MECHANISM OF STARFISH SPAWNING. I. DISTRIBUTION OF ACTIVE SUBSTANCE RESPONSIBLE FOR MATURATION OF OOCYTES AND SHEDDING OF GAMETES

¹ Division of Physiology of Marine Organisms, Ocean Research Institute, University of Tokyo, Nakano-ku, Tokyo, Japan

1. The localization in the starfish body of the active substance responsible for maturation and gamete-shedding was determined by in vitro assay, using Asterias amurensis and Asterina pectinifera.

2. The active substance was found in the radial nerves at the same concentration in both male and female starfish, suggesting that the testis responds more readily to the action of the substance than does the ovary. The gamete-shedding substance seems to be identical in the two sexes.

3. As determined by the shedding reaction of isolated fragments of ovaries, the quantity of active substance (per dry weight of lyophilized nerve materials) was found to be uniform in various parts of the nerve ring-radial nerve system.

4. Tube feet and the body wall also contained considerable amounts of the active substance, although the content was several times lower than that of the radial nerves.

5. The shedding activity was also detectable in the extracts of some other regions of the starfish in which nervous tissue is plentiful: for example, cardiac stomach. However, the activity was much less than that of the radial nerves.

6. The active substance was found in the coelomic fluid only when the starfish were undergoing natural spawning. The coelomic fluid of starfish which were not spawning did not show any shedding activity, regardless of the condition of their gonads.

7. The significance of the appearance of active substance in the coelomic fluid in relation to the mechanism of starfish spawning is discussed.

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