What has three hearts, eight squiggly arms, blue-green blood, and one of the largest brains among animals? A cuttlefish. New findings of old cuttlefish show these creatures can remember specific events even in old age. For example, what they ate and who they mate. This is in stark contrast to other animals and humans whose memory deteriorates over time.
Cuttlefish (Sepia Officinalis), as a cephalopod, roughly live for two years, making them interesting subjects to evaluate the impact of age on memory. Published this week in the journal Proceedings of the Royal Society B, the study is not only an exploration of cuttlefish traits but also offers evidence of an animal whose memory does not decline with age.
It’s not that the cuttlefish in themselves are impervious to aging. Muscle function and appetite deteriorate, and they do die eventually. But researchers found that they can form new memories even towards the end of their lifetime.
“Cuttlefish can remember what they ate, where and when, and use this to guide their feeding decisions in the future,” Alexandra Schnell of the University of Cambridge’s Department of Psychology, who conducted the experiments, said in a press release. They can form the what, where, when of recent events, using the knowledge to inform their actions.
To show this, the researchers conducted memory tests on two groups of cuttlefish: half were 10-12 months old and others were 22-24 months old (equivalent of a human in their 90s). The older cuttlefish were able to remember each detail, and sometimes, even outperformed the younger cuttlefish.
This tendency to remember makes cuttlefish among the first invertebrates to have a solid memory. Humans, on the other hand, are known to suffer cognitive and memory declines with age. This idea of “episodic memory” — the collection of personal experiences at particular times and places — declines in humans, impacting their ability to recall past events, sometime around 60 years of age.
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But episodic-like memory system in cuttlefish differs from episodic-like memory in other non-human species. This is because of varying biology. Memory in humans is linked to the hippocampus — a part of the brain located near our ears. Cuttlefish, on the other hand, do not have the hippocampus. Their “frontal lobe” retains memory and learning over time. It deteriorates over the last two to three days of the cuttlefish’s life.
Interestingly, the cuttlefish also remember their mating habits in acute detail. This is because cuttlefish breed only at the end of their life, the rough equivalent of humans hitting their puberty at the age of 60, Katherine Wu noted in The Atlantic. By remembering who they mate with, and even the location, they try to mate with as many fish as possible to ensure the cuttlefish spread their genes widely. “We think this ability might help cuttlefish in the wild to remember who they mated with, so they don’t go back to the same partner,” Schnell said.
The cuttlefish’s prime last for quite some time and only comes to a halt in the last few days of their life. Sexual activity is swapped for infirmity almost instantaneously. “They really go out with a bang,” Alex Schnell told The Atlantic.
To scientists, this discovery is another evidence of the fascinating and advanced cognitive abilities of animals, similar to our own. In the past, birds, rodents, dogs, and other animals have shown signs of carrying episodic memory — but in each, the decline was imminent as they aged.
“The pedestal upon which humans place themselves in terms of neurological abilities continues to crumble. It is just that other types of animals perform similar functions differently,” Malcolm Kennedy, professor of natural history at the University of Glasgow, who was not part of the study, told The Guardian.
