Geometric morphometrics for the analysis of character variation in size and shape of the sulcus acusticus of sagittae otolith in species of Gerreidae (Teleostei: Perciformes)

Sagittal otoliths are a useful structure to distinguish teleostean fishes. However, character variation in size and shape of the sulcus acusticus has not been tested among Gerreidae Günther, 1862 species. For the first time, this paper explores the size and shape variation in the sulcus acusticus using landmark data and geometric morphometric methods. Variation in the sulcus acusticus size, as estimated with centroid size, is not a useful feature to distinguish neither the five genera nor all species in this study. However, since analyses of variance followed by Tukey a posteriori tests detect differences among groups of species, it is possible that the size of the sulcus acusticus will still be useful as a phylogenetic character. As expected, the pattern of variation in the shape of the sulcus acusticus consists of well-defined character states exclusive of each of the 18 species of Gerreidae included. All comparisons in multivariate analyses of variance of semi-landmark configurations with a CVA were statistically significant, and the rates for correct posterior classifications were all above 79%. Discriminant axes allowed to locate variation in particular regions of the sulcus acusticus outline that contribute most to the distinction among genera. Results revealed species in the same genus share a particular shape in the ostium and posterior extension of the cauda. Variation in the shape of the sulcus acusticus is, therefore, a very useful character to identify species in Gerreidae.