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

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Date
2004-09
Authors
Grobler, Nicolaas Johannes
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University of the Free State
Abstract
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.
Afrikaans: Die parasitiese kopepod en visluis-genus, Caligus Müller, 1785, is die genus met die meeste spesies en word in amper elkeen van die wêreld se oseane aangetref, met die uitsondering van een varswater spesie. Meer as 315 nominale spesies is tot dusver beskryf, waarvan slegs 26 spesies vanaf die Suid-Afrikaanse kus aangeteken is. Die meeste inligting van die genus in Suid-Afrika is tot baie ou en meestal onvolledige taksonomiese beskrywings beperk. Van die 26 bekende Caligus spesies wat van Suid-Afrika aangeteken is, het slegs 15 spesies verwysingsmateriaal wat óf in die versameling van die Suid-Afrikaanse Museum óf in die versameling van die Akwatiese Parasitologie Studiegroep, Universiteit van die Vrystaat, Bloemfontein, gestoor word. Hierdie 15 spesies word herbeskryf en die geldigheid van elke spesie word bespreek. Bykomende morfologiese besonderhede vir ses spesies word ook gegee wat met die hulp van skandeerelektrone-mikroskopie bestuur is. Tesame met die spesie-beskrywings word `n sinopsis van gasheer/parasiet asook een van parasiet/gasheer gegee. Al 15 spesies, wat in die studie bestudeer is, word in `n sleutel saamgevat. Die verwysingsmateriaal van 15 spesies het weggeraak, hoofsaaklik as gevolg van spesies wat uitgeleen is. Hierdie spesies sal wel deel van die Suid- Afrikaanse verwysingsmateriaal bly totdat hul status geldig gemaak word. Vir die doel van die huidige studie word hierdie spesies as deel van die Suid-Afrikaanse fauna ingesluit. Drie van hierdie 15 spesies, Caligus affinis Heller, 1866, C. africanus Oldewage & Van As, 1989 en C. labracis Scott, 1902, is verkeerd geïdentifiseer. Materiaal is ook versamel vanaf Pomatomus saltatrix (Linnaeus, 1766), dieselfde gasheer waarvan Caligus affinis verkry is. Die status van die spesie (Caligus sp. B) is nog onbekend, maar is nie C. affinis nie. Caligus africanus is nie `n geldige spesie nie en word as `n sinoniem van Caligus tetrodontis Barnard, 1948 beskou. Een nuwe spesie is vanaf die kob/kabeljou Argyrosomus japonicus (Temminck & Schlegel, 1843) versamel en `n volledige geïllustreerde beskrywing word gegee. Met die beskrywing van die nuwe spesie sowel as die insluiting van Caligus sp. B, is die totale getal spesies wat vanaf die Suid- Afrikaanse kus versamel is 28. Die genus Caligus is tradisioneel in vier groepe spesies verdeel, gebaseer op die segmentasie en armatuur van die eksopood van die vierde poot. `n Vyfde groep word in die huidige studie voorgestel, wat agt spesies (twee spesies van die huidige studie) insluit, gebaseer op dieselfde morfologiese eienskappe van die vierde poot. In hierdie vyfde groep het die eksopood van die vierde poot óf een óf twee segmente, die eerste segment het `n terminale stekel terwyl die tweede segment slegs twee terminale stekels het. Toekomstige studies op die kaligid kopepode van Suid-Afrika moet molekulêre werk insluit, want dit kan baie hulpsaam wees met spesies wat baie naby verwant is, soos in die huidige studie gevind is waar Caligus epinepheli Yamaguti, 1936, en C. rotundigenitalis Yu, 1933, baie naby verwant is aan ander spesies. Die filogenetiese verwantskappe tussen families kan ook met molekulêre werk gedoen word. Gedurende die huidige studie, wat as my Honneurs projek in 1997 begin het, is vier wetenskaplike artikels in internasionale joernale gepubliseer. Verskeie kongresbydraes gedurende die huidige studie is ook gepubliseer. Die huidige studie is `n baie volledige verwysing vir toekomstige studies op spesies van die genus Caligus van Suid-Afrika.
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Keywords
Copepod, Caligus, Ichthyoparasitic, Sea louse, Description, Synopsis, Key, Reference, South Africa, Caligus -- Classification, Fishes -- Parasites, Copepoda -- South Africa, Crustacea -- South Africa -- Classification, Dissertation (M.Sc. (Zoology and Entomology))--University of the Free State, 2004
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