Paucivitellosus fragilis i sredescribed from the blenny, Salarias meleagris, found on beach-rock intertidally at Heron Island, Great Barrier Reef. The adult was also found in the mullet, Mugil cephalus and Crenimugil crenilabis at Heron Island, and Liza argentea at Brisbane.
Paucivitellosus differs from Bivesicula, Bivesiculoides and Treptodemus in having: (i) the vitellaria reduced to a single follicle on each side, (ii) two primary loops in the uterus, (iii) fully embryonated eggs in the terminal coils of the uterus, and (iv) the cirrus pouch orientated dorso-ventrally. The diagnosis of the family Bivesiculidae is emended.
The molluscan host at Heron Island is Cerithium penthusarus, in which cercariae develop in ‘fork-tailed’ rediae.
The cercaria is furcocystocercous and differs from known bivesiculid cercariae in having a protrusible glandular fold, within the mouth of the invaginated caudal chamber, by which the cercaria attaches to objects.
Evidence is presented for the view that the life-cycle is a two-host one, that there is no metacercarial stage, and that the cercaria is ingested by browsing.
I should like to thank the Great Barrier Reef Committee for the use of facilities at the Heron Island Research Station, where the field work was carried out. Professor H. W. Manter, University of Nebraska, generously donated all of the bivesiculid material that he collected in Australia, including adults of Paucivitellosus fragilis from the warty-lipped and sea mullet. Mr N. Milward and Mr H. Choat, of the Department of Zoology, kindly identified the fish hosts and furnished information on their feeding habits, and Dr D. F. McMichael, of the Australian Museum, kindly identified the snail host. Dr W. H. Coil, University of Kansas, kindly lent three paratypes (?) of P. fragilis. Thanks are also due to Mr R. J. Ballantyne for his able technical assistance in the collection and preparation of material.
The work was supported by a research grant from the University of Queensland.