Lots you can learn from sea squirts

URI student studies how climate change will affect larval growth of marine invertebrates

Todd McLeish

Evelyn Siler collects sea squirts from the edge of a marina dock as part of her research. Photo by Amy Dunkle

Hopkinton resident Evelyn Siler has long been interested in studying genetics, in part to learn whether there is a genetic component to her brother’s autism. 

The University of Rhode Island senior has taken initial steps in that direction by studying the genetics of an invasive marine organism that can be used to understand the environmental effects on numerous other ocean creatures.

Siler, who is majoring in cell and molecular biology, is working with URI Professor Steven Irvine to understand how climate change may affect a common sea squirt, Ciona intestinalis, which she describes as “two-siphoned, gelatinous blobs that filter feed and spawn.” 

The animals are found on marina docks, shallow rocks, and other coastal habitats where you might also find mussels.

“They grow fairly quickly – it only takes 18 hours for them to develop from fertilized egg to larvae – so they’re useful to study in the lab,” Siler said. “You can follow their growth in a very short time.”

She and Irvine wonder whether the sea squirts will develop normally in water that is warmer, less salty and more acidic than they are used to – all conditions predicted to occur as a result of climate change. 

So she collected some sea squirts from Narragansett Bay and raised their larvae in water of varying salinity and pH levels and in temperatures of 18 or 22 degrees Centigrade, both warmer than the species’ preferred temperature of 14 C.

“As expected, we saw a definite decrease in normal larval growth at both temperatures, but the difference was most significant in the 22-degree water,” Siler said. “That’s where we saw the least normal development.”

What her results mean, she said, is that if climate change continues to warm the ocean, lower salinity and increase acidification, the sea squirts will have a much more difficult time producing normal larva.

“They won’t be able to cope with the stresses, and that will probably affect their population size,” she said. “And based on the fact that it’s a model organism that shares many genes with vertebrate species, we suspect the trend with those other species may be similar.”

The next step in her research will be to test whether the offspring of sea squirts that grow to adulthood in the altered water conditions – instead of taking specimens from the wild – will show the same results.

Siler’s research was funded through a Summer Undergraduate Research Fellowship provided by the Rhode Island Established Program to Stimulate Competitive Research, which provides training and career development for undergraduate students. 

The intensive summer research experience breeds a deeper involvement in the sciences and advances technical and cognitive skills. The program also helps students define a clearer picture of their career path.

Following graduation in December, the URI student plans to enroll in graduate school to pursue a doctorate in genetics and eventually pursue a career conducting genetics research.

“I’m not sure exactly where I see myself five years from now, probably working for a university or a private company,” Siler said. “I just know that I would definitely like to continue pursuing research-based fields. Having the opportunity to spend the summer conducting hands-on research has assured me that this is the field I belong in.”