Three-Eyed Crab and More Freaks of Nature

What has three eyes, two noses, and an antenna poking up like a little puppet from its head?
 That would be a unique specimen of the freshwater crab Amarinus lacustris, discovered in New Zealand. The “tri-clops” crab’s peculiar extra parts, and its malformed brain, are likely the result of a combination of bodily missteps. The crustacean has characteristics of a conjoined twin (duplicated parts: in this case, eyes) and a messed-up attempt at regeneration (crabs can regenerate an eye if one is damaged, but here an antenna popped up instead). Nature is no perfectionist; boo-boos happen.
 For scientists, these oddities are not just fun to study but valuable to understand.