Zebrafish their larval stages. In 2011, the British Heart Foundation ran an advertising campaign publicising its intention to study the applicability of this ability to humans, stating that it aimed to raise £50 million in research funding. Zebrafish have also been found to regenerate photoreceptor cells and retinal neurons following injury, which has been shown to be mediated by the dedifferentiation and proliferation of Müller glia. Researchers frequently amputate the dorsal and ventral tail fins and analyze their regrowth to test for mutations. It has been found that histone demethylation occurs at the site of the amputation, switching the zebrafish's cells
Sargassum fish and brown on a paler background, and the fins often have several dark streaks or bands. The fish can change colour rapidly, from light to dark and back again. The body and the fins are covered with many weed-like protrusions, but other than these, the skin is smooth without dermal spines. The dorsal fin has three spines and 11–13 soft rays. The front spine is modified into a slender growth on the upper lip known as an illicium, which is tipped by a fleshy lump, the esca. The junction between the head and body is indistinct because no gill slits