The copepodid and two chalimus stages of Caligus latigenitalis Shiino, 1954 (Copepoda, Siphonostomatoida, Caligidae), parasitic on Japanese black sea bream, Acanthopagrus schlegeli

Abstract

The copepodid, the second chalimus, and both sexes of the fourth chalimus of Caligus latigenitalis Shiino, 1954 are described based on specimens obtained together with adults from black sea bream Acanthopagrus schlegeli cultured in Hikimoto, Japan. No developmental stages of C. latigenitalis have been described thus far. The chalimus larvae of this species could be identified to stage, and the stages confirmed, by the basal structure of the frontal filament and the body length as compared to some congeners. The following points are discussed : quantitative variation of armature elements of the legs among congeneric copepodids, growth increments in the successive chalimus stages, the two types of frontal filament recognized among congeneric chalimus larvae, and the problematic, so-called preadult stage. The number of postnaupliar developmental stages is deduced to be six, the same as in other copepod groups including the freeliving forms.