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Zebrafish use sunscreen also for camouflage

Date:
January 29, 2014
Source:
University of Zurich
Summary:
For diurnal animals like zebrafish embryos, which grow up in shallow pools and are practically see-through, exposure to the sun constitutes a major problem since ultraviolet (UV) radiation damages DNA. Neurobiologists set about investigating which mechanisms zebrafish embryos use to protect themselves against the aggressive UV radiation. Interestingly, scientists have found that the UV-protection mechanism also doubles as camouflage. 
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Camouflage among zebrafish larvae. The left-hand larva is exposed to bright light and has little pigmentation; the right-hand larva against a dark subsurface is more heavily pigmented and thus camouflaged.
Credit: UZH

For diurnal animals like zebrafish embryos, which grow up in shallow pools and are practically see-through, exposure to the sun constitutes a major problem since ultraviolet (UV) radiation damages DNA. Neurobiologists Stephan Neuhauss and Kaspar Müller from the Institute of Molecular Biology at the University of Zurich set about investigating which mechanisms zebrafish embryos use to protect themselves against the aggressive UV radiation. Interestingly, the two scientists reveal in their article, recently published in the journal PLOS ONE, that the UV-protection mechanism also doubles as camouflage.

Sunscreen already from day two

For their study, the scientists examined zebrafish embryos, the skin cells of which already possess pigments known as melanosomes from the second day after fertilization -- even before their eyes have developed. "In strong solar radiation, the pigments spread along predetermined paths within the cells, after which the zebrafish embryo appears darker," explains Neuhauss. As the researchers discovered, this distribution process of dark pigments in the presence of intense light always takes place, regardless of whether the embryo is on a light or dark subsurface. Surprisingly, the embryos display a noticeable change from the third day after fertilization: They adapt to the subsurface. According to Neuhauss, this is because the embryos can see from day three and have eyes with UV-sensitive photoreceptors in the retina. From this moment on, they are able to discern whether they are on a light or dark subsurface and can adapt and thus camouflage themselves accordingly. As long as the animal is in the embryonic stage and see-through, however, the benefits of UV protection prevail.

When the skin is no longer transparent and does not require protection against aggressive radiation, the selective distribution of the pigments within the skin cells is predominantly used for camouflage purposes. And with good reason: Being able to adapt to a lighter or darker subsurface and camouflage yourself reduces the chance of being spotted and eaten. "The original UV protection turns into a camouflage mechanism -- a striking example of the secondary use of an existing capability," Neuhauss concludes.


Story Source:

The above post is reprinted from materials provided by University of Zurich. Note: Materials may be edited for content and length.


Journal Reference:

  1. Kaspar P. Mueller, Stephan C. F. Neuhauss. Sunscreen for Fish: Co-Option of UV Light Protection for Camouflage. PLoS ONE, 2014; 9 (1): e87372 DOI: 10.1371/journal.pone.0087372

Cite This Page:

University of Zurich. "Zebrafish use sunscreen also for camouflage." ScienceDaily. ScienceDaily, 29 January 2014. <www.sciencedaily.com/releases/2014/01/140129184658.htm>.
University of Zurich. (2014, January 29). Zebrafish use sunscreen also for camouflage. ScienceDaily. Retrieved August 28, 2015 from www.sciencedaily.com/releases/2014/01/140129184658.htm
University of Zurich. "Zebrafish use sunscreen also for camouflage." ScienceDaily. www.sciencedaily.com/releases/2014/01/140129184658.htm (accessed August 28, 2015).

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