. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 202 REPORTS FROM THE MBL GENERAL SCIENTIFIC MEETINGS Reference: Biol. Bull. 193: 202-203. (October. 1997) Prediction of Maximum Allowable Retinal Slip Speed in the Fiddler Crab, Uca pugilator John E. La\ne (Duke University Marine Laboratory, 135 Duke Marine Lab Road, Beaufort, North Carolina 28516), Martina Wicklein1, Frederick A. Dodge2, and Robert B. Barlow2 Stabilizing eye movements reduce movement of the image on the retina (retinal slip), and thus are assumed to improve visual acuity by reducing blur. The reasoning behi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 202 REPORTS FROM THE MBL GENERAL SCIENTIFIC MEETINGS Reference: Biol. Bull. 193: 202-203. (October. 1997) Prediction of Maximum Allowable Retinal Slip Speed in the Fiddler Crab, Uca pugilator John E. La\ne (Duke University Marine Laboratory, 135 Duke Marine Lab Road, Beaufort, North Carolina 28516), Martina Wicklein1, Frederick A. Dodge2, and Robert B. Barlow2 Stabilizing eye movements reduce movement of the image on the retina (retinal slip), and thus are assumed to improve visual acuity by reducing blur. The reasoning behind this argu- ment is as follows. The response of individual photoreceptors (in the form of depolarization) to a brief flash of a given intensity is also brief. As is commonly observed in synaptic summation, the response to longer flashes is essentially a summation of many short-flash responses. After a period approximately equal to the duration of one short-flash response (Ts), the summation ceases, and the response reaches a steady state. Prolonging the flash does not further depolarize the cell. If a photoreceptor then samples a particular direction in space for more than T,,, it gains no new information. Assuming no change in the inten- sity of incident light, this means that the eye does not lose spatial information if a retinal slip equal to one visual angle per T,, (1,2) occurs. Here we present two measurements of the temporal dynamics of photoreceptors in the fiddler crab. Uca pugilator: T, and the frequency response. We will consider these in light of the theoretical allowable slip speeds for this animal. ERG measurements. The flash response time of Uca photore- ceptors was estimated from ERG measurements after the crabs had been adapted for four hours to total darkness in the re- cording chamber. Light flashes (\ = 570 nm, ^W/cm2) of increasing length were delivered at a frequency of 1 Hz. and the average amplitude of 15-20 ERGs was recorded. The flash duration a
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
