Catalase and Uric Acid Prevent Morphological Damage to the Sperm Flagella of Colossoma macropomum During 96 Hours at Low Storage Temperatures

Oxidative stress is one of the main causes of loss of sperm function during chilled storage. The aim of the current study was to evaluate the effects of a fructose-based extender, which was supplemented with catalase or uric acid, on the motility, viability, morphological integrity, and lipid peroxidation (LPO) of Colossoma macropomum spermatozoa. Sperm was diluted in extenders containing catalase (0; 0.1; 0.8; and 1.5 kU/L) or uric acid (0; 0.25; 0.5; and 1.0 mmol/L) and then stored at 4.3 ± 0.6°C for 96 hours. The chilling storage time had more significant and pronounced effects on practically all the measured sperm quality parameters than the different concentrations of both antioxidants added to the extenders. This was true for sperm motility, motility duration, sperm viability, and the percentage of normal spermatozoa. In fact, for all these parameters, values were higher in the extenders supplemented with catalase or uric acid, than those not supplemented with these antioxidants, especially after 96 hours. The LPO process showed an antioxidant-dependent response. In catalase-supplemented extenders thiobarbituric acid reactive substance (TBARS) levels increased gradually and significantly with time, but remained stable during the 96 hours of chilled storage in all samples in which uric acid was added. Despite this, TBARS levels were lower in the extenders supplemented with both catalase and uric acid than in those not having these antioxidants. Inverse correlations were found between sperm motility and the damage in sperm flagella. Our findings suggest that the supplementation of an extender with catalase or uric acid is beneficial and protects fish sperm membranes from damage caused by oxidative stress during low-temperature storage. The extenders containing 0.1 kU/L of catalase and 0.25 mmol/L of uric acid provided effective antioxidant protection for the spermatozoa of this important Amazonian fish.

In Vitro Storage of Functional Sperm at Room Temperature in Zebrafish and Medaka

The longevity of sperm in teleost such as zebrafish and medaka is short when isolated even in saline-balanced solution at a physiological temperature. In contrast, some internal fertilizers exhibit the long-term storage of sperm, >10 months, in the female reproductive tract. This evidence implies that sperm in teleost possesses the ability to survive for a long time under suitable conditions; however, these conditions are not well understood. In this study, we show that the sperm of zebrafish can survive and maintain fertility in L-15-based storage medium supplemented with bovine serum albumin, fetal bovine serum, glucose, and lactic acid for 28 days at room temperature. The fertilized embryos developed to normal fertile adults. This storage medium was effective in medaka sperm stored for 7 days at room temperature. These results suggest that sperm from external fertilizer zebrafish and medaka has the ability to survive for at least 4 and 1 week, respectively, in the body fluid-like medium at a physiological temperature. This sperm storage method allows researchers to ship sperm by low-cost methods and to investigate key factors for motility and fertile ability in those sperm.

Multiple-brooding rockfishes (Sebastes spp.) can utilize stored sperm from individual sires to fertilize consecutive broods

Viviparous rockfishes (Sebastes spp., family Scorpaenidae) mate and store sperm in the ovaries for several months prior to fertilization, as oocytes develop for the parturition season. Although multiple paternity has been documented in single-brooding rockfishes, paternity in consecutive broods of multiple-brooding species has not been studied. Analyses of multilocus microsatellite genotypes in both residual larvae left in the ovary from a previous parturition and upcoming fertilized broods in the same ovary demonstrated evidence of the same sires in consecutive broods in chilipepper (Sebastes goodei) and speckled (Sebastes ovalis) rockfishes. One S. goodei mother showed evidence of multiple paternity from the same two sires in both consecutive broods. The ability to retain sperm, even after a parturition event, for use in subsequent broods, confers an advantage to ensure fertilization and allows for extension of the parturition season. This life-history strategy provides a bet-hedging advantage in the California Current system, an environmentally dynamic ecosystem where larval survivorship and subsequent recruitment to adult populations can vary temporally by orders of magnitude.

Loss of Avian Intromittent Organs as a Sperm Competition Strategy: A Race to Be Last

AbstractThe loss of the intromittent organ (IO) in the majority of birds remains unexplained. Here, I propose that IO loss results from sperm competition in the context of the unique avian sperm storage system. The first stage of fertilization is the movement of sperm through the vagina from the site of ejaculation to the sperm storage tubules (SSTs) at the uterovaginal junction. In a second stage, sperm are released from the SSTs and move through the uterus to the site of fertilization in the infundibulum. Last-male fertilization precedence can occur if sperm that arrive later at the uterovaginal junction occupy uterus-side SSTs, which then have a head start in the race to the infundibulum with each ovulation. Under such "last-in, first-out" conditions, there is strong sperm competition to arrive later at the SSTs. Consequently, the optimal male strategy would be placement of the ejaculate at the cloacal opening to allow any other sperm in the vagina to reach the SSTs first. Cloacal placement is effectively achieved by loss of the IO. The evolution of altricial development in Neoaves, the largest clade that lacks IOs, created conditions that favor IO loss. Specifically, the smaller clutch sizes and hatching asynchrony of altricial birds increase the intensity of sperm competition for fertilization of early eggs in the laying sequence and thus the selective advantage of later arrival at the SSTs. The rarity of IO loss among all animals suggests that the complex mechanism of avian fertilization creates unique conditions for sperm competition.

Selection on sperm size in response to promiscuity and variation in female sperm storage organs

Sperm cells are exceptionally morphologically diverse across taxa. However, morphology can be quite uniform within species, particularly for species where females copulate with many males per reproductive bout. Strong sexual selection in these promiscuous species is widely hypothesized to reduce intraspecific sperm variation. Conversely, we hypothesize that intraspecific sperm size variation may be maintained by high among-female variation in the size of sperm storage organs, assuming that paternity success improves when sperm are compatible in size with the sperm storage organ. We use individual-based simulations and an analytical model to evaluate how selection on sperm size depends on promiscuity level and variation in sperm storage organ size (hereafter, female preference variation). Simulations of high promiscuity (10 mates per female) showed stabilizing selection on sperm when female preference variation was low, and disruptive selection when female preference variation was high, consistent with the analytical model results. With low promiscuity (2-3 mates per female), selection on sperm was stabilizing for all levels of female preference variation in the simulations, contrasting with the analytical model. Promiscuity level, or mate sampling, thus has a strong impact on the selection resulting from female preferences. Furthermore, when promiscuity is low, disruptive selection on male traits will occur under much more limited circumstances (i.e. only with higher among-female variation) than many previous models suggest. Variation in female sperm storage organs likely has strong implications for intraspecific sperm variation in highly promiscuous species, but likely does not explain differences in intraspecific sperm variation for less promiscuous taxa.

Effects of reliance on stored sperm on reproduction in the sailfin molly Poecilia latipinna

The impacts of relying on stored sperm were evaluated in the sailfin molly, Poecilia latipinna. Females reliant on stored sperm had fewer offspring compared to remated females, but offspring size and short-term growth rate did not differ. Thus, females may use stored sperm in cases such as previous mating with a preferred male, lack of access to mating opportunities during a reproductive cycle, or to maximize egg fertilization. Females do not compensate for producing fewer offspring however, by allocating more resources to offspring relative to their size or initial growth.

Octopaminergic/tyraminergic Tdc2 neurons regulate biased sperm usage in female Drosophila melanogaster

In polyandrous internally fertilizing species, a multiply-mated female can use stored sperm from different males in a biased manner to fertilize her eggs. The female's ability to assess sperm quality and compatibility is essential for her reproductive success, and represents an important aspect of postcopulatory sexual selection. In Drosophila melanogaster, previous studies demonstrated that the female nervous system plays an active role in influencing progeny paternity proportion, and suggested a role for octopaminergic/tyraminergic Tdc2 neurons in this process. Here, we report that inhibiting Tdc2 neuronal activity causes females to produce a higher-than-normal proportion of first-male progeny. This difference is not due to differences in sperm storage or release, but instead is attributable to the suppression of second-male sperm usage bias that normally occurs in control females. We further show that a subset of Tdc2 neurons innervating the female reproductive tract is largely responsible for the progeny proportion phenotype that is observed when Tdc2 neurons are inhibited globally. On the contrary, overactivation of Tdc2 neurons does not further affect sperm storage, release or progeny proportion. These results suggest that octopaminergic/tyraminergic signaling allows a multiply-mated female to bias sperm usage, and identify a new role for the female nervous system in postcopulatory sexual selection.

Transcriptome Analysis Reveals Key Gene Expression Changes in Blue Catfish Sperm in Response to Cryopreservation

The hybrids of female channel catfish (Ictalurus punctatus) and male blue catfish (I. furcatus) account for >50% of US catfish production due to superior growth, feed conversion, and disease resistance compared to both parental species. However, these hybrids can rarely be naturally spawned. Sperm collection is a lethal procedure, and sperm samples are now cryopreserved for fertilization needs. Previous studies showed that variation in sperm quality causes variable embryo hatch rates, which is the limiting factor in hybrid catfish breeding. Biomarkers as indicators for sperm quality and reproductive success are currently lacking. To address this, we investigated expression changes caused by cryopreservation using transcriptome profiles of fresh and cryopreserved sperm. Sperm quality measurements revealed that cryopreservation significantly increased oxidative stress levels and DNA fragmentation, and reduced sperm kinematic parameters. The present RNA-seq study identified 849 upregulated genes after cryopreservation, including members of all five complexes in the mitochondrial electron transport chain, suggesting a boost in oxidative phosphorylation activities, which often lead to excessive production of reactive oxygen species (ROS) associated with cell death. Interestingly, functional enrichment analyses revealed compensatory changes in gene expression after cryopreservation to offset detrimental effects of ultra-cold storage: MnSOD was induced to control ROS production; chaperones and ubiquitin ligases were upregulated to correct misfolded proteins or direct them to degradation; negative regulators of apoptosis, amide biosynthesis, and cilium-related functions were also enriched. Our study provides insight into underlying molecular mechanisms of sperm cryoinjury and lays a foundation to further explore molecular biomarkers on cryo-survival and gamete quality.

Octopaminergic/tyraminergic Tdc2 neurons regulate biased sperm usage in female Drosophila melanogaster

In polyandrous internally fertilizing species, a multiply-mated female can use stored sperm from different males in a biased manner to fertilize her eggs. The female's ability to assess sperm quality and compatibility is essential for her reproductive success, and represents an important aspect of postcopulatory sexual selection. In Drosophila melanogaster, previous studies demonstrated that the female nervous system plays an active role in influencing progeny paternity proportion, and suggested a role for octopaminergic/tyraminergic Tdc2 neurons in this process. Here, we report that inhibiting Tdc2 neuronal activity causes females to produce a higher-than-normal proportion of first-male progeny. This difference is not due to differences in sperm storage or release, but instead is attributable to the suppression of second-male sperm usage bias that normally occurs in control females. We further show that a subset of Tdc2 neurons innervating the female reproductive tract is largely responsible for the progeny proportion phenotype that is observed when Tdc2 neurons are inhibited globally. On the contrary, overactivation of Tdc2 neurons does not further affect sperm storage and release or progeny proportion. These results suggest that octopaminergic/tyraminergic signaling allows a multiply-mated female to bias sperm usage, and identify a new role for the female nervous system in postcopulatory sexual selection.

Record Longevity and Reproduction of an African Tick, Argas brumpti (Ixodida: Argasidae)

Argas brumpti Neumann is a large argasid (soft) tick that inhabits the drier areas of eastern and southern Africa. This species typically feeds on a wide variety of small to large mammals (including humans) and lizards, and resides in shallow caves, rocky areas, or dust-bath areas used by large mammals. Individuals of this species, collected as nymphs and adults from a semidesert area of Kenya and subsequently maintained under constant conditions in the laboratory, survived for 27 yr. Furthermore, after 8 yr of starvation and at least 4 yr after the last male died, at least one female laid eggs. The progeny developed into considerable numbers of both males and females, some of which are still living after 26 yr. The longevity of these ticks is apparently a record for any species of tick. The delay in reproduction likely represents long-term storage of viable sperm, also apparently a record for any species of tick.

A Taxonomic Survey of Female Oviducal Glands in Chondrichthyes: A Comparative Overview of Microanatomy in the Two Reproductive Modes

Oviducal glands (OGs) are distinct expanded regions of the anterior portion of the oviduct, commonly found in chondrichthyans, which play a key role in the production of the egg in-vestments and in the female sperm storage (FSS). The FSS phenomenon has implications for understanding the reproductive ecology and management of exploited populations, but little information is available on its taxonomic extent. For the first time, mature OGs from three lecithotrophic oviparous and four yolk-sac viviparous species, all considered at risk from the fishing impacts in the central western Mediterranean Sea, were examined using light microscopy. The OG microanatomy, whose morphology is generally conserved in all species, shows differences within the two reproductive modalities. Oviparous species show a more developed baffle zone in respect to viviparous ones because of the production of different egg envelopes produced. Among oviparous species, Raja polystigma and Chimaera monstrosa show presence of sperm, but not sperm storage as observed, instead, in Galeus melastomus and in all the viviparous sharks, which preserve sperm inside of specialized structures in the terminal zone.

Physiological factors influencing female fertility in birds

Fertility is fundamental to reproductive success, but not all copulation attempts result in a fertilized embryo. Fertilization failure is especially costly for females, but we still lack a clear understanding of the causes of variation in female fertility across taxa. Birds make a useful model system for fertility research, partly because their large eggs are easily studied outside of the female's body, but also because of the wealth of data available on the reproductive productivity of commercial birds. Here, we review the factors contributing to female infertility in birds, providing evidence that female fertility traits are understudied relative to male fertility traits, and that avian fertility research has been dominated by studies focused on Galliformes and captive (relative to wild) populations. We then discuss the key stages of the female reproductive cycle where fertility may be compromised, and make recommendations for future research. We particularly emphasize that studies must differentiate between infertility and embryo mortality as causes of hatching failure, and that non-breeding individuals should be monitored more routinely where possible. This review lays the groundwork for developing a clearer understanding of the causes of female infertility, with important consequences for multiple fields including reproductive science, conservation and commercial breeding.

Real-time PCR-based Y-specific sperm quantification assay in Queensland fruit fly: Insights to patterns of sperm storage

Studies of reproductive biology in insects often require quantification of sperm production, transfer or storage. Here, we develop a quantitative real-time PCR-based assay using a Y-specific marker for quantification of sperm from spermathecae of female Queensland fruit fly ('Q-fly'), overcoming constraints typical of traditional sperm quantification methods. The assay enables accurate and reliable quantification of as few as 50 sperms and provides a means to analyse large numbers of samples with flexible timing. The real-time PCR method enables revised understanding of how many sperms are stored by female Q-flies, the distribution of storage between the two spermathecae and the relationship between copula duration and sperm storage. Real-time PCR assays based on Y-specific markers provide an effective solution for sperm quantification in tephritid flies, as well as in other insects and potentially other animals with sperm storage organs.

Changes in Phenotypes and DNA Methylation of In Vitro Aging Sperm in Common Carp Cyprinus carpio

The purpose of the current study was to analyze phenotypic and functional characteristics of common carp (Cyprinus carpio) spermatozoa during in vitro aging and to investigate whether global DNA methylation is affected by sperm aging. Milt was collected from five individual males, stored in vitro on ice in a refrigerator for up to 96 h post stripping (HPS) and used to fertilize eggs with intervals of 1, 24 and 96 h. Computer-assisted sperm analysis and a S3e Cell Sorter was employed to determine the spermatozoa phenotypic characteristics (motility, velocity, concentration and viability). In addition, pH and osmolality of the seminal fluid and the capacity of the spermatozoa to fertilize, hatching rate and health of the resulting embryos were examined at different aging times. Whole-genome bisulfite sequencing was used to compare the global and gene-specific DNA methylation in fresh and aged spermatozoa. The results demonstrated that spermatozoa aging in common carp significantly affects their performance and thus the success of artificial fertilization. The methylation level at the cytosine-phosphate-guanine (CpG) sites increased significantly with 24 HPS spermatozoa compared to the fresh group at 1 HPS and then decreased significantly at 96 HPS. A more detailed investigation of gene specific differences in the DNA methylation was hindered by incomplete annotation of the C. carpio genome in the public databases.

Transcriptomic and metabolomic insights into the variety of sperm storage in oviduct of egg layers

In birds, the sperm storage tubules (SST) are dispersed in uterovaginal junction (UVJ) and highly correlated with differential capacity of sperm storage (SS) in and among species with unspecified mechanisms. Here, the SS duration of 252 egg layer breeders was evaluated in 5 rounds with 3 phenotypic traits to screen high- and low-SS individuals, respectively, followed with transcriptome of UVJ tissues and metabolome of serum (high-SS vs. low-SS) to decipher the candidate genes and biochemical markers correlated with differential SS capacity. Histological characterization suggested slightly higher density of SST in UVJ (high-SS vs. low-SS). Transcriptome analyses identified 596 differentially expressed genes (336 upregulated vs. 260 downregulated), which were mainly enriched in gene ontology terms of homeostasis, steroid and lipid metabolism and hormone activity, and 12 significant pathways (P < 0.05) represented by calcium, steroid, and lipid metabolism. Immunohistochemical staining of GNAQ, ST6GAL1, ADFP, and PCNA showed similar distribution in UVJ tissues between 2 groups. Several candidates (HSD11B2, DIO2, AQP3, GNAQ, NANS, ST6GAL1) combined with 4 (11β-prostaglandin F2α, prostaglandin B1, 7α-hydroxytestosterone, and N-acetylneuraminic acid) of 40 differential metabolites enriched in serum metabolome were considered as regulators and biomarkers of SS duration in egg layer breeders. The integrated transcriptome and metabolome analyses of chicken breeder hens will provide novel insights for exploration and improvement of differential SS capacity in birds.

Seasonal expression of cytoplasmic creatine kinase in the epididymal epithelium of Pelodiscus sinensis

During hibernation of Pelodiscus sinensis, sperm mature and are stored in the epididymis. We investigated seasonal changes in the morphology of epithelial cells of the epididymis of P. sinensis and changes in expression of cytoplasmic creatine kinase (CK). We found that the epididymal epithelium proliferates rapidly to form multiple layers from June to September, while the epididymal epithelial cells are arranged in a single layer from October to May. From the March before the mating period to the end of the mating period in September, a large amount of neutral glycoprotein is secreted in the epididymal epithelium and in the sperm aggregation area; after October, the glycoprotein in the epididymis decreases. At sperm maturation, cytoplasmic CK is expressed abundantly in the villous epithelium, which is formed by proliferation of epididymal epithelial cells. During hibernation and reproduction, the epididymal epithelium of P. sinensis exhibits different proliferation and secretion patterns as the animal adapts to two types of sperm storage. Cytoplasmic CK may participate in regulating the energy metabolism of the epididymal epithelium; it is an important enzyme for regulating sperm maturation.

Transcriptome analysis and identification of age-associated fertility decreased genes in hen uterovaginal junction

Avian sperm storage tubules (SSTs), which are located in the uterovaginal junction (UVJ) of the oviduct, are primary sperm storage sites after mating or artificial insemination. The mechanism underlying reduced sperm storage efficiency of SSTs which is highly correlated with decreased fertility rates in aged laying breeders remains largely unclear. Here, comparative transcriptomic analysis between the aged and young White Leghorn hens (120 vs. 30 wk) was applied to identify gene expression changes of UVJs containing SSTs. Bioinformatics analysis revealed 567 upregulated and 1998 downregulated differentially expressed genes. Gene ontology analysis was highly enriched in terms of immune system, cell adhesion, and cytoskeleton proteins. Kyoto Encyclopedia of Genes and Genomes analysis revealed 5 significant (P < 0.05) pathways including inositol phosphate and glycerophospholipid metabolism. β-Galactosidase staining of chicken UVJ sections suggested increased cell senescence via aging. Oil Red O staining and immunohistochemistry detection of ADFP both confirmed distribution of lipid droplets in SST cells with increased intensity in aged breeders. The lipid synthesis and metabolism-related genes represented by TFAP2 and PLD1 were differentially expressed in aged laying breeders. The upregulation of IL15 and downregulation of a large number of immune-related genes in aged breeders indicate altered immune homeostasis in UVJs and SSTs. The increased accumulation of lipids, and altered immunity homeostasis, combined with other factors (TJP1, MYL9, AFDN, and RPL13, etc.) are potentially dominant effectors to decrease the sperm storage efficiency and egg fertility in aged laying breeders.

Reproductive cycle and fecundity of the bonnethead Sphyrna tiburo L. from the northwest Atlantic Ocean

The present study examined temporal changes in plasma sex hormone concentrations and the morphology and histology of reproductive organs in mature northwest Atlantic (NWA) bonnetheads Sphyrna tiburo L. to characterize reproductive cycle, breeding periodicity and fertility in this still poorly studied population. Progressive increases in testis width, epididymis head width, plasma testosterone (T) concentrations, and occurrence of mature spermatozoa were observed in male S. tiburo from June to September, demonstrating that spermatogenesis occurs during the summer. Nonetheless, increases in maximum follicle diameter, oviducal gland width, plasma 17β-estradiol and T concentrations, and occurrence of vitellogenic follicles were not observed in mature females until between October and April, demonstrating non-synchronous patterns of gametogenesis in males and females. Fresh copulatory wounds were observed in females collected during late September along with histological evidence for sperm presence in the oviducal gland between September and April, confirming a 6- to 7 month period of female sperm storage. Ovulation occurred between mid-April and early May in concert with increases in female plasma progesterone concentrations. Gestation occurred during a 4.5- to 5 month period between May and early September, and 97% of mature females collected during this period were gravid, indicating a highly synchronized, annual reproductive periodicity. Brood size was significantly correlated with maternal size and ranged from 1 to 13 pups with a mean ± S.D. of 8.1 ± 2.2, which was significantly lower than reported in Gulf of Mexico (GOM) populations. The occurrence of non-fertile offspring was observed in 17% of broods with a range of 1-7 non-fertile eggs present in individual females. Thus, as previously reported in GOM S. tiburo, this unusual form of infertility also appears to be prevalent in the NWA population and requires further study. This study has demonstrated meaningful differences in reproductive biology of these populations, emphasizing the need for region-specific approaches for population management.

Sperm competition in squamate reptiles

Multiple paternity is ubiquitous within the polyphyletic group called 'reptiles', especially within the lizards and snakes. Therefore, the probability of sperm competition occurring, and being intense, is high. Squamates exhibit a diversity of tactics to ensure fertilization success in the face of sperm competition. The duration of female sperm storage, which can be many months and even years in some species, remains an enigma. Here, we emphasize some mechanisms that might affect patterns of paternity, the source and function of ejaculates and features of the female reproductive tract that may aid in long-term sperm storage. In doing so, we present a new analysis of the relationship between sperm size, the strength of sperm competition and the duration of female sperm storage. Lizards and snakes are a diverse group that has provided many excellent models for the study of an array of life-history strategies. However, when it comes to postcopulatory sexual selection, there is much left to discover. This article is part of the theme issue 'Fifty years of sperm competition'.

Functional morphology of the sperm-containing chambers of the sea slug Okenia polycerelloides in the context of sexual selection

Sea slugs are interesting models to study post-copulatory sexual selection in simultaneous hermaphrodites due to the enormous variation of their reproductive systems. However, the knowledge of the functional morphology of their reproductive system is limited to few species, and it is rarely discussed in the context of sexual selection theory. In this study, we investigated the functional morphology of the sperm-containing chambers (i.e., ampulla, seminal receptacle, and bursa copulatrix) of the reproductive system of Okenia polycerelloides (Ortea & Bouchet, 1983), based on light, confocal, and electron microscopy. Although the morphology of the ampulla is similar to other species, indicating that it is a site for autosperm storage, we found some sperm facing the ampullar epithelium, a feature commonly regarded as characteristic of the seminal receptacle of sea slugs. The seminal receptacle of O. polycerelloides showed secretory activity and contained sperm with distribution and orientation suggestive of stratification of allosperm from distinct mating events, a feature that would affect sperm competition. The bursa copulatrix had epithelial cells with secretory and absorptive characteristics, and contained degraded sperm and yolk granules within its lumen. Comparative analyses of the contents of each organ demonstrated that sperm digestion occurs in the bursa copulatrix and affects sperm heads first, changing their morphology from slender and curved to shorter and ellipsoid before complete lysis. Although digestion and absorption of surplus sperm are currently the main hypothesized functions for the bursa copulatrix, its role in cryptic female choice should not be ruled out. The close structural connection between the seminal receptacle and bursa copulatrix, as well as their muscular walls, would enable control over the fate of the sperm received in each mating event, that is, storage or digestion.

Reproduction in the pitviper Bothrops jararacussu: large females increase their reproductive output while small males increase their potential to mate

Reproductive traits vary widely within and among snake species, and are influenced by a range of factors. However, additional studies are needed on several species, especially on tropical snake faunas, to fully understand the patterns of reproductive variation in snakes. Here, we characterized the reproductive biology of B. jararacussu from southeastern and southern Brazil. We combined macroscopic and microscopic examinations of the reproductive system of museum specimens with observations of free-ranging snakes to characterize size at sexual maturity, sexual size dimorphism (SSD), reproductive output, and male and female reproductive cycles. We compared our data with published literature and discuss the factors that may play a role in shaping the reproductive patterns in the species and the genus. Bothrops jararacussu shares several characteristics with its congeners such as autumn mating season, obligatory sperm storage in the female reproductive tract, seasonal timing of parturition (summer-autumn), female-biased SSD, maturity at larger body sizes in females, and a positive relationship between body size and litter size. These characteristics seem phylogenetically conserved in Bothrops. On the other hand, B. jararacussu exhibits some unique characteristics such as a high degree of SSD (one of the highest values recorded in snakes), a large female body size, and a large litter and offspring size, which are among the largest recorded in the genus. Moreover, larger females reproduce more frequently than smaller conspecifics. These characteristics may be collectively interpreted as the result of a strong selection for increased fecundity. Other peculiarities of the species include an asynchrony between spermiogenesis (summer-autumn) and the peak of SSK hypertrophy (autumn to spring) and a prolonged production of SSK granules. Because SSK hypertrophy and mating are androgen-dependent in snakes, the prolonged SSK hypertrophy suggests that male B. jararacussu may prolong their potential to mate (compared with its congeners), which may increase their reproductive success. Our results and previous literature collectively suggest that, in Bothrops, the evolution of SSD is driven by fecundity selection, variation in reproductive output is influenced by variation in female body size, and the timing of spermiogenesis is influenced by other factors in addition to temperature. We also suggest that male Bothrops have undergone multiple evolutionary shifts in the timing of spermiogenesis.

Promiscous female Euxesta eluta derive nutrients for ovarian development by expelling and consuming ejaculates

Seminal gifts range from important material donations to items that provide little direct benefit to females. Promiscuous, female silk corn flies Euxesta eluta expel and consume male ejaculates immediately after mating. The evolution and function of this peculiar behavior are currently unknown. We performed a series of experiments aimed to: determine if females under different dietary regimes derive nutrients or water for survival and/or reproduction from ejaculate consumption, if males suffer a fitness cost from supplying females with ejaculates, and if females prefer to mate and/or are more likely to store sperm from well fed than nutritionally stressed presumably inferior males. Experiments revealed that protein deprived E. eluta females derive nutrients for ovarian development through consumption of ejaculates of protein fed males. No seminal products affecting survival appear to be transferred in the consumed ejaculate. However, ovarian development, in contrast to testes growth, occurs in detriment of longevity. Females preferred to mate with protein fed males, yet sperm retention in spermathecae was extremely rare after a single mating. This finding suggests that females could be exerting post copulatory control. A key question that remained to be addressed for the understanding of this puzzling and promiscuous mating system is what ecological factors or male traits drive females to retain sperm from one or several males in order to achieve and/or maximize fertilization potential.

Interaction of Epididymal Epithelia and their Secretions with Spermatozoa Supports Functional and Morphological Changes During Long-Term Storage in the Chinese Soft-Shelled Turtle (Pelodiscus sinensis)

Post-testicular maturation of spermatozoa is crucial for attaining the morphological and functional capabilities needed for successful fertilization. Epididymal epithelia offer a favorable environment for spermatozoa that are stored long term in the turtle epididymis; however, sperm-epithelial interactions during storage, which are enormously important for sperm functional and morphological maturation, are still largely unknown in turtles. The present study examined the epididymis during the sperm-storage period (November-April) in the Chinese soft-shelled turtle (Pelodiscus sinensis). Light and transmission electron microscopy were used to determine the cellular features of each epididymal segment (caput, corpus, and cauda) and their epithelial interactions with the spermatozoa. Spermatozoa were mainly located in the lumena of caput, corpus, and cauda epididymides. Numerous spermatozoa were bound to apical surfaces of the epithelia, and several were even embedded in the epithelial cytoplasm of the caput and corpus epididymides. No embedded spermatozoa were found in the cauda epididymis. In all epididymal segments, principal and clear cells showed the synthetic activity, evidenced by a well-developed endoplasmic reticulum network and high and low electron-dense secretory materials, respectively. Principal and clear cells in the caput and corpus segments showed embedded spermatozoa in electron-dense secretions and in the lipid droplets within the cytoplasm. No lysosomes were observed around the embedded spermatozoa. The lumena of the caput and corpus segments showed few apocrine and low electron density secretions. In the lumen of the cauda epididymidis, different secretions, such as holocrine with low and high electron density and their fragmentation, apocrine, and dictyosome, were found and are summarized. Altogether, sperm physical interactions with secretions either in the cytoplasm of epithelium or in the lumen may support the viability, morphological maintenance, and transfer of various proteins involved in long-term sperm storage in the turtle. This interaction could help us to understand the mechanisms of long-term sperm storage and provide more insights into the reproductive strategies of turtle sperm preservation.

Sequencing of the black rockfish chromosomal genome provides insight into sperm storage in the female ovary

Black rockfish (Sebastes schlegelii) is an economically important viviparous marine teleost in Japan, Korea, and China. It is characterized by internal fertilization, long-term sperm storage in the female ovary, and a high abortion rate. For better understanding the mechanism of fertilization and gestation, it is essential to establish a reference genome for viviparous teleosts. Herein, we used a combination of Pacific Biosciences sequel, Illumina sequencing platforms, 10× Genomics, and Hi-C technology to obtain a genome assembly size of 848.31 Mb comprising 24 chromosomes, and contig and scaffold N50 lengths of 2.96 and 35.63 Mb, respectively. We predicted 39.98% repetitive elements, and 26,979 protein-coding genes. S. schlegelii diverged from Gasterosteus aculeatus ∼32.1-56.8 million years ago. Furthermore, sperm remained viable within the ovary for up to 6 months. The glucose transporter SLC2 showed significantly positive genomic selection, and carbohydrate metabolism-related KEGG pathways were significantly up-regulated in ovaries after copulation. In vitro suppression of glycolysis with sodium iodoacetate reduced sperm longevity significantly. The results indicated the importance of carbohydrates in maintaining sperm survivability. Decoding the S. schlegelii genome not only provides new insights into sperm storage; additionally, it is highly valuable for marine researchers and reproduction biologists.

Structural variation in Drosophila melanogaster spermathecal ducts and its association with sperm competition dynamics

The ability of female insects to retain and use sperm for days, months, or even years after mating requires specialized storage organs in the reproductive tract. In most orders, these organs include a pair of sclerotized capsules known as spermathecae. Here, we report that some Drosophila melanogaster females exhibit previously uncharacterized structures within the distal portion of the muscular duct that links a spermatheca to the uterus. We find that these 'spermathecal duct presences' (SDPs) may form in either or both ducts and can extend from the duct into the sperm-storing capsule itself. We further find that the incidence of SDPs varies significantly between genotypes, but does not change significantly with the age or mating status of females, the latter indicating that SDPs are not composed of or stimulated by sperm or male seminal proteins. We show that SDPs affect neither the number of first male sperm held in a spermatheca nor the number of offspring produced after a single mating. However, we find evidence that SDPs are associated with a lack of second male sperm in the spermathecae after females remate. This raises the possibility that SDPs provide a mechanism for variation in sperm competition outcome among females.

Upregulation of CRISP-3 and kallikrein in stallion seminal plasma is associated with poor tolerance of cooled storage

For unknown reasons, stallion fertility and sperm longevity during cooled storage of semen vary markedly between individuals. Spermatozoa from individual stallions react differently to the presence, or the removal, of seminal plasma (SP). The aim was to evaluate differences in protein content in stallion seminal plasma with either a positive or a negative effect on sperm chromatin integrity during storage. Stallion semen samples from different ejaculate fractions were stored at 5°C for 24 hr. Sperm survival was assessed after storage using a sperm chromatin structure assay. Protein expression in SP with either positive or negative effects on sperm survival during storage was studied using two-dimensional differential gel electrophoresis and liquid chromatography-mass spectrometry. Lower sperm chromatin integrity was associated with upregulation of the proteins kallikrein, CRISP-3 and HSP-1, while higher chromatin integrity was associated with upregulation of TIMP-2. In the sperm-rich fractions, kallikrein and CRISP-3 differed significantly between SP samples with differing effects on sperm chromatin integrity. In the sperm-poor fractions, TIMP-2 and HSP-1 differed significantly between the two SP groups. Differences in the seminal plasma proteome are associated with sperm longevity during cooled storage.

Control of mating plug expelling and sperm storage in Drosophila: A gynandromorph- and mutation-based dissection

INTRODUCTION

In this study, we analyzed gynandromorphs with female terminalia, to dissect mating-related female behaviors in Drosophila.

MATERIALS AND METHODS

We used gynandromorphs, experimentally modified wild-type (Oregon-R) females, and mutant females that lacked different components of the female reproductive apparatus.

RESULTS

Many of the gynandromorphs mated but did not expel the mating plug (MP). Some of these - with thousands of sperm in the uterus - failed to take up sperm into the storage organs. There were gynandromorphs that stored plenty of sperm but failed to release them to fertilize eggs. Expelling the MP, sperm uptake into the storage organs, and the release of stored sperm along egg production are separate steps occurring during Drosophila female fertility. Cuticle landmarks of the gynandromorphs revealed that while the nerve foci that control MP expelling and also those that control sperm uptake reside in the abdominal, the sperm release foci derive from the thoracic region of the blastoderm.

DISCUSSION AND CONCLUSION

The gynandromorph study is confirmed by analyses of (a) mutations that cause female sterility: Fs(3)Avar (preventing egg deposition), Tm2^gs (removing germline cells), and iab-4^DB (eliminating gonad formation) and (b) by experimentally manipulated wild-type females: decapitated or cut through ventral nerve cord.

Impact of immune activation on stored sperm viability in ant queens

Ant queens mate on a single occasion early in life and store millions of sperm cells in their spermatheca. By carefully using stored sperm to fertilize eggs, they can produce large colonies of thousands of individuals. Queens can live for decades and their lifetime reproductive success is dependent on their ability to keep stored sperm alive. Maintaining high sperm viability requires metabolic energy which could trade-off with other costly processes such as immunity. We tested the impact of immune activation on the survival of stored sperm by prompting Lasius niger ant queens to mount a melanization response and subsequently measuring sperm viability in their spermatheca. Since queens face different challenges that influence energy allocation depending on the life stage of their colony, we measured sperm viability after immune activation in both newly mated queens (incipient) and in queens 1 year after mating (established). We found that immune activation reduced sperm viability in established queens but not in incipient queens, showing that the cost of immunity on sperm preservation depends on the life stage. Unexpectedly, established queens had significantly higher sperm viability in their spermatheca compared to incipient queens suggesting that ant queens are able to remove dead sperm from their spermatheca.

Spermathecal Filling in Aedes aegypti and Aedes albopictus: Effects of Female and Male Body Sizes and Species

The mosquitoes Aedes aegypti (L.) (Diptera: Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae) are ecologically similar species that have evolved independently in their native ranges, Ae. aegypti in Africa and Ae. albopictus in Asia. Where their invasive ranges overlap, interspecific mating is facilitated by both species swarming to mate around bloodmeal hosts during daylight. Here, we test hypotheses to account for variation in spermathecal filling in females of Ae. aegypti and Ae. albopictus, particularly, the effect of mosquito size on the number of spermathecae containing sperm after intraspecific and interspecifc matings of these two species. Results show that significantly more spermathecae contained sperm in large than in small Ae. albopictus females, but there was no effect of Ae. aegypti female body size on the average number of spermathecae filled. Among inseminated females, there was no effect of male size or cross-type on number of spermathecae with sperm. Differences in the effect of female size on the number of spermathecae that store sperm in Ae. aegypti and Ae. albopictus imply differences in the mating biology of these two species.

Last male sperm precedence is modulated by female remating rate in Drosophila melanogaster

Following multiple matings, sperm from different males compete for fertilization within the female reproductive tract. In many species, this competition results in an unequal sharing of paternity that favors the most recent mate, termed last male sperm precedence (LMSP). Much of our understanding of LMSP comes from studies in Drosophila melanogaster that focus on twice‐mated females with standardized latencies between successive matings. Despite accumulating evidence indicating that females often mate with more than two males and exhibit variation in the latency between matings, the consequences of mating rate on LMSP are poorly understood. Here, we developed a paradigm utilizing D. melanogaster in which females remated at various time intervals with either two or three transgenic males that produce fluorescent sperm (green, red, or blue). This genetic manipulation enables paternity assessment of offspring and male‐specific sperm fate examination in female reproductive tracts. We found that remating latency had no relationship with LMSP in females that mated with two males. However, LMSP was significantly reduced in thrice‐mated females with short remating intervals; coinciding with reduced last‐male sperm storage. Thus, female remating rate influences the relative share of paternity, the overall clutch paternity diversity, and ultimately the acquisition of indirect genetic benefits to potentially maximize female reproductive success.

Evidence for sperm storage in common smoothhound shark Mustelus mustelus and paternity assessment in a single litter from South Africa

The present histological study of adult female common smoothhound shark Mustelus mustelus demonstrates that the species can store sperm in their oviducal glands. In addition, single paternity of a litter of 22 pups is reported, contributing to further knowledge regarding the genetic and behavioural mating strategy of M. mustelus.

Caffeine strongly improves motility parameters of turkey spermatozoa with no effect on cell viability

The purpose of this study was to evaluate the impact of caffeine on turkey spermatozoa during in vitro incubation. Experimental samples were prepared by diluting the raw semen with nine different concentrations of caffeine - from 0.078125 mg/mL to 10 mg/mL. The individual motility parameters were evaluated by the Computer Assisted Semen Analyser (CASA) system, and the viability of spermatozoa was evaluated using eosin-nigrosin staining. Selected parameters were recorded at six time periods: 0, 1, 2, 3, 4 and 5 h at 5 °C and 41 °C. A significantly higher motility and progressive motility of spermatozoa (P < 0.01 and P < 0.001, respectively) was detected in the samples containing caffeine ranging from 0.15625 to 7.5 mg/mL as compared to the control sample at 5 °C. At an incubation temperature of 41 °C the positive effect of caffeine on motility parameters was observed only at the beginning of incubation (at times 0 and 1). The tested caffeine concentrations showed no significant effect on the viability of turkey spermatozoa at any time period of incubation. A higher percentage of dead spermatozoa was observed for incubation at 41 °C (from 5.96% to 11.1%) in comparison to 5 °C (from 1.62% to 5.79%). The results suggest that caffeine can be used as a suitable component of turkey semen extenders and has the potential to improve fertility.

Severe Fertility Effects of sheepish Sperm Caused by Failure To Enter Female Sperm Storage Organs in Drosophila melanogaster

In Drosophila, mature sperm are transferred from males to females during copulation, stored in the sperm storage organs of females, and then utilized for fertilization. Here, we report a gene named sheepish (shps) of Drosophila melanogaster that is essential for sperm storage in females. shps mutant males, although producing morphologically normal and motile sperm that are effectively transferred to females, produce very few offspring. Direct counts of sperm indicated that the primary defect was correlated to failure of shps sperm to migrate into the female sperm storage organs. Increased sperm motion parameters were seen in the control after transfer to females, whereas sperm from shps males have characteristics of the motion parameters different from the control. The few sperm that occasionally entered the female sperm storage organs showed no obvious defects in fertilization and early embryo development. The female postmating responses after copulation with shps males appeared normal, at least with respect to conformational changes of uterus, mating plug formation, and female remating rates. The shps gene encodes a protein with homology to amine oxidases, including as observed in mammals, with a transmembrane region at the C-terminal end. The shps mutation was characterized by a nonsense replacement in the third exon of CG13611, and shps was rescued by transformants of the wild-type copy of CG13611 Thus, shps may define a new class of gene responsible for sperm storage.

Sperm storage influences the potential for spontaneous acrosome reaction of the sperm in the newt Cynops pyrrhogaster

Sperm storage is supposed to influence sperm quality, although the details remain unclear. In the present study, we found that sperm stored in a sperm storage site, the vas deferens of Cynops pyrrhogaster, spontaneously undergo acrosome reaction following incubation in Steinberg's salt solution (ST). Percentages of acrosome-reacted sperm increased time-dependently to about 60% in 24 hr. The concentration of cyclic adenosine monophosphate (cAMP) was elevated after incubating sperm in ST, while dibutylyl cAMP induced an acrosome reaction. Chelating of extracellular Ca²⁺ suppressed the dibutylyl cAMP-induced acrosome reaction as well as spontaneous acrosome reaction in ST. These results suggest that cAMP elevation driven by Ca²⁺ influx can be a cue for spontaneous acrosome reaction. Relatively low Ca²⁺ concentration and pH in the vas deferens were sufficient to suppress spontaneous acrosome reaction within 1 hr. In addition, the cysteine rich secretory protein 2 gene was expressed in the vas deferens, indicating that it may be involved in the continuous suppression of spontaneous acrosome reaction. Sperm that underwent spontaneous acrosome reaction in ST was significantly increased when stored in the vas deferens for longer periods, or by males experiencing temperatures in excess of 12°C during hibernation conditions. Percentages of the spontaneously acrosome-reacted sperm were found to differ among males even though they were of identical genetic background. Taken together, C. pyrrhogaster sperm possess the potential for spontaneous acrosome reaction that does not become obvious in the vas deferens, unless promoted in correlation with sperm storage.

Investigation of in vitro measurable sperm attributes and their influence on electroejaculated bull semen with a fixed-time artificial insemination protocol in Australian Bos indicus cattle

Increasing use of fixed-time artificial insemination (FTAI) in beef cattle production has presented an opportunity for the use of fresh or chilled semen as an alternative to standard cryopreserved semen. The objective of this study was to examine in vitro sperm function and pregnancy rate of electroejaculated semen, chilled and stored for 48 hr, compared to conventionally cryopreserved semen with an optimized FTAI protocol in Brahman cattle. Semen from three Brahman bulls was collected, and aliquots were extended in either chilled (at 5°C) or frozen (LN₂ ) in a Tris-egg yolk extender base with 2.4% or 7.0% glycerol, respectively. Semen samples were assessed 48 hr after collection or post-thaw and warming, for sperm motility, in vitro sperm function and fertilizing ability, and used in a FTAI programme. The overall pregnancy rates was significantly different (p < .01) after FTAI with frozen (n = 173; 53.2%) and chilled semen (n = 174; 31.6%). In contrast, the in vitro sperm assessment showed that the chilled semen had significantly faster motility (p < .05), a higher proportion of progressively motile spermatozoa (p < .05), with significantly higher proportions of acrosome intact, viable spermatozoa (p < .01). This study showed that reasonable pregnancy rates in Brahman cattle can be achieved using FTAI with chilled semen collected using electroejaculation and stored for up to 48 hr. However, improvements in semen extenders are required in consideration of semen collection method to improve the longevity of sperm fertilizing ability to significantly increase FTAI output using chilled storage of bull semen.

Isolating Spermathecae and Determining Mating Status of Drosophila suzukii: A Protocol for Tissue Dissection and Its Applications

The spotted wing drosophila, Drosophila suzukii (Diptera: Drosophilidae), is an emerging invasive pest, which attacks a wide variety of fruits and berries. Although previous studies have focused on different aspects of D. suzukii reproductive biology, there are no protocols available for determining the mating status of D. suzukii females and drosophilids in general. In this study, a step-by-step protocol for tissue dissection, isolating spermathecae, and determining the mating status of females was developed specifically for D. suzukii. This protocol is an effective and relatively quick method for determining female mating status. It has important applications from exploring reproductive output of D. suzukii females to understanding the biology of D. suzukii winter morph, which presumably plays the main role in the overwintering of this invasive species. We demonstrated applicability of this protocol for both field collected flies and flies reared in the lab, including fly specimens stored on a long-term basis.

Don't pull the plug! the Drosophila mating plug preserves fertility

Mating plugs are hardened structures--typically a coagulation of seminal fluid components--that are transferred to, or formed within, the female reproductive tract of numerous animal species (both mammals and insects). Analysis of the role(s) of the mating plug in reproduction has been conducted in a wide array of diverse species. These structures have been proposed to have a multitude of functions, which include altering female re-mating rate, acting as a barrier to re-mating and being required for sperm storage or sperm movement to occur in mated females. A recent analysis of the Drosophila melanogaster mating plug has shown that proper formation of the structure is required for optimal fertility in flies: the Drosophila mating plug is required to retain the ejaculate within the female reproductive tract once mating has terminated. Here, we discuss the possible implications of the Drosophila mating plug in the fertility of this species in light of these new results.

Sperm use economy of honeybee (Apis mellifera) queens

The queens of eusocial ants, bees, and wasps only mate during a very brief period early in life to acquire and store a lifetime supply of sperm. As sperm cannot be replenished, queens have to be highly economic when using stored sperm to fertilize eggs, especially in species with large and long‐lived colonies. However, queen fertility has not been studied in detail, so that we have little understanding of how economic sperm use is in different species, and whether queens are able to influence their sperm use. This is surprising given that sperm use is a key factor of eusocial life, as it determines the fecundity and longevity of queens and therefore colony fitness. We quantified the number of sperm that honeybee (Apis mellifera) queens use to fertilize eggs. We examined sperm use in naturally mated queens of different ages and in queens artificially inseminated with different volumes of semen. We found that queens are remarkably efficient and only use a median of 2 sperm per egg fertilization, with decreasing sperm use in older queens. The number of sperm in storage was always a significant predictor for the number of sperm used per fertilization, indicating that queens use a constant ratio of spermathecal fluid relative to total spermathecal volume of 2.364 × 10⁻⁶ to fertilize eggs. This allowed us to calculate a lifetime fecundity for honeybee queens of around 1,500,000 fertilized eggs. Our data provide the first empirical evidence that honeybee queens do not manipulate sperm use, and fertilization failures in worker‐destined eggs are therefore honest signals that workers can use to time queen replacement, which is crucial for colony performance and fitness.

Winter is coming: hibernation reverses the outcome of sperm competition in a fly

Sperm commonly compete within females to fertilize ova, but research has focused on short‐term sperm storage: sperm that are maintained in a female for only a few days or weeks before use. In nature, females of many species store sperm for months or years, often during periods of environmental stress, such as cold winters. Here we examine the outcome of sperm competition in the fruit fly Drosophila pseudoobscura, simulating the conditions in which females survive winter. We mated females to two males and then stored the female for up to 120 days at 4°C. We found that the outcome of sperm competition was consistent when sperm from two males was stored for 0, 1 or 30 days, with the last male to mate fathering most of the offspring. However, when females were stored in the cold for 120 days, the last male to mate fathered less than 5% of the offspring. Moreover, when sperm were stored long term the first male fathered almost all offspring even when he carried a meiotic driving sex chromosome that drastically reduces sperm competitive success under short‐term storage conditions. This suggests that long‐term sperm storage can radically alter the outcome of sperm competition.

Expression of TLR2/4 in the sperm-storing oviduct of the Chinese soft-shelled turtle Pelodiscus sinensis during hibernation season

The initiation of innate immunology system could play an important role in the aspect of protection for sperms long‐term storage when the sperms got into oviduct of turtles and come into contact with epithelium. The exploration of TLR2/4 distribution and expression in oviduct during hibernation could help make the storage mechanism understandable. The objective of this study was to examine the gene and protein expression profiles in Chinese soft‐shelled turtle during hibernation from November to April in the next year. The protein distribution of TLR2/4 was investigated in the magnum, isthmus, uterus, and vagina of the turtle oviduct using immunohistochemistry, and the gene expression of TLR2/4 was analyzed using quantitative real‐time PCR (qRT‐PCR). The results showed positive TLR2 protein expression primarily in the epithelium of the oviduct. TLR4 immunoreactivity was widely observed in almost every part of the oviduct, particularly in the epithelium and secretory gland membrane. Analysis of protein, mRNA expression revealed the decreased expression of TLR2/4 in the magnum compared with the isthmus, uterus, and vagina during hibernation. The protein and mRNA expression of TLR2 in the magnum, isthmus, uterus, and vagina was decreased in April compared with that in November. TLR4 protein and mRNA expression in the magnum, isthmus, uterus and vagina was decreased in November compared with that in April. These results indicated that TLR2/4 expression might protect the sperm from microbial infections. In contrast to the function of TLR2, which protects sperm during the early stages of hibernation, TLR4 might play a role in later stages of storage. The present study is the first to report the functions of TLR2/4 in reptiles.

Sperm storage and spermatozoa interaction with epithelial cells in oviduct of Chinese soft-shelled turtle, Pelodiscus sinensis

Spermatozoa are known to be stored within the female genital tract after mating in various species to optimize timing of reproductive events such as copulation, fertilization, and ovulation. The mechanism supporting long-term sperm storage is still unclear in turtles. The aim of this study was to investigate the interaction between the spermatozoa and oviduct in Chinese soft-shelled turtle by light and electron microscopy to reveal the potential cytological mechanism of long-term sperm storage. Spermatozoa were stored in isthmus, uterine, and vagina of the oviduct throughout the year, indicating long-term sperm storage in vivo. Sperm heads were always embedded among the cilia and even intercalated into the apical hollowness of the ciliated cells in the oviduct mucosal epithelium. The stored spermatozoa could also gather in the gland conduit. There was no lysosome distribution around the hollowness of the ciliated cell, suggesting that the ciliated cells of the oviduct can support the spermatozoa instead of phagocytosing them in the oviduct. Immune cells were sparse in the epithelium and lamina propria of oviduct, although few were found inside the blood vessel of mucosa, which may be an indication of immune tolerance during sperm storage in the oviduct of the soft-shelled turtle. These characteristics developed in the turtle benefited spermatozoa survival for a long time as extraneous cells in the oviduct of this species. These findings would help to improve the understanding of reproductive regularity and develop strategies of species conservation in the turtle. The Chinese soft-shelled turtle may be a potential model for uncovering the mechanism behind the sperm storage phenomenon.

Seasonal effects on egg production and level of paternity in a natural population of a simultaneous hermaphrodite snail

In a seasonal environment, the suitable time window for females to reproduce is restricted by both environmental conditions and the availability of males. In simultaneous hermaphrodites, which are female and male at the same time, selection on a trait that is solely beneficial for one sexual function cannot occur independently. Therefore, it is assumed that the optimal time window for reproduction is a compromise between the two sexual functions in simultaneous hermaphrodites, mediated by environmental conditions. We examined seasonal patterns of reproduction and the resulting paternity in a natural population of the simultaneously hermaphroditic land snail Arianta arbustorum. Adult and premature individuals (snails in a short protandric phase) were collected on four occasions over the entire active season. The snails were allowed to deposit eggs after which we assessed the level of paternity in their hatched offspring. Individuals mated throughout the reproductive season, whereas egg production - the major task of the female function - was restricted to the first half of the season. Snails collected in autumn were allowed to hibernate under laboratory conditions. As a result, we found that premature individuals began to mate late in the reproductive season, but did not start to produce eggs before emerging from hibernation. Our results demonstrate a temporal shift of reproductive activities; the egg production and oviposition occur mainly in the first half of the season, while sperm production and mating occur over the entire season. In subadult and adult snails, sperm obtained from several partners in the second part of the reproductive season are stored during hibernation for the fertilization of eggs in the successive years. These results extend our understanding of the influence of both natural and sexual selection on reproductive strategies in hermaphrodites.

Retention of Ejaculate by Drosophila melanogaster Females Requires the Male-Derived Mating Plug Protein PEBme

Within the mated reproductive tracts of females of many taxa, seminal fluid proteins (SFPs) coagulate into a structure known as the mating plug (MP). MPs have diverse roles, including preventing female remating, altering female receptivity postmating, and being necessary for mated females to successfully store sperm. The Drosophila melanogaster MP, which is maintained in the mated female for several hours postmating, is comprised of a posterior MP (PMP) that forms quickly after mating begins and an anterior MP (AMP) that forms later. The PMP is composed of seminal proteins from the ejaculatory bulb (EB) of the male reproductive tract. To examine the role of the PMP protein PEBme in D. melanogaster reproduction, we identified an EB GAL4 driver and used it to target PEBme for RNA interference (RNAi) knockdown. PEBme knockdown in males compromised PMP coagulation in their mates and resulted in a significant reduction in female fertility, adversely affecting postmating uterine conformation, sperm storage, mating refractoriness, egg laying, and progeny generation. These defects resulted from the inability of females to retain the ejaculate in their reproductive tracts after mating. The uncoagulated MP impaired uncoupling by the knockdown male, and when he ultimately uncoupled, the ejaculate was often pulled out of the female. Thus, PEBme and MP coagulation are required for optimal fertility in D. melanogaster. Given the importance of the PMP for fertility, we identified additional MP proteins by mass spectrometry and found fertility functions for two of them. Our results highlight the importance of the MP and the proteins that comprise it in reproduction and suggest that in Drosophila the PMP is required to retain the ejaculate within the female reproductive tract, ensuring the storage of sperm by mated females.

Sperm storage: distinguishing selective processes and evaluating criteria

Sperm storage, the extended maintenance of viable sperm, probably occurs in most internally fertilizing animals. Because it temporally separates mating from conception, sperm storage can be adaptive in ecologically diverse habitats and affect life histories, mating systems, cryptic female choice, sperm competition, and sexual conflict. Sperm storage can result from different selective forces acting on females and/or males, sometimes resulting in coevolution. The various criteria often used to determine the presence of sperm storage in any given taxon can result from the action of any one or all of these selective forces. Here we discuss the criteria used to study sperm storage and how we can use these to better understand the evolution of diversity in sperm-storage adaptations.

Beneficial effects of relaxin on motility characteristics of stored boar spermatozoa

BACKGROUND

Relaxin is detected in seminal plasma of many species and its association with sperm motility may be beneficial in some aspects of assisted reproduction. Here, we immunolocalized relaxin receptors and investigated the effects of exogenous relaxin on motility characteristics, viability, and cAMP content of boar spermatozoa after storage.

METHODS

Commercial doses of boar semen were obtained on the collection day (Day 0) and kept in shipping containers at room temperature for up to 4 days (Day 4). On Day 0, spermatozoa were fixed for immunofluorescence detection of relaxin receptors RXFP1 and RXFP2 (Experiment 1). Semen aliquots were taken from the same dose at Day 0, Day 1, and Day 2 (Experiment 2a), and Day 2 and Day 4 (Experiment 2b) for analyses. Alive spermatozoa were purified and incubated (1 h-37°C) with 0, 50, or 100 ng relaxin/ml (Experiment 2a) and 0, 100, or 500 ng relaxin/ml (Experiment 2b). Afterward, aliquots of each treatment group were subjected to motility (Experiments 2), viability (Experiment 3) analyses, and cAMP quantification (Experiment 4). Data (3-4 independent replicates) were statistically analyzed (ANOVA followed by pairwise comparisons) and p values less or equal to 0.05 was set for significant difference.

RESULTS

Both RXFP1 and RXFP2 receptors were immunolocalized on the entire spermatozoon. Relaxin concentration of 100 ng/ml significantly improved the proportions of motile, progressive, and rapid spermatozoa up to Day 2. Only 500 ng relaxin/ml provided beneficial effects on Day 4. The viability of spermatozoa was not affected by relaxin (100 ng/ml) during storage, but the extent of mitochondria membrane damages was significantly decreased. Furthermore, relaxin did not affect the cAMP contents of spermatozoa during storage, in our conditions.

CONCLUSIONS

Relaxin could be a valuable motility booster of stored- or aged-spermatozoa for assisted reproduction techniques. However, the related-intracellular signaling cascades of relaxin in boar spermatozoa remain undetermined.

Fluorescent sperm in a transparent worm: validation of a GFP marker to study sexual selection

BACKGROUND

Sexual selection has initially been thought to occur exclusively at the precopulatory stage in terms of contests among males and female mate choice, but research over the last four decades revealed that it often continues after copulation through sperm competition and cryptic female choice. However, studying these postcopulatory processes remains challenging because they occur internally and therefore are often difficult to observe. In the transparent free-living flatworm Macrostomum lignano, a recently established transgenic line that expresses green fluorescent protein (GFP) in all cell types, including sperm, offers a unique opportunity to non-invasively visualise and quantify the sperm of a GFP-expressing donor inside the reproductive tract of wild-type recipients in vivo. We here test several aspects of the reproductive performance of the transgenic individuals and the accuracy of the techniques involved in assessing the GFP-expressing worms and their sperm. We then show the usefulness of these methods in a study on sperm displacement.

RESULTS

GFP-expressing worms do not differ from wild-type worms in terms of morphology, mating rate and reproductive success. In addition, we show that the GFP signal is reliably and unequivocally expressed by all GFP-expressing individuals observed under epifluorescence illumination. However, the intensity of the GFP signal emitted by sperm of GFP expressing donors can vary (which we show to be at least in part due to sperm ageing) and the GFP marker is inherited according to Mendel's laws in most, but not all, of the individuals. Nevertheless, we argue these two issues can be addressed with an appropriate experimental design. Finally, we demonstrate the value of the GFP-techniques by comparing the number of GFP-expressing sperm in a wild-type recipient before and after mating with a competing sperm donor, providing clear experimental evidence for sperm displacement in M. lignano. This result suggests that sperm donors can displace previously stored sperm and replace it with their own.

CONCLUSION

The availability of the GFP-techniques in a transparent organism provide unique opportunities to visualise and quantify internal processes in the female reproductive tract after mating, which opens new avenues in the study of sexual selection.

Repeated visitations of spermatophores and polyandry in females of eriophyoid mites

Eriophyoid females store sperm either asymmetrically in one spermatheca, or symmetrically in both spermathecae. Previous studies have suggested that species in which females store sperm asymmetrically pick up sperm from only one spermatophore, while those with symmetrical sperm storage pick up sperm from two or more spermatophores during their lifetime. The aim of this study was to examine spermatophore visitation behaviour and symmetry of sperm storage in Aculops allotrichus from the black locust tree and Cecidophyopsis hendersoni from the yucca. This would indicate monandry or polyandry in these species. In both eriophyoids, the spermatophore visitation consisted of three phases: mounting, lying on the spermatophore and dismounting. Aculops allotrichus stored sperm asymmetrically. However, nearly one-third of the observed females visited two spermatophores, rather than only one in their lives. When A. allotrichus females visited two spermatophores they spent a similar amount of time at the first and at the second visitation. Also, the times of visitation of the first of the two spermatophores and the single spermatophore in a female lifetime did not differ significantly. This would suggest that apart from monandry, double insemination also occurs in this species. By contrast, C. hendersoni females were polyandrous. They stored sperm symmetrically and visited several spermatophores, on average 1.54 (max 6) per day, and up to 33 spermatophores in their lives. The benefits of repeated spermatophore visitation and the possible mechanisms of sperm storage in both species are discussed.

The reproductive system of Osedax (Annelida, Siboglinidae): ovary structure, sperm ultrastructure, and fertilization mode

Osedax is a genus of siboglinid annelids in which the females live on dead vertebrate bones on the seafloor. These females have a posterior end that lies within the bone and contains the ovarian tissue, as well as the "roots" involved with bone degradation and nutrition. The males are microscopic and live as "harems" in the lumen of the gelatinous tube that surrounds the female trunk, well away from the ovary. Females are known to spawn fertilized primary oocytes, suggesting internal fertilization. However, little is known about sperm transfer, sperm storage, or the location of fertilization, and the morphology of the female reproductive system has not been described and compared with the reproductive systems of other siboglinids. A 3D-reconstruction of the ovisac of Osedax showed ovarian tissue with multiple lobes and mature oocytes stored in a "uterus" before being released through the single oviduct. The oviduct emerges as a gonopore on the trunk and travels along the trunk to finally open to the seawater as a thin cylindrical tube among the crown of palps. Light and transmission electron microscopy of mature Osedax sperm revealed elongate heads consisting of a nucleus with helical grooves occupied by mitochondria. In contrast to other Siboglinidae, Osedax sperm are not packaged into spermatophores or spermatozeugmata, and Osedax females lack a discrete region for sperm storage. Transmission electron microscopy and fluorescence microscopy allowed detection of sperm associated with ovarian tissue of the female ovisac of four different Osedax species. This provides the first evidence for the site of internal fertilization in Osedax. A heart body was found in the circulatory system, as seen in other siboglinids and some other annelids. The possible presence of nephridia in the anterior ovisac region was also documented. These morphological features provide new insights for comparing the regionalization of Osedax females in relation to other siboglinids.

Rapid diversification of sperm precedence traits and processes among three sibling Drosophila species

Postcopulatory sexual selection is credited with driving rapid evolutionary diversification of reproductive traits and the formation of reproductive isolating barriers between species. This judgment, however, has largely been inferred rather than demonstrated due to general lack of knowledge about processes and traits underlying variation in competitive fertilization success. Here, we resolved processes determining sperm fate in twice-mated females, using transgenic Drosophila simulans and Drosophila mauritiana populations with fluorescently labeled sperm heads. Comparisons among these two species and Drosophila melanogaster revealed a shared motif in the mechanisms of sperm precedence, with postcopulatory sexual selection potentially occurring during any of the three discrete stages: (1) insemination; (2) sperm storage; and (3) sperm use for fertilization, and involving four distinct phenomena: (1) sperm transfer; (2) sperm displacement; (3) sperm ejection; and (4) sperm selection for fertilizations. Yet, underlying the qualitative similarities were significant quantitative differences in nearly every relevant character and process. We evaluate these species differences in light of concurrent investigations of within-population variation in competitive fertilization success and postmating/prezygotic reproductive isolation in hybrid matings between species to forge an understanding of the relationship between microevolutionary processes and macroevolutionary patterns as pertains to postcopulatory sexual selection in this group.