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 and described in this week’s issue of the journal Arthropod Structure & Development.
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.
“Naturally occurring anomalies show what is possible,” said Gerhard Scholtz, of Humboldt University in Berlin, who led the new study on the weird crab.
Studying them “is like learning from mistakes. If things go wrong, and you understand the causes and mechanisms, you understand the causes and mechanisms for normal development as well”.
There are bad genetic mutations and fatal ones-which, by their nature, are weeded out of the gene pool. But other genetic tweaks stick around, because they offer some competitive advantage, something that improves survival.
