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.     

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.     

Effect of mating on sperm distribution in the reproductive tract of the male rat

Extragonadal sperm reserves in male rats were measured in different regions of the genital tract before and subsequent to normal ejaculation. In sexually rested rats, the sperm count (million spermatozoa for the paired organs) in different regions was: distal vas, 18; proximal vas, 9.8; cauda epididymidis, 229; caput + corpus epididymidis, 154. Following mating, the sperm count was reduced in the proximal and distal vas deferens and in the cauda epididymidis. The reproductive tract of mated females was found to contain 29% (no copulatory plug) or 59% (with copulatory plug) of the estimated mean ejaculate, which was estimated from the difference between the sperm counts in the sexually rested rat and following ejaculation. It is concluded that in the rat the immediate source of spermatozoa for ejaculation is the cauda epididymidis, with a smaller contribution arising from the vas deferens.     

Reproductive biology of Philodryas patagoniensis (Snakes: Dipsadidae) in south Brazil: male reproductive cycle

The male reproductive cycle of Philodryas patagoniensis in south Brazil was described through morpho‐anatomical and histological analysis of individuals deposited in zoological collections. Spermatogenesis occurred during late autumn–winter (June–September) and spermiogenesis occurred in spring–summer (October–March). The volume of the testes was smaller (quiescent) in winter, while the tubular diameter and the epithelial height of the seminiferous tubule were larger in summer (January–March). The ductus deferens presented spermatozoa all over the year and had no seasonal variation in diameter. The length of the kidney was larger in winter–spring (July–December), although the tubular diameter and epithelium height of the sexual segment of the kidney (SSK) were larger only in winter (July–September). Total testicular regression was observed in late autumn (May), simultaneously with the peak in SSK. Therefore, at the individual level, males exhibit a discontinuous cyclical reproduction. Considering the population level, the reproductive cycle is seasonal semisynchronous, with most of the individuals showing a reproductive peak in spring–summer (October–March). Here, we present evidence to support the importance of the microscopic approach to reproductive cycle studies. Finally, we discuss the intrinsic and extrinsic factors influencing P. patagoniensis reproductive patterns.     

The prediapause copulation and its significance in the butterflyEurema hecabe

In the pierid butterflyEurema hecabe, which shows seasonal polymorphism (summer and autumn morphs) and overwinters at adult stage, whether or not the prediapause copulation may be of usual occurrence and reproductively functional was examined. From the counts of the spermatophores carried by the females, it is clear that the prediapause copulation characteristically occurs in reproductively inactive females of the autumn corph. From behavioral observations in the field, mating partners of those females are mostly males of the summer morph rather than from the autumn morph. In autumn, males of the summer morph remained abundant and searched for females on the larval food plants. Furthermore, they mated frequently with autumn morph females. Autumn morph males seemed to be sexually less active or inactive before hibernation. Microscopic examinations of the spermathecae were made in mated autumn-morph females collected before and after hibernation. The results indicate that sperm is passed by the males at autumnal copulation. The sperm may be stored in the female reproductive tract and utilized for fertilization in spring. This supposition is strongly supported by field data; that is, once-mated autumn-morph females laid fertilized eggs in spring. Finally, physiological basis of the prediapause copulation, its adaptive signficance and the behavioral advantage inE. hecabe are discussed from the viewpoint of seasonal adaptation.     

Spermatogenesis, changes in reproductive structures, and time constraint associated with insemination in Podisus nigrispinus

Males of the predatory stinkbug, Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae), accomplish long and multiple matings. We hypothesize that this behavior is due to time requirement for spermatozoa production and their transference to the females. Thus, this work investigated the effect of mating status of males and mating duration on spermatozoa transference to the females and the location of spermatozoa in the male reproductive tract during mating. On females, morphological alterations on female spermatheca and associated structures during a mating were investigated. Analyses of male reproductive tract showed presence of spermatozoa in the lumen of vas deferens was independent of mating status (ca. virgin, 0, 12 and 24 h after having a full mating), indicating continuous spermatogenesis which is supported by the absence of a seminal vesicle for spermatozoa storage. Female spermatheca had no changes associated with the duration of mating. However, females exhibited spermathecal elastic duct swelling by 30 min of mating duration. The success of males in filling the female spermatheca with spermatozoa depends on duration of mating. Thus, the results indicate that multiple mating is a requirement for reproductive success in the species by transference of spermatozoa and accessory substances stored in the female spermathecal duct. Likewise, the long mating is a male requirement to transfer materials in appropriate amount to the female but it is not dependent on spermatozoa alone.     

Reproductive biology of Philodryas patagoniensis (Snakes: Dipsadidae) in south Brazil: Female reproductive cycle

In this study, we describe the female reproductive cycle of Philodryas patagoniensis in south Brazil, which was described through morpho‐anatomical and histological analyses. The peak of secondary vitellogenesis occurred during winter–spring (July–December), ovulation in spring (October–December), mating and fertilization in spring–summer (October–February), oviposition in spring–autumn (October–May) and births from late spring to autumn (December–July). The diameter of vitellogenic follicles/eggs was larger in winter–spring than in other seasons. The diameter of the shell glands was also larger in winter–spring. In spite of the clear reproductive peak, gonads only showed reduced activity in the autumn. Therefore, at the individual level, females have a discontinuous cyclical reproduction; in the populational level, the reproductive cycle is seasonal semisynchronous. We support the hypothesis that P. patagoniensis have the ability to produce multiple clutches with long‐term stored sperm. Sexual dimorphism in body size was evident, and females are significantly larger and heavier than males. Larger females were able to produce follicles and eggs in larger amount and size. The maternal body size was positively related to the reproductive effort and fecundity. To conclude, we deliberated about the proximal and distal causes that influence the reproductive traits and patterns of P. patagoniensis.     

Male reproductive system of the arrow crab Stenorhynchus seticornis (Inachoididae)

Our aim was to describe the reproductive system of males and the formation of sperm packages in the seminal receptacle (SR) of recently mated females of the arrow crab Stenorhynchus seticornis. The male reproductive system was analyzed, and was described using light microscopy and histological and histochemical methods. The first pair of gonopods was described by means of scanning electron microscopy. Additionally, the dehiscence of spermatophores was tested using samples obtained from the vas deferens of males and from the seminal receptacle of recently mated females. Testes were tubular type, and each vas deferens consisted of three regions: the anterior vas deferens (AVD), including a proximal portion that was filled with free spermatozoa and a distal portion contained developing spermatophores; the median vas deferens (MVD) that contained completely formed spermatophores; and the posterior vas deferens (PVD), which contained only granular secretions. The accessory gland, which was filled with secretions, was located in the transition region between the MVD and the PVD. The spermatophores from the MVD were of different sizes, and none of them showed dehiscence in seawater, whereas those spermatophores in contact with the seminal receptacle were immediately broken. The ultrastructure of the gonopods revealed the presence of denticles at the distal portion, which contribute to the mechanical rupture of the spermatophore wall during the transfer of sperm. The contents of the PVD and accessory gland of males are transferred together with the spermatophores, and are responsible for the secretions observed among the sperm packets in the SR of the female. We suggest that these secretions formed the layers found in the SR of recently mated females, and may play a role in sperm competition in arrow crabs.     

Morphological changes in eupyrene and apyrene spermatozoa in the reproductive tract of the male butterfly Atrophaneura alcinous Klug

Summary

Eupyrene and apyrene spermatozoa are contained in separate cysts in the testis of the butterfly Atrophaneura alcinous. Spermatozoa of both types from various parts of the male reproductive tract were examined with particular reference to their morphological characteristics. All spermatozoa collected from the vas deferens and the vesicula seminalis were found to be immotile under a dissecting microscope. No spermatozoa of either type were recognized in any part of the ejaculatory duct. Within the testis, eupyrene spermatozoa are present in bundles and each spermatozoon has a slender nucleus with an acrosome and a long flagellum containing mitochondrial derivatives. Two kinds of appendages, lacinate and reticular, are present on the surface of the sperm membrane. They are replaced with an extracellular sheath during passage through the vas deferens. In contrast, apyrene spermatozoa have neither nucleus nor acrosome, whereas a cup-shaped structure was found at the sperm tip instead of the acrosome. Unlike eupyrene spermatozoa, they are surrounded by a concentric sheath outside the sperm membrane in the vas deferens. Individual apyrene spermatozoa and coiled bundles of eupyrene spermatozoa were both found to accumulate in the vesicula seminalis before mating. These morphological changes during passage through the male reproductive tract suggests the occurrence of a kind of maturation and capacitation process reminiscent of mammalian spermatozoa.     

Seasonal changes in semen quality and freezability in the Warmblood stallion

The objective of this study was to investigate seasonal changes in stallion semen quality and to determine the best time for semen cryopreservation. Experiments were performed using 10 Warmblood stallions from the National Stud Farm in Avenches (Switzerland). Ejaculates were collected and frozen every other week during 1 year from January to December 1999. Volume, concentration, and motility, and the number of morphologically normal sperm and sperm with major defects (abnormal heads, acrosome defects, nuclear vacuoles, proximal droplets, abnormal midpieces) were evaluated. For all frozen-thawed semen samples motility as well as viability (SYBR-14/PI) was tested, and the hypoosmotic swelling test (HOS) was performed. To analyze seasonal differences 4 periods of 3 months each were defined: autumn (September, October, November), winter (December, January, February), spring (March, April, May) and summer (June, July, August). During the 1 year experiment all semen quality parameters showed a clear seasonal pattern. The volume, total sperm count and motility in fresh semen were significantly higher (P<0.05) in summer than in winter, while sperm concentration was significantly lower in summer compared to the other seasons. Regarding morphology, normal sperm was significantly lower (P<0.05) in summer than at any other time of the year and higher values (P<0.05) were found for major defects in summer than in spring and autumn. In frozen-thawed semen motility was significantly (P<0.05) improved in autumn when compared to spring and summer. Viability was lowest in summer and differed significantly (P<0.05) from other seasons. The HOS test revealed significantly more (P<0.05) membrane damaged spermatozoa in winter than in spring, summer and autumn. Our results demonstrate that in our climatic conditions clear seasonal differences occur in semen quality of fresh and frozen-thawed semen and that cryopreservation of stallion semen should preferably be performed in autumn.     

Effects of larval exposure to sublethal concentrations of the ecdysteroid agonists RH-5849 and tebufenozide (RH-5992) on male reproductive physiology in Spodoptera litura

Sublethal concentrations of the bisacylhydrazine moulting hormone agonists, RH-5849, and tebufenozide (RH-5992) were fed to sixth (final) instar larvae of Spodoptera litura. Both RH-5849 and tebufenozide adversely affected the mating success of S. litura when the surviving treated males were crossed with normal females. The ecdysone agonists decreased the longevity of treated males and of untreated females when crossed with treated males. The number of eggs laid by untreated females mated to treated males was decreased, and the fertility (percentage of hatching success) of the resulting eggs was reduced. These effects on male reproductive success were at least in part explained by a reduction in the number of sperm transferred during mating. The adverse effects of tebufenozide on male reproductive function were qualitatively the same as those of RH-5849, but tebufenozide was active at lower concentrations. To understand the reason for these adverse effects on male reproduction, we investigated the effects of the insecticides on male reproductive physiology. Male reproductive tract development and testicular volume of resulting adult moths were adversely affected by sublethal larval exposure to the ecdysone agonists. Dose-dependent reductions occurred in the production of eupyrene and apyrene spermatozoa in the adult testes, and in the number of spermatozoa released from the testes into the male reproductive tract. The descent into the male tract of both eupyrene and apyrene sperm was found to start at the normal stage of development in both normal and treated insects, but the daily rhythm of sperm descent was subsequently disturbed in the insecticide-treated moths. This affected the numbers of sperm in the upper vas deferens (UVD), seminal vesicle (SV), and duplex (duplex). Injections of RH-5849 given to pharate adult or newly emerged adult S. litura also caused drastic reduction in the number of sperm in the upper regions of the male tract, when measured 24 h after injection. The possible importance of pest population reduction through the sublethal anti-reproductive effects of insecticides is discussed.     

Male Alpine Chamois Occupy Territories at Hotspots Before the Mating Season

Ungulate mating systems vary broadly both between and within species. Studies on mating systems in different habitats can provide clues to the ecological factors determining this diversity. Despite its abundance in the European Alps and its importance as a game species, surprisingly little is known about the mating system of Alpine chamois Rupicapra rupicapra rupicapra. We tested the hypothesis that adult males first defend mating territories in late spring, when females segregate from males and well before the Nov. rut. In the Gran Paradiso National Park (north‐western Italian Alps), adult males shared a winter range but occupied individual ranges in summer and early autumn. Males were more aggressive to each other in the summer than in the spring. A strong site fidelity from one year to the next was found for the summer and early autumn months. Those males that occupied the same territories both in the summer and during the rut (Nov.) appeared to be at hotspots, attractive to females during the rut because of reduced snow cover. Other males appeared to cluster around these hotspots during the rut. Territories that were first occupied during the summer were visited by more females than those that were not established until the rut began. Our results suggest that the mating system of this population of Alpine chamois consists of the early occupation of clustered mating territories. The early establishment of mating territories in areas frequented by females during the rut may lead to reproductive benefits for male chamois.     

Delayed sexual maturity in males of Vespa velutina

Vespa velutina var nigrithorax (Lepelletier, 1835) is an invasive predator of bees accidentally introduced in France in 2004, and it is having a serious impact on apiculture and ecosystems. Studying the reproduction of an invasive species is key to assess its population dynamic. This study explores the sexual maturation of V. velutina males and the evolution of their fertility. The main studied parameters were physiologic (spermiogenesis, spermatogenesis) and anatomic (testes size and structure, head width). Two populations of males were described based on their emergence period: early males in early summer or classic males in autumn. Each testis has an average of 108 testicular follicles. Spermatogenesis is synchronous, with only 1 sperm production wave, and completed, on average, at 10.3 d after emergence with the degeneration of the testes. The sperm counts in seminal vesicles of mature males are 3 × 10⁶ in October/November and 0.8 × 10⁶ in June. In comparison, females store 0.1 × 10⁶ sperm in their spermathecae. The early males emerged from colonies made by fertilized queens. The reproductive potential of these early males seemed limited, and their function in the colony is discussed. The sperm stock evolution in autumn males suggests the occurrence of a reproductive pattern of male competition for the access to females and a single copulation per male. The synchronicity of male and foundress emergences and sexual maturation is of primary importance for the mating success and the future colony development.     

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.     

Effect of different seasons on concentration of plasma luteinizing hormone and seminal quality vis-à-vis freezability of buffalo bulls (Bubalus bubalis)

Seasonal variations in semen quality, freezability and plasma luteinizing hormone (LH) levels were studied between summer and spring. Semen volume, density and initial sperm motility did not differ significantly between different seasons. Plasma LH decreased between summer and spring but the differences were, however, not significant. Pre-freezing motility did not differ significantly but post-freezing motility varied significantly (P<0.01) between seasons. Post-freezing motility was lowest during summer and highest during winter. It can be concluded that summer spermatozoa may be fragile and cannot withstand freezing stress. To increase reproductive efficiency in buffalo during summer, semen should be frozen during winter and spring and used during hot weather conditions. Seasonal variations in plasma LH levels were insignificant.     

Light and electron microscopic studies on the seminal secretions and the vas deferens of the penaeiodean shrimp,Sicyonia ingentis

Unlike the other penaeiodean shrimp, the ridge back shrimp, Sicyoniaingentis does not produce a spermatophore, but transfers sperm suspended in seminal plasm. This paper reports on the histomorphology and ultrastructure of the vas deferens with reference to its functional role in secreting the sperm bearing materials. The vas deferens is divisible into proximal secretory, mid storage and distal ejaculatory regions. The epithelial cells lining the proximal vas deferens are comprised of secretory and absorptive cell types. The loose sperm cells found in the lumen of this region are in an immature condition, and are agglutinated into a compact mass with signs of spermiogenesis in the mid vas deferens. The epithelial cells lining the mid vas deferens are short flattened cells. The distal vas deferens is ensheathed by muscular fibres. The inner epithelial cells are highly secretory and contain numerous microvilli at the luminal end. The sperm cord gets liquefied in this region facilitating the transfer of sperm in liquid form to the female during mating.     

Hormonal independence of courtship behavior in the male garter snake

Garter snakes exhibit a dissociated reproductive tactic in which gonadal activity is minimal at the time of mating, increasing only after the breeding season has ended. Experiments are presented demonstrating that neither short-term nor longterm castration affects courtship behavior in adult male red-sided garter snakes (Thamnophis sirtalis parietalis). So long as males have passed through a low-temperature dormancy period (hibernation), castration either shortly after emergence in the spring, or before entering winter dormancy in the fall, does not prevent the display of intense courtship behavior on emergence. Similarly, males castrated during mating activity the previous spring prior to the annual testicular growth phase actively courted females on emergence from hibernation. Males adrenalectomized and castrated during low-temperature dormancy also courted females on emergence. Hypophysectomy during or before low-temperature dormancy did not prevent males from displaying high-intensity courtship behavior on emergence from hibernation. Treatment with sex steroid hormones, as well as hypothalamic and pituitary hormones, and a variety of neural and metabolic affectors also fails to elicit courtship behavior in noncourting males during the summer. It was concluded that causal mechanisms controlling courtship behavior in the red-sided garter snake are fundamentally different, at least at the physiological level, from those mechanisms described for many laboratory and domesticated species.     

Seasonal changes of semen quality and freezability in Franches-Montagnes stallions

The objective of this study was to investigate seasonal changes of semen quality parameters in Franches-Montagnes stallions and to compare the freezability of ejaculates collected in autumn and winter. Experiments were performed using 15 stallions from the National Stud Farm in Avenches (Switzerland). Ejaculates were collected and evaluated every month during 1 year as well as cryopreserved in autumn and winter (September to February). In fresh semen the gel-free volume, concentration, motility and morphology (normal sperm, major defects, vacuoles and acrosome defects) were evaluated and in frozen-thawed semen the motility as well as the viability (SYBR-14/PI) were performed. To analyse seasonal differences four periods of 3 months each were defined as autumn (September, October, November), winter (December, January, February), spring (March, April, May) and summer (June, July, August). During the 1-year experiment all fresh semen quality parameters demonstrated a clear seasonal and individual pattern. The gel-free volume was significantly (P<0.05) higher in spring and summer compared to autumn and winter while sperm concentration was significantly (P<0.05) lower in spring than at any other time of the year. Total sperm number was significantly (P<0.05) higher and sperm motility significantly (P<0.05) lower in summer than in other seasons. Regarding sperm morphology, normal sperm was significantly (P<0.05) higher in autumn than in winter and summer and major defects were lowest (P<0.05) in autumn. In frozen-thawed semen motility was significantly (P<0.05) improved in the ejaculates collected in autumn compared to winter, while viability showed no obvious differences. Our results clearly demonstrate that individual and seasonal differences occurred in semen quality of Franches-Montagnes stallions. Ejaculates collected in autumn (September, October, November) demonstrated good quality, especially regarding sperm morphology, and were more suitable for cryopreservation because of better motility in frozen-thawed semen collected during autumn than in winter.     

The reproductive ecology of the invasive Asian paddle crab,Charybdis japonica (Brachyura: Portunidae), in northeastern New Zealand

The Asian paddle crab, Charybdis japonica, native to the northwest Pacific, is an invasive species that has established populations within northeastern New Zealand. Here, we provide a detailed examination of C. japonica's reproductive seasonality and gametogenesis, sizes at physiological maturity, and sex ratios outside its native range. Trapping in the Weiti River Estuary, Whangaparoa (36°38.4′S, 174°43.6′E) from February 2010 to May 2012 indicated a male‐biased population. Reproductive seasonality largely depended on female condition, since males contained ripe spermatozoa year‐round. Female gametogenesis began during late autumn, with oocyte development occurring throughout winter to early spring. Based on the presence of mature gametes during late winter and the appearance of gravid females in early November, mating began during early spring, with spawning in mid‐spring. Spawning coincided with a large drop in the gonad index, and occurred between sea surface temperatures of 17–22°C and 11.75–13.5 h day length. Females remained reproductive for up to 5 months of the year. Histological observation suggested that CW50 (the carapace width at which 50% of the population is mature) for females was 46.39 mm, while CW50 for males could not be determined due to a paucity of immature males. Histological analysis also suggested that females of C. japonica could produce store sperm and multiple broods annually.     

Evidence for true fall-mating in Japanese newt Cynops pyrrhogaster

The mating season of Japanese newt Cynops pyrrhogaster is generally thought to occur once a year in spring to early summer, during the months of April to June, as in many other Japanese amphibians. However, in fall, from September to October, we often observed breeding colored males demonstrating a mating behavior with females in the field. In this study, in order to identify their true mating season, we anatomically and histologically investigated the annual maturation cycle of gonads and reproductive organs, including cloacal spermathecae in females, and, using a molecular marker, identified the seasonal origins of sperm, which are released in spring to perform insemination. We found that, in fall, ovaries are somewhat immature, while the testes were mature and the sperm already stored in the deferent ducts. Females stored a significant amount of sperm in around 80% of the spermatechae examined in October and 100% in December. When artificially ovulated in March before contact with male partners after hibernation, the females spawned fertilized eggs and these developed normally. Finally, we identified heterozygous genotypes of the visual pigment gene for the two different population types in the embryos, which were derived from a female who established contact with males of the same population in fall and then switched to males from another population until oviposition in spring. We therefore, conclude that the true mating season of this species occurs from fall to early summer, interrupted only by winter, and lasts six months longer (from October to June) than generally believed.