Indirect nervous control of luminescence in the polynoid worm Harmothoe lunulata

Abstract

Abstract Light responses were recorded in vitro from isolated elytra of Harmothoë lunulata following field or intraganglionic stimulation. Similar responses were evoked through bath application or microinjection of acetylcholine (ACh) at the level of the ganglion. Antimuscarinic but not antinicotinic inhibitors reversibly blocked these responses. In these conditions, when the nervous system is blocked, the preparation no longer respond to K + ions depolarization nor to electrical field stimulation (depolarizing or hyperpolarizing currents). These new data strongly suggest that a cholinergic nervous system controls light production through muscarinic receptors which are not localized at the level of the photocyte and definitively rules out the possibility that propagation of the stimulus involves epithelial conduction. We propose that the activation occurs through relaying structures different from the epithelium. Calcium may be involved in the transmission process since inhibitors of its movements also block light response.