Now showing items 1-3 of 3

    • Article

      Effects of long-term exposure to a mixture of cadmium, zinc, and inorganic mercury on two strains of tilapia Oreochromis niloticus (L.) 

      MLA Cuvin-Aralar & EV Aralar - Bulletin of Environmental Contamination and Toxicology, 1993 - Springer Verlag
      Tilapia are an economically important group of fish. They have a short generation period of 3-6 months, and exhibit successive breeding. In addition, their fast growth, herbivorous or omnivorous feeding habits, high food conversion efficiency, ease of spawning, ease of handling, resistance to disease and good consumer acceptance make this group of fish highly popular in aquaculture in Asia, Africa and other developing countries. Tilapia have been the subject of research on pollution effects over the last decade. The purpose of this study was to determine growth, accumulation and depuration responses of 2 strains of the Nile tilapia, Oreochromis niloticus, chronically exposed to a mixture of heavy metals including cadmium, zinc and mercury.
    • Article

      Resistance to a heavy metal mixture in Oreochromis niloticus progenies from parents chronically exposed to the same metals 

      MLA Cuvin-Aralar & EV Aralar - Chemosphere, 1995 - Elsevier
      Adult Oreochromis niloticus were mass spawned in concrete tanks. The one-month old progenies (F1) were exposed for two months to a mixture of 0.01 mg L−1 Hg, 0.1 mg L−1 Cd and 1.0 mg L−1 Zn. The survivors were grown to sexual maturity in a natural environment (lake). The fish were spawned and the progenies (F2) of the exposed F1 (EF1) were exposed to another mixture of the three metals: 3.0 mg L−1 Zn, 0.30 mg L−1 Cd and 0.01 mg L−1 Hg, both in a static and static-renewal system. Another group of F2 from unexposed F1 (UF1) received the same treatment. Results showed that in both exposure systems, survival of the F2 of EF1 was significantly higher (P<0.05) than those from UF1. The medial lethal time (LT50) of the F2's were estimated from the time-response curve following regression analysis: 5.16 days (F2 of UF1) and 9.03 days (F2 of EF1) in the static exposure experiment; 3.34 days (F2 of UF1) and 5.52 days (F2 of EF1) in the static-renewal run. Exposure of the parental stock resulted in the culling out of individuals which were more susceptible to the heavy metals. The more resistant members of the population (survivors) which have the ability to adapt to the toxicants were able to pass on the resistance to their offspring. The results are supported by other studies in the field which demonstrate high resistance in populations of organisms living in contaminated sites.
    • Article

      Survival and heavy metal accumulation of two Oreochromis niloticus (L.) strains exposed to mixtures of zinc, cadmium and mercury 

      MLA Cuvin-Aralar - Science of the Total Environment, 1994 - Elsevier
      Two Nile tilapia strains of Oreochromis niloticus (L.) (Cichlidae, Teleostei) fingerlings were exposed to mixtures of zinc, cadmium and mercury. The two strains used were Chitralada or NIFI (originally from the National Inland Fisheries Institute, Thailand) and CLSU (from the Freshwater Aquaculture Center of the Central Luzon State University, The Philippines). Short-term (10 days) exposure to a metal mixture of 5 mg 1−1 zinc (Zn), 0.5 mg 1−1 cadmium (Cd) and 0.02 mg l−1 mercury (Hg) gave significantly higher survival percentage in the NIFI strain compared with the CLSU strain. Similar exposure conditions using larger and older fingerlings of the two strains also showed a slightly higher survival percentage in the NIFI strain but the difference was not significant. Prolonged exposure of the fingerlings to a lower concentration of the metal mixture (1.0 mg l−1 Zn, 0.1 mg l−1 Cd, 0.01 mg l−1 Hg) also resulted in similar survival percentages between the two strains at the end of the 60 days run. Whole body accumulation of Zn was significantly higher in CLSU than in NIFI after 14-day exposure to the low concentration metal mixture. There was no significant difference in the accumulation of Cd and Hg between the two strains. Of the three metals, Hg had the highest bioaccumulation factor (BF) which was ∼900–1000, followed by Cd with 255–280 and Zn with 180–195 times the nominal concentration in the water. Concentration of Cd and Hg in fish tissues increased with exposure period while the concentration of Zn was maintained in NIFI and decreased in CLSU between the 6th and 14th day of exposure, suggesting that Zn (an essential element) accumulation maybe regulated by both strains.