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Cephalopods, as active marine predators, possess sensory organs specialized for use in aquatic conditions. [1] They have a camera-type eye which consists of an iris, a circular lens, vitreous cavity (eye gel), pigment cells, and photoreceptor cells that translate light from the light-sensitive retina into nerve signals which travel along the optic nerve to the brain. [2]
There are two sets of ocular tentacles: one set in front of the eye (pre-ocular) and one set behind the eye (post-ocular). The digital and labial tentacles are arrayed circularly around the mouth, with the digital tentacles forming the outermost ring and the labial tentacles in between the digital tentacles and the mouth.
Pulmonate land snails usually have two sets of tentacles on their head: the upper pair have an eye at the end; the lower pair are for olfaction. [1]In anatomy, an eyestalk (sometimes spelled eye stalk and also known as an ommatophore) is a protrusion that extends an eye away from the body, giving the eye a better field of view. [1]
A cephalopod / ˈ s ɛ f ə l ə p ɒ d / is any member of the molluscan class Cephalopoda / s ɛ f ə ˈ l ɒ p ə d ə / (Greek plural κεφαλόποδες, kephalópodes; "head-feet") [3] such as a squid, octopus, cuttlefish, or nautilus.
Nautilus are unable to easily move across areas deeper than 800 metres, and most of their activity occurs at a depth of 100–300 metres deep. [4] Nautilus can occasionally be found closer to the surface than 100 metres, however, the minimum depth they can reach is determined by factors such as water temperature and season. [4]
Scallops have up to 100 simple eyes. 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.
Credit - Top row: Marco Di Marco—AP; Sofiia Gatilova—Reuters; Leo Correa–AP; Amr Alfiky—Reuters; John Moore—Getty Images; Bottom row: Anna Moneymaker—Getty Images; Jerome Brouillet ...
8 - nerve of the eye: Drawing of cross sections of the extracted tentacle (left) and constricted tentacle (right) with and eye of Helix pomatia. 1 - nerve of an eye 2 - 3 - 4 - eye 5 - tentacle ganglion 6 - epidermis 7 - 8 - nerve of an tentacle 9 - retractor muscle 10 - Well-developed lens eye of Eustrombus gigas on eyestalk has a black iris.