Postmating sexual selection and the enigmatic jawed genitalia ofCallosobruchus subinnotatus

SummaryInsect genitalia exhibit rapid divergent evolution. Truly extraordinary structures have evolved in some groups, presumably as a result of post-mating sexual selection. To increase our understanding of this phenomenon, we studied the function of one such structure. The male genitalia ofCallosobruchus subinnotatus(Coleoptera: Bruchinae) contain a pair of jaw-like structures with unknown function. Here, we used phenotypic engineering to ablate the teeth on these jaws. We then experimentally assessed the effects of ablation of the genital jaws on mating duration, ejaculate weight, male fertilization success and female fecundity, using a double-mating experimental design. We predicted that copulatory wounding in females should be positively related to male fertilization success. However, we found no significant correlation between genital tract scarring in females and male fertilization success. Male fertilization success was, however, positively related to the amount of ejaculate transferred by males and negatively related to female ejaculate dumping. Ablation of male genital jaws did not affect male relative fertilization success but resulted in a reduction in female egg production. Our results suggest that postmating sexual selection in males indeed favors these genital jaws, but not primarily through an elevated relative success in sperm competition but by increasing female egg production.

Different effects of paternal trans-generational immune priming on survival and immunity in step and genetic offspring

Paternal trans-generational immune priming, whereby fathers provide immune protection to offspring, has been demonstrated in the red flour beetle Tribolium castaneum exposed to the insect pathogen Bacillus thuringiensis . It is currently unclear how such protection is transferred, as in contrast to mothers, fathers do not directly provide offspring with a large amount of substances. In addition to sperm, male flour beetles transfer seminal fluids in a spermatophore to females during copulation. Depending on whether paternal trans-generational immune priming is mediated by sperm or seminal fluids, it is expected to either affect only the genetic offspring of a male, or also their step offspring that are sired by another male. We therefore conducted a double-mating experiment and found that only the genetic offspring of an immune primed male show enhanced survival upon bacterial challenge, while phenoloxidase activity, an important insect immune trait, and the expression of the immune receptor PGRP were increased in all offspring. This indicates that information leading to enhanced survival upon pathogen exposure is transferred via sperm, and thus potentially constitutes an epigenetic effect, whereas substances transferred with the seminal fluid could have an additional influence on offspring immune traits and immunological alertness.

Brainless but not clueless: earthworms boost their ejaculates when they detect fecund non-virgin partners

In many animals in which females store sperm, males may detect female mating status and, in order to outcompete rival sperm, increase ejaculate size when copulating with non-virgin females. Although most studies have been restricted to organisms with separate sexes, theoretical models suggest that sperm competition should also be an important selective agent shaping life-history traits in simultaneous hermaphrodites. Nevertheless, the empirical support for ejaculate adjustment in a mating opportunity is scarce in hermaphrodites. In the present study, we performed a double-mating experiment to determine whether earthworms ( Eisenia andrei ) detect the mating status of their partners and whether they respond by adjusting their ejaculate. We found that earthworms triplicated the donated sperm when mating with a non-virgin mate. Moreover, such increases were greater when the worms were mated with larger (more fecund) partners, indicating that earthworms perform a fine-tune control of ejaculate volume. The results of the present study suggest that, under high intensity of sperm competition, partner evaluation is subject to intense selection in hermaphrodite animals, and donors are selective about to whom they donate how much sperm.

Rabbits behaviour under modern commercial production conditions – a review

Recently, much work has been done to record the diurnal peak of does receptivity. It was found that the highest was in the morning and before allowing suckling. Such studies suggested that mating should be achieved in the morning or before suckling to avoid the negative effect of the circadian peak of prolactin on receptivity that occur around 15.00 to 19.00 h and after each suckling. Some cases of pseudo-pregnancy might be prevented by double mating; the second mating should be within at most five hours after the first, since mating later than this would have no effect. Total parturition time would be 10–14 minutes for a large litter and 5–7 minutes for an average litter, although parturition could be induced to allow prompt attention to does with poor maternal instinct and to those kindle for the first time kindling and to avoid situations such as: kindling at night or in cold weather and/or to avoid the variability in gestation periods (29 to 34 days). Mother-litter separation during night can influence species specific nursing behaviour and may lead to lower weaning weights of pups. Applying good management programs, as well as, change of place, gentle handling of the stressed dams, correcting nutritional deficiencies and inadequate drinking water and provision of adequate amount of straw, may well eliminate stress, correct behavioural disorders and certain types of maternal anomalies which appear to be not under the control of hormonal or genetic factors. Welfare for caged rabbits can be improved by feeding the animals in the afternoon rather than in the morning. Aggressive behaviour was greater in rabbits on nipple drinkers than in those on troughs. In conclusion, better understanding of rabbits natural behaviour under the different conditions, maintains optimal production compatible with welfare demands. Below, description of rabbits behaviour and its relation with modern commercial production conditions, were discussed.

Male mate choice and patterns of paternity in the polyandrous, sexually cannibalistic orb-web spider, Nephila plumipes

Studies that investigate patterns of paternity in polyandrous species typically employ double-mating trials, in which the paternity share of each male is established by either the sterile male technique or using genetic markers. However, polyandrous females may mate with more than two males and, in some species, triple-mating trials produce different patterns of paternity from double-mating trials. We investigated patterns of paternity share in triple-mating trials of the sexually cannibalistic orb-web spider Nephila plumipes. These experiments reveal little quantitative changes to paternity share when more than two males mate with the female; the third male apparently diluted the fertilisation success of the second male but not of the first male. Sexual cannibalism had little impact on the fertilisation success of the first male, but greatly increased the fertilisation success of the third male. When offered a choice, males did not prefer to mate with virgin over mated females, but males that chose virgin females were significantly heavier than those that chose mated females.