Study sheds new light on how some fish adapt to saltwater

October 8, 2013, UC Davis

( —Tilapia fish readily adapt to fresh or salty water, making them both good candidates for aquaculture and potential invasive pests. New work at the University of California, Davis, shows how tilapia can change the protein makeup of their gills, allowing them to nimbly adjust to widely varying levels of water salinity.

Salinization and salinity stress are of particular concern for and other organisms, as is predicted to cause rises in and more frequent droughts. Results from the study are reported in the Sept. 24 issue of the journal Molecular & Cellular Proteomics.

"This study provides us with a better understanding of the strategies that different fish species have for coping with salinity stress, as well as the limitations of those strategies," said Dietmar Kueltz, a professor of animal science. "That in turn will provide insight into future impacts of climate change on the composition of species in habitats affected by salinization."

He added that such studies also reveal which protein-coding genes will be under the strongest selection pressure in future scenarios.

For this study, the researchers worked with Mozambique tilapia (Oreochromis mossambicus), one of four tilapia species that readily interbreed, producing hybrids that are used worldwide in aquaculture operations. These hybrids grow rapidly and are easy to raise. They also have a high tolerance for many environmental stresses, including salinity stress.

Their adaptability to different environments has, however, also given them the capacity to invade and thrive in non-native habitats. Although tilapias are originally native to African freshwater ecosystems, they have spread throughout the world, including to marine reef ecosystems in Hawaii and Florida.

"Understanding the molecular, or proteomic, basis of tilapia's high environmental stress tolerance will also offer insight into potential strategies for managing these fish in aquaculture operations and controlling their invasiveness," Kueltz said.

In this study, the researchers focused on the molecular changes that occurred in the lining, or epithelium, of the tilapias' . The adaptability of the gill epithelium plays an important role in enabling tilapia and other related fish to live in a wide range of water salinity.

The fish are able to alter the proteins in the gill epithelium to adjust the amount of salt that can enter the body. The researchers analyzed the entire collection of proteins, or proteome, present in the gill tissue as the tilapia adjusted from a freshwater habitat to sudden or gradual exposure to water with varying levels of salinity, ranging from 34 parts per thousand (regular ocean salinity) to 70 ppt to 90 ppt.

Their data revealed strong effects of environmental salinity on the molecular characteristics of the tilapias' gills, including large changes in proteins that protect organisms and their cells from stress-related damage.

"The study also revealed specific proteins and mechanisms that are key to the tilapias' ability to tolerate an extremely wide range of salinity," Kueltz said. "Furthermore, it confirmed the reliability of this analytical process in studying stress-related changes in the molecular makeup of fish tissues," he said.

Kueltz and his team plan to conduct additional related research on the functions of proteins altered by in gills as well as other tissues such as those in the kidney and brain, which serve to alleviate the effects of environmental stress on fish.

Explore further: River salinisation an urgent ecological issue

Related Stories

River salinisation an urgent ecological issue

January 31, 2013

(—A just published review by Australian and European researchers has highlighted the growing global environmental problem of increasing salt levels in the world's rivers. Co-author, Dr Ben Kefford from the University ...

Tilapia feed on Fiji's native fish

January 12, 2010

The poster child for sustainable fish farming -- the tilapia -- is actually a problematic invasive species for the native fish of the islands of Fiji, according to a new study by the Wildlife Conservation Society and other ...

Salt water alone unlikely to halt Burmese python invasion

January 4, 2012

Invasive Burmese python hatchlings from the Florida Everglades can withstand exposure to salt water long enough to potentially expand their range through ocean and estuarine environments, according to research in the latest ...

Recommended for you

Space-inspired speed breeding for crop improvement

November 16, 2018

Technology first used by NASA to grow plants extra-terrestrially is fast tracking improvements in a range of crops. Scientists at John Innes Centre and the University of Queensland have improved the technique, known as speed ...

Cells decide when to divide based on their internal clocks

November 16, 2018

Cells replicate by dividing, but scientists still don't know exactly how they decide when to split. Deciding the right time and the right size to divide is critical for cells – if something goes wrong it can have a big ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.