Distribution Patterns and Seasonal Occurrence of Rhabdostyla sp. (Peritricha: Epistylididae) on Dero nivea (Oligochaeta: Naididae)

Rhabdostyla sp. preferentially infested Dero (Dero) nivea in an alkaline bog stream from June 1982 to December 1983. Rhabdostyla occurred infrequently on two other species of naidid oligochaetes but were absent from nonliving substrates, algae, macrophytes and other invertebrates. Seasonal abundance peaks of Rhabdostyla occurred in October of 1982 and September-October of 1983 coincident with abundance peaks of D. nivea. Prevalence of host infestation ranged from 7.5-100% when infestations were present. Overall mean number of Rhabdostyla, 1 SE per D. nivea, was 4.8-i-0.2; means of individual sampling periods ranged from 2.0/worm to 13.1/ worm. Up to .36 Rhabdostyla were present on individual D. nivea. Frequency distributions were significantly (P