Successful Sperm Transfer Research Articles

Virgin queen behaviour and controlled mating in the stingless bee Tetragonulacarbonaria (Meliponini)

Improving knowledge of virgin queen behaviour and mating biology in stingless bees (Meliponini) is an important step towards artificial selection programmes for managed colonies. Here we study the Australian stingless bee Tetragonulacarbonaria to (1) describe the behaviour of queens from eclosion until egg-laying, and (2) assess whether young queens can be reared and mated under constrained conditions. We extracted mature virgin queen cells of T.carbonaria from large colonies and reared them in queen maturation boxes containing a limited number of workers (“micro-colonies”). Queen behaviour followed a typical pattern with three phases: a period of high activity and wing-flapping on top of the brood (5 ± 2 days of age), attempts to leave the colony for the nuptial flight (12 ± 3 days of age), and oviposition (20 ± 6 days of age). In total, 71% (68 of 95) of queen cells hatched in our maturation boxes and 57% (39 of 68) survived to mating age, with some observed to be actively killed by workers within the first week of life (8 of 68; 11%). For a subset of our queens, we performed controlled matings (either with or without CO2 narcosis) by presenting constrained females to males in mating aggregations, allowing one male to mate (deposit mating plug) and then returning queens to their box. In the absence of CO2 narcosis, 30% of queens mated this way were subsequently found to have sperm in their spermathecae, indicative of a successful mating (5 of 17). The remaining 70% however contained no sperm, despite the presence of the male mating plug. Amongst queens that were CO2 narcotized before and during the controlled mating, none had sperm in their spermathecae (0 of 12), though most went on to activate their ovaries following the mating and lay male (haploid) eggs. Together, these trials indicate that controlled matings with T.carbonaria are possible, but suggest that queens may need to actively accept mating for successful sperm transfer.

Mate competition during pseudocopulation in shipworms.

Shipworms are predominantly wood-eating bivalves that play fundamental roles in biodegradation, niche creation and nutrient cycling across a range of marine ecosystems. Shipworms remain confined to the wood they colonize as larvae; however, continual feeding and rapid growth to large sizes degrade both food source and habitat. This unique lifestyle has led to the evolution of a stunning diversity of reproductive strategies, from broadcast spawning to spermcasting, larval brooding and extreme sexual size dimorphism with male dwarfism. Some species also engage in pseudocopulation, a form of direct fertilization where groups of neighbouring individuals simultaneously inseminate one another via their siphons-the only part of the animal extending beyond the burrow. Among the Bivalvia, this exceptionally rare behaviour is unique to shipworms and remains infrequently observed and poorly understood. Herein, we document pseudocopulation with video footage in the giant feathery shipworm (Bankia setacea) and novel competitive behaviours, including siphon wrestling, mate guarding and the removal of a rival's spermatozoa from the siphons of a recipient. As successful sperm transfer is likely greater for larger individuals with longer siphons, we suggest that these competitive behaviours are a factor selecting for rapid growth and large size in species that engage in pseudocopulation.

Mating success of male guppy Poecilia reticulata in the wild

To understand how the diversity among male sexual traits is maintained despite directional female choice for attractive traits, it is important to study male reproductive success in each reproductive episode. Male reproductive success is indeed the comprehensive result of several processes such as mate choice, mating, and fertilization. In this study, male mating success was estimated in a wild guppy Poecilia reticulata population of Hiji River, Okinawa Island, in southern Japan. The mating success of males was estimated as the percentage of sperm transferred in relation to the total sperm reserve. In a preliminary experiment, it was confirmed that the sperm reserves of males were partly replenished after 12 h and fully replenished after 72 h, when all sperm were released. In addition, the results of investigation in the wild population revealed that approximately 20% of males had no sperm reserves at all, although their sperm reserves should have been replenished by sexual isolation. Male sexual traits such as body size or color pattern did not affect the percentage of sperm transferred. Results from this study provide important insights into male sperm transfer ability and sperm production in this population. However, the high frequency of male sperm-transfer success estimated in this study should to be taken with caution, and whether it is due to differences between wild and laboratory conditions, sex ratio or the rates of multiple matings by females in the wild population remain to be fully explored.

A unique mating pattern of Panorpodes kuandianensis (Mecoptera: Panorpodidae)

Sexually reproductive insects exhibit diverse mating behaviors. However, the mating pattern remains unknown for Panorpodes of Panorpodidae to date. In this study, we investigated the mating behavior and copulatory mechanism of the short-faced scorpionfly Panorpodes kuandianensis Zhong, Zhang and Hua, 2011 for the first time. The results show that the male provides a salivary mass as a nuptial gift to the female and starts to copulate with the female in a V-shaped position, then changes to an end-to-end position by temporarily twisting the female abdominal segments VII−IX by 180°. During mating the basal processes and the basal teeth of the gonostyli and the hypandrium are used to obtain copulation and sustain the coupling of genitalia to secure successful sperm transfer. This unique mating pattern is greatly different from that of other Mecoptera reported and is likely evolved as an adaptation in the context of sexual conflict.

One size fits all? Determinants of sperm transfer in a highly dimorphic orb-web spider.

The evolutionary significance of widespread hypo-allometric scaling of genital traits in combination with rapid interspecific genital trait divergence has been of key interest to evolutionary biologists for many years and remains poorly understood. Here, we provide a detailed assessment of quantitative genital trait variation in males and females of the sexually highly dimorphic and cannibalistic orb-weaving spider Argiope aurantia. We then test how this trait variation relates to sperm transfer success. In particular, we test specific predictions of the one-size-fits-all and lock-and-key hypotheses for the evolution of genital characters. We use video-taped staged matings in a controlled environment with subsequent morphological microdissections and sperm count analyses. We find little support for the prediction of the one-size-fits-all hypothesis for the evolution of hypo-allometric scaling of genital traits, namely that intermediate trait dimensions confer highest sperm transfer success. Likewise, our findings do not support the prediction of the lock-and-key hypothesis that a tight fit of male and female genital traits mediates highest sperm transfer success. We do, however, detect directional effects of a number of male and female genital characters on sperm transfer, suggesting that genital trait dimensions are commonly under selection in nature. Importantly, even though females are much larger than males, spermatheca size limits the number of sperm transferred, contradicting a previous hypothesis about the evolutionary consequences of genital size dimorphism in extremely size-dimorphic taxa. We also find strong positive effects of male body size and copulation duration on the probability of sperm transfer and the number of sperm transferred, with implications for the evolution of extreme sexual size dimorphism and sexual cannibalism in orb weavers.

Chemical caressess: geographical variation of male sexual signals in a Neotropical scorpion

Differences in sexual signals among species are common, and may influence mate recognition and reproductive isolation. In scorpions, behavioural mechanisms and other sexual signals involved in mate selection and reproductive isolation have been scarcely studied. In this paper, we compare different male sexual signals between two distant populations of the scorpionBothriurus bonariensis, one located in Uruguay and the other in Central Argentina. We compare sexual behaviours from intra-populations and inter-populations matings. In addition, we extent this comparison to the secreted compounds and morphology of the exocrine glands located on the dorsal side of the telson in this species. Males ofB. bonariensisperformed stimulatory behaviours to the female with different frequency of occurrence and duration in the two populations. Chemical analyses of the glandular extracts showed that Uruguayan males present compounds which are absent in males of Argentinian population. In addition, we observed that in inter-population matings, stimulatory behaviours had intermediate patterns to intra-population matings. However, males failed to achieve a successful sperm transfer with females of different population. Mechanisms of sexual isolation between these two distant populations ofB. bonariensisapparently seem to have evolved due to divergence in allopatry. The differences in stimulatory levels during courtship between the two populations studied here give evidence for an early behavioural divergence promoted by sexual selection.

Copulatory behavior in a pholcid spider: males use specialized genitalic movements for sperm removal and copulatory courtship

Sexual selection may operate on pre-copulatory, copulatory, and post-copulatory traits. An example of a copulatory target of sexual selection is the genitalic movements a male performs during copulation. These movements may function either to prevent sperm competition or to influence a female's fertilization decision. Here we investigated how copulation duration, pedipalp movements, and abdominal movements that males of the pholcid spider Holocnemus pluchei produce during copulation influence sperm removal and/or patterns of successful sperm transfer. We compared mating events with virgin and mated females for differences in copulatory and post-copulatory behavior. We expected longer copulation duration, longer pedipalp movement duration, and more complex and frequent pedipalp and abdominal movements when males mated with mated females compared to virgin females. Except for abdominal movements, our results corroborated these predictions. Furthermore, when we investigated mating events with mated females, we observed sperm mass ejection from the female gonopore and physical removal of sperm by males' procursi. Females with interrupted second mating events showed a significant reduction of stored sperm masses compared to females with completed mating events. We suggest that males use alternating pedipalp movements to remove most of the rival sperm stored by mated females prior to sperm transfer. Copulation duration and pedipalp movements can be further used to transfer sperm and/or as a form of genitalic copulatory courtship.

Give ‘til it hurts: trade‐offs between immunity and male reproductive effort in the decorated cricket, Gryllodes sigillatus

Trade-offs between life-history variables can be manifested at either the phenotypic or genetic level, with vastly different evolutionary consequences. Here, we examined whether male decorated crickets (Gryllodes sigillatus) from eight inbred lines and the outbred founder population from which they were derived, trade-off immune effort [lytic activity, phenoloxidase (PO) activity or encapsulation] to produce spermatophylaxes: costly nuptial food gifts essential for successful sperm transfer. Canonical correlation analysis of the outbred population revealed a trade-off between spermatophylax mass and lytic activity. Analysis of our inbred lines, however, revealed that although PO activity, encapsulation, body mass, spermatophylax mass and ampulla (sperm capsule) mass were all highly heritable, lytic activity was not, and there was, therefore, no negative genetic correlation between lytic activity and spermatophylax mass. Thus, males showed a phenotypic but not a genetic trade-off between spermatophylax mass and lytic activity, suggesting that this trade-off is mediated largely by environmental factors.

Genital shape correlates with sperm transfer success in the praying mantis Ciulfina klassi (Insecta: Mantodea)

The rapid divergence of male genitalia is a widely observed evolutionary phenomenon. Although sexual selection is currently regarded as providing the most likely driving force behind genital diversification, the mechanisms responsible are still debated. Here, we investigate the relationship between male genital morphology and sperm transfer in the praying mantid Ciulfina klassi using geometric morphometrics. The shape of male genitalia in C. klassi influenced sperm transfer duration and the number and proportion of sperm transferred, suggesting that genital morphology is under sexual selection in this species. Genital size however was not correlated with any aspect of sperm transfer. Intriguingly, two of the major genital shape components correlated positively with the number of sperm transferred, but negatively with sperm transfer duration. Hence, males that most effectively transfer sperm to the female spermatheca do so in a relatively short period of time. A direct negative relationship was also found between sperm transfer duration and sperm transfer success. Overall, our study suggests that the variable genital shape of Ciulfina may have been selected for more efficient sperm transfer.

Determinants of mating and sperm‐transfer success in a simultaneous hermaphrodite

The number of mating partners an individual has within a population is a crucial parameter in sex allocation theory for simultaneous hermaphrodites because it is predicted to be one of the main parameters influencing sex allocation. However, little is known about the factors that determine the number of mates in simultaneous hermaphrodites. Furthermore, in order to understand the benefits obtained by resource allocation into the male function it is important to identify the factors that predict sperm-transfer success, i.e. the number of sperm a donor manages to store in a mate. In this study we experimentally tested how social group size (i.e. the number of all potential mates within a population) and density affect the number of mates and sperm-transfer success in the outcrossing hermaphroditic flatworm Macrostomum lignano. In addition, we assessed whether these parameters covary with morphological traits, such as body size, testis size and genital morphology. For this we used a method, which allows tracking sperm of a labelled donor in an unlabelled mate. We found considerable variation in the number of mates and sperm-transfer success between individuals. The number of mates increased with social group size, and was higher in worms with larger testes, but there was no effect of density. Similarly, sperm-transfer success was affected by social group size and testis size, but in addition this parameter was influenced by genital morphology. Our study demonstrates for the first time that the social context and the morphology of sperm donors are important predictors of the number of mates and sperm-transfer success in a simultaneous hermaphrodite. Based on these findings, we hypothesize that sex allocation influences the mating behaviour and outcome of sperm competition.

Male control of copulation duration in Ciulfina praying mantids (Insecta Mantodea)

While copulation serves primarily to allow the transfer of male gametes, the duration of copulation often exceeds that required for successful sperm transfer. One path to elucidate the processes occurring during prolonged copulations is to determine the extent of male and female influence over copulation duration. Here I address the issue of relative male and female influence over copulation duration using a cross-species mating experiment between three species of praying mantis from the genus Ciulfina. Male species identity significantly influenced copulation duration in interspecific crosses, whereas female species identity and the interaction between male and female identity had no such influence. These results show that males exhibit greater influence over copulation duration than females in Ciulfina praying mantids and shed light on some previously observed patterns of mating behaviour within this genus.

Mate Choice by Non‐Virgin Females Contributes to Reproductive Isolation between Populations of the Harlequin Beetle‐Riding Pseudoscorpion

AbstractDetermining whether reproductive isolation evolves through mate choice and/or gametic factors that prevent fertilization or through the post‐zygotic mechanisms of hybrid sterility or inviability is fundamental to understanding speciation. Investigation of the pre‐ and post‐zygotic components of reproductive isolation is facilitated in the pseudoscorpion, Cordylochernes scorpioides, by its indirect method of sperm transfer and viviparous embryonic development. Previous research on this species, in which mate discrimination was assessed in virgin females, suggested that female choice played only a minor role in reproductive isolation between populations from French Guiana and Panamá. Here, in a study of three allopatric populations of C. scorpioides from Panamá, we assessed mating‐stage isolation in both virgin and once‐mated females, and found that female discrimination depends critically on mating status. Virgin females were almost invariably receptive, showing no tendency to discriminate against males from allopatric populations. By contrast, non‐virgin females were significantly more likely to reject foreign males than males from their own population. Male sexual motivation could not account for differences in either female sexual receptivity or male success in sperm transfer. Allopatric and sympatric males did not differ in number of spermatophores deposited as either a female’s first or second mate. Nonetheless, allopatric males achieved significantly lower sperm transfer success not only with choosy, non‐virgin females but also with virgin females. Given the lack of behavioral discrimination by virgin females, female receptivity was not the only factor influencing differences in sperm transfer success. Multivariate analysis of spermatophore morphology suggests that the higher failure rate of matings between allopatric males and virgin females resulted from population differences in sperm packet architecture. Overall, our findings indicate that assessment of discrimination against allopatric males that is limited to virgin females may seriously underestimate the contribution of female mate choice to reproductive isolation between populations.

Fine structure of the male reproductive ducts, vagina and seminal receptacle of Cyathocephalus truncatus (Cestoda: Spathebothriidea)

Fine structure of the vas efferens, vas deferens, ejaculatory duct with accessory glands and vagina with seminal receptacle is described in the spathebothriidean tapeworm, Cyathocephalus truncatus (Pallas, 1781) Kessler, 1868. The numerous well-developed prostate glands are characterised by having secretory granules with an electron-dense core surrounded by a matrix of lower electron density. Coalescence of the outer part of the granules with each other takes place in the terminal end of the secretory ducts. The position of prostate glands around the proximal part of the cirrus pouch and terminating in the ejaculatory duct is a characteristic feature of the Spathebothriidea. Up to 20 closely arranged muscle layers make up the muscular cirrus pouch wall with 4 well-developed muscular layers in the ejaculatory duct and cirrus. Both the cirrus and the vagina are covered with the same uniform cone-shaped microtriches. The vagina has an extensive seminal receptacle. All of these structures are well-adapted to insure successful sperm transfer involving ejaculation and storage, probably for both self- and cross-insemination. Cyathocephalus truncatus has a cirrus similar to that of the monozoic, progenetic caryophyllidean, Archigetes sieboldi and well-developed prostate glands like those of the polyzoic pseudophyllidean, Diphyllobothrium latum. The ultrastructural aspects of the male and female reproductive system of C. truncatus are compared with those of other tapeworms.

Fertilization Success without Anterior Pleopods in Lysmata Wurdemanni (Decapoda: Caridea), a Protandric Simultaneous Hermaphrodite

Abstract The modifications of the first two pleopods in male shrimp have long been considered to serve in insemination of the female. The role of pleopods 1 and 2 in mating in a protandric simultaneous hermaphroditic shrimp, Lysmata wurdemanni, were investigated. Results indicate that the modified endopod of pleopod 1 is not needed to transfer sperm in both male-phase (MP) and euhermaphrodite-phase (EP) shrimp. Absence of pleopod 2 does not affect the sperm-transfer success in both MP and EP shrimp. Removal of pleopod 1 also has no impact on fertilization in the MP shrimp; however, sperm transfer is affected by removal of pleopod 1 in some EP shrimp. Even when both pleopods 1 and 2 are completely ablated, about 20% of the shrimp can still fertilize successfully and another 20% partially successfully.

Effect of Rival Males on the Courtship of Paedomorphic and Metamorphic Triturus alpestris (Amphibia: Salamandridae)

Current theories on the alternative mating tactics suppose that individuals may opt for particular behavioral patterns depending of their morphological status. Facultative paedomorphosis in newts and salamanders is a suitable process to explore this question because it implies the coexistence of two different morphological morphs differing by the presence of gills and epigamic traits. The aim of this study was to find out whether paedomorphs and metamorphs use similar tactics to attract mates in the presence of a rival and whether there are differences in sexual activity and success between alternative morphs. Sexual interactions in triadic encounters were staged and analyzed in a standardized experimental design. The two kinds of males did not differ in terms of sexual activity, spermatophore deposition or female responsiveness. Both rival paedomorphic and metamorphic males exhibited sexual interference, but in most encounters, intruders just disturbed the courting pair. Sperm transfer success was lower in triadic encounters than in dyadic encounters. These results illustrate that intermorph breeding also occurs in the presence of competitors but that the success rate of the newts is considerably decreased in such competitive situations. Moreover, newts do not use alternative reproductive tactics depending on their status (i.e., paedomorph or metamorph).

Relationship Between Size and Mating Success in the Blow Fly <I>Phormia regina</I> (Diptera: Calliphoridae)

Size variation occurs in natural populations of the black blow fly, Phormia regina (Meigen); head width varied from 2.25 and 1.89 mm to 3.68 and 3.72 mm for males and females, respectively. Using these values as a guide, small flies were produced in the laboratory by early removal of larvae from the rearing medium. Mating experiments, pairing flies of various size categories, showed that when small males mated with large females the percentage of successfully inseminated females was significantly reduced compared with the other combinations (42% versus 73–89%). Previous work led us to suspect that small males might have small aedeagi and therefore have a problem in successful sperm transfer when they mate with large females. Measurement of aedeagus size and head width showed that in wild flies the size of the aedeagus is positively correlated with body size.

Sexually Selected Genital Adornment and Sperm Packaging in Species of Oreochromis (Teleostei: Cichlidae)

Species of the tilapiine cichlid genus Oreochromis are female mouthbrooders. During the breeding season, males usually congregate in leks. They defend small territories around a spawning pit (bower, see McKaye et al., 1990) and, by their courtship behavior, try to attract females who move around in groups. Single females, ready to spawn, leave those groups and pay short visits to male territories. In spawning, the female drops a small number of eggs, which she then takes into her mouth well before the male ejects sperm. Eggs are rarely fertilized while on the bottom but essentially within the mouth of the female who picks up sperm from the genital papilla of the male while he ejaculates. Examples include O. mossambicus (Baerends and Baerends-van Roon, 1950), 0. karomo and 0. variabilis (Lowe, 1956), and 0. macrochir (Ruwet, 1963). Females usually move from one spawning pit to another, having one brood of eggs fertilized by several males. The number of eggs that a male fertilizes thus depends on the number of females that come to his bower; successful sperm transfer; and possible sperm competition within the mouth of a female who visits several males in succession.

UTILIZATION AND DEGREE OF DEPLETION OF EXOGENOUS SPERM IN THREE HERMAPHRODITIC SEA HARES OF THE GENUS APLYSIA (GASTROPODA: OPISTHOBRANCHIA)

Two series of experiments were conducted to examine the utilization of exogenous sperm and their degree of depletion in three hermaphroditic sea hares, Aplysia kurodai Baba, 1937, A. Juliana Quoy & Gaunard, 1832, and A. parvula Guilding in MOrch, 1863. The first series of experiments was designed to determine whether one mating is enough for female partners to receive sufficient sperm to fertilize at least one egg mass. For this purpose, isolated individuals were mated as females once with conspecific individuals and the viability of their subsequent eggs was examined. When successfully inseminated, individuals of all the three species received enough sperm to fertilize at least one egg mass, and they continued to lay 3.6–8.5 viable egg masses. However, 10–36% of the matings by these sea hares did not result in any viable egg production by the female partner, indicating that these matings did not involve sperm transfer Such matings without sperm transfer tended to be shorter than matings with successful sperm transfer The second experimental series was conducted to examine whether sperm depletion actually occurs or not in field-caught adults. For this purpose, adult individuals caught in the field were allowed to lay eggs under isolated conditions without mating All the individuals of A. kurodai and A. juliana stored enough sperm to fertilize at least one egg mass. However, in A. parvula, 23–33% of individuals laid egg masses containing non-viable eggs at their first spawning after isolation, indicating that these individuals were depleted in exogenous sperm

Extra-pair paternity in monogamous tree swallows

Abstract. Multilocus DNA fingerprinting of offspring of monogamous pairs of tree swallows, Tachycineta bicolor, revealed that 50% (8/16) of broods contained young sired by extra-pair males, totalling 38% (33/86) of all offspring analysed. No young resulted from intraspecific brood parasitism. The distribution of extra-pair paternity showed a bimodal pattern; either none or many illegitimate young per brood. Thirty-three per cent of illegitimate offspring were sired by three to five nearest male neighbours. Females copulated frequently with their own mate at their own box, but they were never seen copulating with other males. Hence, there was a striking contrast between the rate of extra-pair copulation and the rate of extra-pair fertilization. There was no relationship between the pair copulation rate and the proportion of illegitimate young in a brood, suggesting that males cannot use the number of copulations performed with their mate as a reliable cue to their share of paternity. Males provisioned their young at nearly the same rate as did females, and males with illegitimate offspring in their nest did not reduce provisioning effort compared to males with only legitimate offspring. Hence, females did not suffer any apparent costs of promiscuity. It is argued that females control the sperm transfer success of copulations. Because females do not receive anything other than sperm from extra-pair copulation, the promiscuous behaviour is probably driven by some genetic factors enhancing female fitness. Although the data presented seem consistent with female choice for male genetic quality, there were no detectable phenotypic characteristics of males with high fertilization success.

Sexual selection of body weight in Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

Female Sitophilus oryzae were found to prefer to mate with large males. Observations of the sexual behaviour revealed a male courtship behaviour which may be used by females to assess the size and vigour of courting males. Successful sperm transfer occurred only after pairing for 1 hr and yet insects sometimes remained paired for more than 3 hr. The significance of the results in relation to evolutionary pressures on individual insects is discussed.