SEPARATING THE RESPIRATION RATES OF EMBRYOS AND BROODING FEMALES OF DAPHNIA-MAGNA - IMPLICATIONS FOR THE COST OF BROODING AND THE ALLOMETRY OF METABOLIC-RATE

Rates of oxygen consumption were measured in eggs, embryos, and neonates, as well as in adults of Daphnia magna with or without their broods. There was no detectable energetic cost of carrying a brood, and there was no apparent effect of brooding on the respiration of eggs and 1-2-d-old embryos. The respiration rates of eggs and early embryos were only about a third of those of neonates and adults and thus accounted for very little respiration in brooding females. Subtracting this embryonic respiration and measurement of oxygen consumption rates in isolated individuals over the whole range of body sizes in D. magna revealed that respiration rate is isometric with body mass, or nearly so, in this species.