Microstructural characterization of the body key scale morphology in six Iranian endemic Aphanius species (Cyprinodontidae): Their taxonomic and evolutionary significance

Abstract

The microstructural characteristics of the body key scales were described for six Iranian endemic Aphanius Nardo, 1827 species. Among them, five species genetically belong to the “Iranian inland and inland-related Aphanius species, IIRAS” group, while A. ginaonis (Holly, 1929) belongs to the “brackish water species” group. General scale shape in the studied Aphanius species was cycloid with the exception of A. ginaonis, which has cycloid scales with few spinous-like structures present in the posterior edge of the scales. Considering phylogenetic relationships of the studied taxa, the most likely explanation for presence of the spinous scales in Aphanius species is the primary existence of these scales in this group. In addition, among the IIRAS group, the most different lepidont was recognized in scales of the A. isfahanensis Hrbek, Keivany and Coad, 2006 (pointed), which is similar to lepidonts in the A. ginaonis. The scales of these species are polygonal with similar typology. The similarity in lepidont morphology between A. ginaonis and A. isfahanensis can explained by (i) the primary existence of the rounded lepidont in this group, and (ii) since A. ginaonis and A. isfahanensis belong to two separate phylogenetic lineages, therefore, similarity in their lepidont morphology could be results of convergent evolution.