Back in 1995, I started asking people what the differences were between ranchu and lionhead goldfish. I got some concrete stuff and also some pretty nebulous stuff. Things like "ranchu live longer and swim more elegantly". Looking at pictures, I thought I could see some obvious differences. But I also found pictures where I though the caption was wrong.
A conversation with Jackie Chan in August of 1996 cleared some of this up. Jackie is a major goldfish breeder and exporter in Hong Kong. I commented to him that I thought many of the lionheads I had seen in recent books looked a lot like ranchu. He told me that the popularity of the ranchu had created a market interest in lionheads with "improved" tails and backs. That is, more similar to the ranchu. Previously these had been largely ignored features in the lionheads they were breeding.
I also have a suspicion that I haven't confirmed with anyone that some of the more recent colors in ranchu (like black or blue) may have been introduced through crosses with lionheads. The side effect here is that the ranchu have shallower backs than normal, bigger tails, and more headgrowth. The book "Goldfish in Hong Kong" shows examples of both the ranchu-like lionheads and the lionhead-like ranchu. Confronted with one of these fish, I would be unable to say which breed it was.
Traditionally, however, there are distinct differences beween these two breeds:
Historically, the ranchu has been known in Japan since the 1700's and the first competitive ranchu exhibition was in 1885. The lionhead is about 300 years older and most authors have assumed that the ranchu was derived from the lionhead. Interestingly, in Dr. Smartt's new book on goldfish breeding and genetics, he argues that the ranchu and the lionhead are the same fish. Dr. Smartt backs this up with the observation that you can select fish with either set of varietal characteristics discussed above from any given single spawn of either variety. Not sure if I buy this.
The GFSA has been working on a set of judging guidelines that
include ranchu and lionheads. With the kind permission of the
GFSA, I reprint two of the illustrations below, to try to
reinforce the points made above.
Side view of a lionhead (© 1996 Goldfish Society of America. Reprinted with permission)
Side view of a ranchu (© 1996 Goldfish Society of America. Reprinted with permission)