rectal valve
A thin diaphragm located in the posterior fifth of the intestine of some Centrolophidae, e.g. Seriolella punctata, Schedophilus huttoni and Psenes pellucidus, or in others a sphincter-like constriction, e.g. Seriolella brama. A deep purple fluid was confined to the valve in S. punctata, but was found throughout the intestine in the other two species referred to. The fluid might be used to void a coloured cloud to distract or deter a predator.