. Earth Science News .
Adaptation To Parasites Drive African Fishes Along Different Evolutionary Paths

The East African cichlid fish Pseudotropheus emmiltos.
by Staff Writers
Quebec City, Canada (SPX) Aug 24, 2007
An international team of scientists from Canada (Universite Laval), the U.K. (University of Hull, Cardiff University) and Spain (Dooana Biological Station), have discovered that a pair of closely related species of East African cichlid fishes - a group of fish whose diversity comprising hundreds of species has puzzled evolutionary biologists for decades - evolved divergent immune gene adaptations which might explain why they do not interbreed, despite living side by side.

The two species ( Pseudotropheus emmiltos and Pseudotropheus fainzilberi ) are found in the north western part of Lake Malawi. Until now, the only known difference between them was the color of their dorsal fin. Many researchers believe that African cichlids recognize conspecifics from these kinds of colour differences, which are thought to result from sexual selection. However, recent mate choice experiments have shown that female P. emmiltos recognize males of their own species from P. fainzilberi males based on olfactory communication rather than color.

Some of the genes known to influence mating behavior through olfaction in other vertebrate species are genes of the major histocompatibility complex (MHC). These genes code for receptor that bound molecules produced by infectious agents and present them to specialized cells of the immune system which then launch an immune attack on the microbes. They are the most diverse genes found in vertebrate genomes and individuals of some species, including humans, are able to "smell" other individuals' variability at these genes and adjust their mate choice in order to optimize the effectiveness of their offspring's immune system. Analysis of MHC genes between P. emmiltos and P. fainzilberi revealed that the two species were genetically more different at these sites involved in contacting and presenting molecules to immune cells than at other sites of the gene's DNA sequence that do not play functional roles.

These results show that natural selection has driven the evolution of these genes in different direction between the two species. Furthermore, the researchers showed that infecting parasites found on the two species were significantly different, as predicted based on the known immune function of MHC genes. "The mechanisms having produced the hundreds of species of East African cichlid fishes in a relatively short period of time are unclear", says Jonatan Blais, the senior author of the paper." This is one of the first genetic adaptive differences between closely related East African cichlid species identified. As such, it improves our understanding of the recent evolution of this incredibly diverse group of fish by pointing to a trait that not only diverged for adaptive reasons but may also be involved in mating behavior."

"The precise role that this divergence played in the evolution of reproductive isolation has yet to be studied", comments Louis Bernatchez, co-author of the study." But it offers an exciting new perspective in the study of African cichlids speciation ".

The study appears in the August 15 issue of the online, open-access journal PLoS ONE which can be seen here.

Community
Email This Article
Comment On This Article

Related Links
Public Library of Science
Darwin Today At TerraDaily.com



Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News


White Rice A Mutation Spread By Early Farmers
Ithaca NY (SPX) Aug 24, 2007
Some 10,000 years ago white rice evolved from wild red rice and began spreading around the globe. But how did this happen? Researchers at Cornell and elsewhere have determined that 97.9 percent of all white rice is derived from a mutation (a deletion of DNA) in a single gene originating in the Japonica subspecies of rice. Their report, published online in the journal PloS (Public Library of Science) Genetics, suggests that early farmers favored, bred and spread white rice around the world.







  • Death toll mounts as floods, heat wave batter US
  • Dean's death toll rises with new deaths in Mexico
  • Wave of refugees quits Peru quake ruins
  • Ground-Breaking Antilandmine Radar

  • Corals And Climate Change
  • Climate Change Goes Underground
  • Climate Change Goes Underground
  • UK Satellite Mission To Improve Accuracy Of Climate-Change Measurements Gains Global Support

  • European Hot Spots And Fires Identified From Space
  • China Develops Beidou Satellite Monitoring System
  • DigitalGlobe Announces Launch Date For WorldView-1
  • Radar reveals vast medieval Cambodian city: study

  • Russian Oil Export Duty Could Rise To 250 Dollars Per Ton
  • Russia's Stroytransgaz Completes Gas Pipeline In Greece
  • China's CNPC To Fund Cross-Country Gas Pipeline From Central Asia
  • Boeing Projects 70 Billion Dollar Market For Russia And The CIS

  • Nanoparticle Could Help Detect Many Diseases Early
  • China probably 'covered up' pig disease outbreaks
  • Online gamers rehearse real-world epidemics
  • Features Of Replication Suggest Viruses Have Common Themes And Vulnerabilities

  • Adaptation To Parasites Drive African Fishes Along Different Evolutionary Paths
  • Structure Of 450 Million Year Old Protein Reveals Evolution Steps
  • White Rice A Mutation Spread By Early Farmers
  • Giant Panda Could Survive As An Evolutionary Development

  • Team Tracks Antibiotic Resistance From Swine Farms To Groundwater
  • e-Science Points To Pollution Solutions
  • Toxic Air Pollution In Urban Parking Garages Study Finds SUVs Bigger Polluters
  • Follow Your Nose: Houston Air Quality Study Finds A Few Surprises

  • Area Responsible For Self-Control Found In The Human Brain
  • Milestone In The Regeneration Of Brain Cells: Supportive Cells Generate New Nerve Cells
  • Gene Regulation, Not Just Genes, Is What Sets Humans Apart
  • 3-D Brain Centers Pinpointed

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2007 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement