INFLUENCE OF FOOD CONCENTRATION, TEMPERATURE AND SALINITY ON THE LARVAL DEVELOPMENT OF BALANUS AMPHITRITE

Influence of food concentration (0.5, 1 and 2 x 10(5) cell ml(-1) of S keletonema costatum), temperature (20 and 30 degrees C) and salinity ( 15, 25 and 35 parts per thousand) on the larval development of Balanus amphitrite (Cirripedia: Thoracica) was examined. The mortality rate a t 20 OC was lower than at 30 degrees C in general. Increase in food co ncentration from 0.5 to 1 x 10(5) cells ml(-1) improved the survival r ate, but this was not evident when food concentration was increased to 2 x 10(5) cells ml(-1). The results indicate that food availability a nd temperature jointly determine the energy allocation for metamorphic progress. It was observed that the influence of the tested variables varied with instar. At 20 degrees C the mean duration of the second in star exceeded 3 d and was much longer than other instar durations. The fourth, fifth and sixth instars and the total naupliar period showed that the effect of different salinities at given food concentrations w as negligible at 20 degrees C, while at 30 degrees C there was a marke d decrease in duration with increasing salinity.