THE EFFECTS OF OXYGEN POISONING ON THE POST-EMBRYONIC DEVELOPMENT AND BEHAVIOR OF A CHALCID WASP

¹ Department of Zoology, Cornell University, Ithaca, N. Y.

1. Experiments were conducted to determine the effects of high pressures of oxygen on the development and behavior of an insect, the chalcid wasp, Mormoniella vitripennis.

2. More than 10,000 wasps in five different stages of post embryonic development were compressed with 5 and 10 atmospheres of oxygen, nitrogen, or helium. Rapid compression and decompression were detrimental to chilled diapausing larvae but not to other stages. Although the high pressures of helium or nitrogen had no, or only slight, adverse effect, high pressures of oxygen were exceedingly toxic at certain stages of development.

3. The chilled diapausing larva was but slightly sensitive; about 12 hours at 5 atmospheres oxygen was required to reduce adult emergence by 50 per cent. Sensitivity reached a maximum during the early prepupal stage, when less than one hour of exposure to 5 atmospheres of oxygen reduced adult emergence by 50 per cent. Sensitivity decreased after pupation, and in the "pink stage," at the outset of adult development, about 14 hours of exposure were necessary to reduce adult emergence by 50 per cent. During the rest of adult development and throughout imaginal life, the sensitivity to oxygen again increased. The organ systems attacked by oxygen during these different stages were examined.

4. Exposing "pink stage" wasps to 5 atmospheres of oxygen for about 16 hours stopped development in the "black stage" just prior to adult emergence. Dissection of these "black stage" wasps revealed that they failed to emerge because oxygen poisoning had prevented their thoracic muscles from differentiating. The possibility that this block to muscle development resulted either from direct injury to the muscle cells or from damage to the trophic function of the nervous system was discussed, and an action on the nervous system was favored.

5. Exposure of "black stage" wasps just prior to eclosion caused an immediate and abrupt decline in respiration. Even when respiration returned to control levels within a day, the wasps remained paralyzed within their pupal cuticles and never emerged.

6. The first visible sign of oxygen poisoning in adults was loss of motor activity and coordination. After brief exposures, wasps often recovered completely, but longer exposures evoked permanent paralysis.

7. It was suggested that in the early stages of adult development from the "pink stage" onward, the trophic influence of nerve on muscle is disrupted by oxygen; and that just prior to emergence, and in the adult, impulse conduction and transmission are prevented by oxygen. The gradual increase in oxygen sensitivity during adult development and imaginal life appears to reflect an increasing sensitivity of the nervous system to oxygen poisoning.

8. In contrast to the oxygen-sensitivity of the nervous system, the epidermis of the developing adult was highly resistant to oxygen poisoning. However, prior to the initiation of adult development, epidermal differentiation was blocked by oxygen poisoning. The extreme sensitivity of the early prepupa compared with chilled diapausing larva or the "pink stage" wasp probably reflects the high sensitivity of dividing epidermal cells.