A headspot or star is a white mark on a rat's forehead, usually located in the middle of the forehead between ears and eyes. Shape can vary greatly, from triangular, irregular, or round. This marking is never seen on a self rat - only on rats with other markings on the body, the more marking, the more likely to have a headspot.
Facial markings are believed to be the result of a modifier on the Hooded (H) locus, but are not genetically described. There are believed to be multiple genes controlling these markings. Some are the result of white-spotting genes and may lead to an increased chance for megacolon, therefore they should only be bred from known lines, and with care..
AFRMA
Allows headspots in the following standard markings: Essex and Varigated.
RSA
Allows headspots in the following standard markings: Berkshire and Varigated.
URS
"White marking to be small but clear and distinct placed as centrally as possible between the rat's ears and eyes on the top of the face. To be allowable in combination with the following standard markings: Berkshire and Varigated."
Blue Varigated with Headspot (c) Gabriel Edson