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Kiwi genomes explain the unusual characteristics of an
endangered bird
The kiwi bird’s unique nocturnal behaviour is linked to some altered genes
that eliminate color vision and others that modify its sense of smell,
according to the first kiwi genome published in the open access journal
Genome Biology.
Kiwis are endangered, ground-dwelling birds endemic to New Zealand.
They are the smallest and only nocturnal representatives of the ratites – a
group of flightless birds that includes the ostrich and emu. They are also
unusual in that they have a highly developed sense of smell, low
metabolic rate, and enormous eggs in relation to body size. However, the
genetic adaptations that underpin their unique traits have so far not been
well understood.
A team of researchers sequenced the genomes of two North Island brown
kiwi. Not only was the kiwi genome found to be one of the largest bird
genomes sequenced to date, but the team also identified evolutionary
changes in its genome that help explain the bird’s unique adaptations to
nocturnality – a behavior found in fewer than 3% of all bird species.
Lead author Diana Le Duc from the University of Leipzig and the Max
Planck Institute for Evolutionary Anthropology, Germany, said: “We’ve
seen for the first time that kiwi lack color vision, and that their olfactory
receptors can probably detect a larger range of odors which may be
essential for their night-time foraging. These adaptations seem to have
happened around 35 million years ago, soon after their arrival in New
Zealand, probably as a consequence of their nocturnal lifestyle.”
The gene responsible for black and white vision, rhodopsin, was found to
be similar to other vertebrates. However, the team identified mutations in
the green and blue vision receptor genes, which could render blue and
green color vision absent in the kiwi.
The genomic changes in kiwi vision and smell are consistent with changes
that are thought to occur during adaptation to nocturnal lifestyle in
mammals. The researchers estimated the onset time of these changes to
around 35 million years ago, suggesting that the kiwi adopted its
nocturnal lifestyle shortly after the arrival of its ancestor in New Zealand.
At the time the kiwi arrived other ratites, the moa, already inhabited New
Zealand. These now extinct birds, of which one species was over three
metres in height, are thought to have monopolized food sources during
the day, forcing the kiwi to adopt an alternative nocturnal lifestyle.
Kiwi are unique among birds in having nostrils present at the end of their
long beaks and it has long been thought they are more similar to
mammals than birds in their reliance on tactile and smell senses for
foraging. The kiwi genome showed significantly higher diversity in smell
receptors than other investigated birds, suggesting that they may be able
to distinguish a larger range of odors.
Nocturnal animals tend to have low energy metabolism, and kiwi have the
lowest metabolic rate among all birds. In the genome, the team found
enriched changes in genes related to energy expenditure, reserves and
metabolic processes, which may also be linked to this nocturnal lifestyle.
Diana Le Duc added: “Despite conservation efforts, North Island brown
kiwi are still at high risk of extinction. We made a first estimate of the
diversity of the kiwi genome by comparing the sequence of two
individuals, and it appears to be as low as that of inbred birds. This is an
important indication of the level of the threat, and we expect further
insights from the genome to help in developing conservation management
strategies.”
-ENDSMedia Contact
Joel Winston
Media Officer
BioMed Central
T: +44 (0)20 3192 2081
M: +44 (0)7766540147
E: Joel.Winston@biomedcentral.com
Notes to editor:
1.
Research article
Kiwi genome provides insights into evolution of a nocturnal lifestyle
Diana Le Duc, Gabriel Renaud, Arunkumar Krishnan, Markus Sällman Almén, Leon
Huynen, Sonja J. Prohaska, Matthias Ongyerth, Bárbara D. Bitarello, Helgi B. Schiöth,
Michael Hofreiter, Peter F. Stadler, Kay Prüfer, David Lambert, Janet Kelso, Torsten
Schöneberg
Genome Biology 2015
doi 10.1186/s13059-015-0711-4
During embargo, article available here: http://bit.ly/1eaMYKS
After embargo, article available at journal website here:
http://dx.doi.org/10.1186/s13059-015-0711-4
Please name the journal in any story you write. If you are writing for the web, please
link to the article. All articles are available free of charge, according to BioMed Central's
open access policy.
2.
Genome Biology serves the biological research community as an international
forum for the dissemination, discussion and critical review of information about all areas
of biology informed by genomic research. Key objectives are to provide a guide to the
rapidly developing resources and technology in genomics and its impact on biological
research, to publish large datasets and extensive results that are not readily
accommodated in traditional journals, and to help establish new standards and
nomenclature for post-genomic biology.
3.
BioMed Central is an STM (Science, Technology and Medicine) publisher which has
pioneered the open access publishing model. All peer-reviewed research articles
published by BioMed Central are made immediately and freely accessible online, and are
licensed to allow redistribution and reuse. BioMed Central is part of Springer
Science+Business Media, a leading global publisher in the STM sector.
www.biomedcentral.com