Histological and histochemical features of the small intestine in loggerhead sea turtle hatchlings (Caretta caretta)

Abstract

Loggerheads (Caretta caretta) are endangered marine turtles and basic research is an essential component of conservation. In an attempt to provide further information in this field, we aimed to identify the microscopic morphological and histochemical features of the small intestine in the loggerhead turtle. Four loggerhead turtle hatchlings were used in this study; due to the loggerhead’s endangered status, this study was performed with dead animals. During necropsy, the cranial and caudal portions of the small intestine were obtained. The samples were embedded in paraffin and stained using the following techniques: Hematoxylin and Eosin, Gomori’s trichrome, Periodic acid-Schiff reactive (PAS), Alcian blue (pH 1.0 and pH 2.5), PAS-Alcian blue, Toluidine blue (pH 4.5 and pH 3.5), Giemsa, colloidal iron, Perl’s blue, Wilder’s impregnation, Methenamine silver, Grimelius and Masson-Fontana. The intestinal mucosa present plicae featuring a pseudostratified columnar epithelium with abundant blood vessels and abundant lymphatic vessels in the submucosa; both of these observations represent the main histological findings. The secretory granules in the goblet cells demonstrated the following characteristics: in the cranial portion, neutral mucopolysaccharides, sulfated acid mucopolysaccharides and mucopolysaccharides with sialic acid were found. In the caudal portion, neutral mucopolysaccharides and mucopolysaccharides with sialic acid were observed. Argentaffin cells were detected along the small intestine, primarily in the cranial portion. There are morphological differences, both histological and histochemical, between the cranial and caudal portion in the small intestine of C. caretta. These characteristics are correlated with possible functions in tissue physiology.