Effect of water temperature on larval development of the bivalve mollusk Tivela mactroides: evaluation in the laboratory and via simulation
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We describe laboratory experiments that monitored larval development of the marine bivalve Tivela mactroides at different water temperatures, describe and evaluate a model that simulates larval development and mortality, and use the model to simulate larval development and mortality at temperatures more extreme than those observed in the laboratory. The model represents a cohort of larvae that are introduced as trocophores and subsequently pass through straight-hinge veliger, umbo, and pediveliger stages before becoming juveniles. In the model, development rate of each stage is controlled by the accumulation of degree hours of 'adjusted' water temperature and mortality rates are controlled by current water temperature. Both in laboratory and simulated experiments at 22, 25, and 28C, ages at which T. mactroides developed from one stage to the next decreased with increasing water temperature, and there was no statistically significant difference between simulated and observed median ages at which larval development was completed (F = 1.47, df = 54, P = 0.23). The mean proportion of animals dying during each larval stage also decreased with increasing water temperature, even though hourly mortality rates within each larval stage increased with increasing temperature. Thus the effect of temperature on mortality is mediated primarily by the effect of temperature on development time. Simulated larvae failed to develop beyond the pediveliger stage at 20 and 18C, and failed to develop beyond the umbo stage at 16C. Although the current model predicts shorter development times and less mortality at temperatures up to 34C, excessive bacterial growth and reduction of feeding rate may occur as temperatures approach this upper lethal limit. (C) 2000 Elsevier Science B.V.
