The Rotifera of Hummock‐Hollow Formations in a Poor (Mesotrophic) Fen in Newfoundland

Abstract

Abstract Rotifers encountered from a poor (mesotrophic) fen, Avalon Peninsula of Newfoundland, are listed. Sixty‐four species and varieties, including 25 Bdelloidea and 39 Monogononta, were recorded. All but 4 of the reported species and varieties are new records for the Province of Newfoundland, while 27 are new records for Canada; of these, 13 are new for North America. A seasonal quantitative study of rotifer communities in the hummock‐hollow formations on the fen was carried out from August 1973 to October 1974. An average of 354 rotifers/cm 2 (17 species) was found per formation. Monogononta almost totally disappeared during winter, while the Bdelloidea decreased somewhat in numbers. The tops of hummocks contained mainly bdelloid species. The number of monogononts increased both in species and individuals on the slopes of hummocks and was greatest in the hollows, although the total number of rotifers was less in these areas than in the hummock tops. Some physical and biological factors affecting the rotifer communities were examined. Rotifers in these sites are not subjected to dessication. Predation was not an important factor. A quantitative sampling method was devised for procuring relatively accurate samples from living Sphagnum , and for extracting rotifers from these samples.