Fertilization Chamber Research Articles

The anatomy and histology of the reproductive system of Aplysia oculifera (Mollusca: Heterobranchia: Aplsiida) from the Red Sea coastal waters

ABSTRACT Aplysia oculifera is an endemic sea hare that inhabits the Egyptian coast of the Red Sea. We describe the reproductive system of this species for the first time. It is composed of an ovotestis, small hermaphroditic duct, nidamental glandular complex, large hermaphroditic duct, gametolytic gland, external seminal groove and cephalic penis. The follicles within the ovotestis contain spermatogenic and oogenic cells. A pre-ampulla, ampulla, and post-ampulla constitute the different regions of the small hermaphroditic duct. The nidamental complex consists of albumen, mucus, and membrane glands all confluent with the fertilization chamber. The nidamental glands consist of glandular cells alternating with supporting cells. The glandular cells have different histochemical characters concerning the production of acid and neutral mucopolysaccharides. The large hermaphroditic duct is attached to a seminal receptacle. The duct has two components; red and white hemiducts the secretory epithelia of which are distinguished internally. An atrial gland is present near the visceral genital opening. The gametolytic gland has four types of columnar cells. A seminal groove arises from the genital opening and extends anteriorly to the apex of an ear-like flap penis. The results suggest that some differences in certain reproductive characters may be of phylogenetic importance.

The ultrastructure of sperm and female sperm storage organs in the water strider Gerris lacustris L. (Heteroptera) and a possible example of genital coevolution

The fine structural organization of the male and the female inner reproductive apparatuses of the water-strider Gerris lacustris was studied. The sperm of the species shows a long helicoidal acrosome provided with longitudinal tubules, and a short nucleus. The flagellum is characterized by crescent mitochondrial derivatives and a 9 + 9 + 2 axoneme, as occurs in all Heteroptera. The female reproductive apparatus is characterized by an extremely long spermathecal duct, filled with sperm, which plays the role of the main sperm storage organ. The duct has a thin epithelium surrounded by a complex of secretory and duct-forming cells. The spermathecal duct flows into the gynatrial sac. This region, together with the fertilization chamber, exhibits a simple epithelium with deep apical plasma membrane invaginations, and it does not show conspicuous secretions. The basal cell region shows plasma membrane infoldings forming thin cytoplasmic bands hosting mitochondria and large intercellular spaces. This organization is typical of epithelia active in fluid reabsorption. Two lateral large gynatrial glands open into the gynatrial sac. Such glands also exhibit secretory and duct forming cells. The same structure of these glands is also present along the proximal region of the fecundation canal. The duct forming cells of these regions have very wide ducts with peculiar cuticular finger-like structures at their opening into the gland duct lumen. The results of the present study suggest the occurrence of a coevolution between the sperm and the spermathecal duct lengths.

Intraspecific morphological variation of the sperm storing organ in two hermaphroditic land snail species

BackgroundPostcopulatory sexual selection is very important in species with reproductive strategies that involve multiple mating and prolonged sperm storage. The sperm storage organ has been hypothesized to evolve in response to different levels of sperm competition in several species while population density has been considered as a factor that approximates sperm competition risk and intensity in the field. Apart from population density, local microclimatic conditions may also play a role in determining sperm competition levels in natural populations of land snails by affecting their chances of encountering mates. The goal of this study was to investigate the variation of the structure of the sperm storage organ in the simultaneously hermaphroditic land snails Helix lucorum and Cepaea vindobonensis occurring sympatrically in two sites which differed in habitat humidity. The populations of both species from the two sites, also differed in density and in duration of reproductive period. Multiple samples were taken from each population in order to test for temporal variation.ResultsIn both species, the spermatheca consisted of a simple fertilization chamber and a variable number of lateral tubules. The length of the spermatheca showed no temporal or spatial differentiation nor did it show any correlation with snail size. The number of tubules in Helix lucorum ranged from five to sixteen and in Cepaea vindobonensis from one to eight and in both species a significant difference of this trait between the two study sites was detected. In Cepaea vindobonensis, the difference in tubule number led to difference of the total tubule length which reflects sperm storage capacity of the spermatheca but this was not the case with H. lucorum in which no increase in total tubule length was detected.ConclusionsIntraspecific variation in the spermatheca was observed in both snail species studied. The variation observed was independent of snail size, and reproduction status, while the two species responded differently to higher sperm competition levels.

The first ultrastructural observations of the egg-forming complex of Calicotyle affinis, an endoparasitic monocotylid monogenean which lacks a uterus.

This ultrastructural study of the female reproductive system of Calicotyle affinis, a monogenean without a uterus, demonstrates, for the first time in a monogenean, the presence of accessory cells located in the peripheral region of the ovary and a single large cell whose surface is penetrated by deep invaginations which restrict the passage of oocytes through the lumen of the distal extremity of the ovary. The cytoarchitecture of the epithelial lining of the two vaginae is a syncytium formed by an anucleate epithelial lining with sunken epithelial perykaria. The wall of the seminal receptacle is an enlarged prolongation of the vaginal epithelial lining. Fertilization occurs in the fertilization chamber and fertilized oocytes retain cortical granules within their cytoplasm, a characteristic known to occur in free-living flatworms. Our study also highlights concentrations of two distinct groups of Mehlis' gland cell ducts on either side of the proximal end of the ootype distinguished by ultrastructural characteristics of their secretory granules. The epithelial wall of the ootype is formed by a single layer of regular, columnar, glandular epithelial cells; these cells are closely adjacent, conjoined towards their apical region by septate junctions and produce rounded, electron-dense granules which are discharged into the ootype lumen via a merocrine or holocrine mechanism. Released granules concentrate around the eggshell and form an additional fibrous coat. The morphological diversity observed in the female reproductive system of the Monogenea is commented on it relation to clarifying patterns in monogenean evolution and for understanding the phylogeny of the Neodermata.

Sperm Storage Patterns in Doubly Mated Female Anastrepha suspensa (Diptera: Tephritidae)

We examined sperm storage patterns of doubly mated females in a species of tephritid fly (Anastrepha suspensa (Loew) [Diptera: Tephritidae]) with four sperm storage organs and an unusually complex reproductive system to elucidate possible reproductive arenas in which sexual selection can or has played a role in sperm competition and cryptic female choice and to predict effects on paternity outcomes. The duration of copulation with each male of doubly mated female flies was recorded and the sperm storage organs were dissected to determine the location and identity of each male’s sperm (by microsatellite polymerase chain reaction) and its relative quantity. Short copulations with the first male generally resulted in little transfer of sperm and predicted the length of time spent in second copulations, resulting in disproportionate sperm storage from second copulations. For doubly mated females, most storage organs contained sperm from second males only, although the fertilization chamber often contained sperm from both males (allowing for possible sperm competition). Long-term storage organs (spermathecae) always contained sperm from single males exclusively possibly limiting opportunities for sperm competition. Our data provide a mechanism for second male precedence without invoking sperm competition, and caution that paternity patterns must be critically interpreted with inclusion of information on sperm storage patterns.

Intra-specific morphological variation of the spermatheca in the simultaneously hermaphroditic land snail Helix aperta

In the majority of internally fertilizing animals, females are equipped with sperm storage organs where they store the sperm received during copulation. In many simultaneously hermaphroditic pulmonates, these organs consist of complex spermathecae that show inter- and intra-specific variation in their structure. This variability is theoretically predicted by postcopulatory sexual selection in the context of sperm competition and cryptic female choice. In this study, the variation in the structure of the spermatheca was investigated in the land snail Helix aperta from four natural populations near Bejaia in northern Algeria. The populations were different in local snail density, probably also reflecting the intensity of sperm competition. We tested whether the spermatheca showed differences that are predicted by sperm competition theory. In addition, we tested whether the spermathecal structure depends on the shell size and/or is correlated with other reproductive organs that are thought to be affected by sexual selection. We found that the fertilization pouch of H. aperta consists of a simple fertilization chamber and 3–9 spermathecal tubules. The four populations did not differ significantly in the mean number of these tubules. However, significant differences were found in the length of the main tubule, the length of the fertilization chamber, and the average length of lateral tubules. In addition, strong associations were detected between the lengths of these structures and the local snail density, while no effect of shell size or reproductive organs was found. Our results indicate that the intensity of sperm competition may not affect the total number of spermathecal tubules, but may increase their lengths. This increase in spermathecal length may reflect an improved sperm storage capacity that is probably beneficial in situations of high sperm competitions intensity.

The morphology of the male and female reproductive system in two species of spider crabs (Decapoda: Brachyura: Majoidea) and the issue of the velum in majoid reproduction

The reproductive system of spider crabs (Majoidea) has raised considerable interest due to the complexity of female sperm storage organs. In several majoid species, the seminal receptacle has been described as being divided into a dorsal storage chamber and a ventral fertilization chamber separated by a muscular velum. The velum is supposed to control the amount of sperm used for fertilization and to play an important role in sperm competition. Here, we present a study on the reproductive systems of the two majoid species, Mithraculus sculptus (Lamarck, 1818) and Stenorhynchus seticornis (Herbst, 1788) using various morphological techniques such as μCT scans and 3D-reconstructions, complemented by paraffin histology. The male gonopods of the herein investigated species are similar in their general morphology and in the presence and distribution of setae. The tubular first gonopod holding the ejaculatory canal is much longer than the short and stout second gonopod, which is supposed to function as a piston in the transport of sperm into the female ducts. The female reproductive system of M. sculptus and S. seticornis conforms to that of other Eubrachyura in possessing paired ovaries, oviducts, seminal receptacles, vaginae, and vulvae. Based on our 3D-reconstructions we demonstrate that there is no division of the seminal receptacle into two chambers separated by a velum. In contrast to this, we observed a spatially restricted invagination of the seminal receptacle. A comparison of our data with those of previous studies, allows for the conclusion that the invagination of the seminal receptacle may have been misinterpreted and mistaken for a velum by other authors. Thus, the division of the seminal receptacle into two chambers separated by a velum is a character which needs to be re-evaluated.

Measuring scallop fertilization success in the field: chamber design and tests

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 551:141-154 (2016) - DOI: https://doi.org/10.3354/meps11684 Measuring scallop fertilization success in the field: chamber design and tests Skylar R. Bayer*, Richard A. Wahle, Peter A. Jumars, Damian C. Brady Darling Marine Center, University of Maine, 193 Clark’s Cove Road, Walpole, ME 04573, USA *Corresponding author: skylar.bayer@maine.edu ABSTRACT: We developed and tested a method to field test fertilization success, measured as the proportion of eggs fertilized, in the giant sea scallop Placopecten magellanicus, a commercially valuable and sedentary broadcast spawner in the northwest Atlantic. A laboratory sperm dilution series determined maximum fertilization success expected in the field and assessed gamete longevity. We also developed and flume-tested a fertilization chamber to assess ambient water-column sperm loads near field populations. We then conducted a series of dockside field trials using these chambers over the course of the late summer spawning season in coastal Maine, USA. Chambers were deployed among manipulated populations of scallops to assess effects of local spawner abundance and location on time-integrate fertilization success. In dilution-series experiments, maximum fertilization success occurred at sperm concentrations >107 sperm ml-1. Egg longevity fell to zero between 8 and 24 h at ambient temperatures of 12°C, and sperm half-life shortened from 2 h to 9 min with a 10-fold dilution from a sperm concentration of 107 cells ml-1. Flume trials demonstrated chamber artifacts: fertilization was lower inside the chamber and the effect was greater at higher flow rates, but chamber orientation to flow had no effect. Increasing the numbers of eggs tended to reduce fertilization efficiency. In dockside tests, a 30-fold difference in spawner numbers had a significant effect on fertilization success. Notwithstanding acknowledged chamber artifacts due to flow impedance, this study establishes the feasibility of time-integrated fertilization experiments with scallops and sets the stage for further investigations of fertilization dynamics in natural scallop populations. KEY WORDS: Giant sea scallop · Placopecten magellanicus · Fertilization success · Fertilization ecology · Population density effect · Allee effects · Fisheries · Depensation Full text in pdf format PreviousNextCite this article as: Bayer SR, Wahle RA, Jumars PA, Brady DC (2016) Measuring scallop fertilization success in the field: chamber design and tests. Mar Ecol Prog Ser 551:141-154. https://doi.org/10.3354/meps11684 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 551. Online publication date: June 09, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Polyandry in the medfly - shifts in paternity mediated by sperm stratification and mixing.

BackgroundIn the Mediterranean fruit fly (medfly), Ceratitis capitata, a highly invasive agricultural pest species, polyandry, associated with sperm precedence, is a recurrent behaviour in the wild. The absence of tools for the unambiguous discrimination between competing sperm from different males in the complex female reproductive tract has strongly limited the understanding of mechanisms controlling sperm dynamics and use.ResultsHere we use transgenic medfly lines expressing green or red fluorescent proteins in the spermatozoa, which can be easily observed and unambiguously differentiated within the female fertilization chamber. In twice-mated females, one day after the second mating, sperm from the first male appeared to be homogenously distributed all over the distal portion of each alveolus within the fertilization chamber, whereas sperm from the second male were clearly concentrated in the central portion of each alveolus. This distinct stratified sperm distribution was not maintained over time, as green and red sperm appeared homogeneously mixed seven days after the second mating. This dynamic sperm storage pattern is mirrored by the paternal contribution in the progeny of twice-mated females.ConclusionsPolyandrous medfly females, unlike Drosophila, conserve sperm from two different mates to fertilize their eggs. From an evolutionary point of view, the storage of sperm in a stratified pattern by medfly females may initially favour the fresher ejaculate from the second male. However, as the second male's sperm gradually becomes depleted, the sperm from the first male becomes increasingly available for fertilization. The accumulation of sperm from different males will increase the overall genetic variability of the offspring and will ultimately affect the effective population size. From an applicative point of view, the dynamics of sperm storage and their temporal use by a polyandrous female may have an impact on the Sterile Insect Technique (SIT). Indeed, even if the female's last mate is sterile, an increasing proportion of sperm from a previous mating with a fertile male may contribute to sire viable progeny.

3D- microanatomy of the semiterrestrial slug Gascoignella aprica Jensen, 1985—a basal plakobranchacean sacoglossan (Gastropoda, Panpulmonata)

The monophyly of the panpulmonate, usually marine benthic Sacoglossa—and its basal division into shelled Oxynoacea and shell-less Plakobranchacea—is undisputed, but family relationships are in doubt. Of particular interest is the potentially basal plakobranchacean family Platyhedylidae, comprising morphologically aberrant members lacking head tentacles or body appendages. Herein we re-describe the type species of the genus Gascoignella, G. aprica Jensen, 1985, from Hong Kong. Morphological data was generated by three-dimensional reconstruction from serial semi-thin sections using Amira software. Our microanatomical results largely confirm the original description. The anterior digestive system is sacoglossan-like but modified, e.g. the ascus is not demarcated externally and pharyngeal pouches are lacking. The digestive gland is bipartite, with two rami separated by a longitudinal, muscular, median septum, but fused in the rear end. The postpharyngeally situated nerve ring contains fused cerebropleural ganglia; the short visceral loop has three ganglia. Two major cerebral nerves were identified as rhinophoral and labiotentacular nerves, innervating sensory areas on the head velum. Gascoignella aprica is a hermaphrodite with a truly androdiaulic genital system of which some originally ambiguous characters are clarified. Bursa and prostate insert into a fertilization chamber proximal to a sac-like albumen gland and a tubular mucus gland. The cephalic copulatory apparatus contains a penis armed with a short and straight stylet and an accessory gland of unclear function; the presumed mode of sperm transfer is discussed. A well-developed heart and a large H-shaped kidney are present; the nephroduct opens into the intestine. Epidermal glands and body tissues are described for the first time. The presence of a unique longitudinal, median septum is considered diagnostic for Platyhedylidae, multiple further apomorphies are given. Morphological evidence supports the molecular phylogenetic hypothesis that the Platyhedylidae could be a basal non-shelled sacoglossan lineage.

Developmental synchronization of male and female gametophytes in Ginkgo biloba and its neck mother cell division prior to fertilization

This study investigated male and female gametophytes in Ginkgo biloba, while a droplet of fluid was present in the fertilization chamber and found that the central cell, the generative cell and the neck mother cell divided simultaneously prior to fertilization. In male gametophytes, the generative cell divided to yield two sperm cells. Concomitantly, the two neck mother cells of the archegonium increased in size then divided asymmetrically resulting in two big cover cells and two small base cells. Each cell had a fixed end in direct contact with an adjacent jacket cell and a free end overlapping its counterpart. This unique arrangement could allow for their free ends to swing into the fertilization chamber as a result of the force from the interior of the archegonium where a polar periclinal division had occurred to produce a canal cell and an egg. The subsequent withdrawal of the content of the archegonium may facilitate the entry of sperm into the archegonium. The neck apparatus closed after the fertilization occurred. The concurrence oftheabove divisions and the delicate structure of neck apparatus suggest that the gametophytes undergo a synchronization process to become receptive at the time of fertilization. However, the formation of neck cells and the opening time of neck apparatus of the archegonia within the same ovule were slightly different, which could lead to the formation of zygotes at a temporally distinct interval. The earlier formed zygote may progress as the only mature embryo in the ovule.

New Benedenia Species (Monogenea: Capsalidae) from Diagramma labiosum (Perciformes: Haemulidae) On the Great Barrier Reef, Australia, With Oncomiracidial Descriptions and A Report of Egg Attachment to the Host

The slate sweetlips, Diagramma labiosum Macleay, 1883 (Perciformes: Haemulidae), off Heron Island, Great Barrier Reef, Queensland, Australia, hosts 2 new species of Benedenia Diesing, 1858 (Monogenea: Monopisthocotylea: Capsalidae). Benedenia beverleyburtonae n. sp. infects proximal regions of the primary gill lamellae and gill arches. The adult is characterized by a dorsal vaginal pore anterior to the common genital pore and a voluminous, highly coiled vas deferens. This species also has fine muscle fibrils concentrically arranged in the haptor. Its ciliated oncomiracidium differs little from larvae of other Benedenia species, with the exception of at least 4 gland cells containing a granular secretion on each side of the body at the level of the excretory bladders, with fine ducts opening anterior to the eyes. Benedenia disciliata n. sp. infects gill arches and gill rakers, and the adult is characterized by its small total length, anterior hamuli with a small proximal notch, posterior hamuli with a broad, triangular shape proximally, a conspicuous internal fertilization chamber, and asymmetrical eggs. None of the 5 specimens collected had testes, but their definite absence is undetermined. Their absence and the fact that the vas deferens was discernable only distally in the specimens of B. disciliata examined may represent atrophying of the male organs. Benedenia disciliata is unique among Benedenia species because eggs are attached to the host's gill arches by tight wrapping of the appendages around spines on the gill rakers and the larva is not ciliated. Among Capsalidae species, these features are shared only with species of Dioncus Goto, 1899. Recent molecular evidence has indicated Benedenia is polyphyletic, but with no clear morphological characters available to divide the genus, the 2 new species fit the current concept for the genus more closely than other capsalid genera. Proposal and description of these taxa and accounts of their oncomiracidia and other aspects of their biology indicate potentially useful characters for division of the genus in the future.

Spermathecae of the mangrove crab Ucides cordatus: a histological and histochemical view

Ucides cordatus is the most commercially important mangrove crab in Brazil. In spite of its economic importance, there are few studies of its reproduction, in particular the female reproductive system. The present study describes the histology and histochemistry of the spermathecae of U. cordatus. Adult females were caught monthly from July 2004 through June 2005, at Iguape, State of São Paulo. The crabs were anaesthetized, and their spermathecae removed and fixed in Davidson's fluid, following the histological routine for paraffin. The slides were stained with HE, xylidine Ponceau, PAS, alcian blue (pH 1.0 and 2.5), Sudan black B and picrosirius-haematoxylin. Histologically, the spermathecae possesses a capsule of conjunctive tissue, rich in collagen fibres, which surrounds the secretory columnar epithelium. In the lumen, individual sperm packets are not observed; the spermatophores are intermixed with the seminal fluid and secretions of the spermathecae itself. A large proportion of the free spermatozoids and spermatophores are arranged in homogeneous masses in the proximal part of the spermathecae. The secretion produced by the columnar epithelium appears to promote the movement of the gametes to the fertilization chamber, in a ventral position, allowing fertilization of the oocytes. Histochemically, the secretion produced by the columnar epithelium was strongly positive for neutral polysaccharides, positive for acid polysaccharides, and weakly positive for proteins and lipids. This secretion forms a glycoprotein matrix which is associated with maintenance of the spermatophores, which can remain stored for long periods.

Variation in spermathecal morphology is independent of sperm competition intensity in populations of the simultaneously hermaphroditic land snail Cornu aspersum

The complexity of the sperm-storing organ (spermatheca) has been hypothesized to reflect sperm competition intensity in several gastropod species. Furthermore, considerable variation in spermathecal morphology has been detected among populations of the same species. The morphological variation of the fertilization pouch was studied in five populations of the simultaneously hermaphroditic land snail Cornu aspersum (formerly, Helix aspersa). The populations studied differed in snail density and habitat humidity regimes, thus in sperm competition intensity. The study was conducted on wild adult snails and their progeny, which was reared in the laboratory for two successive generations. Finally, the morphology of the spermatheca was correlated to behavioral mating traits of the snails. The fertilization pouch consisted of a simple fertilization chamber and 4–19 blind tubules. The five studied populations did not differ in either mean number of spermathecal tubules, length of the fertilization chamber, length of the main tubule, or cumulative length of all tubules, while they differed in copulation frequency and mating propensity. No correlation was found between snail size and number of tubules, or length of any spermathecal structure measured. Additionally, no correlation was found between any behavioral trait and the morphological characteristics of the spermatheca. Strong correlations were found only among measurements of some of the spermathecal structures. Our results suggest that the complexity of the spermatheca is not related to sperm competition intensity and its structure is thus genetically determined.

Ultrastructure of the ovary, ovicapt and oviduct of the spathebothriidean tapeworm Didymobothrium rudolphii (Monticelli, 1890)

AbstractThe ultrastructural details are presented of the ovary, ovicapt and oviduct of the spathebothriidean tapeworm Didymobothrium rudolphii (Monticelli, 1890) from the intestine of the sand sole Solea lascaris. Oogonia, maturing oocytes and mature oocytes are surrounded by a syncytial interstitial cytoplasm, one of the distinctive traits of which is the presence of numerous myelin-like bodies. Oocyte inclusions comprise cortical granules and a small number of lipid droplets. The thickened, nucleated epithelium of the ovicapt lacks any apical structure and is a prolongation of the narrow ovarian epithelium. The muscular sphincter of the ovicapt is formed by a band of longitudinal muscles and bands of radial muscles at right angles to the longitudinal layer, and numerous myocytes surround the ovicapt wall. The oviduct of D. rudolphii is subdivided into three regions: (1) the proximal oviduct; (2) the fertilization chamber — the region distal to the point of entry of the duct from the seminal receptacle; and (3) the ovovitelline duct — the region distal to the point of entry of the duct from the vitelline reservoir. A comparative analysis is made between the structures of the ovary, ovicapt and oviduct of D. rudolphii and those of two other spathebothriideans, Cyathocephalus truncatus and Diplocotyle olrikii, with a discussion of ultrastructural traits that might be used as taxonomic criteria within the order Spathebothriidea.

Function of multiple sperm storage organs in female Mediterranean fruit flies ( Ceratitis capitata, Diptera: Tephritidae)

Sperm storage organs allow females to temporally separate insemination from fertilization, manipulate ejaculates and control fertilization. In the reproductive tract of female fruit flies (Diptera: Tephritidae), sperm are found in two different organs—a pair or triplet of spermathecae, and a “fertilization chamber”. In order to understand the specific function of each of these organs, we tested the following hypotheses: (1) Sperm are distributed equally amongst the various sperm storage organs; (2) Both organ types maintain sperm viability; and (3) Sperm used in fertilization come from the fertilization chamber. We counted sperm in spermathecae and fertilization chamber of Mediterranean fruit flies ( Ceratitis capitata) every 3 days for 18 days following insemination, and used a live/dead staining technique to determine the viability of sperm in these organs. Finally, by extirpating spermathecae from inseminated females and allowing them to oviposit, we were able to identify the fertilization chamber as the source of fertilizing sperm. Numbers of sperm in the spermathecae declined from an average of 3575 on the day of copulation to 649, 18 days later. Conversely, the fertilization chamber maintained a fairly constant level of sperms, ranging between an average of 207 cells on day 3 to 115 sperms on day 18. Throughout the period we monitored, we found high levels of sperm viability in both organs (>80%). Sperm viability was similarly high in the fertilization chambers of females without spermathecae. However, fertility of eggs laid by these females declined rapidly, as did the number of sperm in the fertilization chamber. We conclude that both the spermathecae and the fertilization chamber are active sperm storage organs, with separate functions: the spermathecae for long-term storage and the fertilization chamber, periodically filled by the spermathecae, a staging point for fertilizing sperm. We suggest that the use of both organs by females results in sperm economy, which adaptively prolongs the intervals between copulations.

Embryogenesis and the first-stage larva of Thelazia lacrymalis.

The female reproductive system of Thelazia lacrymalis (Nematoda: Thelaziidae) was investigated by light and scanning electron microscopy (SEM) with regard to the developmental stages and the stage deposited by the gravid nematode. Female T. lacrymalis have a didelphic and opisthodelphic type of reproductive system with paired ovaries, oviducts and uteri and a single vagina and vulva. Round and spindle-shaped primary oocytes are documented within the ovaries and oviducts, respectively. The distal part of each uterus provides a fertilization chamber filled with spermatozoa, followed by a sphincter-like part. Further anterior, the uteri broaden gradually containing dividing zygotes, small and large morulae, tadpole-stage embryos and horseshoe-shaped embryos which increase in length and become slimmer forming pretzel-stage embryos and larvae rolled up. The larvae stretch gradually and finally lie straight but still covered with their egg membrane in the vagina. The egg membrane encloses the whole larva and is enlarged at the pointed tail of the larva forming a bulb. At the SEM level, the first-stage larva is shown to have a terminal mouth and three hooks directed posteriorly and a striated cuticle. As morphologically identical larvae were also found in lavages of the conjunctival sac of horses infected with T. lacrymalis, this nematode species can be described as ovoviviparous.

Functional anatomy of the sperm storage organs in Pulmonata: the simple spermatheca of Bradybaena fruticum (Gastropoda, Stylommatophora)

Data on sperm storage and paternity analyses in the pulmonate land snail Arianta arbustorum suggest that the complex, multitubular sperm storage organ, the spermatheca, may influence paternity after multiple matings. Ultrastructural investigations show that the spermatheca is provided with the morphological correlates to exert cryptic female choice. However, in order to understand the function of a multitubular spermatheca it is necessary to understand how a single spermathecal tubule functions. In order to explore the potential to serve as a model for such a simple system in future experiments, the fine structure of the unitubular spermatheca and its interaction with spermatozoa were investigated in Bradybaena fruticum, another member of the Helicoidea. The spermatheca of B. fruticum is only about one-half as long as the fertilization chamber. Its epithelium is densely ciliated throughout its length. Vacuole, Golgi complex, rough endoplasmic reticulum, various vesicles, wide intercellular spaces, and an extensive basal labyrinth indicate strong secretory activity, providing the environment for sperm storage and capacitation. Prior to transfer, sperm are characterized by a perinuclear sheath and an acrosome tilted at about 50°. In the spermatheca, the perinuclear sheath is dissolved and, probably as a consequence, the acrosome folds up in line with the nuclear longitudinal axis. The spermatheca is surrounded by a network of differently oriented smooth muscle cells, which are extensively connected with each other through dense plaques. The fine structure of the muscle cells suggests that they are neither very strong nor enduring. The main function of the spermathecal musculature is certainly expulsion of sperm prior to fertilization. The musculature around the spermathecal tubule of B. fruticum appears to be a highly integrated system not allowing for much functional flexibility compared to A. arbustorum, where the muscle cells are more individualized, permitting finely tuned operations. This restricted flexibility needs to be taken into consideration in future experiments using B. fruticum as a model for the simple, unitubular sperm storage system.

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.

Ultrastructural study of pathological effects on the female reproductive system ofSaduria entomonL. (Crustaeea, Isopoda) from the Baltic infected withCryptococcus laurentii(Kufferath) Skinner

Summary A variety of pathological lesions were observed by electron microscopy in the female reproductive tract of Saduria entomon naturally infected with Cryptococcus laurentii. Pathological changes were clearly visible in the epithelial and muscle cells of the distal part of the ovaries and oviducts and in the cells making up the fertilization chamber. The lesions were characterized by the occurrence of lysosomes, a decrease in cytoplasmic density, damaged mitochondria, and disorganization of myofilaments. In the epithelial cells of the ovaries, the chromatin was concentrated in large granules mainly on the peripheries of their nuclei. In some epithelial cells of the distal parts of the ovaries, the plasma and nuclear membranes were disrupted. Some of the damaged cells had lost contact with the basal lamina and were observed in the lumen as cell debris. The most radical changes, however, were observed in the oviducts in which the epithelial and muscle cells suffered complete destruction, and what was le...