Pure-Cone Retinae and Retinomotor Responses in Larval Teleosts

A pure-cone retina has been reported in the larval stages of teleosts from three families, viz. the salmon Oncorhynchus spp. by Ali (1959), the herring Clupea harengus by Blaxter & Jones (1967) and plaice Pleuronectes platessa by Blaxter (1968 a). There is also an absence of any retinomotor responses (movement of retinal masking pigment and changes in the relative positions of the visual cells) until the rods develop, which is usually at metamorphosis where this is clear-cut. Most adult teleosts are known to have a duplex retina.