SAMPLINGS 



Love Potion 



Musth is the annual season of sexual activity 

 and aggression in male elephants. Glands on 

 the male's face release frontalin, a pheromone 

 that comes in two highly similar forms. In 

 fact, the molecule of one is simply the mirror 

 image of the other. New research shows it's 

 the ratio of the two forms that matters to 

 other elephants. 



A team biologists led by David R. Green- 

 wood of HortResearch in Auckland, New 

 Zealand, discovered that adult male Asian ele- 

 phants secrete nearly equal amounts of the 

 two forms of frontalin. The secretions are 

 most evenly balanced during the peak of 

 musth. Juveniles, by contrast, secrete lower 

 concentrations of both forms than adults do, 

 and the balance is skewed in favor of one of 

 the forms. 



The biologists presented elephants with 

 mixtures of the two frontalin forms in differing 



Three Stars 

 in One 



The most familiar twinkle in the night 

 sky has been keeping a secret. The 

 North Star, it turns out, is not just the 

 two stars (Polaris and a smaller com- 

 panion) that were already known. As- 

 tronomers have now caught sight of 

 number three — though just barely. 

 Nancy Evans of the Harvard-Smithson- 

 ian Center for Astrophysics in Cam- 

 bridge, Massachusetts, and her col- 

 leagues needed the full optical power of 

 the Hubble Space Telescope to see it. 

 The third star is so small, and so "close" 

 to Polaris (about 2 billion miles, or 

 roughly the distance between our Sun 

 and the planet Uranus), that it's all but 

 washed out in the glare of the main star. 



—S.R. 



Under the influence of pheromones? 



ratios. Males and nonovulating females moved 

 away from balanced secretions — the equivalent 

 of giving a wide berth to a horny male who's 

 itching for a fight. Ovulating females had just 

 the opposite reaction: they actively sniffed and 



Jamming the Signal 



Most moths' ears have evolved for one pur- 

 pose: to help the moth avoid being eaten by a 

 bat. Moth ears are tuned to hear bat echoloca- 

 tion calls, which trigger behaviors in the moth 

 that help it escape. Many moth species may 

 even foil bat attacks by mimicking the calls of a 

 bat on the hunt. The resulting cacophony may 

 so confuse the bat — in effect, jamming its 

 "radar" — that it fails to locate its prey. A bat 

 may also learn to associate the clicking sounds 

 of a moth with an unpalatable meal, reducing 

 the chances that the bat will attack. 



Surprisingly, though, no one had ever 

 recorded and studied moth clicks during a bat 

 attack under natural conditions. Now two sen- 



Sneaky Genes 



Some bacteria are masters of deception. Take 

 Pseudomonas syhngae, the species that 

 causes halo blight, a devastating disease in 

 bean crops. When the bacteria infect a bean 

 plant, they release proteins that disable the 

 plant's defense system. Resistant varieties of 

 bean, however, have come up with a counter- 

 measure. They recognize the hostile proteins 

 and respond by releasing antimicrobial com- 

 pounds. That's when the bacteria turn sneaky. 

 Subsequent generations lose the genes that 

 encode the offending proteins. Once they no 

 longer trigger the plant's defenses, they steal 

 in to launch a ferocious infection. But how and 

 when do the bacteria unload the genes? 



stayed close to the samples. What's more, re- 

 ceptive females preferred the most evenly bal- 

 anced mixtures, Greenwood says. Apparently 

 that's the recipe for elephant romance. [Nature 

 438:1097-8,2005) —S.R. 



sory ecologists, John M. Ratcliffe of Cornell 

 University in Ithaca, New York, and James H. 

 Fullard of the University of Toronto in Ontario, 

 have done just that. They observed that moth 

 sounds did affect bat predation, but only dur- 

 ing aerial attacks. 



Just as the bat is making its final decision to 

 attack — about half a second before reaching 

 its target — a dogbane tiger moth begins emit- 

 ting clicks from organs called tymbals, on the 

 thorax. Although such a delayed defense 

 makes for close calls, it usually works: moths 

 with intact tymbals were attacked significantly 

 less often than were moths whose tymbals 

 had been disabled by the investigators. 

 (The Journal of Experimental Biology 

 208:4689-98, 2005) —N.W.A. 



Two molecular plant pathologists, Andrew 

 R. Pitman of the University of the West of 

 England in Bristol and John W. Mansfield of 

 Imperial College London, and their colleagues 

 infected a resistant variety of the common 

 bean Phaseolus vulgaris with the halo-blight 

 pathogen and analyzed the resulting bacterial 

 genome. They discovered that the bacteria re- 

 spond to the plant's defenses by jettisoning a 

 portion of their DNA that includes a gene for 

 one of the proteins in question. Along with 

 the protein-coding gene go other advanta- 

 geous, though not essential, genes. But a 

 puzzle remains: Why does the species retain 

 the genes that betray its presence to the 

 plant in the first place? (Current Biology 

 1 5:2230-5, 2005) —Graciela Flores 



16 



NATURAL HISTORY March 2006 



