On the morphology and life-history of Zoogonoides viviparus (Olsson, 1868) Odhner, 1902 (Trematoda, zoogonidae)

Abstract

The life-cycle of Zoogonoides viviparus (Olsson, 1868) Odhner, 1902 (fam. Zoogonoidae) was studied in the laboratory. The previously described cercaria from the prosobranch gastropod Buccinum undatum L. encysts both in nature and under laboratory conditions in brittle stars, polychaetes, lamellibranchs and prosobranchs. In Danish waters the brittle star Ophiura albida is the most important second intermediate host. The cercaria encysts both in the disc and between the joint of the arms of O. albida. If heavily infested the arms are shed.

The metacercariae do not grow inside the cyst, but their surface - observed in the stereoscan microscope - undergoes extreme changes. The microvilli around the mouth disappear gradually and the long spines on the posterior end of the cercaria shorten.

Juvenile Z. viviparus developed in small plaice and flounders fed with experimentally infected Lagis koreni and with pieces of Nereis diversicolor injected with metacercariae (Cercaria capriciosa Cuénot, 1892) removed from naturally infested O. albida.

Mature Z. viviparus are common in the rectum and posterior part of the intestine of plaice, flounders, dabs, and long rough dabs from the Øresund.

Previous finds of adult Z. viviparus from different fishes are discussed.