PHYSIOLOGY OF REPRODUCTION OF OSTREA VIRGINICA

Abstract

Exps. were designed to study conditions provoking ovulation and discharge of eggs of ripe [female][female]. Spawning of physiologically ripe specimens was induced by exposing them to a constant temp, varying from 22.5[degree] to 30[degree]C or by quickly raising the temp. from about 20[degree] to 34-35[degree]C. The last method proved most effective giving positive results in 39.5% of tests. Of oysters failing to react to increased temps., 55% spawned upon addition of sperm, showing sperm to be a more powerful stimulant of sexual reaction. To induce spawning, however, a minimum conc. of about 100-150 spermatozoa per ml. of sea water, was necessary. Latent periods (101 exps.) varied from 6 to 38 min., and were independent of sperm conc. used. The threshold temp. under which stimulation by sperm was effective lay between 18.6[degree] and 20.5[degree]C, varying, however, in different oysters depending upon their responsiveness to stimulation. Sperm of various other mollusks and several hormones (known to stimulate [male] oysters) failed to induce spawning in [female][female]. Results indicated that the spawning reaction of this species is specific in the sense that sperm of other genera of mollusks did not provoke it. Attempts were made to determine properties of active principle of sperm suspension. Being insoluble in water, it was extracted in 95% alcohol and benzene. It was thermolabile, losing its power after 15 min. exposure to 54[degree]C. Upon inj. into pallial cavity of ripe [female][female], typical spawning reaction followed. The probable mode of action of sperm was discussed.