Kiwi bird genome decodes growth of nocturnal animals

In a first, the genetic code of the endangered Kiwi bird, identifying several sequence changes that give insights into the evolution of nocturnal animals has been discovered.

Researchers from University of Leipzig and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, found several genes in Kiwi involved in colour vision to be inactivated and the diversity of odorant receptors to be higher than in other birds.

It suggests an increased reliance on Kiwi's sense of smell rather than vision for foraging.

"It is very likely that the kiwi lost its colour vision since this was no longer needed for its new nocturnal lifestyle," said first study author Diana Le Duc from University of Leipzig.

"The kiwi's sense of smell - which was required for foraging in the dark of the night - became more acute and the repertoire of odorant receptors increased adapting to a wider diversity of smells," Le Duc added.

Kiwi, national symbol of New Zealand, gives insights into the evolution of nocturnal animals have a number of features that make them interesting for study.

They only have rudimentary wings, no tail and a very long beak with nostrils. They are mainly nocturnal with a low basal metabolic rate and the lowest body temperature among birds.

The team has now sequenced the genome of the brown kiwi (Apteryx mantelli). Their analysis show genetic changes that likely reflect adaptation to nocturnal life.

Although mutations have inactivated some of the key genes involved in colour vision, the number of odorant receptor genes is expanded suggesting that the kiwi sense of smell is highly developed.

These changes happened about 35 million years ago which is after the kiwi's arrival in New Zealand, said the paper that appeared in the journal Genome Biology.

However, the DNA analyses of two kiwi individuals show that there is little genetic variability in the population. This could further endanger the survival of this species.

"The genome of the kiwi is an important resource for future comparative analyses with other extinct and living flightless birds," said computational biologist Janet Kelso of the Max Planck Institute for Evolutionary Anthropology.