Single fathers sacrifice their broods and re-mate quickly in a socially monogamous cichlid

When one of two parents disappears in the midst of caring for offspring, the remaining parent is left with several options. They can either (1) desert the brood, (2) continue caring on their own and reject propositions from new potential partners, or (3) continue caring but remain receptive to re-mating opportunities. The presence of a brood may increase re-mating success of single parents, either because brood care is perceived as a signal of partner quality, or because prospective mates perceive the brood as potential energy source. In this field experiment, we used the socially monogamous, biparental cichlid fish Variabilichromis moorii to examine the re-mating strategy of males with or without dependent offspring after the loss of their female partner. Partner vacancies were filled quickly by new females, and these females engaged in high levels of affiliative behavior with the males. The new females engaged in territorial defense, but focused primarily against intruding conspecifics, likely as a means to repel rivals. The males, in turn, took over the majority of territorial defense against intruding heterospecifics. Interestingly, males that still had offspring from their previous partnerships did not show aggression toward their new female partners, even when those females were infanticidal and cannibalizing the males' current offspring. Overall, our experiment shows that single fathers of a biparental species will re-mate quickly even at the detriment to their current offspring.

Male Age Influences Re-mating Incidence and Sperm Use in Females of the Dengue Vector Aedes aegypti

Diseases transmitted by female Aedes aegypti mosquitoes are public health issues in countries in the tropics and sub-tropics. As in other insects, A. aegypti females undergo behavioral and physiological changes upon mating that principally act to facilitate the production of progeny. The primary effectors of A. aegypti female post-mating responses are male-derived seminal proteins that are transferred to females during mating. Increased male age reduces ejaculate function in numerous taxa and alters seminal protein composition in Drosophila melanogaster, but the impacts of male age on female A. aegypti post-mating responses are unknown. Here, we used "old" (21-22 days old) and "young" (4-5 days old) A. aegypti males to assess the influence of male age on oviposition, fertility, and re-mating incidence in their mates. We also examined how age influenced paternity share in females initially mated to young or old males that subsequently re-mated with a transgenic male that transferred RFP-labeled sperm and whose progeny inherited a larval-expressed GFP marker. We found that increased male age had no effect on female fecundity or fertility but significantly impacted their ability to prevent re-mating in their mates-more than half (54.5%) of the females mated to an old male re-mated, compared to 24% of females initially mated to a young male. Polyandrous A. aegypti females displayed first male precedence regardless of the age of their initial mate. However, young males were better able to compete with rival male sperm, siring significantly more progeny (77%) compared to old males (64%). Young males had significantly more sperm in their seminal vesicles than old males at the time of mating, although males of both age groups transferred similar numbers of sperm to their mates. Our results suggest that male senescence differentially impacts the induction of some post-mating changes in A. aegypti females. As the effect of age may be further exacerbated in the field, age-related declines in male ability to induce sexual refractoriness have implications for A. aegypti population control programs that release adults into the environment.

Pre- and Post-Copulatory Competitiveness of the Genetic Sexing Strain Tapachula-7 of Anastrepha ludens (Diptera: Tephritidae)

Anastrepha ludens (Loew) (Diptera: Tephritidae) is an endemic pest of Mexico, attacking several fruits of economic importance. The Sterile Insect Technique (SIT), consisting of mass-rearing, irradiation and release of adults, is used to control this pest in affected areas. Currently, a genetic sexing strain (Tapachula 7, Tap-7) consisting only of A. ludens males is being released, yet we lack information on its sexual performance at the early ages when they are released and on its post copulatory behavior in terms of sperm transfer and mating inhibition. Here, sexual competitiveness at young ages and ability to inhibit female re-mating was compared between sterile Tap-7, Standard Bisexual (SB), or wild males both in laboratory and field cage conditions. Sperm stored by females mating with wild, Tap-7, or SB strain males was also compared. Six-day-old sterile Tap-7 males had low mating rates, however, by 7 d of age 80% of males had mated. Tap-7 males were just as likely as wild males to inhibit wild female re-mating. In field cages, sterile Tap-7 males mated faster than wild and sterile males from the SB strain and had comparable mating success to wild males. Females mated to sterile Tap-7 males stored more sperm than those mated to sterile SB males. Females mated to wild males stored more sperm than females mated to any other type of male. Mass-rearing had a greater effect on decreasing sperm stored by females than irradiation. We recommend continuing the release of the GSS strain of A. ludens.

Does time after pair bond disruption affect subsequent reproduction in the socially monogamous woodland vole (Microtus pinetorum)?

Disruption of the pair bond between socially monogamous animals leads to changes in behavior, which may have reproductive consequences. There are two alternative hypotheses to explain the effect of the length of time since pair bond disruption on subsequent reproduction. One hypothesis predicts that voles housed immediately with a new opposite-sex conspecific will be as likely to produce litters and will produce them as quickly as voles separated from their initial mate for longer. Alternatively, if attachment between mates is enduring, we expect that more voles separated longer from their previous mates will produce litters and produce them sooner than voles re-paired immediately after separation from their initial mates. Woodland voles, paired with opposite-sex conspecifics, remained together until parturition. Mates were then separated for 0, 7, or 14 days until re-pairing with an opposite-sex conspecific. Pair bond disruption did not prevent males and females from mating subsequently, which was consistent with data from our breeding colony. In addition, the length of time an individual remained alone after pair bond disruption did not affect the latency to produce a litter. Our results show that having been paired previously does not affect subsequent reproduction in this socially monogamous vole.