Microscopic anatomy of the eye of the deep-diving Antarctic Weddell seal (Leptonychotes weddellii)
Version of Record online: 10 APR 2001
Copyright © 2001 Wiley-Liss, Inc.
Journal of Morphology
Volume 248, Issue 2, pages 165–174, 1 May 2001
How to Cite
Welsch, U., Ramdohr, S., Riedelsheimer, B., Hebel, R., Eisert, R. and Plötz, J. (2001), Microscopic anatomy of the eye of the deep-diving Antarctic Weddell seal (Leptonychotes weddellii). J. Morphol., 248: 165–174. doi: 10.1002/jmor.1027
- Issue online: 10 APR 2001
- Version of Record online: 10 APR 2001
- Weddell seal;
- canal of Schlemm;
- area centralis
The microscopic anatomy of the eye of the Weddell seal was studied with various light and electron microscopic methods with a view to correlating morphological findings with the biology of this seal which is adapted to the extremes of the Antarctic environment and to extreme diving excursions into the lightless depths of the sea. In the retina an area centralis was found but no fovea centralis. The densely packed photoreceptors consist exclusively of highly differentiated rods, which in primates detect light at low intensity but have rather poor image discrimination. The ganglion cells are relatively scarce, suggesting a high degree of convergence of the light-sensitive cells on the ganglion cells. The pigment epithelium is almost devoid of pigment granules. The extensive tapetum lucidum is about 400–500 μm thick and is composed of about 30 layers of specialized cells. The cornea is 650 (center) to 800–900 (periphery) μm thick. Its structure and glycosaminoglycan histochemistry correspond to that of other mammals. The iridocorneal angle is unusually deep and pervaded by an elaborate trabecular meshwork, which together with a complex canal of Schlemm can be correlated with the ability to absorb large amounts of fluid. The ciliary muscle and its antagonist, the membrane of Bruch, are poorly developed, suggesting relatively poor abilities of accommodation. The combination of a well-developed tapetum lucidum, an unpigmented pigment epithelium, well-developed rods, and a high number of rods converging on only few ganglion cells is obviously an adaptation to an extreme light sensitivity, enabling the animals to make use of the little light available in the deep sea. J. Morphol. 248:165–174, 2001. © 2001 Wiley-Liss, Inc.