"Fully-embryonated eggs are voided with the urine and hatch immediately on, or sometimes up to 24 hours after, entering water. The miracidium is an active swimmer and, where known, its body is covered with ciliated epidermal plates... the miracidium does not always seek its first intermediate host, a bivalve, occationally a univalve, mollusc, nor penetrate from the exterior, but is fortuitously carried into the mollusc with water flowing through the incurrent siphon of the host. On contact with the gills of the mollusc, the miracidium will rapidly penetrate, or lodge between, the gill-fragemnts, and there become a mother-sporocyst. This sporocyst gives rise to daughter-sporocysts, which in turn give rise to apharyngeal cystocercous cercariae of the macrocercous type. The cercaria escapes into water through the excurrent siphon of its host... almost any aquatic animal ingesting the cercaria will become the host of the metacercaria. Active gorgoderid cercariae are usually caught by predacious creatures, such as odonatan naiads, larvae of caddis-fly and aquatic beetles, whereas inactive cercariae may be swallowed by tadpoles and snails, but freshwater shrimps, crayfish, fish, and adult amphibians are also potential second intermediate hosts. Usually the cercariae penetrate the intestinal wall and encyst on the haemocoele or body-cavity of their hosts... Metacercariae excyst in the stomach of the final host, and the immature worms wander to the ureters and kidneys, there they undergo some development before they enter the urinary bladder to become adults" (Prudhoe and Bray, 1982).
Small to large non-spinous forms with a thin body-musculature. Suckers well developed; oral sucker subterminal; ventral sucker situated in anterior half of body. Pharynx absent in forms from fishes and amphibians; intestinal bifurication lies between the suckers; caeca extend to near posterior end of body. Genital pore median, near intestinal bifurication. Cirrus-sac and cirrus not developed. Seminal vesicle and ejaculatory duct present, pars prostatica feebly developed. Two testes arranged side by side symmetrically or obliquely, in middle third of body, simple or divided into large distinct follicles. Laurer's canal present. Vitelline glands forming two compact lobed or smooth masses situated between the intestinal caeca, in front of ovary. Uterus extends into hinder region of body. Eggs small, numerous and not operculated. Excretory vescicle a simple tube, straight or sigmoid, or occasionally Y-shaped... Adults found in body-cavity, ureters or urinary bladder of fishes, amphibians and reptiles.
Sources: Prudhoe, S. and Bray, R.A. 1982. Platyhelminth Parasites of the Amphibia. British Museum (Natural History) Oxford University Press.