Figure 4. Density of the chlorophyll-like substance in different layers of the Malacosteus niger retina determined by absorption spectroscopy of retinal cryosections.

The absorbance at 673 nm due to the chlorophyll-like substance in different retinal layers, was estimated by taking the absorbance at this wavelength and subtracting the background absorbance (calculated by taking the average of the absorbance 25 nm either side of 673 nm). In this way the effect of absorbance not due to the chlorophyll-like substance, such as astaxanthin, was greatly reduced. The data shown for the eight transect positions, are averages (+/−SD) from cryosections taken at five different retinal locations. The transect positions are shown in Fig. 3. The highest concentration of the bacteriochlorophyll is at the RPE/ROS border in the region containing the tapetal spheres, although one cannot assume it is actually in the spheres rather than the ROS. All labels as in Fig. 1.