We people are fixated on huge brains as a proxy for smarts. However headless animals known as brittle stars haven’t any brains in any respect and nonetheless handle to study by way of expertise, new analysis reveals.
Family members of starfish, brittle stars spend most of their time hiding beneath rocks and crevices within the ocean or burrowing within the sand.
These shy marine creatures haven’t any mind to talk of — simply nerve cords operating down every of their 5 wiggly arms, which be part of to type a nerve ring close to their mouth.
“There is no processing middle,” mentioned lead writer Julia Notar, who did the analysis as a part of her biology Ph.D. in professor Sönke Johnsen’s lab at Duke College.
“Every of the nerve cords can act independently,” Notar mentioned. “It is like as an alternative of a boss, there is a committee.”
Within the case of brittle stars, that appears to be sufficient to study by affiliation, Notar, Johnsen and former Duke undergraduate Madeline Go report within the journal Behavioral Ecology and Sociobiology.
The sort of studying includes associating totally different stimuli through a course of known as classical conditioning. A well-known instance is Pavlov’s canine experiments, which confirmed that canines repeatedly fed on the ringing of a bell would ultimately begin drooling on the mere sound of a bell, even when no meals was round.
People do that on a regular basis. Should you hear the “ding” of a smartphone over and over with every new alert, ultimately the sound begins to have a particular that means. Simply listening to somebody’s telephone ping or buzz with the identical chime as yours is sufficient to make you reflexively attain in your personal telephone in anticipation of the subsequent textual content, e mail, or Instagram publish.
Classical conditioning has been demonstrated in a handful of earlier research in starfish. However most echinoderms — a gaggle of some 7,000 species that features brittle stars and equally brainless starfish, sea urchins and sea cucumbers — haven’t been examined.
To search out out if brittle stars are able to studying, the researchers put 16 black brittle stars (Ophiocoma echinata) in particular person water tanks and used a video digital camera to file their conduct.
Half the brittle stars had been skilled by dimming the lights for half-hour every time the animals had been fed. Each time the lights went out, the researchers would put a morsel of shrimp — “which they love” — within the tanks, positioned simply out of attain.
The opposite half obtained simply as a lot shrimp and likewise skilled a 30-minute darkish interval, however by no means on the identical time — the animals had been fed beneath lit situations.
Whether or not it was gentle or darkish, the animals spent most of their time hiding behind the filters of their tanks; solely popping out at mealtime. However solely the skilled brittle stars discovered to affiliate darkness with meals.
Early within the 10-month-long experiment, the animals stayed hidden when the lights went out. However over time, the animals made such a connection between the darkness and mealtime that they reacted as if meals was on its approach and crept out of hiding every time the lights went out, even earlier than any meals was put within the tanks.
These brittle stars had discovered a brand new affiliation: lights out meant that meals was more likely to present up. They did not have to odor or style the shrimp to react. Simply sensing the lights go dim was sufficient to make them come when known as for dinner.
They nonetheless remembered the lesson even after a 13-day ‘break’ with out coaching, i.e., dimming the lights over and over with out feeding them.
Notar mentioned the outcomes are “thrilling” as a result of “classical conditioning hasn’t actually been proven definitively on this group of animals earlier than.”
“Understanding that brittle stars can study means they don’t seem to be simply robotic scavengers like little Roombas cleansing up the ocean flooring,” Notar mentioned. “They’re probably in a position to count on and keep away from predators or anticipate meals as a result of they’re studying about their setting.”
As a subsequent step, Notar hopes to begin to tease aside how they handle to study and bear in mind utilizing a nervous system that’s so totally different from our personal.
“Individuals ask me on a regular basis, ‘how do they do it?'” Notar mentioned. “We do not know but. However I hope to have extra solutions in a couple of years.”
This work was supported by the U.S. Division of Division of Protection by way of the Nationwide Protection Science & Engineering Graduate Fellowship Program, the Duke Nicholas College Rachel Carson Students program and the Duke Biology Division.
