Further expansion of the genus Cercopagis (Crustacea,Branchiopoda, Onychopoda) in the Baltic Sea,with notes on the taxa present and their ecology |
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Authors: | Gorokhova Elena Aladin Nikolai Dumont Henri J |
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Institution: | (1) Department of Systems Ecology, Stockholm University, 109 61 Stockholm, Sweden;(2) Present address: Department of Biology, Arizona State University, Tempe, U.S.A.;(3) Zoological Institute, Russian Academy of Science, 199034 St. Petersburg, Russia;(4) Laboratory of Animal Ecology, University of Ghent, B-9000 Ghent, Belgium |
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Abstract: | The onychopod cladoceran Cercopagis that recently invaded the Baltic Sea is reported from new zones of the northern Baltic proper. Because of successful survival and an expanding distribution range, the addition of Cercopagis to the Baltic fauna is considered to be permanent. What has previously been cited as Cercopagis pengoi encompasses the morphology of several other species, subspecies and forms. Either a number of morphologically similar species is present, or there is a number of spurious species in Cercopagis. The last hypothesis is favoured. The spatial distribution pattern of Cercopagis, as well as that of total zooplankton, was correlated with depth. Deep (>100 m) and shallow (<10 m) stations had significantly lower abundance than stations of intermediate depth (<100 m). An overview of the distribution of C. pengoi group in fresh and brackish waters suggests a high tolerance to environmental factors, but with differences among taxa. Due to this ecological flexibility, the colonization of the Baltic is not unexpected. Increasing salinity may restrict dispersal of cercopagids to the southern areas of the Baltic and to the North Sea, but inland lakes (e.g. in Sweden) present an ecological profile suitable for colonization. |
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Keywords: | Cercopagis invasion Baltic Sea depth temperature salinity morphological variations |
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