INFESTATION OF AN INTRODUCED HOST, THE EUROPEAN GREEN CRAB, CARCINUS-MAENAS, BY A SYMBIOTIC NEMERTEAN EGG PREDATOR, CARCINONEMERTES EPIALTI

The recent introduction of the European green crab, Carcinus maenas, t o the west coast of the U.S. has provided an opportunity for host tran sfer of the symbiotic nemertean egg predator, Carcinonemertes epialti, from its native shore crab host, Hemigrapsus oregonensis to the exoti c C. maenas. Two surveys of C. maenas in Bodega Harbor, California, re vealed that, in March 1995 prevalence of C. epialti on C. maenas was s ignificantly lower than on H. oregonensis (11% versus 74%), but in Nov ember 1995 there was no significant difference between the 2 species ( 79% versus 98%). Only juvenile C. epialti were recovered from C. maena s in March 1995. However, in November 1995, ovigerous C. maenas were h arboring actively feeding adult worms. Prevalence in both crab species significantly differed from March to November. Laboratory studies rev ealed that C. epialti fed and reproduced on eggs of C. maenas. The fee ding rate of C. epialti on C. maenas eggs (2.5 eggs/trial) was not sig nificantly different from that on H. oregonensis eggs (3.6 eggs/trial) . Our findings suggest that this nemertean may have less host specific ity than was previously thought. If C. epialti causes brood mortality of C. maenas in nature, it could potentially impact populations of thi s exotic crab.