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The Chasmagnathus granulatus crab leads a simple life. It spends its days burrowing for food and trying to avoid its nemesis, the seagull. But recent research has shown that despite its rudimentary brain, this crab has a highly sophisticated memory. For example, it can remember the location of a seagull attack and learn to avoid that area. In mammals, this kind of behavior requires multiple brain regions, but a study published in the June issue of the Journal of Neuroscience suggests that the C. granulatus crab can manage with just a few neurons.
Neuroscientists at the University of Buenos Aires used cardboard cutouts of seagulls to test crabs’ memory skills. They found that the crabs could recognize the cardboard seagulls and figure out that they were nonthreatening—even when they appeared in different locations—implying an ability to apply learned knowledge. Moreover, the crabs retained this information: they still recognized the cutout 24 hours after the training session, the clinical benchmark for long-term memory in most animals, including humans.
The researchers tied the crabs’ behavior to lobula giant neurons, a type of brain cell found in crustaceans. Electrical recordings showed that these cells become less active as the crabs get used to the cardboard seagulls. The researchers suspect that these neurons store information about stimuli, such as seagulls, and that another type of cell handles contextual details, such as the environment. “These animals don’t have millions of neurons like mammals do, but they can still perform really complex tasks,” says Julieta Sztarker, one of the study authors. If researchers can figure out how memory works in the most basic animals, Sztarker explains, they may have a better chance at understanding the much more complicated human system.