DICLIDOPHORA NEZUMIAE SP. N. (MONOGENEA: DICLIDOPHORIDAE) AND ITS ECOLOGICAL RELATIONSHIPS WITH THE MACROURID FISH NEZUMIA BAIRDII (GOODE AND BEAN, 1877)

¹ Department of Biology, Southeastern Massachusetts University, North Dartmouth, MA 02747
² Virginia Institute of Marine Science, School of Marine Science, College of William and Mary, Gloucester Point, VA 23062

Diclidophora nezumiae sp. n. is described from the gills of the rat-tail fish Nezumia bairdii (Goode and Bean, 1877) taken from the environs of Hudson Submarine Canyon in the northwest Atlantic. The host-parasite relationships were studied in the host population. The new species is most similar to small species of Diclidophora having short bodies that taper to maximum width at the level of the first pair of clamps. It may be differentiated from other species by the following: clamps wider than long, noticeably decreasing in size posteriorly; lamellate extension of sclerite b does not fuse with sclerite c¹; unsclerotized diaphragm; a relatively small clamp sucker; 10-13 cirrus hooks; 18-30 intercecal, postovarian testes; unlobed seminal receptacle; filamented eggs; and body dimensions. Of 378 N. bairdii specimens examined, 106 (28%) were infected with 1-21 D. nezumiae per host. The parasite occurred most frequently on filaments of the first gill arch. Infected fish ranged from 61-428 mm in total length. They were collected at depths of 300-1900 m. Both incidence and intensity of infection were greater for hosts collected between 700-1000 m. Depth of capture of the host was more strongly correlated with fish abundance than with fish size.