The molluscs have the widest variety of eye morphologies of any phylum, [1] and a large degree of variation in their function. Cephalopods such as octopus, squid, and cuttlefish have eyes as complex as those of vertebrates, while scallops have up to 100 simple eyes. [2]
There are between seven and eleven distinct eye types in molluscs. [3] Molluscs have eyes of all levels of complexity, from the pit eyes of many gastropods, to the pinhole eyes of the Nautilus , to the lensed eyes of the other cephalopods. Compound eyes are present in some bivalves, and reflective 'mirrors' have been innovated by other lineages such as scallops. [1] As well as varying in complexity, the eyes of molluscs span a huge range in size; they may be from 20 μm (0.0008 in) to 27 cm (11 in) across. [1]
Gastropods and cephalopods have paired eyes on their heads (and sometimes tails), [1] but many molluscs do not have clear head regions in which to locate the eyes. Consequently, many molluscs may have a multitude of eyes in more unlikely places, such as along the edge of their shell. [1] Chitons have a dispersed network of tiny eyes over the surface of their shells which may act together as a compound eye. [1] Many gastropods have stalked eyes; the eye can be retracted into the stalk itself in the presence of danger. [1]
Media related to Mollusca eyes at Wikimedia Commons
