Regulation of body volume by the peripheral nervous system of the terrestrial slug Ariolimax columbianus

Abstract

AbstractResponses to mechanical and chemical stimulation have been studied in an in vitro preparation of the body wall of the land slug Ariolimax columbianus. This preparation (posterior chamber, PC) is separated from the head ganglia and therefore has only peripheral nervous control. The volume contained within the PC (normally filled with viscera and hemolymph) is determined by 1) contraction or relaxation of muscle cells, causing exchange of fluid between the PC and the attached manometer that controls pressure within the PC; 2) secretion by epithelial channel cells moving fluid from inside the PC to the outside across the epithelial surface.The PC maintained at constant internal pressure responded to mechanical stimulation (at ca. 1 Hz) of the epithelium with a brief burst of secretion. Prolonged (45 minutes) stretch of the body wall by maintenance at 11 torr or above resulted in intermittent pulses of secretion and muscle contraction. At very high pressure muscle contraction was suppressed, and secretion volumes were huge, gradually restoring the volume of the PC to its initial value (autoregulation).When PCs were immersed in fluid containing garlic extract, skin receptors responded, initiating secretion comparable to the effects of mechanical stimulation in both amount and duration. Other chemicals (including capsaicine, cysteic acid, and geraniol) known to be aversive to pulmonates in vivo did not activate the secretory response.