Abstract
Ultraviolet (UV) radiation is harmful to all life, and the ongoing depletion of the ozone layer is likely to affect interactions among both terrestrial and aquatic organisms. Some organisms have evolved adaptations to reduce radiation damage, such as the various types of protective pigmentation of freshwater zooplankton. However, strong pigmentation also increases vulnerability to visually hunting predators. Hence, where both UV radiation and predation are intense, zooplankton may be sandwiched between conflicting selective pressures: to be pigmented and to be transparent at the same time. Here, I show that the level of pigmentation in copepods is up to ten times higher in lakes without predatory fishes than where fishes are present. Moreover, animals from the same population exposed to either UV light or predator scent showed a 10% difference in pigmentation after only four days, suggesting that pigmentation is an inducible trait. Hence, individual copepods are not passive victims of selective predation or radiation damage, but adjust the level of pigmentation according to the prevailing threat. The ability to adjust pigmentation level rapidly may be especially useful in situations where risk assessment is difficult due to strong seasonal and spatial variation in risk variables, such as in Arctic regions. With progressive thinning of the ozone layer, the ability of some but not other organisms to adjust protection against UV radiation may lead to counter-intuitive, large-scale alterations in freshwater food webs.
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Selected References
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- Agrawal AA. Induced responses to herbivory and increased plant performance . Science. 1998 Feb 20;279(5354):1201–1202. doi: 10.1126/science.279.5354.1201. [DOI] [PubMed] [Google Scholar]
- Bothwell M. L., Sherbot D. M., Pollock C. M. Ecosystem response to solar ultraviolet-B radiation: influence of trophic-level interactions. Science. 1994 Jul 1;265(5168):97–100. doi: 10.1126/science.265.5168.97. [DOI] [PubMed] [Google Scholar]
- Brönmark C., Miner J. G. Predator-induced phenotypical change in body morphology in crucian carp. Science. 1992 Nov 20;258(5086):1348–1350. doi: 10.1126/science.258.5086.1348. [DOI] [PubMed] [Google Scholar]
- Harkany T., Dijkstra I. M., Oosterink B. J., Horvath K. M., Abrahám I., Keijser J., Van der Zee E. A., Luiten P. G. Increased amyloid precursor protein expression and serotonergic sprouting following excitotoxic lesion of the rat magnocellular nucleus basalis: neuroprotection by Ca(2+) antagonist nimodipine. Neuroscience. 2000;101(1):101–114. doi: 10.1016/s0306-4522(00)00296-7. [DOI] [PubMed] [Google Scholar]
- Harvell C. D. The ecology and evolution of inducible defenses. Q Rev Biol. 1990 Sep;65(3):323–340. doi: 10.1086/416841. [DOI] [PubMed] [Google Scholar]
- Hill H. Z. The function of melanin or six blind people examine an elephant. Bioessays. 1992 Jan;14(1):49–56. doi: 10.1002/bies.950140111. [DOI] [PubMed] [Google Scholar]
- Krieger J., Breer H. Olfactory reception in invertebrates. Science. 1999 Oct 22;286(5440):720–723. doi: 10.1126/science.286.5440.720. [DOI] [PubMed] [Google Scholar]