Biomecânica e variações morfológicas cranianas em Leposternon Wagler, 1824 (Reptilia: Amphisbaenia)

• Autor(a) principal: Hohl, Leandro dos Santos Lima
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/4908
• topic: Biogeography; Kinematics; Performance; Skull; Squamata; Biogeografia; Crânio; Cinemática; Desempenho; Squamata; Cobra - Morfologia; Répteis; Imagem tridimensional; CNPQ::CIENCIAS BIOLOGICAS::ZOOLOGIA

The Amphisbaenia have a fossorial habit and belong to the Squamata group. The genus Leposternon is represented by species that occur in almost all Brazilian states. With the exception of Leposternon microcephalum, which also occurs in Bolivia, Paraguay, Argentina and Uruguay, all other species are endemic to Brazil. They have several morphological adaptations to a fossorial lifesyle, which includes a heavily ossified and compacted skull. This assumes four morphotypes, which are associated with different types of excavation. The study of excavation modes, involving kinematics and locomotor performance, as well as 3D structural analysis and cranial morphological variations have been performed within the genus Leposternon. However, observations and models proposed by biomechanical studies do not directly associate cranial morphological variations with the type of movement and locomotor performance produced by the animal. In addition, the cranial variations in Leposternon are based only on descriptive analyzes. The objective of the present study was to verify inter- and intraspecific cranial morphological variations through the Geometric Morphometrics technique and to associate such variations with the locomotor performance of these animals, and to create a three-dimensional model for biomechanical studies, aligning the virtual model of the skeleton with videofluoroscopy images (Scientific Rotoscopy). Significant morphological variations were found among species, and these were related to body size and geographic distribution of specimens. As subtle differences in cranial size or shape may represent significance in bite force and digging capacity and in excavation speed, the cranial variation found between species and Leposternon specimens may directly influence their diet and locomotor performance. Leposternon microcephalum and L. scutigerum are morphometrically distinct species. The first is shorter and robust, with a wider head while the other is longer and thin, with a narrower head. They share the same digging movements. The animals analyzed reached relatively high speeds, but individuals with narrower skulls dug faster. A negative correlation between skull velocity and width was determined, but not with the total length or diameter of the body. The analysis of the biomechanics of the three-dimensional skeleton of a L. microcephalum specimen in the virtual environment was determinant for an even more detailed description of its excavation behavior revealing the effective participation of other structures, such as the ribs, in the excavation concern. We can state that the reliability and complexity of descriptions of cranial variations and locomotor performance and behavior increase according to the use of innovative techniques and methods.