OXYGEN CONSUMPTION AND ITS INHIBITION IN THE DEVELOPMENT OF FUNDULUS AND VARIOUS PELAGIC FISH EGGS

¹ From the Biological Laboratories of the University of Rochester and the Marine Biological Laboratory, Woods Hole, Massachusetts

1. The respiratory rate of the Fundulus egg increases during the first two and one-half days of development. There is no temporary maximum rate with subsequent decline shortly after fertilization, nor is there evidence for any striking fluctuations in rate during the period studied.

2. The increases in cellular oxidation in the early development of Fundulus may be attributed to increases in cell number and in the amount of material incorporated in the active embryonic mass. These increases in rates of oxidation are not to be correlated with any particular embryonic stage.

3. The respiration of the developing Fundulus egg is cyanide-sensitive. The absolute value of the insensitive portion of the respiration remains relatively constant through four days after fertilization. Therefore, the respiratory increases occurring during development are almost entirely in the cyanide-sensitive respiratory system.

4. The earlier observations of Loeb on the relative sensitivity of the Fundulus and cunner eggs to anaerobic conditions are confirmed by the use of the respiratory poisons, NaCN and NaN₃. In their sensitivity to these poisons scup and mackerel eggs resemble those of the cunner.

5. Fundulus eggs before the end of gastrulation are capable of extensive development in high concentrations of NaCN and NaN₃ which completely and almost immediately inhibit the pelagic eggs. In lower concentrations the pelagic eggs can develop at decreased rates.

6. No differences in sensitivity to cyanide or azide have been found among the eggs at various embryonic stages studied in this paper.