It's the hardest part of the day for pet owners. Watching your dog or cat mournfully look up at you with those big eyes as you walk out the door to go to work. And the worst part? You won't be coming back for another eight hours. All sorts of terrible things could be happening to Fluffy while you're gone, and you would have no clue.

Thestriped zebrafish is a popular pet, not uncommon in aquariums. But it may have a lot more in common with pet owners than you might guess by looking at it—humans actually share 70 percent of our genes with the little swimmers. This is cool for many reasons; for one, the zebrafish can repair its own heart, and the commonalities have made it a focus of medical research. And now, in this week's Proceedings of the National Academy of Sciences, researchershave identified the receptor for the particularly putrid aroma of cadaverine, also known as rotting flesh.

Yes. Many pet owners have seen their sleeping dog or cat twitch or paw the air, as if dreaming of bones to bury or mice to chase. Stanley Coren, a psychology professor at the University of British Columbia in the US, and author of the book The Intelligence of Dogs, says that canines go through the same sleep stages as we do, only faster.