MEPS 260:161-172 (2003) - doi:10.3354/meps260161
Composition and density of bacterial biofilms determine larval settlement of the polychaete Hydroides elegans
Shuyi Huang, Michael G. Hadfield*
ABSTRACT: Larvae of the polychaete worm Hydroides elegans settle and metamorphose in response to marine biofilms. Phylogenetic relationships among 4 marine-biofilm bacterial species identified by 16S rDNA sequences were not predictive of their inductive capacity. Two bacterial species separated by a genetic distance of 30% shared the greatest capacity for inducing metamorphosis in H. elegans. Two bacterial strains with only a 3% divergence in 16S rRNA gene sequences were very different; one strain induced metamorphosis strongly while the other one did not. The percent of larvae that metamorphosed correlated positively with bacterial density in either natural biofilms or biofilms composed of a single bacterial species. When results of tests across 4 bacterial species were compared, the most inductive bacterial species was effective in much lower biofilm densities than weakly or non-inductive bacteria. Evidence presented here indicates that the cue that triggers settlement and metamorphosis in larvae of H. elegans is not unique to a single bacterial taxon and is likely to be an insoluble, surface-bound material.
KEY WORDS: Biofilm bacteria · Larval settlement · Metamorphosis · Hydroides elegans
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