Maintenance of androdioecy in the freshwater clam shrimp Eulimnadia texana: longevity of males relative to hermaphrodites

The clam shrimp Eulimnadia texana exhibits a rare mixed mating system known as androdioecy. In this ephemeral-pond branchiopod crustacean, males coexist with hermaphrodites, which can outcross with males or self-fertilize. We provide an estimate of the longevity of males relative to hermaphrodites (1 – σ), an important parameter of a model that was developed to explain the conditions under which this system would be stable. Under both optimal rearing conditions and various sex-ratio treatments, hermaphrodites from two study populations lived significantly longer than males. Since various aspects of mating have been found to be costly to males and females/hermaphrodites in other taxa, we explored this possibility as well. Hermaphrodites showed no differences in longevity when kept in groups provided with different mating opportunities. Males, however, lived significantly longer when mating opportunities were increased, a result contrary to what we had expected. Behavioral observations, however, suggested that male–male interactions may have been deleterious to males living in groups with little opportunity to mate. This was confirmed by an additional study in which individual males were maintained in the presence and absence of hermaphrodites. Under these conditions we still detected no longevity cost of mating for males.