Effect of Tunicamycin on Growth and Mineralization of Balanus amphitrite amphitrite Darwin (Cirripedia)

Abstract

ABSTRACT The effects of the protein glycosylation inhibitor tunicamycin (TM) on skeletal growth, the rate of formation and morphology of the mineral growth increments, and the fine structure of the scutal plates of the barnacle Balanus amphitrite amphitrite Darwin were examined. If glycoproteins are important in control of crystal form and mineral microstructure, then by using TM to reduce the amount of glycoprotein synthesized by the mineralizing cells, one might expect to observe changes in fine structure by electron microscopy. Accordingly, 15-day-old barnacles, that had been grown on plastic coverslips, were exposed to various concentrations of TM for 10 days and the effects then analyzed by scanning electron microscopy. TM at 0.1 µg/ml inhibited shell growth. At 0.01 µg/ml TM, shell growth was retarded in one experiment but not in another. The normal rate of formation of a mineral growth increment, as calculated in two experiments, was 3.6 and 2.8 days, respectively, at 24° ± 1°C. This rate was reduced significantly by 0.01 µg/ml and 0.1 µg/ml TM; 1.0 µg/ml TM completely blocked increment formation. The bases of setae on the scuta increased in size, and the number of setae also increased in barnacles treated with 0.1 µg/ml TM for 10 days. However, other portions of the scuta revealed no characteristic differences in crystal microstructure.