Crabs can learn and remember their way through a complex maze

Authored by newscientist.com and submitted by mvea
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A species of crab can learn to navigate a maze and still remember it up to two weeks later. The discovery demonstrates that crustaceans, which include crabs, lobsters and shrimp, have the cognitive capacity for complex learning, even though they have much smaller brains than other animals, such as bees.

“Crustaceans have a brain roughly 10 times less than the size of a bee’s in terms of neuronal count,” says Edward Pope at Swansea University in the UK.

Pope and his colleagues trained twelve shore crabs (Carcinus maenas) to complete an underwater maze in an aquarium. The maze had a single correct path to the end, which required five changes of direction and included three dead ends. The researchers placed a single crushed mussel at the end of the maze as a tasty reward.

Read more: Bees are first insects shown to understand the concept of zero

The crabs attempted the maze once a week for four weeks. They did not manage to complete the maze without making a mistake until their third week of training, although they improved after each training session. Pope and his team then waited an additional two weeks before putting the crabs’ memories to the test.

This time, the team put the crabs in a maze without an edible reward. All twelve managed to complete the maze within 8 minutes. By contrast, a group of untrained crabs took an average of 39 minutes to complete the maze, with only 7 out of 12 crabs reaching the end in under an hour.

“It’s interesting that the crabs can learn the maze,” says Neil Burgess at University College London, UK, though they seem to learn more slowly than rodents or other mammals, he says.

Pope says his team next wants to investigate how changing ocean conditions, such as ocean acidification and rising temperatures, might impact the crabs’ ability to learn.

Journal reference: Biology Letters, DOI: 10.1098/rsbl.2019.0407

Frigorifico on October 23rd, 2019 at 09:37 UTC »

Bees can understand the concept of 0 and do simple math, ants recognize themselves in the mirror, it seems animals in general are smarter than what we always thought

Wu-TangJedi on October 23rd, 2019 at 03:57 UTC »

TIL crabs have smaller brains than bees, despite being considerably larger creatures for most varieties. Neat!

mvea on October 23rd, 2019 at 02:10 UTC »

The title of the post is a copy and paste from the first paragraph of the linked academic press release here:

A species of crab can learn to navigate a maze and still remember it up to two weeks later. The discovery demonstrates that crustaceans, which include crabs, lobsters and shrimp, have the cognitive capacity for complex learning, even though they have much smaller brains than other animals, such as bees.

Journal Reference:

Maze learning and memory in a decapod crustacean

Ross Davies , Mary H. Gagen , James C. Bull and Edward C. Pope

Biology Letters, Published:23 October 2019

Link: https://royalsocietypublishing.org/doi/10.1098/rsbl.2019.0407

DOI: 10.1098/rsbl.2019.0407

Abstract

Spatial learning is an ecologically important trait well studied in vertebrates and a few invertebrates yet poorly understood in crustaceans. We investigated the ability of European shore crabs, Carcinus maenas, to learn a complex maze over four consecutive weeks using food as a motivator. Crabs showed steady improvement during this conditioning period in both the time taken to find the food and in the number of wrong turns taken. Crabs also clearly remembered the maze as when returned two weeks later but without any food, they all returned to the end of the maze in under 8 min. Crabs that had not been conditioned to the maze (naive animals) took far longer to reach the end, and many (42%) did not venture to the end of the maze at all during the 1 h study period. This study provides an initial description of spatial learning in a benthic decapod; a better appreciation of this adaptive trait in these animals will develop our understanding of resource exploitation by benthic crustaceans and their ecological roles.