The hagfish retina: electron microscopic study comparing receptor and epithelial cells in the Pacific hagfish, Polistotrema stouti, with those in the Atlantic hagfish, Myxine glutinosa.

Abstract

The fine structure of receptor and epithelial cells in the retina of the pacific hagfish, Polistotrema stouti, has been investigated and compared with previous observations made in the atlantic hagfish, Myxine glutinosa. The receptor cells in Polistotrema have cylindrical outer segments which consist of numerous discs arranged perpendicularly to the long axis of the cell. Characteristic synaptic bodies (synaptic lamellae) occur at the receptor base. Membranous inclusions in the epithelial cells suggest phagocytosis of outer segments. In Myxine, the outer segments are whorl-like, and synaptic bodies are absent at the receptor base. There are no signs of phagocytosis in the epithelial cells. The results are discussed from a functional and phylogenetical point of view.