Annual cycle of Henneguya doori (Myxosporea) parasitizing yellow perch (Perca flavescens).

Henneguya doori Guilford, 1963 (Myxosporea) has an annual development cycle on the gills of adult Perca flavescens. The cycle involves a period of summer invasion, fall development of plasmodia and initiation of sporogenesis, winter completion of sporogenesis, and spring release of spores. An experiment revealed that rising water temperature in spring promotes cyst rupture and loss. The development of cysts is synchronized within individual fish and among members of the host population. As such, the parasite spends 8-9 mo in perch tissues to produce a single annual generation that culminates in a 4-6 wk period of spore dispersal. The parasite does not appear to be pathogenic. The observed cycle of H. doori repeated itself over 4 yr of sampling in Vinegar Lake, Nova Scotia.