An energy budget for individual barnacles (Balanus glandula)

Abstract

An annual energy budget was constructed for individual adult barnacles (Balanus glandula Darwin) for the first year after settlement. The production of body tissue, egg, shell, aquatic and aerial respiration, molting and faecal production was determined and consumption was derived from the summation of these budget items. To provide an estimation of the accuracy of the budget equation, energy budgets were constructed for three small groups of barnacles (n=40) kept under laboratory conditions, in which the budget items, including consumption, were determined independently. The results of the laboratory energy budgets indicated that consumption values derived from the summation methods for the three groups of barnacles were 7.4% higher and 16.2 and 15.6% lower than those determined by actual feeding experiments. The average consumption, assimilation and production of individual barnacles were estimated to be 699.5, 647.3 and 159.6 cal year−1, respectively. B. glandula has an exceptionally high assimilation efficiency (92.5% from the annual budget and 99.3% from the laboratory budgets) but a low gross production efficiency (22.8%) and net production efficiency (24.7%). A very large proportion of energy (67.4%) was lost in respiration. The second most important budget item was egg production (12.3%); followed in decreasing order by: shell production (6.6%)> production of body tissue (3.9%)>molting (2.3%).