Morfologia e morfometria geométrica para estimar o sexo de filhotes da tartaruga marinha Caretta caretta (Linnaeus, 1758) (Testudines, Cheloniidae): tecnologia da informação em prol da conservação

Abstract

The hatchlings and juvenile turtles have not anatomically visible secondary sex characteristics, it is not possible to differentiate sex by viewing the carapace. Several authors advocate histological analysis as the best technique for performing sexing chicks of the species Caretta caretta. The aim of this study was to identify sex of baby C. caretta by geometric morphometrics and histomorphology. 73 stillborn pups were used, collected in different nests along the Guanabara´s, Beach Anchieta, Espírito Santo, Brazil. For morphometric analysis each animal had photographed the shell. Were positioned supine removed the plastron, large intestine, liver and bladder to allow visualization of the kidneys and gonads, photographed after they were stored in 10% buffered formalin. We used the software TPSUtil, TPSDig2, CoordGen, PCAGen CVAGen for morphometrics analysis. The histological analysis followed the steps of conventional histological technique. Based on principal component analysis (PCA), PC1 explained 19.83% of the variation in the carapace of the puppies, while PC2 explained 14.71%. Canonical analysis revealed that there is a trend of sexual dimorphism between the pups through the carapace and that this may be related to the sex of the specimens. The gonads were located near the renal hilum, with threadlike format. Ovarian cortex was possible to observe a cuboidal epithelium with well developed, associated with a disorganized medulla and interstitial-rich matrix. The cortex of the testes was composed of a thin layer of simple squamous epithelium, a very well-developed marrow and low interstitial matrix, observing several seminiferous tubules clearly distinguishable. The macroscopic analysis of gonads alone does not allow the differentiation of the sexes, thus corroborating other work done with this species and other sea turtles. Work done with baby loggerhead turtles and other species also showed significant differences in the carapace that distinguish the sex of newly hatched chicks. The histological features were similar to those identified by other authors, some argue that the macroscopic analysis is sufficient to identify the sex of pups, which has been shown to effectively Dermochelys coriacea and Chelonia mydas, but was not effective in C. caretta. Hormonal measurements were also satisfactory to sex in order to cubs C. mydas, but authors disagree on this method to other species. The geometric morphometrics has the potential to Histology is an excellent tool for choosing to sex most used so far.