Morfometria geométrica e histologia: ferramentas complementares na estimativa do sexo de filhotes da tartaruga marinha Caretta caretta (Linnaeus, 1758) (Testudines, Cheloniidae) dos estados da Bahia e do Espírito Santo

Abstract

The hatchlings and juvenile turtles have not anatomically visible secondary sex characteristics, so it is not possible to differentiate sex by viewing the carapace. Several authors advocate histological analysis as the best technique for performing sex of the Caretta caretta’ hatchlings. The aims of this study were to identify sex of hatchling C. caretta by geometric morphometrics of carapace and plastron and histomorphology and analyze if are difference between populations from Espirito Santo and Bahia by geometric morphometric of carapace and plastron. 204 stillborn hatchlings were collected in different nests along the Sítio do Conde’ Beach, Conde, Bahia and Regência Augusta’ Beach, Espirito Santo, both located in Brazil. For morphometric analysis each animal had photographed the shell and plaston and we used the software TPSUtil, TPSDig2, and MorphoJ for morphometrics analysis. The specimens were positioned and removed the plastron and some viscera to allow visualization of the kidneys and gonads, photographed after they were stored in 10% buffered formalin. The histological analysis followed the steps of conventional histological technique. Principal Components Analyzes do not reveals difference in carapace and plastron between females and males. Just discriminant function reveals there are differences between two localities. The sex ratio was female bias in both localities. The gonads were located near the renal hilum, with threadlike format. Ovarian cortex was possible to observe a welldeveloped cuboidal epithelium, associated with a disorganized medulla and interstitialrich matrix. The cortex of the testes was composed of a thin layer of simple squamous epithelium, a very well-developed medulla and low interstitial matrix, observing several seminiferous tubules clearly distinguishable. Work done with hatchling loggerhead turtles and other species also showed significant differences in the carapace that distinguish the sex of young turtles. The histological features were similar to those identified by other authors, some argue that the macroscopic analysis is sufficient to identify the sex of hatchlings, 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 young C. mydas, but authors disagree on this method to other species. Geometric morphometrics proved to be a promising tool whose analysis could, according to our study, corroborate the existence of two subpopulations that occur in the Brazilian coast.