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Problem of micro animals in Campbells platinum/black-eyed white (BEW) breeding

Author: Bill Greig

From Issue 34 Jul 2000

The following picture shows 3 animals from the same litter at the age of 6 weeks and exemplifies a problem that I have in breeding platinum and black-eyed white Campbell's Russian Dwarf hamsters. In the first litters that I bred from black-eyed whites with black-eyed whites, I found a number of these micro dwarfs.They were about the same size as the micro-ophthalmic toothless whites that arise from MiMi animals ( double dominant mottled) that tend to starve to death around the time of weaning. They also develop atypically with outsize heads, the bodies staying near birth size.(c.f. achondroplasia in humans).

But there the similarity ends

Admittedly there was a considerable prematurity death rate, but some matured at about 12 weeks and some have produced progeny. Most appear to be sterile, especially the females. Also, the platinum micros that appear died in early life, but not exclusively before weaning

Now what have we here?

The only academic evidence I could find is that, in common with a lot of aberrant genes (especially but not exclusively dominant aberrations), the gene that produces the platinum pattern is lethal in the double dose, SiSi. There seems to be an opinion that the gene responsible for producing the black-eyed white condition (I am not allowed to call it a colour) ameliorates or buffers the second Si gene and allows viability. Again I can find no definite naming of this gene, and so I claim the right to call it di with Di as the normal allele.

What I have seen in my own hamstery would lead me to think that SiSiDidi is a micro platinum whilst SiSididi is a micro BEW. If this is the case and assuming that Si and Di are not located on the same chromosome, we would find:

Parents: SisiDidi

Leading to (see punnet square)

• Lethal 2
• Platinum 6
• Micro platinum 1
• BEW 3
• Micro BEW 1
• Normal 3

	Si Di	Si di	si Di	si di
Si Di	SiSiDiDi Lethal	SiSi Didi Micro Plat	Sisi DiDi Platinum	Sisi Didi Platinum
Si di	SiSi Didi Lethal	SiSi didi Micro BEW	Sisi Didi Platinum	Sisi didi BEW
si Di	Sisi DiDi Platinum	Sisi Didi Platinum	sisi DiDi Normal	sisi Didi Normal
si di	Sisi Didi Platinum	Sisi didi BEW	sisi Didi Normal	sisi didi BEW

The production of micro BEWs when BEWs are crossed together points to the presence of Si genes in both parents leading to the 1 in 4 SiSididi. There is a possibility that there is a third recessive gene that produces the micro effect (dwarf-dwarf hamsters sounds gauche) and the whole hypothesis fails but evidence for this would need to be assembled.

This paper is part of a submission to the BHA Standards Committee that a standard be introduced for black-eyed white in Campbell's Russian Dwarf hamster.