Morphological description of the digestive tract of Dormitator latifrons (Richardson, 1844) and comparison by size and sex ; Descripción morfológica del tracto digestivo de Dormitator latifrons (Richardson, 1844) y comparación por estadios y sexos

The study of the digestive tract of species of the family Eleotridae has been little addressed despite its importance for understanding fish physiology, nutrition, trophic associations and application in aquaculture. The Pacific fat sleeper Dormitator latifrons is one of the species of the family Eleotridae with great potential for aquaculture of which very little is known about its digestive system. This paper describes the morphology and histology of the digestive tract of D. latifrons and compares morphometric variables between stages and sexes, based on 127 specimens collected in a culture system. Biometric data were recorded for each fish, and then the digestive tract was described, measured in sections, and tissue fragments were fixed in 10 % neutral formalin for histological analysis. Tissue samples were processed by the paraffin embedding technique and stained with hematoxylin and eosin; morphometric data were compared between stages and sex. The digestive tract was composed of mouth, pharynx, esophagus, stomach, intestine and anus; and each section presented the four concentric tissue layers (mucosa, submucosa, muscular and serosa) characteristic of the fish digestive system. Morphologically, the most distinctive feature was the presence of a tubular "I" shaped stomach, well delimited and with abundant tubular gastric glands. Intestinal length and index were significantly different (p < 0.05) between stages and sexes, placing juveniles in the omnivore trophic level while adults are positioned as herbivores; the analysis by sex showed a significantly lower intestinal index (p < 0.05) in females compared to males. The results show a polytrophic behavior of the Pacific fat sleeper D. latifrons that could be associated with habitat, food availability, or sexual maturity. The presence of a functional stomach allows us to classify this species as gastric and opens the possibility of future studies on the digestive physiology of this species and the composition of the ideal diet for cultured organisms, ...