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 means 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 develop into chimeras themselves.
The findings, which resolve a 15-year thriller in regards to the insect’s genetics, reveal a mode of copy that, till now, was “unknown to science”, says Hugo Darras at Johannes Gutenberg University Mainz in Germany.
“There were lots of crazy hypotheses to explain what was happening in these ants, but none was as crazy as the one we discovered,” 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 father or mother. Generally, males outcome from unfertilised eggs and females from fertilised eggs. In most instances, queens are genetically much 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 blended genetics as if that they had two mother and father. Six years later, one other staff found that every one the queens in a colony descended from the identical genetic line, and their employee sisters all descended from a really 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 larger 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 – despite the fact that 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 a number of the males appeared to share a genetic line with the queens, whereas the others appeared extra carefully associated to the employees.
That might need made sense if the males had resulted from fertilised eggs, says Darras, as a result of it will imply that they had two copies of every chromosome – one from every father or mother. But his staff’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 staff then examined DNA from particular person cells in 20 of the males. They found that throughout the identical particular person insect roughly half the cells had genes of 1 lineage, and the opposite half had genes of the opposite lineage. Looking particularly at sperm cells, the staff discovered that one lineage – the one which led to staff – was rather more ample than the opposite.
Further 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 not like 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.
In retrospect, the researchers realised that the overwhelming majority of yellow loopy ant males are most likely chimeras – and that the DNA samples from the bugs’ legs solely confirmed the genetic materials of that individual leg, says Darras.
The ants might have advanced such a weird reproductive system due to an outdated battle between lineages, he says. In specific, if the worker-producing lineage at all times creates sterile females when the egg and sperm fuse, then it will probably guarantee its survival throughout generations if it will probably slip into an egg with out fusing. It then turns into a “selfish” lineage by turning into the first DNA line within the sperm of fertile males.
“This is only speculation though,” says Darras. “We’re just at the beginning of our understanding.”
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Source: www.newscientist.com