title: Interaction of conspecific cues in Balanus amphitrite Darwin (Cirripedia) settlement assays: continued argument for the single-larva assay.
abstract: Gregariousness in marine invertebrate larvae is an important regulator of benthic community structure. Previous laboratory settlement assays employing Balanus amphitrite Darwin cyprids found gregarious effects with as few as 3 larvae well(-1), together with modulation of such effects by chemical cues. Here, the relationship between settlement rate and larval density was rigorously tested through a fully randomised design. Seawater conditioned with adult B.amphitrite was tested alongside unconditioned seawater to determine the effect of a conspecific cue on gregarious interactions. Gregarious effects were detected in both conditioned and unconditioned seawater at < or =4 larvae well(-1). In untreated seawater, settlement rate increased linearly with larval density, levelling off at densities of > or =10 larvae well(-1). In conditioned seawater, settlement induction was observed at < or =4 larvae well(-1), switching to inhibition at 6, 8 and 10 larvae well(-1), before asymptoting at the highest densities tested. These results advocate the use of individual larvae in laboratory assays that investigate factors stimulating barnacle settlement.
authors.affiliation: School of Marine Science and Technology, Newcastle University, Newcastle upon Tyne, UK. peter.elbourne@ncl.ac.uk
authors.forename: Peter D
authors.initials: PD
authors.lastname: Elbourne
authors.forename: Robert A
authors.initials: RA
authors.lastname: Veater
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Clare
mesh_terms: D000818:Animals; D007814:Larva / Q000254:growth & development; D008675:Metamorphosis, Biological; D011156:Population Density; D012623:Seawater; D013045:Species Specificity; D001468:Thoracica / Q000254:growth & development*