Kiwi bird genome decodes growth of nocturnal animals

An worldwide group of scientists led by the University of Leipzig, Germany, has sequenced the genome of the North Island brown kiwi (Apteryx mantelli) and identified several sequence changes that underlie the bird’s adaptation to a nocturnal lifestyle. They compared the sequence of two individuals and found that the diversity of their genomes appeared to be as low as that of inbred birds – a sign of the serious threat to the kiwi species as a whole, Dr. LeDuc explained in a statement.

“These adaptations seem to have happened around 35 million years ago, soon after their arrival in New Zealand, probably as a outcome of their nocturnal lifestyle”.

The gene responsible for black and white vision in the kiwi, rhodopsin, was found to be close to that found in other vertebrates, the researchers noted. This could further endanger the survival of this species.

Diana Le Duc, one of the authors, said the kiwi lost its color vision once that ability ceased to be an evolutionary advantage because it was active mainly at night.

Scientists say the changes could help explain kiwi nocturnality.

Mutations in genome from about 35 million years ago point to vision changes but also strong sense of smell. 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.

At the time the kiwi arrived other ratites, the moa, already inhabited New Zealand.

Researchers are particularly interested in the kiwi genome because of the bird’s unusual characteristics, which also include the lack of tail, rudimentary wings and a very long beak.

“Knowing the diversity of the kiwi population can be achieved much easier using the genome as a reference to which other sequenced kiwi birds can be compared and an informed decision can be made in regard to the need of mixing different populations to reduce inbreeding”, they added.

Le Duc said the changes in vision and smell were similar to adaptations found in nocturnal mammals. Nocturnal animals tend to have low metabolic rates and the researchers found genetic changes in the kiwi related to energy expenditure, reserves and metabolic processes.

Canterbury University genetics and conservation lecturer Tammy Steeves said he was confident the new findings would lead to a surge in genomics research in New Zealand.

“The genome of the kiwi is an important resource for future comparative analyses with other extinct and living flightless birds”, said study co-author Dr Janet Kelso of the Max Planck Institute for Evolutionary Anthropology.