Understanding of factors influencing settlement (attachment and metamorphosis) of marine invertebrate larvae is of great importance in aquaculture and control of biofouling. The influence of two factors on settlement of larvae was assessed from two separate investigations: 1, the influence of age (endogenous factor) on cyprids of the barnacle Balanus amphitrite; and 2, the influence of a microbial film (exogenous factor) on pediveligers of the mussel Mytilus galloprovincialis.The settlement response of cypris larvae of B. amphitrite was found to be age-dependent. Older cyprids responded more readily to settlement factors than newly molted ones. In M. galloprovincialis, competent pediveligers settled in response to a microbial filmed surface but not to an unfilmed surface. Moreover, a factor with MW of less than 5000 dalton, derived from culture medium of a bacterial strain C1.1 (Pseudomonas-Alteromonas group), induced the settlement of M. galloprovincialis larvae. Thus, marine invertebrate larvae may require a period of competence acquisition, during which they are poorly responsive to settlement inducers. Upon acquisition of competence, larvae readily respond to external cues (e.g. microbial film, bacterial extracellular products).
(Japan Nus. Co. Ltd., Environm. Sci. Lab., Yokohama Kanazawa High Tech. Ctr., Kanazawa KU 5F, 1-1 Fukuura, Yokohama, Kanagawa 236, Japan)
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