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The molluscs have the widest variety of eye morphologies of any
'Camera eyes in gastropod molluscs"
mapoflife.org Molluscs have eyes of all levels of complexity, from the pit eyes of many
The molluscs have the widest variety of eye morphologies of any phylum
In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...
, and a large degree of variation in their function. Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...
s such as octopus
An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttle ...
, squid
True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...
, and cuttlefish
Cuttlefish or cuttles are marine molluscs of the order Sepiida. They belong to the class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique internal shell, the cuttlebone, which is used for control of ...
have eyes as complex as those of vertebrates, while scallops have up to 100 simple eye
Eyes are Organ (anatomy), organs of the visual system. They provide living organisms with Visual perception, vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of ...
s.
Diversity
There are between seven and eleven distinct eye types in molluscs.mapoflife.org Molluscs have eyes of all levels of complexity, from the pit eyes of many
gastropod
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...
s, to the pinhole eyes of the ''Nautilus
The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina.
It comprises six living species in ...
'', to the lensed eyes of the other cephalopod
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...
s. Compound eyes are present in some bivalves, and reflective 'mirrors' have been innovated by other lineages such as scallops. As well as varying in complexity, the eyes of molluscs span a huge range in size; they may be from to across.
Anatomy
Gastropods and cephalopods have paired eyes on their heads (and sometimes tails), 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. Chitons have a dispersed network of tiny eyes over the surface of their shells which may act together as a compound eye. Many gastropods have stalked eyes; the eye can be retracted into the stalk itself in the presence of danger.See also
*Arthropod eye
Apposition eyes are the most common form of eye, and are presumably the ancestral form of compound eye. They are found in all arthropod groups, although they may have evolved more than once within this phylum.
Some annelids and bivalves also h ...
* Parietal eye
A parietal eye, also known as a third eye or pineal eye, is a part of the epithalamus present in some vertebrates. The eye is located at the top of the head, is photoreceptive and is associated with the pineal gland, regulating circadian rhythm ...
* Sensory organs of gastropods
The sensory organs of gastropods (snails and slugs) include olfactory organs, eyes, statocysts and mechanoreceptors. Gastropods have no sense of hearing.Chase R.: ''Sensory Organs and the Nervous System''. in Barker G. M. (ed.): ''The biology of t ...
* Simple eye in invertebrates
A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...
* Vision in fish
Vision is an important sensory system for most species of fish. Fish eyes are similar to the eyes of terrestrial vertebrates like birds and mammals, but have a more spherical lens. Birds and mammals (including humans) normally adjust focus ...
* Visual system
The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (th ...
References
External links
{{vision in animals Eye Vision by taxon eye