Some biochemical constituents of stage I and II nauplii of Balanus balanoides (L.) and the effect of anoxia on stage I

Some aspects of the energy-yielding metabolism of early larval stages of Balanus balanoides (L.) have been investigated by comparison of the concentrations of some biochemical constituents and certain enzyme activities in newly hatched stage I nauplii, stage I nauplii maintained for 4 h under anaerobic conditions, and stage II nauplii obtained after allowing stage I to remain in sea water in aerobic conditions for 24 h. The mean dry weight per nauplius was 1.02 μg for stage I and 0.78 μg for stage II under aerobic-conditions and it is thought that the main contribution to this weight loss is from protein (and some lipid) metabolized in order to maintain the vigorous swimming of the non-feeding stage I nauplius Carbohydrate and free amino-acid concentrations and the activity of malate dehydrogenase, lactate dehydrogenase, and fructose-1,6-diphosphate aldolase were similar in stage I and stage II. Protein, and to a lesser extent lipid, remain the major substrates used under anaerobic conditions but the decreases in these could not be accounted for by increases in metabolic intermediate compounds. A small increase in lactate and succinate may possibly account for the small amount of carbohydrate utilized under anaerobic conditions. The results are discussed in terms of current knowledge of the metabolism of invertebrates with particular reference to the effect of anaerobiosis.