Additional morphological information on two species of Caligus (Copepoda: Caligidae) parasitic on South African marine and estuarine fish

Abstract

Two species of Caligus that are parasitic on fish were collected from Lake St Lucia, South Africa. Specimens of C. confusus Pillai, 1961, were removed from the gill chambers of both Caranx sexfasciatus Quoy & Gaimard, 1825, and Rhabdosargus holubi (Steindachner, 1881), and Caligus acanthopagri Lin, Ho & Chen, 1994, from the skin of both Acanthopagrus berda (Forsskål, 1775) and R. holubi. Except for the occurrence of Caligus confusus on Caranx sexfasciatus, all of the remaining host records are new in South Africa. Caligus acanthopagri is recorded for the first time from South African waters. The morphological features of these two species were studied with scanning electron microscopy. Patterns were observed on the dorsal side of the cephalothorax of the male C. confusus. Such patterns have not previously been observed. The fine structures on the exopod of leg 4 of both species were studied, as these features are important for distinguishing species.

Key words: Crustacea, Caligus confusus, C. acanthopagri, external morphology, SEM.