ABSTRACT
A new cladoceran of the faviformis-group of the genus Chydorus Leach, 1816 (Cladocera: Chydoridae), characterized by a honeycomb-like sculpture of valves and head shield, is described from tundra lakes and ponds in North-East Russia. Morphology of the new species was studied using optical and scanning electron microscopy. Chydorus izvekovae sp. nov. differs from all other species of the faviformis-group in a narrow labral keel with elongated apex, and in a greater number of meshes on the valves and head shield. Other species of the faviformis-group in the Western Hemisphere are distributed in the tropical-subtropical zone, they also inhabit mostly shallow waters with well-developed macrophyte zone.
Subject(s)
Cladocera , Porifera , Animal Distribution , Animal Structures/anatomy & histology , Animals , Body Size , Organ Size , Russia , TundraABSTRACT
Information on the cladocerans of Eastern Palaerctic is limited, and remote islands of Arctic and Subarctic in this region are among inadequately studied territories, i.e. due to a very limited access to them. "Nearctic" Eurycercus longirostris is reported here for the first time from Bering Island and Wrangel Island. Also E. macracanthus is found to be common in Kamchatka Peninsula, while previously only a single population was known. We concluded that the Beringian land bridge played, together with glaciation in North America, important role in the evolutionary history of Eurycercus (Eurycercus), as it was earlier demonstrated for other cladocerans and other animals.
