Spectral Sensitivity of the Common Prawn, Palaemonetes vulgaris

Abstract

The vision of Palaemonetes is of particular interest in view of extensive studies of the responses of its chromatophore systems and eye plgments to light. The spectral sensitvity is here examined under conditions of dark adaptation and adaptation to bright colored lights. In each case the relative number of photons per one-fiftieth sec flash needed to evoke a constant peak amplitude (usually 25 or 50 [mu]v) in the electroretinogram (ERG) was measured at various wavelengths throughout the spectrum. The sensitivity is the reciprocal of this number. In dark-adapted animals the spectral sensitvity curve consists of a broad almost symmetrical band, maximal at about 540 m[mu], with a shoulder near 390 m[mu], Adaptation to bright red or blue light, left on continuously throughout the measurements, depresses the 540 m[mu] peak without notably changing its shape or position, implying that only one visual plgment operates in this region. Adaptation to red light, however, spares a violet-sensitive system, so that a high, narrow peak at 390 m[mu] now dominates the spectral sensitivity function. The 540 and 390 m[mu] peaks are apparently associated with different visual plgments; and these seem to be segregated in different receptor systems, since the associated ERG''s have markedly different time constants. It is suggested that these 2 sensitivity bands may represent the red- and violet-sensitive components of an apparatus for color differentiation.