RESUMO
Laboratory-reared barnacle larvae were used to study natural products from whip corals. Biological assays used barnacle responses in behavioral assays and in larval settlement assays. Whip corals contained substances that were active in both assays. Substances inhibiting swimming and reversible attachment of barnacle larvae were found in an aqueous extract of whip corals. Low-molecular-weight substances inhibiting barnacle settlement were found in a methylene chloride extract of material soluble in aqueous methanol. Antisettlement activity was associated with substances with specific mobilities in several chromatography systems. Partially purified material was effective in preventing settlement at concentrations of less than 0.2 µ/ml. Settlement inhibition involves adsorption of the natural product to surfaces.
RESUMO
Cyprid larvae of Balanus cariosus settle preferentially on slate plates with a biota characteristic of the lower intertidal shore, and the cyprids also prefer plates with more algae. Cyprid larvae of Balanus glandula had the same preferences in two out of three experiments. We conclude that some component of the flora guides both species during settling and metamorphosis. Data on vertical distribution and fecundity of B. glandula show that the preference for the lower shore decreases fitness of B. glandula at the site of the settling experiments and at most other sites sampled in or near the San Juan Islands, though in some restricted habitats in the San Juans and extensive areas in the adjacent regions of Puget Sound a preference for the lower shore is appropriate. Extensive dispersal among sites is possible in the planktonic period of 2 to 4 weeks. This example supports the hypothesis that a cost to large scale dispersal is lower fitness at many sites within a species' range. In this case the cost is through poorer correlation between stimuli guiding choice of habitat and favorability of habitat.
