Pax 6 is a master control gene for eye morphogenesis; sequence comparisons have shown that evolution has recruited crystallins among already existing heat-shock proteins and stress-inducible enzymes,
or the use of existing proteins in the development of new structures;
The genetic control of eye development and its implications for the evolution of the various eye-types,
pretty stright forward;
The finding of Pax-6 from flatworms to humans suggests that eyeless is a universal master control gene and that the various types of eyes in the various animal phyla may have evolved from a single prototype... The wide variety of eyes in the animal kingdom may, therefore, have evolved from a single ancestral photosensitive organ...
Common descent? Ruh roh!;
Hmmm... Is this your "money shot"?
The evolutionary mechanisms responsible for eye degeneration in cave-adapted animals have not been resolved... (But) the manner of eye development and degeneration, the ability to experimentally restore eyes, gene expression patterns, and comparisons between different cavefish populations all provide important clues for understanding the evolutionary forces responsible for eye degeneration. A key discovery is that Hedgehog midline signaling is expanded and inhibits eye formation by inducing lens apoptosis in cavefish embryos. Accordingly, eyes could have been lost by default as a consequence of natural selection for constructive traits, such as feeding structures, which are positively regulated by Hh signaling. We conclude from these studies that eye degeneration in cavefish may be caused by adaptive evolution and pleiotropy.
Pleiotrophy is where a mutation in a single gene can influence multiple phenotypic traits - in other words, it is not a question of gain or loss, the eye morphology is a product of adaptation and selection of a beneficial mutation.
“As a result of lens transplantation, adult cavefish were obtained with a completely differentiated eye on one side of their head (Jeffery et al. 2003; Yamamoto and Jeffery 2000). Remarkably, orbital bone structure resembling the surface fish phenotype is also induced on the side of the head containing the restored eye, whereas the other side of the head has the craniofacial structure typical of cavefish (Figure 4C, D; Yamamoto et al. 2003). These results suggest that the lens dictates craniofacial morphology by controlling eye growth. Recent studies have shown that more retinal nerve fibers project from the restored eye to the contralateral optic tectum, which is also increased in size, suggesting that cavefish with a transplanted eye may be capable of vision (Soares et al. 2004).
In summary, lens transplantation indicates that cavefish have the capacity of form a complete eye and that they possess and are capable of using all the genetic factors necessary for later eye development.
. Thus far, the changes in gene expression patterns detected are either activations (e.g., hsp90) or subtle enhancements (e.g., shh) and reductions (e.g., pax6) in expression domains rather than loss of functions.”
The loss of sight in the cave fish was no adaption but a defect that left most of the sight mechanism intact.
The finding of Pax 6 in a variety of organisms demonstrates a common design.
You neither read nor understand what you post.
“The finding of Pax-6 from flatworms to humans suggests that eyeless is a universal master control gene and that the various types of eyes in the various animal phyla may have evolved from a single prototype... The wide variety of eyes in the animal kingdom may, therefore, have evolved from a single ancestral photosensitive organ...
Common descent? Ruh roh!;”
Impressive modular design.