miércoles, 10 de noviembre de 2010
New Self-Cloning Lizard Found in Vietnam Restaurant
You could call it the surprise du jour: A popular food on Vietnamese menus has turned out to be a lizard previously unknown to science, scientists say.
What's more, the newfound Leiolepis ngovantrii is no run-of-the-mill reptile—the all-female species reproduces via cloning, without the need for male lizards.
Single-gender lizards aren't that much of an oddity: About one percent of lizards can reproduce by parthenogenesis, meaning the females spontaneously ovulate and clone themselves to produce offspring with the same genetic blueprint.
(Related: "Virgin Birth Expected at Christmas—By Komodo Dragon.")
"The Vietnamese have been eating these for time on end," said herpetologist L. Lee Grismer of La Sierra University in Riverside, California, who helped identify the animal.
"In this part of the Mekong Delta [in southeastern Vietnam], restaurants have been serving this undescribed species, and we just stumbled across it."
Wild Lizard Chase
Grismer's Vietnamese colleague Ngo Van Tri of the Vietnam Academy of Science and Technology found live lizards for sale in a restaurant in Ba Ria-Vung Tau Province (see map).
Noting that the reptiles all looked strangely similar, Ngo sent pictures to Grismer and his son Jesse Grismer, a herpetology doctoral student at the University of Kansas.
The father-son team suspected that they may be looking at an all-female species. That's because the team knew that the lizard likely belonged to the Leiolepis genus, in which males and females in lizards have distinct color differences—and no males were apparent in the photos.
So the pair hopped on a plane to Ho Chi Minh City (Saigon), telephoned the restaurant to "reserve" the lizards, and began an eight-hour motorcycle odyssey—which ended in disappointment.
"When we finally got there, this crazy guy had gotten drunk and served them all to his customers," recalled Lee Grismer, who has received funding for other projects from the National Geographic Society's Committee for Research and Exploration. (The Society owns National Geographic News.)
Fortunately other area restaurants had the lizards on offer, and local schoolchildren helped gather more from the wild. Eventually the Grismers examined almost 70 of the lizards—and all turned out to be females.
Who's Your (Lizard) Daddy?
The newfound reptile also had rows of enlarged scales on its arms as well as lamellae—bone layers—under its toes that set it apart from other species, according to the study, published April 22 in the journal ZOOTAXA.
The species is probably a hybrid from maternal and paternal lines of two related lizard species, a phenomenon that can occur in transition zones between two habitats. For instance, the new lizard's home, the Binh Chau-Phuoc Buu Nature Reserve, sits between scrub woodland and coastal sand dunes.
"So species that do really well in one habitat or the other will occasionally get together and reproduce to form a hybrid," Grismer said.
Genetic tests of the new lizard's mitochondrial DNA identified its maternal species as L. guttata. Because this type of DNA is passed down only through females, the paternal species isn't yet known.
New Reptile May Be in Hot Water
The newly discovered hybrid species may already be at a disadvantage, Grismer added—even though it doesn't seem to be rare in the wild.
For instance, some scientists suggest that hybrid species are more prone to extinction because they don't produce much genetic diversity from generation to generation, according to herpetologist Charles Cole, curator emeritus at the American Museum of Natural History in New York.
Genetic diversity keeps a species viable and healthy in the long term.
"At least in terms of lizards, most that are unisexual species—when compared to the lineages of other lizards—have not been around very long," said Cole, who was not involved with the Grismers' research.
Because the lizards don't combine genes during mating, genetic changes arise by random mutations—which are at least as likely to be detrimental as beneficial.
Lizard Hybrid Hardy as a Mule?
However, Cole cautioned, there are also theories that hybrids can be healthier in the short term.
For instance, a hybrid's cells may be more genetically diverse than those of nonhybrids, because hybrids carry genes from each of their parent species.
"This might mean that the animals are tougher and more adaptable," Cole said.
For instance, he said, mules—crosses between horses and donkeys—"are sterile, but they are really good robust animals that are in some ways a preferred work animal even though they can't reproduce."
"So what you get in the unisexual lizards is a mule that can clone itself."