Invasive crabs get nutrients through their gills

In the decades since the invasive green shore crab (Carcinus maenas) appeared off Canada’s west coast, its adaptability has led to its success in inhabiting environments at the expense of native species. It can withstand wide ranges in salinity and temperature. It can even cannibalize when necessary, said Tamzin Blewett, a postdoctoral fellow at the University of Alberta.

Blewett also discovered one more quality that may make these North Sea invaders successful alongside their native Canadian competitors. They can get nutrients through their gills.

“Their ability to feed doesn’t solely depend on just using their gut,” said Blewett, lead author on a study published in Royal Society Proceedings B that revealed these findings. “This ability is something they can use during periods of starvation.”

Blewett knew that both vertebrates and invertebrates could take up nutrients via their skin. But there was a widely held notion that arthropods couldn’t do this because of their hard exoskeleton. “But they have these beautiful, specialized gills that do more than just transport oxygen,” she said. They can also excrete waste and take up trace metals.

Blewett tested whether the green shore crabs could absorb the amino acid leucine through their gills at the Bamfield Marine Sciences Centre on Vancouver Island. They conducted a “gill perfusion” technique that that allowed her to show that these nutrients were absorbed across the gills.

Blewett thinks the crabs may also use these gills during fluctuations in salinity in estuaries. “This ability to absorb nutrients may help these crabs to withstand changes in salinity that can be a challenge for other organisms, and which may therefore contribute to their extreme adaptability,” she said.

But Blewett said she plans to study if this is something that can happen in other crab species as well.

“They’re an invasive species,” she said. “It was important in understanding why they are successful.”

Blewett plans to look at whether the green shore crabs will continue to absorb nutrients through their gills if they are being fed. She also plans to study the molecular structures that may achieve gill adsorption.