What Can Cephalopods Teach Us About Adapting to Climate Change?

When it comes to climate change research, a lot of the news is bad.

The planet is warming, seas are rising, and much of life on Earth is struggling to respond—but there are a few examples of organisms swimming against that current.

Most of the scientific literature is “flooded with doomsday situations of how everything is just dying,” said Aalok Varma, a Grass Fellow at the Marine Biological Laboratory (MBL) and a postdoctoral fellow at the University of California, San Diego. “That’s not really true.”

“Biology can cope with a changing environment,” he said. “Maybe not all organisms, but there are definitely some that do well, some that do badly.”

One group that seems to be flourishing is the cephalopods, a collection of marine organisms that include octopuses, cuttlefish, and squid. Data show these three—known as coleoid cephalopods—have actually seen an overall population increase in the last 60 years, Varma said. Exactly why their numbers are going up is unknown, he added, but their success means they could be a good model to study how organisms adjust to climate change. Varma plans to spend his summer in the Grass Lab simulating climate change effects and testing behavioral responses in the hummingbird bobtail squid (Euprymna berryi).

“If we can find a feature of this animal that allows it to adapt better to changing ocean environments, maybe we should look for that feature in other animals and try and identify not just animals, but maybe even fungi or other species, that could cope well with climate stress,” he said.

Simulating the problem

Worldwide, elevated carbon dioxide in the atmosphere is increasing ocean temperature and acidity. The global significance of these two effects makes them good starting points for experimental research, Varma said.

He plans to recreate these effects in the lab and observe impacts on the squids’ circadian rhythms (internal body clocks) and prey capture behavior, both of which are innate behavioral responses. “And I tend to look at innate behavioral responses because they might tell you more about the intrinsic biology of the organism, as opposed to behaviors which are learned, which are shaped by an animal's experience,” Varma said.

Circadian rhythms can be observed by setting up a video camera, recording a squid for several days, and watching for patterns of activity, while prey capture can be filmed at high speed under a microscope. Varma will present individual squid with shrimp and track their movements and how quickly they catch their prey.

The MBL’s Marine Resources Center has provided Varma with tank systems to house the squid; changing temperature or acidity is as easy as adjusting a thermostat or switching on carbon dioxide bubblers, respectively. Just like in the ocean, the carbon dioxide dissolves and joins with water molecules to become carbonic acid, which increases the water’s acidity as it breaks into hydrogen and bicarbonate ions.

Varma will observe the squids’ behavior in increased temperature and increased acidity conditions, as well as in a combination of both.

A climate counterbalance?

In high-temperature-only and high-acidity-only conditions, Varma expects to see more frequent bouts of activity, since animals naturally seek more suitable environments when under duress. He also expects these two conditions will increase squids’ metabolic demands for food, but simultaneously make them sluggish and unable to meet those demands in prey capture experiments.

But, Varma predicts increasing temperature and acidity at the same time will result in behaviors similar to normal conditions. It’s possible the effects of higher temperature and higher acidity could actually counterbalance one another, he said, and animals faced with both effects will do better than animals faced with only one or the other.

Coleoid cephalopods can adapt to stressful environments in part because they can edit their RNA, Varma said. RNA, like DNA, is a form of genetic instructions; by tweaking it, an organism can adjust which proteins it produces in its body and better suit itself to its environment. Coleoid cephalopods make about 100 times more edits to their RNA than most other animals, Varma said.

“The key enzyme for RNA editing, ADAR2, appears to be less active at high temperatures, but more active at lower pH's,” he explained. “So, I argue that the net balance of RNA edits needed by an animal [to adapt to environmental change] can be achieved when both temperature and pH are altered.”

That line of thinking is speculation for now, he cautioned, pending further research. No matter what he finds, Varma hopes people don’t draw the wrong conclusions from his research.

“I hope it does not suggest to the public that climate change is not a crisis,” he said. “It is very much a crisis, and just because the occasional animal is doing well doesn't mean that we should always relax.”

Despite the harsh realities of climate change, cephalopods provide a glimpse at what success can look like. Varma’s research could open the door for a better understanding of how organisms adapt to a changing world.