Cherepanov Gennadiy Olegovich, Doctor of biological sciences, professor, sub-department of vertebrate zoology, Saint-Petersburg State University (7/9 Universitetskaya embankment, Saint-Petersburg, Russia), E-mail: firstname.lastname@example.org
Background. In accordance with ecology, aquatic and terrestrial turtles have different structural features of their shell. The purpose of the study is to carry out a comparative analysis of the bony carapace development in ecologically different turtles, to identify morphogenetic causes of structural differences and their evolutionary significance.
Materials and methods. The main material is a collection of specimens of Emys orbicularis and Testudo graeca of different ages stained with alizarin and located at St. Petersburg State University. Additional materials are shells of adult turtles from the collection of the Zoological Institute of the Russian Academy of Sciences.
Results and conclusions. Differences in the shell design of aquatic and terrestrial turtles are associated with degree of development of horny scutes and sulci. It was found that invagination of the sulci into the dermis can lead to local changes of dermal structure and to acceleration of ossification process. Aquatic turtles have relatively thin horny integument and their sulci do not have a noticeable effect on the growth of bony plates. As a result, the carapace bones grow relatively evenly around the periphery. This determines the uniformity of the costals and neurals, the narrow shape of the neurals and their partial reduction, the formation of wide peripherals that go medially beyond the marginal scutes. In terrestrial turtles (Testudinidae), horny scutes are thick and their sulci have a morphogenetic effect on bone formation. As a result, the bony plates grow unevenly, rapidly expanding in the areas under the sulci and slowly outside these zones. This determines the main distinctive features of testudinids: alternatively wedge-shaped costals, alternation of octagonal and tetragonal neurals and peripherals limited by pleuro-marginal sulci. The paper describes the specific mechanism of correlative links between the habitat, ontogenesis and definitive organization of the turtle shell.
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