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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.
By this definition the eight appendages of octopuses, though quite long, count as arms. [2] While arms are distinct from tentacles (a definition specific to the limb featuring peduncles), arms do fall within the general definition of "tentacle" as "a flexible, mobile, and elongated organ" and "tentacle" could be used as an umbrella term.
The tentacle consists of a thick central nerve cord (which must be thick to allow each sucker to be controlled independently) [96] surrounded by circular and radial muscles. Because the volume of the tentacle remains constant, contracting the circular muscles decreases the radius and permits the rapid increase in length.
Nautilus is a marine cephalopod genus in the mollusk family Nautilidae. Species in this genus differ significantly, morphologically, from the two nautilus species in the adjacent sister-taxon Allonautilus. [2]
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]
The mystery mollusks are hermaphrodites, which include both male and female reproductive organs. When it is time to release eggs, they descend and use their foot to temporarily attach to the seafloor.
The majority of the specimens researchers found sported eight tentacles, though some had as few as six and one had 11. Some were also seen with “visible eggs.”
The tentacles of the ancestral cephalopod developed from the mollusc's foot; [45] the ancestral state is thought to have had five pairs of tentacles which surrounded the mouth. [45] Smell-detecting organs evolved very early in the cephalopod lineage.