Bdelloid rotifers from lakes above 1700 m in western Italian Alps, with taxonomic notes on Dissotrocha macrostyla

Benthic and periphytic bdelloid communities from 16 alpine lakes from 1700 to 2850 m in above sea level in Sesia Valley (Piedmont region, North-western Italy), sampled during summer 2001 and 2002, were analyzed. Seventeen species were identified from these species-poor communities, with 1 to 6 species each. Dissotrocha macrostyla and Philodina citrina were the most common species, present in 10 lakes while 9 species were collected from one lake only. New morphological details from S.E.M. pictures of Dissotrocha macrostyla revealed that Dissotrocha macrostyla tuberculata (GOSSE, 1886) is only a seasonal morphotype. Its different appearance is due to the presence of locally distributed microscopic mucous bubbles (diameter 1.41 +/- 0.18 mum) on the trunk surface, produced by the rotifer itself under stressful conditions.