No, it's a possum dalmation. Merling is a much darker color and is associated with minks. He looks russian blue, because when put with a black rat, they produced blacks and RBs.

"safe" patterns include berkshires, hoodeds, pink-eyed white/Albino, siamese/himalayan, self, irish/english-irish, variegated/variberk. No blazes/wedge-blazes, no merling, no dalmation spots, no capped/split-capped, no possum, etc.

I, personally, would like megacolon to go away, but until people aren't breeding high risk pet store rats and selling them to be put into general population(other pet stores or friends), then it will still be very prevalent. Even chain pet stores aren't good sources for future breeders. I picked up a 4-5 week old american blue wedge-blazed baby female from Petsmart a few months back. After a day in my care, the bloating and awful diarrhea started. She was placed in a friend's care for quarantine, and within the week was euthanized by her vet. That's why I would never breed a marked rat from a pet store, as you never know what genes they are carrying, and when bred with another rat that carries those genes, you'll get alot of devastation.