Morphology of the Digestive Tube of the Podocnemididae in the Brazilian Amazon

Morphological characterization of the digestive tube of hawksbill sea turtle (Eretmochelys imbricata) hatchlings

“…However, Magalhães et al (2012), report the presence of an exceptionally long esophagus in proportion to the curvilinear length of the carapace in Dermochelys coriacea , extending for almost half the length of the body, only then turning to the left and joining the stomach. Our findings also differ from reports for freshwater turtle species such as Podocnemis expansa, Podocnemis unifilis, Podocnemis sextuberculata, Podocnemis erythrocephala , and Peltocephalus dumerilianus (Magalhães et al, 2014), where all present an esophagus in the form of a thin tube and of uniform diameter, while E. imbricata hatchlings present an esophagus in the form of a thick tube, wide in the anterior region and narrow in the posterior region.…”

“…The entire stomach region of the animals investigated in this study contained gastric glands that resemble those observed in C. mydas sea turtles in all age groups, hatchlings (Chen et al, 2015), juveniles and adults (Magalhães et al, 2010), and the herbivorous and omnivorous freshwater species, P. sextuberculata and Peltocephalus dumerilianus , respectively (Magalhães et al, 2014), differing slightly from three other freshwater herbivorous species, P. expansa , P. unifilis, and P. erythrocephala (Magalhães et al, 2014), as the glands of these animals are absent in the cardiac and fundic regions and present only in the pyloric region. Thus, gastric gland distribution may reflect an adaptation to feeding habits (Chen et al, 2015).…”

“…According to Hildebrand (1995), carnivorous reptiles display a simpler stomach and most herbivorous reptiles exhibit a more complex stomach, which functions as a reservoir or fermentation chamber. In this sense, hawksbill turtle hatchlings presented the simplest stomach morphology, as described for other sea turtles with a carnivorous diet, such as C. mydas (Chen et al, 2015), L. olivacea, Caretta caretta, and D. coriacea (Magalhães et al, 2012) hatchlings, and the omnivorous freshwater species Peltocephalus dumerilianus (Perez-Eman & Paollilo, 1997;Magalhães et al, 2014), and Pangshura tentoria (Rahman & Sharma, 2014). Animals that exhibit a predominantly herbivorous diet, such as C. mydas juveniles and adults (Magalhães et al, 2010(Magalhães et al, , 2012) also differ in terms of the presence of a large sacculation in the fundic region with a blind bottom, while three freshwater turtle species, P. expansa, P. unifilis, and P. erythrocephala, which also exhibit a predominantly herbivorous diet (Balesienfer & Vogt, 2006;Souza & Vogt, 2008;Vogt, 2008) present stomachs divided into two compartments separated by a constriction with longitudinal mucosa folds, where the first compartment is formed by the cardiac and fundic regions, both formed by transverse folds throughout the mucosa, while the second curves to the right immediately after constriction, forming a well-developed pyloric region and displays a mucosa organized by longitudinal folds (Magalhães et al, 2014).…”

“…Calais Junior et al (2016), when describing the esophagus morphology of C. mydas, observed the presence of PAS-positive mucus-producing glands located in the gastroesophageal region mucosa. Vieira-Lopes et al ( 2014) also verified the presence of well-defined glands interspersed in the mucosal epithelium of the esophagus on some freshwater turtles, such as Phrynops geoffroanus, formed by clear cells in a semicircular arrangement, while Magalhães et al (2014) reported the presence of mucus-producing superficial cells throughout the esophagus when studying the morphology of the DT of freshwater turtles belonging to the Podocnemididae family, forming a continuous layer of secretory cells occupying the entire apical region, stained positively with PAS, more intense in the posterior portion. In addition to these mucus-producing cells, the authors also verified the presence of some goblet cells irregularly distributed among the columnar cells in the epithelium but did not observe esophageal glands.…”

Biology of the Big-headed Amazon River Turtle, Peltocephalus dumerilianus (Schweigger, 1812) (Testudines, Pleurodira): the basal extant Podocnemididae species

“…Micro and macroscopic descriptions of the digestive system have really indicated omnivorous habits. The stomach main function is digestion, rather than food storage, unlike in P. erythrocephala, P. expansa, and P. unifilis (see Magalhães 2010;Magalhães et al 2014 for details and comparisons with other Brazilian podocnemidids). During annual floods, the proportion of plant matter in the diet increased considerably, due to difficulty in obtaining animal-based foods (Pérez-Emán and Paolillo 1997;De La Ossa-Velásquez 2007;) (Table 3).…”