How biases in sperm storage relate to sperm use during oviposition in female yellow dung flies

Precise mechanisms underlying sperm storage and utilization are largely unknown, and data directly linking stored sperm to paternity remain scarce. We used competitive microsatellite PCR to study the effects of female morphology, copula duration and oviposition on the proportion of stored sperm provided by the second of two copulating males (S2) in Scathophaga stercoraria (Diptera: Scathophagidae), the classic model for sperm competition studies. We genotyped all offspring from potentially mixed-paternity clutches to establish the relationship between a second male’s stored sperm (S2) and paternity success (P2). We found consistent skew in sperm storage across the three female spermathecae, with relatively more second-male sperm stored in the singlet spermatheca than in the doublet spermathecae. S2 generally decreased with increasing spermathecal size, consistent with either heightened first-male storage in larger spermathecae, or less efficient sperm displacement in them. Additionally, copula duration and several two-way interactions influenced S2, highlighting the complexity of postcopulatory processes and sperm storage. Importantly, S2 and P2 were strongly correlated. Manipulation of the timing of oviposition strongly influenced observed sperm-storage patterns, with higher S2 when females laid no eggs before being sacrificed than when they oviposited between copulations, an observation consistent with adaptive plasticity in insemination. Our results identified multiple factors influencing sperm storage, nevertheless suggesting that the proportion of stored sperm is strongly linked to paternity (i.e., a fair raffle). Even more detailed data in this vein are needed to evaluate the general importance of sperm competition relative to cryptic female choice in postcopulatory sexual selection.

Accelerated Sexual Maturation in Methoprene-Treated Sterile and Fertile Male Queensland Fruit Flies (Diptera: Tephritidae), and Mosquito Larvicide as an Economical and Effective Source of Methoprene

Queensland fruit flies Bactrocera tryoni (‘Q-fly’) have long adult prereproductive development periods, which can present challenges for sterile insect technique (SIT) programs. Holding the sterile flies in release facilities is expensive for control programs. Alternatively, releases of sexually immature males can lead to substantial mortality of sterile males before they mature. Recent studies have reported effectiveness of dietary supplementation with a mosquito larvicide (NOMOZ) that contains S-methoprene, a juvenile hormone analogue, for accelerating sexual development of fertile Q-fly males. However, it is not known whether effects on sterile flies are comparable to effects on fertile flies, or whether effects of methoprene-containing larvicide are comparable to effects of analytical standard methoprene such has been used in most studies. Here we address both knowledge gaps, investigating the effects of analytical standard methoprene and NOMOZ mixed with food and provided for 48 h following emergence on sexual development and longevity of fertile and sterile Q-flies. Compared with controls, fertile and sterile male Q-flies that were provided diets supplemented with methoprene from either source exhibited substantially accelerated sexual development by 2–3 d and longer mating duration. Unlike males, females did not respond to methoprene treatment. Although fertile and sterile flies were generally similar in sexual development and response to methoprene treatment, sterile flies of both sexes tended to have shorter copula duration than fertile flies. Neither methoprene supplements nor sterilization affected longevity of flies. The present study confirms effectiveness of dietary methoprene supplements in accelerating sexual development of both fertile and sterile male (but not female) Q-flies, and also confirms that low-cost mosquito larvicides that contain methoprene can achieve effects similar to those for high-cost analytical grade methoprene as prerelease supplements for Q-fly SIT.

Male–female interactions drive the (un)repeatability of copula duration in an insect

Across the animal kingdom the duration of copulation varies enormously from a few seconds to several days. Functional explanations for this variation are largely embedded within sperm competition theory in which males modulate the duration of copula in order to optimize their fitness. However, copulation is the union of two protagonists which are likely to have separate and often conflicting reproductive interests, yet few experimental designs specifically assess the effect of male–female interactions on the duration of copulation. This can result in inexact assertions over which sex controls copulatory behaviour. Here we analyse the repeatability of copulatory behaviour in the seed beetle Callosobruchus maculatus to determine which sex exerts primary influence over copulation duration. In C. maculatus , copulation follows two distinct phases: an initial quiescent phase followed by a period of vigorous female kicking behaviour that culminates in the termination of copulation. When males or females copulated with several novel mates, copulatory behaviour was not significantly repeatable. By contrast, when males or females mated repeatedly with the same mate, copula duration was repeatable. These data suggest copulatory behaviour in C. maculatus to be largely the product of male–female interactions rather than the consistent, sex-specific modulation of copula duration of one protagonist in response to the phenotypic variation presented by the other protagonist.

Machos Virgens e Acasalados de Ceratitis capitata Wiedemann (Diptera: Tephritidae) Apresentam o mesmo Sucesso de Cópula e a mesma Capacidade de Inibição de Recópula das Fêmeas?

A mosca-das-frutas, Ceratitis capitata Wiedemann é uma espécie polífaga que causa danos à fruticultura. Para seu controle, uma das técnicas utilizada é a técnica do inseto estéril (TIE), que consiste na liberação de milhares de machos estéreis no campo para competirem com os selvagens pelas fêmeas. O sucesso desta técnica está associado à habilidade do macho estéril em ser aceito pela fêmea e também em prevenir a recópula da mesma. Neste trabalho avaliou-se a influência do status reprodutivo do macho - virgem ou acasalado - no seu sucesso de cópula e na sua capacidade de inibir a recópula das fêmeas. Foram avaliados o tempo de latência e o tempo de duração da cópula de acasalamentos com os dois tipos de machos. Para verificar a capacidade de inibição de recópula, fêmeas acasaladas com machos virgens ou acasalados foram expostas a novos machos virgens um dia após o primeiro acasalamento e observadas quanto a ocorrência de recópula. Os resultados evidenciaram que machos de diferentes status reprodutivos apresentaram similaridades quanto ao sucesso de acasalamento e a capacidade de inibir a recópula das fêmeas, além de tempos similares de latência para a cópula e duração da mesma. Tais dados sugerem que, assumindo-se que os machos estéreis apresentam a mesma biologia básica de machos não estéreis, na aplicação da TIE, machos que já acasalaram uma vez no campo podem continuar a ter a mesma eficiência que os virgens quanto ao sucesso de acasalamento e a capacidade de inibição de recópula das fêmeas. Virgin and Mated Males of Ceratitis capitata Wiedemann (Diptera: Tephritidae) Have the Same Mating Success and the Same Ability to Inhibit Female Remating? Abstract. Ceratitis capitata Wiedemann is a polyphagous species that damages fruits and affects their production and consumption. One of the techniques to manage this pest is the Sterile Insect Technique, which consists in releasing sterile males in nature to compete with wild males for mating. The success of this technique is associated with the ability of sterile male in being selected by the female and in preventing female remating with other males. This paper aims to evaluate the influence of male reproductive status in mating success and in female remating inhibition. Tests for evaluating the latency to mate and copula duration were performed to evaluate latency to mate and copula duration based on different male status. In remating inhibition tests, females mated with virgin and mated males, were exposed to other males one day after the first mating so the rate of remating could be evaluated. The results showed that males of different reproductive status had no differences in mating success and in female remating inhibition. The latency to mate and copula duration were similar for both male status as well. Our results suggest that, assuming that the sterile males have the same basic biology of no sterile males, in SIT, after released in nature, mated males can have the same success in mating and female remating inhibition as virgin males.