title: The morphology of the horseshoe crab (Limulus polyphemus) visual system. VII. Innervation of photoreceptor neurons by neurosecretory efferents.
abstract: Efferent fibers to the compound eye of the horseshoe crab, Limulus polyphemus, not only innervate the various pigment cells, but also invade the eccentric cell dendrite and the retinula cells. This finding provides a structural basis for the coupling of circadian rhythm between the efferents and the receptor cells.
mesh_terms: D000818:Animals; D006737:Horseshoe Crabs / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009476:Neurons, Efferent / Q000648:ultrastructure; D009490:Neurosecretory Systems / Q000648:ultrastructure; D010786:Photoreceptor Cells / Q000648:ultrastructure*; D013569:Synapses / Q000648:ultrastructure