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Abstract

The infection of black rockcod, Notothenia coriiceps, with digeneans in Admiralty Bay (South Shetland Islands ) within three months, from November 2007 to January 2008, is compared with the infection in the same three months in 1978/79, based on the examination of twenty fish collected in each month. Digenea found in 1978/1979 season were more numerous, and more diverse. Only five digenean species, Macvicaria georgiana , Neolebouria antarctica , Lepidapedon garrardi , Genolinea bowersi and Lecithaster macrocotyle , were recorded during both investigations, whereas three species, Neolepidapedon trematomi , Elytro− phalloides oatesi and Gonocerca phycidis , only in 1978/79. M. georgiana was the dominant species in 1978/79 and sub−dominant in 2007/08. Other digeneans were found in N. coriiceps in 2007/08 invariably together with M. georgiana. G. bowersi was the sub−dominant species in 1978/79 and the most common species in 2007/2008. Infections with Digenea belonging to other species were much less intense. Of the three rare or common species in 1978/79, the two, L. garrardi and L. macrocotyle , occurred in both seasons, whereas E. oatesi occurred only in 1978/79. Three remaining species were sporadic or absent. The overall results therefore demonstrated that infections with almost all digenean species were less strong in 2007/08 than three decades earlier, in 1978/79. Only data on M. georgiana , G. bowersi and L. g arrardi were statistically significant (p <0.05). Data on the occurrence of 14 species of Digenea in N. coriiceps from South Shetland Islands, South Orkney Islands, South Georgia, Argentine Is − lands, Melchior Islands, Adelie Land and Heard Island are given.
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Abstract

A comparison between the levels of infection with Acanthocephala of the fish Notothenia coriiceps in Admiralty Bay (South Shetland Islands, Antarctic) in 1978/79 and 2007/08 is presented. The same eight acanthocephalan species, three echinorhynchids maturing in fish, Aspersentis megarhynchus (dominant species), Metacanthocephalus johnstoni (subdominant species) and M. dalmori (common species), and five polymorphids maturing in mammals and birds, Corynosoma hamanni , C. pseudohamanni (both co−dominant species), C. arctocephali and C. bullosum (both common species), and C. shackletoni (rare species), were found. Echinorhynchids were more numerous in 2007/08 (mean abundance 46.54 versus 35.35 in 1978/79), whereas polymorphids more numerous in 1978/79 (mean abundance 74.35 versus 36.40 in 2007/08). The overall results therefore demonstrated that echinorhynchids were more numerous than polymorphids in 2007/08 and the reverse was true in 1978/79. This situation is dependent mainly upon the decreased infections with C. hamanni , C. pseudohamanni and C. bullosum , and to a lesser degree upon the increasing of infections with M. johnstoni . The decrease of the three Corynosoma spp. is possibly associated with the decreasing of populations of final hosts, seals, on the shore of Admiralty Bay in the vicinity of Arctowski Station.
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