Fewest chromosomes and fatherless ants

The jack jumper ant of south-eastern Australia has a nasty sting, can jump five times its own body length, and has the fewest chromosomes of any living thing.

So apparently I’m back to writing about the bizarre ants of southern Australia. And boy, today’s ant is a doozy.

The jack jumper ant is a menace. They are highly aggressive, with a powerful venom that can send you to the hospital (or, if you happen to be allergic, to the morgue). And they can jump up to seven and a half centimetres when worked up – not bad, given that they’re only one and a half centimetres long. And they get worked up very easily:

I know that’s not the clearest footage, but the creator’s cry of “crikey!” more than makes up for it.

The strangest thing about the jack jumper ant is its genetic code. Female jack jumper ants have a single pair of chromosomes; male jack jumper ants have just the one chromosome. That’s the fewest chromosomes possible in a living thing.

How is it that male ants can have half the number of chromosomes of female ants? Well, this is a peculiarity of ant, wasp, and bee reproduction. The queen lays eggs, and when those eggs have been fertilised by male drones they produce female queens or workers. But if the eggs are not fertilised, they still grow and hatch: that’s where the male drones come from.

Because female ants have two parents they get chromosomes from both; male ants only have a mother, which means they only get half the number of chromosomes. (This also means that male ants have no father and can have no sons.) The exact number of chromosomes depends on the species, of course, but jack jumper ants represent the minimum limit.

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