Date of this Version
During July-September 1993 and May 1996, a survey of the metazoan parasites of 817 elasmobranchs from the Gulf of California, representing 42 species, was conducted at 14 sites along the western portion of the Gulf of California. Elasmobranchs were obtained from local commercial fishers. In this paper, we report all digeneans collected during the survey, excluding the gorgoderids, which will be presented in a subsequent paper. Four species from three hemiuroid families were collected, none of which was known previously from the Gulf of California. Syncoelium vermilionensis sp. n. (Syncoeliidae), a species that differs most notably from its congeners by having more testes, is described from the gills and gill arches of Mobula thurstoni and M. japonica. Paronatrema vaginicola (Syncoeliidae) is reported from the cloaca, gill arches, and buccal cavity of Prionace glauca (blue shark) and Alopias pelagicus (pelagic thresher shark). These hosts represent new host records for the species, and this is the first record of the parasite from the eastern Pacific Ocean. Observations of uterine morphology in S. vermilionensis and P. vaginicola along with published descriptions of other species in Syncoeliidae indicate that all members of this family obtain a diagnostically thick outer shell of their eggs within a thick-walled section of the uterus rather than in the ootype, as in other digenean groups. Otodistomum veliporum (Azygiidae) is reported from the stomach of Squatina californica (angel shark), from the body cavity of Mustelus helei (brown smoothhound), and from the stomach of two species of horn sharks (Heterodontus francisci and H. mexicanus). Mustelus henlei, H. francisci, and H. mexicanus are new hosts for the parasite. Ptychogonimus megastoma (Ptychogonimidae) is reported from the stomach of Mustelus lunulatus (sicklefin smoothhound) and M. californicus (gray smoothhound). Both are new hosts for the parasite, and this is the first report of the parasite from the eastern Pacific Ocean.