Intra- and interspecific variability in external morphology among three Symphodus species (Labridae)

Labridae (wrasses) showcases a wide range of morphological variations, including diverse shapes, as well as a spectrum of ecological and behavioural characteristics. This study compared intra- and interspecific variation in three congeneric Symphodus species based on 19 morphometric characters associated with external morphology. Morphometric characters were commonly summed as the percentage of total length (TL%). The principal component analysis showed a clear separation of S. roissali from the other two Labridae species. The morphological distinction between species was statistically significant for all variables. While post-orbital length, anal fin length, caudal fin length and soft dorsal fin length are the hallmarks for Labridae species examined in this study, care should be taken when using other characters. Especially S. cinereus and S. ocellatus show similarities in many characters. S. roissali is distinguished from the other two species by its larger head and fin lengths (dorsal, anal, and pectoral). Intraspecific sexual dimorphism was significant for eight variables in the S. cinereus. No significant intraspecies morphological differences by sexes were observed for S. roissali and S. ocellatus species. Sex determination for these two species should be based on macroscopic examination of their gonads rather than external morphology.