Significance of Temperature to Larval Survival and Length of Development in Balanus ebumeus (Crustacea: Cirripedia)

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Abstract
Mortality and length of development of B. eburneus nauplii was modified in laboratory culture by both temperature and concentration of unicellular algal food. At 20 and 25.degree. C mean larval survival was 63.5 and 66.0%, respectively, at an algal concentration of 1 .times. 105 cells ml-1. When the algal concentration was doubled to 2 .times. 105 cells ml-1, mean survival increased significantly to 92.5 and 96.5% at 20 and 25.degree. C, respectively (P = 0.002 at both temperatures). At 30.degree. C the difference in mortality related to algal food concentration disappeared and mean survival was > 90% at both concentrations. Over the interval of 20-30.degree. C, time to complete development to the cyprid stage decreased from a median of 7.6 to 3.9 days at 2 .times. 105 cells ml-1 and from 10.8 to 3.9 days at the lower food level of 1 .times. 105 cells ml-1. At 30.degree. C there was no difference between the 2 food concentrations in the median time to reach the cyprid stage. The hypothesis is proposed that increased algal cell concentration at 20 and 25.degree. C compensates for lower feeding efficiency and consequently results in better survival. To account for the similarity in development time at 30.degree. C at either food concentration, maximum possible food intake at 30.degree. C may have already been attained at 1 .times. 105 cells ml-1 and, therefore, the increase in the number of algal cells possibly would not further affect development rate to the cyprid stage. Experiments on feeding efficiency of B. eburneus nauplii in relation to temperature are needed to test this hypothesis.

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