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

Abstract

The mechanism through which external cues trigger the metamorphosis of marine invertebrate larvae is incompletely understood. Much of what we currently understand about signal transduction pathways in larval marine invertebrates is based on larval responses to neuroactive compounds, pharmacological agents, and elevated ion concentrations. This paper shows that the larvae of Crepidula fornicata can also be induced to metamorphose through brief exposure to thermal shock. Exposure of larvae to lower temperature regimens (e.g., a shift from 20 °C to 25 °C through 30 °C or from 25 °C to 28 °C or 30 °C) was not effective in inducing metamorphosis. By contrast, a 2-h exposure to 32 °C induced metamorphosis significantly above the control levels regardless of whether the larvae were reared at 20 °C or 25 °C. Thus, the absolute exposure temperature was more important than the magnitude of the temperature increase for inducing metamorphosis. Moreover, the larvae of C. fornicata became responsive to temperature shock several days after they became comparably responsive to a previously documented metamorphic trigger, elevated concentrations of potassium ions. Further exploration of the heat shock metamorphic response may improve our understanding of how the metamorphic pathway develops and works in this species.