Aspects of the biology and pathogenicity of Diceratocephala boschmai (Platyhelminthes: Temnocephalida), an ectosymbiont on the redclaw crayfish, Cherax quadricarinatus

Abstract

In commercial ponds, numbers of Diceratocephala boschmai, a temnocephalid ectocommensal on the crayfish Cherax quadricarinatus, were lowest in spring (October-December) and highest in autumn (April). Worm numbers on host crayfish increased over the summer breeding period (December-April) when moulting stopped and decreased during the winter (April-October) when hosts were moulting. The number of worms correlated positively with host size.

P>D. boschmai showed low host specificity in the laboratory. Worms developed and deposited eggs on five different species of Cherax (C. cuspidatus, C. depressus, C. destructor, C. tenuimanus and C. quadricarinatus). Worms did not survive on the shrimp Macrobrachium spp. because of the grooming habits of these hosts.

The health of crayfish was not significantly affected by infestations with D. boschmai. Worms were not found in the branchial chamber and so were not associated with respiratory distress. They ate damaged crayfish eggs but did not attack healthy eggs.