Meeting Abstract

81.4  Monday, Jan. 6 11:00  Who makes the settlement cue for larvae of Phestilla sibogae? MENINZOR, D.; ASAHINA, A.; HADFIELD, M.G.*; University of Hawaii at Manoa hadfield@hawaii.edu

For more than 40 years, researchers in the Hadfield laboratory have made “metamorphic inducer” for larvae of the nudibranch Phestilla sibogae by soaking pieces of the nudibranch’s prey coral, Porites compressa, in a small volume of seawater and filtering the water. The assumption has long been that the inducer is a metabolite of the coral. But is it? As now well known, any hermatypic coral is a community of coral, symbiotic dinoflagellates and bacteria, any one of which might produce the small, polar metabolite that induces the nudibranch larvae to settle and metamorphose. This study attempts to eliminate all but one of the possible sources. To eliminate the dinoflagellate as a source, live coral pieces were maintained in full darkness for 24 hrs and transferred to fresh seawater where they were maintained in continued darkness. The last batch of seawater was filtered and subjected to a larval assay for metamorphosis. Despite a shutdown in photosynthesis, the inducer was still present, thus partly eliminating the dinoflagellates as the inducer source. To examine a possible role for bacteria in production of the inducer, corals were steeped in seawater containing one of seven different antibiotics, representing five different modes of action and the resulting seawater tested for induction. All preparations remained strongly inductive. Thus, results to date support the hypothesis that it is the coral itself whose metabolite is the inducer of recruitment of its prey nudibranch. However, examination of the coral extracts after each of the antibiotic treatments revealed the presence of live, colony-forming bacteria, so none of the treatments was absolute. Experiments are on-going with combinations and serial treatment of coral with multiple antibiotics.