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Smith MR, Long EJ, Dhungana A, Dobson KJ, Yang J, Zhang X. Organ systems of a Cambrian euarthropod larva. Nature 2024:10.1038/s41586-024-07756-8. [PMID: 39085610 DOI: 10.1038/s41586-024-07756-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 06/26/2024] [Indexed: 08/02/2024]
Abstract
The Cambrian radiation of euarthropods can be attributed to an adaptable body plan. Sophisticated brains and specialized feeding appendages, which are elaborations of serially repeated organ systems and jointed appendages, underpin the dominance of Euarthropoda in a broad suite of ecological settings. The origin of the euarthropod body plan from a grade of vermiform taxa with hydrostatic lobopodous appendages ('lobopodian worms')1,2 is founded on data from Burgess Shale-type fossils. However, the compaction associated with such preservation obscures internal anatomy3-6. Phosphatized microfossils provide a complementary three-dimensional perspective on early crown group euarthropods7, but few lobopodians8,9. Here we describe the internal and external anatomy of a three-dimensionally preserved euarthropod larva with lobopods, midgut glands and a sophisticated head. The architecture of the nervous system informs the early configuration of the euarthropod brain and its associated appendages and sensory organs, clarifying homologies across Panarthropoda. The deep evolutionary position of Youti yuanshi gen. et sp. nov. informs the sequence of character acquisition during arthropod evolution, demonstrating a deep origin of sophisticated haemolymph circulatory systems, and illuminating the internal anatomical changes that propelled the rise and diversification of this enduringly successful group.
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Affiliation(s)
- Martin R Smith
- Department of Earth Sciences, Durham University, Durham, UK.
| | - Emma J Long
- Department of Earth Sciences, Durham University, Durham, UK
- Science Group, Natural History Museum, London, UK
- Centre for Ecology and Conservation, University of Exeter, Cornwall, UK
| | | | - Katherine J Dobson
- Department of Earth Sciences, Durham University, Durham, UK
- Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow, UK
- Department of Chemical and Process Engineering, University of Strathclyde, Glasgow, UK
| | - Jie Yang
- Institute of Palaeontology, Yunnan University, Chenggong, Kunming, China
| | - Xiguang Zhang
- Institute of Palaeontology, Yunnan University, Chenggong, Kunming, China
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2
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Smith FW, Game M, Mapalo MA, Chavarria RA, Harrison TR, Janssen R. Developmental and genomic insight into the origin of the tardigrade body plan. Evol Dev 2024; 26:e12457. [PMID: 37721221 DOI: 10.1111/ede.12457] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 08/11/2023] [Accepted: 08/29/2023] [Indexed: 09/19/2023]
Abstract
Tardigrada is an ancient lineage of miniaturized animals. As an outgroup of the well-studied Arthropoda and Onychophora, studies of tardigrades hold the potential to reveal important insights into body plan evolution in Panarthropoda. Previous studies have revealed interesting facets of tardigrade development and genomics that suggest that a highly compact body plan is a derived condition of this lineage, rather than it representing an ancestral state of Panarthropoda. This conclusion was based on studies of several species from Eutardigrada. We review these studies and expand on them by analyzing the publicly available genome and transcriptome assemblies of Echiniscus testudo, a representative of Heterotardigrada. These new analyses allow us to phylogenetically reconstruct important features of genome evolution in Tardigrada. We use available data from tardigrades to interrogate several recent models of body plan evolution in Panarthropoda. Although anterior segments of panarthropods are highly diverse in terms of anatomy and development, both within individuals and between species, we conclude that a simple one-to-one alignment of anterior segments across Panarthropoda is the best available model of segmental homology. In addition to providing important insight into body plan diversification within Panarthropoda, we speculate that studies of tardigrades may reveal generalizable pathways to miniaturization.
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Affiliation(s)
- Frank W Smith
- Biology Department, University of North Florida, Jacksonville, Florida, USA
| | - Mandy Game
- Biology Department, University of North Florida, Jacksonville, Florida, USA
| | - Marc A Mapalo
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Raul A Chavarria
- Biology Department, University of North Florida, Jacksonville, Florida, USA
| | - Taylor R Harrison
- Biology Department, University of North Florida, Jacksonville, Florida, USA
| | - Ralf Janssen
- Department of Earth Sciences, Palaeobiology, Uppsala University, Uppsala, Sweden
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3
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Park TYS. Trilobite hypostome as a fusion of anterior sclerite and labrum. ARTHROPOD STRUCTURE & DEVELOPMENT 2023; 77:101308. [PMID: 37832459 DOI: 10.1016/j.asd.2023.101308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 09/13/2023] [Accepted: 09/20/2023] [Indexed: 10/15/2023]
Abstract
The trilobite hypostome is a biomineralized ventral plate that covers the mouth, but its evolutionary origin remains controversial. The labrum is a lobe-like structure that can take on variety of shapes in front of the mouth in arthropods, while the anterior sclerite refers to a cuticular plate articulated to the anterior margin of the head in some Cambrian arthropods. Here I present a perspective that views the trilobite hypostome as a fusion of the anterior sclerite and the labrum based on anatomical, topological, and developmental evidence. According to this perspective, the anterior lobe of the hypostome originated from the anterior sclerite, while the posterior lobe reflects a remnant of the sclerotized cover of the labrum. The convex anterior lobe housed the root of the eye stalks, represented by the palpebral ridges and the hypostomal wing, and the posterior lobe occasionally developed a pair of posterolateral extensions, as do the labra. The position of the antennal insertion was located in front of the posterior lobe, displaying a similar topology to the Cambrian arthropods with the labrum. The hypostome was present in many artiopodans except for the Conciliterga, in which the anterior sclerite was separate from the labrum.
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Affiliation(s)
- Tae-Yoon S Park
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon, 21990, Republic of Korea; Polar Science, University of Science & Technology, 217 Gajeong-ro, Yuseong-gu, 34113, Daejeon, Republic of Korea.
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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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Posnien N, Hunnekuhl VS, Bucher G. Gene expression mapping of the neuroectoderm across phyla - conservation and divergence of early brain anlagen between insects and vertebrates. eLife 2023; 12:e92242. [PMID: 37750868 PMCID: PMC10522337 DOI: 10.7554/elife.92242] [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: 09/07/2023] [Accepted: 09/18/2023] [Indexed: 09/27/2023] Open
Abstract
Gene expression has been employed for homologizing body regions across bilateria. The molecular comparison of vertebrate and fly brains has led to a number of disputed homology hypotheses. Data from the fly Drosophila melanogaster have recently been complemented by extensive data from the red flour beetle Tribolium castaneum with its more insect-typical development. In this review, we revisit the molecular mapping of the neuroectoderm of insects and vertebrates to reconsider homology hypotheses. We claim that the protocerebrum is non-segmental and homologous to the vertebrate fore- and midbrain. The boundary between antennal and ocular regions correspond to the vertebrate mid-hindbrain boundary while the deutocerebrum represents the anterior-most ganglion with serial homology to the trunk. The insect head placode is shares common embryonic origin with the vertebrate adenohypophyseal placode. Intriguingly, vertebrate eyes develop from a different region compared to the insect compound eyes calling organ homology into question. Finally, we suggest a molecular re-definition of the classic concepts of archi- and prosocerebrum.
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Affiliation(s)
- Nico Posnien
- Department of Developmental Biology, Johann-Friedrich-Blumenbach Institute, University GoettingenGöttingenGermany
| | - Vera S Hunnekuhl
- Department of Evolutionary Developmental Genetics, Johann-Friedrich-Blumenbach Institute, University of GöttingenGöttingenGermany
| | - Gregor Bucher
- Department of Evolutionary Developmental Genetics, Johann-Friedrich-Blumenbach Institute, University of GöttingenGöttingenGermany
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Budd GE, Mayer G, Janssen R, Eriksson BJ. Comment on "The lower Cambrian lobopodian Cardiodictyon resolves the origin of euarthropod brains". Science 2023; 380:eadg1412. [PMID: 37384683 DOI: 10.1126/science.adg1412] [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: 12/07/2022] [Accepted: 04/26/2023] [Indexed: 07/01/2023]
Abstract
Strausfeld et al. (Report, 24 Nov 2022, p. 905) claim that Cambrian fossilized nervous tissue supports the interpretation that the ancestral panarthropod brain was tripartite and unsegmented. We argue that this conclusion is unsupported, and developmental data from living onychophorans contradict it.
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Affiliation(s)
- Graham E Budd
- Department of Earth Sciences, Palaeobiology, Uppsala University, 752 36, Uppsala, Sweden
| | - Georg Mayer
- Department of Zoology, Institute of Biology, University of Kassel, 34132, Kassel, Germany
| | - Ralf Janssen
- Department of Earth Sciences, Palaeobiology, Uppsala University, 752 36, Uppsala, Sweden
| | - B Joakim Eriksson
- Department für Neurowissenschaften und Entwicklungsbiologie, Universität Wien, A-1030, Vienna, Austria
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Strausfeld NJ, Hou X, Sayre ME, Hirth F. Response to Comment on "The lower Cambrian lobopodian Cardiodictyon resolves the origin of euarthropod brains". Science 2023; 380:eadg6051. [PMID: 37384690 DOI: 10.1126/science.adg6051] [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: 02/09/2023] [Accepted: 04/26/2023] [Indexed: 07/01/2023]
Abstract
Budd et al. challenge the identity of neural traces reported for the Cambrian lobopodian Cardiodictyon catenulum. Their argumentation is unsupported, as are objections with reference to living Onychophora that misinterpret established genomic, genetic, developmental, and neuroanatomical evidence. Instead, phylogenetic data corroborate the finding that the ancestral panarthropod head and brain is unsegmented, as in C. catenulum.
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Affiliation(s)
| | - Xianguang Hou
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, China
| | - Marcel E Sayre
- Lund University, Lund Vision Group, Department of Biology, Lund, Sweden & Macquarie University, Department of Biological Sciences, Sydney, Australia
| | - Frank Hirth
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 9RT, UK
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Schuster HC, Hirth F. Phylogenetic tracing of midbrain-specific regulatory sequences suggests single origin of eubilaterian brains. SCIENCE ADVANCES 2023; 9:eade8259. [PMID: 37224241 PMCID: PMC10208574 DOI: 10.1126/sciadv.ade8259] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Accepted: 04/18/2023] [Indexed: 05/26/2023]
Abstract
Conserved cis-regulatory elements (CREs) control Engrailed-, Pax2-, and dachshund-related gene expression networks directing the formation and function of corresponding midbrain circuits in arthropods and vertebrates. Polarized outgroup analyses of 31 sequenced metazoan genomes representing all animal clades reveal the emergence of Pax2- and dachshund-related CRE-like sequences in anthozoan Cnidaria. The full complement, including Engrailed-related CRE-like sequences, is only detectable in spiralians, ecdysozoans, and chordates that have a brain; they exhibit comparable genomic locations and extensive nucleotide identities that reveal the presence of a conserved core domain, all of which are absent in non-neural genes and, together, distinguish them from randomly assembled sequences. Their presence concurs with a genetic boundary separating the rostral from caudal nervous systems, demonstrated for the metameric brains of annelids, arthropods, and chordates and the asegmental cycloneuralian and urochordate brain. These findings suggest that gene regulatory networks for midbrain circuit formation evolved within the lineage that led to the common ancestor of protostomes and deuterostomes.
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Affiliation(s)
- Helen C. Schuster
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, and Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
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Aria C, Vannier J, Park TYS, Gaines RR. Interpreting fossilized nervous tissues. Bioessays 2023; 45:e2200167. [PMID: 36693795 DOI: 10.1002/bies.202200167] [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: 08/25/2022] [Revised: 01/09/2023] [Accepted: 01/10/2023] [Indexed: 01/26/2023]
Abstract
Paleoneuranatomy is an emerging subfield of paleontological research with great potential for the study of evolution. However, the interpretation of fossilized nervous tissues is a difficult task and presently lacks a rigorous methodology. We critically review here cases of neural tissue preservation reported in Cambrian arthropods, following a set of fundamental paleontological criteria for their recognition. These criteria are based on a variety of taphonomic parameters and account for morphoanatomical complexity. Application of these criteria shows that firm evidence for fossilized nervous tissues is less abundant and detailed than previously reported, and we synthesize here evidence that has stronger support. We argue that the vascular system, and in particular its lacunae, may be central to the understanding of many of the fossilized peri-intestinal features known across Cambrian arthropods. In conclusion, our results suggest the need for caution in the interpretation of evidence for fossilized neural tissue, which will increase the accuracy of evolutionary scenarios. Also see the video abstract here: https://youtu.be/2_JlQepRTb0.
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Affiliation(s)
- Cédric Aria
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.,Department of Natural History, Royal Ontario Museum, Toronto, Ontario, Canada.,Shaanxi Key Laboratory of Early Life and Environments, State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an, P. R. China
| | - Jean Vannier
- Université de Lyon, Université Lyon 1, ENS de Lyon, CNRS, UMR 5276 LGL-TPE, Bâtiment Géode, Villeurbanne, France
| | - Tae-Yoon S Park
- Division of Earth Sciences, Korea Polar Research Institute, Incheon, Republic of Korea
| | - Robert R Gaines
- Geology Department, Pomona College, Claremont, California, USA
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Briggs DEG, Parry LA. Putting heads together. Science 2022; 378:831-832. [DOI: 10.1126/science.add7372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cambrian fossils reveal ancestry of the segmented brain in arthropods
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Affiliation(s)
- Derek E. G. Briggs
- Department of Earth and Planetary Sciences, Yale University, New Haven, CT, USA
- Yale Peabody Museum of Natural History, Yale University, New Haven, CT, USA
| | - Luke A. Parry
- Department of Earth Sciences, University of Oxford, Oxford, UK
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