1
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Mussini G, Smith MP, Vinther J, Rahman IA, Murdock DJE, Harper DAT, Dunn FS. A new interpretation of Pikaia reveals the origins of the chordate body plan. Curr Biol 2024; 34:2980-2989.e2. [PMID: 38866005 DOI: 10.1016/j.cub.2024.05.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 04/19/2024] [Accepted: 05/14/2024] [Indexed: 06/14/2024]
Abstract
Our understanding of the evolutionary origin of Chordata, one of the most disparate and ecologically significant animal phyla, is hindered by a lack of unambiguous stem-group relatives. Problematic Cambrian fossils that have been considered as candidate chordates include vetulicolians,1Yunnanozoon,2 and the iconic Pikaia.3 However, their phylogenetic placement has remained poorly constrained, impeding reconstructions of character evolution along the chordate stem lineage. Here we reinterpret the morphology of Pikaia, providing evidence for a gut canal and, crucially, a dorsal nerve cord-a robust chordate synapomorphy. The identification of these structures underpins a new anatomical model of Pikaia that shows that this fossil was previously interpreted upside down. We reveal a myomere configuration intermediate between amphioxus and vertebrates and establish morphological links between Yunnanozoon, Pikaia, and uncontroversial chordates. In this light, we perform a new phylogenetic analysis, using a revised, comprehensive deuterostome dataset, and establish a chordate stem lineage. We resolve vetulicolians as a paraphyletic group comprising the earliest diverging stem chordates, subtending a grade of more derived stem-group chordates comprising Yunnanozoon and Pikaia. Our phylogenetic results reveal the stepwise acquisition of characters diagnostic of the chordate crown group. In addition, they chart a phase in early chordate evolution defined by the gradual integration of the pharyngeal region with a segmented axial musculature, supporting classical evolutionary-developmental hypotheses of chordate origins4 and revealing a "lost chapter" in the history of the phylum.
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Affiliation(s)
- Giovanni Mussini
- University of Cambridge, Department of Earth Sciences, Downing Street, Cambridge CB2 3EQ, UK.
| | - M Paul Smith
- Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK
| | - Jakob Vinther
- University of Bristol, School of Earth Sciences, Wills Memorial Building, Bristol BS8 1RL, UK; University of Bristol, School of Biological Sciences, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Imran A Rahman
- Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK; The Natural History Museum, Cromwell Road, South Kensington, London SW7 5BD, UK
| | - Duncan J E Murdock
- Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK
| | - David A T Harper
- Durham University, Department of Earth Sciences, Lower Mountjoy, Durham DH1 3LE, UK
| | - Frances S Dunn
- Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK
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2
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Guarneri I, Bozzo M, Perez Criado N, Serafini E, Manfè G, Tagliapietra D, Fiorin R, Scapin L, Povero P, Bellitto D, Ferrando S, Amaroli A, Castellano L, Pestarino M, Schubert M, Candiani S. Amphioxus (Branchiostoma lanceolatum) in the North Adriatic Sea: ecological observations and spawning behavior. Integr Zool 2024. [PMID: 38886157 DOI: 10.1111/1749-4877.12846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
The European amphioxus (Branchiostoma lanceolatum) is a member of the chordate subphylum Cephalochordata, and, as such, a key model organism for providing insights into the origin and evolution of vertebrates. Despite its significance and global distribution, detailed characterizations of natural populations of cephalochordates are still very limited. This study investigates the abundance, habitat, and spawning behavior of amphioxus in the North Adriatic Sea. Across 32 sampled sites, adult amphioxus were consistently present, reaching densities exceeding 300 individuals m- 2. DNA barcoding confirmed the species as B. lanceolatum, and environmental analyses revealed an amphioxus preference for slightly gravelly sand with low silt content and a correlation between amphioxus density and the presence of specific macroinvertebrate taxa. Remarkably, the amphioxus population was breeding in early spring and possibly late fall, in contrast to the typical late spring/early summer spawning season described for other populations of European amphioxus. Amphioxus adults kept in captivity maintained the spawning seasonality of their place of origin, suggesting the possibility of extending the overall spawning season of European amphioxus in laboratory settings by exploiting populations from diverse geographic origins. This study thus expands our understanding of B. lanceolatum ecology and reproduction in the Mediterranean Sea, emphasizing the role of the North Adriatic Sea as a substantial reservoir.
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Affiliation(s)
- Irene Guarneri
- CNR-ISMAR, Consiglio Nazionale delle Ricerche-Istituto di Scienze Marine, Venice, Italy
| | - Matteo Bozzo
- Dipartimento di Scienze della Terra, dell'Ambiente e della Vita, Università di Genova, Genoa, Italy
| | | | - Emanuele Serafini
- Dipartimento di Scienze della Terra, dell'Ambiente e della Vita, Università di Genova, Genoa, Italy
| | - Giorgia Manfè
- CNR-ISMAR, Consiglio Nazionale delle Ricerche-Istituto di Scienze Marine, Venice, Italy
| | - Davide Tagliapietra
- CNR-ISMAR, Consiglio Nazionale delle Ricerche-Istituto di Scienze Marine, Venice, Italy
| | | | | | - Paolo Povero
- Dipartimento di Scienze della Terra, dell'Ambiente e della Vita, Università di Genova, Genoa, Italy
| | - Deianira Bellitto
- Dipartimento di Scienze della Terra, dell'Ambiente e della Vita, Università di Genova, Genoa, Italy
| | - Sara Ferrando
- Dipartimento di Scienze della Terra, dell'Ambiente e della Vita, Università di Genova, Genoa, Italy
| | - Andrea Amaroli
- Dipartimento di Scienze della Terra, dell'Ambiente e della Vita, Università di Genova, Genoa, Italy
| | | | - Mario Pestarino
- Dipartimento di Scienze della Terra, dell'Ambiente e della Vita, Università di Genova, Genoa, Italy
| | - Michael Schubert
- Laboratoire de Biologie du Développement de Villefranche-sur-Mer, Institut de la Mer de Villefranche, Sorbonne Université, CNRS, Villefranche-sur-Mer, France
| | - Simona Candiani
- Dipartimento di Scienze della Terra, dell'Ambiente e della Vita, Università di Genova, Genoa, Italy
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3
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Sackville MA, Gillis JA, Brauner CJ. The origins of gas exchange and ion regulation in fish gills: evidence from structure and function. J Comp Physiol B 2024:10.1007/s00360-024-01545-5. [PMID: 38530435 DOI: 10.1007/s00360-024-01545-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 01/15/2024] [Accepted: 02/12/2024] [Indexed: 03/28/2024]
Abstract
Gill function in gas exchange and ion regulation has played key roles in the evolution of fishes. In this review, we summarize data from the fields of palaeontology, developmental biology and comparative physiology for when and how the gills first acquired these functions. Data from across disciplines strongly supports a stem vertebrate origin for gas exchange structures and function at the gills with the emergence of larger, more active fishes. However, the recent discovery of putative ionocytes in extant cephalochordates and hemichordates suggests that ion regulation at gills might have originated much earlier than gas exchange, perhaps in the ciliated pharyngeal arches in the last common ancestor of deuterostomes. We hypothesize that the ancestral form of ion regulation served a filter-feeding function in the ciliated pharyngeal arches, and was later coopted in vertebrates to regulate extracellular ion and acid-base balance. We propose that future research should explore ionocyte homology and function across extant deuterostomes to test this hypothesis and others in order to determine the ancestral origins of ion regulation in fish gills.
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Affiliation(s)
| | - J Andrew Gillis
- Bay Paul Centre, Marine Biological Laboratory, Woods Hole, MA, USA
| | - Colin J Brauner
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
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4
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Lacalli T. The Cambrian fossil Pikaia, and the origin of chordate somites. EvoDevo 2024; 15:1. [PMID: 38302988 PMCID: PMC10832150 DOI: 10.1186/s13227-024-00222-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 01/17/2024] [Indexed: 02/03/2024] Open
Abstract
The Middle Cambrian fossil Pikaia has a regular series of vertical bands that, assuming chordate affinities, can be interpreted as septa positioned between serial myotomes. Whether Pikaia has a notochord and nerve cord is less certain, as the dorsal organ, which has no obvious counterpart in living chordates, is the only clearly defined axial structure extending the length of the body. Without a notochord to serve as a reference point, the location of the nerve cord is then conjectural, which begs the question of how a dorsal neural center devoted to somite innervation would first have arisen from a more diffuse ancestral plexus of intraepithelial nerves. This question is examined using hemichordates as a reference point, first for the information they provide on the organization of the ancestral deuterostome nervous system, and second, extending the analysis of E. E. Ruppert, to explain why neural infoldings like the enteropneust collar cord would first have evolved. Both implicate the medial surface of the anterior-most part of the metacoel as the likely site for the evolution of the first somites. The analysis highlights the importance of the somatobranchial condition in chordates, meaning the linkage between the anterior trunk, hox1 expression, and the beginning of the gill series and somites. This feature is arguably a valid criterion by which to assess extinct taxa from the Cambrian that resemble chordates (e.g., vetulicolians and yunnanozoans), but may be unrelated to them. In a more speculative vein, the nature of the dorsal organ is discussed, including the possibility that it is an expanded neural tube combining neural and support functions in one structure.
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Affiliation(s)
- Thurston Lacalli
- Biology Department, University of Victoria, Victoria, V8W-3N5, Canada.
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D'Aniello S, Bertrand S, Escriva H. Amphioxus as a model to study the evolution of development in chordates. eLife 2023; 12:e87028. [PMID: 37721204 PMCID: PMC10506793 DOI: 10.7554/elife.87028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 08/10/2023] [Indexed: 09/19/2023] Open
Abstract
Cephalochordates and tunicates represent the only two groups of invertebrate chordates, and extant cephalochordates - commonly known as amphioxus or lancelets - are considered the best proxy for the chordate ancestor, from which they split around 520 million years ago. Amphioxus has been an important organism in the fields of zoology and embryology since the 18th century, and the morphological and genomic simplicity of cephalochordates (compared to vertebrates) makes amphioxus an attractive model for studying chordate biology at the cellular and molecular levels. Here we describe the life cycle of amphioxus, and discuss the natural histories and habitats of the different species of amphioxus. We also describe their use as laboratory animal models, and discuss the techniques that have been developed to study different aspects of amphioxus.
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Affiliation(s)
- Salvatore D'Aniello
- Biology and Evolution of Marine Organisms (BEOM), Stazione Zoologica Anton DohrnNapoliItaly
| | - Stephanie Bertrand
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire OcéanologiqueBanyuls-sur-MerFrance
| | - Hector Escriva
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire OcéanologiqueBanyuls-sur-MerFrance
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6
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Nanglu K, Lerosey-Aubril R, Weaver JC, Ortega-Hernández J. A mid-Cambrian tunicate and the deep origin of the ascidiacean body plan. Nat Commun 2023; 14:3832. [PMID: 37414759 PMCID: PMC10325964 DOI: 10.1038/s41467-023-39012-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 05/25/2023] [Indexed: 07/08/2023] Open
Abstract
Tunicates are an evolutionarily significant subphylum of marine chordates, with their phylogenetic position as the sister-group to Vertebrata making them key to unraveling our own deep time origin. Tunicates greatly vary with regards to morphology, ecology, and life cycle, but little is known about the early evolution of the group, e.g. whether their last common ancestor lived freely in the water column or attached to the seafloor. Additionally, tunicates have a poor fossil record, which includes only one taxon with preserved soft-tissues. Here we describe Megasiphon thylakos nov., a 500-million-year-old tunicate from the Marjum Formation of Utah, which features a barrel-shaped body with two long siphons and prominent longitudinal muscles. The ascidiacean-like body of this new species suggests two alternative hypotheses for early tunicate evolution. The most likely scenario posits M. thylakos belongs to stem-group Tunicata, suggesting that a biphasic life cycle, with a planktonic larva and a sessile epibenthic adult, is ancestral for this entire subphylum. Alternatively, a position within the crown-group indicates that the divergence between appendicularians and all other tunicates occurred 50 million years earlier than currently estimated based on molecular clocks. Ultimately, M. thylakos demonstrates that fundamental components of the modern tunicate body plan were already established shortly after the Cambrian Explosion.
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Affiliation(s)
- Karma Nanglu
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
| | - Rudy Lerosey-Aubril
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
| | - James C Weaver
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA, 02138, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
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7
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Li Y, Dunn FS, Murdock DJE, Guo J, Rahman IA, Cong P. Cambrian stem-group ambulacrarians and the nature of the ancestral deuterostome. Curr Biol 2023:S0960-9822(23)00530-4. [PMID: 37167976 DOI: 10.1016/j.cub.2023.04.048] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 02/17/2023] [Accepted: 04/19/2023] [Indexed: 05/13/2023]
Abstract
Deuterostomes are characterized by some of the most widely divergent body plans in the animal kingdom. These striking morphological differences have hindered efforts to predict ancestral characters, with the origin and earliest evolution of the group remaining ambiguous. Several iconic Cambrian fossils have been suggested to be early deuterostomes and hence could help elucidate ancestral character states. However, their phylogenetic relationships are controversial. Here, we describe new, exceptionally preserved specimens of the discoidal metazoan Rotadiscus grandis from the early Cambrian Chengjiang biota of China. These reveal a previously unknown double spiral structure, which we interpret as a chordate-like covering to a coelomopore, located adjacent to a horseshoe-shaped tentacle complex. The tentacles differ in key aspects from those seen in lophophorates and are instead more similar to the tentacular systems of extant pterobranchs and echinoderms. Thus, Rotadiscus exhibits a chimeric combination of ambulacrarian and chordate characters. Phylogenetic analyses recover Rotadiscus and closely related fossil taxa as stem ambulacrarians, filling a significant morphological gap in the deuterostome tree of life. These results allow us to reconstruct the ancestral body plans of major clades of deuterostomes, revealing that key traits of extant forms, such as a post-anal region, gill bars, and a U-shaped gut, evolved through convergence.
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Affiliation(s)
- Yujing Li
- Yunnan Normal University, Kunming 650500, China; Yunnan Key Laboratory for Palaeobiology & MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming 650500, China; State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Frances S Dunn
- Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK
| | - Duncan J E Murdock
- Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK
| | - Jin Guo
- Yunnan Key Laboratory for Palaeobiology & MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming 650500, China; Management Committee of the Chengjiang Fossil Site World Heritage, Chengjiang 652599, China
| | - Imran A Rahman
- Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK; The Natural History Museum, London SW7 5BD, UK.
| | - Peiyun Cong
- Yunnan Key Laboratory for Palaeobiology & MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming 650500, China.
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8
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Osawa H, Caron JB, Gaines RR. First record of growth patterns in a Cambrian annelid. ROYAL SOCIETY OPEN SCIENCE 2023; 10:221400. [PMID: 37122950 PMCID: PMC10130728 DOI: 10.1098/rsos.221400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Accepted: 04/03/2023] [Indexed: 05/03/2023]
Abstract
Early annelid evolution is mostly known from 13 described species from Cambrian Burgess Shale-type Lagerstätten. We introduce a new exceptionally well-preserved polychaete, Ursactis comosa gen. et sp. nov., from the Burgess Shale (Wuliuan Stage). This small species (3-15 mm) is the most abundant Cambrian polychaete known to date. Most specimens come from Tokumm Creek, a new Burgess Shale locality in northern Kootenay National Park, British Columbia, Canada. Ursactis has a pair of large palps, thin peristomial neurochaetae and biramous parapodia bearing similarly sized capillary neurochaetae and notochaetae, except for segments six to nine, which also have longer notochaetae. The number of segments in this polychaete range between 8 and 10 with larger individuals having 10 segments. This number of segments in Ursactis is remarkably small compared with other polychaetes, including modern forms. Specimens with 10 segments show significant size variations, and the length of each segment increases with the body length, indicating that body growth was primarily achieved by increasing the size of existing segments rather than adding new ones. This contrasts with most modern polychaetes, which typically have a larger number of segments through additions of segments throughout life. The inferred growth pattern in Ursactis suggests that annelids had evolved control over segment addition by the mid-Cambrian.
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Affiliation(s)
- Hatena Osawa
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2
- Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, Canada M5S 2C6
| | - Jean-Bernard Caron
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2
- Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, Canada M5S 2C6
- Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, Ontario, Canada M5S 3B1
| | - Robert R. Gaines
- Geology Department, Pomona College, 185 E Sixth Street, Claremont, CA 91711, USA
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9
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Evans RG. Evolution of the glomerulus in a marine environment and its implications for renal function in terrestrial vertebrates. Am J Physiol Regul Integr Comp Physiol 2023; 324:R143-R151. [PMID: 36534585 DOI: 10.1152/ajpregu.00210.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Nearly a century ago, Homer Smith proposed that the glomerulus evolved to meet the challenge of excretion of water in freshwater vertebrates. This hypothesis has been repeatedly restated in the nephrology and renal physiology literature, even though we now know that vertebrates evolved and diversified in marine (saltwater) environments. A more likely explanation is that the vertebrate glomerulus evolved from the meta-nephridium of marine invertebrates, with the driving force for ultrafiltration being facilitated by the apposition of the filtration barrier to the vasculature (in vertebrates) rather than the coelom (in invertebrates) and the development of a true heart and the more complex vertebrate vascular system. In turn, glomerular filtration aided individual regulation of divalent ions like magnesium, calcium, and sulfate compatible with the function of cardiac and skeletal muscle required for mobile predators. The metabolic cost, imposed by reabsorption of the small amounts of sodium required to drive secretion of these over-abundant divalent ions, was small. This innovation, developed in a salt-water environment, provided a preadaptation for life in freshwater, in which the glomerulus was co-opted to facilitate water excretion, albeit with the additional metabolic demand imposed by the need to reabsorb the majority of filtered sodium. The evolution of the glomerulus in saltwater also provided preadaptation for terrestrial life, where the imperative is conservation of both water and electrolytes. The historical contingencies of this scenario may explain why the mammalian kidney is so metabolically inefficient, with ∼80% of oxygen consumption being used to drive reabsorption of filtered sodium.
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Affiliation(s)
- Roger G Evans
- Cardiovascular Disease Program, Biomedicine Discovery Institute, and Department of Physiology, Monash University, Melbourne, Victoria, Australia.,Preclinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia
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10
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Nanglu K, Cole SR, Wright DF, Souto C. Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development. Biol Rev Camb Philos Soc 2023; 98:316-351. [PMID: 36257784 DOI: 10.1111/brv.12908] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 09/23/2022] [Accepted: 09/28/2022] [Indexed: 01/12/2023]
Abstract
Deuterostomes are the major division of animal life which includes sea stars, acorn worms, and humans, among a wide variety of ecologically and morphologically disparate taxa. However, their early evolution is poorly understood, due in part to their disparity, which makes identifying commonalities difficult, as well as their relatively poor early fossil record. Here, we review the available morphological, palaeontological, developmental, and molecular data to establish a framework for exploring the origins of this important and enigmatic group. Recent fossil discoveries strongly support a vermiform ancestor to the group Hemichordata, and a fusiform active swimmer as ancestor to Chordata. The diverse and anatomically bewildering variety of forms among the early echinoderms show evidence of both bilateral and radial symmetry. We consider four characteristics most critical for understanding the form and function of the last common ancestor to Deuterostomia: Hox gene expression patterns, larval morphology, the capacity for biomineralization, and the morphology of the pharyngeal region. We posit a deuterostome last common ancestor with a similar antero-posterior gene regulatory system to that found in modern acorn worms and cephalochordates, a simple planktonic larval form, which was later elaborated in the ambulacrarian lineage, the ability to secrete calcium minerals in a limited fashion, and a pharyngeal respiratory region composed of simple pores. This animal was likely to be motile in adult form, as opposed to the sessile origins that have been historically suggested. Recent debates regarding deuterostome monophyly as well as the wide array of deuterostome-affiliated problematica further suggest the possibility that those features were not only present in the last common ancestor of Deuterostomia, but potentially in the ur-bilaterian. The morphology and development of the early deuterostomes, therefore, underpin some of the most significant questions in the study of metazoan evolution.
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Affiliation(s)
- Karma Nanglu
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Selina R Cole
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, 10th & Constitution Avenue NW, Washington, DC, 20560, USA.,Sam Noble Museum, University of Oklahoma, 2401 Chautauqua Avenue, Norman, OK, 73072, USA.,School of Geosciences, University of Oklahoma, 100 E Boyd Street, Norman, OK, 73019, USA
| | - David F Wright
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, 10th & Constitution Avenue NW, Washington, DC, 20560, USA.,Sam Noble Museum, University of Oklahoma, 2401 Chautauqua Avenue, Norman, OK, 73072, USA.,School of Geosciences, University of Oklahoma, 100 E Boyd Street, Norman, OK, 73019, USA
| | - Camilla Souto
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, 10th & Constitution Avenue NW, Washington, DC, 20560, USA.,School of Natural Sciences & Mathematics, Stockton University, 101 Vera King Farris Dr, Galloway, NJ, 08205, USA
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11
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Tian Q, Zhao F, Zeng H, Zhu M, Jiang B. Ultrastructure reveals ancestral vertebrate pharyngeal skeleton in yunnanozoans. Science 2022; 377:218-222. [DOI: 10.1126/science.abm2708] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Pharyngeal arches are a key innovation that likely contributed to the evolution of the jaws and braincase of vertebrates. It has long been hypothesized that the pharyngeal (branchial) arch evolved from an unjointed cartilaginous rod in vertebrate ancestors such as that in the nonvertebrate chordate amphioxus, but whether such ancestral anatomy existed remains unknown. The pharyngeal skeleton of controversial Cambrian animals called yunnanozoans may contain the oldest fossil evidence constraining the early evolution of the arches, yet its correlation with that of vertebrates is still disputed. By examining additional specimens in previously unexplored techniques (for example, x-ray microtomography, scanning and transmission electron microscopy, and energy dispersive spectrometry element mapping), we found evidence that yunnanozoan branchial arches consist of cellular cartilage with an extracellular matrix dominated by microfibrils, a feature hitherto considered specific to vertebrates. Our phylogenetic analysis provides further support that yunnanozoans are stem vertebrates.
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Affiliation(s)
- Qingyi Tian
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing 210023, China
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing 210008, China
| | - Fangchen Zhao
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing 210008, China
| | - Han Zeng
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing 210008, China
| | - Maoyan Zhu
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing 210008, China
- College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Baoyu Jiang
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing 210023, China
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12
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Ferran JL, Irimia M, Puelles L. Is There a Prechordal Region and an Acroterminal Domain in Amphioxus? BRAIN, BEHAVIOR AND EVOLUTION 2022; 96:334-352. [PMID: 35034027 DOI: 10.1159/000521966] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 01/03/2022] [Indexed: 12/16/2022]
Abstract
This essay re-examines the singular case of the supposedly unique rostrally elongated notochord described classically in amphioxus. We start from our previous observations in hpf 21 larvae [Albuixech-Crespo et al.: PLoS Biol. 2017;15(4):e2001573] indicating that the brain vesicle has rostrally a rather standard hypothalamic molecular configuration. This correlates with the notochord across a possible rostromedian acroterminal hypothalamic domain. The notochord shows some molecular differences that specifically characterize its pre-acroterminal extension beyond its normal rostral end under the mamillary region. We explored an alternative interpretation that the putative extension of this notochord actually represents a variant form of the prechordal plate in amphioxus, some of whose cells would adopt the notochordal typology, but would lack notochordal patterning properties, and might have some (but not all) prechordal ones instead. We survey in detail the classic and recent literature on gastrulation, prechordal plate, and notochord formation in amphioxus, compare the observed patterns with those of some other vertebrates of interest, and re-examine the literature on differential gene expression patterns in this rostralmost area of the head. We noted that previous literature failed to identify the amphioxus prechordal primordia at appropriate stages. Under this interpretation, a consistent picture can be drawn for cephalochordates, tunicates, and vertebrates. Moreover, there is little evidence for an intrinsic capacity of the early notochord to grow rostralwards (it normally elongates caudalwards). Altogether, we conclude that the hypothesis of a prechordal nature of the elongated amphioxus notochord is consistent with the evidence presented.
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Affiliation(s)
- José Luis Ferran
- Department of Human Anatomy and Psychobiology, Faculty of Medicine, University of Murcia, Murcia, Spain.,Institute of Biomedical Research of Murcia - IMIB, Virgen de la Arrixaca University Hospital, Murcia, Spain
| | - Manuel Irimia
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain.,ICREA, Barcelona, Spain
| | - Luis Puelles
- Department of Human Anatomy and Psychobiology, Faculty of Medicine, University of Murcia, Murcia, Spain.,Institute of Biomedical Research of Murcia - IMIB, Virgen de la Arrixaca University Hospital, Murcia, Spain
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13
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Meister L, Escriva H, Bertrand S. Functions of the FGF signalling pathway in cephalochordates provide insight into the evolution of the prechordal plate. Development 2022; 149:275365. [PMID: 35575387 PMCID: PMC9188755 DOI: 10.1242/dev.200252] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 04/05/2022] [Indexed: 12/22/2022]
Abstract
The fibroblast growth factor (FGF) signalling pathway plays various roles during vertebrate embryogenesis, from mesoderm formation to brain patterning. This diversity of functions relies on the fact that vertebrates possess the largest FGF gene complement among metazoans. In the cephalochordate amphioxus, which belongs to the chordate clade together with vertebrates and tunicates, we have previously shown that the main role of FGF during early development is the control of rostral somite formation. Inhibition of this signalling pathway induces the loss of these structures, resulting in an embryo without anterior segmented mesoderm, as in the vertebrate head. Here, by combining several approaches, we show that the anterior presumptive paraxial mesoderm cells acquire an anterior axial fate when FGF signal is inhibited and that they are later incorporated in the anterior notochord. Our analysis of notochord formation in wild type and in embryos in which FGF signalling is inhibited also reveals that amphioxus anterior notochord presents transient prechordal plate features. Altogether, our results give insight into how changes in FGF functions during chordate evolution might have participated to the emergence of the complex vertebrate head. Summary: FGF signalling inhibition in cephalochordates induces a loss of anteriormost somites. After FGFR inhibition, the presomitic anterior region cells are incorporated in the anterior notochord which transiently present prechordal plate features.
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Affiliation(s)
- Lydvina Meister
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, F-66650 Banyuls-sur-Mer, France
| | - Hector Escriva
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, F-66650 Banyuls-sur-Mer, France
| | - Stéphanie Bertrand
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, F-66650 Banyuls-sur-Mer, France
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14
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Wang X, Vannier J, Yang X, Leclère L, Ou Q, Song X, Komiya T, Han J. Muscle systems and motility of early animals highlighted by cnidarians from the basal Cambrian. eLife 2022; 11:74716. [PMID: 35098925 PMCID: PMC8837203 DOI: 10.7554/elife.74716] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 01/11/2022] [Indexed: 12/02/2022] Open
Abstract
Although fossil evidence suggests that various animal groups were able to move actively through their environment in the early stages of their evolution, virtually no direct information is available on the nature of their muscle systems. The origin of jellyfish swimming, for example, is of great interest to biologists. Exceptionally preserved muscles are described here in benthic peridermal olivooid medusozoans from the basal Cambrian of China (Kuanchuanpu Formation, ca. 535 Ma) that have direct equivalent in modern medusozoans. They consist of circular fibers distributed over the bell surface (subumbrella) and most probably have a myoepithelial origin. This is the oldest record of a muscle system in cnidarians and more generally in animals. This basic system was probably co-opted by early Cambrian jellyfish to develop capacities for jet-propelled swimming within the water column. Additional lines of fossil evidence obtained from ecdysozoans (worms and panarthropods) show that the muscle systems of early animals underwent a rapid diversification through the early Cambrian and increased their capacity to colonize a wide range of habitats both within the water column and sediment at a critical time of their evolutionary radiation.
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Affiliation(s)
- Xing Wang
- China Geological Survey, Qingdao Institute of Marine Geology, Qingdao, China
| | - Jean Vannier
- CNRS UMR 5276, Laboratoire de géologie de Lyon, Claude Bernard University Lyon 1, Lyon, France
| | - Xiaoguang Yang
- Department of Geology, Northwest University, Xi'an, China
| | - Lucas Leclère
- CNRS, Laboratoire de Biologie du Développement, Sorbonne Université, Villefranche-sur-mer, France
| | - Qiang Ou
- Early Life Evolution Laboratory, School of Earth Sciences and Resources, China University of Geosciences, Beijing, China
| | - Xikun Song
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, China
| | - Tsuyoshi Komiya
- Department of Earth Science and Astronomy, University of Tokyo, Tokyo, Japan
| | - Jian Han
- Department of Geology, Northwest University, Xi'an, China
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15
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Rival DE, Yang W, Caron JB. Fish without Tail Fins-Exploring the Function of Tail Morphology of the First Vertebrates. Integr Comp Biol 2021; 61:37-49. [PMID: 33690846 DOI: 10.1093/icb/icab004] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We use a series of hydrodynamic experiments on abstracted models to explore whether primitive vertebrates may have swum under various conditions without a clearly-differentiated tail fin. Cambrian vertebrates had post-anal stubby tails, some had single dorsal and ventral fins, but none had yet evolved a clearly differentiated caudal fin typical of post-Cambrian fishes, and must have relied on their long and flexible laterally-compressed bodies for locomotion, i.e., by bending their bodies side-to-side in order to propagate waves from head to tail. We approach this problem experimentally based on an abstracted model of Metaspriggina walcotti from the 506-million-year old Burgess Shale by using oscillating thin flexible plates while varying the tail fin geometry from rectangular to uniform, and finally to a no tail-fin condition. Despite a missing tail fin, this study supports the observation that the abstracted Metaspriggina model can generate a strong propulsive force in cruise conditions, both away from, and near the sea bed (in ground effect). However, when the abstracted Metaspriggina model moves in ground effect, a weaker performance is observed, indicating that Metaspriggina may not necessarily have been optimized for swimming near the sea bed. When considering acceleration from rest, we find that the Metaspriggina model's performance is not significantly different from other morphological models (abstracted truncate tail and abstracted heterocercal tail). Statistical analysis shows that morphological parameters, swimming modes, and ground effect all play significant roles in thrust performance. While the exact relationships of Cambrian vertebrates are still debated, as agnathans, they share some general characteristics with modern cyclostomes, in particular an elongate body akin to lampreys. Lampreys, as anguilliform swimmers, are considered to be some of the most efficient swimmers using a particular type of suction thrust induced by the traveling body wave as it travels from head to tail. Our current experiments suggest that Metaspriggina's ability in acceleration from rest, through possibly a similar type of suction thrust, which is defined as the ability to generate low pressure on upstream facing sections of the body, might have evolved early in response to increasing predator pressure during the Cambrian Explosion.
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Affiliation(s)
- David E Rival
- Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON K7L 2V9, Canada
| | - Wenchao Yang
- Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON K7L 2V9, Canada
| | - Jean-Bernard Caron
- Department of Natural History, Royal Ontario Museum, Toronto, ON M5S 2C6, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 2J7, Canada
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16
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Siomava N, Fuentes JSM, Diogo R. Deconstructing the long‐standing a priori assumption that serial homology generally involves ancestral similarity followed by anatomical divergence. J Morphol 2020; 281:1110-1132. [DOI: 10.1002/jmor.21236] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 06/18/2020] [Accepted: 07/07/2020] [Indexed: 12/26/2022]
Affiliation(s)
- Natalia Siomava
- Department of Anatomy Howard University College of Medicine Washington District of Columbia USA
| | | | - Rui Diogo
- Department of Anatomy Howard University College of Medicine Washington District of Columbia USA
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17
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Yasuoka Y. Enhancer evolution in chordates: Lessons from functional analyses of cephalochordate cis‐regulatory modules. Dev Growth Differ 2020; 62:279-300. [DOI: 10.1111/dgd.12684] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 05/25/2020] [Accepted: 05/27/2020] [Indexed: 12/20/2022]
Affiliation(s)
- Yuuri Yasuoka
- Laboratory for Comprehensive Genomic Analysis RIKEN Center for Integrative Medical Sciences Tsurumi‐ku Japan
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18
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Di Gregorio A. The notochord gene regulatory network in chordate evolution: Conservation and divergence from Ciona to vertebrates. Curr Top Dev Biol 2020; 139:325-374. [PMID: 32450965 DOI: 10.1016/bs.ctdb.2020.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The notochord is a structure required for support and patterning of all chordate embryos, from sea squirts to humans. An increasing amount of information on notochord development and on the molecular strategies that ensure its proper morphogenesis has been gleaned through studies in the sea squirt Ciona. This invertebrate chordate offers a fortunate combination of experimental advantages, ranging from translucent, fast-developing embryos to a compact genome and impressive biomolecular resources. These assets have enabled the rapid identification of numerous notochord genes and cis-regulatory regions, and provide a rather unique opportunity to reconstruct the gene regulatory network that controls the formation of this developmental and evolutionary chordate landmark. This chapter summarizes the morphogenetic milestones that punctuate notochord formation in Ciona, their molecular effectors, and the current knowledge of the gene regulatory network that ensures the accurate spatial and temporal orchestration of these processes.
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Affiliation(s)
- Anna Di Gregorio
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY, United States.
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19
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Parry L, Caron JB. Canadia spinosa and the early evolution of the annelid nervous system. SCIENCE ADVANCES 2019; 5:eaax5858. [PMID: 31535028 PMCID: PMC6739095 DOI: 10.1126/sciadv.aax5858] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 08/09/2019] [Indexed: 05/19/2023]
Abstract
Annelid worms are a disparate, primitively segmented clade of bilaterians that first appear during the early Cambrian Period. Reconstructing their early evolution is complicated by the extreme morphological diversity in early diverging lineages, rapid diversification, and sparse fossil record. Canadia spinosa, a Burgess Shale fossil polychaete, is redescribed as having palps with feeding grooves, a dorsal median antenna and biramous parapodia associated with the head and flanking a ventral mouth. Carbonaceously preserved features are identified as a terminal brain, circumoral connectives, a midventral ganglionated nerve cord and prominent parapodial nerves. Phylogenetic analysis recovers neuroanatomically simple extant taxa as the sister group of other annelids, but the phylogenetic position of Canadia suggests that the annelid ancestor was reasonably complex neuroanatomically and that reduction of the nervous system occurred several times independently in the subsequent 500 million years of annelid evolution.
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Affiliation(s)
- Luke Parry
- Department of Natural History, Palaeobiology, Royal Ontario Museum, 100 Queen’s Park, Toronto, Ontario M5S 2C6, Canada
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA
- Corresponding author.
| | - Jean-Bernard Caron
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2, Canada
- Department of Earth Sciences, University of Toronto, Toronto, Ontario M5S 3B1, Canada
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20
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Abstract
The same genes and signaling pathways control the formation of limbs in vertebrates, arthropods and cuttlefish.
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Affiliation(s)
- Nikola-Michael Prpic
- Allgemeine Zoologie und Entwicklungsbiologie, Justus-Liebig-Universität Gießen, Gießen, Germany
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21
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Ortega-Hernández J, Janssen R, Budd GE. The last common ancestor of Ecdysozoa had an adult terminal mouth. ARTHROPOD STRUCTURE & DEVELOPMENT 2019; 49:155-158. [PMID: 30458236 DOI: 10.1016/j.asd.2018.11.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 11/09/2018] [Indexed: 06/09/2023]
Abstract
The Ecdysozoa is a major animal clade whose main uniting feature is a distinctive growth strategy that requires the periodical moulting of the external cuticle. The staggering diversity within Ecdysozoa has prompted substantial efforts to reconstruct their origin and early evolution. Based on palaentological and developmental data, we proposed a scenario for the early evolution of the ecdysozoan clade Panarthropoda (Onychophora, Tardigrada, Euarthropoda), and postulated that a terminal mouth is ancestral for this lineage. In light of the accompanying comment by Claus Nielsen, we take this opportunity to clarify the significance of our argumentation for Panarthropoda in the phylogenetic context of Ecdysozoa, and Bilateria more broadly. We conclude that the ancestral ecdysozoan most likely had an adult terminal mouth, and that the last common ancestors of all the phyla that constitute Ecdysozoa almost certainly also had an adult terminal mouth. The occurrence of a ventral-facing mouth in various adult ecdysozoans - particularly panarthropods - is the result of convergence. Despite the paucity of embryological data on fossil taxa, we contemplate the likelihood that a developmentally early ventral mouth opening could be ancestral for Ecdysozoa, and if so, then this would represent a symplesiomorphy of Bilateria as a whole.
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Affiliation(s)
- Javier Ortega-Hernández
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK; Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
| | - Ralf Janssen
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, Uppsala se 752 36, Sweden
| | - Graham E Budd
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, Uppsala se 752 36, Sweden
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22
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Nitric oxide and l-arginine regulate feeding in satiated rats. Appetite 2019; 132:44-54. [DOI: 10.1016/j.appet.2018.09.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 08/14/2018] [Accepted: 09/27/2018] [Indexed: 12/27/2022]
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23
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Vannier J, Aria C, Taylor RS, Caron JB. Waptia fieldensis Walcott, a mandibulate arthropod from the middle Cambrian Burgess Shale. ROYAL SOCIETY OPEN SCIENCE 2018; 5:172206. [PMID: 30110460 PMCID: PMC6030330 DOI: 10.1098/rsos.172206] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 05/04/2018] [Indexed: 05/12/2023]
Abstract
Waptia fieldensis Walcott, 1912 is one of the iconic animals from the middle Cambrian Burgess Shale biota that had lacked a formal description since its discovery at the beginning of the twentieth century. This study, based on over 1800 specimens, finds that W. fieldensis shares general characteristics with pancrustaceans, as previous authors had suggested based mostly on its overall aspect. The cephalothorax is covered by a flexible, bivalved carapace and houses a pair of long multisegmented antennules, palp-bearing mandibles, maxillules, and four pairs of appendages with five-segmented endopods-the anterior three pairs with long and robust enditic basipods, the fourth pair with proximal annulations and lamellae. The post-cephalothorax has six pairs of lamellate and fully annulated appendages which appear to be extensively modified basipods rather than exopods. The front part of the body bears a pair of stalked eyes with the first ommatidia preserved in a Burgess Shale arthropod, and a median 'labral' complex flanked by lobate projections with possible affinities to hemi-ellipsoid bodies. Waptia confirms the mandibulate affinity of hymenocarines, retrieved here as part of an expanded Pancrustacea, thereby providing a novel perspective on the evolutionary history of this hyperdiverse group. We construe that Waptia was an active swimming predator of soft prey items, using its anterior appendages for food capture and manipulation, and also potentially for clinging to epibenthic substrates.
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Affiliation(s)
- Jean Vannier
- Université de Lyon, Université Lyon 1, ENS de Lyon, CNRS, UMR 5276 LGL-TPE, Bâtiment Géode, 2, rue Raphaël Dubois, Villeurbanne 69622, France
| | - Cédric Aria
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39, East Beijing Road, Nanjing 210008, People's Republic of China
- Department of Natural History (Palaeobiology Section), Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, CanadaM5S 2C6
| | - Rod S. Taylor
- Manuels River Hibernia Interpretation Centre, 7 Conception Bay South Highway, CBS, Newfoundland, CanadaA1W 3A2
- Department of Earth Sciences, Memorial University of Newfoundland, St John's, Newfoundland, CanadaA1B 3X5
| | - Jean-Bernard Caron
- Department of Natural History (Palaeobiology Section), Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, CanadaM5S 2C6
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, CanadaM5S 3B2, Toronto, Ontario, CanadaM5S 3B2
- Department of Earth Sciences, University of Toronto, Toronto, Ontario, CanadaM5S 3B1
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24
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Maguire JE, Pandey A, Wu Y, Di Gregorio A. Investigating Evolutionarily Conserved Molecular Mechanisms Controlling Gene Expression in the Notochord. TRANSGENIC ASCIDIANS 2018. [DOI: 10.1007/978-981-10-7545-2_8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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25
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Parry LA, Smithwick F, Nordén KK, Saitta ET, Lozano-Fernandez J, Tanner AR, Caron JB, Edgecombe GD, Briggs DEG, Vinther J. Soft-Bodied Fossils Are Not Simply Rotten Carcasses - Toward a Holistic Understanding of Exceptional Fossil Preservation. Bioessays 2017; 40. [DOI: 10.1002/bies.201700167] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 10/21/2017] [Indexed: 12/31/2022]
Affiliation(s)
- Luke A. Parry
- School of Earth Sciences, University of Bristol, Wills Memorial Building; Queen's Road Bristol BS8 1RJ UK
- Royal Ontario Museum; 100 Queen's Park Toronto ON M5S 2C6 Canada
- Department of Earth Sciences, The Natural History Museum; Cromwell Road London SW7 5BD UK
| | - Fiann Smithwick
- Royal Ontario Museum; 100 Queen's Park Toronto ON M5S 2C6 Canada
| | - Klara K. Nordén
- Royal Ontario Museum; 100 Queen's Park Toronto ON M5S 2C6 Canada
| | - Evan T. Saitta
- Royal Ontario Museum; 100 Queen's Park Toronto ON M5S 2C6 Canada
| | - Jesus Lozano-Fernandez
- School of Biological Sciences, University of Bristol; Life Sciences Building, 24 Tyndall Avenue Bristol BS8 1TQ UK
| | - Alastair R. Tanner
- School of Biological Sciences, University of Bristol; Life Sciences Building, 24 Tyndall Avenue Bristol BS8 1TQ UK
| | - Jean-Bernard Caron
- School of Earth Sciences, University of Bristol, Wills Memorial Building; Queen's Road Bristol BS8 1RJ UK
| | - Gregory D. Edgecombe
- Department of Earth Sciences, The Natural History Museum; Cromwell Road London SW7 5BD UK
| | - Derek E. G. Briggs
- Department of Geology and Geophysics, Yale University; 210 Whitney Avenue New Haven CT 06511 USA
- Yale Peabody Museum of Natural History; 170 Whitney Avenue New Haven CT 06520 USA
- Departments of Ecology and Evolutionary Biology and Earth Sciences, University of Toronto; Toronto ON M5S 3B2 Canada
| | - Jakob Vinther
- School of Earth Sciences, University of Bristol, Wills Memorial Building; Queen's Road Bristol BS8 1RJ UK
- Royal Ontario Museum; 100 Queen's Park Toronto ON M5S 2C6 Canada
- School of Biological Sciences, University of Bristol; Life Sciences Building, 24 Tyndall Avenue Bristol BS8 1TQ UK
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26
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Ou Q, Han J, Zhang Z, Shu D, Sun G, Mayer G. Three Cambrian fossils assembled into an extinct body plan of cnidarian affinity. Proc Natl Acad Sci U S A 2017; 114:8835-8840. [PMID: 28760981 PMCID: PMC5565419 DOI: 10.1073/pnas.1701650114] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The early Cambrian problematica Xianguangia sinica, Chengjiangopenna wangii, and Galeaplumosus abilus from the Chengjiang biota (Yunnan, China) have caused much controversy in the past and their phylogenetic placements remain unresolved. Here we show, based on exceptionally preserved material (85 new specimens plus type material), that specimens previously assigned to these three species are in fact parts of the same organism and propose that C. wangii and G. abilus are junior synonyms of X. sinica Our reconstruction of the complete animal reveals an extinct body plan that combines the characteristics of the three described species and is distinct from all known fossil and living taxa. This animal resembled a cnidarian polyp in overall morphology and having a gastric cavity partitioned by septum-like structures. However, it possessed an additional body cavity within its holdfast, an anchoring pit on the basal disk, and feather-like tentacles with densely ciliated pinnules arranged in an alternating pattern, indicating that it was a suspension feeder rather than a predatory actiniarian. Phylogenetic analyses using Bayesian inference and maximum parsimony suggest that X. sinica is a stem-group cnidarian. This relationship implies that the last common ancestor of X. sinica and crown cnidarians was probably a benthic, polypoid animal with a partitioned gastric cavity and a single mouth/anus opening. This extinct body plan suggests that feeding strategies of stem cnidarians may have been drastically different from that of their crown relatives, which are almost exclusively predators, and reveals that the morphological disparity of total-group Cnidaria is greater than previously assumed.
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Affiliation(s)
- Qiang Ou
- Early Life Evolution Laboratory, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China;
- Department of Zoology, University of Kassel, 34132 Kassel, Germany
| | - Jian Han
- Early Life Institute, Collaborative Innovation Center of Continental Tectonics, State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Zhifei Zhang
- Early Life Institute, Collaborative Innovation Center of Continental Tectonics, State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Degan Shu
- Early Life Evolution Laboratory, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China
- Early Life Institute, Collaborative Innovation Center of Continental Tectonics, State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China
| | - Ge Sun
- Early Life Evolution Laboratory, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China
| | - Georg Mayer
- Department of Zoology, University of Kassel, 34132 Kassel, Germany
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27
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Igawa T, Nozawa M, Suzuki DG, Reimer JD, Morov AR, Wang Y, Henmi Y, Yasui K. Evolutionary history of the extant amphioxus lineage with shallow-branching diversification. Sci Rep 2017; 7:1157. [PMID: 28442709 PMCID: PMC5430900 DOI: 10.1038/s41598-017-00786-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 03/13/2017] [Indexed: 01/20/2023] Open
Abstract
Amphioxus or lancelets have been regarded as a key animal in understanding the origin of vertebrates. However, the evolutionary history within this lineage remains unexplored. As the amphioxus lineage has likely been separated from other chordates for a very long time and displays a marked left-right asymmetry, its evolutionary history is potentially helpful in better understanding chordate and vertebrate origins. We studied the phylogenetic relationships within the extant amphioxus lineage based on mitochondrial genomes incorporating new Asymmetron and Epigonichthys populations, and based on previously reported nuclear transcriptomes. The resulting tree patterns are consistent, showing the Asymmetron clade diverging first, followed by the Epigonichthys and Branchiostoma clades splitting. Divergence time estimates based on nuclear transcriptomes with vertebrate calibrations support a shallow diversification of the extant amphioxus lineage in the Tertiary. These estimates fit well with the closure of seaways between oceans by continental drift, ocean currents, and present geographical distributions, and suggest a long cryptic history from the origin of amphioxus to its most recent diversification. Deduced character polarities based on phylogenetic analyses suggest that the common ancestor of the extant amphioxus existed in a tiny epibenthic state with larva-like appearance of extant amphioxus, likely with ciliate epidermis.
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Affiliation(s)
- Takeshi Igawa
- Amphibian Research Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-hiroshima, Hiroshima, 739-8529, Japan
| | - Masafumi Nozawa
- Department of Biological Sciences, School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minamiosawa, Hachioji, Tokyo, 192-0397, Japan
| | - Daichi G Suzuki
- Department of Biological Sciences, Graduate School of Life and Environmental Sciences, Tsukuba University, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8572, Japan.,Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, SE-171 77, Stockholm, Sweden
| | - James D Reimer
- Department of Biology, Chemistry & Marine Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa, 903-0213, Japan
| | - Arseniy R Morov
- Department of Biological Science, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-hiroshima, Hiroshima, 739-8526, Japan.,Depertment of Zoology and General Biology, Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 18 Kremlyovskaya St., Kazan, 420008, Republic of Tatarstan, Russian Federation
| | - Yiquan Wang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, 361102, China
| | - Yasuhisa Henmi
- Aitsu Marine Station, Center for Marine Environmental Studies, Kumamoto University, 6061 Aitsu, Kami-Amakusa, Kumamoto, 861-6102, Japan
| | - Kinya Yasui
- Department of Biological Science, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-hiroshima, Hiroshima, 739-8526, Japan.
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Caron JB, Aria C. Cambrian suspension-feeding lobopodians and the early radiation of panarthropods. BMC Evol Biol 2017; 17:29. [PMID: 28137244 PMCID: PMC5282736 DOI: 10.1186/s12862-016-0858-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 12/17/2016] [Indexed: 11/19/2022] Open
Abstract
Background Arthropoda, Tardigrada and Onychophora evolved from lobopodians, a paraphyletic group of disparate Palaeozoic vermiform animals with soft legs. Although the morphological diversity that this group encompasses likely illustrates the importance of niche diversification in the early radiation of panarthropods, the ecology of lobopodians remains poorly characterized. Results Here we describe a new luolishaniid taxon from the middle Cambrian Burgess Shale (Walcott Quarry) in British Columbia, Canada, whose specialized morphology epitomizes the suspension-feeding ecology of this clade, and is convergent with some modern marine animals, such as caprellid crustaceans. This species possesses two long pairs and four shorter pairs of elongate spinose lobopods at the front, each bearing two slender claws, and three pairs of stout lobopods bearing single, strong, hook-like anterior-facing claws at the back. The trunk is remarkably bare, widening rearwards, and, at the front, extends beyond the first pair of lobopods into a small “head” bearing a pair of visual organs and a short proboscis with numerous teeth. Based on a critical reappraisal of character coding in lobopodians and using Bayesian and parsimony-based tree searches, two alternative scenarios for early panarthropod evolution are retrieved. In both cases, hallucigeniids and luolishaniids are found to be extinct radiative stem group panarthropods, in contrast to previous analyses supporting a position of hallucigeniids as part of total-group Onychophora. Our Bayesian topology finds luolishaniids and hallucigeniids to form two successive clades at the base of Panarthropoda. Disparity analyses suggest that luolishaniids, hallucigeniids and total-group Onychophora each occupy a distinct region of morphospace. Conclusions Hallucigeniids and luolishaniids were comparably diverse and successful, representing two major lobopodian clades in the early Palaeozoic, and both evolved body plans adapted to different forms of suspension feeding. A Bayesian approach to cladistics supports the view that a semi-sessile, suspension-feeding lifestyle characterized the origin and rise of Panarthropoda from cycloneuralian body plans. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0858-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jean-Bernard Caron
- Department of Natural History (Palaeobiology Section), Royal Ontario Museum, Toronto, Ontario, Canada. .,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada. .,Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada.
| | - Cédric Aria
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
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29
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Preservation and phylogeny of Cambrian ecdysozoans tested by experimental decay of Priapulus. Sci Rep 2016; 6:32817. [PMID: 27595908 PMCID: PMC5011709 DOI: 10.1038/srep32817] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 08/10/2016] [Indexed: 11/22/2022] Open
Abstract
The exceptionally preserved Cambrian fossil record provides unique insight into the early evolutionary history of animals. Understanding of the mechanisms of exceptional soft tissue preservation frames all interpretations of the fauna and its evolutionary significance. This is especially true for recent interpretations of preserved nervous tissues in fossil ecdysozoans. However, models of soft tissue preservation lack empirical support from actualistic studies. Here experimental decay of the priapulid Priapulus reveal consistent bias towards rapid loss of internal non-cuticular anatomy compared with recalcitrant cuticular anatomy. This is consistent with models of Burgess Shale-type preservation and indicates that internal tissues are unlikely to be preserved with fidelity if organically preserved. This pattern, along with extreme body margin distortion, is consistent with onychophoran decay, and is therefore resolved as general for early ecdysozoans. Application of these patterns to phylogenetic data finds scalidophoran taxa to be very sensitive to taphonomically informed character coding, but not panarthropodan taxa. Priapulid decay also have unexpected relevance for interpretation of myomeres in fossil chordates. The decay data presented serve not only as a test of models of preservation but also a framework with which to interpret ecdysozoan fossil anatomies, and the subsequent evolutionary inferences drawn from them.
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30
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Edelman DB, McMenamin M, Sheesley P, Pivar S. Origin of the vertebrate body plan via mechanically biased conservation of regular geometrical patterns in the structure of the blastula. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:212-44. [PMID: 27392530 DOI: 10.1016/j.pbiomolbio.2016.06.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 06/24/2016] [Accepted: 06/28/2016] [Indexed: 01/08/2023]
Abstract
We present a plausible account of the origin of the archetypal vertebrate bauplan. We offer a theoretical reconstruction of the geometrically regular structure of the blastula resulting from the sequential subdivision of the egg, followed by mechanical deformations of the blastula in subsequent stages of gastrulation. We suggest that the formation of the vertebrate bauplan during development, as well as fixation of its variants over the course of evolution, have been constrained and guided by global mechanical biases. Arguably, the role of such biases in directing morphology-though all but neglected in previous accounts of both development and macroevolution-is critical to any substantive explanation for the origin of the archetypal vertebrate bauplan. We surmise that the blastula inherently preserves the underlying geometry of the cuboidal array of eight cells produced by the first three cleavages that ultimately define the medial-lateral, dorsal-ventral, and anterior-posterior axes of the future body plan. Through graphical depictions, we demonstrate the formation of principal structures of the vertebrate body via mechanical deformation of predictable geometrical patterns during gastrulation. The descriptive rigor of our model is supported through comparisons with previous characterizations of the embryonic and adult vertebrate bauplane. Though speculative, the model addresses the poignant absence in the literature of any plausible account of the origin of vertebrate morphology. A robust solution to the problem of morphogenesis-currently an elusive goal-will only emerge from consideration of both top-down (e.g., the mechanical constraints and geometric properties considered here) and bottom-up (e.g., molecular and mechano-chemical) influences.
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Affiliation(s)
- David B Edelman
- Department of Psychological Sciences, University of San Diego, Serra Hall 158, 5998 Alcalá Park, San Diego, CA 92110, USA.
| | - Mark McMenamin
- 303 Clapp Laboratory, Mount Holyoke College, 50 College Street, South Hadley, MA 01075, USA.
| | - Peter Sheesley
- Evergreen State College, 2700 Evergreen Pkwy NW, Olympia, WA 98505, USA.
| | - Stuart Pivar
- Chief Scientific Officer and Chairman, Chem-Tainer Industries, Inc., 361Neptune Avenue, West Babylon, NY 11704, USA.
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31
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The phylogeny, evolutionary developmental biology, and paleobiology of the Deuterostomia: 25 years of new techniques, new discoveries, and new ideas. ORG DIVERS EVOL 2016. [DOI: 10.1007/s13127-016-0270-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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32
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New Insights in the Ontogeny and Taphonomy of the Devonian Acanthodian Triazeugacanthus affinis From the Miguasha Fossil-Lagerstätte, Eastern Canada. MINERALS 2015. [DOI: 10.3390/min6010001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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33
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Bertrand S, Aldea D, Oulion S, Subirana L, de Lera AR, Somorjai I, Escriva H. Evolution of the Role of RA and FGF Signals in the Control of Somitogenesis in Chordates. PLoS One 2015; 10:e0136587. [PMID: 26371756 PMCID: PMC4570818 DOI: 10.1371/journal.pone.0136587] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 08/05/2015] [Indexed: 11/18/2022] Open
Abstract
During vertebrate development, the paraxial mesoderm becomes segmented, forming somites that will give rise to dermis, axial skeleton and skeletal muscles. Although recently challenged, the "clock and wavefront" model for somitogenesis explains how interactions between several cell-cell communication pathways, including the FGF, RA, Wnt and Notch signals, control the formation of these bilateral symmetric blocks. In the cephalochordate amphioxus, which belongs to the chordate phylum together with tunicates and vertebrates, the dorsal paraxial mesendoderm also periodically forms somites, although this process is asymmetric and extends along the whole body. It has been previously shown that the formation of the most anterior somites in amphioxus is dependent upon FGF signalling. However, the signals controlling somitogenesis during posterior elongation in amphioxus are still unknown. Here we show that, contrary to vertebrates, RA and FGF signals act independently during posterior elongation and that they are not mandatory for posterior somites to form. Moreover, we show that RA is not able to buffer the left/right asymmetry machinery that is controlled through the asymmetric expression of Nodal pathway actors. Our results give new insights into the evolution of the somitogenesis process in chordates. They suggest that RA and FGF pathways have acquired specific functions in the control of somitogenesis in vertebrates. We propose that the "clock and wavefront" system was selected specifically in vertebrates in parallel to the development of more complex somite-derived structures but that it was not required for somitogenesis in the ancestor of chordates.
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Affiliation(s)
- Stéphanie Bertrand
- UPMC Univ Paris 06, UMR 7232, BIOM, Observatoire Océanologique de Banyuls sur Mer, F-66650, Banyuls/Mer, France
- * E-mail: (SB); (HE)
| | - Daniel Aldea
- UPMC Univ Paris 06, UMR 7232, BIOM, Observatoire Océanologique de Banyuls sur Mer, F-66650, Banyuls/Mer, France
| | - Silvan Oulion
- UPMC Univ Paris 06, UMR 7232, BIOM, Observatoire Océanologique de Banyuls sur Mer, F-66650, Banyuls/Mer, France
| | - Lucie Subirana
- UPMC Univ Paris 06, UMR 7232, BIOM, Observatoire Océanologique de Banyuls sur Mer, F-66650, Banyuls/Mer, France
| | - Angel R. de Lera
- Departamento de Química Orgánica, Facultade de Química, CINBIO, Universidade de Vigo, and Instituto de Investigación Biomédica de Vigo (IBIV), Vigo, Spain
| | - Ildiko Somorjai
- UPMC Univ Paris 06, UMR 7232, BIOM, Observatoire Océanologique de Banyuls sur Mer, F-66650, Banyuls/Mer, France
| | - Hector Escriva
- UPMC Univ Paris 06, UMR 7232, BIOM, Observatoire Océanologique de Banyuls sur Mer, F-66650, Banyuls/Mer, France
- * E-mail: (SB); (HE)
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34
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Fleming A, Kishida MG, Kimmel CB, Keynes RJ. Building the backbone: the development and evolution of vertebral patterning. Development 2015; 142:1733-44. [PMID: 25968309 DOI: 10.1242/dev.118950] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The segmented vertebral column comprises a repeat series of vertebrae, each consisting of two key components: the vertebral body (or centrum) and the vertebral arches. Despite being a defining feature of the vertebrates, much remains to be understood about vertebral development and evolution. Particular controversy surrounds whether vertebral component structures are homologous across vertebrates, how somite and vertebral patterning are connected, and the developmental origin of vertebral bone-mineralizing cells. Here, we assemble evidence from ichthyologists, palaeontologists and developmental biologists to consider these issues. Vertebral arch elements were present in early stem vertebrates, whereas centra arose later. We argue that centra are homologous among jawed vertebrates, and review evidence in teleosts that the notochord plays an instructive role in segmental patterning, alongside the somites, and contributes to mineralization. By clarifying the evolutionary relationship between centra and arches, and their varying modes of skeletal mineralization, we can better appreciate the detailed mechanisms that regulate and diversify vertebral patterning.
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Affiliation(s)
- Angeleen Fleming
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK Department of Medical Genetics, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
| | - Marcia G Kishida
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
| | - Charles B Kimmel
- Institute of Neuroscience, 1254 University of Oregon, Eugene OR 97403-1254, USA
| | - Roger J Keynes
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
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35
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Smith MR, Caron JB. Hallucigenia's head and the pharyngeal armature of early ecdysozoans. Nature 2015; 523:75-8. [PMID: 26106857 DOI: 10.1038/nature14573] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 05/18/2015] [Indexed: 11/09/2022]
Abstract
The molecularly defined clade Ecdysozoa comprises the panarthropods (Euarthropoda, Onychophora and Tardigrada) and the cycloneuralian worms (Nematoda, Nematomorpha, Priapulida, Loricifera and Kinorhyncha). These disparate phyla are united by their means of moulting, but otherwise share few morphological characters--none of which has a meaningful fossilization potential. As such, the early evolutionary history of the group as a whole is largely uncharted. Here we redescribe the 508-million-year-old stem-group onychophoran Hallucigenia sparsa from the mid-Cambrian Burgess Shale. We document an elongate head with a pair of simple eyes, a terminal buccal chamber containing a radial array of sclerotized elements, and a differentiated foregut that is lined with acicular teeth. The radial elements and pharyngeal teeth resemble the sclerotized circumoral elements and pharyngeal teeth expressed in tardigrades, stem-group euarthropods and cycloneuralian worms. Phylogenetic results indicate that equivalent structures characterized the ancestral panarthropod and, seemingly, the ancestral ecdysozoan, demonstrating the deep homology of panarthropod and cycloneuralian mouthparts, and providing an anatomical synapomorphy for the ecdysozoan supergroup.
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Affiliation(s)
- Martin R Smith
- Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
| | - Jean-Bernard Caron
- 1] Department of Natural History (Palaeobiology Section), Royal Ontario Museum, Toronto, Ontario M5S 2C6, Canada [2] Departments of Ecology and Evolutionary Biology and Earth Sciences, University of Toronto, Toronto, Ontario M5S 3B2, Canada
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36
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Aria C, Caron JB. Cephalic and limb anatomy of a new Isoxyid from the Burgess Shale and the role of "stem bivalved arthropods" in the disparity of the frontalmost appendage. PLoS One 2015; 10:e0124979. [PMID: 26038846 PMCID: PMC4454494 DOI: 10.1371/journal.pone.0124979] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Accepted: 03/19/2015] [Indexed: 12/21/2022] Open
Abstract
We herein describe Surusicaris elegans gen. et sp. nov. (in Isoxyidae, amended), a middle (Series 3, Stage 5) Cambrian bivalved arthropod from the new Burgess Shale deposit of Marble Canyon (Kootenay National Park, British Columbia). Surusicaris exhibits 12 simple, partly undivided biramous trunk limbs with long tripartite caeca, which may illustrate a plesiomorphic "fused" condition of exopod and endopod. We construe also that the head is made of five somites (= four segments), including two eyes, one pair of anomalocaridid-like frontalmost appendages, and three pairs of poorly sclerotized uniramous limbs. This fossil may therefore be a candidate for illustrating the origin of the plesiomorphic head condition in euarthropods, and questions the significance of the "two-segmented head" in, e.g., fuxianhuiids. The frontalmost appendage in isoxyids is intriguingly disparate, bearing similarities with both dinocaridids and euarthropods. In order to evaluate the relative importance of bivalved arthropods, such as Surusicaris, in the hypothetical structuro-functional transition between the dinocaridid frontal appendage and the pre-oral-arguably deutocerebral-appendage of euarthropods, we chose a phenetic approach and computed morphospace occupancy for the frontalmost appendages of 36 stem and crown taxa. Results show different levels of evolutionary decoupling between frontalmost appendage disparity and body plans. Variance is greatest in dinocaridids and "stem bivalved" arthropods, but these groups do not occupy the morphospace homogeneously. Rather, the diversity of frontalmost appendages in "stem bivalved" arthropods, distinct in its absence of clear clustering, is found to link the morphologies of "short great appendages," chelicerae and antennules. This find fits the hypothesis of an increase in disparity of the deutocerebral appendage prior to its diversification in euarthropods, and possibly corresponds to its original time of development. The analysis of this pattern, however, is sensitive to the-still unclear-extent of polyphyly of the "stem bivalved" taxa.
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Affiliation(s)
- Cédric Aria
- University of Toronto, Department of Ecology and Evolutionary Biology, 25 Willcocks Street, Toronto, Ontario, M5S 3B2, Canada
- Royal Ontario Museum, Department of Natural History-Palaeobiology, 100 Queen’s Park, Toronto, Ontario, M5S 2C6, Canada
| | - Jean-Bernard Caron
- University of Toronto, Department of Ecology and Evolutionary Biology, 25 Willcocks Street, Toronto, Ontario, M5S 3B2, Canada
- Royal Ontario Museum, Department of Natural History-Palaeobiology, 100 Queen’s Park, Toronto, Ontario, M5S 2C6, Canada
- University of Toronto, Department of Earth Sciences, 22 Russell Street, Toronto, Ontario, M5S 3B1, Canada
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37
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Facts and fancies about early fossil chordates and vertebrates. Nature 2015; 520:483-9. [PMID: 25903630 DOI: 10.1038/nature14437] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 03/20/2015] [Indexed: 02/01/2023]
Abstract
The interrelationships between major living vertebrate, and even chordate, groups are now reasonably well resolved thanks to a large amount of generally congruent data derived from molecular sequences, anatomy and physiology. But fossils provide unexpected combinations of characters that help us to understand how the anatomy of modern groups was progressively shaped over millions of years. The dawn of vertebrates is documented by fossils that are preserved as either soft-tissue imprints, or minute skeletal fragments, and it is sometimes difficult for palaeontologists to tell which of them are reliable vertebrate remains and which merely reflect our idea of an ancestral vertebrate.
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38
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Sansom RS. Bias and sensitivity in the placement of fossil taxa resulting from interpretations of missing data. Syst Biol 2015; 64:256-66. [PMID: 25432893 PMCID: PMC4380037 DOI: 10.1093/sysbio/syu093] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 11/20/2014] [Indexed: 11/14/2022] Open
Abstract
The utility of fossils in evolutionary contexts is dependent on their accurate placement in phylogenetic frameworks, yet intrinsic and widespread missing data make this problematic. The complex taphonomic processes occurring during fossilization can make it difficult to distinguish absence from non-preservation, especially in the case of exceptionally preserved soft-tissue fossils: is a particular morphological character (e.g., appendage, tentacle, or nerve) missing from a fossil because it was never there (phylogenetic absence), or just happened to not be preserved (taphonomic loss)? Missing data have not been tested in the context of interpretation of non-present anatomy nor in the context of directional shifts and biases in affinity. Here, complete taxa, both simulated and empirical, are subjected to data loss through the replacement of present entries (1s) with either missing (?s) or absent (0s) entries. Both cause taxa to drift down trees, from their original position, toward the root. Absolute thresholds at which downshift is significant are extremely low for introduced absences (two entries replaced, 6% of present characters). The opposite threshold in empirical fossil taxa is also found to be low; two absent entries replaced with presences causes fossil taxa to drift up trees. As such, only a few instances of non-preserved characters interpreted as absences will cause fossil organisms to be erroneously interpreted as more primitive than they were in life. This observed sensitivity to coding non-present morphology presents a problem for all evolutionary studies that attempt to use fossils to reconstruct rates of evolution or unlock sequences of morphological change. Stem-ward slippage, whereby fossilization processes cause organisms to appear artificially primitive, appears to be a ubiquitous and problematic phenomenon inherent to missing data, even when no decay biases exist. Absent characters therefore require explicit justification and taphonomic frameworks to support their interpretation.
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Affiliation(s)
- Robert S Sansom
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
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39
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Rost F, Eugster C, Schröter C, Oates AC, Brusch L. Chevron formation of the zebrafish muscle segments. J Exp Biol 2014; 217:3870-82. [PMID: 25267843 PMCID: PMC4213178 DOI: 10.1242/jeb.102202] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 09/04/2014] [Indexed: 01/16/2023]
Abstract
The muscle segments of fish have a folded shape, termed a chevron, which is thought to be optimal for the undulating body movements of swimming. However, the mechanism shaping the chevron during embryogenesis is not understood. Here, we used time-lapse microscopy of developing zebrafish embryos spanning the entire somitogenesis period to quantify the dynamics of chevron shape development. By comparing such time courses with the start of movements in wildtype zebrafish and analysing immobile mutants, we show that the previously implicated body movements do not play a role in chevron formation. Further, the monotonic increase of chevron angle along the anteroposterior axis revealed by our data constrains or rules out possible contributions by previously proposed mechanisms. In particular, we found that muscle pioneers are not required for chevron formation. We put forward a tension-and-resistance mechanism involving interactions between intra-segmental tension and segment boundaries. To evaluate this mechanism, we derived and analysed a mechanical model of a chain of contractile and resisting elements. The predictions of this model were verified by comparison with experimental data. Altogether, our results support the notion that a simple physical mechanism suffices to self-organize the observed spatiotemporal pattern in chevron formation.
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Affiliation(s)
- Fabian Rost
- Center for Information Services and High-Performance Computing, Technische Universität Dresden, 01062 Dresden, Germany
| | - Christina Eugster
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Christian Schröter
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Andrew C Oates
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany MRC-National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Lutz Brusch
- Center for Information Services and High-Performance Computing, Technische Universität Dresden, 01062 Dresden, Germany
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40
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García-Bellido DC, Lee MSY, Edgecombe GD, Jago JB, Gehling JG, Paterson JR. A new vetulicolian from Australia and its bearing on the chordate affinities of an enigmatic Cambrian group. BMC Evol Biol 2014; 14:214. [PMID: 25273382 PMCID: PMC4203957 DOI: 10.1186/s12862-014-0214-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 09/25/2014] [Indexed: 12/25/2022] Open
Abstract
Background Vetulicolians are one of the most problematic and controversial Cambrian fossil groups, having been considered as arthropods, chordates, kinorhynchs, or their own phylum. Mounting evidence suggests that vetulicolians are deuterostomes, but affinities to crown-group phyla are unresolved. Results A new vetulicolian from the Emu Bay Shale Konservat-Lagerstätte, South Australia, Nesonektris aldridgei gen. et sp. nov., preserves an axial, rod-like structure in the posterior body region that resembles a notochord in its morphology and taphonomy, with notable similarity to early decay stages of the notochord of extant cephalochordates and vertebrates. Some of its features are also consistent with other structures, such as a gut or a coelomic cavity. Conclusions Phylogenetic analyses resolve a monophyletic Vetulicolia as sister-group to tunicates (Urochordata) within crown Chordata, and this holds even if they are scored as unknown for all notochord characters. The hypothesis that the free-swimming vetulicolians are the nearest relatives of tunicates suggests that a perpetual free-living life cycle was primitive for tunicates. Characters of the common ancestor of Vetulicolia + Tunicata include distinct anterior and posterior body regions – the former being non-fusiform and used for filter feeding and the latter originally segmented – plus a terminal mouth, absence of pharyngeal bars, the notochord restricted to the posterior body region, and the gut extending to the end of the tail. Electronic supplementary material The online version of this article (doi:10.1186/s12862-014-0214-z) contains supplementary material, which is available to authorized users.
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41
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A primitive fish from the Cambrian of North America. Nature 2014; 512:419-22. [DOI: 10.1038/nature13414] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 04/29/2014] [Indexed: 12/16/2022]
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42
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Abstract
A spectacular Cambrian soft bodied fauna some 40 km from Walcott's original Burgess Shale locality includes over 50 taxa, some 20% new to science. New anatomical evidence from this site will illuminate the evolution of early marine animals.
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43
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Flammang B. The fish tail as a derivation from axial musculoskeletal anatomy: an integrative analysis of functional morphology. ZOOLOGY 2014; 117:86-92. [DOI: 10.1016/j.zool.2013.10.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 10/08/2013] [Accepted: 10/09/2013] [Indexed: 10/26/2022]
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Kodymirus and the case for convergence of raptorial appendages in Cambrian arthropods. Naturwissenschaften 2013; 100:811-25. [DOI: 10.1007/s00114-013-1081-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 07/03/2013] [Accepted: 07/05/2013] [Indexed: 10/26/2022]
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MALLATT JON, HOLLAND NICHOLAS. Pikaia gracilensWalcott: Stem Chordate, or Already Specialized in the Cambrian? JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2013; 320:247-71. [DOI: 10.1002/jez.b.22500] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 03/11/2013] [Indexed: 12/25/2022]
Affiliation(s)
- JON MALLATT
- School of Biological Sciences; Washington State University; Pullman; Washington
| | - NICHOLAS HOLLAND
- Scripps Institution of Oceanography; University of California; San Diego, La Jolla; California
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Ivashkin E, Adameyko I. Progenitors of the protochordate ocellus as an evolutionary origin of the neural crest. EvoDevo 2013; 4:12. [PMID: 23575111 PMCID: PMC3626940 DOI: 10.1186/2041-9139-4-12] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 12/28/2012] [Indexed: 01/01/2023] Open
Abstract
The neural crest represents a highly multipotent population of embryonic stem cells found only in vertebrate embryos. Acquisition of the neural crest during the evolution of vertebrates was a great advantage, providing Chordata animals with the first cellular cartilage, bone, dentition, advanced nervous system and other innovations. Today not much is known about the evolutionary origin of neural crest cells. Here we propose a novel scenario in which the neural crest originates from neuroectodermal progenitors of the pigmented ocelli in Amphioxus-like animals. We suggest that because of changes in photoreception needs, these multipotent progenitors of photoreceptors gained the ability to migrate outside of the central nervous system and subsequently started to give rise to neural, glial and pigmented progeny at the periphery.
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Affiliation(s)
- Evgeniy Ivashkin
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheeles vag 1 A1, Stockholm 17177, Sweden.
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Ou Q, Morris SC, Han J, Zhang Z, Liu J, Chen A, Zhang X, Shu D. Evidence for gill slits and a pharynx in Cambrian vetulicolians: implications for the early evolution of deuterostomes. BMC Biol 2012; 10:81. [PMID: 23031545 PMCID: PMC3517509 DOI: 10.1186/1741-7007-10-81] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Accepted: 10/02/2012] [Indexed: 12/19/2022] Open
Abstract
Background Vetulicolians are a group of Cambrian metazoans whose distinctive bodyplan continues to present a major phylogenetic challenge. Thus, we see vetulicolians assigned to groups as disparate as deuterostomes and ecdysozoans. This divergence of opinions revolves around a strikingly arthropod-like body, but one that also bears complex lateral structures on its anterior section interpreted as pharyngeal openings. Establishing the homology of these structures is central to resolving where vetulicolians sit in metazoan phylogeny. Results New material from the Chengjiang Lagerstätte helps to resolve this issue. Here, we demonstrate that these controversial structures comprise grooves with a series of openings. The latter are oval in shape and associated with a complex anatomy consistent with control of their opening and closure. Remains of what we interpret to be a musculature, combined with the capacity for the grooves to contract, indicate vetulicolians possessed a pumping mechanism that could process considerable volumes of seawater. Our observations suggest that food captured in the anterior cavity was transported to dorsal and ventral gutters, which then channeled material to the intestine. This arrangement appears to find no counterpart in any known fossil or extant arthropod (or any other ecdysozoan). Anterior lateral perforations, however, are diagnostic of deuterostomes. Conclusions If the evidence is against vetulicolians belonging to one or other group of ecdysozoan, then two phylogenetic options seem to remain. The first is that such features as vetulicolians possess are indicative of either a position among the bilaterians or deuterostomes but apart from the observation that they themselves form a distinctive and recognizable clade current evidence can permit no greater precision as to their phylogenetic placement. We argue that this is too pessimistic a view, and conclude that evidence points towards vetulicolians being members of the stem-group deuterostomes; a group best known as the chordates (amphioxus, tunicates, vertebrates), but also including the ambulacrarians (echinoderms, hemichordates), and xenoturbellids. If the latter, first they demonstrate that these members of the stem group show few similarities to the descendant crown group representatives. Second, of the key innovations that underpinned deuterostome success, the earliest and arguably most seminal was the evolution of openings that define the pharyngeal gill slits of hemichordates (and some extinct echinoderms) and chordates.
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Affiliation(s)
- Qiang Ou
- Early Life Evolution Laboratory, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China.
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Lacalli T. The Middle Cambrian fossil Pikaia and the evolution of chordate swimming. EvoDevo 2012; 3:12. [PMID: 22695332 PMCID: PMC3390900 DOI: 10.1186/2041-9139-3-12] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 06/13/2012] [Indexed: 12/02/2022] Open
Abstract
Conway Morris and Caron (2012) have recently published an account of virtually all the available information on Pikaia gracilens, a well-known Cambrian fossil and supposed basal chordate, and propose on this basis some new ideas about Pikaia’s anatomy and evolutionary significance. Chief among its chordate-like features are the putative myomeres, a regular series of vertical bands that extends the length of the body. These differ from the myomeres of living chordates in that boundaries between them (the myosepta) are gently curved, with minimal overlap, whereas amphioxus and vertebrates have strongly overlapping V- and W-shaped myomeres. The implication, on biomechanical grounds, is that myomeres in Pikaia exerted much less tension on the myosepta, so the animal would have been incapable of swimming as rapidly as living chordates operating in the fast-twitch mode used for escape and attack. Pikaia either lacked the fast-twitch fibers necessary for such speeds, having instead only slow-twitch fibers, or it had an ancestral fiber type with functional capabilities more like modern slow fibers than fast ones. The first option is supported by the sequence of development in zebrafish, where both myoseptum formation and fast fiber deployment show a dependence on slow fibers, which develop first. For Pikaia, the absence of fast fibers has both behavioral and anatomical implications, which are discussed. Among the latter is the possibility that a notochord may not have been needed as a primary stiffening device if other structures (for example, the dorsal organ) could perform that role.
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Affiliation(s)
- Thurston Lacalli
- Biology Department, University of Victoria, Cunningham Building, Victoria, BC, V8W-3N5, Canada.
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