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Octopuses May Be Adapting to The Rising Acidity of Our Oceans, Study Suggests

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We know that all the excess CO2 we’re pumping into the air – alongside a host of other damaging effects – is driving up the acidity of the oceans as it sinks and dissolves into the water, but it seems as though the hardy octopus can find ways to adapt to its rapidly changing environment.


Previous research into the impact of ocean acidification on cephalopods such as octopuses, cuttlefish, and squid has shown some indication increased carbon dioxide in the water could negatively impact this type of marine life.

However, in a new study, a group of Octopus rubescens – a species of octopus common to the west coast of North America – were observed adjusting their routine metabolic rate (RMR) over a series of weeks in response to lowering pH levels in the surrounding water.

“Challenges to an organism’s physiology are often reflected in changes in energy use and therefore can be observed as changes in aerobic metabolic rate,” write the researchers in their paper.

A total of 10 octopuses were studied under controlled lab conditions, with RMR measured immediately after exposure to acidic water, after one week, and after five weeks. Critical oxygen pressure – a measure of whether not not animals are getting enough oxygen – was monitored at the same time.

To begin with, high levels of metabolic change were detected in the creatures – a sort of shock reaction that actually conflicts with earlier research into cephalopods, which had recorded a reduction in metabolic change in similar scenarios.


However, RMR had returned to normal after one week, and remained the same five weeks later, suggesting some adaptation had occurred. The increased acidity did have an impact on the ability of the octopuses to function at low oxygen levels, however.

“This response in RMR suggests that O. rubescens is able to acclimate to elevated CO2 over time,” write the researchers. “The observed increase in RMR may be the result of multiple acute responses to hypercapnia [increased CO2 in the blood], possibly including both behavioural and physiological strategies.”

Those strategies could include preparing to move to find a new stretch of water to inhabit, for example, the researchers suggest (something that wasn’t possible here). The short RMR boost might also reflect the octopuses making quick adjustments to their biological processes to suit the new acid level.

The study is the first to look at both short-term (one week) and longer-term (five week) changes in metabolism rates in cephalopods in response to ocean acidification. We know these creatures are tough, and it seems they even have coping strategies that might allow them to adapt to humans destroying the natural environment all around them.

None of this means that we should be okay with the current climate crisis though, or not be trying to make major changes to reverse it. When we don’t take proper care of the planet, it’s not just ourselves that we’re potentially dooming to extinction.

Also, these tests were done in controlled laboratory conditions that don’t take into account many other interlinking factors in the animals’ natural environment. For instance, even if the octopus themselves are able to adjust, what about their food supply?

“While this species may be able to acclimate to near-term ocean acidification, compounding environmental effects of acidification and hypoxia may present a physiological challenge for this species,” write the researchers.

The research has been published in Physiological and Biochemical Zoology.


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Cuttlefish Can Refrain From Eating if They Know a Better Meal Is on The Way

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Cephalopods such as octopuses and squids may demonstrate some impressive smarts, but the latest research on cuttlefish may just blow your mind.

Researchers have found that cuttlefish fed to a schedule will very quickly cut back on eating less enticing food, so they can gorge themselves on their favourite later on.


This means that not only are cuttlefish seemingly able to memorise the feeding schedule, they’re incorporating that schedule into future planning, and then exercising self-control to make the most of their favourite food (shrimp, yum).

That’s wild.

“It was surprising to see how quickly the cuttlefish adapted their eating behaviour – in only a few days they learned whether there was likely to be shrimp in the evening or not,” said neuroscientist Pauline Billard of the University of Cambridge in the UK and Université de Caen Normandie in France.

“This is a very complex behaviour and is only possible because they have a sophisticated brain.”

The experiment was conducted on 29 European common cuttlefish (Sepia officinalis). These little guys were put in tanks, and tested to see what their favourite food was.

They were given crab and shrimp at the same time, five times a day for five days; whichever food item they went for first was interpreted as the favourite. All 29 cuttlefish were all about that shrimp.

For the experiment, the cuttlefish were fed daily. All cuttlefish got a crab in the morning. One group was then also given a shrimp every evening. The other group was randomly given a shrimp or not, which was decided using a random number generator.


The first group quickly adapted. They seemed to know that a shrimp (best food) was coming every night; they ate less and less of the crab over the 16-trial experimental period, and went nuts on the shrimp.

As for the second group, the random provision of shrimp could not be counted on; these cuttlefish ate more or less the same amount of crab for the duration of the experimental period. Overall, there was a significant difference in crab consumption between the two groups.

Then, the groups were swapped. And the same thing happened: The cuttlefish that were reliably fed shrimp adapted and ate less crab; the cuttlefish that received shrimp randomly ate significantly more crab.

It’s not dissimilar to experiments on vertebrate animals (and small children), where they are tested on self-control. It’s called the marshmallow test, and subjects are thought to have successfully demonstrated self control if they refrain from eating a treat when they know there will be a better one later.

Crows and ravens – those wickedly intelligent eldritch birds – have shown this ability, as have some primates, and dogs, albeit variably.


But cephalopods are different. They’re not just invertebrates; their evolutionary path on this planet is different from pretty much every other organism. So, too, is their intelligence – leading to the (uh, out-there) hypothesis that octopuses are, actually, from another planet.

So seeing cognitive capacities that have been demonstrated in vertebrates also demonstrated by these little tentacle-faced squishy weirdos is pretty danged cool. And not just for its own sake. We can learn more about the evolution of complex cognition.

There’s just a little bit more work to do first. It’s not quite completely validated that the cuttlefish’s self-control-like behaviour is underpinned by an ability to plan for the future, or the desire to eat shrimp in the present moment. That will need to be investigated in future studies.

“Nevertheless, these results represent a promising way for further studies on flexibility and future-oriented behaviour in cephalopods,” the researchers wrote in their paper.

“Given that cephalopods diverged from the vertebrate lineage approximately 550 million years ago, finding comparable future-oriented abilities in cuttlefish might provide valuable evolutionary insight into the origins of such a complex cognitive ability.”

After this study, all the cuttlefish were kept in their respective labs. They participated in a few more non-invasive studies, and lived out their natural lifespans in comfortable cuttlefish habitats.

The research has been published in Biology Letters.


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Squid Brains Are Nearly as Complex as Dog Brains, Researchers Claim

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We all know that cephalopods are wicked smart, and their complex nerve systems go some way to explain their aptitudes. Now, a first-of-its-kind magnetic resonance imaging study of squid brains confirms just how rich the connections in their brains truly are.


Using high-resolution MRI and a suite of staining techniques, researchers have discovered and described previously unknown major neural pathways in squid.

“The modern cephalopods, a group including octopus, cuttlefish and squid, have famously complex brains, approaching that of a dog and surpassing mice and rats, at least in neuronal number,” said neurobiologist Wen-Sung Chung of the University of Queensland’s Queensland Brain Institute (QBI) in Australia.

“For example, some cephalopods have more than 500 million neurons, compared to 200 million for a rat and 20,000 for a normal mollusc.”

We all know that neural complexity doesn’t necessarily correlate with intelligence as we know it; but we also know that dogs have rather dense cerebral cortices, so it’s amazing to see how closely some cephalopods trail behind them in terms of brain connections.

To obtain the first high-resolution map of the brain – known as a connectome – of a bigfin reef squid (Sepioteuthis lessoniana) the team used two types of MRI, contrast-enhanced magnetic resonance imagery, and high angular resolution diffusion magnetic resonance imagery.

squid mri(Chung et al., iScience, 2020)

Preserved squid samples were stained with silver dye or multicoloured fluorescent neural tracers, which allowed the researchers to map the neural pathways. These techniques allowed them to confirm over 99 percent of the 282 major pathways that had already been identified.

They also identified 145 new, previously unknown major neural pathways. Of these, more than 60 percent are linked to the vision and motor systems – which could helps us to understand the mad camouflage skills of squid.


“We can see that a lot of neural circuits are dedicated to camouflage and visual communication,” said Chung.

“[This gives] the squid a unique ability to evade predators, hunt and conspecific-communicate with dynamic colour changes.”

How cephalopods see is a fascinating mystery. Technically, they are colourblind, as Chung and his colleague neurobiologist Justin Marshall, also of QBI, previously demonstrated “beyond doubt”.

But they do seem to be able to perceive colour in some way. Just look at how octopuses change colour to perfectly match their surroundings. Or how squids communicate by flashing colours at each other.

This research seems to have found some of the pathways associated with that visual processing and the behaviours it enables, as well as the possible structure in the brain responsible for coordinating vision and camouflage.

“The similarity with the better-studied vertebrate nervous system allows us to make new predictions about the cephalopod nervous system at the behavioural level,” Chung said.

“For example, this study proposes several new networks of neurons in charge of visually-guided behaviours such as locomotion and countershading camouflage – when squid display different colours on the top and bottom of their bodies to blend into the background whether they are being viewed from above or below.”

This research forms part of a long-term project to understand how cephalopod brains and intelligence work, since they are so very different from our own, and the brains of other vertebrates.

As the researchers wrote in their paper, “the apparently complex cognitive tasks cephalopods perform need this kind of solid background evidence before anthropomorphic speculations lead to misconceptions around these unique and wonderful creatures.”

The research has been published in iScience.


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Octopus And Squid Evolution Is Officially Weirder Than We Could Have Ever Imagined

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Just when we thought octopuses couldn’t be any weirder, it turns out that they and their cephalopod brethren evolve differently from nearly every other organism on the planet.

In a surprising twist, in April 2017 scientists discovered that octopuses, along with some squid and cuttlefish species, routinely edit their RNA (ribonucleic acid) sequences to adapt to their environment.


This is weird because that’s really not how adaptations usually happen in multicellular animals. When an organism changes in some fundamental way, it typically starts with a genetic mutation – a change to the DNA.

Those genetic changes are then translated into action by DNA’s molecular sidekick, RNA. You can think of DNA instructions as a recipe, while RNA is the chef that orchestrates the cooking in the kitchen of each cell, producing necessary proteins that keep the whole organism going.

But RNA doesn’t just blindly execute instructions – occasionally it improvises with some of the ingredients, changing which proteins are produced in the cell in a rare process called RNA editing.

When such an edit happens, it can change how the proteins work, allowing the organism to fine-tune its genetic information without actually undergoing any genetic mutations. But most organisms don’t really bother with this method, as it’s messy and causes problems more often that solving them.

“The consensus among folks who study such things is Mother Nature gave RNA editing a try, found it wanting, and largely abandoned it,” Anna Vlasits reported for Wired.


But it looks like cephalopods didn’t get the memo.

In 2015, researchers discovered that the common squid has edited more than 60 percent of RNA in its nervous system. Those edits essentially changed its brain physiology, presumably to adapt to various temperature conditions in the ocean.

The team returned in 2017 with an even more startling finding – at least two species of octopus and one cuttlefish do the same thing on a regular basis. To draw evolutionary comparisons, they also looked at a nautilus and a gastropod slug, and found their RNA-editing prowess to be lacking.

“This shows that high levels of RNA editing is not generally a molluscan thing; it’s an invention of the coleoid cephalopods,” said co-lead researcher, Joshua Rosenthal of the US Marine Biological Laboratory.

The researchers analysed hundreds of thousands of RNA recording sites in these animals, who belong to the coleoid subclass of cephalopods. They found that clever RNA editing was especially common in the coleoid nervous system.

“I wonder if it has to do with their extremely developed brains,” geneticist Kazuko Nishikura from the US Wistar Institute, who wasn’t involved in the study, told Ed Yong at The Atlantic


It’s true that coleoid cephalopods are exceptionally intelligent. There are countless riveting octopus escape artist stories out there, not to mention evidence of tool use, and that one eight-armed guy at a New Zealand aquarium who learned to photograph people. (Yes, really.)

So it’s certainly a compelling hypothesis that octopus smarts might come from their unconventionally high reliance on RNA edits to keep the brain going.

“There is something fundamentally different going on in these cephalopods,” said Rosenthal.

But it’s not just that these animals are adept at fixing up their RNA as needed – the team found that this ability came with a distinct evolutionary tradeoff, which sets them apart from the rest of the animal world.

In terms of run-of-the-mill genomic evolution (the one that uses genetic mutations, as mentioned above), coleoids have been evolving really, really slowly. The researchers claimed that this has been a necessary sacrifice – if you find a mechanism that helps you survive, just keep using it.

“The conclusion here is that in order to maintain this flexibility to edit RNA, the coleoids have had to give up the ability to evolve in the surrounding regions – a lot,” said Rosenthal.

As the next step, the team will be developing genetic models of cephalopods so they can trace how and when this RNA editing kicks in. 

“It could be something as simple as temperature changes or as complicated as experience, a form of memory,” said Rosenthal.

The findings have been published in Cell.

A version of this story was originally published in April 2017.


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