Study offer new clues in sea star wasting epidemic

Northern rainbow star afflicted with sea star wasting disease. This species had virtually disappeared from central California kelp forests as of February 2014. Photo: Steve Lonhart / NOAA MBNMS
A northern rainbow star afflicted with sea star wasting disease. This species had virtually disappeared from central California kelp forests as of February 2014. Photo: Steve Lonhart/NOAA MBNMS.

Unique student research project tracks immune response to virus at genetic level

Staff Report

Biological sleuthing by a group of young marine-disease researchers from around the country may help solve the mystery of a massive sea star die-off along the West Coast.

Millions of the animals have died the past few years. Scientists still don’t why. They suspect a common ocean virus is at fault, and the new study, published this week in PLOS ONE, has contributed key information about the sea stars’ immune response when infected with this virus, which causes the marine creatures to develops white lesions on its limbs and within days dissolve or  into a gooey mass.

Last year, researchers identified a type of pathogen known as a densovirus as the likely cause, but they still can’t explain the mass die-off three years ago or why the common virus has affected so many starfish species from Alaska to Southern California.

Specifically, the student researchers looked at how genes expressed themselves in both healthy and sick sea stars while taking a summer class at the University of Washington’s Friday Harbor Laboratories. It’s the first time researchers have tracked how the genes behave when encountering this naturally occurring pathogen, which could help explain how sea stars attempt to fight the virus and why they develop lesions and appear to melt.

“Doing this study isn’t going to save the sea stars, but from an ecological perspective, it provides new information,” said Steven Roberts, a UW associate professor of aquatic and fishery sciences. “This could be a building block for future studies on the evolution of immune repertoires.”

The eight students who share lead authorship on the paper met for hours on video conference calls, talking through specific details of the paper. The students — from the University of Texas at Arlington, Pennsylvania State University, University of California, Santa Cruz and others — all contributed equally to writing and editing the manuscript, housed as a shared Google document, which is a rare approach in today’s academic publishing world.

“I work in smaller groups or with researchers from only one or two institutions for most of my projects,” said co-author Allison Tracy, a doctoral student at Cornell. “This was really interesting because we were able to collaborate across so many different backgrounds and institutions.”

The students started by looking at 30,000 genes from healthy and sick sea stars. They found that sick sea stars expressed genes differently than healthy ones, and they saw strong evidence of an immune response at the genetic level among infected sea stars. They also found that some of the genes involved in the nervous system and tissue-building were expressed differently in sick and healthy sea stars, which could help scientists better understand how the disease affects the sea stars’ bodies.

Researchers now suspect certain environmental conditions or perhaps water temperature contribute to the rate of disease or how effectively the sea stars can fight it off. As scientists around the country shift to monitoring sea star populations as well as studying the genetic code of the densovirus, they hopefully can use this initial characterization of how sea stars respond to disease, Roberts said.

“This gives us a bit of insight into what’s going on,” Roberts said. “One could argue that in the long term, this information could be used to build upon.”

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