Identification and phyletic distribution of the plasma esterases of some anthropoid primates

Using electrophoresis, specific staining, and selective inhibition, we examined and identified esterase components in the plasma of 13 anthropoid species: 5 hominoids, 7 cercopithecoids, and 1 platyrrhine. Most species, unlike humans, exhibited one or more arylesterase and/or carboxylesterase components as well as cholinesterase and albumin-associated arylesterase. A distinctive arylesterase probably indicates pregnancy in cercopithecoids. While some characters (such as the net charge of the cholinesterase molecule) were extremely uniform across all taxa examined, other quantitative and qualitative traits showed intra- and interspecific variation. Comparison of a cladogram with the distribution of traits shows that the least phyletically stable traits are, in general, those that also exhibit intraspecific polymorphism. One genus-specific, and therefore relatively conservative, trait (weak dimer-dimer bonding in the cholinesterase molecule) evidently appeared independently among papionin cercopithecoids and hominoids. The most parsimonious interpretation of this distribution reinforces the notion of a Pan-Gorilla-Homoclade sororally related to Pongo.In general, plasma esterases are an underexploited source of genetic markers in primates.