On the life history of the nematode <i>Raphidascaris acus</i> (Bloch, 1779) in the natural environment of the River Bystřice, Czechoslovakia

Abstract

From April 1967 until July 1968 the life history of the nematode Rughiduscuris acus was followed in the natural environment of the River Bystfice. The incidence, intensity of infec‐tion, and also the maturation of the nematode in the definitive host ( Saimo truttu m. fario ) indicate that the life history of this parasite exhibits an obvious annual cycle, when adult egg‐producing female nematodes are present only from May until the beginning of July. This seasonal rhythm is largely due to changes in the food composition of the definitive host, although the effects of other factors cannot be excluded. In the River BystHce the main intermediate hosts of R. ucus are the bullhead ( Cottus gobio ) and the Siberian sculpin ( Cottuspoecilopus ) in the trout zone of the river and the stone Ioach ( Noernacheilus barbutulus ) in the lowland reaches. Larvae of the species Prodiamesa olivacca ( Diptera: Chironomidue ) were found to act as reservoir hosts for the second‐stage larvae of Raphiduscuris acus.