Autotomy reflex in a freshwater oligochaete, Lumbriculus variegatus (Clitellata: Lumbriculidae)

Abstract

A novel apparatus was developed that induced segmental autotomy in the freshwater oligochaete, Lumbriculus variegatus. The apparatus delivered a quantifiable amount of focal compression to the dorsal body surface at a selected site along the worm. This resulted in a rapid and stereotyped autotomy sequence, beginning with formation of a lateral fissure in the body just anterior to the compression site. Formation of the fissure usually occurred 100– 200 ms after the onset of compression. Autotomy readily occurred in the absence of significant longitudinal tension at the autotomy site and in the absence of direct laceration of the body wall. Autotomy culminated in a complete, transverse separation and sealing of anterior and posterior body fragments with no apparent blood loss from either end. There was a direct relationship between the amount of compression and the probability of autotomy in both midbody and tail regions. However, there was a consistently greater probability of autotomy in tail versus midbody regions. Autotomy did not occur if the duration of compression was less than 77 ms. Autotomy responses were suppressed in dose-dependent manner by a 15 min treatment with nicotine prior to compression. In instances where compression just failed to induce autotomy there was no evidence of disruption of impulse conduction in giant nerve fibers. Rapid and clear-cut autotomy, in combination with this worm’s significant capacity for regeneration of lost segments, are adaptively significant strategies for surviving predatory attack.

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