Allometric variation and sexual dimorphism in Lycodes yamatoi Toyoshima, 1985 (Perciformes: Zoarcidae) from the Sea of Japan

Abstract

A detailed analysis of allometric variation and sexual dimorphism in Lycodes yamatoi (Perciformes: Zoarcidae) was carried out using an original method developed by the authors. An allometric pattern of growth was revealed not only in plastic but in some meristic characters, such as the number of teeth on the bones of the mouthparts and the number of gill rakers on the first gill arc. It was determined that most of the morphological characters of L. yamatoi were subjected to positive allometric variability (the proportions of the head and the anterior part of the body), while growth of the remaining characters was specified by negative allometry (the length of the rays of pair and caudal fins, interorbital distance, and isthmus width) and isometry (the standard length, ante-anal distance, and head width on the vertical neck). The juveniles of L. yamatoi have no significant sexual distinctions either in plastic or in meristic characters. Adult females and males of L. yamatoi significantly differed by characters composing the head complex, the actual length of the head, and correlatively related with it ante-dorsal and ante-pectoral distances. The dimensional indexes of antedorsal and ante-pectoral distances, and the relative sizes of maxillary bones (lmx/c) are of the greatest diagnostic value for sex differentiation.