Predatory Sea Slug Learns What Not to Eat By Trying to Eat Everything
Posted on June 20, 2013
Pleurobranchaea californica, a deep-water sea slug found off the west coast of the United States, has a simple dining plan. The slug tries to eat everything. If it tastes something that is toxic or not tasty it will avoid it the next time around.
Flabellina iodinea, commonly known as the Spanish shawl, also lives on the west coast. The Spanish shawl eats only one type of food, an animal called Eudendrium ramosum. The Spanish shawl consumes all of the Eudendrium except for its embryonic stinging cells. The Spanish shawl instead transports these stinging cells to its own cerata where they mature. In this manner, the Spanish shawl manages to co-opt its victim's body parts for its own defense.
Rhanor Gillette, University of Illinois professor of molecular and integrative physiology, tested an encounter between the sea slug and the Spanish shawl. The first time around the slug tried to eat the Spanish shawl, but quickly backed away when it discovered the shawl was toxic. The Spanish shawl then performed a strange and unnecessary escape dance. The second time the slug encountered the Spanish shawl it left before even trying to eat it. Take a look:
Gillette says, ""I had never seen that before! We began testing them and found that they were learning the odor of the Spanish shawl very specifically and selectively."
Gillette and his team later replicated that day's events by placing a Pleurobranchaea in a training arena 12-15 centimeters from a Spanish shawl, then recorded the Pleurobranchaea's behavior. They returned the Pleurobranchaea to the arena for four more trials in 20-minute intervals, then repeated the procedure at 24 and 72 hours later. In the experiments, Pleurobranchaea whose feeding thresholds were too high (meaning they were already full) or too low (they were extremely hungry) would either not participate or completely consume the Spanish shawl, respectively. Those Pleurobranchaea that were hungry, but not ravenously so, continued to exhibit the avoidance turn behavior when placed with the Spanish shawl even 72 hours later.
The research by Professor Gillette and his team appears here in the Journal of Experimental Biology.