IDENTIFYING ARCTIC
Heterozygous Arctic
Arctic is an incomplete dominant gene that causes axanthism and pattern reduction in western hognose snakes (Heterodon nasicus). This trait was discovered by JMG Reptiles in the 2000s according to Morphpedia.
This gene in heterozygous form is notoriously subtle and difficult to identify; however, the dramatic contrast of the homozygous/super form makes the identification worth the trouble.
As a neonate, arctic animals tend to have a darkened overall coloration with reduced contrast and slight axanthism. The pattern lightens and increases in contrast with age. Arctic also causes reduction in overall pattern, creating smaller saddles and headstamp. This is also called “cleaning up” the pattern. These markings also have inner-blushing outlined in black, which is then bordered in white. The black and white change according to other color-changing genes such as albino.
The background color is also covered in dark speckles, especially notable within and just ventral to the headstamp.
Arctic male western hognose produced and photographed by JMGReptile.
Note the blushing within the headstamp, black outline, and white border. Dark speckling on the background pattern can also be seen on the head and ventral to the headstamp.
The dark outline and speckling can also be seen throughout the body.
Homozygous Arctic
Homozygous, or super arctic, animals show the same traits as the single-gene trait but amplified.
As a neonate, arctic animals tend to have an intensely darkened overall coloration with reduced contrast and axanthism. The pattern lightens and increases in contrast dramatically with age. Super arctic shows intense reduction and in overall pattern, creating smaller and more defined saddles and headstamp with intense contrast. The dark speckling is also intensified.
Super arctic male western hognose neonate produced and photographed by JMGReptile.
Super arctic male western hognose produced and photographed by JMGReptile.
Arctic with Anaconda
Based on my observations of my own collection and old threads on the internet, it seems as though anaconda interacts with arctic in a way that is helpful for identification. Arctic anaconda snakes tend to have light pixellation near their vent, especially in higher-expression anacondas and supercondas.
Boba Tea, an anaconda arctic axanthic male western hognose photographed by The Vivarium. Note the broken black outlines an speckling throughout his body as well as intense blushing in the flags of his head stamp.
Boba Tea’s tail shows that arctic-pixelation isn’t a hard-and-fast rule, but a guideline. Don’t disregard other obvious signs of arctic if you see them, especially in lower-expression anacondas.
Two neonate western hognose snakes from anaconda arctic axanthic (Boba Tea) x albino anaconda (Orange Juice) pairing. Top, superconda; bottom, arctic superconda. Produced and photographed by The Vivarium.
A ventral view of the superconda neonate. Note the solid black color with no pixelation near the vent.
A ventral view of the arctic superconda neonate. Note the pixelation just below the vent dissolving the solid black belly to the background color. This could be interpreted as a sign of pattern reduction.
More Examples
Superconda het snow male western hognose (Alpha) from an anaconda arctic axanthic (Boba Tea) x albino anaconda (Orange Juice) pairing, produced and photographed by The Vivarium. Note that there is some pixelation near the vent but not nearly as much as his sister on the right.
Arctic superconda het snow female western hognose (Epsilon) from an anaconda arctic axanthic (Boba Tea) x albino anaconda (Orange Juice) pairing, produced and photographed by The Vivarium. Note the extensive pixelation near the vent as well as lower overall saturation and white borders around her headstamp.
Anaconda hypo male western hognose (Whiskey) photographed by The Vivarium. His pairing is unknown.
Ventral view of Whiskey showing the pixelation common with anaconda arctic animals. Traits that cause albinism (including T+ varieties like hypo) make arctic more difficult to identify, so this could be a helpful marker. It will be interesting to see if he proves to be arctic when paired.
Watermelon axanthic female western hognose (Cactus Juice) produced by Tom Bailey Reptiles from an axanthic x axanthic pairing, photographed by The Vivarium. The watermelon line is known for its tendency to produce dark neonates that lighten as they age. Without knowing this, she shows some signs of being arctic including intense black and white borders.
Ventral view of Cactus juice showing no arctic-pixelation near the vent. Based on our observations, arctic doesn’t usually cause this pixelation in animals without the anaconda trait.
Sable pos arctic female western hognose (Lapsang Souchong) produced by Hognose1.com from a het sable het axanthic x arctic het sable het axanthic het pistachio, photographed by The Vivarium. Lapsang Souchong is only possibly arctic and shows few signs; however, the trait can be hard to identify with sable. This is another potential example of how arctic-pixelation does not show in animals without the anaconda trait.
Anaconda het swiss chocolate pos arctic male produced by JMG Reptile from swiss chocolate anaconda arctic x het axanthic 50% het lavender. He shows some signs of having the arctic trait, including pattern reduction, speckling, and ventral pixelation, but needs to be confirmed.
Anaconda het swiss chocolate female produced by JMG Reptile from swiss chocolate anaconda arctic x het axanthic 50% het lavender. She does not possess ventral pixelation like her brother and doesn’t show any other signs of having the arctic trait.
GLOSSARY
Allele: a variation of a gene
Axanthism: a mutation that interferes with an animal's ability to produce yellow pigment, often resulting in lowering the saturation of the color in an animal
Gene: a sequence of DNA that codes of a phenotype, or observable trait
Homozygous: having two copies of an allele
Heterozygous: having one copy of an allele
Phenotype: the set of observable characteristics resulting from the interaction of its genotype with the environment
Genotype: what alleles an animal has
Incomplete dominant: both alleles of a gene are partially expressed, often resulting in an intermediate, blended phenotype
Saturation: the intensity of color. For example, a black-and-white movie and low to no saturation. A bright red rose has high saturation.
Contrast: the difference in brightness and/or color between different parts of a pattern