Editing Cephalopod (section)

===Head appendages===
{{Main|Cephalopod limb|tentacle}}
Cephalopods, as the name implies, have muscular appendages extending from their heads and surrounding their mouths. These are used in feeding, mobility, and even reproduction. In [[Coleoidea|coleoids]] they number eight or ten. Decapods such as cuttlefish and squid have five pairs. The longer two, termed "[[tentacle]]s", are actively involved in capturing prey;<ref name="mollusca11" />{{Rp|225}} they can lengthen rapidly (in as little as 15 milliseconds<ref name="mollusca11"/>{{Rp|225}}). In [[giant squid]], they may reach a length of 8 metres. They may terminate in a broadened, sucker-coated club.<ref name="mollusca11"/>{{Rp|225}} The shorter four pairs are termed ''[[cephalopod arm|arms]]'', and are involved in holding and manipulating the captured organism.<ref name="mollusca11"/>{{Rp|225}} They too have suckers, on the side closest to the mouth; these help to hold onto the prey.<ref name="mollusca11"/>{{Rp|226}} Octopods only have four pairs of sucker-coated arms, as the name suggests, though developmental abnormalities can modify the number of arms expressed.<ref name="Toll1991">{{cite journal|last1=Toll |first1=R. B. |last2=Binger |first2=L. C. |s2cid=34858474 |title=Arm anomalies: Cases of supernumerary development and bilateral agenesis of arm pairs in Octopoda (Mollusca, Cephalopoda)|journal=Zoomorphology|volume=110|issue=6 |pages=313–316 |year=1991 |doi=10.1007/BF01668021}}</ref>

The tentacle consists of a thick central nerve cord (which must be thick to allow each sucker to be controlled independently)<ref>{{cite book |year=1912 |title=Anatomy of the Common Squid}}</ref> 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. Typically, a 70% lengthening is achieved by decreasing the width by 23%.<ref name="mollusca11"/>{{Rp|227}} The shorter arms lack this capability.

The size of the tentacle is related to the size of the buccal cavity; larger, stronger tentacles can hold prey as small bites are taken from it; with more numerous, smaller tentacles, prey is swallowed whole, so the mouth cavity must be larger.<ref>Nixon 1988 in {{cite journal|first1=M. G. E. |first2=J. |title=''Allocrioceras'' from the Cenomanian (mid-Cretaceous) of the Lebanon and its bearing on the palaeobiological interpretation of heteromorphic ammonites|last1=Wippich |journal=Palaeontology|volume=47|issue=5 |pages=1093–1107 |year=2004 |doi=10.1111/j.0031-0239.2004.00408.x |last2=Lehmann |bibcode=2004Palgy..47.1093W |doi-access=free}}</ref>

Externally shelled [[Nautilidae|nautilids]] (''[[Nautilus]]'' and ''[[Allonautilus]]'') have on the order of 90 finger-like appendages, termed ''tentacles'', which lack suckers but are sticky instead, and are partly retractable.