ZEBRAFISH EMBRYO TOLERANCE TO ENVIRONMENTAL STRESS FACTORS-CONCENTRATION-DOSE RESPONSE ANALYSIS OF OXYGEN LIMITATION, PH, AND UV-LIGHT IRRADIATION

During the last century the increase in the mean global temperatures has been shown to impact on freshwater physicochemical parameters such as pH, dissolved oxygen, or ultraviolet (UV) light abundance. Changes in these parameters could modify the toxicity of environmental pollutants. Therefore, in the present study, the authors studied the tolerance (survival and sublethal endpoints) of zebrafish (Danio rerio) embryos to variations in pH (3-12), dissolved oxygen (3.9-237 mu mol/L) and UV intensity (55-467 mW/m(2)) using selected endpoints. Sublethal endpoint assessment included the quantification of hatching success, developmental delay, reduction of body length, frequency of edema, and morphological abnormalities. Median lethal concentrations (LC50s; 96-h) of 3.68 and 10.21 were determined for acid and alkaline pH, respectively. Embryo survival appeared to be relatively resistant to oxygen depletion with a 96-h LC50 of 0.42 mg/L. However, concentrations of 6 mg/L and below caused edema and developmental retardations. Continuous exposure to UV radiation affected zebrafish development by reducing survival and hatching rate and triggering a series of developmental abnormalities such as pericardial edema and deformities. A72-h LC50 of 227 mW/m(2) was derived from intensity-response modeling. By generation of concentration-response parameters the authors' data provide a basis for the subsequent assessment of combined effect of environmental stress parameters and chemicals. (C) 2016 SETAC