It was the spring of 2007.

I was looking forward to a litter from my Tortie CPC, Donegals Irish Step Dancer (Stepper). She had been bred to my Himalayan Flame point male, CH Donegal's Irish Creme (Irish).

Since Stepper was a colorpoint carrier and Irish was a Himalayan, statistically I was expecting a litter where half the kittens would be pointed, while the other half would be solid or parti CPCs.

Although I have been breeding cats for more than a decade, nothing had prepared me for what I did get... because right from his birth, I knew there was something different about this kitten...

During the delivery, as his white head emerged from the birth canal, I thought, "Yea, a Himmy," because I wanted Himmies. As the queen continued his delivery,  I saw the black spot on the back of his head, not something found on a Himalayan at birth.

With astonishment, I said, "What are you?"

It would be some months before I had even an inkling of an answer to that question.

Growing Up The strange kitten looked more like a oppossum than a cat... and that's how he acquired his name. The photo on the right is Possum at 8 days old. His face appeared to be all white and it extended in a streak over the back of his neck.
His body was mostly a mingling of red and black - the typical coat pattern of a tortoiseshell Persian.
The most obvious change as Possum developed was his face and eye color. By seven weeks (photo at right), Possum's white face was showing faint red coloring, the typical beginnings of a flame point's red mask. His eye color developed from the blue of a newborn to the copper eye color of a non-pointed Persian.
By 6 months of age (photo right), Possum's coat continued to be a strange mixture of colors...
At 6 months, a close up of the color on the top of the head and ears shows the unexpected black spot I first noticed at his birth.

She's a He!

Since "she" looked mostly like a tortie, for the first four months of his life I assumed Possum was a girl - some sort of an aberration of a CPC tortie.

I asked several breeders, a CFA representative, and a judge what they thought "her" color was from my photos and I received a variety of answers... smoke tortie and white, calico, brown patched tabby and white. There were a lot of different opinions...

It was at that time that Royal Canin Pet Foods sent members of their breeder club a booklet written for breeders. There was a chapter on unusual color patterns, more specifically on male tortoiseshells and calicos. As soon as I read the chapter I realized that I had never checked Possum's sex. I had assumed because of the tortoiseshell pattern that she had to be female. That's when I discovered two testicles and a penis!

Possum's Color and Sex - and the Contradictions

Now officially a "male", Possum's colors included variations of "white", black, and red, appearing to resemble his flame point sire in the face and his tortie dam along the body, except where the "white" of the Himalayan body color mingled with the tortie pattern.

• Possum has the coloring of a flame point Himalayan on his head - a dominant color.
• What appears to be blue on the body is actually the "white" of the Himalayan body color intermingled with the Tortoiseshell black, giving it a dilute appearance.
• He has the coloring of a black and red tortoiseshell on his body, a sex-linked color, meaning he must have two of the female X chromosomes.
• He has male genitals, meaning he has at least one Y chromosome.
• Although Possum has pointed coloring on his head, his eye color is copper, not the blue eye color expected of a Himalayan.

Genetic Anomalies:

There are three genetic conditions that usually account for unexpected coat colorations in male cats:

• Klinefelter's Syndrome: A genetic condition where the male has an extra X chromosome (XXY). These are the male tortoiseshells and calicos. They are usually sterile.
• Mosaicism: A mosaic is an animal that has one set of DNA, but two (or more) groups of genetically distinct cells from the same zygote. In some of these cats only some of their cells have an extra X chromosome, but other cells have the normal XY genotype. If the cells of the reproductive system have the normal XY genotype, these cats will be fertile.
• Chimerism: A chimera is an animal that has two (or more) groups of genetically distinct cells that originated from different zygotes. Chimeras are formed when two fertilized eggs or embryos fuse together very early in the development process and grow as one individual. Each population of cells keeps its own characteristics and the resulting animal becomes a mixture of sometimes contradictory "parts".

What Is Possum?

Once I discovered Possum was a male, I realized my boy was probably a genetic anomaly. I emailed Lorraine Shelton, author of the chapter in the Royal Canin book and well-known feline geneticist, to ask her if my cat might fit into one of the three categories for the unusual male color patterns. Her response was that Possum was the best marked chimera she had ever seen.

Understanding Chimerism Think of a chimera as two jigsaw puzzles with all the same shaped pieces but of two different pictures. A single puzzle can be made out of a combination of pieces from both puzzles. The completed puzzle would have parts of each different picture. In the same way, a chimera is made up of two different sets of DNA from two different zygotes that merged into a single embryo.

Learning More

Since I have been doing all my cattery's genetic testing with UC Davis, it was logical that my next step was to get in touch with Dr. Leslie Lyons to see if she would like to do a genetic work up on Possum. When a swab of his cheek was DNA tested, it was determined that he had the genetic makeup of a Himalayan. As this is the part of him that looks like a Himalayan (is phenotypically expressed), this was not unexpected.

Blood, and possibly hair samples, should render more genetic information regarding the "fraternal tortoiseshell twin" part of him. The request for these tests are pending from  UC Davis.

DNA testing confirmed that Possum's Himalayan identity does not carry dilute. Of the two parents only the sire carries it. Lorraine believes he will breed like a flame point because the male genitalia is associated with his flame point Himalayan identity.

ANOTHER CHIMERA The Red, White & Blue Maine Coon Solkatz Pretty Boy Floid is a male Maine Coon chimera born in 1996 in Bremerton, Washington, USA. He displayed both dominant and dilute colors, appearing to have areas of red tabby, blue and white patches in his coat. He was fertile and sired many litters, over 30 kittens, always breeding and producing as if he were a red tabby.

Looking For Answers

After receiving the results from UC Davis, next my vet performed an ultrasound on Possum to see if he had a uterus in addition to his male reproductive system. The answer is no.

That leaves just one important question left to be answered - Is Possum fertile? Possum, now a year old, is showing typical male-type behavior, suggesting he is producing the male hormone, testosterone.

I took a urine sample in to be checked for sperm since some of the ejaculate spills over into the urine. Possum did have a few sperm present, but they were immotile. This could be due to the time lag between collection of the sample and the microscopic examination - or it could be the actual morphology of the sperm.

I will try to breed him to one of my girls, a Himalayan, so that we can (hopefully) prove that he is fertile if he produces kittens. By breeding him to a Himalayan, if he produces pointed kittens, this will prove he breeds as if he were a Himalayan.

Only time will tell :-)

Registration

I plan to register him with the CFA as an AOV male and will name him Donegal's Tail of Two Kitties. Look for Possum to appear in shows from time to time on exhibition. He is as sweet as he is both beautiful & unique... and Possum is, of course, remaining at Donegal Cattery.

Possum's Profession Photos

Possum's beautiful professional photos are by Vicki Longoria of Blue Bayou Feline Photography. They were taken at one year of age. You can see what he looks like as he approaches adulthood...

With Thanks

I'd like to express my thanks to the many people helping me determine and document the genetics that have produced such a unique kitten as Possum, especially:

• Lorraine Shelton, Featherland
• Dr. Leslie Lyons, UC Davis
• Rosemarie Williams, DVM, The Sound Cat Veterinary Hospital
• Vicki Longoria of Blue Bayou Feline Photography