Meroistic Ovarioles Research Articles

The timings of vitellogenesis and choriogenesis in the Henosepilachna vigintioctopunctata oocytes

In order to provide a biological basis for the development of population management strategies, a critical need is to better understand the reproduction of agricultural pests. In the current paper, we timed the previtellogenesis, vitellogenesis and choriogenesis processes in Henosepilachna vigintioctopunctata (Fabricius), (Coleoptera, Coccinellidae), a serious polyphagous defoliator damaging a wide range of crops in Solanaceae and Cucurbitaceae. The female reproductive system was comprised of two ovaries, two lateral oviducts, a median oviduct, a spermathecal sac and a genital chamber. Each ovary had an average of 28 (±0.4) telotrophic meroistic ovarioles. In the ovarioles of 4-day-old females, only previtellogenesis process was observed. The vitellogenesis occurred at 5 to 7 days after female emergence, while the choriogenesis took place at 8 and 9 days post eclosion. Copulation and oviposition occurred before and at 8 days post emergence. In order to confirm the observation, HvVgR and HvVg were identified and their expression was examined. HvVgR was abundantly transcribed in the ovary, whereas HvVg was richly expressed in the fat body. The temporal expression profiles showed that the high levels of HvVgR and HvVg were accompanied with the active accumulation of yolk proteins and the occurrence of intercellular spaces among follicle cells. Moreover, only one oocyte was observed per ovariole in active vitellogenesis. The observation demonstrates that oocytes are continuously matured and the oviposition persists in females from 8 days to at least 13 days post eclosion.

Notes on the female reproductive system of the red‐and‐black froghopper, Cercopis vulnerata Rossi, 1807 (Hemiptera: Cercopidae)‐light and electron microscopy studies

AbstractThe morphology of the female reproductive system in Cercopis vulnerata, an economically important species, was examined with light and scanning electron microscopy techniques. The female reproductive system of C. vulnerata has two ovaries, each containing 14 telotrophic meroistic ovarioles joined by two lateral oviducts that open in a common oviduct. In this type of ovarioles, the trophocytes within the germarium are transferred to the developing oocytes in the vitellarium via the nutritive cords. The oocytes in the vitellarium have three different development stages: previtello, vitello and choriogenesis. The ovarioles open in the lateral oviduct with a thin canal‐shaped pedicel. A pair of lateral oviducts opens distally into the common oviduct. The oviducts are surrounded by a monolayer cubical epithelium with deep folds toward the lumen and a thick muscle layer. A pair of spermatheca and a bursa copulatrix are seen near the common oviduct. Spermatheca has an elongated shape. The bursa copulatrix has an ovoid tube‐like structure. No work has been done on the female reproductive system of Cercopidae to date. This study was conducted to fill this gap and forms part of the female reproductive system morphology of this economically important insect.

Ovary Structure and Oogenesis of Trypophloeus klimeschi (Coleoptera: Curculionidae: Scolytinae)

Simple SummaryColeoptera is the largest animal taxon, with many species being agricultural and forest pests. The phylogeny of these species has aroused great interest among scientists. The characteristics of ovariole structure and ultrastructure are useful for phylogenetic work, especially with the improvement of micro technology in recent years. The types of ovarioles are varied. Usually, each family conforms to one type or another. However, in this study, we report on the ovaries of Trypophloeus klimeschi (Coleoptera: Curculionidae: Scolytinae), and find a different ovariole type from that of other known species of Curculionidae. We describe the features of the female reproductive system, ovary and oogenesis of T. klimeschi and also compare these features with those found in other Curculionidae. This study provides novel information on the reproductive biology of the Curculionidae.The female reproductive system, ovary structure and ultrastructure of Trypophloeus klimeschi (Coleoptera: Curculionidae: Scolytinae) were investigated using light microscopy, scanning electron microscopy, and transmission electron microscopy. Its female reproductive system is comprised of two ovaries (each ovary has two ovarioles), lateral oviducts, common oviduct, spermathecal sac, spermathecal pump, two accessory glands and bursa copulatrix. Well-developed endoplasmic reticulum can be clearly seen in the secretory cells of spermathecal sac. This species has telotrophic meroistic ovarioles that are comprised of terminal filament, tropharium, vitellarium and pedicel. The terminal filaments are simple; each is comprised of cellular peritoneal sheath. The presence of several clusters of nurse cells in the tropharium is indicative that its ovarioles conform to the transition stage. This indicates that there are at least two different types (transition stage and secondary stage) of ovarioles in Curculionidae.

Egg maturation by Gonatopus bonaerensis (Hymenoptera: Dryinidae) when provided with two species of planthopper (Delphacidae) as hosts

Type of ovariole, oöcyte maturation, and ovigeny pattern in the parasitoid Gonatopus bonaerensis Virla (Hymenoptera: Dryinidae) were studied using two species of Delphacidae as hosts. The ovaries of G. bonaerensis are composed of three polytrophic meroistic ovarioles. Females are autogenic and the initial egg load averages 3.7 mature eggs. G. bonaerensis is a strongly synovigenic species when parasitizing its usual host, Delphacodes sitarea Remes Lenicov and Tesón (Hem.: Delphacidae); however, when attacking the non-preferred host Peregrinus maidis (Ashmead) (Hem.: Delphacidae), it is weakly synovigenic. Although the number of mature oöcytes increases 3.8-fold during the first 48 h after the emergence, egg numbers decrease significantly in females that spend over 72 h deprived of hosts, apparently as a result of resorption. These results are discussed in the context of rearing and manipulating G. bonaerensis as a biocontrol agent of planthoppers, which are vectors of phytopathogens.

Structure and ultrastructure of the ovary in the South American Veturius sinuatus (Eschscholtz) (Coleoptera, Passalidae)

The morphoanatomy of the ovary in Veturius sinuatus (Eschscholtz) was studied by light and transmission electron microscopy. Data from the female gonad of this species provide more extended and precise knowledge regarding the organization of the ovary in Passalidae. Ovaries are composed of a pair of long telotrophic meroistic ovarioles, with some differences compared to the bauplan of this ovary type in Polyphaga (Coleoptera). The terminal filament has an enlarged proximal region with irregularly shaped cells in apparent degeneration process embedded in a membranous system. Globular structures with amorphous content associated with interstitial cells are distributed throughout the tropharium. Trophocytes develop with the reduction of the plasma membrane between sibling nurse cells of each cluster. Previtellogenic oocytes have an irregular shape and various cytoplasmic prolongations. As oogenesis advances, a single prolongation in the anterior part of the oocyte extends to the tropharium. The ovary structure is comparable to that found in other American species of passalids, and further, the conformation of the terminal filament could be a plesiomorphic character of the family.

Contrasting patterns of ovarian development and oogenesis in two sympatric host-feeding parasitoids, Diglyphus isaea and Neochrysocharis formosa (Hymenoptera: Eulophidae)

Diglyphus isaea (Walker) and Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae) are common idiobiont parasitoids of leafminers attacking vegetable crops. They exhibit differing levels of synovigeny, and host feeding enhances their fecundity and longevity. The reproductive systems of these two parasitoids are typical of hymenopteran eulophids, consisting of two ovaries, each usually comprising three polytrophic meroistic ovarioles. Diglyphus isaea possesses two obvious oviduct accessory glands, which are absent in N. formosa. Both parasitoids underwent oosorption when starved, while feeding on host larvae promoted oogenesis and egg maturation. In both, oogenesis and vitellogenesis commenced on the first day of the pupal stage rather than after eclosion. Formation of ovarioles in D. isaea commenced 1 day earlier than in N. formosa. Mature eggs were rarely observed in ovaries of newly emerged D. isaea, but usually a few were present in N. formosa. When hosts (second–third instar Liriomyza sativae larvae) were provided, the number of mature eggs in D. isaea ovaries initially increased and then stabilized, while in N. formosa, the number first increased and then decreased. Diglyphus isaea had fewer but larger eggs than N. formosa did. Thus, synovigenic divergence begins at the pupal stage and may result in different life-history traits of adults.

Functional morphology of the female reproductive apparatus of Stephanitis pyrioides (Heteroptera, Tingidae): A novel role for the pseudospermathecae

At mating, female insects generally receive and store sperm in specific organs of their reproductive tract called spermathecae. Some Heteroptera, such as Cimicomorpha, lack a true spermatheca; some have receptacles of novel formation where sperm cells can transit or be stored. In Tingidae, there are two sac-like diverticula, the "pseudospermathecae," each at the base of a lateral oviduct, which previously were considered to function as spermathecae. However, this role has never been documented, either by ultrastructural studies or by observations of sperm transit in the female reproductive tract. In this article, we investigate the morphology and the ultrastructure of the female reproductive apparatus in the economically important tingid species Stephanitis pyrioides, focusing our attention on the functional role of the pseudospermathecae in an evolutionary perspective. Each ovary consists of seven telotrophic meroistic ovarioles, the long pedicels of which enlarge into a bulb-like structure near the terminal oocyte. The ovarioles flow into two long lateral oviducts, which join to form a very short common oviduct. Basally, each lateral oviduct is connected through a short duct to one of two pseudospermathecae. The ultrastructure of the ectodermal epithelium of the pseudospermathecae is dramatically different in sexually immature or mated females. In virgin females, cells delimit a very irregular lumen, filled with a moderately electron-dense granular material. The large nucleus adapts to their irregular shape, which can have long projections in some regions and be flattened in others. After mating, epithelial cells generally elongate and display an apical layer of microvilli extending beneath the cuticle, often containing mitochondria. In the lumen of the pseudospermathecae there is a dense brownish secretion. No sperm cells were ever found inside this organ. After mating, sperm move upward along the lateral oviducts and the ovarioles, accumulating in the bulb-like structure of the pedicels, and proceeding into the distal region between the follicle cells surrounding the oocyte and the ovariole wall. The egg, most likely fertilized in the bulb-like region of the ovariole, moves through the lateral oviduct, entirely enters the pseudospermatheca and is smeared with its secretion just before oviposition. We exclude a function of sperm storage for the pseudospermathecae, and instead suggest a novel role for these organs as reproductive accessory glands.

Structure of the Ovary and “Nurse Cells” in a Freshwater Ostracod, Cyprinotus uenoi Brehm (Podocopida: Cypridoidea)

The adult female of the freshwater ostracod Cyprinotus uenoi Brehm, 1936 (Podocopida: Cypridoidea) has a pair of long, sac-like ovaries separately lying in the posterior part of the left and the right carapace valves. Oogonia and very early previtellogenic oocytes are located in the terminal germarium of each ovary. In the germarium, the oogonia occur in the most terminal region, and the very early previtellogenic oocytes are located in the remainder, arranged in order of size, the larger ones nearer the ovarian lumen. Most of the growing oocytes, previtellogenic and vitellogenic, are found in the ovarian lumen, the larger ones farther from the germarium. In the germarium, a cytoplasmic bridge connects a pair of adjoining germ cells, resulting from an incomplete cytokinesis of oogonial division. Among the previtellogenic and early vitellogenic oocytes in the ovarian lumen, "nurse cells" are found as small, spherical cells in mostly the same number as these oocytes. A cytoplasmic bridge connects each "nurse cell" to an adjoining oocyte. Based on the manner of connection and some morphological features, we consider that each "nurse cell" originates from one of each pair of adjoining germ cells connected by a cytoplasmic bridge in the germarium, as in the true nurse cells of several branchiopod crustaceans and insects with meroistic ovarioles.

Ovariole structure supports sistergroup relationship of Neuroptera and Coleoptera

Insect ovaries consist of functional units, the ovarioles. Each ovariole is a polarized tube with a germarial region at its anterior end. Undifferentiated germarial germ cells may differentiate either into oocytes alone (so-called panoistic ovarioles) or in oocytes and nurse cells (so-called meroistic ovarioles). Whenever nurse cells accompany an oocyte through all growth periods in a separated physiological unit – the follicle – the subtype is called polytrophic meroistic. In telotrophic meroistic ovarioles all nurse cells remain in an anterior trophic chamber and contribute their products finally into all growing oocytes via nutritive cords. Differences in the mode of germ cell cluster formation and the specifi c interaction of germ cells with the somatic tissues were causing these different types. All three types are constant at the family to order level or even at a supra-order level. Therefore the characters which lead to these types are excellent candidates to unravel order and supraorder ranked taxa. Data from the analysis of germ cell cluster formation are presented which corroborate the sistergroup relationship of Neuropterida and Coleoptera.

Germ-cell cluster formation in the telotrophic meroistic ovary of Tribolium castaneum (Coleoptera, Polyphaga, Tenebrionidae) and its implication on insect phylogeny

Tribolium castaneum has telotrophic meroistic ovarioles of the Polyphaga type. During larval stages, germ cells multiply in a first mitotic cycle forming many small, irregularly branched germ-cell clusters which colonize between the anterior and posterior somatic tissues in each ovariole. Because germ-cell multiplication is accompanied by cluster splitting, we assume a very low number of germ cells per ovariole at the beginning of ovariole development. In the late larval and early pupal stages, we found programmed cell death of germ-cell clusters that are located in anterior and middle regions of the ovarioles. Only those clusters survive that rest on posterior somatic tissue. The germ cells that are in direct contact with posterior somatic cells transform into morphologically distinct pro-oocytes. Intercellular bridges interconnecting pro-oocytes are located posteriorly and are filled with fusomes that regularly fuse to form polyfusomes. Intercellular bridges connecting pro-oocytes to pro-nurse cells are always positioned anteriorly and contain small fusomal plugs. During pupal stages, a second wave of metasynchronous mitoses is initiated by the pro-oocytes, leading to linear subclusters with few bifurcations. We assume that the pro-oocytes together with posterior somatic cells build the center of determination and differentiation of germ cells throughout the larval, pupal, and adult stages. The early developmental pattern of germ-cell multiplication is highly similar to the events known from the telotrophic ovary of the Sialis type. We conclude that among the common ancestors of Neuropterida and Coleoptera, a telotrophic meroistic ovary of the Sialis type evolved, which still exists in Sialidae, Raphidioptera, and a myxophagan Coleoptera family, the Hydroscaphidae. Consequently, the telotrophic ovary of the Polyphaga type evolved from the Sialis type.

Structural aspects of ovarian sheaths inPhormia regina(Meigen) (Diptera, Calliphoridae)

Each ovary in Phormia regina consists of numerous meroistic ovarioles held together by an ovarian muscle sheath. Each ovariole is enclosed by a thin ovariolar sheath that becomes continuous with the more external ovarian muscle sheath at the germarial tip. In previtellogen ic and early vitellogenic ovaries, terminal follicles are connected to the lateral oviducts through a system of ovarian tubules and ducts. Ovarian tubules establish a continuity between the ovariolar sheath of terminal follicles and the ovarian ducts. The latter form a system of branching luminal continuities that run underneath the ovarian muscle sheath. While ovarian ducts are permanent structures in the ovary, ovarian tubules are restricted to early vitellogenic ovaries. In ovaries at more advanced stages, terminal follicles connect directly to the ovarian ducts over the convex side of the ovary. Thus, on this convex side the ovary is surrounded by a sheath-like covering. We suggest that the various sheaths are so disposed as to allow a directional flow of hemolymph through the ovary to gain access to each terminal follicle.

Potassium channel blockers unmask electrical excitability of insect follicles

AbstractStandard techniques for intracellular recording and current injection were used to determine if the developing ovarian follicles of six species of insect were electrically excitable. Follicles were dissected from the panoistic ovarioles of Locusta migratoria and Periplaneta americana, the polytrophic meroistic ovarioles of the fruit fly Drosophila rnelanogaster and the silkworm moths Hyalophora cecropia and H. Columbia, and the telotrophic meroistic ovarioles of the mealworm beetle Tenebrio mlitor. Follicles of all species except Tenebrio were inexcitable in control saline; Tenebrio follicles produced short action potentials which did not outlast the duration of the current pulse. Follicles of all species except Drosophila produced long duration overshooting action potentials when depolarized in salines containing the potassium channel blockers tetraethylammonium (TEA; 10–80 mM), Bazf (10–20 mM) and 4‐aminopyridine (4‐AP; 10 mM). Hyalophora follicles were also excitable in saline containing TEA and Ba2+ but not 4‐AP, and Tenebrio follicles were excitable in saline containing Ba2+ but not TEA and 4‐AP. Excitability in follicles of all species was unaffected by sodium replacement but was reversibly inhibited by the calcium channel blockers La3+ (1 mM), Co2+(10 mM), or verapamil (0.1‐1.0 mM). It is suggested that the action potentials are caused by the movement of calcium or barium through voltage‐dependent channels that are masked in control saline by a large counteracting potassium conductance. Excitability appears to be a property of the oolemma and not the follicle cell membranes. Possible functions of voltage‐dependent ion channels in insect oocytes are discussed.

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

AbstractThe 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.

Morphology, ultrastructure, and germ cell cluster formation in ovarioles of aphids.

The structure of aphid ovaries, including ovipare and virginopare morphs of five species, was investigated by light and electron microscopy. Aphids contain telotrophic meroistic ovarioles. The amount and distribution of cytoplasmic components of nurse cells, nutritive cords, and young oocytes are nearly identical to those known from scale insects and heteropterans. Each ovariole has a constant number of nurse cells and oocytes. In ovaries of ovipare morphs, the nurse cell nuclei enlarge by endomitosis (n = 28 n-210 n), whereas in virginopare morphs the nurse cell nuclei remain small (n = 22 n-24 n). Furthermore, in virginoparae the previtellogenic growth of oocytes is highly reduced, and vitellogenesis and chorionogenesis are blocked totally. Embryogenesis starts immediately after the shortened previtellogenic growth. In each ovariole, all germ cell descendants belong to one germ cell cluster that follows the 2n rule. The cluster normally contains 25 = (32) cells, but other mostly smaller numbers also occur. In contrast to polytrophic meroistic ovarioles, more than one cell of each cluster will develop into an oocyte. In Drepanosiphum platanoides, 16 (2n-1 ) nurse cells and 16 (2n-1 ) oocytes exist in each cluster, whereas, in Metopolophium dirhodum, 8 (2n-2 ) oocytes and 24 (2n-1 + 2n-2 ) nurse cells are normally found. In many ovarioles of Macrosiphum rosae, 21 nurse cells nourish 11 oocytes. Models of germ cell cluster formation in aphid ovaries are discussed.

The meroistic insect ovary as a miniature electrophoresis chamber

1. 1. In meroistic ovarioles, the oocyte and the trophocytes are sibling cells, interconnected by cytoplasmic bridges as a result of incomplete cytokinesis. 2. 2. In the moth H. cecropia, a potential difference of about 6 mV is observed over the 30 μm wide open cytoplasmic bridge between the trophocyte compartment and the oocyte. 3. 3. Intracellular electrophoresis was clearly illustrated by following the migration of micro-injected fluorescent basic or acidic macromolecular probes. 4. 4. Extracellular electrical current patterns around meroistic ovarioles have been measured by means of the ultrasensitive microvibrating probe. 5. 5. This electrophoresis principle may lead to new insights into the mechanisms controlling the cell cycle, gene expression and differentiation.

Autoradiographic studies on the oosome in the oocyte ofPimpla turionellae L. (Hymenoptera)

During the longitudinal growth of the oocytes ofPimpla the voluminous oosome area has considerable amounts of newly synthetized proteins (= 1st stage of oosome formation). Short time incubations result in labelling the oosome area as distinctly as the plasm in the nurse cells, in spite of the considerable distance between nurse cells and oosome area. Thus there is no evidence of trophocytic proteins being transported towards the oosome. Consequently during the 1st stage of oosome formation more proteins are synthetized in the oosome area than in the ooplasm.All over the oocyte, oocytic and extra-oocytic components are adding to the propagation of ooplasm (intussusceptive growth). During the 1st stage of its formation, the oosome could possibly contain an additional system for appositional growth within the posterior part of the oocyte, or/and the proteins synthetized herein could play a part in the synthesis of fats. Further questions in connection with these preliminary hypotheses can be answered by more refined methods only. During the oocytic stages following the degeneration of the nurse cell chamber (= 2nd stage of oosome formation), the ever more ball-shaped oosome accumulates trophocytic RNA, which is present all over the rest of the egg space as well. This stable RNA is meant to serve either for the somatic embryogenesis or the germ line.Further autoradiographic observations of the ovarioles essentially confirm known facts concerning the extra-oocytic supply of the oocyte as stated for meroistic ovarioles. This includes the supply with stable and unstable RNA from the nurse cell chamber and proteins from haemolymph for vitellogenesis as well as nurse cell plasm rich in RNA, available during the degeneration of the nurse cell chamber.