A study of the helminth parasites ofAnarhichas lupus(Perciformes: Anarhichadidae) in the North Atlantic

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Abstract
The North Atlantic wolffish,Anarhichas lupus, has a broad, relatively short gastro‐intestinal tract (0.55–1.05 of body length). The stomach‐like region has a high pH, suggesting a functionally stomachless condition. The ‘stomach’ is rarely parasitized by helminths. The gut pH tends to rise along its length as does the concentration of the ion Mg2+, while osmolarity and the ions Na+, Cl−and K+tend to decrease and Ca2+stays practically the same. The intestinal wall is deeply folded, particularly in the anterior region. The intestine commonly harbours several helminth species. The gall bladder and urinary bladder tend to be voluminous and both are commonly parasitized by digeneans.A. lupushas been recorded as harbouring over 30 species of parasitic helminth of which 10 are commonly found, often in large numbers. There is little overlap of parasite sites and there appear to be several empty niches. The parasites tend to fall into three categories, those stenoxenic to this genus of fish, those stenoxenic to other groups and accidental inA. lupus, and those forms which are euryxenic.