New species of Holopedium Zaddach, 1855 (Crustacea: Cladocera: Ctenopoda) from Greenland

The genus Holopedium remains poorly studied. Its nominal species H. gibberum was superficially described; later morphological differences of representatives of this taxon, especially in North America, have been recorded but not investigated in detail. The Greenlandic members of the taxon, listed for the first time in 1889, have never been precisely studied. Meanwhile, their comparative analysis resulted in the description of a new species, H. groenlandicum, which differs from H. gibberum s. l. in having a dorsally low shell and jelly envelope, shorter row of valve marginal spinules which are subdivided in groups, and comparatively longer postabdominal claws. Morphologically, the new species seems more primitive than H. gibberum. Absence of males and the presence of resting eggs may indicate a pseudosexual or another, poorly understood, mode of reproduction. Holopedium groenlandicum inhabits only permanent water bodies, mostly along the south-western and western coast of Greenland up to 71º N. This species is endemic to the island, and is most probably of relict nature.