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United States Department of Agriculture

Agricultural Research Service

Title: Occurrence and Morphology of Campula Oblonga (Digenea: Campulidae), in Cluding a Report from An Atypical Host, the Thresher Shark, Alopias Vulpinas (Bonnaterre)

item Hoberg, Eric

Submitted to: Journal of Parasitology
Publication Type: Research Notes
Publication Acceptance Date: October 10, 1997
Publication Date: N/A

Interpretive Summary: Identification among species of campulid trematodes, parasites of cetaceans and pinnipeds, has often been confused because of extensive variation in meristic characters. A specimen of Campulla oblonga, from an atypical elasmobranch host, was identified following detailed comparisons to specimens from harbor and Dall's porpoises. This is the first report of a campulid from a shark, and all previous reports have been from marine mammals. Meristic data were found to be of lesser importance than structural morphological characters in establishing the identity of this trematode. This record indicates the importance of guild associa- tions (phylogenetically unrelated hosts exploiting a common prey resource) in driving the potential for host-switching by parasites. The source of the infection is considered to have been marine fish infected with the metacercaria of C. oblonga. This information will be useful in identifying parasites of fish in marine aquaculture ponds in areas where marine mammals commonly occur.

Technical Abstract: New hosts records for Campula oblonga Cobbold, 1858 from the common dolphin, Delphinus delphis L., and from the thresher shark, Alopias vulpinus (Bonnaterre), are reported herein. Campulids have not been previously reported from a host which was not a marine mammal. Given the excellent condition and small size of the single specimen, and the diet and natural history of the thresher shark, we conclude that the trematode was acquired from the consumption of infected fish. Although the shark is an atypical host, the specimen of C. oblonga persisted and developed to maturity. Specimens of C. oblonga from these two hosts and from harbor porpoises, Phocoena phocoena (L.) and from Dall's porpoises, Phocoenoides dalli (True) are compared and a wide variation in ranges and values for characters are noted. The synonymy of Campula folium Ozaki, 1935 with C. oblonga is further supported by the apparent effect of the host on the size of the trematodes. Clinal variation is demonstrated for C. oblonga from P. phocoena in the north Pacific, with body size increasing from north to south. In regards to the degree of variation in measurements and the numerous factors which may impact these values, we recommend the use of qualitative morphologic characters for the identification of C. oblonga.

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