T positive stands for tyrosinase positive albino. Tyrosinase is an enzyme that catalyses the first two steps in the synthesis of melanin, the black pigment.

A tyrosinase negative albino boa lacks melanin because its tyrosinase does not work at all. Ideally, as in the black rat snake, a tyrosinase positive albino lacks all melanin for some reason having nothing to do with tyrosinase.

There are tests that can tell whether tyrosinase works, but nobody has run any on either the Sharp or Kahl albino. So there is no tyrosinase negative boa constrictor known for sure.

Boa keepers define a tyrosinase positive albino loosely, as a snake with a mutant gene that makes the snake produce less melanin pigment than a normal boa. It is a catch-all term. At least two mutants are named tyrosinase positive albinos. Depending on how loosely you want to use it, the term be used for half a dozen other mutants that have unrelated biochemical actions.

Paul Hollander

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