Crabs are also complex learners

A crab can learn to walk in a maze and still remember it after two weeks The findings suggest that crustaceans, including crabs, lobsters and shrimp, have cognitive abilities for complex learning, although their brains are much smaller than those of other animals, such as bees The results were published in Biology Letters "In terms of the number of neurons, the brain of a crustacean is only about one tenth that of a bee." According to Edward Pope of Swansea University in the UK Pope and his colleagues trained 12 green crabs to walk the underwater maze in the aquarium There is only one correct path to the end of the maze The path requires five changes of direction, and there are three dead ends in the maze Researchers placed a mussel at the end of the maze as a delicious reward The crabs tried to walk the maze once a week for four weeks It wasn't until the third week of training that they went through the maze without making mistakes However, after every training, their performance has improved Pope and his team waited another two weeks to test the crab's memory This time, the researchers put crabs in a maze and didn't offer food rewards All 12 crabs completed the maze in 8 minutes In contrast, a group of untrained crabs took an average of 39 minutes to complete the maze, while only seven of the 12 reached the finish line within an hour "It's interesting that crabs can learn to walk the maze." Neil Burgess of University College London says that although they seem to learn more slowly than rodents or other mammals Pope said that his team next wants to study how changes in the marine environment, such as ocean acidification and temperature rise, affect the learning ability of crabs