Settlement of Pacific calico scallop larvae (Argopecten ventricosus, Sowerby II, 1842) on their predator, the black murex snail (Hexaplex nigritus, Philippi, 1845)

摘要

We examined settlement choices of Pacific calico scallop larvae (Argopecten ventricosus = circularis, Sowerby II, 1842) on eight substrates including live black murex snails (Hexaplex nigritus = Muricanthus nigritus, Philippi, 1845), an endemic neogastropod of the Gulf of California and a common predator of A. ventricosus. We found that A. ventricosus settled on black murex snails with epibiota on their shells in higher densities (6 larvae/cm(2) +/- 1.0) when provided a variety of settlement substrates (P value < 0.0001). In a second experiment, we investigated factors that may contribute to settlement of A. ventricosus on black murex snails such as (1) substrate complexity of murex shells, (2) substrate complexity of murex egg cases, (3) chemical cues from murex snail mucus, and (4) presence or absence of epibiota on black murex snails. Argopecten ventricosus settled in greater densities on black murex snails with epibiota on their shells (8 larvae/cm(2) +/- 1.5) than other substrates (P value < 0.0001). Larval settlement was 4 larvae/cm(2) (SE = 0.8) on cleaned murex snails where epibiota had been removed, but settlement was only 0.2 larvae/cm(2) on murex shell fragments, suggesting that the complexity of the shell alone is not what attracts scallop larvae to settle on black murex snails. Settlement was always much higher on living snails than on other substrates which had no more than 1 or 2larvae/cm(2). Presence of epibiota on the shell appears to be an important factor for settlement of scallops, and it is probable that scallop larvae do not perceive murex snails as a potential predator but as reef structure.