| The gonad of the snail Helix aspersa is innervated by a branch of the intestinal nerve. Here it is demonstrated that nerve stimulation causes peristaltic contractions and the acceleration of cilia beating in the proximal part of the hermaphroditic duct. Acetylcholine and serotonin induced peristaltic contractions when applied without nerve stimulation. As well, serotonin induced the acceleration of cilia beating. The neuropeptide FMRFamide caused dilation of the hermaphroditic duct. Pharmacological blocking of acetylcholine and serotonin receptors with concurrent nerve stimulation induced a dilation similar to that caused by FMRFamide application. It is suggested that all three transmitters are released from intestinal nerve terminals to facilitate oocyte transport during ovulation. Nerve stimulation induced an increase in gamete transport rates. Because several candidate chemical messengers failed to induce ovulation when injected into the circulatory system, Helix aspersa appears to initiate ovulation differently from related species. Whereas Aplysia and Lymnaea use hormones, Helix apparently signals ovulation via the intestinal nerve. |
