Meeting Abstract
Leeches use circular attachment organs to anchor themselves to substrates and prey. Several adhesive mechanisms, including suction and wet adhesion, could contribute to the total attachment force. A force plate incorporating a pressure transducer was used to simultaneously measure attachment force and pressure under the posterior attachment organs of medicinal leeches (Hirudo verbana). The maximum measured attachment force was 0.21 N, approximately 20 times the leech body weight. Pressures up to 27 kPa below ambient were generated during attachment. On a perforated substrate where a pressure differential could not be formed, the attachment force was 0.0085 ± 0.003 N (mean ± SD), 4.0 % of the maximum during suction. This indicates that suction is the primary mechanism for temporary attachment to a substrate during feeding or locomotion. Leeches also anchor to substrates in the longer term, potentially for days or weeks. Long term attachments are accompanied by the secretion of thick mucus at the attachment point. In the presence of a methyl cellulose solution with a viscosity approximating that of mucus, a mean attachment force of 0.055 ± 0.012 N (mean ± SD), or 26 % of the suction maximum, was generated in the absence of suction. Mucus secretion therefore allows for long term anchorage without the need to generate suction pressures with energetically costly muscle contractions.
