Male crazy ants have two different sets of DNA in their bodies

Most male yellow loopy ants carry two separate units of DNA, ensuing from sperm and egg cells that don’t combine their genetic materials after fertilisation.

This implies the males are chimeras – people with some elements of the physique carrying one gene set, and different elements carrying one other. The males’ feminine offspring turn into both staff or queens, relying on the DNA within the sperm cell that fuses with the egg, whereas male descendants change into chimeras themselves.

The findings, which resolve a 15-year thriller concerning the insect’s genetics, reveal a mode of copy that, till now, was “unknown to science”, says Hugo Darras at Johannes Gutenberg College Mainz in Germany.

“There have been numerous loopy hypotheses to clarify what was occurring in these ants, however none was as loopy because the one we found,” he says.

Ants often reproduce both by sexual copy – a male’s sperm fertilising a feminine’s egg – or by clonal copy, that means the queen produces offspring with out the added genes of a second mum or dad. Usually, males outcome from unfertilised eggs and females from fertilised eggs. Normally, queens are genetically just like staff in the identical colony, however they turn into queens as a result of they’ve been given particular care and nourishment.

In 2007, scientists studied the genomes of yellow loopy ants (Anoplolepis gracilipes) and located, to their shock, that males had mixed genetics as if they had two parents. Six years later, one other crew found that each one the queens in a colony descended from the identical genetic line, and their worker sisters all descended from a very distinct, second line.

Intrigued by this puzzle, Darras and his colleagues sequenced the DNA of 53 yellow loopy ant queens and 91 staff collected from 14 areas in South-East Asia. The queens had been inbred, however the staff had a lot increased genetic range, he says. In different phrases, it appeared as if the queens had been born to oldsters of the identical lineage, whereas staff had been born to oldsters of various lineages – though the males that fathered all of them got here from the identical colony.

Assuming this meant the colonies included two lineages of males, the researchers then collected 574 males from the identical colonies because the queens and staff and sequenced the DNA of their legs. They discovered that among the males appeared to share a genetic line with the queens, whereas the others appeared extra carefully associated to the employees.

Which may have made sense if the males had resulted from fertilised eggs, says Darras, as a result of it could imply that they had two copies of every chromosome – one from every mum or dad. However his crew’s evaluation revealed that, like most ant, bee and wasp males, they solely had one copy of every chromosome and thus appeared to outcome from unfertilised eggs.

Perplexed, the crew then examined DNA from particular person cells in 20 of the males. They found that inside the identical particular person insect roughly half the cells had genes of 1 lineage, and the opposite half had genes of the opposite lineage. Wanting particularly at sperm cells, the crew discovered that one lineage – the one which led to staff – was way more ample than the opposite.

Additional evaluation revealed that the 2 lineages in these males did come from two mother and father, that means the males really resulted from fertilised eggs, however in contrast to in females, the nucleus of the egg didn’t fuse with the nucleus of the sperm. The males thus ended up with two completely different units of chromosomes, carried into completely different elements of the physique.

Looking back, the researchers realised that the overwhelming majority of yellow loopy ant males are in all probability chimeras – and that the DNA samples from the bugs’ legs solely confirmed the genetic materials of that specific leg, says Darras.

The ants might have advanced such a weird reproductive system due to an previous battle between lineages, he says. Particularly, if the worker-producing lineage all the time creates sterile females when the egg and sperm fuse, then it may guarantee its survival throughout generations if it may slip into an egg with out fusing. It then turns into a “egocentric” lineage by turning into the first DNA line within the sperm of fertile males.

“That is solely hypothesis although,” says Darras. “We’re simply firstly of our understanding.”