Researchers may have discovered the secret behind an invasive ‘supervillain’ crab’s ability to thrive in extremely harsh environments.
Cannibalistic green shore crabs are native to the North Sea, but have rapidly spread across the ocean in recent decades.
Now, scientists have found that they are able to ‘eat’ by absorbing nutrients across their gills, likely helping them to survive even in areas of low oxygen and fluctuating salinity.
‘People just assumed that, because of their hard body, the crabs would not be able to access nutrients present in the water via the gills, and therefore they could only ingest nutrients through their digestive system,’ said lead author Tamzin Blewett, a post-doctoral fellow at the University of Alberta
‘We found that their gills, these specialized and delicate tissues that are designed for transporting things in and out of the body, are way more important than we originally thought.
‘While we knew that the crab gill takes up oxygen and deals with ions and toxicants in the environment, they are also being used for nutrition.
‘They’re super-critical organs.’
The researchers observed the crabs’ absorption of the amino acid leucine through nine sets of specialized gills.
These are hidden beneath their hard exoskeleton.
The team studied crabs at the Bamfield Marine Sciences Centre on Vancouver Island.
‘This type of crab is so readily adaptable to extremely harsh environments, and that’s why they’re everywhere,’ Blewett said.
‘They’re super-tolerant to low oxygen levels and changes in salinity, and now we know they also have this ability to consume nutrients through their gills.
‘This ability may come in handy between meals. This ability kind of makes them the superhero of the marine world – or supervillain, depending on your perspective.’
According to the researchers, these North Sea crabs made their way to Canada’s west coast in the last few decades.
In the time since, they’ve continued to be a problem, and are now on the Department of Fisheries and Oceans’ watch list.
The new understanding, while helping to reveal new insight on the function of the gills, has also dug up new questions.
‘Is this ability to absorb nutrients through the gills just for food, or is it a survival mechanism for when the crabs are situated in estuaries that are constantly changing in salinity?’ Blewett said.
‘Salinity can alter body water content, but amino acids can be used to offset these changes caused by salinity, so taking up amino acids from the water could be an adaptation to these environments.’