Fig. 5

Eight major types of complex eyes found in living animals, divided into two major categories: chambered eyes (top) and compound eyes (bottom). (A) and (B) form images using shadows, (C) to (F) use refraction, and (G) and (H) use reflection. The paths of light rays entering the eyes are indicated by dark lines. The photoreceptive structures are shown in shaded gray. (A) A simple pit eye, as found in Nautilus as well as many flatworms and annelids. (B) A basic compound eye in which each receptor is shielded from its neighbor by a simple pigment tube, as found in sea fans and a few bivalve mollusks. (C) A complex camera-type eye in which the lens does most of the focusing, as found in fishes and cephalopod mollusks. (D) A complex camera-type eye in which the cornea does most of the focusing, as found in terrestrial vertebrates and spiders. (E) An apposition compound eye, found in diurnal insects and many crustaceans. (F) A refracting superposition compound eye, as found in invertebrates in dim environments such as krill and moths. (G) A single-chambered eye in which an image is formed using a concave mirror, as found in some scallops. (H) A reflecting superposition eye, similar to (F) but with lenses replaced by mirrors, as found in lobsters and shrimps. Modified from Land and Nilsson (2002) and Fernald (2006), reproduced by permission of Oxford University Press and the American Association for the Advancement of Science