The most well supported theory I have heard, is that the difference between the Japanese harlequin breed and the brindled harlequins we regularly see in rex (and some other breeds) is the presence of the dutch gene, du.
The broken gene, En, is known to cause the harlequin pattern to bunch up into spots. Which is why rex tris look more "correct."
The dutch (and possibly vienna) genes may help it separate into checker pattern, or at least, more intensely colored patches.
That would make the du gene and suppression modifiers(or their lack) the cause of the white foot or white markings that have, to date, never been bred out of japanese harlequins.
Ideal japs may have a Dudu genotype, with enough suppression modifiers to make the white completely invisible.
Breeding two Dudu rabbits together will always produce some DuDu(no dutch genes, brindled), Dudu (one copy, which may or may not be visible on the coat, and dudu (likely to have visible white.)
Supporting facts:
From the American harlequin rabbit club website:
It appeared accidentally in the Belleville or Montmartre suburbs of Paris, and is obviously descended from Brabancon or Dutch..
http://americanharlequinrabbitclub.weeb ... story.html
I have heard experienced harlequin breeders refer to the white in Japanese harlequins as "dutch-like white marks, or describe them as "appearing in all the same places that dutch marks will."
Finally, it's pretty well known that that breeding two well-marked harlequins together still tends to produce very mixed results, and that breeding poorly marked animals can still throw something great (with a lot of luck, and the right genes
)
The du theory also helps explain why brindled rabbits are still regularly born to the harlequin breed, even to nicely marked parents.
I believe that most harlequin rex lines simply do not to have the dutch gene, which is very good thing for rex in general! The last thing rex breeders need to worry about is random dutch marks cropping up in other colors.
The consequence is that harli rex are more brindled than Japanese harlequins, but, that is OK, since harlequin is not showable in rex anyway, and brindled harlequins still make for just fine tris.
Now that I think about it, perhaps not having dutch genes to contend with can actually help improve tri spotting?? :? This needs looked into...
The vienna gene may cause a similar effect to dutch (I'm basing this on pics I've seen online, so it's
pure speculation), but, that may explain why nicely marked harlequin lops seem to be a bit more common.
The burnt ginger part is just rufus modifiers.
My own japs are very washed out (burnt ginger, or even pale ginger) due to breeding with low rufous magpies. It's OK for me, since my japs are just working towards all the recessives I need to get a 100% magpie herd.
If you want nicer red color in harlequin rex, you can improve a line with high rufous castors, or good red rex.
