Grillotia borealis sp n. (Cestoda : Trypanorhycha) from five species of Bathyraja (Rajiformes : Arhynchobatidae) in the North Pacific Ocean with comments on parasite enteric distribution

A new trypanorhynch cestode, Grillotia borealis sp. n., is described from t he spiral intestines of softnose skates of the genus Bathyraja collected fr om subarctic waters of the North Pacific Ocean: B. parmifera (Bean) (type h ost), B. aleutica (Gilbert) and B. interrupta (Gill et Townsend) from the B ering Sea and B. minispinosa Ishiyama et Ishihara and B. smirnovi (Soldatov et Pavlenko) from the Sea of Okhotsk off Japan. The new species is disting uished from other species of Grillotia by possession of the following combi nation of characters: four hooks per principal row, hooks 4(4') distinctly separated from hooks 3(3') of principal row, principal rows separated by 13 -15 intercalary hooks in 2-3 rows, hooks 2(2') and 3(3') change in form alo ng their respective files, hooks 1(1') do not change in form along the file , a broad band of microhooks on the external tentacular face, intermediary hooks are lacking, absence of a special basal armature, origin of the retra ctor muscle near middle of the bulb, average scolex ratio of 1 : 3 : 2 : 0. 1, and a hermaphroditic sac. Grillotia borealis consistently favoured the m ost anterior regions of the spiral intestine. Seventy-one per cent of 21 at tached worms occupied the most anterior chamber of the spiral valve and 52 per cent were embedded in the anterior surface of the spiral valve whorls. Factors which may limit the distribution of G. borealis within the spiral i ntestine of its host are discussed. Statistically significant differences o ccur in the mucosal morphology of B. aleutica and B. parmifera for villus l ength, diameter, spatial arrangement and number per unit area along the ant ero-posterior axis of the spiral intestine.