Life bond

Schistosoma are copulating during their whole larval life.
They only separate so that the female puts down her eggs.

Unlike other trematods, they are dioic, which means male and female are different : the male is leaf-like and the female is worm-like.
They life in blood vessels, so the male rolls himself around his mate, who remains in his gynecoforous canal.
She goes for a small trip a bit further down in the body to lay some thousands of eggs, which have a small "horn" capable of digging a whole trough the vessel and into the intstine lumen or ureters: that's their way out of the body, in urine or faeces.
Eggs hatch in contact with water to release free-swimming larvae which actively seek out and penetrate a snail.
After multiplication within the snail, the parasites emerge and infect humans or other mammalian hosts by direct penetration through the skin.
It is amazing how they find out their way then from there to the vessels they look for (mesenteric or vesical plexus), and how they can swim, find the particular species of snail, and in the end find the human foot, or the animal mouth mucosa to penetrate in it!