Learning to Adapt
 Jelle Atema: A Fine Sense of Smell
Marine biologist Jelle Atema has a discriminating palate—and a connoisseur’s nose for fine food and wine. Each spring he collects a new crop of lobsters from the waters near his laboratory in Woods Hole, Massachusetts—for his observation tank, not for his dinner table—where he investigates this crustacean’s curiously fine sense of smell.
After arriving on Cape Cod in the 1970s from his native home in the Netherlands, Atema searched for a model animal to reveal the secrets of chemical messaging between aquatic species. Lobsters, it turned out, proved to be a very good model for learning about social communication. He has studied them for decades, producing a wealth of knowledge about chemical communication in this species.
Atema’s recent work reveals even more complexity in what he calls the “underwater odor world.” The whole social structure of lobsters is held together by chemical recognition of dominance, sex differences, and molting state, he explains. “It’s remarkable that what humans consider a higher-animal behavior is found in what’s known as a lower animal.” Male lobsters fight to establish dominance, and the losing male, in subsequent encounters, will back down to avoid another fight with a previous victor. The animals identify each other individually by “smelling” odors in urine released during the fight. 
Lobsters have five major chemoreceptive organs on a variety of antennae and hairs projecting from their heads and legs. One hair type, known as aesthetasc sensilla, leads directly to the olfactory (odor-receptive) area of the brain. You can see them flick in a quick downstroke, a sniffing-like action, says Atema. He hypothesized that receptors in these hairs might allow lobsters to recognize an individual’s unique scent.
To test the theory, Atema pitted male lobsters, either with or without the hairs, against one another in a fight for dominance. In round two, he measured how long the weaker lobster challenged the dominant one. Male lobsters that had their aesthetasc sensilla removed spent longer challenging the dominant males, seeming not to remember their vanquishers from round one. “Without any doubt,” Atema says, “this experiment shows that for individual recognition lobsters need aesthetasc sensilla.”
Atema’s newest collection of lobsters will help him search for the specific urine chemicals to which the hairs react. The immune system of humans and other vertebrate animals is based on gene families called the major histocompatibility complex (MHC). These genes generate chemicals that protect the body from foreign invaders and provide individual odors. “Now comes the kicker,” says Atema. “In invertebrates like lobsters, no MHC system is known. So how do they do it?”
 His next step is to painstakingly hone down the list of urine chemicals to the ones essential for individual recognition. He expects that it might be a protein of similar structure and size to the MHC, but because this is “totally novel research,” Atema says, his mind is open to all possibilities. “As soon as you know the chemistry, a whole new world opens up because you can talk about the evolution of these substances, their sources, their function besides recognition, and their role in neurobiology.” He compares the yet-unknown recognition chemicals to unexplored territory: “The exciting part is that we just don’t know what we’ll find when we get there.”
This research was published in the August 1, 2005, issue of The Journal of Experimental Biology.
To find out more about the Boston University Marine Program, visit www.bu.edu/bump/.
— by Leah Eisenstadt |
