Cone Arrangements in Teleost Retinae

Abstract

1. There are four types of cone elements in teleosts: single, double, triple, and quadruple cones. The latter two types have only been found as typical elements in minnow (Phoxinus laevis) retinae. The constituent parts of a multiple cone may differ from each other in staining properties and size. 2. A regular arrangement of single and double cones is a feature of many teleost retinae, but these cone patterns are only associated with equal double cones. 3. Changes in the cone patterns occur during growth of the retinae. In trout (Salmo trutta) the pattern in young eyes has many more single cones than that in adult retinae. The loss of these single cones is probably due to their transmutation into rods. 4. The derivation of the typical cone arrangement in central regions of the retina from that found at the periphery has been studied in trout, minnow, and pike (Esox lucius). In all these species there is a similar basic cone pattern at the edge of the retina, although the arrangements in more central parts are very different. It appears that the triple and quadruple cones in minnow retinae are formed by the fusion of a single cone with a double cone and a triple cone respectively.