Triple cones in the retinae of three anchovy species: Engraulis encrasicolus, Cetengraulis mysticetus and Anchovia macrolepidota (Engraulididae, Teleostei)

Histology and fine structure of three anchovy outer retinae is investigated by light- and electron microscopy and computer aided topographic mapping. They all possess novel linear triple cones with two large lateral components and one small central component. Engraulis encrasicolus has a polycone-dominated retina with two triple-cone sectors, the retinae of Cetengraulis mysticetus and Anchovia macrolepidota are triple-cone dominated. Interspecific differences in the configuration of the complex outer retina structures appear well adapted to the requirements of visual orientation in the respective photic habitats. In addition a survey on the occurrence of triple cones in teleosts is given.