THE INFLUENCE OF FOOD CONCENTRATION AND TEMPERATURE ON GROWTH AND MORPHOLOGICAL-DIFFERENTIATION OF BLUE MUSSEL MYTILUS-EDULIS-L LARVAE

The relationship between growth rate, rate of morphological development, and length of larval life, was examined for larvae of the blue mussel Mytilus edulis L. The larvae were reared at phytoplankton (Isochrysis galbana, clone T-ISO) concentrations between 0.5 × 104 and 30 × 104 cells · ml-1 at either 12 or 16°C. Growth rates generally increased with increasing food concentration and were highest at the higher temperature; maximum shell growth rate was ≈ 8 μm · day -1. The number of days required for larvae to develop recognizable eyespots sometimes varied proportionately with changes in growth rate, but often did not; temperature was especially effective at uncoupling rate of growth from rate of morphological development. Maintained in clean glass dishes at 16°C, many eyespotted larvae survived until the end of the study, as long as 8 wk after they first developed eyespots (≈80 days after fertilization). Nearly 30% of those larvae that survived under these conditions eventually metamorphosed in the absence of filamentous substratum, suggesting that metamorphosis can be postponed at least 45 days at 16°C. Food concentration had no effect on 1. (1)the time elapsed between eyespot development and noninduced attachment; 2. (2) the average shell length of individuals that did attach; or 3. (3) the mean size of larvae remaining at the end of the study. © 1990.