Photopigment and spectral sensitivity in the bioluminescent fish Porichthys notatus

Digitonin extracts from retinas of the marine fish Porichthys notatus, from California and Puget Sound (USA), contain a single photopigment with maximum absorbance at 498 nm. In the presence of hydroxylamine the final product of bleaching absorbs maximally at 367 nm, indicating that the photopigment is based on retinal. Spectral sensitivity measurements performed on intact eyes and eye-cup preparations in darkadapted and selectively light-adapted states yield curves which suggest that the retina of P. notatus contains at least 3 different types of receptors. In the darkadapted state, the spectral sensitivity curve has a broad peak, with a maximum between 480 and 500 nm. In the blue and red light-adapted states, in addition to depressing the sensitivity, the shape of the sensitivity curve also changes. Under these conditions new peaks appear which suggest the presence of at least two different types of cones, with sensitivity maxima in the blue and the green regions of the spectrum, respectively. Comparison of the spectral sensitivity curves with the in vivo bioluminescence emission spectrum of the fish gives an especially good correspondence and suggests that the fish is able to perceive the bioluminescence of its own species.