Heat shock induces metamorphosis in the larvae of the prosobranch gastropod Crepidula fornicata

The mechanism through which external cues trigger the metamorphosis of mari ne invertebrate larvae is incompletely understood, Much of what we currentl y understand about signal transduction pathways in larval marine invertebra tes is based on larval responses to neuroactive compounds, pharmacological agents, and elevated ion concentrations. This paper shows that the larvae o f Crepidula fornicata can also be induced to metamorphose through brief exp osure to thermal shock. Exposure of larvae to lower temperature regimens (e .g., a shift from 20 degreesC to 25 degreesC through 30 degreesC or from 25 degreesC to 28 degreesC or 30 degreesC) was not effective in inducing meta morphosis, By contrast, a 2-h exposure to 32 degreesC induced metamorphosis significantly above the control levels regardless of whether the larvae we re reared at 20 degreesC or 25 degreesC. Thus, the absolute exposure temper ature was more important than the magnitude of the temperature increase for inducing metamorphosis. Moreover, the larvae of C. fornicata became respon sive to temperature shock several days after they became comparably respons ive to a previously documented metamorphic trigger, elevated concentrations of potassium ions. Further exploration of the heat shock metamorphic respo nse may improve our understanding of how the metamorphic pathway develops a nd works in this species. (C) 2001 Elsevier Science B.V. All rights reserve d.