Comparative Morphology of the Digestive Tract of African Bush Fish (Ctenopoma acutirostre) and Paradise Fish (Macropodus opercularis) Inhabiting Asian and African Freshwaters

SIMPLE SUMMARY: The diets of ornamental aquaculture and aquarium fish usually differ significantly from the diets and types of diets present in natural habitats. These differences can significantly affect the health and welfare of the reared animals. One popular group of aquarium fish is the Anabantoidei fish, which can breathe atmospheric air using an additional respiratory organ—the labyrinth. These fish are commonly bred for both ornamental and consumption purposes. The structure of the digestive system of labyrinth fish such as African bush fish (Ctenopoma acutirostre) and paradise fish (Macropodus opercularis) is currently not known. In the present experiment, the fishes were studied and characterized based on their morphological and histological body structures. The results obtained suggest that although both species are generally regarded as omnivorous, their digestive tract structures have some differences, including the structure of the mouth, mouth cavity and esophagus, which indicate that the African bush fish is much better adapted to carnivorous feeding than the paradise fish. The results obtained will enable better feeding strategies to be developed for these Anabantoidei, thus improving their health in both commercial and domestic breeding. ABSTRACT: Anabantidae is a large and diverse group of fish cultured both under aquaculture conditions and as a hobby. These fish share a common structural feature in the form of an additional respiratory organ. Despite the enormous availability of these fish worldwide, little is known about their feeding preferences in husbandry and their influence on homeostasis under both industrial and domestic conditions. This study describes, for the first time, the structure of the digestive tracts of two Anabantoidei fishes: African bush fish (Ctenopoma acutirostre) and paradise fish (Macropodus opercularis). The overall structure of the digestive tract and its histological structure were analyzed and compared in both fish species. Physiological predispositions indicated a predominance of omnivorous fish traits in M. opercularis in contrast to C. acutirostre, which has several morphological traits indicating greater adaptation to carnivory, particularly ichthyophagy. The results obtained will allow further research to be conducted in the future to optimize the nutrition and feeding of these fish and to develop appropriate dietary recommendations.