Photoprotection by carotenoid pigments in the copepod Diaptomus nevadensis.

Abstract

Individuals of the copepod Diaptomus nevadensis that contain high concentrations of carotenoids survive significantly better in natural intensities of visible light than less pigmented copepods. Vertical migration and behavior in light of different wave lengths are related to the degree of pigmentation.Many investigators of aquatic communities have shown that the more visible zooplankters are the preferred prey of fish and other predators that hunt by sight (1-3). Strikingly visible, bright red copepods, however, are common in many lakes and ponds. While Nilsson and Pejler (4) showed that large red copepods occur in Swedish lakes only when the planktivorous whitefish (Coregonus) are absent or rare, the question of why any should be red remained unanswered.Diaptomus nevadensis Light, a calanoid copepod, is found in two lakes in central Washington. Those living in Lake Lenore are pale blue, clear, or only slightly red, while those in Soap Lake are deep red in color. Soap Lake is quite saline (17 g/liter) and contains no vertebrates, while a population of predatory salamanders (Ambystoma tigrinum, Green) is found in Lake Lenore (salinity 1.7 g/liter) as well as greater numbers of aquatic insects. In the laboratory, salamanders from Lake Lenore consume red copepods in preference to pale ones. Studies on stomach contents of animals from the lake are in progress.Species of Diaptomus have, in several cases, been shown to contain carotenoid pigments which give them their red color (5-7). While many hypotheses have been forwarded to explain this phenomenon, none had up to the present time been proven (8, 9). One of the more plausible of these explanations first proposed by Griffiths et al. (10) suggests that the carotenoids protect the animals from potentially damaging, visible wave lengths of light. These pigments have been shown by many investigators to enhance survival of a wide variety of bacteria and plants, probably by preventing the photooxidation of sensitive molecules (10-12). To the present, examples of this function in animals appear to be limited to trout eggs, mice, and humans (12).Reports of the damaging effect of visible light on copepods are common (13), and J. M. Harvey in 1930 showed that the cause could be attributed much more to blue light than to green or red (14). This agrees with the observation that porphyrins and flavins, likely candidates for the sensitizers in photodynamic action (11,15) To test the importance of these considerations in Diaptomus nevadensis, experiments were made comparing the survival of dark red copepods with that of pale copepods in natural intensities of light, and comparing their behavior in different colors of light. METHODSDiaptomus nevadensis were collected by plankton net and stored in the laboratory at 100. The animals were used within 5 days of capture to ensure that they were in good condition. Field measurements of light were made with a pyrheliometer and a submersible photocell with glass cut-off filters.Photodamage Experiments. Two experiments were run t...

Toward a more comprehensive theory of zooplankton diel vertical migration: Integrating ultraviolet radiation and water transparency into the biotic paradigm

“…This was clearly the thinking of many early prominent investigators who stated that ''the lethal ultra-violet light is rapidly absorbed and would not affect the Calanus in deep water'' (Marshall and Orr 1955), echoed by others as that ''solar radiation has in the past been denied as an ultimate cause of vertical migration on the basis that ultraviolet light does not penetrate more than two meters into water'' (Hairston 1976) and that ''protection from UV-light damage would not require deep migrations, as UV is absorbed in the uppermost water column'' (Lampert 1989). Yet in many of the clearer lakes and oceans of the world, the UV-A wavelengths to which zooplankton respond can penetrate to depths of tens to over 100 m and may thus be involved in driving DVM with much greater amplitudes than just a few meters.…”

“…Although variations in carotenoid concentrations in zooplankton were found to be related to dietary availability (Ringelberg 1980(Ringelberg , 1981Moeller et al 2005) and possibly temperature regulation (Byron 1981(Byron , 1982, extensive evidence accumulated on the important photoprotective function of carotenoids in copepods and melanin in cladocerans. In freshwater zooplankton, higher mortality of pale vs. pigmented individuals exposed to damaging wavelengths of light has been demonstrated for carotenoids in Diaptomus nevadensis (Hairston 1976), Heterocope septentrionalis (Luecke and O'Brien 1981), Acanthodiaptomus denticornis (Ringelberg et al 1984), and Leptodiaptomus minutus (Moeller et al 2005) as well as for melanin in Daphnia pulex obtusa (Siebeck 1978), Daphnia middendorffiana (Luecke and O'Brien 1983), Daphnia pulex (Hessen 1996), and the Daphnia pulex group (Hebert and Emery 1990). In both copepods and cladocerans, pale individuals exhibit stronger avoidance of damaging sunlight and are usually distributed more deeply in the water column than pigmented individuals (Hairston 1979;Luecke and O'Brien 1981;Hebert and Emery 1990).…”

Analysis of the seasonal variation in biochemical composition ofDaphnia magnaStraus (Crustacea : Branchiopoda : Anomopoda) from an aerated wastewater stabilisation pond

“…radiation (Hairston 1976, Siebeck 1978. In the pond of Differdange, the positive correlation between the carotenoid content of D. magna and water transparency, coupled with the fact that the pond is shallow and that no light refuge would exist, seems to confirm this hypothesis.…”

First record of a blue-pigmented Acartiid copepod in the tropical coral reef waters of Malaysia

“…Although the reason for the blue color in A. erythraea in the present study area is unknown, it may act to provide concealment from visual predators (i.e. animal color matches the background) and/or protection against UV radiation (Herring 1965, Hairston 1976.…”