Mengual, R.; Segovia, Y. & García, M.

Summary

There is a close relationship between morphological features of sensory systems, their function and habitat to which these organisms are adapting. In this sense, of all marine mammals that have been studied, cetaceans are the ones that have profoundly changed structure and ocular physiology in their adaptation to an exclusively aquatic life. To add further data to the literature, the aim of this paper is to describe morphologically the retina of the pilot whale through optical microscopy and relate their adaptation to the aquatic environment. Our data show that the retina of the long-finned pilot whale is organized according to the same basic plan of vertebrates. It has an average thickness of about 330±23 microns in areas of high ganglion cell density of 175±2 microns in the peripheral zone. Photoreceptor layer corresponds to 45% of total thickness of the retina and has long outer segments. The most significant characteristic of cetaceans in general and long-finned pilot whale in particular, is the ganglion cell layer. Thickness of 77.76±37.26 being the most variable of the entire retina. This layer has a low density but exceptionally large cell size of 10 to 75 microns (average of 33.5 microns), known as giant ganglion cells.

KEY WORDS: Globicephala melas; Cetacean vision; Retina.

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