A morphometric study of the retinal ganglion cell layer and optic nerve from metamorphosis in Xenopus laevis

The number and distribution of cells in the retinal ganglion layer have been examined in Nissl-stained wholemounts during postmetamorphic life in Xenopus laevis. Total cell number at metamorphic climax, in the 3 and 4 month juveniles and in 5 year adults were 30,000-41,000, 45,000-51,000 and 71,000-82,000 respectively. Optic axon counts of 29,000, 39,000 and 58,000 at these stages suggested that most cells counted were ganglion cells and that their number doubled during this period. Cell distribution changed after metamorphosis producing nasal and temporal regions of higher density in juveniles and adults. These results are discussed in relation to retinal growth and plasticity of retinotectal connections.