Lead (Pb) is a major heavy metal that augments environmental pollution and is a health risk to living organisms. This study was performed to investigate the effect of lead on characteristics of planarian, Dugesia japonica. Briefly, planarians were cultivated in water containing different concentrations (0–400 mg/L) of Pb, and incubated for varying durations (1, 3, and 5 hr). After termination of the incubation time, motility and seizure-like behaviors (c-like, head-bop, snake-like, and screw-like) of the planarians were counted in fresh water. Results showed that increasing Pb concentration and time resulted in decreased motility of the planarians (p<0.05). Increasing concentrations of Pb also resulted in significant increase in the seizure-like behavioral patterns, in particular the c-like and head-bop behaviors. In order to examine eye regeneration, the head region was cut, and rest of the body was incubated in water in the absence or presence of Pb, until emergence of the eye extrusion. Formation of eye spots was initiated in amputated fragments of the control group (without Pb) on day 4 after incubation, whereas appearance of the eye spots was delayed in planarian exposed to 200 mg/L Pb. Moreover, immunohistochemistry revealed that formation of the optic nerve was delayed in planarians exposed to Pb. Thus, our studies determined that planarians exposed to high concentrations of Pb resulted in decreasing motility and induction of seizure-like behaviors, as well as delayed eye regeneration. Results of the current study therefore validate that exposure to lead has a negative effect on the lifespan of aquatic organisms and can cause disturbance of the nervous system in animals, thereby implying the possibility of threatening health.

Introduction
Materials and Methods
    Experimental animals and reagents
    Evaluation of motility and seizure-like behaviorpatterns
    Observation of eye formation
    Whole-mount immunohistochemistry
    Statistical analysis
Results
    Atypical motility observed in planarians exposed toPb
    Delayed eye regeneration after exposure to Pb
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)
• Ram Prasad Aganja(Division of Biotechnology, College of Environmental & Bioresource Sciences, Jeonbuk 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