Nav: Home

Freshwater find: Genetic advantage allows some marine fish to colonize freshwater habitats

May 30, 2019

How did some marine fish manage to make their way from the salty sea to the newly available freshwater niches after the last ice age and eventually differentiate from their marine brethren?

It comes down genetics -- and diet, according to a team of scientists at the Research Organization of Information and Systems (ROIS) in Japan. The study is published on May 30 in the journal Science.

"One of the underappreciated constraints for freshwater colonization by marine animals is the poor nutritional quality of food in freshwater ecosystems," said Jun Kitano, the study's author and professor in the Ecological Genetics Laboratory at the National Institute of Genetics, part of ROIS, "Generally, the food chain in marine environments is rich in the omega-3 fatty acid DHA, which is essential for animal development and health. However, freshwater ecosystems contain very little DHA."

Kitano, along with lead author Asano Ishikawa, and his team compared the genomes of freshwater stickleback to marine stickleback, a small fish with three spines on the back.

They found that freshwater Three-Spined Stickleback has multiple copies of a gene called Fads2, which helps synthesize DHA. With more copies of the gene, the fish can synthesize more DHA, compared to their marine cousins who have an abundance of DHA available in their diet.

To further test this theory, the researchers developed a genetic mutant of the marine stickleback that over-expresses Fads2. It synthesized more DHA and demonstrated a longer lifespan than control marine stickleback, providing further evidence that the genetic ability to make use of available DHA dictates where fish colonize.

"It's unclear when the genetic advantage appeared," Kitano said. "It may be that ancient extinct freshwater species possessed additional Fads2 copies somewhere in the genome or adapted to DHA-deprived diets through other mutations."

According to Kitano, it could also be that multiple copies of the gene allowed some versions to acquire new functions, such as a way to better synthesize DHA.

The Fads2 gene may allow certain selections in species beyond the stickleback, as it also appears at higher rates in fishes that colonized freshwater. A previous study also showed signatures of natural selection in humans that colonize polar regions.

"It certainly appears to be an important gene beyond fish, in a wide variety of organisms, including humans," Kitano said.
This work is supported by the Research Organization of Information and Systems, the Japan Society for the Promotion of Science, the Asahi Glass Foundation, the Sumitomo Foundation, and the Swiss National Science Foundation.

The other authors are Asano Ishikawa, Naoki Kabeya, Koki Ikeya, Ryo Kakioka, Jennifer N. Cech, Naoki Osada, Miguel C. Leal, Jun Inoue, Manabu Kume, Atsushi Toyoda, Ayumi Tezuka, Atsushi J. Nagano, Yo Y. Yamasaki, Yuto Suzuki, Tomoyuki Kokita, Hiroshi Takahashi, Kay Lucek, David Marques, Yusuke Takehana, Kiyoshi Naruse, Seiichi Mori, Oscar Monroig, Nemiah Ladd, Carsten J. Schubert, Blake Matthews, Catherine L. Peichel, Ole Seehausen, and Goro Yoshizaki.

About the Research Organization of Information and Systems (ROIS)

The Research Organization of Information and Systems (ROIS) is a parent organization of four national institutes (National Institute of Polar Research, National Institute of Informatics, the Institute of Statistical Mathematics and National Institute of Genetics) and the Joint Support-Center for Data Science Research. It is ROIS's mission to promote integrated, cutting-edge research that goes beyond the barriers of these institutions, in addition to facilitating their research activities, as members of inter-university research institutes.

Research Organization of Information and Systems

Related Genetics Articles:

Turning to genetics to treat little hearts
Researchers makes a breakthrough in understanding the mechanisms of a common congenital heart disease.
New drugs more likely to be approved if backed up by genetics
A new drug candidate is more likely to be approved for use if it targets a gene known to be linked to the disease; a finding that can help pharmaceutical companies to focus their drug development efforts.
Mapping millet genetics
New DNA sequences will aid in the development of improved millet varieties
Genetics to feed the world
A study, published in Nature Genetics, demonstrated the effectiveness of the technology known as genomic selection in a wheat improvement program.
Genetics researchers find new neurodevelopmental syndrome
Researchers have identified a gene mutation that causes developmental delay, intellectual disability, behavioral abnormalities and musculoskeletal problems in children.
The genetics of cancer
A research team has identified a new circular RNA (ribonucleic acid) that increases tumor activity in soft tissue and connective tissue tumors.
New results on fungal genetics
An international team of researchers has found unusual genetic features in fungi of the order Trichosporonales.
Mouse genetics influences the microbiome more than environment
Genetics has a greater impact on the microbiome than maternal birth environment, at least in mice, according to a study published this week in Applied and Environmental Microbiology.
New insights into genetics of fly longevity
Alexey Moskalev, Ph.D., Head of the Laboratory of Molecular Radiobiology and Gerontology Institute of Biology, and co-authors from the Institute of biology of Komi Science Center of RAS, Engelgard's Institute of molecular biology, involved in the study of the aging mechanisms and longevity of model animals announce the publication of a scientific article titled: 'The Neuronal Overexpression of Gclc in Drosophila melanogaster Induces Life Extension With Longevity-Associated Transcriptomic Changes in the Thorax' in Frontiers in Genetics - a leading open science platform.
Some personal beliefs and morals may stem from genetics
Penn State researchers found that while parents can help encourage their children to develop into responsible, conscientious adults, there is an underlying genetic factor that influences these traits, as well.
More Genetics News and Genetics Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at