Trophic morphology and diet of the endangered fish Tlaloc hildebrandi (Cyprinodontiformes: Profundulidae)

Introduction: Tlaloc hildebrandi is a freshwater killifish, endemic to Southern Mexico and under threat of extinc-tion; the knowledge of the trophic morphology and diet is needed by conservation managers.Objective: To analyse and describe the anatomy of the visceral skeleton, visceral musculature, digestive tract and its adjoining glands of T. hildebrandi; as well as its diet.Methods: We performed the trophic anatomy on 20 adult specimens of both sexes, through manual dissection; as well as gut content analysis in 60 individuals to describe the diet.Results: As notable characters of the visceral skeleton of T. hildebrandi we found the posterior notch of the premaxillary, the presence of the "coronoid cartilage", the tricuspid shape of the gill rakers of the first branchial arch, and the presence of the coronomeckelian bone; some outstanding characters of the visceral musculature are the origin of the retractor dorsalis muscle from the first four vertebral centra, and the division of the pharyn-goclavicularis externus muscle into two sections. The notable characters of the digestive tube are the absence of stomach and pyloric caeca, and the presence of the "intestinal valve". Insects (IVI = 66.6 %) and ostracods (13 % IVI) were the dominant prey items of the Tlaloc hildebrandi diet; larvae and adults of the family Chironomidae were the most dominant insects in the diet (53 % IVI ).Conclusions: The organization of the digestive system of T. hildebrandi corresponds to the general morphologic pattern of the Cyprinodontiformes; however, we register as new information for these fish, the presence of the "coronoid cartilage" and the "intestinal valve". The structures of the trophic morphology and the components of the diet, confirms us that T. hildebrandi is a carnivorous-insectivorous fish.