Taxonomy and distribution of a Crassicauda species (Nematoda: Spirurida) infecting the kidney of the common fin whale (Balaenoptera physalus Linné, 1758).

Nematode parasites were found in the kidney of common fin whales (Balaenoptera physalus Linné, 1758) captured in the North Atlantic Ocean (Denmark Strait area). These were identified as Crassicauda boopis Baylis, 1920, on the basis of morphologic and morphometric descriptions of this species' posterior end. The cephalic end of this parasite was described for the first time, however, and was indistinguishable from that of Crassicauda pacifica Margolis and Pike, 1955, a species whose posterior portion is unknown. It was also found that the eggs, size, host, and site of infection of both C. boopis and C. pacifica are indistinguishable. This established the synonymy of C. boopis with the more recently named taxon, C. pacifica. In light of previous descriptions of Crassicauda infections in balaenopterids, this implied that C. boopis should at present be considered a renal parasite of fin whales, and perhaps other rorquals, throughout the world's oceans.