Female Spermathecal Duct Research Articles

Sperm competition in yellow dung flies: No consistent effect of sperm size.

The male competition for fertilization that results from female multiple mating promotes the evolution of increased sperm numbers and can impact sperm morphology, with theory predicting that longer sperm can at times be advantageous during sperm competition. If so, males with longer sperm should sire more offspring than competitors with shorter sperm. Few studies have directly tested this prediction, and findings are inconsistent. Here we assessed whether longer sperm provide a competitive advantage in the yellow dung fly (Scathophaga stercoraria; Diptera: Scathophagidae). Initially, we let brothers with different temperature-mediated mean sperm lengths compete - thus minimizing confounding effects of genetic background - and found no clear advantage of longer sperm. We then used flies from lines subjected to bidirectional selection on phenoloxidase activity that had shown correlated evolutionary responses in sperm and female spermathecal duct lengths. This experiment also yielded no main effect of sperm size on siring success. Instead, there was a trend for a shorter-sperm advantage, but only when competing in females with longer spermathecal ducts. Our data corroborated many previously reported findings (last-male precedence, effects of copula duration and body size), suggesting our failure to find sperm size effects is not inherently due to our experimental protocols. We conclude that longer sperm are not competitively superior in yellow dung flies under most circumstances, and that, consistent with previous work, in this species competitive fertilization success is primarily determined by the relative numbers of sperm competing.

Descriptive Morphology of Male and Female Genitalia of the Long-horned Grasshopper in the Tribe Aphractini (Orthoptera: Tettigoniidae), with a Key to the Genera.

The male and female genital morphologies of the tribe Aphractini are presented in this study. Four species are included: Aphractus acuminatus, Paraphractus abbreviatus, Polycleptidella chilensis and Polycleptis scutellifera. A dichotomous key to the genera is provided. The lengths between the female spermathecal duct and titillatory articulated processes are similar within species but differ between them. Therefore, we propose that the function of these organs could be associated with the sperm removal strategy.

How Does the Male Penisfilum Enter the Female Copulatory Pore in Hangingflies?

Hangingflies are characterized by the interesting nuptial feeding behavior and unusual belly-to-belly hanging mating position. However, the mating behavior and the copulatory mechanism remain poorly known for Bittacidae, especially how the elongated male penisfilum enters the copulatory pore of the female. In this study, the mating behavior and copulatory mechanism of Terrobittacus implicatus (Huang and Hua, 2006) were investigated to reveal the functional morphology of hangingfly genitalia. The results show that the male provides a prey as a nuptial gift to the female and twists his abdomen about 180° to form a belly-to-belly hanging mating position. During the penisfilum-entering process, the male epandrial lobes clamp the female subgenital plate with the aid of the female abdomen swelling. Then the male locates the female copulatory pore through his upper branch of the proctiger and inserts his penisfilum into the female spermathecal duct in cooperation with the short setae on the groove of the proctiger. The female subgenital plate where the epandrial lobes clamp is strongly sclerotized and melanized. The copulatory mechanism of Terrobittacus is briefly discussed.

Taxonomic review of Australian Mecyclothorax Sharp (Coleoptera, Carabidae, Moriomorphini) with special emphasis on the M. lophoides (Chaudoir) species complex

The Australian fauna ofMecyclothoraxSharp (Coleoptera: Carabidae: Moriomorphini) is reviewed, with special focus on species assigned to the monophyletic subgenus Eucyclothorax Liebherr:M.isolatus,sp. n.from Western Australia,M.mooreiBaehr,M.punctatus(Sloane),M.curtus(Sloane),M.blackburni(Sloane);M.eyrensis(Blackburn);M.peryphoides(Blackburn);M.darlingtoni,sp. n.from Queensland;M.jameswalkeri,sp. n.from Western Australia;M.lophoides(Chaudoir); andM.cordicollis(Sloane). The last six species listed above–theM.lophoidesspecies complex–have been the source of long-term confusion for taxonomists, with male genitalic characters providing trouble-free species circumscription. One new subspecies,M.lewisensisestriatus,subsp. n.from Queensland is added to the seven previously described taxa of the monophyletic subgenus Qecyclothorax Liebherr. The balance of the fauna consists of four species in the subgenus Mecyclothorax:1and2, the sister-species pairM.lateralis(Castelnau) andM.minutus(Castelnau);3,M.ambiguus(Erichson); and4,M.punctipennis(MacLeay).Mecyclothoraxfortis(Blackburn),syn. n., is newly synonymized withM.minutus.MecyclothoraxovalisSloane is recombined asNeonomiusovalis(Sloane),comb. n., and a neotype is designated to replace the destroyed holotype. Phylogenetic relationships for the AustralianMecyclothoraxare proposed based on information from 68 terminal taxa and 139 morphological characters. The biogeographic history of AustralianMecyclothoraxis deduced based the sister-group relationship betweenMecyclothoraxand theAmblytelus-related genera, with both groups hypothesized to have originated during the late Eocene. Diversification withinMecyclothoraxhas occurred since then in montane rainforests of tropical Queensland, temperate forest biomes of the southwest and southeast, and in grasslands and riparian habitats adjacent and inland from those forests. Several species presently occupy interior desert regions, though no sister species mutually occupy such climatically harsh habitats. TheM.lophoidesspecies complex exhibits profound male genitalic diversification within the context of conserved external anatomy. This disparity is investigated with regard to the functional interaction of the male internal sac flagellum and female spermathecal duct. Though limited association of flagellar and spermathecal duct configurations can be documented, several factors complicate proposing a general evolutionary mechanism for the observed data. These include:1, the occurrence of derived, elongate spermathecal ducts in three species, two of which exhibit very long male flagella, whereas males of the third exhibit a very short flagellum; and2, a highly derived and exaggerated male flagellar configuration shared across a sister-species pair even though the two species can be robustly diagnosed using external anatomical characters, other significant genitalic differences involving male parameral setation, and biogeographic allopatry associated with differential occupation of desert versus forest biomes.

Eversion and withdrawal of an intromittent organ before sexual maturation prepares male beetles for copulation.

Some species of criocerine beetles have a hyper-elongated part of the intromittent organ called a flagellum. In resting position, the flagellum is stored in a specialized internal sac in the intromittent organ. This specialized state of the flagellum and internal sac is indispensable during copulation for flagellar insertion into the female spermathecal duct for sperm transfer. However, the morphogenesis of the flagellum does not generate the active state of the flagellum; rather, the flagellum is generated in an inactive and completely coiled state. After eclosion, males of Lema coronata evert and withdraw the internal sac multiple times before sexual maturation, without mounting a female. This behaviour serves to uncoil the flagellum and guide it into the active state with the aid of surface structures on the internal sac. A closely related species, Lema dilecta, also has a long flagellum and undergoes the same behaviour to place the flagellum in the active position. However, some other species of criocerine beetles with much shorter flagella can attain the active state without exhibiting this behaviour. Based on a previously proposed phylogenetic tree, we discuss the evolutionary history of the hyper-elongation of the flagellum and associated behaviour.

Functional morphology and evolution of the hyper-elongated intromittent organ in Cassida leaf beetles (Coleoptera: Chrysomelidae: Cassidinae)

The peculiar phenomenon of hyper-elongation of intromittent organs is well known in a number of insect groups. However, the unresolved questions of how and why such a phenomenon originated independently many times continue to attract biologists’ attention. To be able to detect the evolutionary driving mechanisms that enabled insects to repeatedly acquire such a peculiarity, first of all the structural key features and the mechanics of these organs have to be determined. In the present study, the morphology of the reproductive organs of two species of the beetle genus Cassida, with a special focus on the male structures, was scrutinised in detail during copulation and at rest using different microscopy techniques. We found that the hyper-elongated structure of the intromittent organ, called flagellum, is part of the male ejaculatory duct. When the flagellum is inserted into the female spermathecal duct, longitudinal muscles of the ejaculatory duct, but not the flagellum, are shortened. These results strongly suggest that the contraction of the longitudinal muscles of the ejaculatory duct causes propulsion of the flagellum into the highly spiralled spermathecal duct of the female. The tip of the cuticular flagellum is curled up, which can suggest that its physical properties differ from those of the rest of the flagellum. Considering the preceding modelling studies, this property aids the flagellum in penetrating within the highly spiralled and very variable female duct. Based on our morphological results and in comparison with the morphology of intromittent organs of other beetles, we discuss the evolutionary origin of the hyper-elongation in the Cassida species and propose a hypothesis that explains the independent origin of the hyper-elongation of intromittent organs.

Stiffness gradient of the beetle penis facilitates propulsion in the spiraled female spermathecal duct.

It is well known that sexual selection is the main driving force of substantial diversity of genitalia found in animals. However, how it facilitates the diversity is still largely unknown, because genital morpho/physical features and motions/functional morphology of the structures in sexual intercourse are not linked for the vast majority of organisms. Here we showed the presence of material gradient and numerically studied an effect of stiffness gradient of the beetle penis during its propulsion through the female duct. We found that stiffness gradient on the penis essentially affects its propulsion. Microscopic investigation suggests the possibility that the tip of the hyper-elongated penis is softer than the rest of it, and our numerical model confirms that this type of distribution of stiffness gradient aids in faster propulsion than other types. This result indicates that previously ignored physical properties of genital materials are of crucial importance in evolutionary studies of genitalia.

Male penile propulsion into spiraled spermathecal ducts of female chrysomelid beetles: A numerical simulation approach

Genital diversification in animals is an interesting evolutionary phenomenon. Sexual selection is the main driving force behind the diversification. However, evolutionary mechanisms that have established and maintained variations in genitalia shape parameters observed in related species are not well understood. Here, for the first time, we used numerical simulations to test the hypothesis that variations in female spermathecal duct shapes among related beetle species mechanically interfere with penile propulsion in varying ways. Our numerical simulations showed that high curvature of the spiraled spermathecal ducts of the female have effects with a threshold-based interaction on male penile insertion. The relative size of spirals observed in the beetle, Cassida rubiginosa, studied here is not small enough to interfere with penile propulsion. But the model revealed that propulsion is impeded by the presence of reverse turns in spermathecal ducts. This type of morphology leads to an increase in the velocity of the propulsion but also to an increase in the propulsion energy cost for males. Our results showed that quantitative differences in spermathecal duct shape can mediate qualitative differences in penile motion. This explains, in part, the mechanism behind origin and maintenance of genital divergence among closely related species in general.

The intermediate sperm type and genitalia of Zorotypus shannoni Gurney: evidence supporting infraordinal lineages in Zoraptera (Insecta)

The sperm ultrastructure and the male and female genital apparatus of Zorotypus shannoni were examined and documented in detail, mainly using transmission electron microscopy micrographs. The findings suggest an evolutionary trend shared with Z. hubbardi and Z. impolitus. The three species are characterized by enlarged mitochondrial derivatives and related modifications. Giant sperm are probably a synapomorphy of Z. hubbardi and Z. impolitus, whereas an intermediate condition of this feature is found in Z. shannoni. The monophyletic origin of Z. caudelli, Z. magnicaudelli, Z. huxleyi and Z. weidneri is suggested by characteristically modified axonemes. The presence of extra-acrosomal material is also an unusual feature for Zoraptera, but this condition also occurs in the majority of polyneopteran groups. The long and convoluted female spermathecal duct with secretory and duct-forming cells is a constant feature in Zoraptera. The enlarged seminal receptacle suggests an evolutionary link between the male genital structures and the sperm size on one hand, and the size of the female spermatheca on the other. The small and otherwise uniform group Zoraptera exhibits a remarkable variation of sperm types and genital structures, suggesting the impact of different types of selection. It is likely that cryptic female choice plays a major role in shaping the genital apparatus.

Co-Evolution of the Mating Position and Male Genitalia in Insects: A Case Study of a Hangingfly

Hangingflies are unique for the male providing a nuptial gift to the female during mating and taking a face-to-face hanging copulation with the female. Their male genitalia are peculiar for an extremely elongated penisfilum, a pair of well-developed epandrial lobes (9th tergum), and a pair of degenerated gonostyli. However, the co-evolution of their face-to-face copulation behavior and the male genitalia has rarely been studied hitherto. In this paper the mating behavior of the hangingfly Bittacus planus Cheng, 1949 was observed under laboratory conditions, and the morphology of the male and female external genitalia was investigated using light and scanning electron microscopy. The male provides an insect prey as a nuptial gift to the female in courtship and mating process, and commits a face-to-face copulation. During copulation, the male abdomen twists temporarily about 180° to accommodate their face-to-face mating position. The aedeagal complex has an extremely elongated penisfilum, corresponding to the elongated spermathecal duct of the female. The well-developed epandrial lobes serve as claspers to grasp the female subgenital plate during copulation, replacing the function of gonostyli, which are greatly reduced in Bittacidae. The modified proctiger assists the penisfilum to stretch and to enter into the female spermathecal duct. The possible reasons why this species might mate face-to-face are briefly discussed.

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.

Telmatogeton murrayi sp. n. from Iceland and T. japonicus Tokunaga from Madeira (Diptera: Chironomidae)

Male and female imagines of Telmatogeton murrayi sp. n. from Iceland are described and male and female imagines of T. japonicus Tokunaga from Madeira redescribed. Telmatogeton murrayi differs from T. japonicus by its much larger size, higher chaetotaxy, in details of the cibarial pump, and in having the posterior widening of the female spermathecal duct nearly as wide as the anterior widening. The number of setae on the pedicel indicates that the European T. japonicus not may be conspecific with the Pacific T. japonicus. The effects of environmental induced size variation on morphological differences and meristic data are discussed.

Co‐evolution of male and female reproductive traits across the Bruchidae (Coleoptera)

1. Despite the obvious importance of spermatozoa to individual reproductive success a general explanation of variation in spermatozoan form and function is still lacking. In species with internal fertilization, sperm not only have to interact with the physical and biochemical environment of the female reproductive tract, but frequently face competition from the sperm of rival males. Both sperm competition theory and adaptation to the selective environment of the female reproductive tract have been implicated in the evolution of spermatozoan morphological diversity. 2. Using the comparative method, we examine variation in sperm length in relation to (i) sperm competition intensity (as measured by relative testis size) and (ii) female reproductive characters, across 15 species of beetle belonging to the family Bruchidae. 3. Stepwise multiple regression within a phylogenetic framework revealed sperm length to be positively correlated with female spermathecal duct length and negatively related to spermathecal volume, but not testes size, indicating that the female reproductive environment rather than sperm competition per se exerts selection on sperm length in this taxonomic group. 4. A positive association between testes volume and the volume of the female spermatheca was also evident suggesting correlated evolution of these traits. 5. A number of models of sexual selection could lead to the correlated evolution of male and female reproductive characters, although the underlying mechanisms of cause and effect remain elusive. Divergence between species (and populations) in primary reproductive traits is likely to present a significant barrier to hetero-specific fertilization, and thus contribute to reproductive isolation.

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.

Taxonomic revision of Hawaiian Bembidion Latreille (Coleoptera: Carabidae: Bembidiini) with a discussion of their reductive and derivative evolutionary specializations

The Bembidion fauna (Coleoptera: Carabidae: Bembidiini) of the Hawaiian Islands is taxonomically revised, entailing the recognition of 23 native, precinctive species, and one adventively introduced Old World species, Bembidion niloticum Dejean. Two species previously placed in Gnatholymnaeum Sharp—G. blackburni Sharp, 1903, and G. spurcum (Blackburn, 1881)—are formally placed as member taxa within Bembidion Latreille, with Gnatholymnaeum recognized at subgenus rank. This taxonomic placement establishes Bembidion blackburni Csiki, 1928, as a junior secondary homonym, and Bembidion ateradustum, new name, is proposed as a replacement. Twenty-one species are recognized as member taxa of Bembidion subgenus Nesocidium Sharp, five of which are newly described: Bembidion waialeale, new species, from Kauai; Bembidion paratomarium, new species, and Bembidion gagneorum, new species, from Oahu; Bembidion kamakou, new species, from Molokai; and Bembidion haleakalae, new species, from East Maui. Bembidion molokaiense Sharp (new synonymy) is treated as a junior synonym of Bembidion ignicola Blackburn, and Metrocidium brevicolle Sharp (new synonymy) is placed as a junior synonym of Bembidion munroi (Sharp). Taxonomic treatment includes a key to species, diagnoses and descriptions of the male genitalia and female reproductive tract for all species, and complete descriptions of external characters for newly described species. Length of the male aedeagal flagellum in subgenus Nesocidium species was found to be subequal in length, to 60–75% longer than the female spermathecal duct, consistent with previous reports that list emplacement of the male spermatophore within the female spermathecal duct as a primary function of the male flagellum. Geographical distribution varies in concert with dispersal ability. All species including at least some individuals with fully developed flight wings are distributed on multiple oceanic islands. Representative taxa within putative clades of vestigially winged species occupy adjacent oceanic islands, implying overwater dispersal by wingless ancestors of present-day species followed by speciation. Ecological preference conforms to the taxon cycle at the archipelago level, with the ancestor of Hawaiian Bembidion hypothesized to have inhabited coastal habitats. Present-day ecological specialists include a deep-soil inhabitant, and numerous species found predominantly in arboreal microhabitats such as mossy vertical tree trunks and horizontal nurse logs. Geographic distributions of the species define areas of endemism appropriate for conservation that are geographically congruent with areas defined by other carabid beetle taxa in Blackburnia Sharp and Mecyclothorax Sharp, as well as by taxa in other insect groups.

The production and transfer of spermatophores in three Asian species of Luciola fireflies

During mating, many male insects transfer sperm packaged within a spermatophore that is produced by reproductive accessory glands. While spermatophores have been documented in some North American fireflies (Coleoptera: Lampyridae), little is known concerning either production or transfer of spermatophores in the aquatic Luciola fireflies widespread throughout Asia. We investigated this process in Japanese Luciola lateralis and L. cruciata by feeding males rhodamine B, a fluorescent dye known to stain spermatophore precursors. We then mated males with virgin females, and dissected pairs at various timepoints after mating. In both of these Luciola species, spermatophores were produced by three pairs of male accessory glands and were transferred to females during the second stage of copulation. Male spermatophores were highly fluorescent, and were covered by a thin outer sheath; a narrow tube leading from an internal sperm-containing sac fit precisely into the female spermathecal duct, presumably for sperm delivery. Both L. lateralis and L. cruciata females have a spherical spermatheca as well as a highly extensible gland where spermatophore breakdown commences by 24h post-mating. Similar reproductive anatomy was observed for both sexes in Luciola ficta from Taiwan. These results suggest that nuptial gifts may play an important role in many firefly-mating systems.

The evolution of sperm length in moths.

Sperm form and function remain poorly understood despite being of fundamental biological importance. An instructive approach has been to examine evolutionary associations across comparable taxa between sperm characters and other, potentially selective reproductive traits. We adopt this approach here in a comparative study examining how sperm lengths are associated with male and female reproductive characters across moths. Primary data have revealed Lepidoptera to be an ideal order for examination: there is profound variation in the dimensions (but not organization) of the reproductive traits between closely related species which all share a monophyletic ancestry, for example, eupyrene sperm length varies from 110 to 12,675 microm. Eupyrene (normal fertilizing) and apyrene (anucleate and non-fertile) sperm lengths are positively correlated across taxa and both sperm types show positive associations with mating pattern (as measured by the residual testis size). At fertilization, eupyrene sperm must migrate down the often elongated female spermathecal duct from storage to unite with the ovum. Across taxa, the elongation of this duct is associated with increased eupyrene sperm length, suggesting a positive female influence on sperm size since longer, more powerful sperm may be selected to migrate and/or compete successfully down greater ductal lengths. Apyrene sperm length is not associated with female reproductive tract dimensions. However, we found a positive relationship between the residual testis volume and spermathecal volume, suggesting coevolution between male investment in spermatogenesis and the extent of the female sperm storage capacity. Within males, there is a positive association between the two organs which form the ejaculate-containing spermatophore: the testes and the accessory gland. The 'trade-up' in investment to these components is discussed in relation to paternal investment and mating patterns.

Transfer of a male accessory gland peptide to the female during mating in Leptinotarsa decemlineata

Summary The male accessory glands of the Colorado potato beetle, Leptinotarsa decemlineata, produce an 8kDa peptide (Led-MAGP), whose primary structure and gene have been described. To investigate the possible function of this peptide in the female, we traced the passage of Led-MAGP through the male and female reproductive tracts during and after the mating process. We used immunohistochemical procedures to localize Led-MAGP employing a specific polyclonal antiserum which was raised against a recombinant Led-MAGP. Mating couples of Colorado potato beetles were interrupted after various time intervals after the initiation of mating and fixed by perfusion to immobilize the transferred male accessory gland secretions and sperm cells. Serial sections of reproductive tracts were prepared and immunolabelled. These time-lapse studies indicated that the contents of the male accessory glands are transferred during the first few minutes of mating and are deposited in the female spermathecal duct. Sperm cells are transferred later, 4–6 min after the beginning of mating. Led-MAGP is found in two forms, namely a granular, doughnut-shaped form and a homogeneously dispersed form. After deposition in the spermathecal duct, the irnmunoreactive product dissolved within 4–6 min. It is argued that the Led-MAGP crosses the duct wall and enters the hemolymph and that its function must therefore be sought outside the female reproductive tract.