Demographic and temporal structure of an allele frequency cline in the mussel Mytilus edulis

Feeding rates, patterns of prey selection, and starvation tolerance were investigated for adult males and females of the cyclopoid copepod Corycaeus anglicus collected from the waters of Friday Harbor, Washington, USA. Selection by C. anglicus was determined largely by prey body-size, but was also affected by species and developmental stage. Small developmental stages of all prey species were fed upon at relatively low rates. The small calanoid species Acartia clausii was increasingly vulnerable to predation by C. anglicus as it progressed through successive developmental stages. Larger prey species, Pseudocalanus sp. and Calanus pacificus, were more vulnerable in intermediate stages, the C3 and N6 stages, respectively. Larger and smaller prey were characteristically attacked at different sites on their bodies; however, attack sites fell within a similar range of body widths, 130 to 170 m. Males of Corycaeus anglicus killed a maximum of 1.4 prey d^-1 when feeding on the optimally-sized adult females of Acartia clausii, which are approximately equivalent to its own body length. Males fed at approximately double the rates of females. Despite its small size and apparent lack of metabolic stores, this cyclopoid is highly tolerant of starvation conditions. Median survival time without food is at least 2 wk for both males and females. In its predatory behavior, C. anglicus employs an ambush-type strategy and seems to be adapted for infrequent encounters with relatively large prey.Contribution No. 1412 from the School of Oceanography, University of Washington, Seattle