The Life Cycles, Intermediate Hosts, and Larval Stages Ofrhipidocotyle Transversale Chandler, 1935 Andrhipidocotyle Lintonihopkins, 1954: Life-Cycles and Systematics of Bucephalid Trematodes

The life-cycles of Rhipidocotyle transversale Chandler, 1935 and Rhipidoctoyle lintoni Hopkins, 1954 have been determined. Both species employ the same intermediate and final hosts; metacercariae in silversides, Menidia menidia, and adults in gars, Stronglyura marina. Branching sporocysts and furcocercous cercariae occupy the gonad and digestive gland of Lyonsia hyalina but can not be assigned with certainty to either or both species, because identifying morphological features are not yet developed. Adult and metacercarial stages of both parasites occur in the same host-species and it is probable that the larval stages of both are in L. hyalina.Recent studies on life-cycles of bucephalid trematodes demand revision of certain taxonomic allocations. The status of Distoma gracilescens, Monostomum galeatum, and Monostomum crucibulum, all described by Rudolphi (1819), are reviewed. Distoma gracilescens was transferred to Gasterostomum by Wagener (1852), to Rhipidocotyle by Diesing (1858), to Prosorhynchus by Lebour (1912), to Bucephalopsis by Nicoll (1914), and to Bucephaloides by Hopkins (1954). But Bucephaloides Hopkins, 1954 is a junior synonym of Prosorhynchoides Dollfus, 1929 and Distoma gracilescens becomes Prosorhynchoides gracilescens (Rudolphi, 1819) new combination. The life-cycle of the species was reported by Matthews (1974). Monostomum galeatum was transferred to Gasterostomum by Stossich (1898) and declared identical with Gasterostomum minimum Wagener, 1852 by Eckmann (1932). Accordingly, it becomes the type-species of Rhipidocotyle Diesing, 1858. Monostomum crucibulum was transferred to Gasterostomum by Gervais and Beneden (1859), and to Prosorhynchus by Odhner (1905). The life-cycle was reported by Matthews (1973a), and Stunkard (1974a) named it type of a new genus, Rudolphinus.The status of Bucephalus polyphemus von Baer, 1827 and Gasterostomum fimbriatum von Siebold, 1848, long regarded as specifically identical and the only bucephalid species in freshwater hosts in Europe, is equivocal. Bucephalus polymorphus is the name of a cercaria whose adult stage is yet to be disclosed and the larval stages of G. fimbriatum are unknown.Dujardin (1845) described small distomes from the intestine of Esox lucius taken at Rennes, France, as Distoma campanula. The species was redescribed and figured by Wedl (1858). Distomum fimbriatum von Siebold (1848) was redescribed by Wagener (1852, 1857, 1859). He (1858) suppressed D. campanula as a synonym of G. fibriatum, and recognized the latter species as the adult of B. polymorphus. Ziegler (1883) described mature bucephalid worms from E. lucius taken in the Ill River near Strassburg as G. fimbriatum and larval stages from Anodonta mutabilis as B. polymorphus. In a footnote, he predicated that if his specimens did not prove to be identical with G. fimbriatum, they should be regarded as a new species, Gasterostomum illense. A second bucephalid species from freshwater fishes in Europe was described by Kowal (1949), Vejnar (1956), and Kozicka (1959). It was designated Rhipidocotyle illense (Ziegler, 1883) Vejnar, 1956 by Kozicka (1959). Comparison with the descriptions of Distoma campanula show such agreement that the two must be regarded as identical and the name of the species is Rhipidocotyle campanula (Dujardin, 1845) new combination.Bucephalus haimeanus was described by Lacaze-Duthiers (1854) from cercariae found in oysters, Ostrea edulis, at Mahon in the Balearis Isles and in Cardium edule taken in l'étang du Thau near Cette on the south coast of France. There is no evidence that the cercariae from the two hosts and two locations are identical. Lebour (1912) reported Cercaria haimeanus from C. edule at Plymouth, but no infection in oysters. Matthews reported that cercariae from C. edule, identified as Cercaria haimeanus, developed into adults identical with Bucephalus minimum Stossich, 1887. The adult stages of the cercariae from European oysters, and of another species, Bucephalus cuculus, parasitic in the American oyster, Crossostrea virginica, are still unknown after more than one-hundred years.