Additional Observations on the Bionomics and Life History of Gorgodera amplicava Looss, 1899 (Trematoda: Gorgoderidae)

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Abstract
A study of the life history and bionomics of G. amplicava, from Cape Cod, Massachusetts, and s.-w. Missouri, has been made. The sphaeriid bivalve mollusk, Musculium partumeium, taken from the same natural habitats as M. securis and Sphaerium occidentale, has alone been found naturally infected, while M. partumeium used in successful laboratory controlled miracidial expts. has been maintained in continuous laboratory cultures for 4 years. Cercariae were ingested with food or in respiratory currents by tadpoles of several anuran spp. including Rana catesbeiana, R. clamitans, R. palustris and Hyla versicolor, and these amphibians were all satisfactory natural and exptl. metacercarial hosts. Moreover, the snails, Pseudosuccinea columella and Physa heterostropha, were additional natural and exptl. metacercarial hosts. Penetration and early encystment of metacercariae have been obtained in the larval urodele, Ambystoma maculatum, and the odonatan nymph, Enallagma sp. Encystment in vitro and ectopically in tadpole tails was accomplished. Metacercarial excystment and successful invasion of the urogenital systems (i.e., urinary bladder, meso-nephric ducts or oviducts) occurred in all anuran final hosts tried, including R. catesbeiana, R. clamitans, R. palustris, R. pipiens brachycephala, R. pipiens sphenocephala and Bufo americanus. Ambystoma maculatum is a suitable exptl. urodelan final host, while Trituruv v. viridescens is not. In the latter, normal excystment occurs but the young worms become trapped in fecal pellets and are eliminated. In the painted turtle, Chrysemys p. picta, metacercariae excyst in the small intestine but do not achieve independence of motion and are carried along peristaltically with the chyme until they are eliminated. All stages in the life cycle have been studied and descr. or figured. The miracidia are approximately 55 [mu]. long by 28 [mu] wide and are covered with 15 epidermal plates arranged in 3 rows. The anteroposterior pattern is 6, 6, 3. An apical adhesive and a pair of penetrating glands as well as 2 flame cells, germ cells and body cells are found internally. Experimentally produced mother sporocysts, located in the gills of the bivalve, have been traced from miracidial penetration to the liberation of daughter sporocysts. The miracidial epidermal plates persist as a loose, intact investing sporocyst cover for as long as 43 days after miracidial penetration. A unique flame cell metamorphosis has been found in mother and daughter sporocysts and in the adult. The large-tailed cercaria of G. amplicava agrees closely with the published descr. but has been found to be much longer than previously reported, with an average length of 13.9 mm. (12-17.4 mm.) for recently shed cercariae. The intrasporocyst development of the cercaria has been traced and a minutely graded developmental series of the adult in the frog host is given. Gorgodera minima Cort is shown to have been established on the basis of non-existent differences between it and young specimens of G. amplicava and is, therefore, suppressed as a synonym of G. amplicava.
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