Morphological variation in Bradyidius pacificus (Brodsky, 1950) (Copepoda: Aetideidae) in the eastern part of the Sea of Okhotsk

Abstract

This study deals with individual variation in Bradyidius pacificus (Brodsky, 1950) which is one of the most common aetideid copepods of the waters near Kamchatka. Material was collected during spring-summer 2001 in the eastern part of the Sea of Okhotsk. Only data on females of V-VI copepodite stages are presented. Studied was the structure (setation in particular) of individual limbs, rostrum, cephalothorax and abdomen in more than 50 specimens. There were observed 12 variants of the rostrum, up to 5 variants of the structure of individual segments of the antennules, 8 variants of the protopodites of the maxillipedes and up to 3 variants of the structure of the basipodites of the periopods. The rostrum, antennules and maxillipedes were the most variable parts. There were no variability observed of the structure in the maxillules and the antennae. It is shown that the maxillipedes are more variable than it was considered earlier.