What are the mechanisms underlying leucism--genetic and epigenetic or other? Is there agreement on its definition?
I found two larvae of a Himalayan Troidine butterfly (Byasa dasarada) which were leucistic. Interestingly, one was in the final instar, the second in the penultimate instar. When brought down more than half a kilometer in altitude (from the forest where they were found to my home, i.e. about from 2200 m to 1500m elevation, where it was warmer), the final instar larva pupated and yielded a normal butterfly; the penultimate instar larva, however, reverted to the normal coloration of the species in the final instar and pupated. Both yielded normal adults. So, perhaps there is sometimes a genetic basis to the phenomenon, in this case, perhaps triggered by climate?
In "himalayan" rabbits and mice, there is effect of temperature on pigment production. In lower temperature the production is activated.
The effect of temperature on tyrosinase activity in Himalayan mouse skin, S. H. Kidson, B. C. Fabian 1981, DOI: 10.1002/jez.1402150111
thanks..and does that mean that when coats are shed, a Himalyan colored animal can change its degree of pigmentation?
Anne, probably yes if the temperature changes. I found such paper: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1209709/pdf/90.pdf I didn;t study it closely but I think there was demonstrated some change in coat colour.
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