No abstract

No abstract

Aspects of the life cycle of Asymphylodora tincae have been studied in a small lake near Amsterdam. Bithynia tentaculata, being the only snail species that was very numerous in the lake, was the first as well as the main second intermediate host; adult trematodes were found exclusively in the tench, Tinca tinca. A small part of the cercariae that penetrate into B. tentaculata was able to develop into progenetic specimens. A morphological description is given of the following stages of A. tincae: adult, egg, redia, cercariaeum, metacercaria and progenetic stage. The cercariaeum is identified as Cercariaeum paludinae impurae De Filippi, 1854.It is concluded that A. tincae is a species, capable of large variation regarding both morphological structure (e.g. body spination, size) and life cycle.

The natural infection of tench by Asymphylodora tincae in a lake was studied during one summer season. The incidence of infection was 57%, the mean intensity about 50. The distribution of the digencans along the host's intestine showed a maximum in the second half; this could be modified by the presence of other helminth species. Tench caught in early spring and kept in the laboratory retained their natural infection throughout the summer. Starvation of hosts during two months caused disappearance of the infection. Experiments showed that metaecrcariae, introduced into the intestine of tench, can excyst within one hour. In vitro, cysts in contact with tench bile opened within 15 seconds. Bile of several other cyprinid fisli species caused excystment within 60 seconds. Asymphylodora eggs appeared in tench faeces 7 to 10 days after infection. Progenetic specimens of A. tincae probably disintegrate in the intestine of the tench and their eggs arc passed out with the faeces.

No abstract