LIFE CYCLE, DISTRIBUTION AND ABUNDANCE OF CARCINONEMERTES EPIALTI, A NEMERTEAN EGG PREDATOR OF THE SHORE CRAB, HEMIGRAPSUS OREGONENSIS, IN RELATION TO HOST SIZE, REPRODUCTION AND MOLT CYCLE

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Abstract
The epizoic nemertean, C. epialti, is a common egg predator of its intertidal crab host, H. oregonensis, from northern Baja California, Mexico, to Vancouver Island, British Columbia, Canada. Transmission experiments show that contact transfer of nemerteans can occur. In the field, nemertean prevalence and density peak in autumn at Bodega Harbor, California, USA. Ovigerous female hosts are more frequently infested than are male or nonovigerous hosts, although the mean density on ovigerous females is low. Nemertean density changes through the molt cycle, rising during post-molt, declining during intermolt and rebuilding to high densities during premolt. Large crabs have more nemerteans than do small crabs. The sternal-abdominal furrow is increasingly used as a site on large crabs. A model of C. epialti transmission and site occupancy is proposed, incorporating the influence of host size, sex, reproductive state, embryogenesis, molt cycle stage and molt cycle duration at Bodega Harbor.