SJD descended from a full sibship (clutch) of Darjeeling
Wild Types that the Johnson lab genotyped. More information can be found at the Johnson lab website
. The analysis revealed that approximately 14 percent of the genome still had polymorphisms within the stock. Since then, the Johnson lab has been breeding these fish to retain that diversity and vigor.
SJD-subB: The Johnson lab also developed a subline of SJD that has been further inbred by full sib matings, called SJD-subB. They have not been analyzed to see if they are in fact more inbred, but they likely are. The Johnson lab assumes that only 5 percent of the genome in these fish still has polymorphisms. ZIRC maintains and distributes their descendants.
Both SJD and SJD-subB are still quite hardy, and shock breed naturally.