Mating stimulates female feeding: testing the implications for the evolution of nuptial gifts

Modulation of seminal fluid molecules by males and females

In insects, seminal fluid molecules (SFMs) influence female post-mating phenotypes that affect reproductive success including egg development, sperm use, mating behavior, attractiveness, and lifespan. Yet, the magnitude of these effects can be quite variable, even within inbred strains. This variation is important because it could impact post-copulatory reproductive success of both males and females. One likely cause of this variation is modulation by males or females of the quantities or qualities (e.g. stability or activity state) of SFMs, or, in the case of females, of their sensitivity to SFMs. Here, I review opportunities for SFM modulation by males and females and propose that these processes could provide mechanisms by which information received before and during copulation influences post-copulatory reproductive success.

Mating changes the female dietary preference in the two-spotted cricket, Gryllus bimaculatus

Most insect species exhibit characteristic behavioral changes after mating. Typical post-mating behaviors in female insects include noticeable increases in food intake, elevated oviposition rates, lowered receptivity to courting males, and enhanced immune response. Although it has been reported that mated females of several insect species including the fruit fly, Drosophila melanogaster increase the amount of food intake and change their dietary preferences, the limited number of comparative studies prevent the formulation of generalities regarding post-mating behaviors in other insects in particular amongst orthopteran species. Here, we investigated whether females of the two-spotted cricket, Gryllus bimaculatus, alter their feeding behavior after mating. Although significant differences in the amount of food intake after mating were not observed, all experimental data indicated a clear trend among crickets toward the ingestion of larger quantities of food. Geometric framework analyses revealed that the mated female crickets preferred food with higher protein content compared to virgin female crickets. This implies that this species required different nutritional demands after mating. These findings further expand our understanding of the behavioral and biological changes that are triggered in female insects post-mating, and highlight the potential for this species in investigating the molecular-based nutritional dependent activities that are linked to post-mating behaviors.

Extreme costs of mating for male two-spot ladybird beetles

Male costs of mating are now thought to be widespread. The two-spot ladybird beetle (Adalia bipunctata) has been the focus of many studies of mating and sexual selection, yet the costs of mating for males are unknown. The mating system of A. bipunctata involves a spermatophore nuptial gift ingested by females after copulation. In this study, we investigate the cost to males of mating and of transferring spermatophores in terms of lifespan, ejaculate production and depletion of nutritional reserves. We found that males faced a strong trade-off between mating and survival, with males that were randomly assigned to mate a single time experiencing a 53% reduction in post-mating lifespan compared to non-mating males. This is among the most severe survival costs of a single mating yet reported. However, spermatophore transfer did not impact male survival. Instead, the costs associated with spermatophores appeared as a reduced ability to transfer spermatophores in successive matings. Furthermore, males ingested more food following spermatophore transfer than after matings without spermatophores, suggesting that spermatophore transfer depletes male nutritional reserves. This is to our knowledge the first report of an effect of variation in copulatory behaviour on male foraging behaviour. Overall, our study highlights the advantages of assessing mating costs using multiple currencies, and suggests that male A. bipunctata should exhibit mate choice.

Spermatophore consumption in a cephalopod

An individual's gametes can represent a nourishing food source for a manipulative mate. Here, we provide evidence of ejaculate and sperm consumption in a cephalopod. Through labelling male spermatophores with (14)C radiolabel, we found that female squid, Sepiadarium austrinum, consumed the spermatophores of their partners and directed the nutrients received into both somatic maintenance and egg production. We further show that in this species-where fertilization occurs externally in the female's buccal cavity-sperm storage is short-term (less than 21 days). The combination of female spermatophore consumption and short-term external sperm storage has the potential to exert strong selection on male ejaculates and reproductive strategies.

The seminal symphony: how to compose an ejaculate

Ejaculates are fundamental to fitness in sexually reproducing animals: males gain all their direct fitness via the ejaculate and females require ejaculates to reproduce. Both sperm and non-sperm components of the ejaculate (including parasperm, seminal proteins, water, and macromolecules) play vital roles in postcopulatory sexual selection and conflict, processes that can potentially drive rapid evolutionary change and reproductive isolation. Here, we assess the increasing evidence that considering ejaculate composition as a whole (and potential trade-offs among ejaculate components) has important consequences for predictions about male reproductive investment and female responses to ejaculates. We review current theory and empirical work, and detail how social and environmental effects on ejaculate composition have potentially far-reaching fitness consequences for both sexes.