Supported by grants to Doctor Dickson from the Medical Research Council of Canada and the Canadian National Institute for the Blind out of the E. A. Baker Foundation for the Prevention of Blindness.
Retinal development in the lamprey (Petromyzon marinus L.): Premetamorphic ammocoete eye
Article first published online: 3 FEB 2005
Copyright © 1979 Wiley-Liss, Inc.
American Journal of Anatomy
Volume 154, Issue 3, pages 321–336, March 1979
How to Cite
Dickson, D. H. and Collard, T. R. (1979), Retinal development in the lamprey (Petromyzon marinus L.): Premetamorphic ammocoete eye. Am. J. Anat., 154: 321–336. doi: 10.1002/aja.1001540303
- Issue published online: 3 FEB 2005
- Article first published online: 3 FEB 2005
- Manuscript Accepted: 4 OCT 1978
- Manuscript Received: 19 JUN 1978
Development of the retina of the ammocoete begins early in embryogenesis, with the formation of the optic vesicle, but development of the rudimentary eye is suspended and remains arrested during larval life. Prior to the onset of metamorphosis, the retina of the ammocoete is completely undifferentiated, with the exception of a small area (Zone II) surrounding the optic nerve head, where all of the adult retinal layers are found. The photoreceptors in this area have developed to include synaptic contacts as well as inner and outer segments. The pigment epithelium in this area, too, has differentiated to include well-formed melanin granules, myeloid bodies and endoplasmic reticulum and is closely associated with the receptor cell outer segments. With the approach of metamorphosis, differentiation of the remainder of the retina (Zone I) begins, taking place in a radial fashion from the optic nerve head. Differentiating pigment epithelial cells adjacent to the differentiated retinal zone begin to accumulate melanin granules. In the neural retina, junctional complexes are established in the form of an external limiting membrane, and connecting cilia project into the optic ventricle. Photoreceptor differentiation begins with the formation of a mitochondria-filled ellipsoid within the inner segment.
Development and differentiation of the ammocoete retina is unique to vertebrates in that only a small area of differentiated retina is present during the larval stage. The remainder of the retina differentiates and becomes functional during metamorphosis.