Family TRANSVERSOTREMATIDAE

Museums

Regional Maps

• Squamicolidae Pan, J-P. & Wang, W-J. 1985. An ectoparasitic, digenetic trematode Squamicola parvivitellaria ge. et. sp. nov. (Squamicolidae Fam. Nov.), found from freshwater fish in China. Acta Zootaxonomica Sinica 10: 344-349 [347].

Introduction

General
The family Transversotrematidae is a small family of some 8 species of digeneans in four genera. The adult worms and cercariae are easily recognised by the transversely elongated shape of the adult worms. Adults are ectoparasitic, being found beneath the scales of freshwater and marine fish, predominantly in Australian and Oriental regions, the Indian sub-continent and the Red Sea.

Life History
The life cycle of transversotrematids involves two hosts. Cribb (1988) notes that the first intermediate host of Prototransverotrema steeri Angel, 1969 is the hydrobiid snail Posticobia brazieri. Within the snail, the worm gives rise to one mother sporocyst and a single mother redia. The mother redia gives rise to daughter rediae and cercariae. The cercaria escapes from the snail and can infect a variety of native and introduced fish. The cercarial body is transversely elongated, resembling the adult form, while its tail is furcate and bears distinctive arm processes.

Collection Details
Adult transversotrematids can be obtained from their hosts by scraping the scales with a scalpel blade into a dish containing water. The worms should be collected into saline, not the natural surrounding medium of the host environment, because the environment of the parasites is essentially equivalent to an endoparasitic site.

A key to Australian genera, adapted from Cribb et al. (1992) is provided below. Detailed descriptions, redescriptions and keys to species can be found in Cribb et al. (1992).

Key to Australian Genera

1. Vitellarium follicular, profuse outside cyclocoel; eggs not embryonated in utero .......................................................................................................................................................2
Vitellarium restricted to inside lateral extremities of cyclocoel; eggs embryonate in utero and contain prominent eye-spotted miracidia.............................................Crusziella

2. Mouth on anterior margin of body; seminal vesicle tubular....................Prototransversotrema
Mouth mid-ventral; seminal vesicle bipartite................................................Transversotrema


References to Introduction

Cribb, T.H. (1988) Life-cycle and biology of Prototransversotrema steeri Angel, 1969 (Digenea, Transversotrematidae). Australian Journal of Zoology, 36: 111-129.

Cribb, T.H., Bray, R.A. & Barker, S.C. (1992) A review of the family Transversotrematidae (Trematoda : Digenea) with the description of a new genus, Crusziella. Invertebrate Taxonomy, 6: 909–935.

Diagnosis

Body flattened, transversely elongate or pyriform. Tegument spined throughout. Pair of eyespots present. True oral sucker always absent; oral flange present or absent. Ventral sucker median. Pharynx present. Oesophagus distinct. Cyclocoel present. Testes symmetrical, deeply lobed. Seminal vesicle tubular or bipartite with two parts separated by narrow duct passing ventral to cyclocoel. Cirrus pouch and pars prostatica absent. Male and female ducts join without specialisation at genital pore or at base of distinct sinus-sac. Temporary sinus organ may form. Genital pore on anterior margin at midline or, if genital pore on anterior margin, postero-dextral to midline. Ovary sinistral to left testis or between and anterior to testes, lobed or almost entire. Laurer's canal present, part dilated by sperm and vitelline remains. Proximal uterus forms uterine seminal receptacle. Uterus of varying length, may loop posterior to testes. Eggs large; capsules either thick-walled and tanned, containing unembryonated zygote, or thin-walled, clear and containing embryonating miracidium. Vitellarium consisting of widely distributed follicles, of 2 small symmetrical fields of follicles inside lateral extremities of cyclocoel, or of 2 single masses inside lateral extremities of cyclocoel. Excretory pore at small notch in midline of posterior margin. Bladder narrow distally, broad proximally. Life cycle known for two species only: cercariae develop in rediae in prosobranch gastropods; cercariae with furcate tails bearing distinctive arm processes at their bases; cercariae in form of nearly fully developed adult that attaches directly to skin of fish and matures to adult beneath scales without intervening metacercarial form. Adults known from beneath scales of wide variety of families of marine and freshwater fish in Africa, India, Asia, Australia and Indian and Pacific Oceans.

History of changes