Morphological and molecular observations on the status of Crassicauda magna, a parasite of the subcutaneous tissues of the pygmy sperm whale, with a re-evaluation of the systematic relationships of the genus Crassicauda.

Members of the genus Crassicauda (Nematoda: Spirurida) are parasites of the body tissues of whales and dolphins. Owing to the large size of worms and difficulties in the recovery of entire nematodes from the tissues of hosts, limited information is available on morphological descriptions of both male and female worms. Furthermore, there are currently no available sequence data for this genus to assist with such identifications. This paper describes for the first time features of the anterior extremity and the male tail of Crassicauda magna, suggesting that Crassicauda duguyi may be a synonym of this species. In addition, molecular data are presented for the genus for the first time suggesting that the genus belongs within the superfamily Acuarioidea rather than within the Habronematoidea, in which it is currently placed.