Researchers have sequenced the
genome of the endangered kiwi bird and identified several genetic changes that likely reflect the bird's adaptation to nocturnal life.
Researchers found several genes involved in colour vision to be inactivated and the diversity of odourant receptors to be higher than in other birds.
This suggests the kiwi's increased reliance on their sense of smell rather than vision for foraging.
The kiwi, national symbol of New Zealand, has rudimentary wings, no tail and a very long beak with nostrils.
The flightless bird is mainly nocturnal with a low basal metabolic rate and the lowest body temperature among birds. To date there has been little genetic information available for this species that might help scientists to understand their biology better.
An international team led by Torsten Schoneberg of the Institute of Biochemistry of the Medical Faculty at the University of Leipzig and Janet Kelso of the Max Planck Institute for Evolutionary Anthropology has now sequenced the genome of the brown kiwi (Apteryx mantelli).
Their analyses 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 odourant 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.
"Already French botanist and zoologist Jean Baptiste de Lamarck, who lived in the 18th century, hypothesised that evolution works in accordance with a 'use it or lose it' principle," said first author Diana Le Duc, from the University of Leipzig.
"It is therefore very likely that the kiwi lost its colour vision since this was no longer needed for its new nocturnal lifestyle," Le Duc said.
"The kiwi's sense of smell - which was required for foraging in the dark of the night - became more acute and the repertoire of odourant receptors increased adapting to a wider diversity of smells," Le Duc said.
DNA analyses of two kiwi individuals showed that according to first estimates there is little genetic variability in the population.
This could further endanger the survival of this species and will have to be taken into account when planning future breeding programmes, researchers said.
"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.
The kiwi belongs to a group of birds called ratites that also includes the extinguished New Zealand moa as well as flightless birds like ostrich, emu and rhea. Despite intensive protection efforts the kiwi is highly endangered.
The study was published in the journal Genome Biology.
