ASPECTS OF THE BIOLOGY AND PATHOGENICITY OF DICERATOCEPHALA BOSCHMAI (PLATYHELMINTHES, TEMNOCEPHALIDA), AN ECTOSYMBIONT ON THE REDCLAW CRAYFISH, CHERAX-QUADRICARINATUS

In commercial ponds, numbers of Diceratacephala boschmai, a temnocepha lid ectocommensal on the crayfish Cherax quadricarinatus, were lowest in spring (October-December) and highest in autumn (April). Worm numbe rs on host crayfish increased over the summer breeding period (Decembe r-April) when moulting stopped and decreased during the winter (April- October) when hosts were moulting. The number of worms correlated posi tively with host size. D. boschmai showed low host specificity in the laboratory. Worms developed and deposited eggs on five different speci es of Cherax (C. cuspidatus, C. depressus, C. destructor, C. tenuimanu s and C. quadricarinatus). Worms did not survive on the shrimp Macrobr achium spp. because of the grooming habits of these hosts. The health of crayfish was not significantly affected by infestations with D. bos chmai. Worms were not found in the branchial chamber and so were not a ssociated with respiratory distress. They ate damaged crayfish eggs bu t did not attack healthy eggs.