Eco-morphology of sagittal otoliths in five Macrouridae species from Central Mediterranean Sea.

The increase in deep-sea exploitation and depletion related to fisheries activities has enhanced the importance of improving the knowledge about deep-sea species. Macrourids are an ecologically essential component of the bathyal community and are among the most abundant species in deep-sea environments worldwide. The present paper aims to investigate the sagittae morphology, morphometry, and shape of five Mediterranean Macrouridae species, investigating their intra and inter-specific variability. Shape and morphometric analyses highlighted the absence of directional bilateral asymmetry, with a morphometry and a mean contour shape changing among the investigated species. Despite this, statistically significant similarities were detected between Coelorinchus caelorhincus and Coryphaenoides guentheri, and between Nezumia aequalis and Nezumia sclerorhynchus. Otherwise, Hymenocephalus italicus showed the most marked differences in sagittae' features compared to the other species. The inter specific variability highlighted by results have confirmed the similarity in sagittae' shape and morphometry among both phylogenetically close species, and among those sharing similar depth distribution and feeding habits. Further analysis of the genetics, growth dynamics, feeding habits and environmental conditions experienced by species are required to confirm the environmental influence on sagittae, also comparing data from different Macrouridae populations.