Morfologia da gônada de filhotes natimortos de tartaruga-de-pente (erecmochelys imbricata)

Abstract

Climate change is considered a major threat to global biodiversity. Hawksbill turtles (Eretmochely imbricata) are the most critically endangered species that spawn off the coast of Rio Grande do Norte. Knowing that sea turtles exhibit their temperaturedependent sex determination, they are considered vulnerable to changes in thermal regimes. Thus, the present study aims to characterize the gonad morphology of stillborn hawksbill turtle hatchlings. The animals were collected on the beach of Cabo de São Roque, municipality of Barra de Maxaranguape. After collection, the plastron was removed, where it was possible to identify and dissect the gonad-mesonephro complex (GMC). This complex was submitted to macroscopic analysis, later fragmented and fixed with 4% paraformaldehyde and 2.5% glutaraldehyde in phosphate buffer for 24h for processing for light microscopy and transmission electron microscopy (TEM), respectively. The female gonads were found to have a grainy appearance, translucent whitish color and spindle shape. In the male gonads, a smooth surface was observed, with an opaque white color and an approximately ovoid shape. It was also possible to observe greater vascularization on the surface of the female gonads compared to males. The testicles had an average right width of 63.48 ± 17.66μm and the left 6 1.11 ± 14.96μm, while the right ovaries 71.79 ± 17.67μm and the left 66.86 ± 20.74 μm (P>0.05) Under microscopy, it was possible to confirm the sex of individuals, mainly due to the difference in the structure of the marrow, where females had disorganized cellularity, with the presence of oogonias, lacunae and blood vessels. Males showed an organizational pattern in the medulla marked by the presence of seminiferous tubules throughout its length. Regarding the ultrastructure, the females presented a stroma marked by a network of association between blood vessels, gaps, fibroblasts, collagen fibers, smooth muscle, interstitial cells with cytoplasm rich in electron-dense vesicles and germline cells (ovogonia) that they had a large oval shape, with a conspicuous rather than a central nucleus, and abundant cytoplasm. In males, it was possible to observe inside the seminiferous tubules, pyramidal cells with little heterochromatin, approximately triangular and basal apical cytoplasm with an evident nucleolus characteristic of Sertoli cells (CS). Along the basal lamina, pavement cells with characteristics of myoid cells (Cm) were identified, and in the interstitium cells with characteristics of endocrine function were observed with electron-dense vesicles inside, a pattern similar to Leydig cells (Ly). Ly had a rounded nucleus, irregularly distributed heterochromatin and a prominent nucleolus. The paramesonephric ducts in females is lined with simple columnar epithelium and tall cubic cells, whereas in males, it is lined with low cubic cells, with an elongated elliptical profile and characterized by the absence of lumen. The appendages in females have an oviduct-connecting ring with a larger number of cells when compared to the ring in males. In addition, the end of the appendages also differs between sexes. It was concluded that both macroscopic, microscopic and ultrastructural evaluation are effective and reliable techniques for sexual identification. It is also worth noting that in the absence of the gonads, microscopic analysis of the paramesonephric ducts and duct appendages represent an alternative for the sexual identification of the species in question