The old cuttlefish still have good memories

Cuttlefish, with their airship-shaped bodies and eight wavy arms, don’t age like people. Sexual maturity tends to come late for them – around three-quarters of their two-year life, the rough equivalent of a human reaching puberty in their sixties. Geriatric cephalopods will then spend several weeks on an absolute hanger, mating with as many partners as possible. It is only after the end of these frenzied sexual deals that the real decrepitude comes to claim them: their feeding tentacles relax; their appetite deserts them; their color-changing skin sparkles like a turned-on television. The animals revolve almost instantly from their sexual peak into the throes of infirmity, and within days they are dead. “They’re coming out really beautiful,” Alex Schnell, a cuttlefish biologist at Cambridge University and the Marine Biological Laboratory in Massachusetts, told me.

Before this quick ending, however, the animals remained relatively healthy in body – and also in mind. Schnell and his colleagues to have found this common cuttlefish (Sepia officinalis) can still form and retain crystalline memories of personal experiences just a month before their death. They can catalog the what, when, and or recent events and use that knowledge to inform their actions in the present. It’s an animal approximation of what’s called episodic memory in humans, an ability that’s often touted as a kind of mental time travel that allows creatures to relive past experiences. For us, episodic memory usually begins to fade towards retirement age. But the cuttlefish version seems to persist deep into their golden months. “I don’t know of any other animal model that has shown episodic-type memory that is still intact,” Gabriel Nah, a neurobiologist who studies rat memory at Indiana University, told me and was not involved. to the work of Schnell.

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This cuttlefish can form episodic type memories to all the age is remarkable. In humans, episodic memories are the source of subjective knowledge that cannot be found in textbooks or Google searches; they live in the world of personal storytelling, each unique to the individual who makes them. Until the late 1990s, researchers had no evidence that non-human animals could handle even the basics of this type of booster.

Everything changed when Nicky Clayton and Anthony Dickinson, researchers at the University of Cambridge, show that the western scrub jays could remember when and where they had hidden particular caches of food, and knew how to avoid collecting food that had been hidden long enough to rot. What the birds accomplished wasn’t necessarily an exact echo of the emotional, awkward memory that humans engage in when, say, longing for a first date. But all the mental ingredients, at least, seemed to be there.

Over the next two decades, the What-When-Where Memories Club grown up include more birds, rodents, dogs, and others. Common cuttlefish, already famous for their sophisticated big brains, have become card-carrying members in 2013, when a team led by Clayton and Christelle Jozet-Alves showed that cephalopods could keep track of what they ate, when, and where they ate after researchers offered them snacks in order, like a mental eating journal. Schnell took over the project a few years ago and became curious whether their abilities could withstand the ravages of time. In humans, episodic memory “is one of the first types of memory that begins to deteriorate as an individual ages,” she told me. But in a series of delicate trials designed by Schnell and colleagues, middle-aged cuttlefish, around 10-12 months old, and older postpubertal cuttlefish, 22-24 months old and a few weeks before death , have kept their minds about them. .

Researchers first had cephalopods prove that they could memorize a feeding routine, tapping into another form of memory, called semantic memory, which deals with general facts and concepts and remains intact in the elderly. Cuttlefish have successfully learned to swim to specific places in their aquarium marked with identical black and white symbols to earn edible rewards at different times of the day – the equivalent of eating in a breakfast nook in the morning, a kitchen counter at noon, and a formal dining room at night.

Then came the hardest test. The researchers trained six new animals in each age group to associate the same black-and-white symbol with two types of food: live shrimp, luxury cuttlefish food, or a boring piece of shrimp meat. In the morning, the cuttlefish were given a selection of both seafood at a time, each in its own location in the tank. They would then receive a second feed, either an hour later with only the least desirable menu item, or three hours later with both options available.

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In the case of an hour, the cuttlefish had to swim to where the breakfast shrimp was offered to earn the second meal. If three hours had passed, they could spend some time at the shrimp spot for a tastier reward. (The cuttlefish, apparently, can tell what time it is, and no one knows how yet.) In short, the cuttlefish had to match what they ate breakfast for or the larva had appeared for the first time, while also calculating how much time had passed since their last suckling. Each day of the experiment, the feeding points of the prawns and prawns moved. The cuttlefish therefore had to rely on their personal experiences of their morning meal and adapt accordingly.

Most older people, Schnell said, would have missed a human version of the team’s experiments. But all the cuttlefish were successful, “an incredibly complex thing for an animal to do,” Robyn Crook, a neurobiologist and cephalopod expert at San Francisco State University who did not participate in the study. If anything, said Schnell, the older ones were faster learning the rules and applying them in new contexts, which is “quite mind blowing”.

Wild cuttlefish do not hunt by sneaking up to black and white symbols in laboratory tanks. But Schnell and Clayton believe the skills the cephalopods showed in these experiments could translate into hunting, or even their orgies on the hill. Replaying personal memories in their heads could, for example, help animals know which reefs teem with crabs at dusk, or which males or females they have already fucked. And, of course, revisiting the memories is not just a matter of pass. The cuttlefish might be among the few animals that have enough cognitive ammo to use these memories to plan ahead. Previous research by Schnell and others has shown that cephalopods will switch to poor food if they know better options are ahead-a type of self control it takes years for human children to develop fully.

Adapting human concepts and experiences to other animals is always a tricky business, not least because the wants and needs of other species, and the intelligence they need to navigate them, are so different from ours. Some researchers remain skeptical that what-when-where memory, impressive as it is, even counts as episodic. Jennifer Vonk, an animal cognition expert at Oakland University, Mich., Who was not involved in the study, told me that the task assigned to the cuttlefish may “not have been completed. not been difficult enough ”to really push the boundaries to remind them. Under more natural circumstances, with more distractions, the weak points of the cephalopods could have appeared more clearly.

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Older cuttlefish, after all, are not totally immune to aging. While fairly fit for repeated sex, they still show slight signs of wear and tear: slower reflexes, dull interest in food, haggard skin. Schnell sees this happening even in virgin, lab-reared cuttlefish that reach their last days without a chance to mate. Trevor Wardill, who studies cuttlefish vision at the University of Minnesota and did not participate in Schnell’s study, told me that he noticed that older animals had difficulty hitting false prey in some hunting simulations. Articles from the 1990s suggest that aged cuttlefish could also have difficulties retain long-term memories.

In some ways, it’s hard to define what aging really is, in terms of cuttlefish. Humans are used to “a long period of maturity and a slow decline to senescence,” Jennifer Mather, a cuttlefish biologist at the University of Lethbridge, Canada, told me, who was not involved in the. study. Cephalopods take a more winding path to adulthood, accelerate their sexually active passage, and then “decline rapidly.” (Crook also pointed out that sex, which these cuttlefish didn’t have, might speed up the aging process.) Found very different results. Age and aging aren’t always the same: maybe the older cuttlefish in the study aren’t surprisingly sharp, just typical adults, acting exactly as old as they should be.