MECHANISM OF STARFISH SPAWNING. III. PROPERTIES AND ACTION OF MEIOSIS‐INDUCING SUBSTANCE PRODUCED IN GONAD UNDER INFLUENCE OF GONAD‐STIMULATING SUBSTANCE

Abstract

The gonad‐stimulating substance (GSS) contained in nerve extract of the starfish, Asterina pectinifera, acts on the ovary to produce an active substance responsible for oocyte maturation, meiosis‐inducing substance (MIS). MIS was successfully separated from GSS by gel‐filtration on Sephadex. The MIS fraction had also spawning‐inducing activity. Starfish testis also produced MIS under the influence of GSS. MIS production was shown in six starfish species. Although some species specificity characterizes GSS, this was not observed in MIS. Production of MIS in the ovary was found to begin immediately after the addition of GSS. The amount of MIS produced increased as the concentration of GSS was raised, and the longer the time of treatment with GSS, the greater was the amount of MIS produced. MIS was rather heatstable, insoluble in ether, benzene and petroleum ether but soluble in 95% ethanol. Its activity was not destroyed by pronase. Injection of MIS into the coelomic cavity induced gamete‐shedding in both male and female. However, MIS failed to induce spawning when applied from the outside of the body. Both GSS and MIS were found in the coelomic fluid only when the starfish were undergoing natural spawning. A mechanism of starfish spawning, based on the action of GSS and MIS is discussed. Copyright © 1970, Wiley Blackwell. All rights reserved