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The shelled Magellanic Mollusca: with special reference to biogeographic relations in the Southern Ocean
Linse, K. (2002). The shelled Magellanic Mollusca: with special reference to biogeographic relations in the Southern Ocean. Theses Zoologicae, 34. A.R.G. Gantner: Ruggell. ISBN 3-904144-72-3. VII, 252 pp.
Part of: Fricke, R. (Ed.) Theses Zoologicae. ISSN 0934-8956, more

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    VLIZ: Mollusca MOL.270 [25473]

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  • Linse, K.

Abstract
    The present study focuses on the composition and distribution of the shelled Magellanic malacofauna and on the biogeographic patterns of shelled molluscs in the Southern Ocean. The origin of the Trochidae in the Southern Ocean is investigated on the basis of the recent biogeographic distribution and of the geological history of Antarctica. The Magellan region contains 210 shelled species of gastropods, 6 species of scaphopods, and 131 species of bivalves. During this study 42 species of gastropods and 10 species of bivalves were described, including the new descriptions of eight species and one genus and generic changes of two species: Anatoma clathrata (Strebel,1908) and Polinices patagonicus (Philippi, 1845). Within Gastropoda Iothia coppingeri magellanica subsp. nov., Margarella whiteana sp.nov., Orbitestella ponderi sp. nov., and Crenatosipho beaglensis gen.n. sp. nov. are new to science and within Bivalvia Philobrya crispa sp. nov., Crenella magellanica sp. nov., Cyclopecten multistriatus sp.nov., and Lyonsiella angelika sp. nov. Illustrated keys for the identification of the shelled benthic Magellanic molluscan fauna are presented. Figures of diagnostic characters and glossaries of technical terms used in malacology are provided to enable other workers to identify gastropods, scaphopods, and bivalves of the Magellan region. The shelled Magellanic malacofauna is characterised by: 1) a large number of very widely distributed families, 2) a large number of bipolar genera, 3) a latitudinally balanced systematic diversity, 4) a large number of endemic species, 5) a large number of small-sized species, 6) a large number of species and genera shared with the deep sea, and 7) a large number of species in families and genera that are diverse in Antarctica. From a geographical point of view, Magellanic gastropods share most species with adjacent regions on the Patagonian shelf, while the species composition of the bivalve fauna seem to be more related to the sub- and high Antarctic fauna. Biogeographic analysis of 1033 shelled molluscan species of the Southern Ocean show five subregions: the Magellan region (Magellanic mainland and Falkland Islands), South Georgia, the Kerguelen Islands, the West Antarctic region (Scotia Arc Islands, Antarctic Peninsula, eastern Weddell Sea), and the East Antarctic region (from Breid Bay/Gunnerus Bank to the Ross Sea, Marion and Prince Edward Islands). The horizontal distribution of the Southern Ocean trochids has been analysed on the basis of the world-wide distribution of these genera and their phylogenetic relationships, in order to reveal informations about the possible geographic origin and dispersal of these taxa. The phylogenetic-biogeographic analysis revealed that the origin of the Antarctic trochids can only be elucidated by the investigation of all taxa of the widely and sometimes world-widely distributited genera. Future studies should also cover behavioural, environmental characters, ancient and recent distribution patterns besides morphological characters.

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