![]() "They chase each other, they bite, they hit each other with their tails. "They're surprisingly vigorous fighters," said Dr. All the meek males in the neighborhood rush over, seeking to fill the vacancy, and a series of violent battles commences. The colorful fish are easily seen and predated upon, and once a dominant male disappears, a remarkable event occurs. The Price of Gloryīut it turns out that the flamboyance of machismo has its price. By contrast, both females and subordinate males have cryptic, sand-colored scales and are unlikely to pick a fight. Dominant males are larger and more brilliantly colored, with bold orange stripes and fins that gleam like rainbows, and they are extremely aggressive. Those few males, he realized, differed spectacularly from their timid counterparts. Studying the species Haplochromis burtoni, he noticed that only 10 percent of the males controlled all the feeding territory and all access to females. Fernald began his research at Lake Tanganyika in Africa, home to 150 species of cichlid fish. Fernald's new study.īut researchers concur that it will be far more difficult to decipher the meaning of brain differences in people than it is to investigate the neurobiology of fish.ĭr. Simon LeVay of the Salk Institute in La Jolla, Calif., who stirred an acrimonious debate recently when he said he had detected a difference in the hypothalamus between homosexual and heterosexual men, has expressed great interest in Dr. Fernald suggests that the architecture of the human brain may also be affected by a person's behavior. Because the brain molecules under study are highly conserved across the evolutionary spectrum, Dr. The findings may also have implications for a few finless creatures, including people. This goes a long way toward solving the nature-nurture debate, which was a false debate to begin with." ![]() "Here you have this animal whose social state is translated into changes in the cells of the hypothalamus, which then contribute to the animal's augmented reproductive capacity. Kelley, a biologist at Columbia University who studies frog mating songs. "This is a marvelous example of how the social environment influences animal biology," said Dr. And after the hypothalamic cells have shrunk, the male's testes follow suit, eventually robbing the fish of its desire and ability to breed. Should the domineering male be confronted by a larger male able to bully it, the neurons of the defeated fish will rapidly shrink. Fernald has found that the dimensions of those cells are extremely plastic. Russell Fernald, a neurobiologist at Stanford University, has discovered that in aggressive males that command large territories and keep contending males at bay, brain cells in the hypothalamus that allow the fish to mate are six to eight times larger than are equivalent cells in mild-mannered males with no social clout. AMONG males of many species, from elephant seals to human beings, the struggle to prevail over competing males often seems to dwarf all other tasks - and perhaps with good reason.Ī scientist has discovered that how a male fish interacts with other males, and whether it is socially dominant or a tremulous wimp, has such a profound effect on the creature that it changes the brain cells in charge of the fish's capacity to breed.
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