Marked Changes in the Ribonuclease Activity of Mature and Immature Gonads of Sea Urchins Hemicentrotus pulcherrimus and Anthocidaris crassispina

It is generally impossible to sort male and female sea urchins before they reach maturity, i.e., while they are still in the immature stage. The ribonuclease (RNase) activity of the gonads of immature stage sea urchins consistently shows a constant activity level. Comparison of the RNase activity of the gonads of mature male and female Hemicentrotus pulcherrimus and Anthocidaris crassispina species at pH 5.0 showed that while its mean specific activity in the immature stage of female H. pulcherrimus increased rapidly from 7.35 to 62.79 units/mg, its activity in male H. pulcherrimus decreased from 7.35 to 1.90 units/mg. The same phenomenon was observed in A. crassispina. Based on its optimal pH, substrate specificity, and heat stability the RNase that exhibited these changes was determined to be an enzyme of the RNase T2 type. This enzyme is also thought to exert an influence on sex determination in sea urchins.