According to new research, a toxin produced by marine algae is causing seals brain damage, producing changes to a neurological and behavioral level that affects their ability to navigate in the sea and survive in the wild.
Scientists worked with sea lions that had been found stranded and rescued by the Marine Mammal Centre, testing their behavior and spatial memory for abnormalities and scanning their brains to look for signs of Domoic acid-related damage.
According to Peter Cook, cognitive psychologist from Emory University, the Domoic Acid is a toxin that transmits nerve impulses in the brain, and leads to over-activation of hippocampus nerve cells and chronic epilepsy.
The chemical was already known as a cause of sea lion’s deaths, but the new study was the first one to explain how it affects the behavior.
Among one of the tests made to analyze the spatial ability of the marine mammals, there was a maze similar to the ones used for rats but adapted for lions. However, scientists noticed that the poisoned sea lions showed a weakening performance on both short and long-term spatial memory tasks. Affected sea lions had trouble foraging for food, as they had “no sense which way to go”.
Other brain analysis using high-tech equipment that had never been used in mammals, found that, in addition to damage to the hippocampus, the injury also caused interactions between the hippocampus and other brain structures including the thalamus.
Cook stated that this is the first evidence they have of the changes in brain networks in exposed sea lions, adding that these animals may be suffering from a wide memory impairment and not just spatial memory deficit.
The researchers believe that the brain injuries develop over time with constant exposure to the toxin of the algae, which could explain why some sea lions and other marine mammals like whales strand on beaches throughout the year, even when there is no active bloom of the Domoic acid.
Source: Discovery News