File:American malacological bulletin (1987) (17968707398).jpg

Title: American malacological bulletin
Identifier: americanmal4519861987amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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246 AMER. MALAC. BULL. 5(2) (1987)
Text Appearing After Image:
en at co ci ip Fig. 2. Biogeographical affinities of southern African opisthobranchs within the seven regions studied (CT - Cape Town, FB - False Bay, KN - Knysna, PE - Port Elizabeth, UM - Umgazana, DU - Durban, SO - Sodwana Bay, en - endemic, at - Altantic, co - cosmopolitan, ci - circum- tropical, ip - Indo-Pacific). opisthobranchs from the Gulf of Guinea and six species from the Ivory Coast. Edmunds (1977, 1981) conducted the most comprehensive studies of West African opisthobranchs and recorded 46 species from Ghana. The only other locality that has been studied is Senegal, from which Pruvot-Fol (1953) recorded 11 species and Bouchet (1971) listed an additional three species. Most of the coast of East Africa and the islands of Madagascar and Reunion have been poorly studied. Twenty- six species of opisthobranchs have been reported from Madagascar (Ev. Marcus and Er. Marcus, 1970), fourteen species from the Seychelles (Edmunds, 1972) and 35 species from Mauritius (Bergh, 1888,1889). The portion of East Africa that has been most thoroughly investigated is the coast of Tanzania, including Zanzibar (Eliot, 1902, 1903a, b, 1904a, b, c; Edmunds, 1969, 1970,1971; Edmunds and Thompson, 1972; Rudman, 1973a, b, 1977, 1978, 1979, 1980, 1981a, b, 1982a, b, 1984). Although about 200 species have been recorded in the literature, many more species occur there (Rudman, pers. comm.). Lack of distributional information from areas surround- ing a particular region, can lead to incorrect biogeographical conclusions, particularly in the case of erroneous assump- tions of endemism. Changes in the systematics of taxa can also alter biogeographical conclusions. For example, Aeolidiella saldanhensis Barnard and A. multicolor Macnae were thought to represent distinct endemic species in southern Africa. Re- cent taxonomic revisions (Gosliner and Griffiths, 1981) demonstrated that both species are junior synonyms of a widespread, circumtropical species. Another factor which should be considered in any biogeographical study is the potential alteration of natural distributional patterns by human intervention. The prey of opisthobranch gastropods are frequently colonial organisms such as hydroids, bryozoans and sponges, which are known to foul ships' hulls. Nudibranchs, often with their food and egg masses, can be transported long distances in this man- ner. These introduced species have limited ranges where they become established, and are generally restricted to harbors. There is no evidence that over time, they expand their ranges appreciably. There appears to be at least one example of the in- troduction of an opisthobranch species into South African waters by this means. The natural range of Catriona Colum- biana (O'Donoghue) is from the Pacific coast of North America to Japan (Baba and Hamatani, 1963). In South Africa it has been found only in Cape Town Harbor and its presence there is probably a result of international shipping (Gosliner and Griffiths, 1981).

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