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Akat Çömden E, Yenmiş M, Kytyr D, Ayaz D, Bayrakci Y. A study on the vertebral column of the dice snake Natrix tessellata (Serpentes, Natricidae) from Denizli (western Anatolia, Turkey). Anat Rec (Hoboken) 2024; 307:1930-1942. [PMID: 37746926 DOI: 10.1002/ar.25328] [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: 05/19/2023] [Revised: 08/17/2023] [Accepted: 08/21/2023] [Indexed: 09/26/2023]
Abstract
The vertebral anatomy of snakes has attracted the attention of researchers for decades and numerous studies have been made for extinct and extant species. The present study investigated the morphological variations in vertebral structure among different vertebral regions in the dice snake Natrix tessellata, and provides a detailed anatomical and microstructural description of the vertebral column. Vertebrae were analyzed and compared using x-ray imaging, scanning electron microscopy, micro-computed tomography, and histological techniques. The vertebral column of N. tessellata is divided into three regions: precloacal, cloacal, and caudal. Unlike in many other tetrapods and snakes, the atlas of N. tessellata does not form a complete ring. It has a flat and roughly trilobate shape with a prominent middle lobe. The axis has two hypapophyses. The anterior precloacal region of the vertebral column has longer and more paddle-shaped hypapophyses, distinguishing it from the posterior and mid-trunk vertebrae. The anterior cloacal vertebrae have a short hypapophysis rather than a hemal keel, and the lymphapophysis extends outward, curving slightly. The cotyle and condyle of the caudal vertebrae exhibited a closer resemblance to a rounded shape, while the pleurapophysis extended ventrolaterally and curved ventrally near its distal end. Paired hemapophyses were present at the posterior-most point of the centrum instead of a hypapophysis. In light of previous fossil findings, our anatomical comparison of the vertebral and transverse processes indicates that the extant Natrix has a more flexible and less rigid spine than its ancestors. Overall, the vertebral differences among snake anatomical regions or taxa are a testament to the remarkable diversity and adaptability of these fascinating reptiles.
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Affiliation(s)
- Esra Akat Çömden
- Science Faculty, Biology Department, Zoology Section, Ege University, Bornova, Izmir, Turkey
| | - Melodi Yenmiş
- Science Faculty, Biology Department, Zoology Section, Ege University, Bornova, Izmir, Turkey
| | - Daniel Kytyr
- Institute of Theoretical and Applied Mechanics, Czech Academy of Sciences, Prague 9, Czech Republic
| | - Dinçer Ayaz
- Science Faculty, Biology Department, Zoology Section, Ege University, Bornova, Izmir, Turkey
| | - Yusuf Bayrakci
- Science Faculty, Biology Department, Zoology Section, Ege University, Bornova, Izmir, Turkey
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Hampton PM, Meik JM. Regionalization of the vertebral column and its correlation with heart position in snakes: Implications for evolutionary pathways and morphological diversification. Evol Dev 2024; 26:e12460. [PMID: 37804483 DOI: 10.1111/ede.12460] [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: 04/17/2023] [Revised: 08/17/2023] [Accepted: 09/26/2023] [Indexed: 10/09/2023]
Abstract
Spinal regionalization has important implications for the evolution of vertebrate body plans. We determined the variation in the number and morphology of vertebrae across the vertebral column (i.e., vertebral formula) for 63 snake species representing 13 families using intracolumnar variation in vertebral shape. Vertebral counts were used to determine the position of the heart, pylorus, and left kidney for each species. Across all species we observed a conspicuous midthoracic transition in vertebral shape, indicating four developmental domains of the precloacal vertebral column (cervical, anterior thoracic, posterior thoracic, and lumbar). Using phylogenetic analyses, the boundary between the anterior and posterior thoracic vertebrae was correlated with heart position. No associations were found between shifts in morphology of the vertebral column and either the pylorus or left kidney. We observed that among taxa, the number of preapex and postapex vertebrae could change independently from one another and from changes in the total number of precloacal vertebrae. Ancestral state reconstruction of the preapex and postapex vertebrae illustrated several evolutionary pathways by which diversity in the vertebral column and heart position have been attained. In addition, no conspicuous pattern was observed among the heart, pylorus, or kidney indicating that their relative positions to each other evolve independently. We conclude that snakes exhibit four morphologically distinct regions of the vertebral column. We discuss the implications of the forebody and hindbody vertebral formula on the morphological diversification of snakes.
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Affiliation(s)
- Paul M Hampton
- Department of Biology, Colorado Mesa University, Grand Junction, Colorado, USA
| | - Jesse M Meik
- Department of Biological Sciences, Tarleton State University, Stephenville, Texas, USA
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Ludington AJ, Hammond JM, Breen J, Deveson IW, Sanders KL. New chromosome-scale genomes provide insights into marine adaptations of sea snakes (Hydrophis: Elapidae). BMC Biol 2023; 21:284. [PMID: 38066641 PMCID: PMC10709897 DOI: 10.1186/s12915-023-01772-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 11/20/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND Sea snakes underwent a complete transition from land to sea within the last ~ 15 million years, yet they remain a conspicuous gap in molecular studies of marine adaptation in vertebrates. RESULTS Here, we generate four new annotated sea snake genomes, three of these at chromosome-scale (Hydrophis major, H. ornatus and H. curtus), and perform detailed comparative genomic analyses of sea snakes and their closest terrestrial relatives. Phylogenomic analyses highlight the possibility of near-simultaneous speciation at the root of Hydrophis, and synteny maps show intra-chromosomal variations that will be important targets for future adaptation and speciation genomic studies of this system. We then used a strict screen for positive selection in sea snakes (against a background of seven terrestrial snake genomes) to identify genes over-represented in hypoxia adaptation, sensory perception, immune response and morphological development. CONCLUSIONS We provide the best reference genomes currently available for the prolific and medically important elapid snake radiation. Our analyses highlight the phylogenetic complexity and conserved genome structure within Hydrophis. Positively selected marine-associated genes provide promising candidates for future, functional studies linking genetic signatures to the marine phenotypes of sea snakes and other vertebrates.
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Affiliation(s)
- Alastair J Ludington
- School of Biological Sciences, The University of Adelaide, Adelaide, SA, 5005, Australia.
| | - Jillian M Hammond
- Genomics and Inherited Disease Program, Garvan Institute of Medical Research, Sydney, NSW, Australia
- Centre for Population Genomics, Garvan Institute of Medical Research and Murdoch Children's Research Institute, Darlinghurst, Australia
| | - James Breen
- Indigenous Genomics, Telethon Kids Institute, Adelaide, Australia
- John Curtin School of Medical Research, College of Health & Medicine, Australian National University, Canberra, Australia
| | - Ira W Deveson
- Genomics and Inherited Disease Program, Garvan Institute of Medical Research, Sydney, NSW, Australia
- Centre for Population Genomics, Garvan Institute of Medical Research and Murdoch Children's Research Institute, Darlinghurst, Australia
- Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Kate L Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, SA, 5005, Australia.
- The South Australian Museum, Adelaide, Australia.
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Sherratt E, Nash-Hahn T, Nankivell JH, Rasmussen AR, Hampton PM, Sanders KL. Macroevolution in axial morphospace: innovations accompanying the transition to marine environments in elapid snakes. ROYAL SOCIETY OPEN SCIENCE 2022; 9:221087. [PMID: 36569233 PMCID: PMC9768463 DOI: 10.1098/rsos.221087] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 11/29/2022] [Indexed: 06/17/2023]
Abstract
Sea snakes in the Hydrophis-Microcephalophis clade (Elapidae) show exceptional body shape variation along a continuum from similar forebody and hindbody girths, to dramatically reduced girths of the forebody relative to hindbody. The latter is associated with specializations on burrowing prey. This variation underpins high sympatric diversity and species richness and is not shared by other marine (or terrestrial) snakes. Here, we examined a hypothesis that macroevolutionary changes in axial development contribute to the propensity, at clade level, for body shape change. We quantified variation in the number and size of vertebrae in two body regions (pre- and post-apex of the heart) for approximately 94 terrestrial and marine elapids. We found Hydrophis-Microcephalophis exhibit increased rates of vertebral evolution in the pre- versus post-apex regions compared to all other Australasian elapids. Unlike other marine and terrestrial elapids, axial elongation in Hydrophis-Microcephalophis occurs via the preferential addition of vertebrae pre-heart apex, which is the region that undergoes concomitant shifts in vertebral number and size during transitions along the relative fore- to hindbody girth axis. We suggest that this macroevolutionary developmental change has potentially acted as a key innovation in Hydrophis-Microcephalophis by facilitating novel (especially burrowing) prey specializations that are not shared with other marine snakes.
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Affiliation(s)
- Emma Sherratt
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
| | - Tamika Nash-Hahn
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - James H. Nankivell
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
| | - Arne R. Rasmussen
- The Royal Danish Academy, Institute of Conservation, 1435 Copenhagen, Denmark
| | - Paul M. Hampton
- Department of Biology, Colorado Mesa University, Grand Junction, CO 81501, USA
| | - Kate L. Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
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