Dissertation Juliana Flávia Ferreira E Silva Paranaíba

AUTHOR: Juliana Flávia Ferreira E Silva Paranaíba

TITLE: Morphology of the digestive tube of the sloth (Choloepus didactylus (linnaeus, 1758): pilosa, megalonychidae)

ADVISOR: Profa. Dra. Mônica Rodrigues Ferreira Machado

DEFENSE DATE: 02/25/2021

ABSTRACT

Diversified diets can contribute to digestive organs specializations, thus, knowledge of their anatomy is essential to understand several parameters, such as eating habits, diagnosis and treatment of illnesses, maintenance and reintroduction and phylogenetic  relationships. Xenarthran species are a good example of animals with varied eating habits. Consisting of armadillos, anteaters and sloths, this group presents a unique anatomy. Therefore, the objectives of this work were to compile the existing data about the Xenarthra digestive tube morphology and to describe the anatomy of these organs in Choloepus didactylus. A systematic review was carried out based on original studies in Portuguese and English for the first part of this study. For the second objective, the morphology of the digestive tube of C. didactylus was described from the dissection of four specimens. After applying inclusion and exclusion criteria, eleven studies were part of the systematic review, covering five species. The esophagus of Tamandua tetradactyla and Bradypus variegatus has similar macroscopic morphology with some histological differentiations. The stomach of T. tetradactyla is unicavitary while B. variegatus and B. torquatus have a pluricavitary stomach. The description of the intestines basically presents differences in topography, bowel loops divisions and histological differentiations. The digestive tube of C. didactylus is similar to that described for other Xenarthra. The species have features of ruminant herbivores, althought is not. The stomach is similar to that of other species of sloths, with some differences. We highlight differences in the nomenclature of the stomach chambers. Many macro and microscopic adaptations are related to eating habits. Based on the review, the scarcity of complete morphological studies on Xenarthra's digestive system is evident, which can directly compromise aspects applied to these species in diferente areas, as well as the understanding their dietary features. From this analysis, we highlight important macro and microscopic specializations in the stomach, while the other organs present the expected morphology.

Keywords: comparative anatomy, wild animals, stomach, histology, Xenarthra