Peter Ellis

The animal world has many weird and wonderful ways of having sex. Some animals, such as snails, are hermaphrodites—able to make both eggs and sperm simultaneously. Some, such as wrasses and parrot-fish, initially hatch as male but transition to female in later life as they get older. Still others, including some lizard species, have dispensed with males entirely, and the females reproduce by parthenogenesis—laying fully fertile eggs without the need for sperm.