This study was undertaken to evaluate the toxic effect of cadmium sulfate (Cds) on planarians (Dugesia japonica), and the suitability of planarians as an alternative animal model for toxicity studies. Planarians were exposed to varying concentrations of experimental solutions containing 0.1–25 mg/L Cds, and incubated for 1, 3, and 5 hrs. Motility, seizure-like behaviors (c-like, head-bop, snake-like, and screw-like) and regeneration ability of the amputated fragment were subsequently evaluated. Results showed decreased motility with increasing concentrations of Cds (p<0.05), with the lowest motility being observed at the highest concentration of 25 mg/L Cds. Results also indicate that seizure-like behavior patterns were significantly affected by increments in the Cds concentrations, especially the c-like and head-bop behaviors were notably increased. Compared to the control, the regeneration ability of the planarians was decreased in the experimental solutions containing Cds. Planarians exposed to Cds showed either delayed eye formation or no eye regeneration during incubation. Moreover, increased concentrations of Cds resulted in failure to regenerate and death of the planarians. In conclusion, this study confirm that the heavy metal Cds exerts a toxic effect on planarians. Furthermore, the performances of the planarians in the experimental period exhibit their suitability as an alternative animal model for toxicity studies.

Introduction
Materials and Methods
    Experimental animals and reagents
    Examination of motility and seizure-like behaviors
    Observation of regeneration pattern
    Whole-mount immunohistochemistry
    Statistical analysis
Results
    Aberrant motility was observed in planarian exposedto Cds
    Eye formation of planarians in the presence of Cds
Discussion
References

• Yong-Jin Kim(Division of Biotechnology, College of Environmental & Bioresource Sciences, Jeonbuk National University)
• Yeon-Hwa Kim(Laboratory of Veterinary Virology, College of Veterinary Medicine, Chungbuk National University)
• A. A. Dilki Indrachapa Adikari(Department of Agricultural Education, College of Education, Sunchon National University)
• Juneno So(Department of Pharmaceutical Engineering, Woosuk University)
• Young-Joo Yi(Department of Agricultural Education, College of Education, Sunchon National University) Corresponding author
• Sang-Myeong Lee(Laboratory of Veterinary Virology, College of Veterinary Medicine, Chungbuk National University) Corresponding author