CHEMICAL ECOLOGY OF THE SETTLEMENT OF BENTHIC MARINE-INVERTEBRATES

Most benthic marine invertebrates produce planktonic larvae that must locate a suitable substratum on which to settle. This review considers evidence for chemical cues that promote or deter the settlement of marine invertebrates, with a particular focus on the isolation and identification of naturally occurring inducers of settlement. Chemoreception by marine invertebrate larvae is discussed, with a review of information on the larval sensory organs involved in the perception of chemical cues and with comparisons of chemoreception by marine and terrestrial invertebrates. While there is considerable evidence for the existence of site-specific chemical cues that promote larval settlement, naturally occurring inductive compounds have been isolated and identified in only a few instances, and it is unclear whether any of these induce settlement under natural conditions. Conversely, a wealth of natural products have been characterised from extracts of unfouled sessile marine invertebrates to which an antifouling role has been ascribed, yet there is little evidence that these putative fouling inhibitors are released at concentrations that would influence settling larvae. The acknowledged importance of settlement and recruitment in structuring benthic communities warrants further interdisciplinary research on the identification, production, and perception of chemical signals in the marine environment.