Sperm Supply Research Articles

Female feeding regime and polyandry in the nuptially feeding nursery web spider, Pisaura mirabilis

We examined the influence of female feeding regime on polyandry in the nuptially feeding nursery web spider (Pisaura mirabilis). In this species, the nuptial gift, a dead prey item wrapped in the male's silk, is physically separate from the ejaculate. We manipulated female feeding regime (starved or fed) and the presence or absence of a gift with three successive males to test direct-benefits hypotheses (nuptial gift or sperm supply) for the expression of polyandry. The presence of a gift was necessary for copulation, as no male without a gift successfully copulated. Female mating behavior most strongly supports polyandry due to the accumulation of gifted food items ("nuptial gift" direct-benefits hypothesis). Starved females that were presented with a gift accepted significantly more gifts and inseminations than fed females. Most starved females (74%) copulated two or more times, as opposed to only 3% of the fed females. Nearly all of the females that accepted a gift subsequently copulated. The nuptial gift item seems to function as male mating effort and females appear to receive multiple matings as part of a feeding strategy.

Reproductive strategies of Aphidius ervi Haliday (Hymenoptera: Aphidiidae)

Hymenopteran parasitoids are usually arrhenotokous parthenogenetic, where females arise from fertilized and males from unfertilized eggs. Therefore, the reproductive fitness of females is a function of egg production and furthermore affected by mating, whereas that of males is mainly determined by the number of daughters they father. Aphidius ervi Haliday is a quasi-gregarious parasitoid of a number of aphid pests on economically important crops such as legumes and cereals. Females are monandrous whereas males are polygynous. Here, we tested how parental age at mating and male mating history affected mating success, fecundity and daughter production in this species. Once-mated males perform significantly better than naïve males with regard to mating success, suggesting that males learn from previous matings. The fecundity of virgin females is not significantly different from that of mated females regardless of parental age at mating and male mating history, indicating that mating does not stimulate egg production or contribute to female nutrient supply. Males can replenish sperm supply after mating, implying that they are at least moderately synspermatogenic. Preference for young over old mates for mating by both sexes may be explained by the fact that aging of both sexes contributes to the reduction of daughter production. Rather than sperm depletion, the reduced daughter production may be attributed to diminishing sperm viability and mobility in aging males and increasing constraints in fertilization process in aging females. Our results also show that female age has a stronger impact on the production of daughters, suggesting that fertilization process in females is more sensitive to aging than sperm vigor in males.

Strategic ejaculation in the egg parasitoid Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

Abstract 1. Several parameters influence sperm allocation by males, including their size and sperm stock, intra‐specific variability, quality of females’, as well as the risk and intensity of sperm competition.2. Models predict that males should invest the maximum ejaculate size when sperm competition intensity is low. As sperm competition intensity increases, males should decrease the number of sperm transferred during mating.3. This decrease in sperm transfer to females occurs because the benefits gained by males with each extra unit of expenditure on sperm decrease. When sperm supply is not unlimited, males could expect a better return by keeping some or all sperm for mating under lower competition intensity.4. In this study, the ejaculate size of males that were kept in groups of one, five or 10 males prior to mating, has been investigated in the haplodiploid egg parasitoid Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae).5. As predicted by theory, the number of sperm transferred decreased significantly with an increase in the number of rivals.6. This is the first study showing strategic sperm allocation depending on sperm competition intensity in a parasitoid.

Artificial insemination technology for ratites: a review

In ratite farming, the low male to female ratio in the mating system restricts genetic improvement and prevents reduction of the number of males kept on-farm for fertilisation of the female flock. These issues can be overcome and the industry can better realise its potential by using artificial insemination (AI) technology. It is the only practical method for intensive genetic improvement of reproduction and the production of eggs, chicks, oil, meat and leather. For AI to be feasible, we need reliable methods for semen collection, artificial insemination, prolonged storage of spermatozoa in the female tract, high rates of lay, efficient protocols for semen storage, and a panel of quantitative methods for measuring true fertility and hatchability, sperm supply rates in vivo and sperm viability in vitro. For both emus and ostriches, prolonged sperm storage in females has already been demonstrated. Methods for semen collection and artificial insemination, using animal-friendly techniques, have also been developed. Semen storage and cryopreservation protocols are yet to be optimised and we still need to overcome the male-dependent rate of lay, but adoption of AI technology by the ratite industries is now feasible. It also seems likely that these technologies will be relevant to wild ratites that need intensive conservation efforts, such as cassowaries, rheas and ostrich subspecies.

Mating success and potential male-worker conflict in a male-dimorphic ant

BackgroundMales of many species adjust their reproductive tactics with regard to their condition and status. For example, large males may develop weapons and fight for access to females, whereas small or undernourished males do not express costly weapons or ornaments and sneak copulations. Different condition-dependent reproductive tactics may be associated with unequal average fitness, but the tactic chosen by a given male under given circumstances is thought to result in the highest possible fitness return.The ant species Cardiocondyla obscurior exhibits an environment-controlled polymorphism of docile, winged males and aggressive "ergatoid" males. Ergatoid males, which can replenish their sperm supply throughout their lives, engage in lethal fighting, and attempt to monopolize all female sexuals available in their nests, were previously assumed to gain higher lifetime reproductive success than the peaceful, winged males, which disperse to mate away from the nest and whose spermatogenesis is limited to the first days of adult life. However, precise data on male mating success have as yet not been available.Here, we compare the average mating success of the two male morphs, taking the high mortality rate of immature ergatoid males into account. Because individuals in insect societies may have opposing interests about their own development, we also investigate whether the interests of male larvae coincide with those of the workers and the rest of the society.ResultsWhen the survival probability of males is taken into account, winged males are more likely to mate multiply and in consequence have a higher estimated average mating success than ergatoid males. Therefore, male larvae are expected to prefer developing into winged instead of ergatoid adults.ConclusionThough male larvae can expect a higher average mating success when developing into winged males, most colonies produce only ergatoid males under standard conditions. This might point at a novel type of potential kin conflict within the social insect colony. Because workers in insect societies usually control male larval development, ergatoid male production under normal conditions probably reflects the optimal allocation strategy of workers to maximise their inclusive fitness.

Variation of sperm allocation with male size and recovery rate of sperm numbers in spiny king crab Paralithodes brevipes

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 312:189-199 (2006) - doi:10.3354/meps312189 Variation of sperm allocation with male size and recovery rate of sperm numbers in spiny king crab Paralithodes brevipes Taku Sato1,*, Masakazu Ashidate2, Tadao Jinbo2, Seiji Goshima1 1Laboratory of Marine Biodiversity, Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan 2IAA, FRA, National Center for Stock Enhancement, Akkeshi Station, 2-1 Tsukushikoi, Akkeshi, Hokkaido 088-1160, Japan *Email: takyun@mail.goo.ne.jp ABSTRACT: This study examined whether sperm allocation by males can limit sperm passed to females in fished spiny king crab populations in which large males are selectively fished. We investigated the recovery rate of sperm in vasa deferentia of males of different body sizes, sperm allocation passed to females of different body sizes by males of different body sizes, and sperm allocation in different male:female sex ratios (1:1 or 1:6) by males of different body sizes by laboratory experiments. The recovery rates of sperm were very slow regardless of male size, suggesting that a sperm allocation strategy is important to increase male reproductive success in this species. In large males, the ejaculate size increased significantly with increasing female size, but the ejaculate size of small males did not vary with female size, indicating that small males cannot increase ejaculate size by more than a certain number. Females mated with small males showed significantly lower fertilization rates than females mated with large males. Males showed no difference in pattern of sperm allocation between the different sex ratios in both male size classes. These results suggest that a decrease in mean male size due to male-only fishing would increase the number of females mated with small males without an ability to increase ejaculate size with increasing female size, which would result in females mating with small males would receive an insufficient sperm supply and have a low fertilization rate due to sperm limitation. KEY WORDS: Sperm limitation · Sperm allocation · Sperm-to-egg ratio · Recovery rate · Male-only fishing · Paralithodes brevipes Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 312. Online publication date: April 24, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Females benefit from mating with different males in the scorpionfly Panorpa cognata

The adaptive significance of female polyandry has become a recurrent subject of recent theoretical and empirical research. It has been argued that in addition to direct benefits, such as nuptial gifts or an adequate sperm supply, females may gain genetic benefits from mating with different males. Females of the scorpionfly Panorpa cognata mate with several males during their lifetime. In an experiment designed to rule out any direct nutritional benefit of multiple matings, I found that polyandrous females that mated with two different males achieved a significantly higher egg-hatching success than monandrous females that mated twice with the same male. However, individual males did not trigger the same response in different females as the egg-hatching success of different females that mated with one and same male did not correlate. The results, thus, do not conform to predictions from hypotheses assuming that genetic benefits of polyandry are influenced by the intrinsic genetic quality of males. The results are, however, consistent with the genetic incompatibility hypothesis. Nevertheless, substances from different males transferred during copulation may synergistically affect zygote viability. Furthermore, I discuss why paternity studies can only explicitly test the genetic incompatibility hypothesis if there are a priori expectations of female-male genome compatibilities.

Why do sperm-depleted parasitoid males continue to mate?

Insect males of several parasitoid species have limited amount of sperm at emergence and experience sperm depletion when mate acquisition rate is high, suggesting that sperm production and storage could be a limiting factor for male's fitness. Sperm-depleted males of the parasitoid wasp Trichogramma evanescens continue to mate, and the impact of this behavior on sperm storage by females has been studied. Virgin females T. evanescens stored 50.6 ± 13.1 (Mean ± SD) sperm when mating first with a virgin male. However, when these females mated first with a sperm-depleted male and then with a virgin male, they stored only 18.9 ± 7.8 sperm, indicating that mating with a sperm-depleted male has a cost and limits sperm acquisition from fertile males. Following a mating with a sperm-depleted male, females had to mate with three virgin males to restore their sperm supply confirming that additional mating enabled the female to store a limited number of sperm. According to our results, by continuing to mate, sperm-depleted males do not prevent mates from copulating again but they decrease their ability to store other male's sperm. Continuing to mate could be a strategy to increase the relative fitness of sperm-depleted males.

Stalk-eyed flies

Stalk-eyed flies

Females Mated without Sperm Transfer Maintain High Sexual Receptivity in the Wolf Spider Schizocosa malitiosa

AbstractThe mating of the Neotropical lycosid Schizocosa malitiosa is long and complex, involving intense genital stimulation and copulatory courtship. This suggests functions other than just insemination. Previous data indicated that mated females of this species are less sexually receptive than virgins. We hypothesise that copulatory characteristics presented by males during prolonged copulations could be responsible for subsequent female sexual reluctance, and may be selected by cryptic female choice. Our objective was to examine the influence of copulatory behaviour on subsequent female sexual receptivity in S. malitiosa, isolating it from the effects of sperm transfer per se. For this purpose, we obtained males without sperm in their copulatory organs (palpal bulbs), and prevented them from charging their palps by sealing their genital pores immediately after their last moult (treated males). Virgin females were separated into three groups: (i) females exposed once to normal males, (ii) females exposed twice to normal males, and (iii) females exposed first to treated and second to normal males. The results showed that, 3 d after their first mating, females first mated with untreated males were frequently refractory to remating, whereas all those first mated with treated males were receptive. Copulations performed by treated males showed some differences from those performed by normal males, but maintained the basic behavioural pattern with abundant sexual stimulation. The presence of sperm fluids in the female receptacles appears to be the most likely factor generating female remating reluctance. Males may manipulate female responses using receptivity inhibiting substances in their sperm, like those described for insects. Females would first ensure sperm supply, becoming more choosy afterwards. All females, whether mated once or twice, generated similar numbers of progeny, indicating no relationship between number of matings and number of spiderlings.

Evolution of male morphology in the ant genus Cardiocondyla

The ant genus Cardiocondyla is characterized by a striking male polymorphism, with wingless, local fighter males (ergatoid males) with life-long spermatogenesis, and winged, peaceful disperser males with limited sperm supply. We examined the evolution of male morphology by reconstructing the phylogeny of Cardiocondyla from sequences of the mitochondrial COI/COII and 16S RNA genes from 13 of the 15 species, of which males are known. Data suggest that male polymorphism is ancestral and that winged males were lost convergently in several taxa, such as C. elegans, C. batesii, and C. mauritanica. Saber-shaped mandibles and lethal fighting among adult ergatoid males might probably have been the original condition, from which strong, shear-shaped mandibles and attacks directed predominantly against freshly eclosed, not yet sclerotized males might have evolved once. The evolution of queen number from ancestral polygyny to derived monogyny appears to be associated with a switch in the behavior of ergatoid males from fighting to mutual tolerance.

Effects of male mating frequency and male size on ejaculate size and reproductive success of female spiny king crab Paralithodes brevipes

Potential sperm limitation in a fished population of the spiny king crab Paralithodes bre- vipes was investigated in controlled laboratory experimental and field studies. The laboratory exper- iments examined the effects of male size and mating frequency on their reproductive potential and the recovery rate of exhausted sperm. The spawning success and fertilization rate of females decreased as the male mating frequency increased. The effects of increased male mating frequency on the spawning success of females and fertilization rates differed between male size classes. Male size and mating frequency have great influences on sperm limitation. Males showed little capacity to regenerate sperm, increasing the likelihood of limited sperm supply to females in fished population with low numbers of males due to male-selective fishing regulations. The field studies examined the structure of a fished population of P. brevipes in Hamanaka, eastern Hokkaido, before and after a change in the fishery regulations that permitted smaller males to be harvested. The results showed that a change in the sex ratio occurred after the fishery regulations were introduced, skewing the population towards females. The results also showed a decrease in the mean male size in the fished population. The results also indicated that a significant percentage of males (42.2%) had depleted sperm reserves just after the reproductive season. Overall, the results indicate that sperm limitation could occur in this fished population of P. brevipes. These observations may warrant a review of the current fishing regulations, particularly the minimum legal size.

Sexual maturity in females of deep-sea red crab Chaceon notialis (Brachyura, Geryonidae) in the southwestern Atlantic Ocean

Summary Chaceon notialis is a brachyuran crab inhabiting the continental slope (250–1,000 m) off Uruguay in the southwestern Atlantic Ocean, constituting one of the main exploited stocks of deep-sea red crab in the world. The objective of this paper was to estimate size at morphological and physiological sexual maturity in females of Chaceon notialis in Uruguayan waters. Crabs were obtained from commercial samples taken in 1997 and 1998. For each individual, carapace width (CW) was measured and morphological (abdomen width and vulval features) and physiological (ovarian maturity) reproductive indicators were examined in order to estimate the size at sexual maturity. As the existence of a terminal molt still cannot be confirmed in females of C. notialis, we tested the alternative hypotheses that females: (1) have indeterminate growth and (2) exhibit a terminal molt. Hypothesis 1 was evaluated by fitting the logistic maturity function that provides the CW50% of females with mature vulvae, whereas hypothesis 2 was evaluated through the analysis of CW frequency distributions of morphologically and physiologically mature females. In addition, 50 pairs of female spermathecae were examined to determine if insemination had occurred; the carapace hardness of the individuals concerned was also noted. Two patterns of vulval morphology in females of C. notialis were observed for the first time: immature or ttclosedtt vulvae, and mature or ttopenedtt vulvae, respectively. Estimations of size at sexual maturity differed according to the hypothesis evaluated: under the assumption that females continue growing after the pubertal molt, mean sizes at morphological and physiological maturity (CW50%) were estimated as 70.2 mm and 71.7 mm, respectively. Alternatively, if females have a terminal molt, mean (± SD) estimates were 91.5 ± 8.5 mm and 91.1 ± 8.0 mm, respectively. Both scenarios clearly suggest synchrony between vulval and ovarian maturity. The species displays a soft mating system and most mature postmolt females lacks seminal contents in their reservoirs, in spite of evidence of successful mating (abrasion marks). This suggests that, due to selective exploitation of males, sperm supply may have become a limiting resource for the reproductive output of the population. Under the terminal molt hypothesis, females at the pubertal moult will be the only individuals in the population contributing to reproduction. Taking into account these findings, we suggest that the current regulations are reassessed, including the use of the terminal molt scenario for fishery management because it provides a precautionary framework in a situation where the life history of the targeted stock is data-limited.

Insemination potential of male Trichogramma evanescens

AbstractReproduction strategies of male parasitoids have received less attention than those of the females. In hymenopteran parasitoids that reproduce by arrhenotokous parthenogenesis, virgin females are able to reproduce, but they are constrained to produce only males. In such species, the number of sperm transferred to females is of prime importance for female reproductive success. In this study, we measured the insemination potential of male Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae). Independent of their age and their sperm‐depletion status, males continued to mate with females until the end of their life. They quickly depleted their sperm supply by fertilizing 18 females during their lifetime, among which 80% were inseminated during the first 24 h. They fathered around 400 daughters over their lifetime. Our results suggest an absence of imaginal spermatogenesis in T. evanescens males that can be designated as prospermatogenic. Sperm is thus a limited resource in this species and females might encounter males with varying amounts of sperm.

Sexual conflict and cooperation under naturally occurring male enforced monogamy

An evolutionary conflict often exists between the sexes in regard to female mating patterns. Females can benefit from polyandry, whereas males mating with polyandrous females lose reproductive opportunities because of sperm competition. Where this conflict occurs, the evolution of mechanisms whereby males can control female remating, often at a fitness cost to the female, are expected to evolve. The fitness cost to the female will be increased in systems where a few high status males monopolise mating opportunities and thus have limited sperm supplies. Here we show that in the cockroach Nauphoeta cinerea, a species where males enforce female monogamy in the first reproductive cycle, males that have become sperm depleted continue to be able to manipulate female remating behaviour. Although the manipulation severely decreases fecundity in females mated to sperm-depleted males, males benefit, increasing their relative fitness by preventing other males from reproducing. Our results suggest that there is selection on maintaining the mechanism of manipulation rather than maintaining sperm numbers. Taken with previous research on sexual conflict in N. cinerea, this study suggests that the causes and consequences of sexual conflict are complex and can change across the life history of an individual.

Sperm competition

Sperm competition

Sperm limitation and the evolution of extreme polyandry in honeybees (Apis mellifera L.)

Honeybee queens (Apis mellifera) show extreme levels of polyandry, but the evolutionary mechanisms underlying this behaviour are still unclear. The “sperm-limitation hypothesis”, which assumes that high levels of polyandry are essential to get a lifetime sperm supply for large and long-lived colonies, has been widely disregarded for honeybees because the semen of a single male is, in principle, sufficient to fill the spermatheca of a queen. However, the inefficient post-mating sperm transfer from the queen’s lateral oviducts into the spermatheca requires multiple matings to ensure an adequate spermatheca filling. Males of the African honeybee subspecies A. m. capensis have fewer sperm than males of the European subspecies A. m. carnica. Thus, given that sperm limitation is a cause for the evolution of multiple mating in A. mellifera, we would expect A. m. capensis queens to have higher mating frequencies than A. m. carnica. Here we show that A. m. capensis queens indeed exhibit significantly higher mating frequencies than queens of A. m. carnica, both in their native ranges and in an experiment on a North Sea island under the same environmental conditions. We conclude that honeybee queens try to achieve a minimum number of matings on their mating flights to ensure a sufficient lifetime sperm supply. It thus seems premature to reject the sperm-limitation hypothesis as a concept explaining the evolution of extreme polyandry in honeybees.

Sperm supply and egg fertilization in the ostrich (Struthio camelus).

We used egg break-out and spermatozoa trapped in the perivitelline layer of eggs to test the hypothesis that sperm supply and egg fertilization rate are high in the ostrich. Egg fertilization status was determined at break-out by the appearance of the germinal disc (GD) and then the perivitelline layer overlying the GD region was collected to count sperm (SpermOPVL) under fluorescence following staining with 4',6'-diamidino-2-phenyindole (DAPI). The study was carried out on commercial ostrich farms over two laying seasons. In the first year, 229 eggs from nine randomly chosen ostrich pens comprising pairs, trios (two females, one male) and larger groups were collected for 1 week of every month of laying. Eggs contained 253 +/- 18 SpermOPVL/mm2 of the GD (mean +/- SEM; range 0-1330). Egg fertilization rate averaged 89.4 +/- 3.4% and varied from 78.6 to 98.2% between pens. Month had no effect on sperm supply or egg fertilization status. Eggs from paired birds (sex ratio 1 : 1) had less sperm in the GD than the eggs from pens with a higher sex ratio. In the second year, 150 eggs from seven pens, each containing only one male and either one, two or three females, were studied for 2 weeks at the beginning (winter), middle (spring) and end (summer) of laying. Eggs contained 364 +/- 45 SpermOPVL/mm2 of the GD (range 0-2880). Season had no effect on sperm supply or egg fertilization. The number of SpermOPVL varied between pens, assumed to be due to variation between individual males. The number of SpermOPVL increased as the sex ratio increased only when very high-ranking males were excluded from the analysis. Egg fertilization rate was 94.4 +/- 3.1% but varied from 64.0 to 100% between pens. Egg fertilization was not affected by season or sex ratio. Low fertilization rates were observed in two pens and appeared related to the lack of synchrony between timing of laying and sperm production in the first, and lack of mating in the second pen. We conclude that ostrich flocks generally have high rates of egg fertilization and any infertility is associated with lack of sperm supply.

Fertility and paternity in the Eucalyptus snout-beetle Gonipterus scutellatus: females might benefit from sperm mixing

Mating in Gonipterus scutellatus is very long and lasts on average 6.98 ± 0.49 hr. This could be interpreted as a mechanism of male guarding, but males neither increase copulation duration nor ejaculate volume when sperm competition risk increases. We studied paternity patterns using RAPDs, and the influence of multiple matings on fertility, fecundity and sperm supply. Using twicemated females, we compared the percentage of polymorphic bands shared between first male/offspring, second male/offspring, mother/offspring, unrelated adults (males). In agreement with a previous study on paternity with the sterilemale technique, we found that sperm mixing seems the prevalent sperm competition mechanism. In a second experiment, adults were randomly assigned to three treatments: females mated only once; females allowed to mate ad libitum with one male; and females that could mate with seven different males. Females of the last group showed a significant increase in fertility. Additionally, we compared the stored sperm volumes among four groups: female whose copulation was interrupted after 15 min, those that mated once, twice or three times. This experiment indicates that sperm supply increases with the number of matings, excluding the possibility of sperm removal. These facts and the occurrence of sperm mixing might explain the lack of male response to increased male density in previous studies.

Interannual variability of sperm reserves and fecundity of primiparous females of the snow crab (Chionoecetes opilio) in relation to sex ratio

Demographics of adults and reproductive condition of primiparous (first brood) females of the snow crab (Chionoecetes opilio) were monitored annually from 1994 to 2002 at a fished site to investigate the possibility that sperm supply limits embryo production. Abundance of primipara fluctuated 533-fold because of a recruitment pulse, and this caused a large oscillation in the sex ratio of adult males to primipara. Annual mean of stored ejaculate weight (SL) and potential fecundity index (PF, clutch weight × percent fertilized eggs) adjusted to constant primipara carapace width ranged from 31 to 130 mg by spermatheca and from 1.97 to 3.43 g by clutch, respectively. Annual mean of SL and number of stored sperm (range 3.81 × 106 to 35.00 × 106 sperm by spermatheca) decreased when sex ratio decreased, probably because of a combined reduction of sperm allocation and female promiscuity. Annual mean PF was negatively correlated with abundance of small males, which may reflect egg losses during postoviposition matings. Although sociosexual context has a large impact on reproductive condition of primipara, the possibility that sperm supply limits embryo production could not be confirmed or excluded because of the complexity of snow crab mating behavior.