Condition-dependent ejaculate size and composition in a ladybird beetle

Abstract

Sexually selected male ejaculate traits are expected to depend on the resource state of males. Theory predicts that males in good condition will produce larger ejaculates, but that ejaculate composition will depend on the relative production costs of ejaculate components and the risk of sperm competition experienced by low-and high-condition males. Under some conditions, when low condition leads to poorer performance in sperm competition, males in low condition may produce ejaculates with higher sperm content relative to their total ejaculate and may even transfer more sperm than high-condition males in an absolute sense. Previous studies in insects have shown that males in good condition transfer larger ejaculates or more sperm, but it has not been clear whether increased sperm content represents a shift in allocation or simply a larger ejaculate, and thus the condition dependence of ejaculate composition has been largely untested. We examined condition dependence in ejaculate by manipulating adult male condition in a ladybird beetle (Adalia bipunctata) in which males transfer three distinct ejaculate components during mating: sperm, non-sperm ejaculate retained within the female reproductive tract, and a spermatophore capsule that females eject and ingest following mating. We found that high condition males indeed transferred larger ejaculates, potentially achieved by an increased rate of ejaculate transfer, and allocated less to sperm compared with low-condition males. Low-condition males transferred ejaculates with absolutely and proportionally more sperm. This study provides the first experimental evidence for a condition-dependent shift in ejaculate composition.

Protein-specific manipulation of ejaculate composition in response to female mating status in Drosophila melanogaster

“…However, only recently have researchers begun to investigate nonsperm aspects of ejaculate allocation theoretically (36) and empirically (30,52,53). Moreover, the idea that males can potentially exploit the ejaculates of rival males is a recent one that has previously received only theoretical attention (3,4).…”

Protein and carbohydrate intake influence sperm number and fertility in male cockroaches, but not sperm viability

“…B 282: 20142144 feeding has the potential to greatly influence the intake of nutrients [48]. Thus, it is possible that the decrease in sperm number seen in ladybirds [31] and Mediterranean fruitflies [32] with higher diet quality may actually reflect a suboptimal intake of nutrients for sperm production in these species. Our work therefore clearly illustrates the value of using the GF approach to understand dietary effects on male ejaculates [43].…”

“…A limitation of all previous studies examining the relationship between diet and sperm production in insects is that an explicit nutritional framework was not used to manipulate diet quality [27][28][29][30][31][32]. Thus, it is not possible to separate the effects of total nutritional content (i.e.…”

DNA Repair Pathway Choice Is Influenced by the Health of Drosophila melanogaster

“…While we are aware of no studies directly examining whether condition affects cell cycle dynamics, numerous studies examining life-history traits (i.e., development time, body size, longevity) have shown that individuals in higher condition have increased growth-related fitness (Jenkins et al 2001;Hunt et al 2004;Reitzel 2004;Perry and Rowe 2010). Therefore, high-condition individuals, whose cells likely have sufficient resources to get ready for mitosis faster, might spend proportionally less time in the growth phases of the cell cycle (e.g., G2) so that fewer of their DSBs will occur during the phase when they have the greatest probability of being repaired by HR-h.…”