Caracterização histológica do estômago das espécies Hoplias malabaricus Bloch, 1974 (Characiformes: Erythrinidae) e Hoplosternum littorale Hancock, 1828 (Siluriformes: Callichthyidae): implicações ecológicas na alimentação de duas espécies de peixes de água doce

Abstract

The digestive system of animals is subject to modifications due to their feeding habits, theirinteraction with the environment, and the quality of the aquatic ecosystem in which they arelocated. Among the organs composing this system, the stomach is responsible for digestionand the initiation of the nutrient absorption process. Due to its cellular constitution, it standsout as an organ prone to histological alterations caused by these characteristics, presentingvariations in its shape and size. These alterations can compromise the maintenance of speciesin the ecosystem, as they are subject to both morphological and cellular changes. In thiscontext, two species with different feeding habits were chosen to investigate, through theanalysis of epithelial tissue, the possible changes that may occur in their stomachs. In thiscontext, the scarcity of studies analyzing and describing possible alterations in the epithelialtissue of the stomachs of H. malabaricus and H. littorale species was noted. These specieswere chosen as a biological model due to their feeding habits and distribution. H. malabaricusis a carnivorous species widely distributed in the Brazilian northeast, while H. littoraleexhibits omnivorous feeding behavior and is considered an invasive species. The lack ofresearch involving histological characteristics of their digestive tract, with an emphasis on thestomach, highlighted the need to expand the taxonomic levels of these species. Thus, studiesinvolving the Callichthyidae family and Siluriformes order, to which the H. littorale speciesbelongs, and the Erythrinidae family and Characiformes order, corresponding to the H.malabaricus species, were included in the work to increase data for comparison anddiscussion of the findings. The obtained results indicate the lack of studies describing theepithelial tissue of the stomach in species with carnivorous and omnivorous feeding habits,especially in representatives of the Caraciformes order. H. malabaricus and H. littorale didnot show differences in the layers forming the stomach wall. H. malabaricus did not exhibitdiscrepant results, showing a simple prismatic epithelial tissue. However, H. littoraleexhibited epithelial tissue classified as irregularly simple, contrary to expectations. In thissense, it is concluded that the epithelial tissue undergoes modifications related to theenvironment in which the species is located, leading to significant changes in its shape andheight.