A study of Gyrocotyle in the San Juan Archipelago, Puget Sound, U.S.A., with observations on the host, Hydrolagus colliei (Lay and Bennett)

Abstract

Simmons John E. & Laurie John S., 1972. A study of Gyrocotyle in the San Juan Archipelago, Puget Sound, U.S.A., with observations on the host, Hydrolagus colliei (Lay and Bennett). International journal for Parasitology, 2: 59–77. Over 400 specimens of the chimaeroid fish, Hydrolagus colliei, were examined for infection with Gyrocotyle spp. Only six uninfected animals were noted, and an infection incidence of 98·8 per cent recorded. Infection with Gyrocotyle parvispinosa comprised approximately 10–30 per cent of the total, dependent upon site of capture of the hosts. This species occupies a more posterior habitat in the valvular intestine than does Gyrocotyle fimbriata, and it escapes a moribund host animal somewhat more rapidly. Size of gyrocotylideans can be directly related to size of hosts from which they are derived, but there is little diffreence in this size relationship between the two species of worms, nor do the numbers of uterine egg capsules differ significantly between the two. Infections with two individuals comprised 68 per cent of those with G. fimbriata and 56 per cent of those with G. parvispinosa; single-worm infections constituted 21 per cent and 44 per cent of the infections with these two species, respectively. The incidence of single-worm infections was elevated to 42 and 83 per cent, respectively, in hosts less than 150 mm in length, and no evidence was obtained that infections are initiated with numerous worms. The possibility that ‘massive’ infections with Gyrocotyle might result from ingestion of free worms containing parenchymal postlarvae is discussed. Data on size class distributions of hosts collected at three sites, on weight-length relationships of the fish, and vomerine root lamellae counts, are presented.