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Differences in Reproduciton
Observing the act of reproduction is an effective method of discerning between male and female sea urchins. Reproduction happens externally so the sex of the urchin can be observed without dissection. The female releases thousands of jelly-encased eggs and the male releases a cloud of milky white sperm in the same area. To observe this phenomena you will need a method of magnification.
Gonad Color and Characterisitcs
Sea urchin gonads secrete gametes (sex cells), which are dyed in a lab to reveal sex-indicating colors. Yellowness and redness as well as varying degrees of lightness are indicators of the sex. In cultivated males there is a decrease in both colors and an increase in lightness. In females the case is the opposite with decreased lightness and increases in both colors.
Gonad Fatty Acids
Analyzing the fatty acid content of male and female sea urchin gonads shows significant differences in fatty acid levels between the two sexes. Ovaries contain higher levels of fatty acids 14:0, 16:0, 16:1n-7, 18:2n-6, 18:3n-3 and 18:4n-3 than are present in testes. Testes show higher levels of 18:0, 22:1n-9, 20:4n-6 and 22:5n-3 than are present in ovaries.
Gonad Moisture Content
Examination of sea urchin gonads further reveals varying levels of moisture content between the male and female gonads. Male gonads have a markedly higher moisture content than females, though gonad wet weight between the two sexes is comparably similar. Males also have higher marks on the gonad index, which is gonad wet weight divided by body times 100.