Stranded dolphins show signs of Alzheimer’s disease

(ORDO NEWS) — The mysterious behavior of cetaceans, which “commit suicide” by throwing themselves ashore, may be associated with a brain disease and the resulting disorientation in an elderly pack leader.

Alzheimer’s disease is associated with neurodegenerative processes in the brain. It usually develops in older people.

Abnormal accumulations of amyloid and tau proteins cause destruction of nerve cells and connections between them, leading to severe degradation of cognitive functions.

A few years ago, biologists showed that the same processes can occur in wild animals.

Amyloid plaques and neurofibrillary tangles, characteristic of Alzheimer’s disease, were then found in the brain of dolphins, moreover, living in the wild, in nature.

Since then, Frank Gunn-Moore and colleagues at several Scottish universities have continued to study the disease in dolphins.

During this time, they were able to collect and analyze brain tissue samples from 22 individuals, representatives of five different species of dolphins, which were found stranded on the coast in Scotland.

According to the authors of the article, four dolphins belonging to three different species were found to have all the pathological signs of Alzheimer’s disease, including amyloid plaques, accumulation of tau proteins and gliosis – the replacement of dead neurons with neuroglial cells, which normally should support and “serve” them.

All this indicates that neurodegeneration and dementia may be characteristic not only of humans, although the decline in cognitive functions in such dolphins, strictly speaking, has not yet been proven.

In addition, the work is consistent with a relatively new hypothesis related to the beaching phenomenon of cetaceans.

So far, the most popular explanation for this self-destructive behavior remains the noise pollution of the ocean by ships and sonar, which confuses and often injures the sensitive organs of echolocation of these animals.

However, another idea arose a few years ago, linking the ejection to a “sick leader”, which, due to disorientation, can lead the entire flock to dangerous shallow water.

Then the authors of this hypothesis investigated the case of a massive beaching of seven sperm whales at once and showed that it could be caused by a viral infection that struck the oldest member of the flock.

But new work by Gan-Moore and colleagues offers yet another explanation.

It is possible that such individuals, which, as a rule, act as leaders of their groups, develop senile neurodegeneration. It is the loss of orientation associated with it that leads the entire group to death.

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