Hormonal modulation of circadian neural activity in Carcinus maenas (L.)

Carcinus maenas is shown to exhibit circadian variations of (i) responsiveness to light in retinal photoreceptors and visual interneurons, (ii) reflex responses of optomotor neurons to mechanoreceptive stimulation and (iii) spontaneous activity of neurons detecting movements of the body. In each case reactivity is high at ‘expected’ night and low during ‘expected’ day. Day-phase characteristics are reproduced by injected extract of nervous tissue, particularly of the eyestalk, the active substance in which appears to be peptidic.