Suborder TRANSVERSOTREMATA Olson, Cribb, Tkach, Bray & Littlewood, 2003

Museums

Regional Maps

Introduction

The Transversotremata is one of the smallest orders of trematodes. It contains just one superfamily, Transversotrematoidea Witenberg, 1944, and one family Transversotrematidae Witenberg, 1944. There are presently four genera and eight species recognised in the order (Cribb et al. 1992; Cribb 2002). Sexual adults live under the scales of marine and freshwater bony fishes.

The order is characterized by the site of infection, the transversely elongate body shape, the possession of a ventral sucker and pharynx, and the absence of a true oral sucker. All species have a cyclocoel.

Life cycles are known for freshwater species only. The egg embryonates to a miracidium hatches and swims to and penetrates a gastropod first intermediate host. The miracidium develops to a mother spororcyst which produces rediae which, in turn, produce either more rediae or cercariae. The cercariae are large and distinctive. The cercarial body is in the form of the adult worm and is easily recognizable as being that of a transverostrematid; the gonads are usually well-developed and sperm has been reported in the seminal vesicle. The tail is large and forked and also has large appendages at its base. The appendages have sensory pads that help recognise fish when the cercariae contacts it (Whitfield et al. 1975). The life cycle is completed when the cercaria slips under a scale and the tails detaches. Egg-production can start in as little as four days post-attachment. Just one life cycle is known for Australian transversotrematids (Cribb 1988). The classification here follows that of Cribb et al. (1992) and Olson et al. (2003).

History of changes