Detrimental effects of excessive fatty acid secretion on female sperm storage in chickens

Background:Female sperm storage(FSS),the maintenance of sperm inside the female reproductive tract for an extended period of time,is pervasive among organisms with internal fertilization.Because FSS enables asynchronous mating and fertilization,it could be extremely important to reproduction.However,the physiological mechanisms underlying prolonged preservation and maintenance are poorly understood.Here,we used chicken,a typical oviparous animal,to determine the mechanisms ensuring sperm functionality in sperm storage tubules(SSTs).Results:We performed an insemination experiment on over two thousand hens at two periods,and found that the FSS capabilities varied widely among individuals.Except for the differences in the SST density between the two groups with distinct FSS abilities,we quantitatively profiled small-molecule metabolites derived from SST cells,and identified 28 metabolites with differential expression.In particular,high levels of lipids,fatty acids and lipid peroxidation product were observed in hens with low FSS capability.Pathway analysis showed that these differential metabolites were significantly enriched in the biosynthesis of unsaturated fatty acids.Moreover,we detected the total antioxidant capacity and lipid peroxidation level of SSTs,and found that chickens with a lower FSS ability had a significantly higher content of lipid peroxidation end-product,which was 2.4-fold greater than chickens with a higher FSS capability,and no significant difference was found in the total antioxidant capacity between these two groups.Conclusions:Our findings reveal that the long-term storage of sperm and the maintenance of their function in the female reproductive tract require an adequate microenvironment.The superabundance of fatty acids secreted by SST cells had detrimental effects on sperm storage in the female reproductive tract.Lipid peroxidation produces toxic biological substances that may cause irreversible damage to resident spermatozoa,resulting in short-term sperm retention and decreased fertility.Our findings provide new avenues for studying sperm storage and sustaining fertility.

Role of the epididymis in sperm competition

Although it is generally understood that the testes recruited kidney ducts for reproductive function during the evolution of vertebrates, little is understood of the biological significance of the adaptation. In the context of the evolution of the mammalian epididymis, this report provides evidence that a major role of the epididymis is to enhance a male＇s chance of achieving paternity in a competitive mating system. A unique example of sperm cooperation in monotremes is used as evidence that the epididymis produces sperm competition proteins to form groups of 100 sperm into bundles that have a forward motility nearly thrice that of individual spermatozoa. As it required 3-h incubation in vitro under capacitation conditions to release motile sperm from the bundles, it is suggested that the monotremes provide an example of capacitation that is quite different from capacitation in higher mammals. It is suggested that variation between species in the intensity of sperm competition could explain the variation that occurs between species in the amount of post-testicular sperm maturation and storage in the epididymis, an explanation of why the human epididymis does not play as important a role in reproduction as the epididymis of most mammals. （Asian J Androl 2007 July; 9： 493-499）

Histological and immunocytochemical study of deferens ducts in the Chinese rat snake (Zaocys dhumnades)

To investigate the relationship between structure and function of the deferens ducts in the Chinese rat snake （Zaocys dhumnades）, morphological changes within an annual cycle were observed by routine histological techniques. Also, the correlation of androgen receptor （AR）, estrogen receptor （ER）, progesterone receptor （PR） and aromatase （Ar） expressions in the vas deferens and testis were studied immunohistochemically. To confh＇m that the sperm and the spherical structure existed in deferens ducts, we also used routine histological technique observed deferens ducts in the Striped-tailed rat-snake （Elaphe taeniura）, Red-banded snake （Dinodon rufozonatum）, and Tiger-spotted neck- troughed snake （Rhabdophis tigrina lateralis）. The results showed that the deferens ducts of the Chinese Rat Snake were composed of efferent duct, epididymal duct and vas deferens. Efferent duct contained sperm from August-October, and the sperm were observed in the epididymal duct from August-the following January. Throughout the year （except July） a large number of sperm were present in the vas deferens where a previously unreported spherical structure formed by spermatids was observed, which showed no significant differences in the IOD values of AR-, ER-, PR- and Ar- immunoreactivities. Since the spermatids in the spherical structure were undergoing spermatogenesis and this phenomenon also existed in the Striped-tailed rat-snake and Red-banded snake, the term, seminiferous spherule, was named for this spherical structure This study demonstrated that the testis was the main site for snake spermiogenesis, and the seminiferous spherule in vas deferens was the other Both the epididymis and vas deferens stored sperm; however, the vas deferens was the main organ for sperm storage.

Transcriptome profile analysis of the accompanying migratory parasitic wasp Aenasius bambawalei(=Aenasius arizonensis girault)(Hymenoptera:Encyrtidae):Genes related to fertilization involved at different stage of ovary development

Age-related declines in fertilization success have been reported for a wide range of species.The fertilization of parasitic wasps is closely related to egg production and sperm storage.Aenasius bambawalei(Hymenoptera:Encyridae)is a key parasitic wasp of the important invasive mealybug Phenacoccus solenopsis(Hemiptera:Pseudococcidae).The female offspring ratio of this parasitic wasp was declined with parental age in mass rearing under laboratory conditions.To investigate the molecular mechanisms involved in the reproduction of A.bambawalei,an extensive analysis of the impact of age on transcriptome profile of mated ovaries of this wasp was performed by comparing the gene expression profiles of various maternal ages:the early stage(ES),the intermediate stage(IS),and the advanced stage(AS).In total,358 differentially expressed genes were identified,with 17.60%(63 genes)of the changes associated with greater expression in fertilization.Moreover,the expression of serine protease 47 precursor,serine protease inhibitor 3/4,glucose dehydrogenase,fatty acyl-CoA reductase 1-like,major royal jelly,and acyl-CoA delta(11)desaturase-like was detected by real-time fluorescence quantitative(RT-qPCR).The results showed that fertilization related genes exhibited a stage-specific pattern.Egg production and sperm storage genes in A.bambawalei were significantly modified in the transcriptome,providing a starting point for the genetic dissection of fertilization.

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.