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High-Speed Tracking of Ascidian Spermatozoa


We have utilized our microorganism tracking system to assess chemotaxis of ascidian spermatozoa, collaborating with Prof. Yoshida in Misaki Marine Biological Station, University of Tokyo.

The new system is capable of tracking fast-moving, small objects under extreme conditions by using high-speed visual feedback for assessing sperm chemotaxis. The system shows remarkable performance and versatility, good enough for practical use in biology. Spermatozoa are tracked under severe conditions of ultra-high speed, diffraction-limit size, and the low contrast targets.

Experimental results showed that we successfully achieved continuous stable tracking of swimming ascidian spermatozoa with quality sufficient for assessing sperm motility, indicating the feasibility of our system to tracking almost any type of cell.

System configuration. Cropped image sequence of a swimming sperm.


Measured chemotactic motion

A result of measured chemotactic motion is shown as an integrated video of the target image and its trajectory. An agar including the ascidian spermatozoa's chemoattractant was infused in the chamber so that it would make the density distribution. The image of the swimming sperm attracted to the source of the chemoattractant and it's trajectory were synthesized into one video by using the computer graphics technique.


  1. Hiromasa Oku, Naoko Ogawa, Kogiku Shiba, Manabu Yoshida, and Masatoshi Ishikawa : How to Track Spermatozoa using High-Speed Visual Feedback, 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC 2008) (Vancouver, 2008.8.21) / Proceedings, pp.125-128 [PDF (1.5M)] *IEEE(Oral Session)
  2. Naoko Ogawa, Takahiko Ishikawa, Hiromasa Oku, Kogiku Shiba, Manabu Yoshida and Masatoshi Ishikawa. Tracking of ascidian spermatozoa using high-speed visual feedback. 2007 JSME Conference on Robotics and Mechatronics (Robomec 2007) (Akita, Japan, 12 May 2007) / Proceedings, 2A2-O05, May 2007. [PDF (998K)] (in Japanese)

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