# Why are cave-dwelling fish blind? **URL:** \ **Category:** Factual Questions\ **Created:** [November 16, 2007, 1:17am UTC](https://boards.straightdope.com/t/why-are-cave-dwelling-fish-blind/426627 "2007-11-16T01:17:45Z")\ **Posts on this page:** 1\ **Showing post:** 40
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [November 19, 2007, 10:03pm UTC](https://boards.straightdope.com/t/why-are-cave-dwelling-fish-blind/426627/40 "2007-11-19T22:03:18Z")
[QUOTE=Ronald C. Semone] [quote=Triskadecamus ] Has anyone ever raised multiple generation of “cave fish” in normal light environments, and observed the nature of their development? Tris [/quote] Or more to the point, has anyone ever raised generations of sighted fish in a totally dark environment and monitored their development? [/QUOTE] Developmental studies [have been done](http://jhered.oxfordjournals.org/cgi/content/full/96/3/185) on both sighted and non-sighted versions of _Astyanax_. Note that development in light for sightless or the dark for sighted will not really reveal much, beyond the fact that eye loss in _Astyanax_ is an adaptation (i.e., it is not merely the developmental result of loss of light triggers; it is “programmed” at the genetic level). As **wevets** notes, the jury is still out on a definitive cause. However, the 2005 study that I linked demonstrates that midline signalling genes (specifically, _pax6_, _pax2_ and _hedgehog_) can act as protagonists during development, and that all act on the developing eye in some fashion. If one signal is increased, eye development is altered dramatically. It does remain to be demonstrated conclusively which of the other adaptations I mentioned (and which are mentioned in the linked study) are affected by the same triggers; as the author notes: > [@](#): > > The specific cavefish trait(s) that is positively regulated by Hh signaling and antagonistic to eye development is currently unknown. However, constructive features related to changes in cavefish feeding structures and behavior (Figure 2) are excellent candidates for such traits. In other vertebrates, _shh_ is expressed in developing teeth (Gritli-Linde et al. 2002), in tastebuds (Hall et al. 1999, 2003), and in craniofacial structures (Helms et al. 1997), all of which are enhanced or modified in cavefish (Jeffery 2001). In preliminary studies, my colleagues and I have shown that _shh_ expression is both sufficient and necessary for _Astyanax_ tastebud development (Yamamoto and Jeffery unpublished data). However, as also noted, hypoetheses based on energy conservation and neutral mutations are not supported by the current research. --- _[View the full topic](https://boards.straightdope.com/t/why-are-cave-dwelling-fish-blind/426627)._