Description of Gymnophallus somateriae (Levinsen, 1881) from Macoma inconspicua and diving ducks from Vancouver, Canada

Abstract

In the same clam host, the metacercaria of Gymnophallus somateriae differs from those of Lacunovermis conspicuus and Meiogymnophallus multigemmulus in the body shape and spination; small, irregular vitellaria; and lyre-shaped excretory bladder. The adult from diving ducks differs from Levinsen's description in the shorter posterior range of the uterus and shorter length of the eggs. The fusiform body, sucker ratio, location of the ventral sucker in the posterior third of the body, and bipartite seminal vesicle with large distal portion and smaller proximal portion are characteristic of the species. G. somateriae of Odhner (1900, 1905) belongs to a new genus and new species because of the size and location of the genital pore and will be described in the next paper. G. gibberosus Loos-Frank, 1971 is closely related to G. somateriae but has a ventral sucker in the middle third of the body, a uterus only in the anterior half of the body, and a proximal seminal vesicle smaller in diameter than the ventral sucker.