Use of response surface methodology to determine optimum diets for Venerupis corrugata larvae: effects of ration and microalgal assemblages

Microalgal quantity and quality are major factors affecting bivalve larval growth. Effects of ration using bi-specific diet assemblages with varying proportions of the flagellate Isochrysis galbana and the diatom Chaetoceros neogracile were evaluated on Venerupis corrugata larval development. Response surface methodology was used to determine the optimal ration and better proportions of flagellate and diatom in the microalgal diet at different phases of larval development (early larva (<190μm, 10days), 12days, early pediveliger (15days) and young postlarvae (26days)). Maximum growth was obtained on day 10 for a diet of 22.5cellsμL−1 of I. galbana, which suggests that C. neogracile was not ingested or digested by early larvae. On day 12 a maximum in the experimental domain was predicted for a diet of 22.5cellsμL−1 of I. galbana and the lowest concentration of C. neogracile tested (30cellsμL−1), as C. neogracile reduced growth of the larvae at higher concentrations. On day 15, maximum growth was found at 42.6cellsμL−1 of C. neogracile and 27.9cellsμL−1 of I. galbana. During metamorphosis and early postlarval growth optimal ration was 70cellsμL−1 of a bi-specific diet in similar proportions to that previous stage of development. This novel approach to study bivalve larval nutrition allows the quality and quantity of the optimal diet to be determined.