Premium
Retinal structure in the smooth dogfish, Mustelus canis : Light microscopy of photoreceptor and horizontal cells
Author(s) -
Stell William K.,
Witkovsky Paul
Publication year - 1973
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901480103
Subject(s) - rod , anatomy , biology , retina , geometry , columnar cell , biophysics , optics , physics , mathematics , neuroscience , medicine , genetics , alternative medicine , pathology , epithelium
Photoreceptor and horizontal cells in retinas of the smooth dogfish were impregnated by the rapid Golgi method. Cones as well as rods are present; there are hundreds of rods per cone. The rod synaptic endings are small spherules which send out basal processes (telodendria). The cone synaptic endings are large pedicles which also extend telodendria. Horizontal cells of three distinctive varieties are segregated in vertically separate layers. Horizontal cells of the first (external) row are thick and cuboidal. They send out processes which enter into the invaginations in rod spherules. These cells and their processes cover a circular to elliptical field measuring 75–125 by 125–200 μm. They probably contact every rod in this field. Horizontal cells of the second (intermediate) row are flattened and stellate. Their processes also enter into the rod spherules. These cells cover a circular to elliptical field slightly larger than that covered by cells of the first row. Although they appear not to contact every rod in their field, the fields of adjacent cells of this type overlap. Every rod, therefore, probably contacts one horizontal cell of the second row as well as one of the first row. Horizontal cells of the third (internal) row are stellate, with a few long cylindrical horizontal processes. Finer vertical processes go from these to contact cone pedicles. Probably each cone contacts one such process, and each third‐row horizontal cell contacts on the order of ten cones. Although somewhat uncertain, the size, shape, and degree of overlap of the fields covered by third‐row cells are probably not very different from those of first‐ and second‐row cells. The vertical sequence of horizontal cells which contact rods or cones in dogfish is inverted from that in teleosts.