Simple Photoreceptors in Limulus polyphemus

Abstract

The "olfactory nerve," the endoparietal eye, and the rudimentary lateral eyes of Limulus (polyphemus) contain simple photoreceptor cells that duplicate many of the electrical responses of the retinular cells of the lateral eye; the responses are a receptor potential consisting of aninitial transient phase and a subsequent steady phase,low-amplitude fluctuations, and a small locally regenerative response to pulses of both light and current. Photic stimulation does not induce conducted action potentials, but does increase the membrane conductance. The receptor potentialrequires the presence of sodium ions in the external medium. Measurements of action and absorption spectra indicate a photopigment whose maximum absorption is of light with wavelength of 535 nanometers. The functional significance of these cells has not been ascertained.

Membrane properties of a barnacle photoreceptor examined by the voltage clamp technique

“…This suggests a possible mechanism of suppression. As shown previously, the major (Smith et al 1968 (Millecchia et al 1966;Smith et al 1968). In the barnacle receptor, however, the response is not transiently abolished and there is no increase of the response with time in Na-free solution.…”

Photosensitivity of the Central Nervous System of Limulus polyphemus

“…Limulus has four kinds of photoreceptors: lateral eyes, median ocelli, ventral photoreceptors and mini-ommatidia. The latter two kinds of photoreceptors are located internally: the ventral photoreceptors are distributed along the ventral optic nerves and are most sensitive to light of 535 nm (Millecchia et al ., 1966); and the mini-ommatidia are distributed in the median optic nerves and are sensitive to light of 380 nm (Samie et al ., 1995). In addition, it has been suggested that there are photosensitive cells in the telson (Hanna et al ., 1985;1988).…”

Distinct lobes of Limulus ventral photoreceptors. II. Structure and ultrastructure.

“…Since they were originally proposed for the physiological study of phototransduction (Millecchia et al, 1966), the ventral photoreceptors of Limulus polyphemus have become an important model system for studies of how photoreceptors transduce light. Among their advantages as a model system must be counted their large size, which allows multiple penetrations with intracellular electrodes and selective illumination of portions of the cell; the ease with which their extracellular environment can be manipulated; and their survival as transducing cells in vitro.…”