Editing Amblyopsidae (section)

==Description==
[[File:Forbesichthys agassizii.jpg|thumb|The [[spring cavefish]] (''Forbesichthys agassizii'') spends some time aboveground and its adaptions to an underground habitat are not as extreme as most species in the family]]

Amblyopsids are generally small, the [[northern cavefish]] (largest species in family) reaching up to {{convert|11|cm|in|abbr=on}} in length.<ref>{{FishBase genus | genus = Amblyopsis| month = May | year = 2017}}</ref>

The amblyopsids are probably ancient in origin. Adaptations common to many cavefish include reduced susceptibility to light, pigment loss, or reduction in skin scales,<ref name="Helfman">{{cite book |last1=Helfman |first1=G. |last2=Collette |first3=D. |last3=Facey |last4=Bowen |first4=BW |title=The Diversity of Fishes: Biology, Evolution, and Ecology |year=2009 |url=http://www.blackwellpublishing.com/helfman/ |publisher=Wiley-Blackwell |isbn=978-1-4051-2494-2 }}</ref> as well as development of [[chemoreceptor]]s in the sensory organs of the body surface and the [[lateral line]]. Three species exhibit efficient [[metabolism]] during swimming, as compared with a group of non-cave fish, and many cavefish species exhibit slender bodies adapted to swimming in fast-flowing waters.<ref name="Helfman" />

The cave-dwellers typically lack pigment and are somewhat translucent.<ref name=Romero/> They have a naked, moderately depressed head and an elongated body, covered with small cycloid irregular flakes, with tiny or absent [[pelvic fin]]s. The anal opening is so far forward that it is in the throat region.

The [[premaxilla]], a bone of the upper [[jaw]], is segmented, and the [[vomer]] has no [[teeth]]. They have no [[ventral fin]]s. The lateral line is incomplete, but well developed in some species. Its spine has between 27 and 35 [[vertebrae]].

Externally, they resemble [[killifish]]es in many respects, although their internal anatomy more closely resembles the [[trout-perch]]es, with which they are currently classified.<ref name=EoF>{{cite book |editor1=Paxton, J.R. |editor2=Eschmeyer, W.N. |author= Cohen, Daniel M.|year=1998|title=Encyclopedia of Fishes|publisher= Academic Press|location=San Diego|pages= 129|isbn= 0-12-547665-5}}</ref>

===Eyes===
The name of the family, Amblyopsidae, refers to their eyes (compare [[amblyopia]]). Most in this family are either [[Blind fish|blind]] or can only detect the difference between light and darkness. The true cave-dwellers have only rudimentary eyes, like so many other fauna that live in the dark.<ref name=Romero/>

Although some cave-dwellers have tiny, [[vestigial]] but functional eyes, others, such as the ''[[Amblyopsis]]'' and ''[[Typhlichthys]]'' have no eyes at all. Blindfish do, however, have rows of sensory [[wikt:papillae|papillae]] on their skin, which they use to help navigate.

Similar darkness-adaptive traits can be seen in [[Cavefish#Range and diversity|many fish families]] where members live underground and is known as [[convergent evolution]].<ref name=Romero/><ref name=Rantin2013>Rantin B., and M.E. Bichuette (2013). ''Phototactic behaviour of subterranean Copionodontinae Pinna, 1992 catfishes (Siluriformes, Trichomycteridae) from Chapada Diamantina, central Bahia, northeastern Brazil.'' International Journal of Speleology 41(1): 57–63</ref>