The effects of endosulfan and variable water temperature on survivorship and subsequent vulnerability to predation in Litoria citropa tadpoles

The effects of short-term exposure of stage 25 Litoria citropa tadpoles to sublethal concentrations of endosulfan in combination with either a stable or a variable temperature cycle (20 +/- 2 vs. 21 +/- 7.5 degreesC) were investigated. Both exposure to 0.8 mug/l endosulfan and the wider temperature range over 96 h had significant adverse effects on survivorship. In addition, variable water temperatures at the time of endosulfan exposure increased tadpoles' vulnerability to predation by odonates 24 days later, but only if they had also been exposed to endosulfan. This effect occurred despite maintenance of all tadpoles at 19 +/- 1 degreesC during the intervening 24 days. Correlates of fitness such as this represent a move towards more biologically relevant experimental endpoints. This is an important step if we are to gain an understanding of how exposure to agricultural chemicals may affect frog populations in the natural environment. The results indicate that a short, pulsed exposure to a sublethal concentration of endosulfan and extremes in temperature may then have long-term impacts on fitness. (C) 2002 Elsevier Science B.V. All rights reserved.