The mother pram bug uses her crab-like front claws to eat out the salp’s insides, inhabit its hollowed shell and lay her eggs inside. Once she exits, she propels the salp forward like a pram ...

That they’re both at risk of being killed at least lends some stakes to the fight, but when Eve is gravely injured (she has her jaw broken and her insides strewn about), it’s hard to get on ...