A review of the genus Caligus (Copepoda: Caligidae) from South Africa

English: The ichthyoparasitic and fish louse copepod genus, Caligus Müller, 1785, is the most abundant copepod genus, found in almost any part of the world’s oceans, with the exception of one freshwater species. More than 315 nominal species have been described, of which only 26 species have been recorded off the coast of South Africa. Most of the information on this genus from South Africa is limited to very old and often incomplete taxonomic descriptions. Of the 26 known species of Caligus recorded from South Africa, only 15 species have reference material, either in the collection of the South African Museum, or in the collection of the Aquatic Parasitology Research Group, University of the Free State, Bloemfontein. These 15 species are redescribed, and the validity of each species is discussed. Additional morphological features for six species are given, based on studies with the aid of scanning electron microscopy. In addition to the species descriptions, a synopsis of host/parasite and parasite/host is given. A key to all 15 species reviewed in the present study is included. The reference material of 15 species has disappeared, mainly due to material on loan that got lost. These species will, however, remain as species recorded from South Africa, until such time that their status can be validated. However, for the purpose of this study, they are included as part of the South African fauna. Three of these 15 species, Caligus affinis Heller, 1866, C. africanus Oldewage & Van As, 1989 and C. labracis Scott, 1902, have been misidentified. Specimens of the misidentified C. affinis were subsequently collected from the same host, Pomatomus saltatrix (Linnaeus, 1766), in the present study, and a detailed description is included for this species (Caligus sp. B), but it is still uncertain whether this species is new. Caligus africanus is not a valid species and is therefore synonymised with Caligus tetrodontis Barnard, 1948. One new species (Caligus sp. A) has been collected from the Kob, Argyrosomus japonicus (Temminck & Schlegel, 1843), and a fully illustrated description is supplied. With the description of this new species, as well as the inclusion of Caligus sp. B, the total number of species recorded from the South African coast is 28. The genus Caligus can traditionally be divided into four major species groups based on the segmentation and armature of the exopod of the fourth leg. In this study, a fifth group is proposed to include eight species (two species from the present study) with the same characteristic features of the exopod of the fourth leg. In this group the exopod of leg 4 is either one- or two-segmented, the first segment bearing a terminal spine and the last segment bearing only two terminal spines. Future studies on the caligid copepods of South Africa should involve molecular work, as this trend may be useful when species are found which are close to each other, as was found in the present study with Caligus epinepheli Yamaguti, 1936, and C. rotundigenitalis Yu, 1933, or to explore phylogenetic relationships within the family to see whether a species belongs to another genus or not. During the course of the present study, which started as an Honours project in 1997, four papers have been published in international journals. Various conference proceedings have also been published during the course of this study. This present study forms a well-outlined reference for future studies on species of Caligus from South Africa.