. The Biological bulletin. Biology; Zoology; Marine biology. 108 D. J. NUCKLEY ET corneal lenses corneagenous cell cone cell distal pigment cell reflecting pigment cell photoreceptor axon Figure 9. Schematic diagram of the organization of the retina of the compound eye of Palaemoneies showing the major cell types. This draw- ing is based on examination of Palaemoneies vulgaris in this study and published results for Palaemoneies pugio (Doughtie and Rao, 1984— figure 1) and does not include the effects of light and darkness or time of day on the structure of the retina. partite dioptrics i
. The Biological bulletin. Biology; Zoology; Marine biology. 108 D. J. NUCKLEY ET corneal lenses corneagenous cell cone cell distal pigment cell reflecting pigment cell photoreceptor axon Figure 9. Schematic diagram of the organization of the retina of the compound eye of Palaemoneies showing the major cell types. This draw- ing is based on examination of Palaemoneies vulgaris in this study and published results for Palaemoneies pugio (Doughtie and Rao, 1984— figure 1) and does not include the effects of light and darkness or time of day on the structure of the retina. partite dioptrics in Palaemoneies. The distal pigment cells in Palaemoneies that contain opaque screening pigment granules are probably represented by the ellipsoidal pigment cells along the inner surface of the retina in Rimicaris sp. The reflecting pigment cells, which in Palaemoneies are filled with vesicles, are probably rep- resented by the elaborated white diffusing cells in Rim- icaris sp. The screening pigment granules in the photo- receptors that migrate between the axons and the R-seg- ment in response to light and darkness in Palaemoneies are reduced in number in Rimicaris sp. and seem to be restricted to the axons and the A-segment below the nu- cleus. The geometrical, interleaved arrangement of mi- crovilli from the rhabdomeres of individual photorecep- tors in Palaemoneies (Fig. 8B, C) is replaced by a much larger, but less geometrical rhabdom in Rimicaris sp. Table I compares the classes of retinal cells of Palae- moneies and Rimicaris sp. The suggested evolution of the stalked eyes of Palae- moneies into the dorsal eye oi Rimicaris sp. can be sum- marized as follows (compare Figs. 7 and 9). The dioptric apparatus is gone. Although the number of ommatidia is unchanged, each is larger so that the volume of the eye is increased. The sensitivity of the retina is likely further enhanced by a sevenfold to eightfold increase in the vol- ume density of photosensitive membrane in the rha
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