Age-related settlement success by cyprids of the barnacle Balanus amphitrite, with special reference to consumption of cyprid storage protein

Newly molted (0-d-old) cyprids of the barnacle Balanus amphitrite Darwin were prevented from settling for 0 to 14 d at four different temperatures (25, 20, 15 and 5 degrees C treatments). The effect on settlement success of prolonging the cyprid lifetime was evaluated using a nitrilocellulose membrane assay. In addition, protein extract prepared from these cyprids was analyzed using gel electrophoresis to characterize the effect of age on protein content and composition. Settlement success was significantly affected for larvae aged at 25 (P < 0.001), 20 (P < 0.001) and 15 degrees C (P < 0.05), while differences in settlement success between age groups was negligible at 5 degrees C (P = 0.09). Settlement success of cyprids increased with time for up to 3 d (P < 0.001, Phase I), following which settlement success significantly declined (P < 0.001, Phase II). Temperature had no significant effect on settlement in Phase I (P = 0.17), Phase I), following which settlement success significantly declined (P < 0.001, Phase II). Temperature had no significant effect on settlement in Phase I (P = 0.17), but did enhance the decline in settlement success with age during Phase II (p < 0.001). Gel electrophoresis revealed a significant decline in the quantity of the cyprid storage protein CMP (Cyprid Major Protein) with increasing age at 25, 20 and 15 degrees C, but CMP levels remained constant at 5 degrees C. These results suggest that, upon molting to the cyprid stage, larvae may still require a settlement-competence attainment period. This may be achieved by CMP utilization during Phase I, depletion of which during Phase II may be responsible for reduction in settlement success with cyprid age such that remaining CMP stores can no longer support the production of adult structures following settlement.