Editing Jumping spider (section)

== Vision ==
[[File:Jumping spider vision David Hill.svg|thumb|The visual fields of a jumping spider]]
[[File:Telamonia dimidiata female.jpg|thumb|The eight eyes of a ''[[Telamonia dimidiata]]'' located near the front]] 
[[File:Phidippus audax male.jpg|thumb|Adult male ''[[Phidippus audax]]'']]
Jumping spiders have four pairs of eyes; three secondary pairs that are fixed and a principal pair that is movable.

The posterior median eyes are [[Vestigiality|vestigial]] in many species, but in some primitive subfamilies, they are comparable in size with the other secondary eyes and help to detect motion.<ref>{{cite journal |title=short communication fields of view of the eyes – The Company of Biologists Limited 1985 |journal=Journal of Experimental Biology |date=November 1985 |volume=119 |issue=1 |pages=381–384 |doi=10.1242/jeb.119.1.381 |url=http://jeb.biologists.org/content/119/1/381.full.pdf |access-date=13 August 2013 |last1=Land |first1=M. F. }}</ref> While unable to form images, the reduced pair of eyes is thought to have a role similar to that of insect ocelli by receiving light from the sky. The photoreceptors in the other secondary pairs are almost exclusively green-sensitive, but the posterior median eyes have two visual [[opsin]]s different from those in all the other eyes, sensitive to blue and UV light.<ref>[http://www.bioone.org/doi/full/10.2108/zs140094 Functional Properties of Opsins and their Contribution to Light-Sensing Physiology]</ref>

The posterior lateral eyes (PLEs) are wide-angle motion detectors that sense motions from the side and behind. Combined with the other eyes, PLEs give the spider a near 360° view of the world.

The anterior lateral eyes (ALEs) have the best [[visual acuity]] of the secondary eyes.<ref name="Zurek2012">{{cite journal |last1=Zurek |first1=Daniel B. |last2=Nelson |first2=Ximena J. |date=August 2012 |title=Hyperacute motion detection by the lateral eyes of jumping spiders |journal=Vision Research |doi=10.1016/j.visres.2012.06.011 |pmid=22750020 |volume=66 |pages=26–30|doi-access=free |hdl=10092/17539 |hdl-access=free }}</ref> They are able to distinguish some details, as well, and without them, no "looming response" can be triggered by motion.<ref>{{cite web |date=17 October 2012 |title=Jeepers, Peepers: Why Spiders Have So Many Eyes |publisher=Livescience.com |url=http://www.livescience.com/24054-why-spiders-have-eight-eyes.html |access-date=13 August 2013}}</ref> Even with all the other pairs covered, jumping spiders in a study could still detect, stalk, and attack flies, using their ALEs only, which are also sufficiently widely spaced to provide stereoscopic vision.<ref name="Zurek2010">{{cite journal |last1=Zurek |first1=D. B. |last2=Taylor |first2=A. J. |last3=Evans |first3=C. S. |last4=Nelson |first4=X. J. |date=25 June 2010 |title=The role of the anterior lateral eyes in the vision-based behaviour of jumping spiders |journal=Journal of Experimental Biology |doi=10.1242/jeb.042382 |pmid=20581266 |volume=213 |issue=14 |pages=2372–2378|doi-access=free |bibcode=2010JExpB.213.2372Z |hdl=10092/17412 |hdl-access=free }}</ref>

The [[Anatomical terms of location|anterior]] median eyes have very good [[Visual perception|vision]]. This pair of eyes is built like a telescopic tube with a corneal lens in the front and a second lens in the back that focus images onto a four-layered retina, a narrow, boomerang-shaped strip oriented vertically.<ref>{{cite journal|url=http://archopht.jamanetwork.com/article.aspx?articleid=420035 |title=Eye on the Web |publisher=Archopht.jamanetwork.com |date=21 August 2007 |doi=10.1001/archopht.125.11.1557 |access-date=13 August 2013|last1=Rozenbaum |first1=Ilya |last2=Ritch |first2=R. |journal=Archives of Ophthalmology |volume=125 |issue=11 |page=1557 |pmid=17998517 |url-access=subscription }}</ref><ref name=HarlJack00/> Physiological experiments have shown they may have up to four different kinds of receptor cells, with different [[absorption spectrum|absorption spectra]], giving them the possibility of [[tetrachromacy|tetrachromatic]] [[color vision]], with sensitivity extending into the [[ultraviolet]] (UV) range.<ref name=PeasWils89 /> As the eyes are too close together to allow [[depth perception]], and the animals do not make use of [[Parallax|motion parallax]], they have instead evolved a method called image defocus. Of the four photoreceptor layers in the retina, the two closest to the surface contain a UV-sensitive opsin (visual pigment), while the two deepest contain a green-sensitive opsin. The incoming green light is only focused on the deepest layer, while the other one receives defocused or fuzzy images. By measuring the amount of defocus from the fuzzy layer, calculating the distance to the objects in front of them is possible.<ref>{{cite web|url=http://www.livescience.com/18143-jumping-spider-unique-vision.html |title=Jumping Spiders' Unique Vision Revealed |publisher=Livescience.com |date=26 January 2012 |access-date=13 August 2013}}</ref><ref>{{cite journal |last1=Nagata |first1=Takashi |last2=Koyanagi |first2=Mitsumasa |last3=Tsukamoto |first3=Hisao |last4=Saeki |first4=Shinjiro |last5=Isono |first5=Kunio |last6=Shichida |first6=Yoshinori |last7=Tokunaga |first7=Fumio |last8=Kinoshita |first8=Michiyo |last9=Arikawa |first9=Kentaro |last10=Terakita |first10=Akihisa |title=Depth Perception from Image Defocus in a Jumping Spider |journal=Science |date=27 January 2012 |volume=335 |issue=6067 |pages=469–471 |doi=10.1126/science.1211667 |pmid=22282813|bibcode=2012Sci...335..469N |s2cid=8039638 |url=https://ir.soken.ac.jp/?action=repository_action_common_download&item_id=4203&item_no=1&attribute_id=22&file_no=1}}</ref> In addition to receptor cells, red filters also have been detected, located in front of the cells that normally register green light.<ref>[http://www.futurity.org/jumping-spiders-vision-925522/ Filters let jumping spiders spot flashy mates]</ref> All salticids, regardless of whether they have two, three, or four kinds of color receptors, seemingly are highly sensitive to UV light.<ref name=PeasWils89/> Some species (such as ''[[Cosmophasis umbratica]]'') are highly [[Sexual dimorphism|dimorphic]] in the UV spectrum, suggesting a role in sexual signaling.<ref>(Lim & Li, 2005).</ref> Color discrimination has been demonstrated in behavioral experiments.

The anterior median eyes have high resolution (11 [[minute of arc|min]] [[visual angle]]),<ref>{{cite journal|url=http://jeb.biologists.org/cgi/content/abstract/51/2/443 |title=Structure of the Retinae of the Principal Eyes of Jumping Spiders (Salticidae: Dendryphantinae) in Relation to Visual Optics |pmid=5351425|year=1969|last1=Land|first1=MF|volume=51|issue=2|pages=443–70|journal=The Journal of Experimental Biology|doi=10.1242/jeb.51.2.443 |bibcode=1969JExpB..51..443L |url-access=subscription}}</ref> but the field of vision is narrow, from 2 to 5°. The central region of the retina, where acuity is highest, is no more than six or seven receptor rows wide. However, the eye can scan objects off the direct axis of vision. As the lens is attached to the carapace, the eye's scanning movements are restricted to its retina through a complicated pattern of translations and rotations.<ref>{{cite web|url=http://www.mapoflife.org/topics/topic_281_Scanning-eyes-in-molluscs-and-arthropods/ |title=Topic: Scanning eyes in molluscs and arthropods |publisher=Mapoflife.org |access-date=13 August 2013}}</ref> This dynamic adjustment is a means of compensation for the narrowness of the static field of vision. Movement of the retina in jumping spiders is analogous to the way many [[vertebrate]]s, such as [[primate]]s, move their entire eyes to focus images of interest onto their [[fovea centralis]]. In jumping spiders with a translucent carapace, such movements within the jumping spider's eyes are visible from outside when the attention of the spider is directed to various targets.<ref>{{cite journal|author=Land, M. F. |title=Movements of the retinae of jumping spiders (Salticidae: Dendryphantinae) in response to visual stimuli|pmid=5351426|url=http://jeb.biologists.org/content/51/2/471.full.pdf|year=1969|volume=51|issue=2|pages=471–93|journal=The Journal of Experimental Biology|doi=10.1242/jeb.51.2.471|bibcode=1969JExpB..51..471L }}</ref>