Journal of Environmental Biology

Life table demography of Ceriodaphnia dubia (Cladocera) exposed to

copper at different levels and periods

­Jose Luis Gama-Flores¹, Maria Elena Castellanos-Paez¹, S.S.S. Sarma*², S. Nandini²

*sarma@servidor.unam.mx

¹Doctoral Programme, Autonomous Metropolitan University, Unidad Xochimilco, Calzada de Hueso, No. 1100,

Villa de Quietud,  Mexico City, Postal code- 04960, Mexico

²Laboratory of Aquatic Zoology, Division of Research and Postgraduate Studies, National Autonomous University of Mexico,

Campus Iztacala, Av. de los Barrios No.1, AP 314, , Los Reyes, Tlalnepantla, State of Mexico,Postal code- 54090, Mexico

(Received: August 19, 2006 ; Revised received: November 12, 2006 ; Accepted: January 15, 2007)

Abstract: We studied the demographic responses of Ceriodaphnia dubia exposed to copper at 3 different levels (0.1, 0.2 and 0.4 mg l^-1) and at 4 exposure periods (3, 6, 12 and 24 hr) in addition to controls (without the heavy metal). The tested levels of Cu concentration and the chosen periods of exposure affected some demographic variables (average lifespan, gross and net reproductive rates and generation time). Depending on the heavy metal concentration and the period of exposure, the average lifespan of C. dubia varied from 18 to 24 day. Net reproductive rates (NRR) ranged from 50 to 80 offspring per female per lifespan, while the rate of population increase (r) varied from 0.30 to 0.34 per day. Though gross reproductive rates (especially at low and intermediate copper levels and shorter duration of exposure) showed significantly higher values than controls, both NRR and r were either unaffected or decreased. It is therefore necessary to regulate the release of untreated industrial effluents containing copper into freshwater ecosystems. Our study thus highlights the importance of including, not only toxicant concentrations but also exposure time, in ecotoxicological evaluations.

Key words:   Cladocera, Heavy metal, Zooplankton, Demography

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