Background and purpose: Locomotory behavior (motility) is a vital importance in animals. We examined the effects of ionizing radiation (IR) on locomotory behavior using Caenorhabditis elegans. We reported an IR-induced reduction of locomotory rate in the absence of food[1],[2]. In the previous experiments, wild-type animals were irradiated with g-rays in the whole body, and measured the motility using "body bends" (the number of bends in the anterior body region at 20-s intervals)[3]. However, the IR-induced effects in the central and posterior body region were not evaluated by the body bends. In the present study, to investigate the IR-induced effects in more detail, we try to evaluate the motility of the whole body by using the video-based analysis. Strains and culture: The C. elegans wild-type Bristol N2[4] and the Escherichia coli HB101 strain, were obtained from the Caenorhabditis Genetics Center. Using standard methods[4], animals were grown at 20 deg C on 6-cm plates containing nematode growth medium (NGM) agar spread with E. coli. Well-fed adults were used in all experiments. Irradiation and video-based analysis: Animals were collected from culture plates and washed, and transferred to the 3.5-cm NGM plate without a bacterial lawn. The movements of animals were video-recorded for 1 min. Subsequently, animals were collected and placed on a plate with a bacterial lawn for 1h to avoid starvation, and irradiated with graded doses (< 1 kGy) of 60Co g-rays. Immediately after irradiation, animals were again transferred to the 3.5-cm NGM plate without a bacterial lawn, and the movements were video-recorded. To measure the whole-body motility, we are now constructing a worm-tracking system based on "the parallel worm tracker"[5]. Using this system, we analyze the trajectories and bends at several points of the body in multiple animals before and after irradiation. Results and conclusion: We propose a novel standard by using the video-based analysis for evaluation of IR-induced effects on motility in C. elegans. In the presentation, we will show preliminary results of the analyses, and would like to discuss about the effectiveness of the analysis for evaluation of IR-induced effects. References: [1] Sakashita, T., et al. (2008) J. Radiat. Res. 49: 285-291. [2] Suzuki, M., et al. (2009) J. Radiat. Res. 50 (in press). [3] Sawin, E.R., et al. (2000) Neuron 26: 619-631. [4] Brenner, S. (1974) Genetics 77: 71-94. [5] Ramot, D., et al. (2008) PLoS ONE,3: 5:
e2208.