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Comparison of the lower jaw and maxilla of Homoroselaps lacteus, Atractaspis aterrima, and Atractaspis irregularis

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Comparison of the lower jaw and maxilla of Homoroselaps lacteus, Atractaspis aterrima, and Atractaspis irregularis
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Regan Saltzer
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CT scans of three snake species from Africa were segmented to compare the lower jaw and maxilla. The CT scans were put into Avizo software, which allows for the visualization of 3D models. Screenshots were taken of the bones in various planes of view to anatomically describe them. This was then compared to other literature about the anatomy and behavior of burrowing asps to make predictions about behavior despite their elusive burrowing habits. The jaws of Atractaspis aterrima and Atractaspis irregularis were very similar with thin, complicated dentary and compound bones containing several projections. Homoroselaps lacteus in comparison had thick, less complicated dentary and compound bones. These differences could be explained by differences in burrowing habits, feeding behavior, or in venom delivery systems. This has yet to be determined conclusively until further research is conducted.
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Collected for SUNY Oswego Institutional Repository by the online self-submittal tool. Submitted by Regan Saltzer.

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Due to their burrowing behavior, there is little information available on the ecological traits of burrowing asps. In this study, the lower jaw and maxilla of three venomous African species of burrowing asps were segmented and described; Homoroselaps lacteus , Atractaspis aterrima , and Atractaspis irregularis, commonly called the Sotted Harlequin snake, Slender Burrowing Asp or Mole Viper, and Variable Burrowing Asp. It is beneficial to look at the anatomy of these species because it can be used to make predictions about the behavior of these snakes. Looking at the dentary bones could help to learn more about eating or burrowing behavior (Shine, 2006). This could also be useful in comparing these to other snake species. A complete morphological analysis was last provided by (Gans, 2008) but only Homoroselaps lacteus was shown and not all bones were looked at individually. While Atractaspis species have not had a complete morphological analysis, there is generally more information about this family of snakes compared to Homoroselaps . Regan Saltzer SUNY Oswego Department of Biological Sciences Comparison of the lower jaw and maxilla of Homoroselaps lacteus , Atractaspis aterrima , and Atractaspis irregularis Introduction: Methods: CT scans of three snake species from Africa were segmented to compare the lower jaw and maxilla. The CT scans were put into Avizo software, which allows for the visualization of 3D models. These scans were segmented to show each individual bone of the lower jaw and the maxilla bone. Following segmentation, the bones were labeled by comparing them to other literature on the anatomy of snakes close to these on the phylogenetic trees (Gans, 2008; Pyron 2014). Screenshots were taken of the bones in lateral, dorsal, ventral, anterior, and posterior planes of view to compare the anatomy of the snakes. Anatomical terms and definitions that were used to describe the dentary were based on those of Gomez, (2011) and Comeaux (2010). This was used in relation to literature on burrowing asps to determine variation that could possibly explain behaviors otherwise not observable due to the burrowing habits of these species. I thank OSRP and NSF for funding. I thank Dr. Olori for her advisement on this research. I thank my fellow lab students for their helpful feedback. I thank the University of Florida; J. Mueller from the Museum for Naturkunde, Berlin Germany; and J. Maisano at Digimorph, at the University of Texas at Austin for providing the CT scans. Results: The jaws of Atractaspis aterrima and Atractaspis irregularis are very similar which makes sense given that both snakes are within the Atractaspis genus. These species have thin, complicated dentary and compound bones with several projections. Homoroselaps has thicker compound and dentary bones that are not as irregular and asymmetrical. This could possibly be explained by a difference in diet or burrowing behavior. It is possible that Atractaspis and Homoroselap s have a difference in size of prey, burrowing techniques, or venom delivery systems but that has yet to be determined conclusively. The next step of this research would be to completely segment the skull of all three species to further explore possible variation of ecological traits associated with anatomical structure. Conclusions: One possible reason Homoroselaps lacteus has a thicker compound and dentary bone could be due to variation in digging stress that would require them to be able to put in more force in order to burrow properly (Gans 2006). Atractaspis has a front fanged venom delivery system and a unique side strike ability that could give them the advantage of striking their prey to envenomate them, opposed to Homoroselaps which could be less venomous. Therefore Homoroselaps would not be able to simply strike prey and would reply on thicker jaw bones to have the crushing force needed to kill its prey. (Terrat 2013). Atractaspis could afford to have thinner, more delicate bones in the jaw because if this species has a stronger venom system, it would be able to simply strike its prey and wait for it to become paralyzed or die instead of relying on strong biting force like Homoroselaps . References: Acknowledgments: Figure 2. Left Lateral view of Homoroselaps lacteus lower jaw and maxilla . Figure 4. Left Lateral view of Atractaspis Irregularis lower jaw and maxilla. Figure 3. Left Lateral view of Atractapis aterrima lower jaw and maxilla. Comeaux, S. R., Olori, J. C., Bell, C. J. Cranial osteology and preliminary phylogenetic assessment of Plectrurus aureus Beddome, 1880 (Squamata: Serpentes: Uropeltidae), Zoological Journal of the Linnean Society , 160, (1), 2010, pp. 118 138. Gans, C., Gaunt, A. S., & Adler, K. (2008). Biology of the Reptilia. Society for the Study of Amphibians and Reptiles, vol 20. Society for the Study of Amphibians & Reptiles. Gomez, R. O. A Snake Dentary from the Upper Cretaceous of Patagonia. Journal of Herpetology , vol 45, no. 2, 2011, pp 230 233. Pyron, R. A., et al. (2014). Effectiveness of phylogenomic data and coalescent species tree methods for resolving difficult nodes in the phylogeny of advanced snakes (Serpentes: Caenophidia). Elsevier (18), 221 231. Rasmussen, J. B. A review of the Slender Stiletto snake, Atractaspis aterrima Gunther 1863 (S erpentes Atractaspididae ). Tropical Zoology (Florence) , vol 18, no. 1, 2005, pp. 137 148. Figure 1. Phylogeny of Atractaspis and Homoroselaps according to Pyron, et al. (2014). Shine, R., Branch, W. R., Harlow, P.S., Webb, J.K., Shine, T. (2006). Biology of burrowing asps ( Atractaspididae ) from southern Africa. Copeia , (1), pp. 103 115.