Sure, evolution has already provided an ample number of ambulatory fish, but when has that ever stopped researchers from cooking something up in a lab. You know, for science!
Actually, biologist Renata Freitas and her colleagues at the Pablo de Olavide University in Seville, Spain, had a good reason for engineering the limbed zebrafish you see up there: they wanted to better understand the evolutionary process that brought life out of the oceans.
“Fossil data suggest that limbs evolved from fish fins by sequential elaboration of their distal endoskeleton, giving rise to the autopod close to the tetrapod origin.
This elaboration may have occurred by a simultaneous reduction of the distal ectodermal fold of fish fins. Modulation of 5′Hoxd gene transcription, through tetrapod-specific digit enhancers, has been suggested as a possible evolutionary mechanism involved in these morphological transformations.”
By adding extra hoxd13 genes to a zebrafish embryo’s fin (genes that control morphogenesis, or the process that dictates the shape of an organism), they caused it to overdevelop and expand, becoming something closer to a lobe. This is exactly what eventually allowed limbs to develop during the early natural evolutionary process.
Unfortunately (as far as I can gather), in this case the modifications were ultimately lethal. But they do point to the likelihood that a mutation of the hoxd13 gene caused the development of limbs in certain sea creatures, and therefore the arrival of life on land.