Editing Cephalopod (section)

===Senses===
Cephalopods have advanced vision, can detect gravity with [[statocyst]]s, and have a variety of chemical sense organs.<ref name=Cephalopods/>{{Rp|34}} Octopuses use their arms to explore their environment and can use them for depth perception.<ref name=Cephalopods/>

====Vision====
{{Main|Cephalopod eye|mollusc eye}}
[[File:Nautilus pompilius (head).jpg|thumb|right|250px|The primitive [[nautilus]] eye functions similarly to a [[pinhole camera]].]]
[[File:Sepia eyelid shape.theora.ogv|thumb|right|250px|The W-shaped pupil of the cuttlefish expanding when the lights are turned off]]
Most cephalopods rely on vision to detect predators and prey and to communicate with one another.<ref name=Serb2008>{{cite journal|first1=J. M. |first2=D. J. |last2=Eernisse |title=Charting Evolution's Trajectory: Using Molluscan Eye Diversity to Understand Parallel and Convergent Evolution |last1=Serb |s2cid=2881223 |journal=Evolution: Education and Outreach|volume=1|issue=4 |pages=439–447 |year=2008 |doi=10.1007/s12052-008-0084-1|doi-access=free}}</ref> Consequently, cephalopod vision is acute: training experiments have shown that the [[common octopus]] can distinguish the brightness, size, shape, and horizontal or vertical orientation of objects. The morphological construction gives cephalopod eyes the same performance as shark eyes; however, their construction differs, as cephalopods lack a cornea and have an everted retina.<ref name=Serb2008/> Cephalopods' eyes are also sensitive to the plane of [[Polarization (waves)|polarization]] of light.<ref>{{cite journal|title=Part M, Chapter 4: Physiology of Coleoids|journal=Treatise Online|first=Martin J.|last=Wells|place=Lawrence, Kansas, USA|url=http://129.237.145.244:591/FMPro?-db=treatiseonline&-format=treatiseonline%2fdetails.html&-lay=table&-sortfield=sortnumber&-recid=11&-findall=|year=2011|doi=10.17161/to.v0i0.4226|access-date=2013-05-10|archive-url=https://web.archive.org/web/20160822014821/http://129.237.145.244:591/FMPro?-db=treatiseonline&-format=treatiseonline%2fdetails.html&-lay=table&-sortfield=sortnumber&-recid=11&-findall=|archive-date=2016-08-22|url-status=dead|doi-access=free}}{{subscription required}}</ref> Unlike many other cephalopods, [[nautilus]]es do not have good vision; their eye structure is highly developed, but lacks a solid [[lens (anatomy)|lens]]. They have a simple "[[Pinhole camera|pinhole]]" eye through which water can pass. Instead of vision, the animal is thought to use [[olfaction]] as the primary sense for [[foraging]], as well as locating or identifying potential mates.

[[File:Cuttlefish eye.jpg|thumb|250px|A cuttlefish with W-shaped pupils which may help them discern colors]]
All octopuses<ref name=Boyle/> and most cephalopods<ref name="Messenger-17">{{cite book |last1=Messenger |first1=John B. |first2=Roger T. |last2=Hanlon |title=Cephalopod Behaviour |publisher=Cambridge University Press|year=1998 |location=Cambridge |pages=17–21 |isbn=978-0-521-64583-6}}</ref><ref>{{Cite journal|last1=Chung |first1=Wen-Sung |last2=Marshall |first2=N. Justin |date=2016-09-14 |title=Comparative visual ecology of cephalopods from different habitats|journal=Proceedings of the Royal Society B: Biological Sciences|language=en |volume=283|issue=1838 |pages=20161346 |doi=10.1098/rspb.2016.1346 |issn=0962-8452 |pmc=5031660|pmid=27629028}}</ref> are considered to be [[color blind]]. Coleoid cephalopods (octopus, squid, cuttlefish) have a single photoreceptor type and lack the ability to determine color by comparing detected photon intensity across multiple spectral channels. When [[camouflage|camouflaging]] themselves, they use their chromatophores to change brightness and pattern according to the background they see, but their ability to match the specific color of a background may come from cells such as [[iridophore]]s and [[leucophore]]s that reflect light from the environment.<ref>Hanlon and Messenger, 68.</ref> They also produce visual pigments throughout their body and may sense light levels directly from their body.<ref>{{cite journal|last1=Mäthger |first1=L. |last2=Roberts |first2=S. |last3=Hanlon |first3=R. |title=Evidence for distributed light sensing in the skin of cuttlefish, ''Sepia officinalis'' |journal=Biology Letters |volume=6|issue=5 |pages=600–603 |year=2010 |pmid=20392722 |pmc=2936158 |doi=10.1098/rsbl.2010.0223}}</ref> Evidence of [[color vision]] has been found in the [[sparkling enope squid]] (''Watasenia scintillans'').<ref name="Messenger-17" /><ref name=Michinomae1994>{{cite journal|last1=Michinomae |first1=M. |last2=Masuda |first2=H. |last3=Seidou |first3=M. |last4=Kito |first4=Y.|title=Structural basis for wavelength discrimination in the banked retina of the firefly squid ''Watasenia scintillans'' |journal=Journal of Experimental Biology|volume=193|issue=1 |pages=1–12 |year=1994 |doi=10.1242/jeb.193.1.1|pmid=9317205|doi-access=free |bibcode=1994JExpB.193....1M }}</ref> It achieves color vision with three [[photoreceptor protein|photoreceptors]], which are based on the same [[opsin]], but use distinct [[retinal]] molecules as chromophores: A1 (retinal), A3 (3-dehydroretinal), and A4 (4-hydroxyretinal). The A1-photoreceptor is most sensitive to green-blue (484&nbsp;nm), the A2-photoreceptor to blue-green (500&nbsp;nm), and the A4-photoreceptor to blue (470&nbsp;nm) light.<ref name=Seidou1990>{{cite journal|last1=Seidou |first1=M. |last2=Sugahara |first2=M. |last3=Uchiyama |first3=H. |last4=Hiraki |first4=K. |last5=Hamanaka |first5=T. |last6=Michinomae|first6=M. |last7=Yoshihara |first7=K. |last8=Kito |first8=Y. |s2cid=25707481 |title=On the three visual pigments in the retina of the firefly squid, ''Watasenia scintillans'' |journal=Journal of Comparative Physiology A|volume=166|issue=6 |year=1990 |doi=10.1007/BF00187321}}</ref>

In 2015, a novel mechanism for spectral discrimination in cephalopods was described. This relies on the exploitation of [[chromatic aberration]] (wavelength-dependence of focal length). Numerical modeling shows that chromatic aberration can yield useful chromatic information through the dependence of image acuity on accommodation. The unusual off-axis slit and annular pupil shapes in cephalopods enhance this ability by acting as prisms which are scattering white light in all directions.<ref name="Stubbs">{{cite bioRxiv |last1=Stubbs |first1=A. L. |last2=Stubbs |first2=C. W. |year=2015 |title=A novel mechanism for color vision: Pupil shape and chromatic aberration can provide spectral discrimination for 'color blind' organisms |biorxiv=10.1101/017756}}</ref><ref>{{cite web |title=Octopus Eyes Are Crazier Than We Imagined |date=2016-07-06 |website=[[Gizmodo]]|archive-url=https://web.archive.org/web/20230430021550/https://gizmodo.com/octopus-eyes-are-crazier-than-we-imagined-1783195433 |archive-date=2023-04-30 |url-status=live |url=https://gizmodo.com/octopus-eyes-are-crazier-than-we-imagined-1783195433}}</ref>

====Photoreception====
In 2015, molecular evidence was published indicating that cephalopod chromatophores are photosensitive; reverse transcription polymerase chain reactions (RT-PCR) revealed [[Primary transcript|transcripts]] encoding [[rhodopsin]] and [[retinochrome]] within the retinas and skin of the [[longfin inshore squid]] (''Doryteuthis pealeii''), and the [[common cuttlefish]] (''Sepia officinalis'') and broadclub cuttlefish (''[[Sepia latimanus]]''). The authors claim this is the first evidence that cephalopod dermal tissues may possess the required combination of molecules to respond to light.<ref name="Kingston2015">{{cite journal|last1=Kingston|first1=A. C. |last2=Kuzirian |first2=A. M. |last3=Hanlon |first3=R. T. |last4=Cronin |first4=T. W. |s2cid=25431963 |year=2015 |title=Visual phototransduction components in cephalopod chromatophores suggest dermal photoreception |journal=Journal of Experimental Biology|volume=218|issue=10 |pages=1596–1602 |doi=10.1242/jeb.117945 |pmid=25994635 |doi-access=free |bibcode=2015JExpB.218.1596K |hdl=11603/13387 |hdl-access=free}}</ref>

====Hearing====
Some squids have been shown to detect sound using their [[statocyst]]s,<ref>{{cite news |url=http://news.bbc.co.uk/earth/hi/earth_news/newsid_8095000/8095977.stm |work=BBC News|title=The cephalopods can hear you|date=2009-06-15 |access-date=2010-04-28}}</ref> but, in general, cephalopods are deaf.