著者

甕 紘介 中島 翔 菊池 俊紀 藤江 裕道

出版者

一般社団法人日本機械学会

雑誌

年次大会講演論文集

巻号頁・発行日

vol.2004, pp.143-144, 2004

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The frictional characteristics of earthworms were determined using a 3D micro force plate developed in our laboratory. It was possible to measure the frictional force and vertical force applied to the force plate. Earthworms, named "Eisenia fetida" and "Pheretima hupeiensis" in Japanese, were used to determine their frictional behaviors when they moved on waterproof sand papers fixed to the force plate. The coefficient of static friction of Eisenia fetida against the sand papers were 6.9, 5.7, and 3.9, at the roughness of 2.98, 3.73, and 16.2 μm, respectively, with a significant difference (p<0.05) observed between the roughness of 2.98 and 16.2 μm. The coefficient of friction of Pheretima hupeiensis against the sand papers indicated a smilar trend as to Eisenia fetida, with a significant difference observed between the roughness of 2.98 and 16.2 μm. Note that the coefficient was significantly higher in Pheretima hupeiensis than in Eisenia fetida at the roughness of 2.98 μm. Mucous liquid secreted from earthworms was observed on the surface of the roughness of 2.98 and 3.73 μm after the friction test. Microscopic observation indicated that earthworms had many spikes called "seta" around their bodies and that they controlled the length of the seta during the movement on an irregular surface. These results indicate that earthworms control their frictional behavior in response to various surfaces that they contact by the use of their mucous liquid and seta They also indicate that the mucous liquid plays more important role than the seta in controlling the frictional behavior of earthworms in response to relatively smooth surfaces.