Why some crickets don't chirp any more

New York, If going to bed to the chirping of crickets is what you fantasize about during your vacation, then heading to the Hawaiian islands Kauai and Oahu may not be a good idea. Male crickets in these two islands have lost their ability to chirp.

They have developed flatwings as a result of separate, but simultaneous, evolutionary adaptation that started as a response to infestation by a deadly parasitic fly, says a new study.

The changes which allow the insects to avoid attracting a parasitic fly occurred independently over just 20 generations and are visible to the human eye.

The mutation has erased almost all the wing structures that help to make the sound, leaving the wings flattened but still airworthy.

The larvae of the fly Ormia ochracea burrow into crickets and grow inside, killing the host when they emerge a week or so later.

The researchers analysed the genomes of crickets from both islands using a technique that slices DNA into small fragments and then detects hundreds of thousands of genetic markers or small distinct regions of the genome.

The genetic markers associated with the flat wing are very different in the Kauai and Oahu populations.

"It means that different mutated portions of the genome cause males to be flatwing in either population," Nathan Bailey from University of St Andrews in Britain was quoted as saying.

The findings could help shed light on the earliest stages of convergent evolution -- when separate groups or populations independently evolve similar adaptations in response to natural selection, the study said.

The findings appeared in the journal Current Biology.

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