Nautilus Rising: A Living Fossil’s Unexpected Renaissance

Underestimation is a rather unfortunate, but powerful, phenomenon. It is easy to become lost in its narrow, dimly lit pathways; much harder to find a way back out. The one hint of beauty that resides in this whole ordeal of underestimation is the potential for a moment, after a seemingly endless battle against a stubborn majority, of brilliant breakthrough. The fight is never finished at this point, but for a short time it is possible to revel in how the world has been stunned into a satisfying hush.

Enter the nautilus.

Nautilius pompilius, the chambered nautilus, is something of a funny creature. With a body almost completely encased by a shell, retractable tentacles emerging only to sense surroundings and food, and with most of its activitImagey occurring in the evening hours, when it ascends from the depths of the ocean to feed in shallower water, the nautilus lives its life quietly and cautiously. While life in the slow lane may not appeal to many, it seems to be working just fine for this secretive cephalopod: having lived for somewhere around 500 million years, it has certainly earned its status as a “living fossil.”

The title “living fossil”, however, doesn’t come without its share of stigma. Because of its relatively primitive brain structure, many people believed that the nautilus was not capable of the same complex learning and memory storage as its more modern relatives, the sleek and shell-less coleoids (squid, octopus, and cuttlefish). Private animal that it is, the nautilus was not about to stage a loud protest arguing for its intellectual capabilities; so for a while the belief stuck that Nautilius pompilius was, for the most part, an uncomplicated creature.

Luckily, the members of the Basil et al. lab (2011) noticed the current that seemed to be pushing everyone’s thoughts in the same direction and did what any good scientists should do: they wondered if the assumptions about the nautilus were wrong. After all, you don’t get to be a “living fossil” without learning a few things along the way. They watched closely, trying to see past the layers of prejudice that had shrouded the nautilus for so long, then used those observations to construct a series of graceful experiments that would allow the creature to reveal its cognitive capabilities. The nautilus did not disappoint.

To test the nautilus’s capacity for learning and memory, Basil et al. (2011) paired flashes of blue light with the release of a fish head odor, a favorite nautilus snack, to see if the animals would learn and remember the association between the light and the food. Nautiluses extend their tentacles when they sense the promise of a delicious meal, so the researchers used this response to measure whether the creatures were learning. The experiment had two conditions: in the first, the flashes of light were always immediately followed by the release of the fish head odor, creating a temporal link between the stimuli; in the second, the fish head odor was released at regular intervals, but the flashes of light were completely random. Both conditions involved a series of training trials, after which the blue light was shown on its own, without any odor. Only in the first condition, where the odor always followed the light, did the nautiluses extend their tentacles in response to the light alone – they had learned that the flashes of light predicted the potential for food, so their tentacles did a happy dining dance whenever they saw it.

Not only can nautiluses learn an association between light and food, but they can also retain that newly acquired information (Crook & Basil, 2008). Their short-term memory is excellent – even after an hour of only seeing the flashing light, the nautiluses kept extending their tentacles with vigor, ever hopeful for a meal. This excited response died down between hours one and six, which the researchers attributed to a period of memory consolidation, but shot back up again around the twelfth hour of seeing the flashing light, demonstrating a previously unheard of capacity for long-term memory. Despite having no specific brain regions dedicated to memory storage, the nautilus seemed to be just as capable of learning and remembering novel information as its coleoid counterparts.

Those same tentacles that wiggle with joy at the prospect of food also allow the nautilus to maintain a keen awareness of its physical surroundings. Tentacles help nautiluses to feel their way along coral reefs during their nocturnal journeys for meals, as they search for paths that include both hiding spots from predators and undiscovered food stores. Because this heightened sense of touch would be crucial for moving about in the darkeImagest parts of the ocean, Crook et al. (2009) predicted that the nautilus would be particularly astute at detecting changes in the structure of coral reefs.

Sure enough, the nautiluses showed an incredible ability to sense variations in their environment. After being allowed to explore a tank housing an artificial coral reef for a few hours, the nautiluses were removed from the tank and the cinder blocks that made up the synthetic reef were rearranged. When the nautiluses were brought back and allowed to explore the reef once more, they suddenly became extra vigilant, distancing themselves from the side of the reef and only swimming close to it after some time had gone by. This finding speaks not only to the nautilus’s learning and memory capacity, but also hints at a survival strategy of cautious investigation, as opposed to fearless exploration, that may have helped to keep to keep the species alive for all these years.

Against all odds, the nautilus has managed to move beyond the stigma of being a “simple” creature – and these findings are likely just the beginning of many more to come. Unfortunately for the nautilus, the majority of the research so far on the cognitive complexity of cephalopods has focused on coleoids, meaning nautilus research has a bit of catching up to do. But Basil et al. have taken a crucial first step in illuminating the creature’s hidden abilities, as well as providing multiple directions for future studies. They have shown that our tendency to underestimate will no longer do – it’s time to allow the nautilus to lead where it will, quietly astounding us along the way.

 

References:

Basil, J., Barord, G., Crook, R., Derman, R., Hui Ju, C., Travis, L. & Vargas, T. (2011). “A synthetic approach to the study of learning and memory in Chambered Nautilus L. (Cephalopoda, Nautiloidea).” Vie Et Milieu – Life and Environment, 61, 231-242.

Crook, R. & Basil, J. (2008). “A biphasic memory curve in the chambered nautilus, Nautilus pompilius L. (Cephalopoda: Nautiloidea).”Journal of Experimental Biology, 211, 1992-1998.

Crook, R., Hanlon, R. & Basil, J. (2009). Memory of visual and topographical features suggests spatial learning in nautilus (Nautilus pompilius L.).” Journal of Comparative Psychology, 123, 264-274.