I have heard of some experiements where animals have their DNA adjusted to make parts of their bodies glow. The first one I heard about is the glow fish that are now sold commercially now. People do complain about the ethics behind glofish, but they do live full lives, don't have anything toxic in their system, and answered some questions about gene expression and genetransport
(Sorry if the first site is excessively biased towards glowing fish. this one is more objective
and focuses more on the laws involved. ^_^;). The fish were healthy and safe enough for any aquarium so a commercial market formed without endangering people or the enviornment. The GloFish
article on Wiki is another place to see what a responsible researcher has to deal with to introduce a modified animal into a commercial market for the sake of profit.
I say all this for a reason. GloFish I will defend because they are nothing more than healthy Zebra fish that happen to glow for the sake of medical science (and now profit). Fish tattooes and Fish dying is nothing more than torture or really, really slow murder for the sake of profit in that order. How on Earth is either legal? I condone humane animal testing in a controlled enviornment for the sake of medical breakthroughs and I still see this as nothing more than animal abuse. :(