The Oligochaetes and Their Actinosporean Parasites in Lake Sasajewun, Algonquin Park, Ontario

Abstract

There is little ecological information on actinosporean parasites and their oligochaete hosts. Between 1995 and 1997, about 14,100 oligochaetes belonging to 19 species were collected from Lake Sasajewun. The oligochaete fauna consisted of 5 tubificid, 10 naidid, 3 enchytraeid, and 1 lumbriculid species. The most widely distributed species in the lake were Limnodrilus hoffmeisteri, Dero nivea, and Stylaria lacustris, with L. hoffmeisteri being the most prevalent. The diversity and abundance of worms decreased with increased water depth. Four species, L. hoffmeisteri, Tubifex tubifex, Rhyacodrilus coccineus, and Lumbriculus variegatus, harbored actinosporean parasites and were distributed along shallow areas of the lake shore where the sediment was comprised mainly of clay-mud, with the shoregrass, Littorella americana. The actinosporean parasites of the oligochaetes belong to 25 forms of 8 collective groups. Triactinomyxon 'F' was the most prevalent form, whereas triactinomyxon, raabeia, and echinactinomyxon were the most speciose groups. The overall prevalence of actinosporeans was about 1%. Waterborne spores of different actinosporean forms showed distinct temporal patterns. Spores of triactinomyxon 'F' occurred throughout the sampling season, whereas spores of other forms occurred only at certain times. The presence of waterborne spores peaked from late June to August when water temperatures ranged from 18 to 24 C and coincided with the feeding and growing season of larval fish.