Seasonal incidence and development of the cestodeCaryophyllaeus laticeps(Pallas) in the River Avon

Abstract

An account is given of the seasonal occurrence, maturation and population changes of Caryophyllaeus laticeps in its intermediate host Psammoryctes barbatus and in its definitive host Leuciscus leuciscus in the River Avon. Infective larvae were found in the tubificid in all months except August, but occurrence and maturation of C. laticeps in fish showed a clear seasonal periodicity. Infections were acquired between December and March, the parasite matured in April and May and disappeared by July. Maturation of C. laticeps appeared to be governed by changes in fish hormone levels. Changes in the parasite population in fish bore no relationship to the availability of infective larvae nor probably to the feeding behaviour of fish but were closely correlated with water temperature changes. The most important factor controlling the dynamics of the C. laticeps–dace system appears to be a temperature dependent rejection response to the parasites by dace, and it is suggested that a similar mechanism may operate to control the dynamics of other freshwater fish–tapeworm systems.I should like to thank the Avon and Dorset River Authority, and in particular Mr A. S. Grater, for their help in capturing the fish and for their ready co-operation.