Dapple is the dachshund name for merle: a dominant gene that randomly dilutes patches of a dark base coat, leaving marbled lighter areas and often giving one or both eyes a blue segment. A single copy produces the classic dapple. It only shows on eumelanin, so a dapple red dog can be hard to spot.
Because it is dominant, a dapple always has at least one dapple parent. A dog that looks solid cannot secretly carry classic dapple — with one important exception discussed below, cryptic or "phantom" dapple, where the pattern is so minimal it is almost invisible.
Brindle and sable
Brindle lays vertical dark striping over the red (tan) areas of the coat. On a red dog it can be subtle; on the tan points of a black-and-tan dog it looks like tiger striping on the legs and face. It is caused by a variant at the K locus and is common and harmless.
Sable is trickier to define. In dachshunds it usually describes a red coat where individual hairs are tipped with black, giving a dark overlay along the back and ears that can fade with age. It carries no health concerns.
Piebald
Piebald is a recessive white-spotting pattern: symmetrical white on the chest, feet, tail tip and often a blaze or full white collar, over any base colour. Both parents must carry it. Unlike double dapple, piebald white is not associated with the eye and ear defects that come from a doubled merle gene.
That said, heavily white-headed piebalds can occasionally have reduced pigment around the ears; responsible breeders avoid pairing piebald with dapple so the two white-producing mechanisms never stack.
