On the morphology and life history ofLecithaster gibbosus (Rudolphi, 1802) Lühe, 1901 (Digenea, Hemiuroidea)

Abstract

A previously undescribed cystophorous cercaria, which develops in the pyramidellid opisthobrachOdostomia eulimoides Hanley, was experimentally shown to be, the cercaria ofLecithaster gibbosus (Rudolphi, 1802) Lühe, 1901, a common digenean in the intestine of marine teleosts in the North Atlantic Ocean and adjacent seas. The immotile cercariae are ingested by calanoid copepods. Pressure by the mouth parts triggers delivery tube eversion, with consequent injection of the cercarial body into the haemocoel.Acartia sp.,Pseudocalanus elongatus andCentropages hamatus were experimentally infected, but the metacercariae became infective only inAcartia sp. The stickleback,Gasterosteus aculeatus, was the experimental final host. The infective cercaria ofL. gibbosus differs from that ofL. confusus Odhner, 1905, which develops inO. trifida (Totten), in that the former has a double-layered, swollen caudal cyst and a longer delivery tube. The cercaria, metacercaria and adults ofL. gibbosus are described by means of interference contrast, and scanning electron microscopy (SEM).