Ecomorphological patterns of the lapilli of Paranoplatense Siluriforms (South America)

The morphology and morphometry of lapillus otoliths were studied in bottom frequenters, intermediate and benthonic fishes. The shape, margins and type of sulcus of 3 groups of otoliths from 19 species were analyzed: group 1 (bottom frequenters, 11 spp), group 2 (intermediate, 5 spp) and group 3 (benthonic, 3 spp). The indices EL (maximum width of the lapillus (WOL)/maximum length of the lapillus (LOL) %) and S (sulcus area/otolith area %) were calculated for each species.The lapilli of bottom frequenters and intermediate groups showed, in their ventral face, similar morphological features, high shape variability (oblong shape, elongated shape and quadrangular shape) and a sulcus surface that represents 16–34% of otolith surface. The lapilli of the benthonic group are globosal or rounded with a sulcus surface that represents less than 12% of otolith surface.Statistical analyses showed significant differences in the EL and S indices between the benthonic group and the other two groups, but there were no differences between the otoliths of the bottom frequenters and intermediate groups. EL and S values could be used to characterize the lapilli of the paranoplatense fish and could be considered a useful tool for fish ecology studies.