MECHANISM OF STARFISH SPAWNING. II. SOME ASPECTS OF ACTION OF A NEURAL SUBSTANCE OBTAINED FROM RADIAL NERVE

Abstract

1. When a water extract of radial nerves of the starfish, Asterias amurensis, was locally applied to one part of an isolated whole ovary for an appropriate period and then small slits were made on the ovarian wall, intense discharge of eggs occurred only in the treated portion. 2. Eggs within the nontreated part of the ovary were observed to adhere to each other and to the gonadal wall by means of the follicle layer surrounding them. 3. Eggs within ligated ovarian fragments which had been treated with nerve extract lost their follicles and underwent maturation. These eggs were found to be freely movable. 4. Artificial spawning could be induced without using nerve extract; ovarian fragments immersed in Mg-free sea water released their eggs after a certain interval, while those treated with Ca-free sea water for an appropriate period spawn after subsequent addition of calcium. 5. Breakdown of follicles occurred within an ovary treated with calcium-free sea water. 6. Treatment with contraction-inducing agents such as potassium chloride and acetylcholine did not bring about spawning, although they caused countraction of isolated ovarian wall preparations. 7. Although the crude nerve extract caused muscular contraction in an isolated rat uterus, gel-filtrated nerve extract failed to induce contraction of either rat uterus or starfish ovarian wall. 8. These findings suggest that the action of the neural substance which is responsible for spawning acts within the ovary to induce breakdown of the follicles surrounding the oocytes. 9. Treatment with hyaluronidase and trypsin failed to induce spawning, suggesting that the intercellular cementing substance between the oocytes resists the action of these enzymes. 10. The neural substance failed to induce spawning when it was applied from the outside of the body.