Spermathecae of Salamandrina terdigitata (Amphibia: Salamandridae): Patterns of sperm storage and degradation

The spermathecae of female Salamandrina terdigitata were observed using light and transmission electron microscopy during the fallspring period of sperm storage and secretory activity and during the summer stasis. When sperm are stored inside the spermathecae, the product synthesized by spermathecal epithelial cells is exported into the lumen, where it bathes the sperm. During sperm storage some spermatozoa undergo degradation by the spermathecal epithelium. This process, which includes sperm capture by the apical microvilli, formation of endocytic vacuoles and production of lysosomes, becomes prominent shortly after oviposition. In many instances, cells filled with vacuolized spermatozoa and/or residual bodies undergo desquamation from the spermathecal epithelium and enter the lumen together with residual sperm. Desquamated cells, together with residual sperm, are a common feature in the spermathecal lumina at the end of the egg-laying season. Concomitant to the activity of the spermathecal epithelium, macrophages move into the spermathecae from the stroma and contribute to the degradation of both the residual sperm and desquamated epithelial cells. As a result of this degradation activity, spermathecae observed during the short summer stasis appear devoid of secretory product and sperm. By late summer, however, the spermathecae already show early signs of an imminent resumption of biosynthetic activity. © 1995 Wiley-Liss, Inc.     

Function of the spermathecal muscle in Chelymorpha alternans Boheman (Coleoptera: Chrysomelidae: Cassidinae)

Abstract. When the spermathecal muscle of a virgin female Chelymorpha alternans Boheman (Coleoptera: Chrysomelidae) was cut, the number of spermatozoa transferred in a single mating to the spermatheca and the spermathecal duct was not affected, but their distribution differed. Cutting the spermathecal muscle also reduced egg fertility. Eggs from females with a cut muscle showed a lower average percentage fertilization. Longer delays in oviposition after removal of the spermathecal muscle were associated with higher proportions of infertile eggs.     

Sensory trap as the mechanism of sexual selection in a damselfly genitalic trait (Insecta: Calopterygidae)

During copulation, males of some calopterygid damselfly species displace the sperm stored in the spermatheca: the male genital appendages enter into the spermathecal ducts and physically remove sperm. In Calopteryx haemorrhoidalis, the genital appendages are too wide to penetrate the spermathecae, but males use a different mechanism in which the aedeagus stimulates the vaginal sensilla that control spermathecal sperm release. Since these sensilla are used during egg fertilization and oviposition, it was hypothesized that this function evolved before the male stimulatory ability. I investigated this using Hetaerina cruentata, a species whose position in the Calopterygidae phylogeny is more basal than Calopteryx. Given this position and having determined that males of this species are not able to displace sperm of their conspecific females during copulation, it was expected that H. cruentata females would eject sperm when stimulated with the aedeagi of C. haemorrhoidalis but not when stimulated with the aedeagi of their conspecifics. This prediction was confirmed. In order to investigate the widespread nature of this result, some other Calopteryx species-Calopteryx xanthostoma and Calopteryx virgo-were investigated. The results were similar to those of H. cruentata: conspecific males were unable to stimulate their females, but females ejected sperm when stimulated with C. haemorrhoidalis aedeagi. Morphometric analysis suggests that the mechanistic explanation for the stimulatory ability of C. haemorrhoidalis genitalia is that the aedeagal region that makes contact with the vaginal sensilla is wider in C. haemorrhoidalis than in the other species. These results suggest that the sensory "bias" shown and shared by H. cruentata, Calopteryx splendens, C. virgo, and C. haemorrhoidalis females represents an ancestral condition and that the male stimulatory ability is absent in the evolutionary history of the clade. These pieces of evidence as well as another one presented elsewhere, which indicates that C. haemorrhoidalis males vary in their stimulatory ability, constitute the three criteria for a case of sexual selection via exploitation of a female sensory bias. These results also provide support to the sensory trap hypothesis that indicates that the female bias-in this case, egg fertilization and oviposition-evolved in a context different from sexual selection. Considering that the male genital appendages responsible for physically removing spermathecal sperm in other calopterygids are present in C. haemorrhoidalis, I suggest that males were once able to displace spermathecal sperm physically. Such ability may have been later impeded by a reduction in size of the spermathecal ducts. Possibly, one of the latest events in this sequence is the male's stimulatory ability. This hypothetical series of events suggests a coevolutionary scenario in which the central actor is the sperm stored in the spermathecae.     

Coevolution of sperm and female reproductive tract morphology in stalk-eyed flies

Sperm and female reproductive tract morphology are among the most rapidly evolving characters known in insects. To investigate whether interspecific variation in these traits results from divergent coevolution we examined testis size, sperm length and female reproductive tract morphology for evidence of correlated evolution using 13 species of diopsid stalk-eyed flies. We found that sperm dimorphism (the simultaneous production of two size classes of sperm by individual males) is ancestral and occurs in four genera while sperm monomorphism evolved once and persists in one genus. The length of ''long-sperm'' types, though unrelated to male body or testis size, exhibits correlated evolution with two regions of the female reproductive tract, the spermathecae and ventral receptacle, where sperm are typically stored and used for fertilization, respectively. Two lines of evidence indicate that ''short sperm'', which are probably incapable of fertilization, coevolve with spermathecae. First, loss of sperm dimorphism coincides phylogenetically with reduction or loss of spermathecae. Second, evolutionary change in short-sperm length correlates with change in spermathecal size but not spermathecal duct length or ventral receptacle length. Morphological coevolution between sperm and female reproductive tracts is consistent with a history of female-mediated selection on sperm length.     

Coevolution of male and female genitalia in stalk-eyed flies (Diptera: Diopsidae)

The present study investigates the coevolution of a particular male genital process and the female spermathecal ducts in a clade of stalk-eyed flies (Diptera, Diopsidae) and debates the underlying evolutionary mechanisms. The fine morphology and interaction of the male and female genitalic structures are reconstructed from serial sections of mating pairs in one of the species. It is found that the male genital process traverses the common spermathecal duct to enter the base of one of the separate spermathecal ducts during the mating. Spermatozoa and accessory secretions are not transferred through the male genital process but can be discharged only from the male gonopore near its base. A detailed morphometric study reveals low intraspecific variation and hypoallometry of the male genital process. Across 17 species studied comparatively, the lengths of the male genital process and the female common and separate spermathecal ducts are highly variable. The length of the male genital process is correlated significantly with that of the female common spermathecal duct, but not with that of the separate spermathecal ducts. Based on the combined evidence it is concluded that the male genital process and the female common spermathecal duct have coevolved, and that sexual selection by cryptic female choice constitutes a possible and parsimonious explanation for their coevolution. Alternative or additional explanations in terms of sexually antagonistic coevolution cannot be ruled out conclusively, but are not supported by the available evidence.     

Complex genital system of a haplogyne spider (Arachnida, Araneae, Tetrablemmidae) indicates internal fertilization and full female control over transferred sperm

The female genital organs of the tetrablemmid Indicoblemma lannaianum are astonishingly complex. The copulatory orifice lies anterior to the opening of the uterus externus and leads into a narrow insertion duct that ends in a genital cavity. The genital cavity continues laterally in paired tube-like copulatory ducts, which lead into paired, large, sac-like receptacula. Each receptaculum has a sclerotized pore plate with associated gland cells. Paired small fertilization ducts originate in the receptacula and take their curved course inside the copulatory ducts. The fertilization ducts end in slit-like openings in the sclerotized posterior walls of the copulatory ducts. Huge masses of secretions forming large balls are detectable in the female receptacula. An important function of these secretory balls seems to be the encapsulation of spermatozoa in discrete packages in order to avoid the mixing of sperm from different males. In this way, sperm competition may be completely prevented or at least severely limited. Females seem to have full control over transferred sperm and be able to express preference for spermatozoa of certain males. The lumen of the sperm containing secretory balls is connected with the fertilization duct. Activated spermatozoa are only found in the uterus internus of females, which is an indication of internal fertilization. The sperm cells in the uterus internus are characterized by an extensive cytoplasm and an elongated, cone-shaped nucleus. The male genital system of I. lannaianum consists of thick testes and thin convoluted vasa deferentia that open into the wide ductus ejaculatorius. The voluminous globular palpal bulb is filled with seminal fluid consisting of a globular secretion in which only a few spermatozoa are embedded. The spermatozoa are encapsulated by a sheath produced in the genital system. The secretions in females may at least partly consist of male secretions that could be involved in the building of the secretory balls or play a role in sperm activation. The male secretions could also afford nutriments to the spermatozoa.     

Sperm supply and its utilization in doubly inseminated flies, Culicoides melleus.

By using the irradiated male technique, utilization of sperm in doubly inseminated Culicoides melleus was studied and compared with the contributions of sperm made by each male. Contributions were calculated from direct counts of sperm known to reach the female common spermathecal duct. Based on these determinations, the first male contributed about 65 per cent of the total sperm supply, the second male 35 per cent. Segregation of progeny between the two males was in remarkably close agreement to their respective contributions of sperm. Although there was slight evidence that a small proportion of the second male's sperm do not reach the spermathecae, the results suggested that complete mixing of sperm occurred in the female storage organs before oviposition.     

日本北海道虻类雌性外生殖器形态(双翅目：虻科)(英文)

【目的】利用日本北海道虻类评估和验证外生殖器在分类学上的意义。【方法】将虻类成虫标本浸渍在生理盐水中并置于双目显微镜下通过针和镊子在培养皿中进行解剖并绘图,观察第9背板、第10背板、尾叶、第8腹板、受精囊、受精囊管及生殖叉器的形态特征。【结果】在日本北海道共记录了虻科(Tabanidae) 3亚科7属38种。我们观察并描述了3亚科其中的6属24种的雌性外生殖器的主要特征。亚科之间存在明显差异;然而在一般情况下属之间很难建立一种方法来确定共同点;种之间只有在斑虻属Chrysops中有相似之处,其他属中则比较多样化。因此,亚科鉴定根据第9背板、第8腹板及受精囊足以进行区分,属及种鉴定需要结合第9背板、第10背板、尾叶、第8腹板、受精囊、受精囊管及生殖叉器各自的特征组合在一起才能区分开来。我们也制作了虻类外生殖器的检索表。【结论】和许多其他昆虫一样,外生殖器是虻科的重要分类特征,对于促进分类学和系统学的发展具有重要意义。本研究首次对分布在日本北海道的虻科雌性外生殖器进行了系统研究。     

The importance of the spermathecal duct in bumblebees

The elongated spermathecal duct of bumblebees has been studied in hibernating queens, queens shortly after hibernation, mature egg-laying queens and uninseminated queens captured during summer, and workers. Only rather small size differences are found when comparing spermathecae of queens and workers. Clear differences between bumblebee queens and workers are found when comparing the histochemistry of the spermathecal ducts. Adult queens, regardless of age and reproductive status have spermathecal ducts that contain PAS positive material, whereas workers do not. It is suggested that the polysaccharides in the spermathecal ducts of queens are necessary as a source of energy for the rapid activation of spermatozoa passing through the duct prior to oocyte fertilization. An ultrastructural investigation revealed the presence of high glycogen content in the cells lining the duct of queens. Assuming that sperm cells are kept in a rather inactive state in the reservoir, the carbohydrate (glycogen) probably serves as an energy source for the sperm. The comparatively increased spermathecal duct length of bumblebees may increase the retention time of sperm inside the lumen.     

Structural organization of the copulation site in the medfly Ceratitis capitata (Diptera: Tephritidae) and observations on sperm transfer and storage

The copulation site of the medfly Ceratitis capitata was investigated at anatomical and ultrastructural levels. It consists of the anterior vagina, with a ventral fertilization chamber and a dorsal insemination pocket into which the two spermathecal ducts open. The fertilization chamber is an organ comprised of a number of alveoli that in virgin females are filled with a filamentous secretion, whereas in mated females contain sperm bundles. Through study of the internal morphology of the aedeagus, its position in the anterior vagina, and the direct observation of sperm transfer and storage, we confirmed that sperm are ejaculated through two gonopores at the top of the distiphallus and another at the base of the genital rod. The sperm flow dorsally into the insemination pocket and ventrally into the fertilization chamber. During copulation, the two spermathecae and the fertilization chamber are progressively filled with spermatozoa.     

The fine structure of the female reproductive system of Zorotypus caudelli Karny (Zoraptera)

The general structure of the female genital system of Zorotypus caudelli is described. The ovarioles are of the panoistic type. Due to the reduction of the envelope (tunica externa) the ovarioles are in direct contact with the hemolymph like in some other insect groups, Plecoptera included. The calices are much larger in Z. caudelli then in Zorotypus hubbardi and their epithelial cells produce large amounts of secretions, probably protecting the surface of the eggs deposited on the substrate. Eggs taken from the calyx bear a series of long fringes, which are missing in the eggs found in the ovariole, and in other zorapteran species. The long sperm of Z. caudelli and the long spermathecal duct are likely related to a sexual isolating mechanism (cryptic female choice), impeding female re-mating. The apical receptacle and the spermathecal duct - both of ectodermal origin - consist of three cell types. In addition to the cells beneath the cuticle lining the lumen, two other cell types are visible: secretory and canal cells. The cytoplasm of the former is rich in rough endoplasmic reticulum cisterns and Golgi complexes, which produce numerous discrete dense secretory bodies. These products are released into the receiving canal crossing the extracellular cavity of secretory cells, extending over a series of long microvilli. The secretion is transported towards the lumen of the apical receptacle of the spermatheca or to that of the spermathecal duct by a connecting canal formed by the canal cells. It is enriched by material produced by the slender canal cells. Before mating, the sperm cells are enveloped by a thick glycocalyx produced at the level of the male accessory glands, but it is absent when they have reached the apical receptacle, and also in the spermathecal duct lumen. It is likely removed by secretions of the spermatheca. The eggs are fertilized at the level of the common oviduct where the spermathecal duct opens. Two micropyles at the dorsal side of the equator level possibly facilitate fertilization. The presence of these two micropyles is a presumably derived feature shared with Phasmatodea. The fine structure of the female reproductive system of Z. caudelli does not allow to assess the phylogenetic position at the present stage of knowledge. The enlarged calyx and the temporary presence of long fringes on the eggs are potential autapomorphies of Z. caudelli or may indicate relationships with other Zorotypus species.     

Spermathecal cytology of Ambystoma opacum (Amphibia: Ambystomatidae) and the phylogeny of sperm storage organs in female salamanders

Sperm storage glands, spermathecae, were examined from mated female Ambystoma opacum during the breeding season. No differences occur in the spermathecal ultrastructure of individuals sacrificed prior to oviposition and those sacrificed within 3 days of removal from tended clutches of recently oviposited eggs. The simple tubuloalveolar glands produce two types of secretory vacuoles. Apical secretory vacuoles contain glycosaminoglycans for export into the lumen to bathe stored sperm, perhaps providing the chemical/osmotic environment necessary for sperm quiescence. The other type of secretory vacuole contains an unsaturated lipid that is produced for export into the connective tissue surrounding the spermathecae. The role of this secretion may involve the contraction of myoepithelial cells, resulting in sperm expulsion. Some sperm undergo degradation in the spermathecal epithelium, and an interepithelial leukocyte was observed in one specimen. Apical secretory vacuoles and sperm are absent from the spermathecae of a specimen sacrificed 62 days after removal from a tended egg clutch. This is the first report on the spermathecal cytology of a salamander from the Ambystomatidae, and comparisons with salamanders from other families provide a morphological basis for considering spermathecae polyphyletic within the Caudata. © 1993 Wiley-Liss, Inc.     

A light and electron microscopical study of the spermathecae and ventral receptacle of Anastrepha suspensa (Diptera: Tephritidae) and implications in female influence of sperm storage

Female insects with multiple sperm storage organs may potentially influence patterns of paternity by differential storage of sperm from competing males. The Caribbean Fruit Fly, Anastrepha suspensa, stores sperm differentially with respect to its three spermathecae. To understand the mechanisms and processes responsible for patterns of sperm storage and use in A. suspensa, details of the fine structure of female sperm storage organs were resolved by UV-light microscopy, confocal microscopy, tissue sectioning, and scanning and transmission electron microscopy. Structures not previously described for this species include a ventral receptacle for sperm storage and osmoregulation, a conical-shaped valve at the junction between the spermathecal capsules and their ducts, laminar and granular secretions, secretions from the signum, hemocytes surrounding the spermathecae, and spermathecae with sclerotized, hollow projections that terminate in single glandular cells. The independent organization of sperm storage organs, spermathecal ducts, associated musculature, gland cells, and innervation offer possible mechanisms by which sperm movement may be influenced by females. The implications of these structures for insemination and fertilization events are discussed.     

Morphology of the female reproductive system of European pea crabs (Crustacea,Decapoda, Brachyura,Pinnotheridae)

Commensal pea crabs inhabiting bivalves have a high reproductive output due to the extension andfecundity of the ovary. We studied the underlying morphology of the female reproductive system in the Pinnotheridae Pinnotheres pisum, Pinnotheres pectunculi and Nepinnotheres pinnotheres using light microscopy and transmission electron microscopy (TEM). Eubrachyura have internal fertilization: the paired vaginas enlarge into storage structures, the spermathecae, which are connected to the ovaries by oviducts. Sperm is stored inside the spermathecae until the oocytes are mature. The oocytes are transported by oviducts into the spermathecae where fertilization takes place. In the investigated pinnotherids, the vagina is of the “concave pattern” (sensu Hartnoll 1968 ): musculature is attached alongside flexible parts of the vagina wall that controls the dimension of its lumen. The genital opening is closed by a muscular mobile operculum. The spermatheca can be divided into two distinct regions by function and morphology. The ventral part includes the connection with vagina and oviduct and is regarded as the zone where fertilization takes place. It is lined with cuticle except where the oviduct enters the spermatheca by the “holocrine transfer tissue.” At ovulation, the oocytes have to pass through this multilayered glandular epithelium performing holocrine secretion. The dorsal part of the spermatheca is considered as the main sperm storage area. It is lined by a highly secretory apocrine glandular epithelium. Thus, two different forms of secretion occur in the spermathecae of pinnotherids. The definite role of secretion in sperm storage and fertilization is not yet resolved, but it is notable that structure and function of spermathecal secretion are more complex in pinnotherids, and probably more efficient, than in other brachyuran crabs. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.     

Seasonal variation in genital and body size, sperm displacement ability, female mating rate, and male harassment in two calopterygid damselflies (Odonata: Calopterygidae)

Sperm competition is a pervasive force. One adaptation is the male ability to displace the rivals' sperm that females have stored from previous copulations. In the damselfly, Calopteryx haemorrhoidalis asturica , males with wider aedeagi displace more spermathecal sperm. The present study documents that the same mechanism operates in another damselfly, Hetaerina americana . However, this genital width in both species decreases along the season, but late-emerging females have more sperm displaced than early-emerging females. Because territorial males mated more and were larger in body and genital size than nonterritorial males, late-season females mated with considerably larger males with respect to female size and this produced higher sperm displacement. Assuming female benefits from storing sperm but that such benefit does not prevail if males displace sperm, it is predicted that, along the season, females will mate less and male harassment (in terms of male mating attempts and oviposition duration) will increase. These predictions were corroborated. In H. americana , it was also tested whether spermathecal sperm became less viable along the season. The results obtained did not corroborate this. This is the first evidence indicating that season affects sperm displacement ability and female mating frequency due to changes in male body and genital size.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 815–829.     

Sperm storage and degradation in the spermathecae of the salamander Eurycea Cirrigera

Spermathecae are exocrine glands in the roof of the female cloaca that store sperm. Cytological and histochemical data indicate that the one type of secretion into the lumen is a glycoprotein. After a period of stasis in the summer, production of the secretion is initiated in the fall, coincident with an increase in ovarian follicular size. By the time of maximal follicular development and most intense mating activity in March and April, the spermathecal epithelium is filled with secretory granules. The secretory material is released into the lumen, enveloping the sperm. Many sperm remain in the spermathecae after oviposition, and most of these sperm are degraded in the spermathecal epithelium or pass through interruptions in the spermathecal walls caused by desquamation. Sperm in contact with the stromal environment are phagocytized by leukocytes. Some sperm, however, may survive in the lumen until at least the following fall. These sperm retain normal cytology, but whether or not they remain fertile and intact until a subsequent ovipository cycle is unknown.     

The anatomy of fertilization in the yellow dung fly Scathophaga stercoraria

Female yellow dung flies, Scathophaga stercoraria, can influence the traffic of sperm stored in their spermathecae to the site of fertilization in the bursa copulatrix. However, the anatomical mechanisms employed are largely unknown. We investigated the anatomy of the female genital tract, seeking structures involved in sperm transfer and egg fertilization. We found a membranous structure descending from the ends of the spermathecal and accessory gland ducts into the bursa copulatrix. We call this the prolatus. Sperm accumulate in the prolatus during oviposition. When an egg is in the bursa the egg micropyle, rather than being aligned towards the dorsal openings of the spermathecal ducts, lies on the opposite, ventral side. We also confirm the presence, and suggest a function for, a cuticularized pouch on the ventral wall of the anterior bursa copulatrix. This pouch, plus a previously undescribed chamber, may be homologous to the ventral receptacle/fertilization chamber found in other dipterans. Further, we describe a translucent cap, apparently transversed by channels, covering the micropyle. Sperm were observed to aggregate on and in the micropyle cap, which appears to attract and hold sperm. We interpret the prolatus as a structure that allows an ovipositing female to transfer a few sperm onto the ventral bursal wall and thus, indirectly, onto the micropyle cap. Such anatomy potentially gives the female a large degree of control over sperm traffic from storage to the site of fertilization.     

Prevalence of bacteria in the spermathecae of female snow crab, Chionoecetes opilio (Brachyura: Majidae)

The spermathecal contents of primiparous, multiparous and barren female snow crabs were observed by a scanning electron microscope. Bacteria colonies were observed with a significantly higher frequency in the spermathecae of primiparous and old barren females. Bacteria infect the spermathecae and destroy the spermatophores and spermatozoa inside. These observations suggest that bacteria in the spermathecae do not exclude opportunistic microbes by modifying pH of the medium as suggested in the literature. The prevalence of bacteria in primiparous and old barren females suggests that they infect individuals with a weak anti-microbial protection. The absence of bacteria in the highly acidic seminal fluid derived from males upon copulation suggests that it may provide anti-microbial protection. Bacteria do not seem to be able to survive in an anaerobic environment for a long period.     

Sperm motility and spermathecal filling in lower diptera

A recently completed study of sperm transfer and spermathecal filling in Culicoides melleus (Ceratopogonidae) provided evidence that the spermathecae create an incoming current by fluid absorption. This current, rather than sperm motility, was thought to accomplish transfer of spermatozoa from spermatophore to spermathecae. This review discusses the approach used to assess the role of sperm motility, as applied critically to available observations in other lower Diptera. Aedes aegypti (Culicidae), Simulium decorum (Simuliidae) and Plecia nearctica (Bibionidae) are considered. The results suggest that sperm motility very probably does not contribute to spermathecal filling in these species, and that fluid absorbtion is the more likely mechanism. Certain physical properties of the female reproductive systems are discussed in the light of this conclusion.