GYRODACTYLUS-RAFINESQUEII SP-N (MONOGENEA) FROM ETHEOSTOMA-RAFINESQUEI (PERCIDAE) IN KENTUCKY, WITH A REVIEW OF THE TAXONOMY AND HOST-SPECIFICITY OF SPECIES OF GYRODACTYLUS FROM ETHEOSTOMATID FISHES IN NORTH-AMERICA

Gyrodactylus rafinesqueii sp. n. (Monogenea) is described from the tru nk surfaces, fins, and gonopodium of the Kentucky snubnose darter (Eth eostoma rafinesquei) from Russell Creek, Kentucky. The species has mod erately sized hamuli (56-65 pm long), a ventral bar with prominent (14 -18 pm long) anterolateral processes and a tapered membrane, and a rel atively large, slender marginal hook sickle (8.0-8.5 mu m long). An il lustrated comparison of the sclerites of G. rafinesqueii sp. n. to tho se of related species known from etheostomatid fishes (G. bretinae Wel lborn, 1967; G. etheostomae Wellborn and Rogers, 1967; G. nigrum Roger s, 1975; G. percinae Rogers and Wellborn, 1965) is presented. Gyrodact ylus rafinesqueii sp. n. resembles most closely G. percinae but has la rger marginal hook sickles and a dorsal bar devoid of a distinct media l notch. Within various rivers studied in Kentucky, G. rafinesqueii sp . n. parasitized E. rafinesquei, E. flavum, and E. simoterum, all thre e of which are species of darters classified in the subgenus Nanostoma /Ulocentra. Gyrodactylus rafinesqueii sp. n. did not parasitize specie s of darter of other subgenera living syntopically in the same habitat . In contrast, G. etheostomae parasitized hosts (E. barrenense, E. cae ruleum, E. spectabile, and E. stigmaeum) of 3 subgenera and thus has a much broader host specificity. Field collections revealed that G. raf inesqueii sp. n. and G. etheostomae can co-occur within the same stret ch of river but that they do not share hosts. Both apparently are depe ndent on darters, for neither parasite was found on cyprinid fishes sa mpled at the same sites. A key to species of Gyrodactylus from etheost omatid fishes and preliminary thoughts on the evolutionary history of gyrodactylids on these fishes are included.