Laboratory culture of Balanus trigonus larvae by the method of B. amphitrite for establishing a multi-species settlement assay.

Abstract

In the study of antifouling, it is important to establish a method for culturing barnacle larvae for settlement assays. In the laboratory, the diatom Chaetoceros gracilis has been shown to be one of the best diets for raising the larvae of Balanus amphitrite. We applied this culture method to B. trigonus, supplying the larvae with C. gracilis at concentrations of 1, 3, 5, and 7×105cells/ml at 25°C. Larval growth in terms of rate of development to the cyprid stage, and the survival rates at different food concentrations, indicated that the optimal food concentration for B. trigonus was 5×105cells/ml. At this concentration, the larval survival rate on the sixth day following the start of culture was 84%, and about 71% of the larvae had developed to cyprids by then. Parallel observations on larvae of B. amphitrite showed that at its optimal food concentration of 3×105cells/ml, it took one day less to develop to the cyprid stage than did B. trigonus. In settlement assays using cyprids of each species and six-well multiwell plates, the percentage of settlement in response to a crude extract of adults of their own species for B. trigonus was 39±13%, whereas settlement on plates without the extract was 9±2%; the corresponding values were 44±12% and 20±10% for B. amphitrite. These results suggest that the larval culture and settlement assay methods established for B. amphitrite can also be applied to B. trigonus.