Purification and Partial Characterization of an Autotomy-Promoting Factor from the Sea Star Pycnopodia helianthoides

¹ Department of Biology, Mount Allison University, Sackville, New Brunswick, Canada E0A 3C0
² Department of Biology, University of Victoria, Victoria, British Columbia, Canada V8W 2Y2

Echinoderms possess collagenous connective tissues that are capable of rapid, nervously mediated changes in their tensile strength. Arm autotomy in sea stars is facilitated by a rapid decrease in the tensile strength of connective tissues in the arm base. In this study, an autotomy-promoting factor (APF) has been isolated from the fluids released by scalded or autotomizing sea stars (Pycnopodia helianthoides). When injected into the coleom, APF elicits a complex behavioral response that culminates within minutes in multiple arm autotomy and a generalized softening of the body wall. Injection of fluid from intact, untreated sea stars does not promote the autotomy response. APF is a water soluble, heat-labile substance derived from the body wall. It is ammonium sulphate precipitable and its activity is reduced or destroyed by several proteolytic enzymes. On the basis of its gel permeation elution pattern, APF has M_r of about 1200 Daltons. APF can be purified to a single peak of activity by reversed-phase HPLC. We conclude the substance is a peptide or has a peptide component.

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