The reproductive cycle of the male sleep snake Sibynomorphus mikanii (Schlegel, 1837) from southeastern brazil

This study describes the male reproductive cycle of Sibynomorphus mikanii from southeastern Brazil considering macroscopic and microscopic variables. Spermatogenesis occurs during spring–summer (September–December) and spermiogenesis or maturation occurs in summer (December–February). The length and width of the kidney, the tubular diameter, and the epithelium height of the sexual segment of the kidney (SSK) are larger in summer–autumn (December–May). Histochemical reaction of the SSK [periodic acid‐Schiff (PAS) and bromophenol blue (BB)] shows stronger results during summer–autumn, indicating an increase in the secretory activity of the granules. Testicular regression is observed in autumn and early winter (March–June) when a peak in the width of the ductus deferens occurs. The distal ductus deferens as well as the ampulla ductus deferentis exhibit secretory activities with positive reaction for PAS and BB. These results suggest that this secretion may nourish the spermatozoa while they are being stored in the ductus deferens. The increase in the Leydig cell nuclear diameter in association with SSK hypertrophy and the presence of sperm in the female indicate that the mating season occurs in autumn when testes begin to decrease their activity. The peak activity of Leydig cells and SSK exhibits an associated pattern with the mating season. However, spermatogenesis is dissociated of the copulation characterizing a complex reproductive cycle. At the individual level, S. mikanii males present a continuous cyclical reproductive pattern in the testes and kidneys (SSK), whereas at the populational level the reproductive pattern may be classified as seasonal semisynchronous. © J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

Renal sexual segment of the ground skink, Scincella laterale (Reptilia, Squamata, Scincidae)

Mature squamates possess hypertrophied regions of the distal urinary ducts, the renal sexual segment (RSS). The RSS is believed to provide seminal fluid that mixes with sperm and is released into the female cloaca during coitus. This study is the first to describe ultrastructure of the RSS in a lizard collected throughout the active season. The species examined, Scincella laterale, represents the largest family (Scincidae: 1,200 species) of lizards. Although sperm are present in the posterior ductus deferens of male S. laterale throughout the year, an annual spermatogenic cycle occurs that results in spermiation in spring, coinciding with maximum development of the RSS. Female S. laterale may possess stored sperm in vaginal crypts from March-May and large oviductal eggs April-June. Thus, the correlation between mating and RSS activity observed in other squamates is also found in S. laterale. Cytologically, the active RSS consists of columnar cells with numerous apical, electron-dense secretory vacuoles which are released by an apocrine process. The granules stain positively for proteins with bromphenol blue and react with PAS for neutral carbohydrates. After the mating season the RSS undergoes recrudescence and the electron-dense granules are replaced by a mucoid secretion that characterizes more proximal portions of the nephric tubules throughout the year. Little variation in ultrastructure of the RSS occurs between S. laterale and Cnemidophorus lemniscatus (Teiidae), the only other lizard in which seasonal variation of the RSS has been studied using similar methods. Females exhibit differentiation similar to that of males in the distal urinary tubules, but to a lesser degree. This is only the second such report for female squamates, and the differentiation of the region in females is proposed to result from adrenal androgens.     

Evolutionary reduction in testes size and competitive fertilization success in response to the experimental removal of sexual selection in dung beetles

Sexual selection is thought to favor the evolution of secondary sexual traits in males that contribute to mating success. In species where females mate with more than one male, sexual selection also continues after copulation in the form of sperm competition and cryptic female choice. Theory suggests that sperm competition should favor traits such as testes size and sperm production that increase a male's competitive fertilization success. Studies of experimental evolution offer a powerful approach for assessing evolutionary responses to variation in sexual selection pressures. Here we removed sexual selection by enforcing monogamy on replicate lines of a naturally polygamous horned beetle, Onthophagus taurus, and monitoring male investment in their testes for 21 generations. Testes size decreased in monogamous lines relative to lines in which sexual selection was allowed to continue. Differences in testes size were dependent on selection history and not breeding regime. Males from polygamous lines also had a competitive fertilization advantage when in sperm competition with males from monogamous lines. Females from polygamous lines produced sons in better condition, and those from monogamous lines increased their sons condition by mating polygamously. Rather than being costly for females, multiple mating appears to provide females with direct and/or indirect benefits. Neither body size nor horn size diverged between our monogamous and polygamous lines. Our data show that sperm competition does drive the evolution of testes size in onthophagine beetles, and provide general support for sperm competition theory.     

Population density mediates the interaction between pre‐ and postmating sexual selection

When females mate with more than one male, sexual selection acts both before and after mating. The interaction between pre‐ and postmating episodes of selection is expected to be context dependent, but few studies have investigated how total sexual selection changes under different ecological conditions. We examined how population density mediates the interaction between pre‐ and postmating sexual selection by establishing replicate populations of the horned dung beetle Onthophagus taurus at low, medium, and high densities, and then using microsatellite‐based parentage analyses to measure male fitness. We found that mating success and fertilization success were positively correlated at all three densities, but the strength of the correlation decreased with increasing density. We also found a shift from negative to positive linear selection on testes mass as density increased, and opposing selection on weapons and testes at high densities. These patterns suggest that the importance of postmating processes increases with increasing population density, which reduces the selective advantage of weapons for premating contest competition, and increases the selective advantage of large ejaculates for postmating sperm competition. We expect that density‐dependent selection on testes mass has contributed to the phenotypic variation observed between natural populations of O. taurus that differ in density.     

Reproductive biology of the male little mastiff bat, Mormopterus planiceps (Chiroptera:Molossidae), in southeast Australia

The anatomy, biology, and chronology of reproduction in the male of the long penile form of Mormopterus planiceps was studied in southeast South Australia and Victoria. In the morphology of its primary and accessory reproductive organs, M. planiceps was generally reminiscent of other Molossidae; however, in the specialized (sebaceous) nature of the Cowper's gland ducts, in the presence of para-anal glands, and in the unusual, horizontally bifid glans penis and the greatly elongated os penis, it was distinct from other Molossidae studied to date. Young of the year were not reproductively active. Adults displayed a single annual spermatogenic cycle that commenced in spring (September/October) and culminated in spermiogenesis in autumn (February-May), during which period plasma levels of testosterone overtook androstenedione. Thereafter, spermatogenesis appeared to cease (though scattered sperm were seen in the seminiferous tubules until August), but abundant epididymal sperm reserves persisted until September/(October). The accessory glands were hypertrophied during this period, becoming involuted by October. Although the numbers of animals available for study were small, these observations, together with the appearance of spermatozoa in the ductus deferens in August/September suggested that mating could occur during the interval from autumn to spring. Late winter/spring insemination is normal for molossids from temperate environments. However, protracted spermatogenesis commencing in spring that is not accompanied by the availability of spermatozoa until autumn, and a subsequent apparent extension of fertility (epididymal sperm storage, accessory gland hypertrophy) beyond the testicular gametogenic phase, are aspects of the male reproductive cycle in M. planiceps that have not heretofore been described in another molossid bat.     

Prolonged epididymal sperm storage, and the temporal dissociation of testicular and accessory gland activity in the common sheath-tail bat, Taphozous georgianus, of tropical Australia

Peak spermatogenic activity of the common sheath-tail bat occurs in autumn, declines over winter and ceases in spring. Accessory glands enlarge in spring when mating occurs, but are regressed at other times of the year. Spermatozoa are stored in the cauda epididymidis throughout the year, and their numbers increase progressively from early summer to late autumn. Sperm storage permits asynchrony of male and female cycles and allows each to be optimally timed in relation to environmental conditions. The temporal separation of primary and secondary sexual functions in the male enables the insemination of females close to ovulation and is a consequence of the burden of sperm storage being placed upon the male.     

Basic properties and annual changes of follicle-stimulating hormone receptors in the testis of horseshoe bats, Rhinolophus ferrumequinum

The unique reproductive patterns, delayed fertilization in females, and asynchrony between spermatogenesis and mating behavior in males are well documented in bats living in temperate latitudes. The present study was undertaken to examine follicle-stimulating hormone (FSH) receptors in the testis of bats, Rhinolophus ferrumequinum, during the annual reproductive cycle. Male bats were captured at natural roosting sites and testicular preparations were subjected to a radioligand binding assay for FSH receptors. The weight of paired testes increased considerably in the spermatogenic period and decreased from the mating to hibernation periods. Meiotic division in the testis was observed in the spermatogenic period but not the mating period. Serum testosterone concentrations increased in the spermatogenic period and rapidly decreased in the mating period. The binding of FSH was specific for mammalian FSHs and detected primarily in the testis. Scatchard plot analyses of the binding of FSH to bat testicular preparations showed straight lines, suggesting the presence of a single class of binding sites. The affinities (equilibrium association constant) of FSH receptors were consistent throughout the annual reproductive cycle. The specific binding per unit weight of testis and total binding in the paired testes were highest in the mating period and in the spermatogenic period, respectively, among reproductive periods. The accumulation of cyclic adenosine 3', 5'-monophosphate to FSH stimulation was higher in the spermatogenic period than in the hibernation period. These findings suggest that testicular function of bats is associated with seasonal changes in the number of binding sites, while the number per target cell and the activation of adenylate cyclase led by FSH-receptor complex considerably decreases in the hibernation period.     

Copulation, the dynamics of sperm transfer and female refractoriness in the leafhopper Balclutha incisa (Hemiptera: Cicadellidae: Deltocephalinae)

Abstract.  Mature sperm of the leafhopper Balclutha incisa (Matsumara) (Cicadellidae: Auchenorrhyncha: Hemiptera) are stored as a series of sperm bundles within seminal vesicles prior to ejaculation. During transfer, sperm are pumped from the vesicles into the ejaculatory duct to the complex aedeagus. Sperm transfer is marked by a c . 30-fold expansion of the spermatheca to accommodate both sperm and seminal fluid. Sperm number increases exponentially with male age, reaching a maximum of 700 000 after 14 days, while the number of sperm available on days 2–5 is between 70 000 and 100 000. During mating, maximum sperm transfer occurs after 7 min and mating is complete after about 10 min. Ejaculate size, defined by both sperm and associated accessory gland fluid, is influenced by male mating status and the interval since the previous mating. There is a positive correlation between duration of copulation and both ejaculate and the time to subsequent mating. Sperm are more likely to be retained in the testes during mating by males of 2–5 days post-emergence than older males. The number of sperm received by the female can be manipulated experimentally by mating males once (medium ejaculate) or twice (small ejaculate) immediately after their first mating. Females that receive small ejaculates from sperm-depleted males have a far shorter refractory period than females receiving medium to large ejaculates. Both ejaculate size and the time after males have mated influence the female post-mating refractory period as measured by the female's responsiveness to male sexual signalling.     

Reproduction of the canyon bat, Pipistrellus hesperus, in southwestern United States.

The reproductive biology of the bat Pipistrellus hesperus was investigated histologically using animals obtained from nature at monthly intervals throughout the year. The female shows proestrous morphological changes in late summer and autumn, which continue until early spring. Insemination is probably effected several times during proestrous, since both sexes are intermittently active throughout this period (August--April). Permanent arousal from torpor and return to normal metabolism in the spring results in ovulation. Both ovaries are functional and both uterine horns may be utilized. P. hesperus is monestrous; two young per bat is usual. The male spermatogenic cycle is initiated in late June and the first sperm are available for ejaculation in September. Some sperm remain in the seminiferous tubules until early March. The epididymides also serve in sperm storage with the caput emptied by late February and the cauda in April. Leydig cells are largely nonsecretory from March through July, a few are secretory in August and most are secretory in September and October. Active cells gradually decline in number until few are secretory in late March. Accessory sex glands are functionally cyclic: they are small from April through August, hypertrophy in September, and gradually involute to the resting stage through March, to achieve total involution in April. The penis, similar in structure to that of other vespertilionids, is thought specialized to insure effective insemination.     

Seasonal Ultrastructural Changes of Leydig Cells in Lacerta muralis

We have studied the ultrastructure of the testis and interstitial tissue of lizard Lacerta muralis sacrificed in spring, summer and autumn, with special emphasis on the morphological changes of Leydig cells. From the autumn to the end of spring, Leydig cells showed a large smooth endoplasmic reticulum and mitochondria with tubular cristae. These features correlate with the synthesis and secretion of androgens. At the end of spring and after mating, the amount of smooth endoplasmic reticulum decreased and the mitochondria showed laminar cristae. Both features are typical of a latent period, during which time secretion of androgens remains inactive until the end of summer. The possible role of other cell organelles, such as Golgi complex and lysosome-like electron dense bodies, during both secreting and resting periods, is also discussed. Finally, we consider the relationship between seasons, secretory activity of Leydig cells and the spermatogenic cycle.     

Not just a chastity belt: the functional significance of mating plugs in garter snakes,revisited

During the spring emergence of red‐sided garter snakes (Thamnophis sirtalis parietalis) in Manitoba, Canada, the operational sex ratio is strongly skewed towards males, who scramble to locate and court newly emerged females. A high frequency of multiple paternity litters suggests that the females are promiscuous; the gelatinous copulatory plugs (CPs) deposited by males may confer fitness benefits via passive mate guarding. Because precopulatory female choice is limited in large mating aggregations, sexual conflict may place a premium on preventing females from ejecting male sperm. In snakes, sperm are produced in the testes and delivered through the ductus deferens, and the CP is thought to be produced by the renal sexual segment and conveyed through the ureter. We manipulated the delivery of the two fluids separately by surgically ligating the ducts. Ureter‐ligated males did not produce a CP, causing their sperm to leak out of the female's cloaca immediately after copulation. Contrary to previous suggestions, histology revealed sperm distributed throughout the CP. Thus, the CP may function as a spermatophore: the protein matrix contains the sperm, which are liberated gradually as the plug dissolves. The likelihood of a male depositing a CP fell significantly after his second mating, perhaps limiting his reproductive success. These results challenge the hypothesis that passive mate guarding is the primary function of the CP in T. sirtalis parietalis. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 893–907.     

Early gonadal development and primary males in the protogynous epinepheline, Cephalopholis boenak

Early gonadal development of the protogynous epinepheline, Cephalopholis boenak, was examined histologically in 289 specimens with standard length (L_S) of 42–130 mm, collected from May 2000 to April 2002 in Hong Kong waters, to determine male developmental pathways and establish its sexual pattern. All juvenile gonads developed an ovarian lumen with primary‐growth stage oocytes and scattered spermatogenic tissue prior to sexual differentiation and first sexual maturation. From this bisexual phase containing both female and male tissues, some gonads differentiated as ovaries with further oocyte growth to cortical‐alveolus and vitellogenic stages, the rest differentiated as testes with the proliferation of spermatogenic tissue and the formation of a sperm sinus. All testes retained the lumen and primary‐growth stage oocytes, and sperm sinuses ran within the gonad wall. Unlike most protogynous species, among functional males it was impossible to distinguish those resulting from juveniles through sexual differentiation (i.e. primary male) from those resulting from functional females through sex change (i.e. secondary male) based solely on testicular morphology. A proportion‐spermatogenic‐tissue index (I_ST) was, therefore, developed and determined to be a reliable quantitative indicator for distinguishing differentiating, primary males before a sperm sinus was evident, from differentiating females during sexual differentiation. Since sexually transitional specimens with the concominant appearance of degenerating vitellogenic, or later, stage oocytes and spermatogenic tissue in the gonads were previously noted from Hong Kong, diandric, protogynous hermaphroditism is confirmed in C. boenak. For species, such as this and other epinephelines, in which all males have the same testicular morphology, a complete analysis of a wide range of body sizes from juveniles to adults is necessary for understanding male developmental pathways, and determining sexual pattern.     

Slow increase of Sertoli cell efficiency and daily sperm production causes delayed establishment of full sexual maturity in the rodent Chinchilla lanigera

Puberty in the male Andean rodent Chinchilla lanigera occurred approximately 3 mo after birth, whereas full sexual maturity was established much later. The objective of the present study was to investigate testis function in postpubertal chinchillas, with an emphasis on the estimation of seminiferous epithelium cycle length (n=6) and Sertoli cell (SC) and spermatogenic efficiencies (n=26). Samples of testes were collected between May and November. Each spermatogenic cycle lasted 10.2d and the total duration of spermatogenesis was approximately 46 d. The SC efficiency (spermatids/SC) and the daily sperm production per testis gram increased markedly (P<0.05) from 5 to 17-22 mo of age, whereas the conversion rates of type A1 spermatogonia to preleptone and the number of spermatids per pachytene remained stable (P>0.05) from 5 to 30 mo. Therefore, efficiency of the spermatogenic process increased equally during all phases of spermatogenesis. In conclusion, based on the gradual and striking postpubertal increases for SC and sperm production, we inferred that more undifferentiated spermatogonia and/or spermatogonial stem cells were produced and therefore, that the chinchilla might represent a good experimental model to investigate regulation of this crucial aspect of spermatogenesis.     

Competitive PCR reveals the complexity of postcopulatory sexual selection in Teleogryllus commodus

The outcome of mate choice depends on complex interactions between males and females both before and after copulation. Although the competition between males for access to mates and premating choice by females are relatively well understood, the nature of interactions between cryptic female choice and male sperm competition within the female reproductive tract is less clear. Understanding the complexity of postcopulatory sexual selection requires an understanding of how anatomy, physiology and behaviour mediate sperm transfer and storage within multiply mated females. Here we use a newly developed molecular technique to directly quantify mixed sperm stores in multiple mating females of the black field cricket, Teleogryllus commodus. In this species, female postcopulatory choice is easily observed and manipulated as females delay the removal of the spermatophore in favour of preferred males. Using twice‐mated females, we find that the proportion of sperm in the spermatheca attributed to the second male to mate with a female (S₂) increases linearly with the time of spermatophore attachment. Moreover, we show that the insemination success of a male increases with its attractiveness and decreases with the size of the female. The effect of male attractiveness in this context suggests a previously unknown episode of mate choice in this species that reinforces the sexual selection imposed by premating choice and conflicts with the outcome of postmating male harassment. Our results provide some of the clearest evidence yet for how sperm transfer and displacement in multiply mated females can lead directly to cryptic female choice, and that three distinct periods of sexual selection operate in black field crickets.     

Population density and structure drive differential investment in pre‐ and postmating sexual traits in frogs

Sexual selection theory predicts a trade‐off between premating (ornaments and armaments) and postmating (testes and ejaculates) sexual traits, assuming that growing and maintaining these traits is costly and that total reproductive investments are limited. The number of males in competition, the reproductive gains from investing in premating sexual traits, and the level of sperm competition are all predicted to influence how males allocate their finite resources to these traits. Yet, empirical examination of these predictions is currently scarce. Here, we studied relative expenditure on pre‐ and postmating sexual traits among frog species varying in their population density, operational sex ratio, and the number of competing males for each clutch of eggs. We found that the intensifying struggle to monopolize fertilizations as more and more males clasp the same female to fertilize her eggs shifts male reproductive investment toward sperm production and away from male weaponry. This shift, which is mediated by population density and the associated level of male–male competition, likely also explains the trade‐off between pre‐ and postmating sexual traits in our much broader sample of anuran species. Our results highlight the power of such a multilevel approach in resolving the evolution of traits and allocation trade‐offs.     

Cyclic changes in the pituitary gland in correlation with the testicular cycle in a hill-stream teleost, Schizothorax richardsonii (Gray and Hard).

In Schizothorax richardsonii, the pituitary gland has been studied in correlation with the phases of the testicular cycle. The cyanophils of the proximal pars distalis show hypertrophy, hyperplasia, granulation, degranulation and vacuolisation in concurrence with the spermatogenic cycle. Secretory activity of the cyanophils controls the maturation of testes, which indicates that these cyanophils are gonadotrops. The formation of sperm mother cells, however, does not appear to depend on the secretory activity of the pituitary. During spawning and regression phases, the azocarminophilous granules in the cytoplasm of the cyanophils show quantitative variation. The migratory chromophil cells show numerical variation, suggesting their involvement in the reproductive cycle. Neurosecretory material also appears to play some part in reproduction.     

On the cost of searching for a mate in female pied flycatchers Ficedula hypoleuca

Female pied flycatchers, Ficedula hypoleuca, were trapped in one area and released in another a few kilometres away, where the positions of all available nest sites and males were known beforehand. Many of the females moved only a short distance before mating, settling after about 2 (0–6) days in early spring and about 1 day later on. The length of the premating period was negatively correlated with female body weight and prevailing air temperature, indicating that the females were subject to an energy constraint when searching. The premating period was longer for females that settled with an alreadymated male than for those mating with an unmated male. The significance of the results is discussed in relation to the evolution of avian mating systems, and of male behaviour and plumage colour. Competition for a mate, rather than for food, may explain the spacing of males (territoriality).     

Male coloration signals direct benefits in the European bitterling (Rhodeus amarus)

Female mating preferences are frequently associated with exaggerated male sexual traits. In the European bitterling, Rhodeus amarus, a fish with a resource-based mating system, male coloration is not associated with indirect genetic benefits of female mate choice, and does not reliably signal spawning site quality. We tested a link between the extent of male carotenoid-based coloration and testis size and number of spermatozoa stripped from the testes. Male body size predicted spermatozoa number, but less reliably than the extent of male coloration. Male color was a highly significant predictor of spermatozoa number, with approximately 26 % of variance in the number of spermatozoa stripped from males predicted from male color after controlling for male body size. Body size, but not coloration, predicted teste size. Female bitterling often risk sperm limitation, especially during pair spawnings, and male nuptial coloration may be under direct selection through female mate choice as a signal of male fertilization efficiency.     

Annual changes in testicular development and occurrence of parasperm in the male reproductive organs of fourspine sculpin, Cottus kazika

Annual changes in testicular development and occurrence of parasperm were investigated using 2-year-old male fourspine sculpins Cottus kazika, based on the histological observation of testes. The male reproductive organ of fourspine sculpins comprised a pair of testes and a sperm duct that functioned as a sperm-storage organ. Male maturity was divided into the following periods: spermatogonial proliferation period (September), early spermatogenic period (October), mid-spermatogenic period (November), late spermatogenic period (December and January), functional maturation period (February and March), and recovery period (April to August). Spermatogenesis rapidly progressed from October to January and continued until the functional maturation period. Parasperm formation, which is known in some cottidae species, was observed in fourspine sculpins. Testicular regression of cultured fourspine sculpins progressed slowly during the recovery period when residual parasperm and empty spaces occupied the testis. The parasperm were immotile and oval and slightly concave on one side; additionally, they stained strongly with hematoxylin and PAS. Seminal lobules of the testis were filled with parasperm during the spawning period; in contrast, the sperm duct was filled with eusperm. These findings were observed in both cultured and wild fish. In this study, the functions of parasperm with regard to reproduction in fourspine sculpins are discussed.     

渔游蛇雄性生殖周期及其肾性节的生殖生理学研究:Ⅱ.肾性节对精子的体外效应及生化分析

通过精子体外短期孵育表明：渔游蛇（Ｎａｔｒｉｘ ｐｉｓｃａｔｏｒ）肾性节具有营养精子的功能。聚丙烯酰 胺凝胶制备性电泳分离得到了肾性节特异性蛋白Ａ、Ｂ、Ｃ三因子。其中Ａ因子能显著提高精子在 体外的存活率，由Ａ１Ａ２两个亚基构成，分子量分别为６００００和３２０００。而Ｂ、Ｃ因子对精子存活 率无明显的影响。