Darwinulid ostracods: Ancient asexual scandals or scandalous gossip?

Abstract

Whereas studies of putative ancient asexuals could help solve the paradox of sex, most research on such groups still focuses on consolidating their status. The evidence for the darwinulid ostracods is as yet inconclusive. Recent males have been found in a single species, but their functionality is uncertain and their morphology highlights the erroneous assignment of male status to a single individual of Darwinula stevensoni, presently the best candidate for an ancient asexual darwinulid. Previous records of putative fossil males for the past 200 million years have been rejected. Genetic signatures of ancient asexuality are equally inconclusive: there is no Meselson effect in the darwinulids, but neither the presence nor the absence of the Meselson effect does provide conclusive evidence for or against sex. However, it would seem that a combination of a general purpose genotype with powerful homogenising genetic mechanisms (gene conversion, DNA repair) could counter the deleterious effects of the absence of sex in at least a number of darwinulid species.