|Year : 2008 | Volume
| Issue : 2 | Page : 137-141
Phototoxicological studies of riboflavin and chloroquine on Daphnia magna
Sunil Kumar, Prashsti Mishra, Bharat Singh Rawat
Environmental Toxicology Laboratory, Department of Zoology, D.A.V. (P.G.) College, Dehradun -248001, Uttarakhand, India
|Date of Submission||26-Feb-2008|
|Date of Acceptance||08-Aug-2008|
|Date of Web Publication||5-Jun-2010|
Environmental Toxicology Laboratory, Department of Zoology, D.A.V. (P.G.) College, Dehradun -248001, Uttarakhand
| Abstract|| |
The effect of solar and ultraviolet (UV-B) radiation has been examined on Daphnia magna in presence of riboflavin and chloroquine. Daphnia magna were divided into nine groups and exposed to natural solar light and UV-B individually and in combination of riboflavin and chloroquine. Exposure lasted for 3 days with the duration of 1 hour per day. Results on mortality rate indicates that mortality was highest 62% in chloroquine + ultraviolet-B exposed group, 49% in solar radiation + chloroquine exposure, 39% after chloroquine treatment, 38% in Ultraviolet-B + riboflavin exposure, 36% in UV-B exposed groups and minimum in control and riboflavin treated groups. Solar and UV-B radiations further have more harmful effect on Daphnia in presence of riboflavin and chloroquine thus showing their phototoxic effect. Exposure of UV-B radiation increase mortality rate and decreases the rate of reproduction in Daphnia magna. UV-B dose measured in Dehradun on clear sunny day was 0.380mw/cm2 in the month of January at 12.00 noon in natural solar radiation.
Keywords: Chloroquine, Daphnia magna, ozone depletion, phototoxicity, riboflavin, ultraviolet-B
|How to cite this article:|
Kumar S, Mishra P, Rawat BS. Phototoxicological studies of riboflavin and chloroquine on Daphnia magna. Toxicol Int 2008;15:137-41
| Introduction|| |
Ultraviolet radiation is the most photo chemically reactive wavelength of solar energy reaching the surface of the earth and has a broad range of effects on aquatic biogeochemistry, biota and ecosystem. Ultraviolet radiation is recognized as an important biological stressor for many species in aquatic ecosystem. (Williamson, 1996). Some phytoplankton species are UVR tolerant due to protective pigmentation and cell size and morphology (Cabrera et al., 1997). Ultraviolet radiation induced inhibition and enhancement of photosynthesis, chlorophyll content and primary productivity were studied (Day and Neale, 2002).
It has been recognized that the intensity of solar ultraviolet radiation (UV), especially of the short wavelengths of UV-B (280-325 nm) is increasing due to ozone depletion (Madronich, 1994). This was registered in terrestrial stations mainly in Antarctica and Arctic stations (Jokela et al., 1995). Life of aquatic environments experiences extreme conditions with respect to temperature, food availability and radiation, especially ultraviolet radiation due to long sunshine hours in summer. Additional stress may be added by an increase in solar UV radiation due to stratospheric ozone depletion. Aquatic organisms of shallow arctic water must reproduce successfully within a very short breeding season under these extreme environmental conditions. Some organisms are sensitive and unable to adapt these harsh conditions; one example is aquatic arthropod Daphnia (Hebert et al., 1990).
Daphnia occur circumpolar and play an important role in the aquatic food web. Therefore, the knowledge of the effect of solar ultraviolet radiation on Daphnia is of great interest. The effect of solar UV-B on some sensitive model species i.e. Tubifex and Pheretima has also been studied by Misra et al. (2002, 2005). Most of the irradiation experiments on Daphnia and other zooplankton have been conducted under standardized conditions in the laboratory using artificial light sources for irradiation (Siebeck and Bohm, 1994, Borgeraas and Hassen, 2000). However, some authors demonstrated that aquatic organisms of shallow habitats such as ponds, with high UV radiation doses or intensities, may be harmed, even killed due to natural irradiation (Williamson et al., 1994). There is a lack of information on phototoxicity of endogenous and exogenous chemicals present in our body and in environment. Riboflavin is vitamin B2 commonly present in our body and chloroquine is antimalarial drug.
This study was started with the objective to see the harmful effect of natural solar radiation and artificial ultraviolet-B with photosensitizers riboflavin and chloroquine, using mortality and reproduction as important parameters.
| Material and Methods|| |
All experiments were carried out in November to January. During the experiment water depth was about 6 cm and water transparency was very high. Transmission was measured with a Shimadzu Spectrophotometer. Daphnia magna species were collected from ponds of Dehradun 6 days before experimental setup. Daphnia magna were cultured by following the method of Songlake and Tisher (2001). We used a 200 mm mesh net to collect the Daphnia. Daphnia magna used in this experiment were active and of light cream/white in color.
Daphnia placed in Petri dish More Details with pond water. Twenty five adult Daphnia, egg carrying or egg carrying size were selected for each group. Daphnia were divided into nine groups. Group one was wrapped with aluminum foil and kept as dark control. Group two was exposed with riboflavin, group three was exposed with chloroquine, group four was exposed with solar radiation and group five was exposed with artificial UV-B radiation. Group six was exposed with solar radiation + riboflavin, group seven was exposed with solar radiation + chloroquine, group eight was exposed with UV-B radiation + riboflavin and group nine was exposed with UV-B radiation + chloroquine. Temperature was maintained between 15-20°C.
Natural solar radiation was given between 11A.M.-1 P.M. for one hour per day for 3 days during clear weather. Artificial ultraviolet-B was given by Philips UV-B lamp with average wavelength 312 nm. During the experiments, solar terrestrial UV-B was recorded at the research station Dehradun. UV-B dose was measured by Cole-Parmer radiometer USA; Vilber Laurmat corrected sensors spectral sensitivity UV-B: 280 - 320 nm, with maximum sensitivity 312 nm. UV-B dose in natural solar light measured at 12.00 noon was 0.380 mw/cm 2 in month of January. In experiment artificial UV-B lamp dose used was 1.85 mw/cm 2 . Riboflavin and chloroquine were collected from Merck India and dose used was 50 mg/litre.
The content was filtered and the number of live Daphnia, the number of egg carrying females and the number of juveniles alive were recorded. Physical appearance, movement and the color intensities of Daphnia were noted to get some measure of the condition of the animals. Results were statistically analyzed, standard error were calculated and inter group comparison were made using the Student's "t " test (Fisher, 1963).
| Results|| |
Results on mortality rate of Daphnia in presence of solar light and UV-B with riboflavin and chloroquine indicates that, riboflavin is not harmful when given separately but it become phototoxic in presence of solar light and UV-B both. Chloroquine is toxic in it and show more phototoxic effect in presence of solar radiation and UV-B. Its phototoxicity is more with UV-B radiation than solar radiation. Riboflavin is also phototoxic and has slight difference in toxicity in solar light and ultraviolet-B radiation [Table 3], [Figure 1]. Mortality rate in Daphnia was found highest i.e. 62% on 3rd day of UV-B exposure with chloroquine and 36% without chloroquine. Mortality rate was 49% with solar radiation + chloroquine, 39% in chloroquine treatment and 38% with UV-B and riboflavin coexposure [Table 1] and [Table 3]. Result also indicates that artificial UV-B has more toxicity than solar radiation [Table 3]. Studies on growth, reproduction and movement further support our results. UV-B radiation and chloroquine show maximum reduction in rate of reproduction and movement [Table 2]. Results also indicate that Daphnia is good model for evaluation of biological impact of enhanced UV radiation.
| Discussion|| |
The approach of the study was to examine the effect of solar radiation and UV-B on Daphnia with endogenous and exogenous photo-sensitizers i.e. riboflavin and chloroquine. Therefore, Daphnia magna were exposed in the laboratory with natural solarlight and artificial UV-B. Low UV-B exposure dose resulted in low mortality survival in all treatments. This demonstrates that Daphnia survived well under the experimental conditions. This is in agreement with Hessen (1996), who reported no effect on survival in Daphnia pulicaria exposed to UV-B in a deep pond for several days in poor weather condition. [Table 1] and [Table 3] showed considerable variation in survival rates in presence of photosensitizers and ultraviolet radiation suggesting the photo reactivity of riboflavin and chloroquine. High doses cause greater stress to Daphnia as compared to lower UV-B dose. Nutritive status of Daphnia has a strong impact on the UV- tolerance (Zellmer 1996, DeLange and Van Donk 1997, Lurling and Van Donk 1997) However, all containers contained algae from the surrounding waters with similar degree of damage.
Riboflavin and chloroquine are important chromophores for photoinduced lethality in Daphnia. Phototoxicity of riboflavin and chloroquine due to irradiation of solar light and UV-B is attributable to generation of reactive oxygen species and hydrogenperoxide radicals (Sato et al., 1995). UV-B effects on zooplankton were reported in even greater depths. In Northern temperate lake, Williamson and coworkers (1994) reported difference in survival of Daphnia at different depth. They found distinct differences in UV-B effects in correlation with water transparency. Reproduction has proved to be a sensitive measure for radiation damage in Daphnia (Zellmer, 1996). The comparison of the number of offspring exposed to different radiation regimes must be viewed with caution since the number of eggs per egg carrying female could not be registered at the start of the experiments.
Limitation of the experiment was movement and reproduction can not be measured absolutely and statistically. As a consequence, results of the experiments cannot be compared in an absolute way. Reduction in reproduction after irradiation with artificial UV-B has been reported for marine zooplankton (Damkaer et at., 1980). From these experiments it can be concluded that Daphnia of shallow water such as ponds and small lakes may experience critical levels of solar and UV-B exposure unless their habitat provides shelter from radiation in form of vegetation and rocks. It was demonstrated that not only UV-B, but also solar light can cause severe damage to aquatic fauna. Reproductive parameters seem to be very sensitive in determining UV damage; therefore, further increases in solar UV may lead to significant changes in the zooplankton communities. Further field investigations on reproductive success under natural radiation conditions are necessary to gain a better understanding of the effect of solar UV radiation.
| Acknowledgements|| |
Authors are thankful to Uttarakhand State Council for Science and Technology, Dehradun for providing financial support No. UCST/R&D/LS37/06-07/1175.
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[Table 3], [Table 1], [Table 2]