The melanoid axolotl is a dark morph with no shiny pigment cells. The gene behind it is Ltk.[1]
Appearance
A melanoid has many black pigment cells and fewer yellow ones, and it has no iridophores, the shiny cells that give the wild colour its sparkle.[1]
Genetics
The gene Ltk, which codes for the leukocyte tyrosine kinase, was found by comparing RNA from melanoid and normal animals, and animals edited with CRISPR copied the dark colour. The authors say the evidence “strongly implicates” this gene. The morph is recessive.[1]
History
The morph turned up in the 1960s in crosses among the grandchildren of axolotls imported from Mexico, and it was described in 1967.[1] Whether melanoid axolotls still occur in Xochimilco is not known.[1]
Popularity
Melanoid is one of the four pigment mutants kept by the stock center, and it has received considerable attention in biological research.[2][3] All colour mutants known to research are also available in the pet trade.[3]