Energy Metabolism in a Rapidly Developing Marine Fish Egg, the Red Drum (Sciaenops ocellata)

Rates of utilization of different lipid classes, glycogen, protein, and adenine nucleotides in the eggs of red drum (Sciaenops ocellata) were measured concurrently throughout embryonic development. Red drum eggs are small, pelagic, and very rapidly developing, going from fertilization to hatching in as little as 19 h at natural spawning temperatures. Wax esters comprised about 50% of the neutral lipid reserve along with triglyceride. Lipid was quantitatively the most important energy reserve supplying virtually all of the catabolic demand. Total lipid content decreased 30% from 23.6 to 16.6 mg/g during development. Glycogen decreased 53% from 0.279 to 0.103 mg/g. Protein did not contribute to catabolism. Total adenylates, primarily ATP, decreased from 564 to 271 nmol/g. Adenylate energy charge decreased from 0.87 to 0.58. Glycogen and lipid were used concurrently rather than sequentially during development. The rapid rate of development could be accounted for by simple thermal effects on metabolism rather than any unique biochemical adaptation. High concentrations of wax ester may be an adaptation for maintaining buoyancy at reduced salinities.