Hypo Boa Constrictors

The Hypo gene in boa constrictor removes black pigment from the pattern. This leaves a cleaner animal that has warmer background colour instead of the usual dark barring. Because it underpins some of the hobby's best-known combos like Sunglow, Ghost and Moonglow, many keepers know one of those names before they meet Hypo on its own.

Appearance

One copy makes the black pigment less intense. Because the dark margins that usually edge the pattern are faint or absent and the fine black flecks of melanin on a normal boa are missing, the tail shows the same reduction. The dark pigment around the red blotches on the lower body is thinned out, meaning it looks paler and cleaner than the tail of a normal boa. The animal looks warmer overall as more orange, tan and cream show through the pattern while darker browns and blacks give way to brighter background colour. Rather than a paler shade of the same thing, two copies give Super Hypo, which is a more strongly affected, visibly different animal.

Genetics

The Hypo gene is incomplete dominant. Because the two-copy Super Hypo looks different enough to settle the mode, some people in the hobby call it dominant or co-dominant instead. This is the same looser usage used for other incomplete dominant boa genes. Hypo is in a complex with Motley. The year is not recorded when Rich Ihle first produced the Central American Hypo line. Rather than being the Hypo gene itself, Salmon Hypo and Pos Salmon Hypo are a separate, polygenic line. Ihle bred that line too from a boa thought to be a cross between a Colombian boa and a Panamanian hypo, and it is distinct from his Central American Hypo line. A further Hypo line is kept separately in Colombian red-tail boas. Hypo is the base of Sunglow and Moonglow when combined with an albino gene, and it gives Ghost with Anerythristic.

Known issues

The homozygous form, Super Hypo, has a documented musculature issue. It has not been shown to affect lifespan or breeding success.