Summary: | Seven harpacticoid species were found to be associated with sea ice collected during 5 Antarctic cruises of the RV Polarstern . Their distribution within the fast ice and pack ice zones of the Weddell Sea is presented. Whereas some individuals probably become entrapped into the ice only accidentally, at least 4 species are genuinely sympagic. These have evolved remarkable adaptations, as evidenced by field and laboratory studies of Drescheriella glacialis , which is by far the most abundant. Such adaptations include: the ability to penetrate deep into ice; a comparatively high salinity tolerance allowing it to endure large salinity fluctuations associated with ice crystal formation and melting; good swimming ability, necessary both for horizontal dispersal and for a planktonic intermezzo after annual melting of the sea ice. D. glacialis is the first polar non-vertebrate metazoan to be cultivated through its entire life cycle. Its life history suggests an r-strategy; this would be the first indication of such a trait in the polar environment. A new species of Drescheriella , on the other hand, exhibits resting stages (CIV-V) known to date only for Calanoida but not reported for Harpacticoida .
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