The pars tuberalis of the pituitary: a gateway for neuroendocrine output

The circalunidian hypothesis that tidal rhythms in coastal animals are controlled by two lunar-day (c.24.8 h) oscillators coupled in antiphase is challenged. Rhythmic locomotor activity patterns of the shore crab Carcinus maenas, and probably of some other species too, are more economically explained by interacting circadian (c.24 h) and true circatidal (c.12.4 h) physiological oscillators. A testable hypothesis is proposed that combines a circadian promotor and a circatidal inhibitor of locomotor activity.