Professional Herpetoculture for the Pet Trade

Cornsnake Pattern Mutations

Most pattern mutations in the Cornsnake are simple traits, inherited in typical Mendelian recessive fashion. In at least two cases, the traits are allelic (residing at the same locus). Another appears to be the first documented dominant trait in Cornsnakes, and yet another stems from a combination of selected appearance and a recessive trait or traits. Combining pattern mutations with color mutations can lead to some exceptional looking specimens indeed. Since pattern mutations essentially affect the distribution of the pigments, many specimens appear much brighter or cleaner than typically patterned individuals of the same color morph.

Motley

This, the first recessive pattern trait discovered in Cornsnakes, is also one of the most complex. The mechanisms involved in the redistribution of pattern are not understood at all. However, a few plausible theories have been postulated. The motley pattern affects the entire animal. Belly patterning is completely absent. In most examples there is a complete dark line along the edge of the ventral scales, matching in coloration what one would suppose the ventral checkering to be. The supposition is that the ventral patterning has been aligned along the edges of the ventral scales. Lateral pattern is either absent or has been reduced to faint irregular striping along the lower sides. The dorsal pattern may consist of either widely spaced elongated blotches, often fused at the sides to form a ladder pattern, or nearly full-length parallel stripes. Extremely variable, leading to several named variations such as Q-Tipped, Pin-Striped, and Hurricane.

It is known that the motley and stripe allele share the same locus, yet the Motley appearance is dominant to that of Striped. Thus specimens with two motley alleles appear motley patterned, those with two striped alleles appear striped and those with one of each allele appear Motley, but are heterozygous for Stripe.

Striped

Two nearly perfect full-length dark stripes surround a full-length light mid-dorsal stripe. Lateral pattern is largely reduced to fain irregular stripes or elongated blotches. Often the pattern of stripes is broken near the vent and onto the tail. As in the motley pattern variant, ventral pattern is absent. Consistency of striping is extremely variable, with some specimens appearing more blotched than striped. This has led to a variety of named appearances - none of which seem to breed true in a consistent fashion. Among these are Cubed, Patternless and Vanishing Stripe.

It is known that the motley and stripe allele share the same locus, yet the Motley appearance is dominant to that of Striped. Thus specimens with two motley alleles appear motley patterned, those with two striped alleles appear striped and those with one of each allele appear Motley, but are heterozygous for Stripe.

Zigzag or Zipper

Appears to be caused by a longitudinal misalignment of the two (left and right) halves of the dorsal pattern blotches. The result erratic combinations often form a broken pattern resembling a thick wavy line down the dorsum. A Zigzag or Zipper, if you will. Although the trait is a simple recessive, specimens which are known homozygous for the trait occasionally fail to exhibit it visually. In actuality, it just happens that the misalignment of the two may be re-aligned by chance - and the result appears completely normal to our eyes. Most examples of this mutation have areas which appear completely normal due to this. Recently, breeders have concentrated on this trait and have 'enhanced' it into more and more severe pattern deformations. As they are stabilized genetically, many are given new trade names. Aztec is one we hear a lot.

Plain-Belly

A total lack of ventral pattern is found in another cornsnake color mutation. Examples of the 'Blood-Red' morph lack all traces of ventral patterns. It has been demonstrated that this trait is inherited separately from the rest of the Blood-Red traits, and can be passed to other color mutations. It has also been conclusively demonstrated that it is genetically distinct from the lack of ventral pattern exhibited by motley and striped cornsnakes. Unlike those two pattern morphs, there is no tendency for dark striping along the edges of the ventral scales, indicting a change in distribution of ventral pigments. Rather, all pigmentation is simply missing.

Bloodred (Diffuse)

I approach this subject with a little trepidation, as I'm sure there are those out there who will disagree - but here goes the conclusions I've drawn over the last couple decades. Examples of the 'Blood-Red' morph lack all traces of ventral patterns and also have greatly reduced to completely absent lateral blotches. Additionally, many will have either absent or greatly reduced and malformed head patterns. With growth, the 'best' of them will become suffused with red pigment throughout, eventually achieving a near solid red appearance. Obviously, this does not happen in specimens lacking red pigmentation, such as anerythristic or charcoal.

It has been demonstrated that the plain-belly trait, the head trait, the blurring of side patterning, and the red suffusion trait may in fact all be inherited separately. The trade name Diffuse had already been put in use for specimens exhibiting the blurred side patterns and plain belly traits, which so often are passed together in recessive fashion (almost as if they were one).

In truth, Blood-Red corns must be viewed as a polygenic morph, comprised (I think) of the following alleles:

  • Plain-Belly (evidently a codominant allele, as many 'hets' exhibit an 'intermediate' or modified belly pattern. Possibly trait-linked to Diffuse side patterning)
  • Diffuse (herein referring to the blurred side patterns only, although in common use 'Diffuse Corns' includes plain-belly as well, other breeders have begun using the term interchangeably with Blood-Red, tossing a turd in the churn for those trying to sort this mess out. Possibly trait-linked to Plain-Belly)
  • Faded Head (appears to be a typical recessive)
  • Suffusion (herein used to describe the extensive development of red pigmentation through the body. Appears to be inherited as a recessive, but is clearly improved upon through the process of selective breeding. Obviously this one is not very apparent in mutations not exhibiting red pigmentation)


The concept of true Blood-Red corns being a polygenic morph, in part heavily influenced by selective breeding, really should come as no surprise to any reader familiar with their history. This morph was not created from a single mutated snake, but was instead slowly developed over a long period of time by a breeder living in Florida, who had easy access to large numbers of Cornsnakes. Logically, any corn exhibiting a possibly useful appearance was incorporated into the breeding program, until the 'Blood-Red' corn was born.

This process continues today, although the waters have been muddied by the sale of many poorly marked specimens as true Blood-Reds, hence a lot of confusion exists with regard to what actually constitutes a good one. But us old-timers who had access to the early Blood-Reds, before they were genetically 'thinned out' by outcrosses to other mutations, can attest to the fact that most of today's 'Blood-Reds' are pretty poor examples.

Banded

The genetic origins of this trait are unclear, and it may in fact be a simple variant of the motley trait. However, it is distinct enough in appearance to be discussed here. The dorsal blotches are simply expanded down onto the lateral regions to give the appearance of a banded snake, rather than blotched. The best specimens also appear to lack the intermediate lateral markings. As this trait is fairly new to the scene, it remains to be seen where it will lead.

Frosted

Appears to be a pattern trait in which pigmentation is concentrated at the center of each scale, producing a pale speckled look. Has been crossed to several color mutations. This trait can be seen to a degree in many Cornsnakes, but specimens which have been selected for this tendency are very unique in appearance. Here's another relatively new genetic trait for breeders to explore.

Tessera

This startling pattern mutation creates a snake with a very thin but strong and dark-edged mid-dorsal stripe, often the full length of body and tail. The side pattern is broken up into large numbers of densely jumbled 'squarish' blocks. Many folks have mistaken them for garter snakes upon first sight, with the realization they are actually Cornsnakes slowly dawning on them after a few moments.

The first known dominant mutation in Cornsnakes, with all adult specimens proven heterozygous for this allele!When bred to a completely normal Cornsnake, a Tessera will produce a clutch of half Tesseras and half completely normal babies. Tessera to Tessera breedings have thus far produced only what appear to be  Tesseras and completely normal Cornsnakes. Such clutches have also resulted in a moderate egg failure rate, which leads one to the conclusion that the Tessera allele may be lethal in the homozygous state, a situation well known in other species such as Merle dogs. A large number of Tesseras from such clutches will need to be grown up and test bred to confirm or deny whether homozygous specimens may simply be identical to heterozygous.

Terrazo

A recessive mutation which could best be described as a combination of patternless and the most extreme thin-banded zig-zagging imaginable. In truth, this one can't be described in words.... goggle up a picture, we don't own any yet so you'll have to look elsewhere.

Wide-Stripe

A very new cornsnake pattern variation, not yet fully understood. It appears as a very wide mid-dorsal stripe, with slight wavy edges. Side patterns tend to be reduced to thin vertical bars on many specimens. Mode of inheritance is uncertain at this point, but our limited breeding results indicate this is may be a dominant mutation. Thus far, all of our breedings between two wide-stripes have yielded 100% wide-stripes. Breedings between wide-stripes and unrelated anery and snow specimens have also yielded 100% wide-stripes. Currently very few specimens exist.

Piebald

Generally termed 'Calico' in the trade, although there may in fact be two or more mutations present in captive collections which fall under this label. The first discovered incidence of piebaldism involves animals which develop varying amounts of white scattered patches during later years of life. These patches are associated with some form of cellular disruption appearing as blistered deformities of the scales. Breeders are currently attempting to see if this negative trait can be separated from the 'desirable' one.

A few recent hatchlings have appeared to be true piebald specimens, in which large areas are devoid of pigment at birth. Future breeding projects will determine if this trait is genetically inheritable or simply a developmental anomaly. The parallel trait in the Ball Python (Python regius) was proven inheritable in the summer of 1999...