In corn snakes, there is a recessively inherited neurological condition called "Star Gazing". This page is dedicated to
the education of the corn hobbyist and breeder about this condition. Below are some frequently asked questions about Star
Gazing in corns answered with what we presently know about this condition.
Is Star Gazing recognizable at hatch?
Yes, absolutely. Although at rest it is difficult to detect, if you simply get the hatchling crawling about, the signs
are easy to spot.
What signs do Star Gazers show?
At rest, a Star Gazer may appear just as normal as any other hatchling. When stimulated to move about, they seem to have
difficulty with balance, swinging their heads to and fro as they slither. If agitated, they get more animated and swing their
heads faster, more wildly, and may even flip their heads over in a loop. As the name implies, Star Gazers may throw their
heads back and appear to gaze towards the stars at times. They may lay in odd positions with their heads upside down. Sometimes
they will get themselves flipped over and slither along on their backs for a time before righting themselves. The more intensely
focused on something they are, the more difficulty they have (such as when they're excited about eating, they may miss a strike
or swing their heads wildly.)
Mentally, these snakes are normal. They respond just as any hatchling would with excitement at feeding, gripping of your
hand as they crawl on you, and curiosity and exploring while "tongue sniffing". They can eat normally (albeit sometimes upside
down or in a weird position), they can shed normally. They don't appear to suffer any pain or discomfort and are perfectly
content to go about their daily duties, even if a bit wobbly.
Clinically, the condition is very similar to an animal that is bilaterally vestibular (meaning an animal that doesn't have
balance sensation from either side of its inner ear). Click here to view some video clips of Star Gazing hatchlings:
Star Gazers out actively exploring their nest box
Star Gazers excited after being moved into a deli cup
What causes Star Gazing?
At present, it is believed that Star Gazing is not an infectious disorder, but rather an inheritable one. Snakes are born
with the affliction and do not develop it over time or with exposure to Star Gazers. Star Gazing appears to be the result
of a simple recessive gene. The gene must be inherited from both parents for a hatchling to be affected. The gene does not
appear to be sex-linked (both males and females are affected equally) and does not appear to be linked to the Sunkissed gene
that it originated with (both Sunkisseds and non-Sunkisseds are affected equally).
The anatomical cause of the disorder at present is unknown, but research is underway to determine the result of the gene
on brain structure to see if we can identify the area of the brain that is affected and how it's affected.
What does "S-Factored" and "*S" mean?
Since Star Gazing is believed to be a simple recessive gene, we refer to the gene as the S-factor or *S for short. A snake
that is said to be S-factored is a snake that carries one copy of the Star Gazing gene. A snake that is possible S-factored
means that there is reason to believe the snake may be carrying the gene, but it is not 100% certain. Some things to remember
about inheritance of a recessive gene:
- If one parent is known to be S-factored, the hatchlings would then be known to be 50% possible S-factored.
- If both parents are known to carry *S or if a Star Gazer is produced in the clutch with a hatchling, that normal-appearing
hatchling is known to be 67% possible S-factored.
(1/4 of the clutch should be Gazers, 1/2 should be S-factored, and 1/4
should be clear of the gene. Since you can't tell *S clear hatchlings from S-factored hatchlings, until they are tested they
are 67% possible S-factored.)
Which corns are at the highest risk for carrying Star Gazing?
While Star Gazing has not been proven to be linked to any particular morph, it is seen most often in Sunkisseds and Sunkissed
descendants simply because the gene popped up in the original line of Sunkisseds. Since the gene can be passed on regardless
of the morph, any snake descended from these original carriers is possible S-factored. Unfortunately, with the way family
histories are lost and information lost in transactions, it is not possible to guarantee any corn is not a carrier without
either test crossing or having a full, accurate family pedigree showing no relation to Star Gazing carriers.
I have Sunkissed descendants in my collection, how do I test them for *S?
At present, there are two ways to positively identify carriers. The first is to have a clutch hatch out from unknown parents
with Star Gazers evident in the clutch. This would then identify both parents as S-factored. The second way is to cross an
unknown snake to a known S-factored animal (one that has produced Star Gazers). If no gazers are produced in a large set of
eggs, you can be reasonably sure the test cross animal is clear of Star Gazing. As a general guideline, to be 95% certain
the tester is clear, you need 11 healthy hatchlings with no Star Gazers. To be 99% certain, you need to produce 16.
I've bred my pair of Sunkisseds several times and never had a Star Gazer in the clutches,
this means they're clear, right?
Wrong. If only one of the Sunkisseds is S-factored, you'll never see a Star Gazer in the first generation, but all of those
babies would be 50% possible S-factored. Even in the second generation from this pairing, you only have a 25% chance of pairing
up two S-Factored hatchlings to see Star Gazers. You have a 50% chance of pairing up a non-carrier with an S-factored animal
and only a 25% chance of pairing 2 clean individuals. You can see how Star Gazing can "skip" multi generations only to pop
up down the line. This is especially troublesome when the first generation is an outcross and some of normal babies get wholesaled.
The gene is then silently spread into the general gene pool.
This information is
freely distributable courtesy of CCCorns.com and may be printed and used as a handout.