Crossed induction of sex in sympatric congeneric rotifer populations

García-Roger, Eduardo M., Natália Dias, María José Carmona, Manuel Serra

Limnol. Oceanogr., 54(6), 2009, 1845-1854 | DOI: 10.4319/lo.2009.54.6.1845

ABSTRACT: The transition from asexual to sexual reproduction in rotifers of the genus Brachionus (Monogononta) is triggered by a chemical signal produced and released by the rotifers themselves; the signal accumulates in the environment as population density increases. The response to this signal has been hypothesized to be speciesspecific. If not, the timing of sex and final diapausing egg production of a species might not be optimized. In this study, a set of experiments—based on individual and mass culture approaches—was carried out to investigate the differentiation in sex induction signals between sympatric and allopatric congeneric Brachionus populations by analyzing the capability of the medium conditioned by the growth of a population (i.e., medium containing the inducing signal) to induce sex in a different one. We found that populations induce sex in response to medium conditioned by congeneric populations. Results suggest differences among species in their production and responsiveness to sex-inducing signals, as well as slight differentiation in these signals. The observed lack of strong differentiation between sympatric populations is proposed to have implications in avoidance of competition.

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