British researchers have found that a British crab can learn to find the right way to travel in a maze and remember it until two weeks later, New Scientist reported on October 23. The findings suggest that crabs may be smarter than we think, and crustaceans, including crabs, lobsters and prawns, have complex cognitive abilities, even though their brains are much smaller than those of bees.
Study leader Edward Pope, of Swansea University, said: “The brains of crustaceans are about one-tenth the size of bees when measured by the number of neurons. “
In the latest study, Popp and colleagues trained 12 crabs to walk underwater mazes in aquariums, with only one correct path to the finish line, but five changes of direction, and three dead ends, with researchers putting crushed mussels at the end of the maze as a reward.
Trained crabs try to walk through the maze once a week for four weeks. Although they didn’t manage to get out of the maze until the third week of training without making a mistake, they improved after each training session. The Pop team then waited another two weeks to test the crab’s memory.
This time, the team placed the crabs in a maze without food rewards. It turned out that all 12 crabs managed to get out of the maze in eight minutes, compared with an average of 39 minutes for a group of untrained crabs to get out of the maze.
Neil Burgess, of University College London, who was not involved in the study, said: “It’s interesting that crabs learn to walk the maze, even though they seem to learn more slowly than rodents or other mammals. “
Popp said his team next wants to study changes in ocean conditions– such as how acidification and warming affect crabs’ ability to learn.