G protein‐linked receptors and induction of metamorphosis in Bugula stolonifera (Bryozoa)

Abstract

Abstract. Induction of metamorphosis in larvae of the marine bryozoan Bugula stolonifera was examined for potential roles of G protein‐linked cell‐surface receptors. Two compounds that modulate components of the G protein system were tested in a bath‐applied experimental design over concentrations of 10−8 to 10−3 M, plus a seawater control, and 2 controls to assess metamorphic competence (10 mM excess KCl and a biofilmed surface). The G protein activator Gpp[NH]p and the G protein inhibitor GDP‐β‐s did not affect rates of metamorphosis, under the conditions tested. We found no evidence that G protein‐linked cell‐surface receptors are the receptors of the metamorphic cue in this species. This negative finding parallels reports on a gastropod and a polychaete; by contrast, G proteins are involved in metamorphic induction in several cnidarians, a nematode, and barnacles. Thus, as no single model can account for induction across phyla, our results may serve to focus attention on identifying possible roles of the other 2 major classes of cell‐surface receptors in triggering metamorphosis in B. stolonifera and other invertebrates.