STRIKING that happy balance between giving and receiving in a relationship can be fraught with difficulty. But not, it seems, for hermaphrodite sea slugs. These gentle soft-bodied animals, blessed with both male and female genitalia, solve the battle of the sexes by engaging in “sperm trading”.
They donate sperm only on the condition that they receive it, so thwarting the male desire to fertilise and run. During sex, each slug inserts its penis into the other and one transfers a small package of sperm. The transfer of further sperm will only proceed if the other partner reciprocates by transferring a…
