INFLUENCE OF TEMPERATURE ON THE PHYSIOLOGY OF GROWTH IN RUDITAPES-DECUSSATUS (L) LARVAE

Larvae of the butterfish clam Ruditapes decussatus obtained from a wil d stock were reared at 10, 16, 22 and 28-degrees-C from D-larval stage to metamorphosis. Growth in length and weight in addition to clearanc e and ingestion rates were studied. Growth efficiencies were calculate d for each temperature. Allometric equations relating feeding rates to weight and length were obtained. Growth rate steadily increased with increasing temperature during the experimental interval. Larval life c ould be divided into an initial mixotrophic period (from D stage to 14 0-150 mum length) followed by an exotrophic period (from 140-150 mum l ength to metamorphosis), according to their feeding activity. The clea rance rate (CR) in fully active feeding (exotrophic) larvae was an iso metric function of the ash free dry weight (AFDW), CR (ml . h-1) = 7.4 6 AFDW (mg). The effect of temperature on feeding rates was specially noticeable during the first few days of culture. Low temperatures (10- degrees-C) strongly inhibited feeding rates whereas high temperatures (28-degrees-C) yielded the maximum feeding activity. Gross growth effi ciency ranged between 33 and 78%, increasing with increased temperatur e and decreasing with larval development.