Histometric parameters of the large intestine of hybrid marmosets Callithrix sp. under the influence of seasonality

Morphofunctional characteristics of the large intestine are rarely explored to understand the physiology, behavior and ecology of neotropical primates. In this study, we analyzed the histometric parameters of the large intestine of hybrid marmosets (Callithrix sp.) captured in forest fragments of Viçosa-Brazil, under seasonal interference. These animals were predominantly insectivorous in the rainy season and gummivores in the dry season. Large intestine fragments were collected and processed according to histological methods and stained with toluidine blue for general analysis, periodic acid of Schiff (PAS) and Alcian blue (AB) for goblet cells, Grimelius and Masson Fontana for argyrophil and argentaffin endocrine cells. Several histometric parameters were more expressive in the large intestine of the rainy season marmosets: greater thickness of the parietal layers, greater number of argyrophil and argentaffin endocrine cells, and AB-positive goblet cells, characteristics favor secretomotor functions and reduce the passage time of the fecal bolus, which is consistent with an insectivorous diet. In contrast, parameters such as crypt width, height of the absorptive cells and striated border, and the number of PAS-positive cells were more expressive in the dry season marmosets, reflecting the need for longer passage time for digestion and absorption of food items from tree gum, which are more complex and demand the action of microorganisms present in the large intestine, as well as greater protection against the abrasive action of dietary fibers and against microorganisms. Thus, it can be said that the marmoset's large intestine has morphological adaptations to maximize energy intake from the diet, which alternates under the influence of seasonality.     

Anatomical parameters of the body and the digestive tract of Callithrix sp. marmosets under the influence of seasonality

Due to the ecological importance and given the scarcity of studies on the digestive morphology of primates, anatomical aspects of the body and digestive tract, as well as food content were analysed for marmosets Callithrix sp. (hybrids of exotic species) captured in forest fragments in Minas Gerais - Brazil, during the dry and rainy seasons, considering that seasonal variations affect the availability of food and quality of diet. Data such as body weight and length, and thoracic and abdominal perimeters were analysed, and no significant difference was found between dry and rainy seasons. In relation to the digestive tract, length, weight and diameter of the oesophagus, stomach, small intestine and large intestine were measured, in addition to the isolated caecum. There was a significant difference in the diameter of the ascending colon, which was larger in the animals in the dry season than in the rainy season. The difference found may be related to diet, and through analysis of the gastric and caecal contents, it was observed that gum was the main food item for the dry season marmosets, while in the rainy season the animals consumed mainly arthropods. Thus, the characteristic observed in the digestive tract of dry season marmosets is a reflection of an adaptive response to gum intake, since this food item is of low digestibility, necessitating that the food content be retained for a long time in this segment of the large intestine, helping the process of microbial fermentation and better energy utilization for these animals.