Unveiling the Variety of Axolotl Appearances for Astonished Breeding Enthusiasts
In the vibrant underwater world of the axolotl, a fascinating array of morphs has emerged, each boasting a unique and captivating colour palette. These variations are primarily due to mutations in a set of four pigmentation genes, which produce distinct colour variants [1].
One of the most intriguing morphs is the white albino axolotl, characterized by its pale pink hues and red eyes, setting it apart from the leucistic variety due to the addition of the albino gene [2]. Unlike the golden albinos, it lacks the golden tint, presenting a paler appearance.
Another rare morph is the copper axolotl, known for its muted brown colouration, featuring light-coloured skin and subtle coppery tones, often described as pinkish or tan [3].
The piebald axolotl, with its dark patches primarily on the back and head, offers a strong contrast between black and white, giving it a spotted or marbled look [4].
Axolotls have also been genetically modified to glow a bright green colour under UV light, creating the GFP axolotl [5]. Meanwhile, mosaic axolotls exhibit patches of pigment from different morphs due to multiple genetic lines.
Firefly axolotls are a chimera variant, with glowing GFP tails attached to non-GFP bodies or vice versa, adding a surreal element to these aquatic creatures [6].
Enigma axolotls, while rare and not fully understood, start out completely black and later develop gray and white colouring with patches of iridescent gold [7].
Axanthic axolotls, lacking yellow pigments, present a gray or dark appearance [1]. The wild type axolotl, resembling its natural, lake-dwelling ancestors, features a dark gray to black body, a speckled appearance, and dark purple gills, making it the most common among wild populations [8].
Lavender axolotls exhibit a soft purplish-gray hue, while melanoid axolotls are completely dark, with no shiny gold ring or iridescence, due to the absence of iridophores [1]. Leucistic axolotls have pale pink skin, black eyes, and a light pink hue, and unlike albinos, they still have some pigment [1].
The golden albino axolotl features a light tan colour with yellow pigments and golden flecks, with translucent skin, no melanin, and its eyes are red due to the recessive albino gene [2].
Black axolotls are melanistic, caused by a genetic mutation leading to excess dark pigmentation throughout the body, including black or slightly purple external gill filaments and black eyes [2].
The largest completed axolotl genome (32 billion base pairs) published in 2018 revealed the genetic basis for these pigmentation traits among other species-specific genes [1]. Despite its massive size compared to the human genome, it encodes a similar number of proteins, and the pigmentation differences arise from mutations in a handful of pigmentation genes that affect melanin, iridophores, and xanthophores pigment cells [1].
In captive breeding, over 30 axolotl morphs have been identified, many through selective breeding of these mutant alleles causing varying degrees of pigmentation loss or changes [3][4]. These colour morph variations rarely occur in the wild, as natural axolotls are mostly dark gray or greenish [1].
Sources: [1] Axolotl.org.uk (2021) Axolotl Morphs. [Online] Available at: https://www.axolotl.org.uk/axolotl-morphs/ [2] National Geographic (2019) Axolotls: The Underwater Pokémon. [Online] Available at: https://www.nationalgeographic.com/animals/article/axolotls-the-underwater-pokemon [3] Axolotl Central (n.d.) Axolotl Morphs. [Online] Available at: https://axolotlcentral.com/axolotl-morphs/ [4] Axolotl News (2018) Axolotl Morphs: A Comprehensive Guide. [Online] Available at: https://axolotlnews.com/axolotl-morphs-a-comprehensive-guide/ [5] Genetic Modification of Axolotls. [Online] Available at: https://www.sciencedirect.com/topics/neuroscience/genetic-modification-of-axolotls [6] The Conversation (2019) Axolotls are being genetically engineered to glow in the dark. [Online] Available at: https://theconversation.com/axolotls-are-being-genetically-engineered-to-glow-in-the-dark-121962 [7] Science Alert (2019) Mysterious 'Enigma' Axolotls Have Been Discovered: Here's What We Know About Them. [Online] Available at: https://www.sciencealert.com/mysterious-enigma-axolotls-have-been-discovered-heres-what-we-know-about-them [8] Axolotl.org.uk (2021) Wild Type Axolotl. [Online] Available at: https://www.axolotl.org.uk/wild-type-axolotl/
technology might play a role in identifying the genetic basis of various axolotl morphs, potentially leading to advancements in biology and home-and-garden pets. Understanding the unique colors and patterns of different axolotl morphs, such as the enigma axolotl, could provide insights into the genetic modifications that govern pet lifestyle as well.
