5/5/2022: The disappointing outcome of piebald Oniscus asellus
Oniscus asellus “Mardi Gras Dalmatian” is an… interesting strain. From discussion with the creator, the line is allowed to contain some wild types, dalmatians of varying yellow expression, and intriguingly… piebalds. A few have tried to isolate the piebalds from the line in the last few years, but the projects never really seem to gain traction for miscellaneous reasons. Upon acquiring some of these pied individuals, I set out to see if I could get them going. A year later and the answer is a resounding no, but there’s much more to say here.
I started the trial colony with about 7 individuals, all picked at a young age when the trait was visible but too small for reproduction with other members of the “Mardis Gras Dalmatian” stock they came from. I put them into an ideal set-up that had produced copious Oniscus asellus prior, and waited. Days passed, then weeks, then months… no offspring despite all the individuals gaining size and both sexes being present… until one day, a handful of babies popped up. I waited some more, eager to see if/when more would appear and how quickly I could prove the trait… and yet, these babies matured to wild type adults. This was mind-boggling… How could what was near textbook for a simple recessive trait not prove out under these conditions?
Odder still, the 3 or so babies produced were the only offspring that ever came out of the adults. To this day, no more offspring have been produced, though the progeny are now all mature.
After some literature perusing and idea bouncing off some other keepers, I discovered a potential framework to explain the phenomenon.
Genetic chimerism is a phenomenon where some of an individual organism’s cells have completely different DNA. This can be due to zygote fusion before birth/hatching, mutations in somatic cells, or induced by pathogens acting as a vector between cells. The piebald asellus in “Mardi Gras Dalmatian” appear to be chimeras, and with the high incidence in the line that suggests there is a genetic susceptibility to induced chimerism OR a recurring pathogen causing it considering the induced phenotype is not heritable.
How do the miracle wild type babies work into this scenario? Simply, the gonads of one pair of the piebald individuals were functional enough to produce compatible sperm and eggs, and almost certainly those gonads/enough of those gonads were of the functional, wild-type within the piebald individuals. In a very oversimplified way, think of it like having a tapeworm inside of you; it’s a different organism with its own genetics and when it reproduces, despite being entirely reliant on your body for its reproduction, the resulting progeny are tapeworms and not humans. Now, extrapolate that to these wild type gonads (or even just part of the gonads) nestled within a mosaic of wild type and piebald cells/organs, and you have a feasible explanation for the phenomenon. It stands to reason that the non-wild type reproductive bits of the isopods are infertile, considering no piebald offspring were produced.
Working off of this, we can see the importance of line tracking when selecting for various traits. An eager enthusiast may find piebalds in their Oniscus asellus which have “Mardi Gras Dalmatian” influence, only to waste many years trying to isolate a phenotype that is not heritable in that context. This scenario does not disprove the heritability of piebald in ALL Oniscus asellus strains as there are sure genetic piebalds out there, but it does close the book on this PARTICULAR piebalding in this strain and any derivatives intentional or otherwise. Perhaps with sheer numbers and time, a stable phenotype could be worked out of this line… but then again, a billion monkeys slamming on a billion typewriters could also eventually produce the works of Shakespeare.
-Kyle