title: Changes during the moult cycle in the bursting firing pattern of the electrical activity recorded extracellularly from the sinus gland of the terrestrial isopod, Oniscus asellus.
abstract: Ongoing electrical activity of the sinus gland (SG) of the terrestrial isopod, Oniscus asellus, was recorded extracellularly from almost intact breeding or non-breeding females to delineate the major times of neurohormone release during the moult cycle. In intermoult, SGs discharged in long bursts (10-50 s) at high frequency (10-45 Hz), and their activity ratios (total burst duration divided by total time the SG was monitored) ranged from 0.22 to 0.73. At premoult initiation when release of moult-inhibiting hormone is expected to decline, a decrease in SG activity occurred. It rose again in early premoult in parallel with increases in ecdysteroid titre; declined again in late premoult during peak ecdysteroid titres; increased again just prior to posterior ecdysis, and was very low during posterior ecdysis itself. Activity increased immediately after posterior and anterior ecdysis suggesting the release of neurohormones involved in calcification of the new cuticle. Burst duration was ca. two-fold longer in breeding compared to non-breeding females during early premoult suggesting the release of neurohormones involved in vitellogenesis, and before anterior ecdysis suggesting release of neurohormones involved in egg deposition. Thus, the release of neurohormones occurred during 4 major periods in each moult cycle, clearly demonstrating a relationship between SG activity in situ, and the physiological events dependent on SG hormones.
mesh_terms: D000818:Animals; D003445:Crustacea / Q000502:physiology*; D004440:Ecdysone / Q000502:physiology; D004594:Electrophysiology; D005260:Female; D009489:Neurosecretion; D009490:Neurosecretory Systems / Q000502:physiology*
chemical_list: D004440:Ecdysone