120.6 Saturday, Jan. 7 Nitric oxide as a regulator of marine invertebrate metamorphosis: behavioural and molecular insights UEDA, N.*; DEGNAN, S.M.; The University of Queensland; The University of Queensland firstname.lastname@example.org
The nitric oxide (NO) signalling pathway plays multiple roles in biological systems, one of which appears to be regulation of the initiation of larval settlement and metamorphosis in diverse marine invertebrates. For several species representing divergent animal phyla, it has been experimentally demonstrated that reducing endogenous NO in larva via chemical inhibition of nitric oxide synthase (NOS) results in the induction of settlement and metamorphosis. These results, together with the antiquity and conservation of the NO signalling pathway, has led to the hypothesis that NO may be a universal negative regulator of marine invertebrate metamorphosis across the metazoa. We have tested this hypothesis in three tropical, southern hemisphere animals that represent three divergent animal phyla, and provide the first evidence of a contrasting role for NO in marine invertebrate metamorphosis – as a positive, rather than a negative, regulator. In each of our three taxa - a demosponge, a vetigastropod, and a solitary ascidian - the chemical application of NOS inhibitors resulted in repression of larval metamorphosis. Consistent with this, chemical application of an exogenous NOS donor alone was sufficient to induce metamorphosis of the sponge and ascidian larvae. We complement these settlement behaviour experiments by assaying both temporal (by quantitative RT-PCR) and spatial (by whole mount in situ hybridisation) expression of the NOS gene through larval competency and settlement. Our molecular data provides insights into the way in which chemoreception of environmental signals deriving from suitable benthic settlement substrates are mediated by the NO pathway to regulate metamorphosis in diverse marine invertebrates.