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Biol Bull 75: 286-307. (October 1938)
© 1938 Marine Biological Laboratory
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PHYSIOLOGY OF REPRODUCTION OF OSTREA VIRGINICA

II. STIMULATION OF SPAWNING IN THE FEMALE OYSTER

PAUL S. GALTSOFF 1

1 U. S. BUREAU OF FISHERIES

1. Spawning of the physiologically ripe female O. virginica can be induced by exposing it to a constant temperature a few degrees higher than that of its environment or by quickly raising the temperature of the water from about 20° C. to 34-35° C. The second method, which appears to be more effective than the first one, gave positive results in 39.5 per cent of the tests.

2. Sperm of the oyster is a more powerful stimulant of sexual reaction for it easily induces spawning in oysters which do not respond to temperature stimulation. In the laboratory experiments, 55 per cent of the oysters which failed to react to increased temperature immediately responded to the addition of sperm.

3. The latent period of spawning reaction varies from 6 to 38 minutes and is independent of the concentration of sperm. A minimum concentration of sperm of about 100-150 spermatozoa per ml. of sea water is, however, necessary to induce a reaction.

4. The lowest temperature at which spawning in O. virginica was induced lay between 18.6° and 20.5° C. This threshold temperature is not, however, a critical temperature in the sense that it induces spawning or makes the stimulation by sperm effective in all physiologically ripe females. The lowest temperature level of the spawning reaction varies in different oysters depending on their responsiveness to stimulation.

5. The spawning reaction of O. virginica is specific in the sense that sperm of other genera of mollusks cannot provoke it.

6. The active principle of sperm suspension is thermolabile and insoluble in water. It can be extracted in 95 per cent ethyl alcohol and benzene.

7. The spawning reaction follows the "all-or-none" principle and once started cannot be inhibited or stopped. Rhythmical contractions of the adductor are considered to be due to impulses originating in the female organism during spawning. They are not ejection reactions caused by the presence of eggs in the pallial cavity.

8. The possibility of the action of sperm through absorption by the digestive tract or through the gills is discussed.






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Copyright © 1938 by the Marine Biological Laboratory.