Structure of the ovipositor and ovary and the features of reproduction in Amur bitterling <Emphasis Type="Italic">Rhodeus sericeus</Emphasis> (Cyprinidae: Acheilognatinae)

Biological characteristics of sexually mature individuals of Amur bitterling Rhodeus sericeus from the Amur River basin are described. Sexual maturity is reached in the first year of life in males and in the second year in females. The development of ovipositors is observed during sexual maturation of the females and their preparation to spawning. The base of the ovipositor is formed by the conical organ. Based on the structure of the conical organ, including a special distribution of collagenous and muscular fibrils, well developed blood system, and numerous mucous cells in the internal epithelial layer, this organ is used for temporal storage of oocytes during the spawning period and for their movement along the ovipositor. Owing to a well developed net of blood vessels, presence of muscular wall, and numerous collagenous fibrils in the connective tissue, a stable position of the ovipositor is reached during the spawning. Based on secretion of numerous mucous cells of the external epithelial layer of the ovipositor, this organ is inserted into the excretory siphon of the mollusk during egg deposition. The spawning in Amur bitterling is in batches, and it is multiple. The oocytes of three generations can be seen in the ovary. The oocyte possesses a thin zona radiata. Based on the presence of a dense gelatinous layer in the basal part of the chorion, the egg is attached to the internal hemibranches of bivalves. The observations of free embryos of Amur bitterling in the left internal hemibranches of bivalves Sinanodonta likharevi, Nodularia amurensis, N. schrencki, and N. middendorffi show that the symbiotic relationships can be characterized as obligate.     

Features of reproductive biology in females of bitterlings (Cyprinidae: Acheilognathinae) from the Amur River basin

Data on morphological and functional characteristics of the ovipositor, conical organ, and ovaries in four species of bitterlings (Russian bitterling Acanthorodeus asmussii, Khanka spiny bitterling A. chankaensis, bitterling Rhodeus sericeus, and Amur bitterling R. amurensis) from the Amur River basin are obtained and reviewed for the first time. In all studied fish species, several generations of sex cells develop at the same time, which leads to releasing of oocytes in batches. The specificity of Amur bitterling, bitterling, and Russian bitterling to selection of mollusks for egg deposition is determined.     

The reproductive ecology of two subspecies of the bitterling Rhodeus atremius (Cyprinidae, Acheilognathinae)

The reproductive ecology of two endangered subspecies of the bitterling Rhodeus atremius was investigated in two rivers in Okayama and Fukuoka Prefectures, Japan. Several other bitterling species, R. ocellatus, Tanakia limbata, T. lanceolata, Acheilognathus tabira and A. rhombeus, are also found in these rivers. Spawning of both R. atremius subspecies was recorded between late March and August 2007, peaking between April and July. Females of R. atremius began to mature at small body size (minimum 25 mm). They had small clutch sizes (maximum 16 eggs) and developed a short ovipositor (mean 13.6 mm), which was used to deposit a bulb-shaped egg of comparatively large size (3.2 mm³, major and minor axes 2.8 and 1.5 mm). Clutch size, ovipositor length and egg size appear to be a function of female body size. Both the body size and ovipositor length of R. atremius with ripe ova and the size and shape of the eggs varied seasonally. Rhodeus a. suigensis achieved maturity at a smaller body size, had a longer ovipositor and produced smaller eggs, with the minor axis being wider relative to the major axis than those of R. a. atremius. Rhodeus atremius may be adapted for depositing small numbers of eggs in a much shallower position inside the gills of smaller host mussels than other bitterling species.     

Reproduction mode of European Bitterling (Rhodeus amarus,Bloch, 1782) determined through rapid oocyte counts and size determination using digital imaging

This study focuses on assessing the reproduction mode of an important model species for evolutionary and behavioural ecology by using digital image analysis: the European bitterling Rhodeus amarus (Bloch, 1782). Specifications of mode of reproduction were determined using oocyte size distribution, seasonal dynamics in mean oocyte diameter and total number of oocytes in ovary samples gained from April to July 2007. The rapid oocyte count was enabled by using lucia image analysis software, which also provided measurement and colour estimations of oocytes. Bitterling ovaries showed features typical for indeterminate spawners, i.e. a continuous distribution of oocyte size over the reproductive season and recruitment of new pre‐vitelogenic oocytes in the second half of the reproductive season. These results are consistent with the view that the European bitterling is a batch spawning fish with indeterminate fecundity.     

Ultrastructural Morphology of the Male and Female Genital Tracts of <Emphasis Type="Italic">Psoroptes</Emphasis> spp. (Acari: Astigmata: Psoroptidae)

The structure of the male and female genital systems of the astigmatid mite Psoroptes ovis (Hering) is described. The male genital system is composed of a paired testis, fused at its proximal part, two vasa deferentia, an ejaculatory duct, into which a single accessory gland opens, and a copulatory organ. The testis is characterized by a peripheric syncytial cell surrounding spermatogonia, spermatocytes, spermatids and spermatozoa which are distributed regularly in the gonad according to the sequence of spermatogenesis. The female genital system consists of a copulatory pore (the bursa copulatrix), a seminal receptacle, paired ovaries and oviducts, a glandular uterus and an ovipositor which leads to the oviporus. Ovaries are composed of somatic cells, germ cells and a central cell, with a multilobular nucleus, connected to oocytes by a stalk. Similarities with other astigmatic mites belonging to Psoroptidia and Acaridia are also discussed.     

Fine Structure of the Female Intoshia variabili(Alexandrov & Sljusarev) (Mesozoa: Orthonectida)

The morphology and fine structure of female Intoshia variabili, new combination for Rhopalura variabiliAlexandrov & Sljusarev, 1992, were studied with transmission electron microscopy. The body surface is covered with a 3-layered cuticula, under which is a layer of ciliated + non-ciliated cells arranged in alternating rings around the body. Ciliated cells have lateral extensions that intercalate with the non-ciliated cells. The kinetosome of each cilium has two longitudinally oriented cross-striated rootlets. The outer surface of the ciliated cells is covered with small tubercles, and the cytoplasm of these cells contains granules, vacuoles, mitochondria, fibrillar structures and lamellary bodies. A band of dense fibrils passes through the upper part of each ring of cells, going from one cell junction to another, encircling the entire body. Between the layer of ciliated + non–ciliated cells and the oocytes, elongated contractile cells from 4–5 longitudinal columns and 1 ring, the latter at the level of ciliated rings 7–9. The contractile cells contain thick and thin longitudinally oriented fibrils. The oocytes contain a large nucleus, numerous mitochondria, electron–dense granules and 1–2 spherical structures. An anteriorly situated, ciliated goblet–like receptor, not described for any other orthonectids, consists of three closely apposed cells, the upper part of which contains densely packed cilia. The genital pore opens through a non–ciliated cell and is surrounded by several cells with granules.     

Seasonal change in the spatial utilization of host mussels in relation to ovipositor length by female rosy bitterling Rhodeus ocellatus kurumeus

The seasonal changes in ovipositor length and utilization patterns of mussels for oviposition in the rosy bitterling Rhodeus ocellatus kurumeus (Cyprinidae) were investigated in a field experiment and field surveys during the breeding period (April to August). The mean length of ovipositors at oviposition was short at the start (early April) and end (July) of the breeding period. Females with long ovipositor at oviposition were collected between mid‐April and June. Mark‐and‐recapture data showed that ovipositor length at oviposition changed rhythmically throughout the breeding period, shortening and lengthening as the female entered the spawning and resting phase. The density of rosy bitterling embryos in mussels increased between April and June, peaking in May, but decreasing in July. The position of eggs on mussel gills varied from close to the exhalant siphon to deeper inside the gill during April, and periodically thereafter. There was a positive correlation between ovipositor length at oviposition and the distance from exhalant siphon of mussels to eggs deposited by females, suggesting that ovipositor length at oviposition determined the position of eggs deposited on a mussel gill. Because dissolved oxygen in mussel gills decreased with the density of bitterling embryos, suitable positions for embryo survival in gills changed with embryo density. By changing ovipositor length at oviposition, females might be able to spawn their eggs in a position that maximizes embryo survival. Thus, plasticity in ovipositor length at oviposition may play an important role as an adaptation of rosy bitterling in utilizing mussels when their quality as a spawning substratum fluctuates seasonally.     

Ovipositor ultrastructure of the striped bitterling Acheilognathus yamatsutae (Teleostei: Acheilognathinae) during spawning season

The ovipositor of striped bitterling Acheilognathus yamatsutae was subjected to ultrastructure and histochemical analysis during spawning season using light and electron microscopy. Although the ovipositor of A. yamatsutae is a long cylindrical tube with smooth external surface, it was possible to confirm the presence of well-developed fingerprint structure using scanning electron microscopy. Internal aspect analysis of ovipositor revealed formation of 5–8 longitudinal folds. Cross section analysis revealed that the ovipositor is composed of an outer epithelial layer, a mid connective tissue layer, and an inner epithelial layer. The outer epithelial layer contains 7–9 cell layers composed mainly of epithelial and mucous cells. Result of AB–PAS (pH 2.5) and AF–AB reaction showed that mucous cells contained mainly acidic carboxylated mucosubstances. The connective tissue layer was loose and made mainly of collagen fibers and some muscle fibers, along with blood vessels and a small number of chromatophores. The inner epithelial layer, which is a single layer, is composed of columnar epithelia. Observation under transmission electron microscope enabled distinction of the outer epithelial layer into superficial, intermediate and basal layers. Although the types of cells in the superficial tissue layer were diverse, they all shared the development of glycocalyx covered microridges. The majority of epithelial cells in the intermediate layer were cuboidal shaped, while those in the basal layer were columnar. Two types (A and B) of secretory cells were observed in the outer epithelial layer. The connective tissue layer had two types of chromatophores including xantophore and melanophore, in addition to a well-developed nerve fiber bundles. Columnar epithelial cells, mitochondria-rich cells and rodlet cells were observed in the inner epithelial layer. Microvilli were well developed on the free surface of columnar epithelial cells.     

Fine structure of the genital system in the bee parasite,Varroa jacobsoni (Gamasida: Dermanyssina) with remarks on spermiogenesis,spermatozoa and capacitation

The female genital tract ofVarroa jacobsoni is composed of a sperm-access system comprising paired solenostomes located between coxa III and IV, paired tubules, paired rami, an unpaired sperm duct, and an unpaired spermatheca. Another part of the female genital system is confined to egg development and oviposition. It is composed of an ovary (s.str.), in which oocytes mature, and a lyrate organ functioning as a nutrimentary structure. Both compartments, regarded as parts of the gonad, are connected by a region named the camera spermatis. This part is also in continuity with the oviduct I, which is provided with a muscular layer and numerous nerve endings. The following cuticle-lined oviduct II leads to the genital orifice through which the eggs are deposited. The fine structure of all these parts is described. Attention is drawn especially to the peculiar spermatheca which contains the inner cells which are thought to connect by way of free cells with a specialized region of the camera spermatis, thus establishing a cellular bridge through which penetration of capacitated spermatozoa into the ovary s.str. may occur. Lyrate organ and oocytes are connected via intercellular bridges/nutritive cords and are thus comparable to the telotrophic ovarioles of certain insects.The male genital system, composed of unpaired testis, paired vasa deferentia, unpaired accessory gland and ductus ejaculatorius, is described ultrastructurally. Spermiogenesis occurs in cysts and spermatozoa belong to the ribbon type. The vasa deferentia are provided with a muscular layer. For the first time receptors are detected in the proximal part or the ductus ejaculatorius. The accessory gland produces a proteinaceous secretion.Spermatozoa were observed in the female rami and spermatheca. Only in the latter were elongated, capacitated spermatozoa seen.     

The Nutrimentary Egg Development of the Mite,Varroa jacobsoni (Acari,Arachnida), an Ectoparasite of Honey Bees

The fine structure of the female gonad of Varroa jacobsoni is described. There are two components: the ovary proper and the so-called lyrate organ. The ovary is the place where oocytes mature, embedded in a supporting tissue composed of two cell types: somacells 1 and somacells 2. The lyrate organ has a nutrimentary function and is comprised of two components: supporting cells and nutritive tissue. The supporting cells are similar to the somacells 2 in that they contain abundant microtubules. The nutritive tissue is an extensive syncytium. It is connected with the oocytes via intercellular bridges, the nutritive cords. Oocytes and nutritive tissue are thought to have derived from common stem cells. From fine structural evidence it is concluded that ribosomes are one of the most important components to be transported via the nutritive cords into the oocytes. However, an increase in number of mitochondria in the middle-stage oocytes may also be a consequence of transport of these organelles from the nutritive tissue into the oocytes. Further characteristics make plausible that the interdependences of oocytes and nutritive tissue are comparable to those found in meroistic ovarioles of insects. The somatic components do not seem to be as important as the follicle cells of insects, however. It is assumed that the evolution of a nutrimentary oogenesis speeds up embryogenesis. Thus, the differentiation of the female gonad of Varroa jacobsoni may have facilitated the species' adaptation to a development completed in a short and limited time within the shelter of the covered brood cell of the bee.     

Adaptations for matrotrophy in the female reproductive system in the pseudoscorpion Chelifer cancroides (Chelicerata: Pseudoscorpiones,Cheliferidae)

Pseudoscorpiones (pseudoscorpions, false scorpions) is an order of small terrestrial chelicerates. While most chelicerates are lecithotrophic, that is, embryos develop due to nutrients (mostly yolk) deposited in the oocyte cytoplasm, pseudoscorpions are matrotrophic, that is, embryos are nourished by the female. Pseudoscorpion oocytes contain only a small amount of yolk. The embryos develop within a brood sac carried on the abdominal site of the female and absorb nutrients by a pumping organ. It is believed that in pseudoscorpions nutrients for developing embryos are produced in the ovary during a postovulatory (secretory) phase of the ovarian cycle. The goal of our study was to analyze the structure of the female reproductive system during the secretory phase in the pseudoscorpion Chelifer cancroides, a representative of the family Cheliferidae, considered to be one of the most advanced pseudoscorpion taxa. We use diverse microscopic techniques to document that the nutritive fluid is produced not only in the ovaries but also by the epithelial cells in the oviducts. The secretory active epithelial cells are hypertrophic and polyploid and release their content by fragmentation of apical parts. Our observations also indicate that fertilization occurs in the oviducts. Moreover, in contrast to previous findings, we show that secretion of the nutritive material starts when the fertilized oocytes reach the brood sac and thus precedes formation of the pumping organ. Summing up, we show that C. cancroides exhibits traits of advanced adaptations for matrotrophy due to coordinated secretion of the nutritive fluid by the ovarian and oviductal epithelial cells, which substantially increases the efficiency of nutritive fluid formation. Since the secretion of nutrients starts before formation of the pumping organ, we suggest that the embryos are able to absorb the nutritive fluid also in the early embryonic stages.     

Sensilla on antennae,ovipositor and tarsi of the larval parasitoids,Cotesia sesamiae (Cameron 1906) and Cotesia flavipes Cameron 1891 (Hymenoptera: Braconidae): a comparative scanning electron microscopy study

Two braconid parasitoids of cereal stemborers in eastern Africa, Cotesia sesamiae and Cotesia flavipes, have been shown to display a similar hierarchy of behavioural events during host recognition and acceptance. In order to understand the mechanisms underlying host recognition and acceptance, the morphology of antennal sensilla on the last antennomeres, on the ovipositor, and on the fifth tarsomere and pretarsus of the prothoracic legs tarsi were studied using scanning electron microscopy followed by selective silver nitrate staining. It appeared that female C. sesamiae and C. flavipes shared the same types and distribution of sensory receptors, which enable them to detect volatiles and contact chemical stimuli from their hosts. In both parasitoids, four types of sensilla were identified on the three terminal antennomeres: (i) non-porous sensilla trichodea likely to be involved in mechanoreception, (ii) uniporous sensilla chaetica with porous tips that have gustatory functions, (iii) multiporous sensilla placodea, which are likely to have olfactory function, and (iv) sensilla coeloconica known to have thermo-hygroreceptive function. The tarsi of both parasitoids possessed a few uniporous sensilla chaetica with porous tips, which may have gustatory functions. The distal end of the ovipositor bore numerous dome-shaped sensilla. However, there were no sensilla coeloconica or styloconica, known to have gustatory function in other parasitoid species, on the ovipositors of the two braconid wasps.     

Female reproductive system of the decapitating fly Pseudacteon wasmanni Schmitz (Diptera: Phoridae)

Pseudacteon wasmanni is a South American decapitating fly that parasitizes workers of Solenopsis fire ants. We used light microscopy (historesin serial-sectioning stained with Haematoxylin/Eosin) and scanning electron microscopy to show and analyze internal and whole external views of the female reproductive system. All specimens analyzed (n=9) by light microscopy showed post-vitellogenic oocytes inside the ovaries. The lack of typical follicles (oocyte-nurse cell complexes) in all specimens suggests that oogenesis occurs during the pupal stage. The total number of eggs found ranged from 31 to 280 (X=142±73, SD). The egg has a slugform or torpedo shape (about 130 by 20 μm) with a pointed apex at the posterior pole as defined by the fly; the micropyle appears to be in a depression or invagination at the anterior pole. An acute hypodermic-like ovipositor is evaginated from the hard sclerotized external genitalia during egg laying. The existence of a muscular bulb associated with the end of the common oviduct suggests that the egg is injected into the ant's body by a strong contraction of the bulb which probably is stimulated by bending of several ventral sensilla. During contraction, the abdomen extends out along a large fold between the sixth and seventh tergites in such a way that the sclerotized genitalia is rotated ventrally into a slightly anterior orientation in preparation for oviposition.     

Male coloration signals direct benefits in the European bitterling (Rhodeus amarus)

Female mating preferences are frequently associated with exaggerated male sexual traits. In the European bitterling, Rhodeus amarus, a fish with a resource-based mating system, male coloration is not associated with indirect genetic benefits of female mate choice, and does not reliably signal spawning site quality. We tested a link between the extent of male carotenoid-based coloration and testis size and number of spermatozoa stripped from the testes. Male body size predicted spermatozoa number, but less reliably than the extent of male coloration. Male color was a highly significant predictor of spermatozoa number, with approximately 26 % of variance in the number of spermatozoa stripped from males predicted from male color after controlling for male body size. Body size, but not coloration, predicted teste size. Female bitterling often risk sperm limitation, especially during pair spawnings, and male nuptial coloration may be under direct selection through female mate choice as a signal of male fertilization efficiency.     

Copulation anatomy of Drosophila melanogaster (Diptera: Drosophilidae): wound-making organs and their possible roles

Males of several insect species inflict wounds on female genitalia during copulation. Such copulatory wounding also occurs in the fruit fly Drosophila melanogaster Meigen, 1830, one of the most important model organisms. Using a flash fixation technique with mating pairs of D. melanogaster, I examined the use and functions of the male phallic organ within the female reproductive tract. Paired components of the phallic organ (gonopods and two pairs of branches of the basal processes of the aedeagus) opened sequentially, from outer to inner components, during copulation. The dorsal branches of the aedeagal basal processes pierced the intima of the female reproductive tract at the lateral shallow folds. Consequently, mated females usually had a pair of melanized patches from repaired copulatory wounds. The sites that were stabbed by the dorsal branches were also clutched on the outside of the female oviscape (ovipositor) by the posterior process, which is a component of the periphallic organ. These structures likely function together as a mate-holding device. Male ejaculate labeled with rhodamine-B fluorescent dye entered the copulatory wounds in D. eugracilis Bock and Wheeler (Univ Texas Publ 7213:1–102, 1972), a related species, but not in D. melanogaster. Thus, copulatory wounds may function as an entrance for male seminal chemicals into the female circulatory system in D. eugracilis, but might not in D. melanogaster.     

Structural peculiarities of the tubercles in the skin of the turbot,Scophthalmus maximus (L., 1758) (Osteichthyes,Pleuronectiformes, Scophthalmidae)

The structure of the bony tubercles of the turbot, Scophthalmus maximus (L., 1758), was examined using ground sections, microradiography, SEM, and TEM. The tubercles are small, isolated, mineralized conical plates randomly distributed in the eyed side of the body. They are composed of three layers: the outer limiting layer, the external layer, and the basal plate, which make up the thin and flat elasmoid scales of Teleostei. The main difference between regular elasmoid scales and bony tubercles lies in the organization and the growth of the basal plate. Indeed, the conical shape of the tubercle is the result of a prominent thickening of the central part of the basal plate where the collagen matrix is organized in a complicated three-dimensional network. Densely packed thick collagen fibrils form superimposed plies organized in a plywood-like structure that resembles that of the elasmoid scales but it is criss-crossed by numerous vertical sheets of thin collagen fibrils. The tubercles originate from thin and flat plates located in the skin of larvae and juveniles, whose structure is that of regular-developing elasmoid scales. Thus, the tubercles of Scophthalmus maximus could be considered as modified elasmoid scales rather than bony structures. They might be the result of specific arrangements related to the general trend of reduction of the dermal skeleton in the teleostean lineage.     

Internal micromorphology of the frons plate in females of the oriental hornet

Scanning electron microscopy and energy dispersive x-ray analysis (SEM/EDS) have been used to study the internal micromorphology of the frons plate in the Oriental hornet, Vespa orientalis. A conical shaped organ was described which is recessed into the frons plate and projects toward the interior of the acoustic box. The latter is located on the inner side of the frons plate. On the exterior of the conical region are observed aggregates containing Ca and Si, and a thin transparent membrane bearing a hole in its center. The innermost surface of the conical structure terminates bluntly as a convex lentiform tip, bearing a transparent oval-shaped window in its center. The conical organ, excepting the window, is enclosed in several layers of epithelium. The structure of this many-layered conical organ is highly complex; its numerous sub-structures and the possible role as a gravity sense organ are discussed. © 1993 Wiley-Liss, Inc.     

The role of the European bitterling (<Emphasis Type="Italic">Rhodeus amarus,</Emphasis> Cyprinidae) in parasite accumulation and transmission in riverine ecosystems

In aquatic ecosystems, fish play a key role in parasite accumulation and transmission to predacious animals. In the present study, realized on seven populations of a small cyprinid fish species, the European bitterling Rhodeus amarus, we investigated (1) the role of the European bitterling as a potential intermediate or paratenic host, (2) the ability of the fish to accumulate parasites with similar final host group, and (3) its significance as a potential source of parasite infection in the ecosystem in respect to habitat characteristics. A total of 36 parasite species were recorded; 31 species (90% of all parasite specimens) were classified as endoparasites. Most of the endoparasites were found in the larval life stage, using bitterling as an intermediate or paratenic host. In particular, parasite community structure showed significantly higher proportions of allogenic parasites in comparison with autogenic. The supposed co-occurrence of parasite species with identical final host groups showed only a weak association. The adjacent reservoir areas were a significant determinant of both the total and infracommunity parasite species richness and for the mean parasite abundance. No relationship between the distance of sampling site from the adjacent reservoir and parasite community characteristics was found. As a small-sized fish with a wide distribution range and high local abundances, the European bitterling can represent a natural prey for a wide range of piscivorous predators. Due to its susceptibility to the number of larval endoparasites, this fish species may therefore fulfill the role as important transmitter of parasites to their final hosts.     

Morphological characterization of the ovary and oocytes vitellogenesis of the tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae)

This study presents the morphology of the ovary, as well as the process of the vitellogenesis in oocytes of the tick Rhipicephalus sanguineus. The ovary of these individuals is of the panoistic type; therefore, it lacks nurse cells. This organ consists of a single tubular structure, continuous, and composed of a wall formed by small epithelial cells with rounded nuclei which delimit the lumen. The oocytes in the different developmental stages in this tick species were classified into five stages (I-V). They remain attached to the ovary during vitellogenesis by a cellular pedicel and afterwards the mature oocytes (stage V) are released into the ovary lumen.