LIMULUS RECEPTOR ACTION SPECTRA

An early report of the existence of two classes of ommatidial cells in the lateral eye of Limulus with different action spectra has been confirmed and observations have been extended into the near ultraviolet region of the spectrum. Responses of single receptor cells have been measured as a function of wavelength and energy; equal response action spectra have been constructed from these data. Two types of cells have been found. Alpha cells: These cells have an action spectrum which agrees well with the density spectrum of rhodopsin. The most sensitive wavelength is around 525 nm. Beta cells: The action spectrum of these cells does not resemble a photopigment spectrum; beta cells are sensitive to a band of wavelengths from 350 to 550 nm. No convincing evidence of spectrally selective bleaching was found in the beta cells. © 1969.