The retina of the harbour seal, Phoca vitulina

• Published in: Canadian Journal of Zoology
• Main Authors: Jamieson, G. S., Fisher, H. D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1971
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; harbour seal; Harp Seal; Phoca vitulina
• Online Access: http://dx.doi.org/10.1139/z71-005; http://www.nrcresearchpress.com/doi/pdf/10.1139/z71-005

The structure of the retina of the harbour seal, Phoca vitulina richardii, is described. It is shown that the retina of the harbour seal is similar to that of the harp seal, in that it shows little zonation of the inner nuclear layer, possesses large horizontal cells, and has similar nuclear densities within the different retinal layers throughout the retina. The outer nuclear layer is also the thickest of all the retinal layers. Two types of photoreceptor cell, types B and C, were observed with a ratio of roughly 1:23 respectively. This ratio, along with a well-developed and extensive tapetum, indicates a highly light-sensitive retina. The existence of retinal folding in marine mammals is also questioned and discussed.