Influence of food concentration, temperature and salinity on the larval development of Balanus amphitrite

Abstract

Influence of food concentration (0.5, 1 and 2 x 105 cell ml^-1 of Skeletonema costatum), temperature (20 and 30°C) and salinity (15, 25 and 35‰) on the larval development ofBalanus amphitrite (Cirripedia: Thoracica) was examined. The mortality rate at 20°C was lower than at 30°C in general. Increase in food concentration from 0.5 to 1 x 105 cells ml^-1 improved the survival rate, but this was not evident when food concentration was increased to 2 x 105 cells ml^-1. The results indicate that food availability and temperature jointly determine the energy allocation for metamorphic progress. It was observed that the influence of the tested variables varied with instar. At 20 °C the mean duration of the second instar 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 was negligible at 20°C, while at 30°C there was a marked decrease in duration with increasing salinity.