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Wang D, Qiang Y, Guo J, Vannier J, Song Z, Peng J, Zhang B, Sun J, Yu Y, Zhang Y, Zhang T, Yang X, Han J. Early evolution of the ecdysozoan body plan. eLife 2024; 13:RP94709. [PMID: 38976315 PMCID: PMC11231812 DOI: 10.7554/elife.94709] [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] [Indexed: 07/09/2024] Open
Abstract
Extant ecdysozoans (moulting animals) are represented by a great variety of soft-bodied or articulated organisms that may or may not have appendages. However, controversies remain about the vermiform nature (i.e. elongated and tubular) of their ancestral body plan. We describe here Beretella spinosa gen. et sp. nov. a tiny (maximal length 3 mm) ecdysozoan from the lowermost Cambrian, Yanjiahe Formation, South China, characterized by an unusual sack-like appearance, single opening, and spiny ornament. Beretella spinosa gen. et sp. nov has no equivalent among animals, except Saccorhytus coronarius, also from the basal Cambrian. Phylogenetic analyses resolve both fossil species as a sister group (Saccorhytida) to all known Ecdysozoa, thus suggesting that ancestral ecdysozoans may have been non-vermiform animals. Saccorhytids are likely to represent an early off-shot along the stem-line Ecdysozoa. Although it became extinct during the Cambrian, this animal lineage provides precious insight into the early evolution of Ecdysozoa and the nature of the earliest representatives of the group.
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Affiliation(s)
- Deng Wang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi'an, China
| | - Yaqin Qiang
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Junfeng Guo
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Jean Vannier
- Université de Lyon, Université Claude Bernard Lyon 1, ENS de Lyon, CNRS, Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement (CNRS-UMR 5276), Villeurbanne, France
| | - Zuchen Song
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Jiaxin Peng
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Boyao Zhang
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Jie Sun
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi'an, China
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Yilun Yu
- Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yiheng Zhang
- School of Information Science and Technology, Northwest University, Xi'an, China
| | - Tao Zhang
- School of Information Science and Technology, Northwest University, Xi'an, China
| | - Xiaoguang Yang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi'an, China
| | - Jian Han
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi'an, China
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2
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Wang X, Liu AG, Chen Z, Wu C, Liu Y, Wan B, Pang K, Zhou C, Yuan X, Xiao S. A late-Ediacaran crown-group sponge animal. Nature 2024; 630:905-911. [PMID: 38839967 DOI: 10.1038/s41586-024-07520-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Accepted: 05/03/2024] [Indexed: 06/07/2024]
Abstract
Sponges are the most basal metazoan phylum1 and may have played important roles in modulating the redox architecture of Neoproterozoic oceans2. Although molecular clocks predict that sponges diverged in the Neoproterozoic era3,4, their fossils have not been unequivocally demonstrated before the Cambrian period5-8, possibly because Precambrian sponges were aspiculate and non-biomineralized9. Here we describe a late-Ediacaran fossil, Helicolocellus cantori gen. et sp. nov., from the Dengying Formation (around 551-539 million years ago) of South China. This fossil is reconstructed as a large, stemmed benthic organism with a goblet-shaped body more than 0.4 m in height, with a body wall consisting of at least three orders of nested grids defined by quadrate fields, resembling a Cantor dust fractal pattern. The resulting lattice is interpreted as an organic skeleton comprising orthogonally arranged cruciform elements, architecturally similar to some hexactinellid sponges, although the latter are built with biomineralized spicules. A Bayesian phylogenetic analysis resolves H. cantori as a crown-group sponge related to the Hexactinellida. H. cantori confirms that sponges diverged and existed in the Precambrian as non-biomineralizing animals with an organic skeleton. Considering that siliceous biomineralization may have evolved independently among sponge classes10-13, we question the validity of biomineralized spicules as a necessary criterion for the identification of Precambrian sponge fossils.
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Affiliation(s)
- Xiaopeng Wang
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
- University of Chinese Academy of Sciences, Beijing, China
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - Alexander G Liu
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - Zhe Chen
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Chengxi Wu
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yarong Liu
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Bin Wan
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China.
- University of Chinese Academy of Sciences, Beijing, China.
| | - Ke Pang
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Chuanming Zhou
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
- University of Chinese Academy of Sciences, Nanjing, Nanjing, China
| | - Xunlai Yuan
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China.
- University of Chinese Academy of Sciences, Beijing, China.
| | - Shuhai Xiao
- Department of Geosciences and Global Change Centre, Virginia Tech, Blacksburg, VA, USA.
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3
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Boag TH, Busch JF, Gooley JT, Strauss JV, Sperling EA. Deep-water first occurrences of Ediacara biota prior to the Shuram carbon isotope excursion in the Wernecke Mountains, Yukon, Canada. GEOBIOLOGY 2024; 22:e12597. [PMID: 38700422 DOI: 10.1111/gbi.12597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 02/29/2024] [Accepted: 03/27/2024] [Indexed: 05/05/2024]
Abstract
Ediacara-type macrofossils appear as early as ~575 Ma in deep-water facies of the Drook Formation of the Avalon Peninsula, Newfoundland, and the Nadaleen Formation of Yukon and Northwest Territories, Canada. Our ability to assess whether a deep-water origination of the Ediacara biota is a genuine reflection of evolutionary succession, an artifact of an incomplete stratigraphic record, or a bathymetrically controlled biotope is limited by a lack of geochronological constraints and detailed shelf-to-slope transects of Ediacaran continental margins. The Ediacaran Rackla Group of the Wernecke Mountains, NW Canada, represents an ideal shelf-to-slope depositional system to understand the spatiotemporal and environmental context of Ediacara-type organisms' stratigraphic occurrence. New sedimentological and paleontological data presented herein from the Wernecke Mountains establish a stratigraphic framework relating shelfal strata in the Goz/Corn Creek area to lower slope deposits in the Nadaleen River area. We report new discoveries of numerous Aspidella hold-fast discs, indicative of frondose Ediacara organisms, from deep-water slope deposits of the Nadaleen Formation stratigraphically below the Shuram carbon isotope excursion (CIE) in the Nadaleen River area. Such fossils are notably absent in coeval shallow-water strata in the Goz/Corn Creek region despite appropriate facies for potential preservation. The presence of pre-Shuram CIE Ediacara-type fossils occurring only in deep-water facies within a basin that has equivalent well-preserved shallow-water facies provides the first stratigraphic paleobiological support for a deep-water origination of the Ediacara biota. In contrast, new occurrences of Ediacara-type fossils (including juvenile fronds, Beltanelliformis, Aspidella, annulated tubes, and multiple ichnotaxa) are found above the Shuram CIE in both deep- and shallow-water deposits of the Blueflower Formation. Given existing age constraints on the Shuram CIE, it appears that Ediacaran organisms may have originated in the deeper ocean and lived there for up to ~15 million years before migrating into shelfal environments in the terminal Ediacaran. This indicates unique ecophysiological constraints likely shaped the initial habitat preference and later environmental expansion of the Ediacara biota.
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Affiliation(s)
- Thomas H Boag
- Department of Earth and Planetary Science, Stanford University, Stanford, California, USA
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut, USA
- Department of Geosciences, Princeton University, Princeton, New Jersey, USA
| | - James F Busch
- Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | - Jared T Gooley
- Alaska Science Center, U.S. Geological Survey, Anchorage, Alaska, USA
| | - Justin V Strauss
- Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | - Erik A Sperling
- Department of Earth and Planetary Science, Stanford University, Stanford, California, USA
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4
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Sun W, Yin Z, Liu P, Zhu M, Donoghue P. Developmental biology of Spiralicellula and the Ediacaran origin of crown metazoans. Proc Biol Sci 2024; 291:20240101. [PMID: 38808442 DOI: 10.1098/rspb.2024.0101] [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: 01/13/2024] [Accepted: 04/23/2024] [Indexed: 05/30/2024] Open
Abstract
The early Ediacaran Weng'an biota (Doushantuo Formation, South China) provides a rare window onto the period of Earth history in which molecular timescales have inferred the initial phase of crown-metazoan diversification. Interpretation of the embryo-like fossils that dominate the biota remains contentious because they are morphologically simple and so difficult to constrain phylogenetically. Spiralicellula from the Weng'an biota is distinguished by spiral internal bodies, allied through development to Megasphaera or Helicoforamina and interpreted variously as metazoan embryos, encysting protists, or chlorophycean green algae. Here we show, using X-ray microtomography, that Spiralicellula has a single-layered outer envelope and no more than 32 internal cells, often preserving a nucleus and yolk granules. There is no correlation between the extent of spiral development and the number of component cells; rather, the spiral developed with each palintomic stage, associated with cell disaggregation and reorientation. Evidence for envelope thinning and cell loss was observed in all developmental stages, reflecting non-deterministic shedding of gametes or amoebae. The developmental biology of Spiralicellula is similar to Megasphaera and Helicoforamina, which otherwise exhibit more rounds of palintomy. We reject a crown-metazoan affinity for Spiralicellula and all other components of the Weng'an biota, diminishing the probability of crown-metazoan diversification before the early Ediacaran.
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Affiliation(s)
- Weichen Sun
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China
| | - Zongjun Yin
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China
- Nanjing College, University of Chinese Academy of Sciences, Nanjing 211135, People's Republic of China
| | - Pengju Liu
- Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, People's Republic of China
| | - Maoyan Zhu
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China
- Nanjing College, University of Chinese Academy of Sciences, Nanjing 211135, People's Republic of China
| | - Philip Donoghue
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK
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5
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Delahooke KM, Liu AG, Stephenson NP, Mitchell EG. 'Conga lines' of Ediacaran fronds: insights into the reproductive biology of early metazoans. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231601. [PMID: 39076788 PMCID: PMC11286166 DOI: 10.1098/rsos.231601] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 02/29/2024] [Accepted: 04/09/2024] [Indexed: 07/31/2024]
Abstract
Late Ediacaran strata from Newfoundland, Canada (~574-560 Ma) document near-census palaeocommunities of some of the earliest metazoans. Such preservation enables reproductive strategies to be inferred from the spatial distribution of populations of fossilized benthic organisms, previously revealing the existence of both propagule and stoloniferous reproductive modes among Ediacaran frondose taxa. Here, we describe 'conga lines': linear arrangements of more than three closely spaced fossil specimens. We calculate probabilistic models of point maps of 13 fossil-bearing bedding surfaces and show that four surfaces contain conga lines that are not the result of chance alignments. We then test whether these features could result from passive pelagic propagules settling in the lee of an existing frond, using computational fluid dynamics and discrete phase modelling. Under Ediacaran palaeoenvironmental conditions, preferential leeside settlement at the spatial scale of the conga lines is unlikely. We therefore conclude that these features are novel and do not reflect previously described reproductive strategies employed by Ediacaran organisms, suggesting the use of mixed reproductive strategies in the earliest animals. Such strategies enabled Ediacaran frondose taxa to act as reproductive generalists and may be an important facet of early metazoan evolution.
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Affiliation(s)
| | - Alexander G. Liu
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - Nile P. Stephenson
- Department of Zoology, University of Cambridge, Cambridge, UK
- Museum of Zoology, University of Cambridge, Cambridge, UK
| | - Emily G. Mitchell
- Department of Zoology, University of Cambridge, Cambridge, UK
- Museum of Zoology, University of Cambridge, Cambridge, UK
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6
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Sierra NC, Gold DA. The evolution of cnidarian stinging cells supports a Precambrian radiation of animal predators. Evol Dev 2024; 26:e12469. [PMID: 38236185 DOI: 10.1111/ede.12469] [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: 05/16/2023] [Revised: 11/22/2023] [Accepted: 12/31/2023] [Indexed: 01/19/2024]
Abstract
Cnidarians-the phylum including sea anemones, corals, jellyfish, and hydroids-are one of the oldest groups of predatory animals. Nearly all cnidarians are carnivores that use stinging cells called cnidocytes to ensnare and/or envenom their prey. However, there is considerable diversity in cnidocyte form and function. Tracing the evolutionary history of cnidocytes may therefore provide a proxy for early animal feeding strategies. In this study, we generated a time-calibrated molecular clock of cnidarians and performed ancestral state reconstruction on 12 cnidocyte types to test the hypothesis that the original cnidocyte was involved in prey capture. We conclude that the first cnidarians had only the simplest and least specialized cnidocyte type (the isorhiza) which was just as likely to be used for adhesion and/or defense as the capture of prey. A rapid diversification of specialized cnidocytes occurred through the Ediacaran (~654-574 million years ago), with major subgroups developing unique sets of cnidocytes to match their distinct feeding styles. These results are robust to changes in the molecular clock model, and are consistent with growing evidence for an Ediacaran diversification of animals. Our work also provides insight into the evolution of this complex cell type, suggesting that convergence of forms is rare, with the mastigophore being an interesting counterexample.
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Affiliation(s)
- Noémie C Sierra
- Department of Earth and Planetary Sciences, University of California, Davis, Davis, California, USA
- Integrative Genetics and Genomics, University of California, Davis, Davis, California, USA
| | - David A Gold
- Department of Earth and Planetary Sciences, University of California, Davis, Davis, California, USA
- Integrative Genetics and Genomics, University of California, Davis, Davis, California, USA
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7
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Zhang H, Xiao S, Eriksson ME, Duan B, Maas A. Musculature of an Early Cambrian cycloneuralian animal. Proc Biol Sci 2023; 290:20231803. [PMID: 37817588 PMCID: PMC10565385 DOI: 10.1098/rspb.2023.1803] [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: 08/10/2023] [Accepted: 09/18/2023] [Indexed: 10/12/2023] Open
Abstract
Cycloneuralians are ecdysozoans with a fossil record extending to the Early Cambrian Fortunian Age and represented mostly by cuticular integuments. However, internal anatomies of Fortunian cycloneuralians are virtually unknown, hampering our understanding of their functional morphology and phylogenetic relationships. Here we report the exceptional preservation of cycloneuralian introvert musculature in Fortunian rocks of South China. The musculature consists of an introvert body-wall muscular grid of four circular and 36 radially arranged longitudinal muscle bundles, as well as an introvert circular muscle associated with 19 roughly radially arranged, short retractors. Collectively, these features support at least a scalidophoran affinity, and the absence of muscles associated with a mouth cone and scalids further indicates a priapulan affinity. As in modern scalidophorans, the fossil musculature, and particularly the introvert circular muscle retractors, may have controlled introvert inversion and facilitated locomotion and feeding. This work supports the evolution of scalidophoran-like or priapulan-like introvert musculature in cycloneuralians at the beginning of the Cambrian Period.
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Affiliation(s)
- Huaqiao Zhang
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA
| | | | - Baichuan Duan
- Key Laboratory of Marine Geology and Metallogeny, First Institute of Oceanography, Ministry of Natural Resource, Qingdao 266061, People's Republic of China
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8
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Travert M, Boohar R, Sanders SM, Boosten M, Leclère L, Steele RE, Cartwright P. Coevolution of the Tlx homeobox gene with medusa development (Cnidaria: Medusozoa). Commun Biol 2023; 6:709. [PMID: 37433830 DOI: 10.1038/s42003-023-05077-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 06/27/2023] [Indexed: 07/13/2023] Open
Abstract
Cnidarians display a wide diversity of life cycles. Among the main cnidarian clades, only Medusozoa possesses a swimming life cycle stage called the medusa, alternating with a benthic polyp stage. The medusa stage was repeatedly lost during medusozoan evolution, notably in the most diverse medusozoan class, Hydrozoa. Here, we show that the presence of the homeobox gene Tlx in Cnidaria is correlated with the presence of the medusa stage, the gene having been lost in clades that ancestrally lack a medusa (anthozoans, endocnidozoans) and in medusozoans that secondarily lost the medusa stage. Our characterization of Tlx expression indicate an upregulation of Tlx during medusa development in three distantly related medusozoans, and spatially restricted expression patterns in developing medusae in two distantly related species, the hydrozoan Podocoryna carnea and the scyphozoan Pelagia noctiluca. These results suggest that Tlx plays a key role in medusa development and that the loss of this gene is likely linked to the repeated loss of the medusa life cycle stage in the evolution of Hydrozoa.
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Affiliation(s)
- Matthew Travert
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA.
| | - Reed Boohar
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA
| | - Steven M Sanders
- Department of Surgery, Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Manon Boosten
- Sorbonne Université, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-Mer (LBDV), Villefranche-sur-Mer, France
- Sorbonne Université, CNRS, Laboratoire d'Océanographie de Villefranche, Villefranche-sur-Mer, France
| | - Lucas Leclère
- Sorbonne Université, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-Mer (LBDV), Villefranche-sur-Mer, France
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins, BIOM, Banyuls-sur-Mer, France
| | - Robert E Steele
- Department of Biological Chemistry, University of California, Irvine, CA, USA
| | - Paulyn Cartwright
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA
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9
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Yang J, Lan T, Zhang XG, Smith MR. Protomelission is an early dasyclad alga and not a Cambrian bryozoan. Nature 2023; 615:468-471. [PMID: 36890226 DOI: 10.1038/s41586-023-05775-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 01/31/2023] [Indexed: 03/10/2023]
Abstract
The animal phyla and their associated body plans originate from a singular burst of evolution occurring during the Cambrian period, over 500 million years ago1. The phylum Bryozoa, the colonial 'moss animals', have been the exception: convincing skeletons of this biomineralizing clade have been absent from Cambrian strata, in part because potential bryozoan fossils are difficult to distinguish from the modular skeletons of other animal and algal groups2,3. At present, the strongest candidate4 is the phosphatic microfossil Protomelission5. Here we describe exceptionally preserved non-mineralized anatomy in Protomelission-like macrofossils from the Xiaoshiba Lagerstätte6. Taken alongside the detailed skeletal construction and the potential taphonomic origin of 'zooid apertures', we consider that Protomelission is better interpreted as the earliest dasycladalean green alga-emphasizing the ecological role of benthic photosynthesizers in early Cambrian communities. Under this interpretation, Protomelission cannot inform the origins of the bryozoan body plan; despite a growing number of promising candidates7-9, there remain no unequivocal bryozoans of Cambrian age.
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Affiliation(s)
- Jie Yang
- Institute of Palaeontology, Yunnan University, Chenggong, Kunming, China
| | - Tian Lan
- College of Resources and Environmental Engineering, Guizhou University, Guiyang, China
| | - Xi-Guang Zhang
- Institute of Palaeontology, Yunnan University, Chenggong, Kunming, China.
| | - Martin R Smith
- Department of Earth Sciences, Durham University, Durham, UK.
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10
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Dunn FS, Kenchington CG, Parry LA, Clark JW, Kendall RS, Wilby PR. A crown-group cnidarian from the Ediacaran of Charnwood Forest, UK. Nat Ecol Evol 2022; 6:1095-1104. [PMID: 35879540 PMCID: PMC9349040 DOI: 10.1038/s41559-022-01807-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 05/23/2022] [Indexed: 11/17/2022]
Abstract
Cnidarians are a disparate and ancient phylum, encompassing corals and jellyfish, and occupy both the pelagic and benthic realms. They have a rich fossil record from the Phanerozoic eon lending insight into the early history of the group but, although cnidarians diverged from other animals in the Precambrian period, their record from the Ediacaran period (635–542 million years ago) is controversial. Here, we describe a new fossil cnidarian—Auroralumina attenboroughii gen. et sp. nov.—from the Ediacaran of Charnwood Forest (557–562 million years ago) that shows two bifurcating polyps enclosed in a rigid, polyhedral, organic skeleton with evidence of simple, densely packed tentacles. Auroralumina displays a suite of characters allying it to early medusozoans but shows others more typical of Anthozoa. Phylogenetic analyses recover Auroralumina as a stem-group medusozoan and, therefore, the oldest crown-group cnidarian. Auroralumina demonstrates both the establishment of the crown group of an animal phylum and the fixation of its body plan tens of millions of years before the Cambrian diversification of animal life. A new fossil cnidarian, Auroralumina attenboroughi, from the Ediacaran of Charnwood Forest, UK, described as showing mosaic anthozoan and medusozoan characters, is the oldest yet-known crown-group cnidarian.
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Affiliation(s)
- F S Dunn
- Oxford University Museum of Natural History, University of Oxford, Oxford, UK.
| | - C G Kenchington
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - L A Parry
- Department of Earth Sciences, University of Oxford, Oxford, UK
| | - J W Clark
- School of Biological Sciences, University of Bristol, Bristol, UK
| | - R S Kendall
- British Geological Survey, Cardiff University, Cardiff, UK
| | - P R Wilby
- British Geological Survey, Nicker Hill, Keyworth, Nottingham, UK.,Department of Geology, University of Leicester, Leicester, UK
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11
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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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12
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Were the First Trace Fossils Really Burrows or Could They Have Been Made by Sediment-Displacive Chemosymbiotic Organisms? Life (Basel) 2022; 12:life12020136. [PMID: 35207424 PMCID: PMC8880172 DOI: 10.3390/life12020136] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 01/13/2022] [Accepted: 01/15/2022] [Indexed: 11/17/2022] Open
Abstract
This review asks some hard questions about what the enigmatic graphoglyptid trace fossils are, documents some of their early fossil record from the Ediacaran–Cambrian transition and explores the idea that they may not have been fossils at all. Most researchers have considered the Graphoglyptida to have had a microbial-farming mode of life similar to that proposed for the fractal Ediacaran Rangeomorpha. This begs the question “What are the Graphoglyptida if not the Rangeomorpha persevering” and if so then “What if…?”. This provocative idea has at its roots some fundamental questions about how to distinguish burrows sensu-stricto from the external molds of endobenthic sediment displacive organisms.
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13
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McIlroy D, Dufour SC, Taylor R, Nicholls R. The role of symbiosis in the first colonization of the seafloor by macrobiota: Insights from the oldest Ediacaran biota (Newfoundland, Canada). Biosystems 2021; 205:104413. [PMID: 33794297 DOI: 10.1016/j.biosystems.2021.104413] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 03/19/2021] [Accepted: 03/20/2021] [Indexed: 01/23/2023]
Abstract
The earliest record of animal life comes from the Ediacaran of Newfoundland, including dm scale fossil organisms, most of which are inferred to have been epibenthic immotile eumetazoans. This work introduces the palaeobiology of the major fossil groups in the Newfoundland assemblages including strange fractal-like taxa and addresses some of biogeochemical challenges such as sulfide buildup that could most easily have been overcome by symbiogenesis. Specifically, the epibenthic reclining nature of some of the Ediacaran biota-with their fractal-like high surface area lower surfaces-are considered to have been well designed for gaining nutriment from chemosynthetic, sulfur-oxidizing bacteria. This view constitutes a shift away from the view that most of the biota were anomalously large osmotrophs.
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Affiliation(s)
- Duncan McIlroy
- Department of Earth Sciences, Memorial University of Newfoundland, St. John's, NL, A1B 3X5, Canada; Bonne Bay Marine Station, Memorial University of Newfoundland, Norris Point, PO Box 69, A0K 3V0, Canada.
| | - Suzanne C Dufour
- Department of Biology, Memorial University of Newfoundland, St. John's, NL, A1B 3X9, Canada
| | - Rod Taylor
- Department of Earth Sciences, Memorial University of Newfoundland, St. John's, NL, A1B 3X5, Canada
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14
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McFadden CS, Quattrini AM, Brugler MR, Cowman PF, Dueñas LF, Kitahara MV, Paz-García DA, Reimer JD, Rodríguez E. Phylogenomics, Origin, and Diversification of Anthozoans (Phylum Cnidaria). Syst Biol 2021; 70:635-647. [PMID: 33507310 DOI: 10.1093/sysbio/syaa103] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 12/18/2020] [Accepted: 12/21/2020] [Indexed: 01/19/2023] Open
Abstract
Anthozoan cnidarians (corals and sea anemones) include some of the world's most important foundation species, capable of building massive reef complexes that support entire ecosystems. Although previous molecular phylogenetic analyses have revealed widespread homoplasy of the morphological characters traditionally used to define orders and families of anthozoans, analyses using mitochondrial genes or rDNA have failed to resolve many key nodes in the phylogeny. With a fully resolved, time-calibrated phylogeny for 234 species constructed from hundreds of ultraconserved elements and exon loci, we explore the evolutionary origins of the major clades of Anthozoa and some of their salient morphological features. The phylogeny supports reciprocally monophyletic Hexacorallia and Octocorallia, with Ceriantharia as the earliest diverging hexacorals; two reciprocally monophyletic clades of Octocorallia; and monophyly of all hexacoral orders with the exception of the enigmatic sea anemone Relicanthus daphneae. Divergence dating analyses place Anthozoa in the Cryogenian to Tonian periods (648-894 Ma), older than has been suggested by previous studies. Ancestral state reconstructions indicate that the ancestral anthozoan was a solitary polyp that had bilateral symmetry and lacked a skeleton. Colonial growth forms and the ability to precipitate calcium carbonate evolved in the Ediacaran (578 Ma) and Cambrian (503 Ma) respectively; these hallmarks of reef-building species have subsequently arisen multiple times independently in different orders. Anthozoans formed associations with photosymbionts by the Devonian (383 Ma), and photosymbioses have been gained and lost repeatedly in all orders. Together, these results have profound implications for the interpretation of the Precambrian environment and the early evolution of metazoans.[Bilateral symmetry; coloniality; coral; early metazoans; exon capture; Hexacorallia; Octocorallia photosymbiosis; sea anemone; ultraconserved elements.].
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Affiliation(s)
- Catherine S McFadden
- Department of Biology, Harvey Mudd College, 1250 N. Dartmouth Ave., Claremont, CA 91711 USA
| | - Andrea M Quattrini
- Department of Biology, Harvey Mudd College, 1250 N. Dartmouth Ave., Claremont, CA 91711 USA.,Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
| | - Mercer R Brugler
- Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA.,Biological Sciences Department, NYC College of Technology, City University of New York, 285 Jay Street, Brooklyn, NY 11201, USA.,Department of Natural Sciences, University of South Carolina Beaufort, 801 Carteret Street, Beaufort, SC 29902, USA
| | - Peter F Cowman
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia.,Biodiversity and Geosciences Program, Museum of Tropical Queensland, Queensland Museum, Townsville, QLD 4810, Australia
| | - Luisa F Dueñas
- Departamento de Biología, Facultad de Ciencias, Universidad Nacional de Colombia-Sede Bogotá, Carrera 30 No.45-03 Edificio 421, Bogotá, D.C., Colombia
| | - Marcelo V Kitahara
- Department of Marine Science, Federal University of São Paulo, Santos, SP 11070-100 Brazil.,Centre for Marine Biology, University of São Paulo, São Sebastião, SP 11612-109 Brazil
| | - David A Paz-García
- CONACyT-Centro de Investigaciones Biológicas del Noroeste (CIBNOR). Laboratorio de Necton y Ecología de Arrecifes. Calle IPN 195, Col. Playa Palo de Santa Rita Sur, 23096 La Paz, B.C.S., México
| | - James D Reimer
- Molecular Invertebrate Systematics and Ecology Laboratory, Department of Marine Science, Chemistry, and Biology, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.,Tropical Biosphere Research Center, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan
| | - Estefanía Rodríguez
- Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA
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15
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Julca I, Marcet-Houben M, Cruz F, Vargas-Chavez C, Johnston JS, Gómez-Garrido J, Frias L, Corvelo A, Loska D, Cámara F, Gut M, Alioto T, Latorre A, Gabaldón T. Phylogenomics Identifies an Ancestral Burst of Gene Duplications Predating the Diversification of Aphidomorpha. Mol Biol Evol 2020; 37:730-756. [PMID: 31702774 PMCID: PMC7038657 DOI: 10.1093/molbev/msz261] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Aphids (Aphidoidea) are a diverse group of hemipteran insects that feed on plant phloem sap. A common finding in studies of aphid genomes is the presence of a large number of duplicated genes. However, when these duplications occurred remains unclear, partly due to the high relatedness of sequenced species. To better understand the origin of aphid duplications we sequenced and assembled the genome of Cinara cedri, an early branching lineage (Lachninae) of the Aphididae family. We performed a phylogenomic comparison of this genome with 20 other sequenced genomes, including the available genomes of five other aphids, along with the transcriptomes of two species belonging to Adelgidae (a closely related clade to the aphids) and Coccoidea. We found that gene duplication has been pervasive throughout the evolution of aphids, including many parallel waves of recent, species-specific duplications. Most notably, we identified a consistent set of very ancestral duplications, originating from a large-scale gene duplication predating the diversification of Aphidomorpha (comprising aphids, phylloxerids, and adelgids). Genes duplicated in this ancestral wave are enriched in functions related to traits shared by Aphidomorpha, such as association with endosymbionts, and adaptation to plant defenses and phloem-sap-based diet. The ancestral nature of this duplication wave (106-227 Ma) and the lack of sufficiently conserved synteny make it difficult to conclude whether it originated from a whole-genome duplication event or, alternatively, from a burst of large-scale segmental duplications. Genome sequencing of other aphid species belonging to different Aphidomorpha and related lineages may clarify these findings.
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Affiliation(s)
- Irene Julca
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Marina Marcet-Houben
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Fernando Cruz
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Carlos Vargas-Chavez
- Institute for Integrative Systems Biology (I2SysBio), University of Valencia and CSIC, Valencia, Spain
| | | | - Jèssica Gómez-Garrido
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Leonor Frias
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - André Corvelo
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
- New York Genome Center, New York, NY
| | - Damian Loska
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Francisco Cámara
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Marta Gut
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Department of Experimental and Health Sciences, Barcelona, Spain
| | - Tyler Alioto
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Department of Experimental and Health Sciences, Barcelona, Spain
| | - Amparo Latorre
- Institute for Integrative Systems Biology (I2SysBio), University of Valencia and CSIC, Valencia, Spain
- Joint Unit in Genomics and Health, Foundation for the Promotion of Sanitary and Biomedical Research (FISABIO) and University of Valencia, Valencia, Spain
| | - Toni Gabaldón
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Department of Experimental and Health Sciences, Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
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16
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Hancy AD, Antcliffe JB. Anoxia can increase the rate of decay for cnidarian tissue: Using Actinia equina to understand the early fossil record. GEOBIOLOGY 2020; 18:167-184. [PMID: 31990129 DOI: 10.1111/gbi.12370] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 10/02/2019] [Accepted: 11/05/2019] [Indexed: 06/10/2023]
Abstract
An experimental decay methodology is developed for a cnidarian model organism to serve as a comparison to the many previous such studies on bilaterians. This allows an examination of inherent bias against the fossilisation of cnidarian tissue and their diagnostic characters, under what conditions these occur, and in what way. The decay sequence of Actinia equina was examined under a series of controlled conditions. These experiments show that cnidarian decay begins with an initial rupturing of the epidermis, followed by rapid loss of recognisable internal morphological characters. This suggests that bacteria work quicker on the epidermis than autolysis does on the internal anatomy. The data also show that diploblastic tissue is not universally decayed more slowly under anoxic or reducing conditions than under oxic conditions. Indeed, some cnidarian characters decay more rapidly under anoxic conditions than they do under oxic conditions. This suggests the decay pathways acting may be different to those affecting soft bilaterian tissue such as soft epidermis and internal organs. What is most important in the decay of soft polyp anatomy is the microbial community, which can be dominated by oxic or anoxic bacteria. Different Lagerstätte, even of the same type, will inevitably have subtle difference in their bacterial communities, which among other factors, could be a control on soft polyp preservation leading to either an absence of compelling soft anthozoans (Burgess Shale) or an astonishing abundance (Qingjiang biota).
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Affiliation(s)
- Anthony D Hancy
- School of Earth Sciences, University of Bristol, Bristol, UK
| | - Jonathan B Antcliffe
- Oxford University Museum of Natural History, Oxford, UK
- Institut des Sciences de la Terre, Bâtiment Géopolis, UNIL-Mouline, Université de Lausanne, Lausanne, Switzerland
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17
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Erwin DH. The origin of animal body plans: a view from fossil evidence and the regulatory genome. Development 2020; 147:147/4/dev182899. [DOI: 10.1242/dev.182899] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
ABSTRACT
The origins and the early evolution of multicellular animals required the exploitation of holozoan genomic regulatory elements and the acquisition of new regulatory tools. Comparative studies of metazoans and their relatives now allow reconstruction of the evolution of the metazoan regulatory genome, but the deep conservation of many genes has led to varied hypotheses about the morphology of early animals and the extent of developmental co-option. In this Review, I assess the emerging view that the early diversification of animals involved small organisms with diverse cell types, but largely lacking complex developmental patterning, which evolved independently in different bilaterian clades during the Cambrian Explosion.
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Affiliation(s)
- Douglas H. Erwin
- Department of Paleobiology, MRC-121, National Museum of Natural History, PO Box 37012, Washington, DC 20013-7012, USA
- Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA
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18
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Schiffbauer JD, Selly T, Jacquet SM, Merz RA, Nelson LL, Strange MA, Cai Y, Smith EF. Discovery of bilaterian-type through-guts in cloudinomorphs from the terminal Ediacaran Period. Nat Commun 2020; 11:205. [PMID: 31924764 PMCID: PMC6954273 DOI: 10.1038/s41467-019-13882-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 12/04/2019] [Indexed: 11/08/2022] Open
Abstract
The fossil record of the terminal Ediacaran Period is typified by the iconic index fossil Cloudina and its relatives. These tube-dwellers are presumed to be primitive metazoans, but resolving their phylogenetic identity has remained a point of contention. The root of the problem is a lack of diagnostic features; that is, phylogenetic interpretations have largely centered on the only available source of information-their external tubes. Here, using tomographic analyses of fossils from the Wood Canyon Formation (Nevada, USA), we report evidence of recognizable soft tissues within their external tubes. Although alternative interpretations are plausible, these internal cylindrical structures may be most appropriately interpreted as digestive tracts, which would be, to date, the earliest-known occurrence of such features in the fossil record. If this interpretation is correct, their nature as one-way through-guts not only provides evidence for establishing these fossils as definitive bilaterians but also has implications for the long-debated phylogenetic position of the broader cloudinomorphs.
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Affiliation(s)
- James D Schiffbauer
- Department of Geological Sciences, University of Missouri, Columbia, MO, 65211, USA.
- X-ray Microanalysis Core, University of Missouri, Columbia, MO, 65211, USA.
| | - Tara Selly
- Department of Geological Sciences, University of Missouri, Columbia, MO, 65211, USA.
- X-ray Microanalysis Core, University of Missouri, Columbia, MO, 65211, USA.
| | - Sarah M Jacquet
- Department of Geological Sciences, University of Missouri, Columbia, MO, 65211, USA
| | - Rachel A Merz
- Biology Department, Swarthmore College, Swarthmore, PA, 19081, USA
| | - Lyle L Nelson
- Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Michael A Strange
- Department of Geoscience, University of Nevada, Las Vegas, Las Vegas, NV, 89154, USA
| | - Yaoping Cai
- Shaanxi Key Laboratory of Early Life and Environment, State Key Laboratory of Continental Dynamics, and Department of Geology, Northwest University, Xi'an, 710069, China
| | - Emily F Smith
- Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, 21218, USA
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19
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Medusozoan genomes inform the evolution of the jellyfish body plan. Nat Ecol Evol 2019; 3:811-822. [PMID: 30988488 DOI: 10.1038/s41559-019-0853-y] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 02/26/2019] [Indexed: 01/01/2023]
Abstract
Cnidarians are astonishingly diverse in body form and lifestyle, including the presence of a jellyfish stage in medusozoans and its absence in anthozoans. Here, we sequence the genomes of Aurelia aurita (a scyphozoan) and Morbakka virulenta (a cubozoan) to understand the molecular mechanisms responsible for the origin of the jellyfish body plan. We show that the magnitude of genetic differences between the two jellyfish types is equivalent, on average, to the level of genetic differences between humans and sea urchins in the bilaterian lineage. About one-third of Aurelia genes with jellyfish-specific expression have no matches in the genomes of the coral and sea anemone, indicating that the polyp-to-jellyfish transition requires a combination of conserved and novel, medusozoa-specific genes. While no genomic region is specifically associated with the ability to produce a jellyfish stage, the arrangement of genes involved in the development of a nematocyte-a phylum-specific cell type-is highly structured and conserved in cnidarian genomes; thus, it represents a phylotypic gene cluster.
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20
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Sperling EA, Stockey RG. The Temporal and Environmental Context of Early Animal Evolution: Considering All the Ingredients of an "Explosion". Integr Comp Biol 2019; 58:605-622. [PMID: 30295813 DOI: 10.1093/icb/icy088] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Animals originated and evolved during a unique time in Earth history-the Neoproterozoic Era. This paper aims to discuss (1) when landmark events in early animal evolution occurred, and (2) the environmental context of these evolutionary milestones, and how such factors may have affected ecosystems and body plans. With respect to timing, molecular clock studies-utilizing a diversity of methodologies-agree that animal multicellularity had arisen by ∼800 million years ago (Ma) (Tonian period), the bilaterian body plan by ∼650 Ma (Cryogenian), and divergences between sister phyla occurred ∼560-540 Ma (late Ediacaran). Most purported Tonian and Cryogenian animal body fossils are unlikely to be correctly identified, but independent support for the presence of pre-Ediacaran animals is recorded by organic geochemical biomarkers produced by demosponges. This view of animal origins contrasts with data from the fossil record, and the taphonomic question of why animals were not preserved (if present) remains unresolved. Neoproterozoic environments demanding small, thin, body plans, and lower abundance/rarity in populations may have played a role. Considering environmental conditions, geochemical data suggest that animals evolved in a relatively low-oxygen ocean. Here, we present new analyses of sedimentary total organic carbon contents in shales suggesting that the Neoproterozoic ocean may also have had lower primary productivity-or at least lower quantities of organic carbon reaching the seafloor-compared with the Phanerozoic. Indeed, recent modeling efforts suggest that low primary productivity is an expected corollary of a low-O2 world. Combined with an inability to inhabit productive regions in a low-O2 ocean, earliest animal communities would likely have been more food limited than generally appreciated, impacting both ecosystem structure and organismal behavior. In light of this, we propose the "fire triangle" metaphor for environmental influences on early animal evolution. Moving toward consideration of all environmental aspects of the Cambrian radiation (fuel, heat, and oxidant) will ultimately lead to a more holistic view of the event.
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Affiliation(s)
- Erik A Sperling
- Department of Geological Sciences, Stanford University, 450 Serra Mall, Building 320, Stanford, CA 94305, USA
| | - Richard G Stockey
- Department of Geological Sciences, Stanford University, 450 Serra Mall, Building 320, Stanford, CA 94305, USA
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21
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Integrated records of environmental change and evolution challenge the Cambrian Explosion. Nat Ecol Evol 2019; 3:528-538. [DOI: 10.1038/s41559-019-0821-6] [Citation(s) in RCA: 120] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 01/22/2019] [Indexed: 11/08/2022]
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22
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Boag TH, Stockey RG, Elder LE, Hull PM, Sperling EA. Oxygen, temperature and the deep-marine stenothermal cradle of Ediacaran evolution. Proc Biol Sci 2018; 285:20181724. [PMID: 30963899 PMCID: PMC6304043 DOI: 10.1098/rspb.2018.1724] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 11/13/2018] [Indexed: 11/12/2022] Open
Abstract
Ediacaran fossils document the early evolution of complex megascopic life, contemporaneous with geochemical evidence for widespread marine anoxia. These data suggest early animals experienced frequent hypoxia. Research has thus focused on the concentration of molecular oxygen (O2) required by early animals, while also considering the impacts of climate. One model, the Cold Cradle hypothesis, proposed the Ediacaran biota originated in cold, shallow-water environments owing to increased O2 solubility. First, we demonstrate using principles of gas exchange that temperature does have a critical role in governing the bioavailability of O2-but in cooler water the supply of O2 is actually lower. Second, the fossil record suggests the Ediacara biota initially occur approximately 571 Ma in deep-water facies, before appearing in shelf environments approximately 555 Ma. We propose an ecophysiological underpinning for this pattern. By combining oceanographic data with new respirometry experiments we show that in the shallow mixed layer where seasonal temperatures fluctuate widely, thermal and partial pressure ( pO2) effects are highly synergistic. The result is that temperature change away from species-specific optima impairs tolerance to low pO2. We hypothesize that deep and particularly stenothermal (narrow temperature range) environments in the Ediacaran ocean were a physiological refuge from the synergistic effects of temperature and low pO2.
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Affiliation(s)
- Thomas H. Boag
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA
| | - Richard G. Stockey
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA
| | - Leanne E. Elder
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA
| | - Pincelli M. Hull
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA
| | - Erik A. Sperling
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA
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23
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Gold DA. Life in Changing Fluids: A Critical Appraisal of Swimming Animals Before the Cambrian. Integr Comp Biol 2018; 58:677-687. [DOI: 10.1093/icb/icy015] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Affiliation(s)
- David A Gold
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA
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24
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Cavalier-Smith T. Origin of animal multicellularity: precursors, causes, consequences-the choanoflagellate/sponge transition, neurogenesis and the Cambrian explosion. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2015.0476. [PMID: 27994119 PMCID: PMC5182410 DOI: 10.1098/rstb.2015.0476] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/05/2016] [Indexed: 02/07/2023] Open
Abstract
Evolving multicellularity is easy, especially in phototrophs and osmotrophs whose multicells feed like unicells. Evolving animals was much harder and unique; probably only one pathway via benthic ‘zoophytes’ with pelagic ciliated larvae allowed trophic continuity from phagocytic protozoa to gut-endowed animals. Choanoflagellate protozoa produced sponges. Converting sponge flask cells mediating larval settling to synaptically controlled nematocysts arguably made Cnidaria. I replace Haeckel's gastraea theory by a sponge/coelenterate/bilaterian pathway: Placozoa, hydrozoan diploblasty and ctenophores were secondary; stem anthozoan developmental mutations arguably independently generated coelomate bilateria and ctenophores. I emphasize animal origin's conceptual aspects (selective, developmental) related to feeding modes, cell structure, phylogeny of related protozoa, sequence evidence, ecology and palaeontology. Epithelia and connective tissue could evolve only by compensating for dramatically lower feeding efficiency that differentiation into non-choanocytes entails. Consequentially, larger bodies enabled filtering more water for bacterial food and harbouring photosynthetic bacteria, together adding more food than cell differentiation sacrificed. A hypothetical presponge of sessile triploblastic sheets (connective tissue sandwiched between two choanocyte epithelia) evolved oogamy through selection for larger dispersive ciliated larvae to accelerate benthic trophic competence and overgrowing protozoan competitors. Extinct Vendozoa might be elaborations of this organismal grade with choanocyte-bearing epithelia, before poriferan water channels and cnidarian gut/nematocysts/synapses evolved. This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.
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Lieberman BS, Kurkewicz R, Shinogle H, Kimmig J, MacGabhann BA. Disc-shaped fossils resembling porpitids or eldonids from the early Cambrian (Series 2: Stage 4) of western USA. PeerJ 2017; 5:e3312. [PMID: 28603667 PMCID: PMC5463991 DOI: 10.7717/peerj.3312] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 04/13/2017] [Indexed: 11/20/2022] Open
Abstract
The morphology and affinities of newly discovered disc-shaped, soft-bodied fossils from the early Cambrian (Series 2: Stage 4, Dyeran) Carrara Formation are discussed. These specimens show some similarity to the Ordovician DiscophyllumHall, 1847; traditionally this taxon had been treated as a fossil porpitid. However, recently it has instead been referred to as another clade, the eldonids, which includes the enigmatic EldoniaWalcott, 1911 that was originally described from the Cambrian Burgess Shale. The status of various Proterozoic and Phanerozoic taxa previously referred to porpitids and eldonids is also briefly considered. To help ascertain that the specimens were not dubio- or pseudofossils, elemental mapping using energy dispersive X-ray spectroscopy (EDS) was conducted. This, in conjunction with the morphology of the specimens, indicated that the fossils were not hematite, iron sulfide, pyrolusite, or other abiologic mineral precipitates. Instead, their status as biologic structures and thus actual fossils is supported. Enrichment in the element carbon, and also possibly to some extent the elements magnesium and iron, seems to be playing some role in the preservation process.
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Affiliation(s)
- Bruce S Lieberman
- Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, KS, United States of America.,Biodiversity Institute, University of Kansas, Lawrence, KS, United States of America
| | | | - Heather Shinogle
- Microscopy and Analytical Imaging Laboratory, University of Kansas, Lawrence, KS, United States of America
| | - Julien Kimmig
- Biodiversity Institute, University of Kansas, Lawrence, KS, United States of America
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Kraus YA, Markov AV. Gastrulation in Cnidaria: The key to an understanding of phylogeny or the chaos of secondary modifications? ACTA ACUST UNITED AC 2017. [DOI: 10.1134/s2079086417010029] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Cunningham JA, Liu AG, Bengtson S, Donoghue PCJ. The origin of animals: Can molecular clocks and the fossil record be reconciled? Bioessays 2016; 39:1-12. [PMID: 27918074 DOI: 10.1002/bies.201600120] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The evolutionary emergence of animals is one of the most significant episodes in the history of life, but its timing remains poorly constrained. Molecular clocks estimate that animals originated and began diversifying over 100 million years before the first definitive metazoan fossil evidence in the Cambrian. However, closer inspection reveals that clock estimates and the fossil record are less divergent than is often claimed. Modern clock analyses do not predict the presence of the crown-representatives of most animal phyla in the Neoproterozoic. Furthermore, despite challenges provided by incomplete preservation, a paucity of phylogenetically informative characters, and uncertain expectations of the anatomy of early animals, a number of Neoproterozoic fossils can reasonably be interpreted as metazoans. A considerable discrepancy remains, but much of this can be explained by the limited preservation potential of early metazoans and the difficulties associated with their identification in the fossil record. Critical assessment of both records may permit better resolution of the tempo and mode of early animal evolution.
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Affiliation(s)
- John A Cunningham
- School of Earth Sciences, University of Bristol, Bristol, UK.,Department of Palaeobiology and Nordic Center for Earth Evolution, Swedish Museum of Natural History, Stockholm, Sweden
| | - Alexander G Liu
- School of Earth Sciences, University of Bristol, Bristol, UK
| | - Stefan Bengtson
- Department of Palaeobiology and Nordic Center for Earth Evolution, Swedish Museum of Natural History, Stockholm, Sweden
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Abstract
Molecular clocks have become the method of choice to date the tree of life. A new study demonstrates that there are limits to their precision, which may only be overcome by improving our knowledge of the fossil record.
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Affiliation(s)
- Davide Pisani
- School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK; School of Earth Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.
| | - Alexander G Liu
- School of Earth Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
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Abstract
Animals make up only a small fraction of the eukaryotic tree of life, yet, from our vantage point as members of the animal kingdom, the evolution of the bewildering diversity of animal forms is endlessly fascinating. In the century following the publication of Darwin's Origin of Species, hypotheses regarding the evolution of the major branches of the animal kingdom - their relationships to each other and the evolution of their body plans - was based on a consideration of the morphological and developmental characteristics of the different animal groups. This morphology-based approach had many successes but important aspects of the evolutionary tree remained disputed. In the past three decades, molecular data, most obviously primary sequences of DNA and proteins, have provided an estimate of animal phylogeny largely independent of the morphological evolution we would ultimately like to understand. The molecular tree that has evolved over the past three decades has drastically altered our view of animal phylogeny and many aspects of the tree are no longer contentious. The focus of molecular studies on relationships between animal groups means, however, that the discipline has become somewhat divorced from the underlying biology and from the morphological characteristics whose evolution we aim to understand. Here, we consider what we currently know of animal phylogeny; what aspects we are still uncertain about and what our improved understanding of animal phylogeny can tell us about the evolution of the great diversity of animal life.
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Affiliation(s)
- Maximilian J Telford
- Department of Genetics, Evolution and Environment, University College London, WC1E 6BT, UK.
| | - Graham E Budd
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 75236 Uppsala, Sweden
| | - Hervé Philippe
- Centre de Théorisation et de Modélisation de la Biodiversité, Station d'Ecologie Expérimentale du CNRS, USR CNRS 2936 Moulis, 09200, France; Département de Biochimie, Centre Robert-Cedergren, Université de Montréal, Montréal, Québec, Canada
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Mendoza-Becerril MA, Maronna MM, Pacheco MLAF, Simões MG, Leme JM, Miranda LS, Morandini AC, Marques AC. An evolutionary comparative analysis of the medusozoan (Cnidaria) exoskeleton. Zool J Linn Soc 2016. [DOI: 10.1111/zoj.12415] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- María A. Mendoza-Becerril
- Department of Zoology; Institute of Biosciences; University of São Paulo; Rua do Matão, Trav. 14, 101 05508-090 São Paulo Brazil
| | - Maximiliano M. Maronna
- Department of Zoology; Institute of Biosciences; University of São Paulo; Rua do Matão, Trav. 14, 101 05508-090 São Paulo Brazil
| | - Mírian L. A. F. Pacheco
- Department of Biology; Federal University of Sao Carlos; Rodovia João Leme dos Santos - até km 104.000 Parque Reserva Fazenda Imperial 18052780 Sorocaba São Paulo Brazil
| | - Marcello G. Simões
- Department of Zoology; Laboratory of Paleozoology; São Paulo State University Botucatu; Jardim Santo Inácio (Rubião Junior) 18618970 Botucatu São Paulo Brazil
| | - Juliana M. Leme
- Department of Sedimentary and Environmental Geology; Institute of Geosciences; University of São Paulo; Rua do Lago, 562 05508-080 São Paulo Brazil
| | - Lucília S. Miranda
- Department of Zoology; Institute of Biosciences; University of São Paulo; Rua do Matão, Trav. 14, 101 05508-090 São Paulo Brazil
| | - André C. Morandini
- Department of Zoology; Institute of Biosciences; University of São Paulo; Rua do Matão, Trav. 14, 101 05508-090 São Paulo Brazil
| | - Antonio C. Marques
- Department of Zoology; Institute of Biosciences; University of São Paulo; Rua do Matão, Trav. 14, 101 05508-090 São Paulo Brazil
- Center for Marine Biology; University of São Paulo; Rodovia Manoel H. Do Rego km 131.5 CEP 11600-000 São Sebastião São Paulo Brazil
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Liebeskind BJ, Hillis DM, Zakon HH, Hofmann HA. Complex Homology and the Evolution of Nervous Systems. Trends Ecol Evol 2015; 31:127-135. [PMID: 26746806 DOI: 10.1016/j.tree.2015.12.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 12/01/2015] [Accepted: 12/02/2015] [Indexed: 02/07/2023]
Abstract
We examine the complex evolution of animal nervous systems and discuss the ramifications of this complexity for inferring the nature of early animals. Although reconstructing the origins of nervous systems remains a central challenge in biology, and the phenotypic complexity of early animals remains controversial, a compelling picture is emerging. We now know that the nervous system and other key animal innovations contain a large degree of homoplasy, at least on the molecular level. Conflicting hypotheses about early nervous system evolution are due primarily to differences in the interpretation of this homoplasy. We highlight the need for explicit discussion of assumptions and discuss the limitations of current approaches for inferring ancient phenotypic states.
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Affiliation(s)
- Benjamin J Liebeskind
- Center for Systems and Synthetic Biology, University of Texas, Austin, TX 78712, USA; Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA; Center for Computational Biology and Bioinformatics, University of Texas, Austin, TX 78712.
| | - David M Hillis
- Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA; Center for Computational Biology and Bioinformatics, University of Texas, Austin, TX 78712; Department of Integrative Biology, University of Texas, Austin, TX 78712, USA
| | - Harold H Zakon
- Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA; Center for Computational Biology and Bioinformatics, University of Texas, Austin, TX 78712; Department of Integrative Biology, University of Texas, Austin, TX 78712, USA; Department of Neuroscience, University of Texas, Austin, TX 78712, USA; Institute for Neuroscience, University of Texas, Austin, TX 78712, USA; Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Hans A Hofmann
- Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA; Center for Computational Biology and Bioinformatics, University of Texas, Austin, TX 78712; Department of Integrative Biology, University of Texas, Austin, TX 78712, USA; Department of Neuroscience, University of Texas, Austin, TX 78712, USA; Institute for Neuroscience, University of Texas, Austin, TX 78712, USA
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Raikova EV, Raikova OI. Nervous system immunohistochemistry of the parasitic cnidarian Polypodium hydriforme at its free-living stage. ZOOLOGY 2015; 119:143-152. [PMID: 26897553 DOI: 10.1016/j.zool.2015.11.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 11/09/2015] [Accepted: 11/30/2015] [Indexed: 10/22/2022]
Abstract
Polypodium hydriforme, the only species in Polypodiozoa, which is currently considered a class of Cnidaria, and likely a sister group to Medusozoa (together with Myxozoa), is a cnidarian adapted to intracellular parasitism inside sturgeon oocytes. Free-living P. hydriforme lives on river bottoms; it walks on supporting tentacles and uses sensory tentacles to capture food and bring it to the mouth. The nervous system of free-living P. hydriforme was studied by confocal microscopy and immunohistochemistry using antibodies to FMRF-amide and α-tubulin combined with phalloidin-staining of F-actin fibres. A sensory FMRF-amide immunoreactive (IR) nerve net and an α-tubulin IR nerve net have been identified. The FMRF-amide IR nerve net underlies the epidermis along the tentacles and around the mouth; it consists of neurites emanating from epidermal sensory cells and basiepidermal ganglion cells, and it connects with cnidocytes. A deeper-lying α-tubulin IR nerve net occurs only in tentacles and looks like chains of different-sized beads crossing the mesoglea and entwining muscles. Anti-α-tubulin staining also reveals microtubules in muscle cells following the longitudinal muscle fibres or the thin circular F-actin fibres of the tentacles. Cnidocytes in the tentacles are embedded in a regular hexagonal non-neural network formed by the tubulin IR cytoskeleton of epidermal cells. Cnidocils of the cnidocytes around the mouth and in walking tentacles are identical, but those in sensory tentacles differ in length and width. The possible homology of the tubulin IR nerve net with motor nerve nets of cnidarians is discussed. The absence of a classic nerve ring around the mouth and the lack of specialised sense organs are considered to be plesiomorphic characters for Cnidaria.
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Affiliation(s)
- Ekaterina V Raikova
- Institute of Cytology, Russian Academy of Sciences, 4, Tikhoretsky ave., 194064 St. Petersburg, Russia
| | - Olga I Raikova
- Zoological Institute, Russian Academy of Sciences, 1, Universitetskaya nab., 199034 St. Petersburg, Russia; Biological Faculty, Saint Petersburg State University, 7-9, Universitetskaya nab., 199034 St. Petersburg, Russia.
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33
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Budd GE, Jensen S. The origin of the animals and a 'Savannah' hypothesis for early bilaterian evolution. Biol Rev Camb Philos Soc 2015; 92:446-473. [PMID: 26588818 DOI: 10.1111/brv.12239] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 10/12/2015] [Accepted: 10/21/2015] [Indexed: 12/14/2022]
Abstract
The earliest evolution of the animals remains a taxing biological problem, as all extant clades are highly derived and the fossil record is not usually considered to be helpful. The rise of the bilaterian animals recorded in the fossil record, commonly known as the 'Cambrian explosion', is one of the most significant moments in evolutionary history, and was an event that transformed first marine and then terrestrial environments. We review the phylogeny of early animals and other opisthokonts, and the affinities of the earliest large complex fossils, the so-called 'Ediacaran' taxa. We conclude, based on a variety of lines of evidence, that their affinities most likely lie in various stem groups to large metazoan groupings; a new grouping, the Apoikozoa, is erected to encompass Metazoa and Choanoflagellata. The earliest reasonable fossil evidence for total-group bilaterians comes from undisputed complex trace fossils that are younger than about 560 Ma, and these diversify greatly as the Ediacaran-Cambrian boundary is crossed a few million years later. It is generally considered that as the bilaterians diversified after this time, their burrowing behaviour destroyed the cyanobacterial mat-dominated substrates that the enigmatic Ediacaran taxa were associated with, the so-called 'Cambrian substrate revolution', leading to the loss of almost all Ediacara-aspect diversity in the Cambrian. Why, though, did the energetically expensive and functionally complex burrowing mode of life so typical of later bilaterians arise? Here we propose a much more positive relationship between late-Ediacaran ecologies and the rise of the bilaterians, with the largely static Ediacaran taxa acting as points of concentration of organic matter both above and below the sediment surface. The breaking of the uniformity of organic carbon availability would have signalled a decisive shift away from the essentially static and monotonous earlier Ediacaran world into the dynamic and burrowing world of the Cambrian. The Ediacaran biota thus played an enabling role in bilaterian evolution similar to that proposed for the Savannah environment for human evolution and bipedality. Rather than being obliterated by the rise of the bilaterians, the subtle remnants of Ediacara-style taxa within the Cambrian suggest that they remained significant components of Phanerozoic communities, even though at some point their enabling role for bilaterian evolution was presumably taken over by bilaterians or other metazoans. Bilaterian evolution was thus an essentially benthic event that only later impacted the planktonic environment and the style of organic export to the sea floor.
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Affiliation(s)
- Graham E Budd
- Palaeobiology Programme, Department of Earth Sciences, Uppsala University, Villavägen 16, SE 752 40, Uppsala, Sweden
| | - Sören Jensen
- Área de Paleontología, Facultad de Ciencias, Universidad de Extremadura, 06006, Badajoz, Spain
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dos Reis M, Thawornwattana Y, Angelis K, Telford MJ, Donoghue PCJ, Yang Z. Uncertainty in the Timing of Origin of Animals and the Limits of Precision in Molecular Timescales. Curr Biol 2015; 25:2939-50. [PMID: 26603774 PMCID: PMC4651906 DOI: 10.1016/j.cub.2015.09.066] [Citation(s) in RCA: 247] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 09/20/2015] [Accepted: 09/22/2015] [Indexed: 11/24/2022]
Abstract
The timing of divergences among metazoan lineages is integral to understanding the processes of animal evolution, placing the biological events of species divergences into the correct geological timeframe. Recent fossil discoveries and molecular clock dating studies have suggested a divergence of bilaterian phyla >100 million years before the Cambrian, when the first definite crown-bilaterian fossils occur. Most previous molecular clock dating studies, however, have suffered from limited data and biases in methodologies, and virtually all have failed to acknowledge the large uncertainties associated with the fossil record of early animals, leading to inconsistent estimates among studies. Here we use an unprecedented amount of molecular data, combined with four fossil calibration strategies (reflecting disparate and controversial interpretations of the metazoan fossil record) to obtain Bayesian estimates of metazoan divergence times. Our results indicate that the uncertain nature of ancient fossils and violations of the molecular clock impose a limit on the precision that can be achieved in estimates of ancient molecular timescales. For example, although we can assert that crown Metazoa originated during the Cryogenian (with most crown-bilaterian phyla diversifying during the Ediacaran), it is not possible with current data to pinpoint the divergence events with sufficient accuracy to test for correlations between geological and biological events in the history of animals. Although a Cryogenian origin of crown Metazoa agrees with current geological interpretations, the divergence dates of the bilaterians remain controversial. Thus, attempts to build evolutionary narratives of early animal evolution based on molecular clock timescales appear to be premature. Molecular clock analysis indicates an ancient origin of animals in the Cryogenian Diversification into animal phyla occurred in the Ediacaran, before the Cambrian Uncertainties in the fossil record and the molecular clock affect time estimates A precise timeline of animal evolution cannot be obtained with current methods
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Miranda LS, Collins AG, Marques AC. Is Haootia quadriformis related to extant Staurozoa (Cnidaria)? Evidence from the muscular system reconsidered. Proc Biol Sci 2015; 282:20142396. [PMID: 25673674 DOI: 10.1098/rspb.2014.2396] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- L S Miranda
- Instituto de Biociências, Departamento de Zoologia, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - A G Collins
- National Systematics Laboratory, National Marine Fisheries Service (NMFS), National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | - A C Marques
- Instituto de Biociências, Departamento de Zoologia, Universidade de São Paulo, São Paulo, São Paulo, Brazil Centro de Biologia Marinha, Universidade de São Paulo, São Sebastião, São Paulo, Brazil
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36
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Liu AG, Matthews JJ, Menon LR, McIlroy D, Brasier MD. The arrangement of possible muscle fibres in the Ediacaran taxon Haootia quadriformis. Proc Biol Sci 2015; 282:20142949. [PMID: 25673688 DOI: 10.1098/rspb.2014.2949] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Alexander G Liu
- School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Jack J Matthews
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - Latha R Menon
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - Duncan McIlroy
- Department of Earth Sciences, Memorial University of Newfoundland, 300 Prince Philip Drive, St John's, Newfoundland and Labrador, Canada A1B 3X5
| | - Martin D Brasier
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK Department of Earth Sciences, Memorial University of Newfoundland, 300 Prince Philip Drive, St John's, Newfoundland and Labrador, Canada A1B 3X5
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