Lethal and sub-lethal effects on the Asian common toad Duttaphrynus melanostictus from exposure to hexavalent chromium.
Chromium discharged in industrial effluents frequently occurs as an environmental pollutant, but the lethal and sub-lethal effects the heavy metal might cause in animals exposed to it have been insufficiently investigated. Selecting the amphibian Duttaphrynus melanostictus, we carried out laboratory tests to investigate the effects of short and long term exposure to hexavalent chromium (Cr(VI)) in both tadpoles and adult toads. The concentrations used were 0.002, 0.02, 0.2, 1.0 and 2.0mg/L, the first three corresponding to field levels. In vitro exposures were also carried out using toad erythrocytes and Cr(VI) concentrations of 0.0015, 0.003, 0.015, 0.03, 0.15mg/L. Mortality, growth retardation, developmental delays and structural aberrations were noted in the metal-treated tadpoles, with increasing incidence corresponding to increase in Cr(VI) level and duration of exposure. Many of the sub-lethal effects were evident with long term exposure to environmentally relevant levels of the toxicant. Changes in selected blood parameters and erythrocyte morphometry were also detected in Cr(VI) exposed toads, indicating anaemic and leucopenic conditions. In the genotoxicity study, DNA damage indicated by comet assay and increased micronuclei frequency, occurred at the low Cr(VI) concentrations tested. The multiple deleterious effects of exposure to chromium signal the need for monitoring and controlling the discharge of chromium to the environment. The dose-dependency and genotoxic effects observed in this widely distributed Asian toad indicates its suitability for monitoring heavy metal pollution in aquatic systems.
Department of Zoology and Environment Sciences, University of Colombo, Colombo 03, Sri Lanka. Electronic address: vink1025@gmail.com.
Vindhya A K
VA
Fernando
Institute of Biochemistry, Molecular Biology and Biotechnology, University of Colombo, Colombo 03, Sri Lanka. Electronic address: jagath@ibmbb.cmb.ac.lk.
Jagathpriya
J
Weerasena
Department of Statistics, University of Colombo, Colombo 03, Sri Lanka. Electronic address: pemantha@stat.cmb.ac.lk.
G Pemantha
GP
Lakraj
Department of Zoology and Environment Sciences, University of Colombo, Colombo 03, Sri Lanka. Electronic address: icperera@sci.cmb.ac.lk.
Inoka C
IC
Perera
Department of Zoology and Environment Sciences, University of Colombo, Colombo 03, Sri Lanka. Electronic address: cddangalle@gmail.com.
Chandima D
CD
Dangalle
Institute of Biochemistry, Molecular Biology and Biotechnology, University of Colombo, Colombo 03, Sri Lanka. Electronic address: shiromah@gmail.com.
Shiroma
S
Handunnetti
Department of Zoology and Environment Sciences, University of Colombo, Colombo 03, Sri Lanka. Electronic address: suviprema@gmail.com.
Sunil
S
Premawansa
Department of Zoology and Environment Sciences, University of Colombo, Colombo 03, Sri Lanka. Electronic address: mayuri@sci.cmb.ac.lk.
Mayuri R
MR
Wijesinghe
D000818:Animals; D002025:Bufonidae / Q000502:physiology; D002857:Chromium / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000187:drug effects; D007814:Larva / Q000187:drug effects; D018675:Toxicity Tests; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion
Chromium; Genotoxicity; Growth; Haematology; Tadpoles; Toxicity