The Importance of Bacteria in Laboratory Experiments on Rearing the Larvae of<i>Ostrea Edulis</i>(L.)

Abstract

Preliminary experiments had suggested that the extent of the development of the bacterial flora which develops when sea water is confined in small vessels is an important factor in the laboratory culture of oyster larvae. In the experiments reported in this paper the growth and settlement of oyster larvae was compared in controls of normal sea water with those in which the bacterial flora was controlled with antibiotics. A concentration of 50 i.u. of the sodium salt of penicillin G per ml. suppressed bacterial growth for at least 2 days and, in a series of experiments using fifteen different broods of larvae, significantly (P&gt;0·001) more spat were obtained in those to which penicillin had been added than in the controls. A mixture of 50 units of penicillin G and 0·05 mg streptomycin sulphate was tried in three series of experiments. This completely suppressed the development of bacteria for at least nine days. In all three series many more spat were obtained than in the controls, but in only one series was there more spat than in the comparable penicillin experiment. It is suggested that when the bacterial population is very vigorous, or perhaps when certain species are present, this mixture will be more useful than penicillin alone. Experiments with other concentrations of penicillin, and with streptomycin and chloromycetin alone were not successful.