Sperm transfer during mating in the pharaoh's ant, Monomorium pharaonis

Abstract.  Sperm transfer in the pharaoh's ant Monomorium pharaonis (L.) is studied by making longitudinal sections through the gasters of mating pairs fixed in copula. Sperm is transferred inside a spermatophore similar to those found in two other ants, Diacamma sp. from Japan and Carebara vidua . Sharp teeth-ridges are present on the penis valves and, during copulation, these teeth make contact with a thick and soft cuticular layer covering the bursa copulatrix. This ensures an attachment long enough for the successful transfer of the spermatophore to the right position inside the female oviduct. The thick cuticle also protects the queen from serious damage by the male's sharp claspers. After a first successful copulation, sperm is still present inside the male's seminal vesicles, suggesting that males can mate multiply. Additional experiments, where single, initially virgin males are presented to several virgin females, confirm this.     

Multiple mating and lifetime reproductive output in female dobsonflies that receive nuptial gifts

In mating of the dobsonfly, Protohermes grandis (Thunberg), the male attaches the spermatophore externally to the female genitalia. The spermatophore includes a large gelatinous mass which the female detaches and feeds on after mating. While the female consumes this nuptial food gift, sperm is evacuated from the remaining portion of the spermatophore (sperm package) into her reproductive tract. Under laboratory conditions, mated females maintained receptivity throughout their lifetime, and they remated even on the day following copulation. A single insemination may supply enough sperm, as females mated only once deposited fertile eggs throughout life and, when dissected after death, all females had sperm in the spermatheca. There was a positive correlation between longevity and the number of matings. Lifetime fecundity also increased as mating multiplied. However, the size of eggs and hatchlings was not influenced by the number of matings. It seems that large spermatophore consumption by female P. grandis provides nutrients that increase fitness not in offspring quality, but in their quantity.     

Chonopeltis australis (Crustacea) male reproductive system morphology; Sperm transfer and review of reproduction in Branchiura

The morphology of the male reproductive system as well as sperm transfer in Branchiura has been described for Dolops ranarum and Argulus japonicus. In this study, the reproductive system and accessory structures are described for male Chonopeltis australis using histology, light microscopy, and scanning electron microscopy. For the first time, we describe sperm transfer by means of a spermatophore in this genus. The internal and external morphology and mechanism of sperm transfer is compared with other Branchiura, where it has been described. The morphology of the reproductive system of C. australis is similar to that of D. ranarum while the accessory structures and the spermatophore produced are similar to that of A. japonicus. A revision of the definition of Branchiura with respect to reproduction is provided. J. Morphol. 276:209–218, 2015. © 2014 Wiley Periodicals, Inc.     

Sperm transfer by spermatophore in Diptera: new results from the Diopsidae

Sperm transfer by spermatophore is reported as a common and possibly primitive feature of the Diopsidae (Diptera, Schizophora). Spermatophores occur in four out of five investigated genera, in Cyrtodiopsis, Diasemopsis, Teleopsis , and in Sphyracephala , which is positioned close to the base of the family. Within the genus Diopsis the spermatophore is subject to reduction. Spermatophore size and copulation duration are positively correlated across the species. This is only partially explained by the time requirement of sperm transfer. Parsimony in time and material seems to be favoured in species with high mating frequency at special aggregation sites, whereas high investment in time and material occurs in species that do not mate preferentially at certain times or locations. The utilization of spermatophores has strong implications on the possibilities of sperm competition and cryptic female choice and may account for the occurrence of a postcopulatory passive phase or prolonged mating in some species. The increasing number of records of spermatophores in Diptera is reviewed.     

Sperm stratification and paternity success in red flour beetles

Abstract. When females are inseminated by multiple males, male paternity success (sperm precedence) is determined by the underlying processes of sperm storage and sperm utilization. Although informative for many questions, two-male sperm competition experiments may offer limited insight into natural mating scenarios when females are likely to mate with several males. In this study, genetic markers in Tribolium castaneum are used to trace paternity for multiple sires, and to determine whether displacement of stored sperm that occurs after a third mating equally affects both previous mates, or if fertilizations are disproportionately lost by the female's most recent mate. For 20 days after triple-matings, first males retain significantly higher paternity success (relative to first male paternity in double-matings) compared with second males. These results demonstrate that when females remate before sperm mixing occurs, sperm stratification results in differential loss of sperm from the most recent mate. This study provides insight into the mechanisms underlying sperm precedence in a promiscuous mating system, and suggests that T. castaneum females could limit paternity success of particular mates by remating with more highly preferred males.     

黑玛丽精子包特性及pH和温度对其精子活力的影响

通过研究黑玛丽Poecilia latipinna精子包破裂的过程和影响因素、精子运动的情况及影响因素,结果发现,当精液用Hank’s平衡盐溶液(HBSS)稀释约5 min后精子包开始破裂,约12 min后全部破裂。释放出的精子暂时处于休眠状态,约50 min后,处于HBSS稀释液中的精子会被激活。应用计算机辅助精子分析系统对黑玛丽精子在不同pH和不同温度下HBSS中的精子运动百分数、运动时间和平均运动速率进行观察。在pH7~8的中性或弱碱性溶液中,精子运动活力较强;而在酸性(pH<7)或碱性较强(pH>9)的溶液中,精子的运动活力都会降低。在不同温度下的HBSS中精子的活力不同,精子在低温(4℃)条件下的运动时间显著长于在室温(20℃)条件下,但运动速度较慢。本研究初步探讨了黑玛丽的精子包特性以及pH和温度对精子运动活力的影响,旨在对黑玛丽等卵胎生鱼类的人工授精,以及生殖生物学特性等的研究提供更丰富的基础资料。     

Sperm size of African cichlids in relation to sperm competition

We compared pairs of closely related taxa of cichlid fishesfrom Lake Tanganyika to examine the relationship between spermsize and the presumed intensity of sperm competition. In contrastto previous reports of relatively short sperm in polygamousfishes across a variety of taxa, we found that polygamous cichlidshad significantly longer sperm than their closest monogamousrelatives. In addition, sperm length was significantly relatedto relative testis size (controlling for body size and phylogeny).The site of fertilization may also be correlated with spermlength, as species that fertilize in the female's buccal cavityhad significantly shorter sperm than those that fertilizedeggs on the substrate. Assuming that relatively large testesand polygamous mating are indicative of more intense sperm competition, these results indicate that sperm length is related to the intensityof sperm competition in this clade of cichlids, as has beenfound previously in insects, birds, and mammals.     

Sperm transfer mechanisms: some correlates and consequences

Abstract

The methods by which the Metazoa bring their gametes into juxtaposition as a preliminary to fertilisation are reviewed. The method of sperm transfer employed by a particular organism or group of organisms is commonly more directly related to habitat than to phylogeny. This appears in part to be a consequence of certain methods of sperm transfer facilitating the exploitation of particular habitats. Non-exposure of sperm to hostile influences such as fresh water, digestive enzymes, antibodies, or the desiccating effects of air may have been important in the colonisation of fresh waters by animals with body fluids of high osmolarity, in the establishment of the endoparasitic habit, and in the colonisation of dry land. Mutual exchange of sperm with equal sharing of the reproductive burden by means of hermaphroditism, coupled with internal fertilisation, is seen as an important adaptation to very small body size, especially as associated with life in interstitial habitats. Efficient transfer of sperm, usually in conjunction with internal fertilisation, is seen as a prerequisite for the development of yolky eggs with fairly direct development of the young. It is also a prerequisite for establishing maternal nourishment of the young in viviparity and a consequent reduction or suppression of free larval stages. Yolky eggs confer freedom from the vicissitudes of fluctuation in larval food supplies, and eggs which contain all or most of the mineral salts required for development seem necessary for colonisation of fresh waters. Amongst freshwater fishes and anurans, close pairing of male and female minimises the effects of rapid destruction of sperm in species which do not copulate or use spermatophores.     

Sperm precedence in the dragonfly Erythemis simplicicollis

Females of the dragonfly Erythemis simplicicollis (Say) (Odonata, Libellulidae) store enough sperm to fertilize 6–13 clutches of eggs laid on consecutive days. Nonetheless, they usually mate one or more times per day. Males wait for females at ponds containing surface vegetation on which the females lay eggs. Some males defend vegetation while other act as satellites. After mating, both types of males attempt to guard females against takeover by other males. Sperm precedence by male E. simplicicollis was studied using sterility produced by gamma irradiation to label sperm. After a dose-response analysis, males receiving a dose of 25 kiloroentgens (>99.9% sterile) were returned to their home pond as territory residents and satellites. Both types of males fertilized an average of 99.5% (range 97.3–100%) of the female's remaining clutch. After mating with a sterile male, females were isolated in a large cage, and eggs collected for several consecutive days. These clutches revealed that sperm mixing in the bursa of the females is essentially complete after 24 to 48 h and that the last male to mate had replaced an average of more than 57–75% of the sperm stored by female from previous matings. Thus, the last sperm in is the first sperm out fertilizing essentially all of the eggs laid soon (5–6 min) after the mating. Sperm from the most recent mating competes for fertilizations with sperm stored from previous matings only if the female oviposits on the following day without remating.     

Sperm structure and spermiogenesis in Atelura formicaria Heyden (Zygentoma, Insecta)

The spermatozoon of Atelura formicaria (Zygentoma) shows several features that are typical of insects: an apical acrosome, an elongated dense nucleus, a centriole with expanded centriolar adjunct material, two large mitochondrial derivatives, and two thin accessory bodies located beneath the nucleus. The axoneme exhibits a 9 + 9 + 2 pattern with accessory tubules formed by 16 protofilaments and intertubular material. However, spermatozoa of A. formicaria show some remarkable features. The sperm cell is short for an insect, being only 50 µm in length. The nucleus is characterized by the presence of two lateral grooves which are filled with numerous infoldings of the nuclear envelope. In a cross-section the chromatin has the configuration of the Leonardo da Vinci's 'Vitruvian man'. Each mitochondrial derivative has a peculiar structure with peripheral cristae and four crystalline bodies in its matrix; two of these crystalline bodies are large and have differently orientated cristal planes. At the end of spermiogenesis, sperm bundles are stored in the proximal part of the testes. Secretions from the epithelial wall of this region give rise to large globular structures. These include sperm bundles intermingled with dense granules, forming the so called 'spermatolophids'. These formations descend along the deferent duct and are stored in the expanded seminal vesicle. Atelura spermatozoa do not pair as in some Lepismatidae, nor do they fuse as in Tricholepidion (Lepidotrichidae). Thus, sperm aggregation in Zygentoma is realized according to different modalities and can hardly be considered as a synapomorphic trait of its subtaxa.     

Sperm competition and brain size evolution in mammals

The ‘expensive tissue hypothesis’ predicts a size trade‐off between the brain and other energetically costly organs. A specific version of this hypothesis, the ‘expensive sexual tissue hypothesis’, argues that selection for larger testes under sperm competition constrains brain size evolution. We show here that there is no general evolutionary trade‐off between brain and testis mass in mammals. The predicted negative relationship between these traits is not found for rodents, ungulates, primates, carnivores, or across combined mammalian orders, and neither does total brain mass vary according to the level of sperm competition as determined by mating system classifications. Although we are able to confirm previous reports of a negative relationship between brain and testis mass in echolocating bats, our results suggest that mating system may be a better predictor of brain size in this group. We conclude that the expensive sexual tissue hypothesis accounts for little or none of the variance in brain size in mammals, and suggest that a broader framework is required to understand the costs of brain size evolution and how these are met.     

Sperm limitation affects sex allocation in a parasitoid wasp Nasonia vitripennis

Insect reproduction is influenced by various external factors including temperature, a well-studied constraint. We investigated to what extent different levels of sperm limitation of males exposed to different heat stresses (34 and 36℃) afFect fem ales' offspring production and sex allocation in Nasonia vitripennis. In this haplodiploid parasitoid wasp attacking different species of pest flies, we investigated the effect of the quantity of sperm females received and stored in their spermatheca on their sperm use decisions, hence sex allocation, over successive ovipositions. In particular, we compared the sex allocation of females presenting three levels of sperm limitation (i.e.,mated with control, 34 ℃ heat-stressed or 36℃heat-stressed males) on each host they parasitized. To disentangle the potential reduction of sperm quality after a heat stress exposure from that of sperm quantity, we also explored the clutch size and sex ratio produced by fem ales that were partially sperm limited after copulating with multiply mated males. Independently of their sperm numbers, all types of fem ales produced a similar total number of offspring, but the more limited ones had fewer daughters. Sperm limitation further affected the distribution of daughters' production across time.In addition to constraints acting on female physiology, male fertility should therefore be considered in studies measuring reproductive outputs of insects submitted to heat stresses.     

Heterosexual raping in the mole crab,Emerita asiatica

A peculiarity in the mating habit of E. asiatica resulting in deposition of spermato-phores on immature females has been described and interpreted as heterosexual raping. Pheromonal attraction of the male is apparently not involved, the copulation being indiscriminate.     

Sperm competition and the evolution of testes size in birds

Comparative analyses suggest that a variety of ecological and behavioural factors contribute to the tremendous variability in extrapair mating among birds. In an analysis of 1010 species of birds, we examined several ecological and behavioural factors in relation to testes size; an index of sperm competition and the extent of extrapair mating. In univariate and multivariate analyses, testes size was significantly larger in species that breed colonially than in species that breed solitarily, suggesting that higher breeding density is associated with greater sperm competition. After controlling for phylogenetic effects and other ecological variables, testes size was also larger in taxa that did not participate in feeding their offspring. In analyses of both the raw species data and phylogenetically independent contrasts, monogamous taxa had smaller testes than taxa with multiple social mates, and testes size tended to increase with clutch size, which suggests that sperm depletion may play a role in the evolution of testes size. Our results suggest that traditional ecological and behavioural variables, such as social mating system, breeding density and male parental care can account for a significant portion of the variation in sperm competition in birds.     

Sperm Competition and Optimal Timing of Matings in Microcebus murinus

Female promiscuity is common in mammals and leads to sperm competition: the sperm of ≥2 males compete for ova. Scientists understand the possible role of optimal insemination periods for male reproductive success in many species as well as the impact of monopolization of receptive females. Information from experiments combined with detailed observations from the field that allow determining the relative impacts of the elements in the same species are rare. We studied sperm competition and the role of optimal insemination periods in gray mouse lemurs (Microcebus murinus), a small solitary nocturnal primate from Madagascar. We used controlled matings to identify the relative impact of both contest and scramble competition, which characterize their mating system, on paternity. Fifteen females mated with 3–6 males in quick succession. Our experiments revealed that the optimal insemination period is during early receptivity. Early but not first mating males are more likely to sire offspring. Comparison with our field data indicate that the timing of male monopolization efforts correspond with the optimal insemination period.     

Spermatophore transfer in the hermit crab Clibanarius vittatus (Crustacea,Anomura, Diogenidae)

Although mating has been described in several hermit crab species, the mechanics of spermatophore transfer have not previously been demonstrated. Evidence from pleopod and gonopore morphology, video observations, and inseminated females indicates that in Clibanarius vittatus the male applies a spermatophoric mass directly onto the female via the gonopores rather than with modified pleopods 1-2 (gonopods) and/or genital papillae as in many other decapods. The single second pleopod of males of C. vittatus has a simple endopod with no apparent modifications for sperm transfer. There are no genital papillae extending from the male gonopores. The globular spermatophores are aligned in rows surrounded by a seminal secretion in the male ducts (vasa deferentia that terminate in ejaculatory ducts opening to the exterior via the gonopores). During copulation, described from time-lapse video recordings, the ventral surface of the last thoracic segment of the male, bearing the gonopores, was apposed to the ventral cephalothorax of the female. A massive amount of seminal secretion containing spermatophore ribbons, termed here the spermatophoric mass and described for the first time in a hermit crab species, was observed covering the sternites and coxae of pereopods 1-5 of a recently copulated female. It is suggested that during copulation the male emits the contents of the ejaculatory ducts directly onto the female without the aid of gonopods or genital papillae. Although spermatophore transfer is simple in C. vittatus, the presence of modified anterior pleopods or elongate genital papillae (sexual tubes) in other paguroidean species suggests the possibility of a more complex insemination process in these other hermit crabs.