Manta rays have the largest brain to body weight ratio of any living fish.
Gentle giants of the open ocean: Manta Rays are fascinating creatures of incredible proportions. Adult oceanic manta rays reach a wing span of up to 7 metres and weigh up to two tonnes.
With disproportionately large brains when compared to their body size, the weight of a manta’s brain is more comparable to that of a similar sized mammal and is the largest brain of all fish by absolute weight.
Not only do Manta Rays have big brains, but the regions of the brain that account for this enlargement are linked to increased sensory functions which also compares to brain development in mammals.
The Manta’s brain possesses a network of blood vessels that surrounds their braincase which is used to help keep this organ warmer than the surrounding tissue. This system of blood vessels is able to be regulated in order to keep the manta’s brain functioning effectively when diving into the deep sea where temperatures decrease rapidly.
When compared to sharks, the heavy structure of the Manta’s brain compares the most to that of Hammerhead Sharks, most likely due to the 3-dimensional habitat they live in, their active and manoeuvrable lifestyles, highly developed social and migratory behaviour, and possibly the increased ability of sensory processing thanks to the broad shape of their heads.
Very little is known about the behavioural and learning capacities of these large-brained species since they are very difficult to study in their natural environment.