Sexual dimorphism in spined loaches

Morphological differences between females and males spined loaches belonging to five species from the Adriatic basin were examined. Besides the presence of the Canestrini scale and the length of the pectoral fins, sexual dimorphism is also visible in the position of the pectoral fins, as well as in the length of the pelvic fins. Both pectoral and pelvic fins are significantly longer in males than in females, whereas pectoral fins of females are located more anteriorly then in males. Differences in the length of pectoral and pelvic fins among species are also revealed. The role of the observed secondary sexual characters in males is probably connected with their special mating behavior. Furthermore, a hypothesis that habitat conditions have greater impact on body dimensions of females than males is proposed.