Summary
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1.
Under very weak illumination, photoreceptors of the darkadapted locust compound eye produce large (in the range 0.5 to 10 mV) discrete depolarising potentials called bumps.
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2.
By eliminating all sources of stray light it was shown that spontaneous bumps are very rare (less than 10 per h).
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3.
Statistical analysis of the occurrence of bumps following brief flashes of light and during continuous light exposure shows that an absorbed photon triggers the production of only one bump with a probability greater than 0.59+-0.19 (S.D.).
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4.
As a consequence of the extremely low rate of spontaneous activity and the invariability of the number of bumps elicited by an effectively captured photon, two potential sources of transducer noise in the photoreceptor are minimized.
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I thank Drs. S.R. Shaw and S.B. Laughlin and Professors G.A. Horridge and W.R. Levick for useful discussions.
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Lillywhite, P.G. Single photon signals and transduction in an insect eye. J. Comp. Physiol. 122, 189–200 (1977). https://doi.org/10.1007/BF00611889
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DOI: https://doi.org/10.1007/BF00611889