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PUBLIC RELEASE DATE:
25-Jan-2010

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Contact: Graeme Baldwin
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BioMed Central
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Lopsided fish show that symmetry is only skin deep

IMAGE: This is an image of a cichlid fish, Perissodus elaviae.

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Putting function before form, members of the Perissodinus genus of fish have developed a hugely lopsided jaw that provides a distinct feeding advantage. Research published in the open access journal BMC Biology describes how these scale-eating fish, called cichlids, develop mouths directed either to the left or the right - enabling them to feed on the opposite side of their prey.

A research team from Syracuse University, led by Thomas Stewart and R. Craig Albertson, studied the facial evolution of cichlids from Lake Tanganyika in eastern Africa, where they feed on the scales of larger lake-dwellers. According to Stewart, "While most animals have bilateral symmetry and some show a radial symmetry, asymmetries are actually relatively common in nature. For example, humans can be either left handed or right handed, and one side of the brain is structured differently to the other. Often, both the trait and whether it is placed on the left or right are genetically determined, and the population as a whole tends to show the same characteristic. For example, most people have their heart positioned slightly to the left".

The research team found that there is a genetic locus that determines whether a cichlid will be a 'lefty' or a 'righty'. However, they add that these developmental divergences are more complicated than originally thought. "Some scale-eaters start off with balanced mouths, and others do not. So, what happens as these symmetrical fish get older: do they develop asymmetries due to lateralized foraging behaviors? Do they develop asymmetries due to lateralized growth? Do they die because they are not effective hunters?" debates researcher Craig Albertson. He continues, "All three are possible, but we do not have data to support any one of these scenarios. It would seem, however, that in this group an innate, genetically-determined left/right difference has been accentuated to enable a bizarre predatory life style."

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Notes to Editors

1. Evolution of a unique predatory feeding apparatus: functional anatomy, development and a genetic locus for jaw laterality in Lake Tanganyika scale-eating cichlids
Thomas A Stewart and R. Craig Albertson
BMC Biology (in press)

During embargo, article available here

After the embargo, article available at journal website

Please name the journal in any story you write. If you are writing for the web, please link to the article. All articles are available free of charge, according to BioMed Central's open access policy.

Article citation and URL available on request at press@biomedcentral.com on the day of publication

2. Images of Cichlids are available here:

http://www.biomedcentral.com/graphics/email/images/a.jpg
http://www.biomedcentral.com/graphics/email/images/b.jpg
http://www.biomedcentral.com/graphics/email/images/d.jpg

3. BMC Biology - the flagship biology journal of the BMC series - publishes research and methodology articles of special importance and broad interest in any area of biology and biomedical sciences. BMC Biology (ISSN 1741-7007) is covered by PubMed, MEDLINE, BIOSIS, CAS, EMBASE, Scopus, Zoological Record, Thomson Reuters (ISI) and Google Scholar.

4. BioMed Central (http://www.biomedcentral.com/) is an STM (Science, Technology and Medicine) publisher which has pioneered the open access publishing model. All peer-reviewed research articles published by BioMed Central are made immediately and freely accessible online, and are licensed to allow redistribution and reuse. BioMed Central is part of Springer Science+Business Media, a leading global publisher in the STM sector.



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