Navigation Links
Seeing how evolutionary mechanisms yield biological diversity
Date:12/22/2009

COLLEGE PARK, Md. -- An international team of scientists has discovered how changes in both gene expression and gene sequence led to the diversity of visual systems in African cichlid fish.

In research published in the December 21, 2009 issue of the journal PLoS Biology, Assistant Professor Karen Carleton, together with post-doctoral associate Chris Hofmann and graduate student Kelly O'Quin, in the University of Maryland Department of Biology, and collaborators Justin Marshall, University of Queensland; Tom Cronin, University of Maryland, Baltimore County (UMBC); and Ole Seehausen, University of Bern; describe how over 60 species of cichlid fish from Lake Malawi and Lake Victoria have adapted their visual sensitivity in response to specific ecological factors, including what they eat and the clarity of the water in which they swim.

Evolutionary biologists seek to understand the mechanisms behind genetic changes that have led to the vast diversity of life on Earth. There are two important molecular mechanisms that contribute to organismal diversity - changes to the sequence of genes, and changes in the way genes are expressed, including when, where, and how much of a gene is made. This study was one of the first to look at how both gene sequence and gene expression can contribute to the same trait, and showed that they contribute in complementary ways.

"African cichlid fishes are some of the most diverse animals on the planet. Their visual systems differ dramatically in their sensitivity and represent some of the largest differences known in vertebrates," explains Hofmann. "Yet there has been little understanding as to why such diversity exists. Our findings have important implications for understanding both the factors and the mechanisms responsible for generating biodiversity."

Cichlids have several different cone opsin genes that enable them to detect light across the visible and ultraviolet regions of the spectrum. Different species express different subsets of these opsins to create alternate visual systems. The research team found that cichlid fish in the clear waters of Lake Malawi expressed a wide range of opsins, with closely related species differing in whether they used the shorter wavelength or longer wavelength gene combinations.

The method of foraging for food was a key factor influencing fish vision. Fish whose diets consist primarily of zooplankton were more likely to have UV sensitivity, which enables them to detect the presence of these small transparent aquatic organisms that absorb ultraviolet light. In contrast, cichlids in the murky waters of Lake Victoria expressed longer wavelength combination of opsin genes, regardless of what they ate.

This long wavelength combination matches the light that is best transmitted through the murky water. A few Lake Victoria fish at clearer sites turned on shorter wavelength genes, suggesting that opsin expression matches the light environment. Therefore opsin gene expression in both lakes is adaptively determined based on important ecological variables.

The authors also examined changes in the genetic sequence of these opsins that fine-tuned visual pigment sensitivity at the short and long-wavelength ends of the spectral range.

"When you get to the extremes of the light spectrum, there is no other gene that can be turned on or off, so the only way to extend the sensitivity is to change the gene structure itself," says O'Quin. Therefore, this study presents a model of sensory evolution in which both molecular genetic mechanisms work in concert.

For a copy of the paper go to: http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1000266

Previous work by Ole Seehausen, Karen Carleton, Nori Okada and colleagues (Nature, 455, 620-626, 2 October 2008) has demonstrated that color vision plays a key role in how cichlids recognize different species and choose mates. (Read more about thiis work here: http://www.newsdesk.umd.edu/scitech/release.cfm?ArticleID=1752)

"Previously, we showed that changes in opsin gene sequence contributed to generating new species," says Carleton. "The speed with which opsin gene expression changes suggests that it might also contribute to creating the incredible diversity of cichlid fishes."

The authors are extending their work to other African Great Lakes and even to coral reef fishes, to better understand how biodiversity is formed.


'/>"/>

Contact: Kelly Blake
kellyb@umd.edu
443-851-0272
University of Maryland
Source:Eurekalert

Related biology news :

1. Seeing Alzheimers amyloids
2. Crystal (eye) ball: Study says visual system equipped with future seeing powers
3. Seeing through the skin
4. Seeing stem cells helps in fight against peripheral arterial disease
5. Seeing the tree from the forest: Predicting the future of plant communities
6. Seeing previously invisible molecules for the first time
7. Seeing is relieving
8. Seeing family for the holidays? Scientists discover how the stress might kill you
9. Clones on task serve greater good, evolutionary study shows
10. Adaptation to parasites drive African fishes along different evolutionary paths
11. Old developmental pathways spawn revolutionary evolutionary changes
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/15/2016)... -- A new partnership announced today will help life ... a fraction of the time it takes today, ... insurance policies to consumers without requiring inconvenient and ... rapid testing (A1C, Cotinine and HIV) and higi,s ... pulse, BMI, and activity data) available at local ...
(Date:3/31/2016)...   LegacyXChange, Inc. ... LegacyXChange is excited to release its first ... be launched online site for trading 100% guaranteed authentic ... also provide potential shareholders a sense of the value ... industry that is notorious for fraud. The video is ...
(Date:3/22/2016)... India , March 22, 2016 /PRNewswire/ ... market research report "Electronic Sensors Market for Consumer ... Proximity, & Others), Application (Communication & IT, ... Geography - Global Forecast to 2022", published ... industry is expected to reach USD 26.76 ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... 27, 2016  Global demand for enzymes is ... 2020 to $7.2 billion.  This market includes enzymes ... products, biofuel production, animal feed, and other markets) ... biocatalysts). Food and beverages will remain the largest ... consumption of products containing enzymes in developing regions.  ...
(Date:6/27/2016)... ... June 27, 2016 , ... Parallel 6 , ... announced today the Clinical Reach Virtual Patient Encounter CONSULT module which enables ... the physician and clinical trial team. , Using the CONSULT module, patients and physicians ...
(Date:6/27/2016)... 27, 2016   Ginkgo Bioworks , a leading ... was today awarded as one of the World ... world,s most innovative companies. Ginkgo Bioworks is engineering ... real world in the nutrition, health and consumer ... with customers including Fortune 500 companies to design ...
(Date:6/24/2016)... NC (PRWEB) , ... June 24, 2016 , ... Researchers ... the most commonly-identified miRNAs in people with peritoneal or pleural mesothelioma. Their findings are ... to read it now. , Diagnostic biomarkers are signposts in the blood, lung ...
Breaking Biology Technology: