In Sum

Natural History, March, 2001 by Richard Milner

DADDY'S NO BOOB According to some evolutionary biologists, males will act to favor the reproduction of their own genes at the expense of their rivals' genes. Male blue-footed boobies provide extensive parental care, including defending the nest, incubating the eggs, and helping to feed the chicks.

How can males prevent their prodigious labors in the seabird colony from profiting other males that may try to cuckold them while they are off gathering food? According to Marcela Osorio-Beristain and Hugh Drummond, of the Universidad Nacional Autonoma de Mexico, when an egg's paternity is in doubt, some male boobies push it out of the nest.

To test the male birds' reactions to eggs that may have been fertilized in their absence, the researchers (working on Isla Isabel, off Mexico's Pacific coast) removed a number of males from their nesting territory for ten to twelve hours and then returned them to their mates. One group of males was removed a few days before their females' fertile period (about a week before females lay their eggs); a control group had been temporarily isolated several weeks earlier. The scientists found that females did not suddenly become promiscuous while their mates were away. Some copulated with other males, but the rate of these pairings was low. Yet of the males sequestered just before the females' fertile period, 43 percent expelled the first-laid egg from the nest, although none of the control males did so.

The researchers concluded that a large proportion of male boobies will eliminate any possibility of lavishing their efforts on a "deadbeat dad's" offspring by destroying eggs of questionable paternity--even though some of them could be their own. ("Male Boobies Expel Eggs When Paternity Is in Doubt," Behavioral Ecology 12:1, 2000)

SMART SLIME Scientists at the Bio-Mimetic Control Research Center in Nagoya, Japan, placed blobs of the single-celled amoeba-like organism Physarum polycephalum inside a miniature maze in which four different routes led to food (ground oat flakes) placed at the start and end points. In a series of trials, the slime organism consistently chose the shortest path to reach the prize.

Classified as fungi, slime molds seem to share characteristics with both plants and animals. Like other fungi, they reproduce with spores, yet like amoebas, they can change shape and extend pseudopodia--tubelike legs with which they reach out to move and to absorb food. When pieces of a P. polycephalum were placed in the maze, they spread and coalesced to form a single organism spanning the shortest route from start to end. Then the mold extended its pseudopodia to connect the two food sources, reaching for a double helping.

The research team, led by Toshiyuki Nakagaki, concluded that the organism changes shape to maximize foraging efficiency, eventually forming one thick tube covering the shortest distance between food sources--a "cellular computation" demonstrating a "primitive intelligence." ("Maze-Solving by an Amoeboid Organism," Nature 407, 2000)

BALLISTIC TONGUE Chameleons are welt known for being able to change color but also for their spectacular ability to capture prey by shooting out their long, sticky tongues. White many other kinds of lizards can extend their tongues to seize small prey, only chameleons have evolved a powerful suction device: a pouch on the lingual tip. This pouch enables them to grab birds and lizards as heavy as 15 percent of the chameleons' body weight--a feat comparable to a 150-pound man lifting a 22-pound weight with this tongue. Using high-speed video, X rays, and electromyography, a team led by Anthony Herrel, of the University of Antwerp, and Jay Meyers, of Northern Arizona University, has elucidated the mechanism in various chameleon species.

Herpetologists already knew that chameleons had a pair of pouch-retractor muscles in their tongues, but it was thought that the pouch splayed open on contact with prey, creating suction. Herrel, Meyers, and colleagues have shown that these muscles actually open the pouch just before contact and that two modified muscles then pull the tongue pad inward. (When the researchers cut the special nerves that extend into the pouch-retractor muscles, the chameleons were unable to hold onto their targeted meal.) These intricate, coordinated movements, including the full retraction of the tongue with its captive, are completed in less than haft a second, The suction adaptation, the team believes, arose when the lizards took to the trees, where targeted prey would fall if not instantly well secured. ("The Mechanics of Prey Prehension in Chameleons," Journal of Experimental Biology 203, 2000)