A Method for Measuring Growth in Living Barnacles (Crustacea: Cirripedia)

Abstract

A buoyant-weight method is described for the non-destructive estimation of fresh weight, total dry weight, shell weight and dry weight of organic matter in living barnacles Balanus amphitrite amphitrite Darwin. The method involves developing regression equations relating weight in air of these parameters to the buoyant weight of living barnacles in sea water. Buoyant weights of barnacles can then be used with the regression equations to obtain the weight in air of these consitituents, making possible the measurement of rates of shell growth and growth in dry weight without disturbance to the living animal. The method has been developed for the analysis of groups of juvenile barnacles cultured on coverslips, ranging in total dry weight from 1 to 60 mg, and for single mature individuals from 75 to 800 mg total dry weight. The buoyant-weight method has been used to measure shell growth of 2–3 mg d-1 in barnacles of 48 mg mean initial total dry weight cultured at 28°C.