The Taxonomic Status of Sarcotaces komaii and Sarcotaces verrucosus (Copepoda: Phylichthyidae) and Host-Parasite Relationships between Sarcotaces arcticus and Sebastes spp. (Pisces)

Abstract

Five species of rockfish (Sebastes spp.) were examined off southeast Alaska for Sarcotaces arcticus (Copepoda). Only Sebastes ciliatus was infected. Sarcotaces were compared to those found in 7 species of Sebastes collected off California and those from Molva dypterygia collected off Norway. As a result of these comparisons it is suggested that Sarcotaces komaii be synonymized with S. arcticus. It is possible that S. arcticus is synonymous with Sarcotaces verrucosus. Studies on aspects of the host-parasite relationship indicated that younger fish have a higher prevalence of infection and more multiple infections. There is no host-parasite size relationship. Seventy-five percent of the female parasites were associated with males, 85% had eggs and 10% nauplius larvae. Females ranged in size from 20 to 50 mm. Smaller specimens were represented by degenerated cysts. There was no indication of parasite-induced host mortality. The absence of infection in some species may be more a result of the hosts' natural history and geographic distribution than parasite specificity. In the course of a study on nearshore demersal fishes off southeast Alaska, numerous individuals from 5 species of rockfish (Sebastes) were examined for Sarcotaces (Copepoda: Phylichthyidae). Only Sebastes ciliatus was found to harbor Sarcotaces. This copepod, Sarcotaces arcticus Collett, 1874, was compared to specimens recovered from incidental collections of Sebastes spp. off southern and northern California. This report discusses some aspects of the host-parasite relationship between S. arcticus and S. ciliatus and suggests changes in the taxonomic status of Sarcotaces komaii Shiino, 1953. MATERIALS AND METHODS Five Sebastes spp. were collected off southeast Alaska from June to August 1981. Specimens were collected at 0 to 30 m by spear using SCUBA and hook-andline and at 80 to 120 m by longline and a jigging machine. Sebastes spp. (number hosts necropsied): S. ciliatus (411); Sebastes brevispinis (90); Sebastes ruberrimus (141); Sebastes entomelas (125); and Sebastes melanops (797). Hosts were aged by otolith ring count. The text will refer to small and large populations of S. ciliatus. The small populations are fish between 140 to 340 mm (3 to 12 yr old) and the large between 350 to 500 mm (12 to 27+ yr old). Although there is some overlap, the large populations were usually found in deeper water than the small. Comparisons between samples were standardized for host size, sex, Received 5 September 1984; revised 6 November 1985; accepted 10 December 1984. * School of Fisheries and Sciences, University of Alaska, Juneau, Alaska 99801. t School of Fisheries, University of Washington, Seattle, Washington 98195. seasons and depth of collection. Hence, not all comparisons have the same sample sizes. Infected Sebastes spp. off California included (host, number infected, collection, location, date): Sebastes auriculatus, 7, Tiburon, Sept. 1980; S. entomelas, 2, Moss Landing, Aug. 1982 and, 1, Point Pinos, Oct. 1982; Sebastes flavidus, 4, Moss Landing, June 1983; Sebastes melanops, 2, Monterey Bay, June 1982; S. rubrivinctus, 1, Bodega Bay, May 1981; Sebastes semicinctus, 1, Los Angeles, June 1982; and Sebastes serranoides, 2, Farallon Island, June 1981. The Molva dypterygia was collected by Dr. Bjmrn Berland, Zoological Laboratory, Bergen, Norway in September 1970. The tissues containing the Sarcotaces specimens were rehydrated in glycerine in March 1984. The northeastern Pacific Sarcotaces were compared to these specimens because the type specimen of S. arcticus was described from M. dypterygia (as Molva abyssorum) off Norway. Linear regression was used to assess the host-parasite size relationship and comparison between percentages to test prevalence of infections (Bailey, 1974). Parasites were formalin fixed at necropsy. Specimens to be examined by scanning electron microscopy were prepared by routine methods and examined on a NANOLAB 7 (SEM). All measurements were taken from formalin fixed specimens. The taxonomy of the Sebastes spp. is from Eschmeyer et al. (1983).