This is a gold marble
pearlscale, but it's possible to breed pearlscale versions of any variety, although
it works best in varieties such as gold and platinum, where the reflective effect
of the scales is not masked by darker pigment.
Pearlscale is considered a recessive mutation which results in abnormal formation of the scales, this in turn produces a characteristic "ridge and furrow" appearance of the skin.
These ridge and furrows
catch the light and can cause the fish to "sparkle".
Although a deformity, this mutation does not seem to have any detrimental effect on fish in captivity. There are some reports of increased incidence of missing or deformed ventral fins in fish that carry this particular mutation, but it seems likely that this is not due to the pearlscale gene itself, but more likely due to excessive inbreeding.
fish are homozygous for the mutation and this is written as p/p.
Although considered recessive, it is sometimes possible to spot the effect of pearlscale in heterozygous condition, as seen in this blue ghost angel.
The effect is much easier to see in a photo than it is in the flesh, and has yet to be shown to be a reliable indicator of pearlscale in heterozygous condition.