Vol. 42 No. 1, 2003

Copper or Cadmium Pretreatment Increases the Protection against Cadmium Toxicity in Tilapia Larvae (Oreochromis mossambicus)

Su-Mei Wu^1,* and Pung-Pung Hwang²

¹Department of Aquatic Biosciences, National Chiayi University, Chiayi, Taiwan 600
²Institute of Zoology, Academia Sinica, Nankang, Taipei, Taiwan 115

Su-Mei Wu and Pung-Pung Hwang (2003) The purpose of this study was to examine the role of metallothionein (MT) in the acclimation mechanisms in tilapia larvae to environments containing heavy metals. Waterborne Cu²⁺ stimulated MT expression in newly hatched tilapia larvae in dose- and time-dependent patterns. Tilapia larvae, exposed to 35 µg/l CdCl² or 100 µg/l CuSO4 or normal fresh water for 72 h, respectively, were subsequently transferred to 100 µg/l Cd²⁺ for an additional 48 h. At the end of experiment, whole-body contents of Cd²⁺, Na²⁺, Ca²⁺ and MT, as well as mortality in the larvae were examined. The present data indicate that: (1) Cd²⁺- or Cu²⁺-pretreated larvae survived much better than did larvae with no pretreatment after the final exposure to 100 µg/l Cd²⁺; and (2) both pretreatment groups synthesized about 1.8- and 1.6-fold, respectively, more MT than did larvae with no pretreatment. These results suggest the involvement of MT in heavy-metal detoxification in developing tilapia.

Key words: Metallothionein, Fish larvae, Cd²⁺, Cu²⁺, Ca²⁺.

*Correspondence: Tel: 886-5-2754081. Fax: 886-5-2717847. E-mail: sumei@mail.ncyu.edu.tw