Exploring the riverbed: How olfactory organ morphology shapes the life habits of freshwater stingrays (Potamotrygoninae)

The olfaction in batoids have an important role for initial detection of the chemical stimulus produced by prey during the foraging activities. The present study relates the morphology of olfactory rosettes to the habitat use and feeding habits in four potamotrygonin species. The morphological and histological descriptions of the olfactory structures are provided, using preserved olfactory rosettes. A simpler structure of olfactory organs in Paratrygon sp. does not indicate a primary sensory role during the initial phase of its feeding behavior. In Potamotrygon wallacei, the largest surface area of primary lamellae suggests enhanced olfactory sensitivity related to its generalist feeding habits and complex substrate exploration. Although the gross morphology is similar, histological analyses revealed that the sensory and non-sensory regions present differences in epithelial cell composition among species, with variations in the secondary folds shape and the distribution of mucus cells. The simplicity of secondary folds in both Paratrygon sp. and Potamotrygon orbignyi probably is related to their specialized feeding habits, requiring fewer adaptations to detect different types of chemical stimuli. These findings provide insights into the functional morphology of olfactory organs in potamotrygonin stingrays and their ecological implications, evidencing the intricate sensory adaptations crucial for foraging success in diverse freshwater habitats. Additionally, it becomes necessary to take into account the contribution of all sensory systems to understand their foraging behavior. Nonetheless, the generalization of the morphological characteristics of olfactory organ in a potamotrygonin species requires caution, since morphological variations can be found, especially to widespread species.