Pattern Formation

The following chapter describes a model for pattern formation. This model is only hypothetical and may or may not be an exact description of the true process. It is based on the way patterns are formed in other vertebrates (fish, lizards, birds, and mammals) and should serve as a good tool to visualize and understand how cornsnake patterns come to be.

The "Neural Crest Migration" Model:

In early development of embryos, one group of cells, known as the neural crest, differentiates itself. This group of cells eventually becomes the nervous system, brain, spinal cord, eyes, and the pigment cells on the skin. Since the pigment cells are closely related to the cells forming the nervous system, this could explain why many defects in skin pigment (in mice, dogs, cats, and horses, and humans, for example) are often accompanied by neurological defects such as blindness, deafness, megacolon, "lethal whites," etc.

The pattern in cornsnakes appears to be made of four different types of cells, one produces the saddle color, one produces the border color, one produces the ground color, and the last type only produces iridophores, which creates the white areas. Areas where no iridophores and no pigments are produced end up being a pinkish flesh color. When these cells divide, the resulting daughter cells have the same "destiny" as the original cell and will produce the same pigment.

cells aligned along the spine

Illustration 1 - cells moving from head to tail along the spine, with subgroups beginning to form.

Back Page 34 Next