Parasitic protozoa from marine and euryhaline fish of Newfoundland and New Brunswick. I. Peritrichous ciliates

Trichodina elizabethae n. sp. (which is commonly hyperparasitized by the suctorian Endosphaera engelmanni Entz), T. galyae n. sp., and T. domerguei (Wallengren) saintjohnsi n. subsp. are described from Newfoundland waters; the first two from the radiated shanny and lumpfish respectively, and the last from the mailed sculpin, lumpfish, and shorthorn sculpin. T. jarmilae n. sp. parasitizes the sea raven in the Bay of Fundy, New Brunswick. In both provinces, T. cottidarum Dogiel, sensu lato, occurs on shorthorn and longhorn sculpins. Two species of fish from brackish pools (the threespine stickleback in both areas; the mummichog in the Bay of Fundy) are often heavily parasitized by T. tenuidens Fauré-Fremiet. All the ciliates referred to were collected from the gills of their hosts, only two of which bore peritrichs other than trichodinids. One of these, Caliperia brevipes Laird, is found on the little skate in the Bay of Fundy and has been described elsewhere. The other, Scyphidia arctica Zhukov, is now reported from the longhorn sculpin in Newfoundland. Only five (16%) of 31 species of marine fish from Newfoundland bore trichodinids, as compared with nine (35%) of 26 from New Brunswick. However, four of the latter group had extremely light or sporadic infestations. Three of the rest, showing high incidence and heavy to extremely heavy infestations, were sculpins (Cottidae), as were three of the five Newfoundland hosts. Thus, while information is accumulating to suggest that marine fish trichodinids find optimum environmental conditions where mean seawater temperatures are not extreme (neither very warm nor very cold), certain fish are evidently more prone to infestation than others. This may well be due to varying ecological vulnerability to parasitization rather than to the operation of host specificity, an important question which, like that of environmental tolerances, merits early experimental attention. The paper includes a list of 61 species of Trichodina and the closely related Tripartiella and Trichodinella now known from marine and euryhaline fish, their validity being assessed on the basis of technique and the taxonomic criteria used.