Oogenesis and ovarian morphology in pollinating and non-pollinating fig wasps: evidence from adult and immature stages

Hymenopteran insects have meroistic polytrophic ovaries characterised by trophocytes associated with oocytes inside the follicles. In pro-ovigenic species, all oocytes mature before emergence and no trace of oogenesis is visible in adult females. Pro-ovigeny is a rare condition among Hymenoptera, but common in pollinating fig wasps. In the present investigation, we studied adult and pupa females of three fig wasp species with different trophic strategies. We demonstrated that females of Pegoscapus aerumnosus and Idarnes spp. have an unusual ovarian organisation (i.e. each ovariole has only one mature egg and no oocyte) that has led to misleading interpretation of fig wasp reproductive anatomy. The ovaries of these studied species have several ovarioles, recognisable by the presence of nuclei of tunica propria cells surrounding them. Each adult wasp ovariole had one mature egg. None of the pupae had mature eggs, but all of them had follicles with oocytes in different developmental stages. The studied fig wasps are pro-ovigenic, irrespective of their trophic strategy, since there were no signs of ovigeny in adult females. We discuss ecological and phylogenetic factors that could play a role in fig wasps reproductive strategies.     

Factors affecting egg maturation in the bean weevil Callosobruchus maculatus

Abstract. This paper concerns the effects of mate and seed availability on the rate of egg maturation in the bean weevil Callosobruchus maculatus (F.). Egg maturation starts before emergence from the seed and, provided that both oviposition sites and mates are available, eggs are laid at a rate determined by the number of oviposition sites, and mature at a similar rate. If seeds or mates are absent then a small number of eggs are laid, but oocytes continue to mature until the oviduct-capacity is approached. The number of eggs that a female can store is dependent on her body weight and does not correlate with the number of ovarioles. If, after a period in which oocyte development has been halted, conditions for egg-laying become suitable, then egg maturation can be re-started, but only after the oviducts have been emptied of eggs. The rate of egg maturation is then similar to that for females of the same age which have been maturing eggs since emergence.     

Assessing the age of field female wheat bulb flies (Leptohylemyia coarctata)

From 1967 to 1971, wheat bulb fly females caught by sweeping from a number of localities contained mature eggs from the third week of July to the end of August. In 1971 when female wheat bulb flies were caught by sweeping, by white water traps, by suction traps as well as by light traps, the first flies containing mature eggs were caught 29 days after the first detected emergence while the first batch was laid 29–58 days after first emergence. The peak period of egg laying occurred in the fourth week of July, 24–38 days after the peak emergence. The second batch of eggs was laid when the flies were 8 weeks old, 29 days after the first; the peak for this batch was 35 days after the first. A few females laid a third batch of eggs 28 days after the first record of the laying of the second batch. A female that lives sufficiently long to lay the third batch of eggs is at least 12 weeks old. In 1970, when emergence started earlier in June, ripening and laying of eggs of the three batches was also earlier. After the harvest of cereal crops more females were caught by white water traps placed on the fallow than by other methods. The most important pathogen affecting adult wheat bulb flies was a fungus, probably Entomophthora muscae. When infection occurred early in July, fewer eggs from the first batch were laid than when infection developed later. Fewer flies were infected in 1971 than in 1970. To be effective against wheat bulb fly in the early spring, control measures-should be applied against adults before their eggs mature in early July of the preceding year.     

Effects of host stage on the development of the facultative autoparasitoid Encarsia tricolor (Hymenoptera: Aphelinidae)

Encarsia tricolor is a facultative autoparasitoid of the glasshouse whitefly, Trialeurodes vaporariorum, with a potential in biological control. The rate of development, number of mature oocytes at emergence, number of ovarioles and size of the emerged adults were studied. Five nymphal instars (N1, N2, N3, N4, and pharate adult) of T. vaporariorum were used as hosts for the females. Female larvae and pupae of E. tricolor and Encarsia formosa were used as hosts for the males. Females developed faster when the egg was laid on N3 (18.0 days from egg to adult) and slower on N1 (22.3 days). Females were bigger when developing from N1 and N3 than from N4 and pharate adult. On emergence the mean number of mature oocytes was always small (0.8–2.6). Males developed faster and were smaller than females, and developed faster and were larger on larvae of E. formosa.     

Oogenesis in antenatal development in man

Summary Ninety-seven female embryos and foetuses aged 6–40 weeks were quantitatively analyzed for germ cell development, mitotic activity in the ovary, and dynamics of chromosome transformations in oocytes at the stages of meiotic prophase I and follicle genesis. For the first time, chronology of oocytes dynamics at the stage of the preleptotene chromosome condensation and decondensation is described. Oocytes at the leptotene stage occur in embryos aged 10–11 weeks. Oocyte transfer at the zygotene and pachytene stages starts by 10.5–11 and 11.5–13 weeks, respectively. Their number is maximum after 26 weeks and by the 40th week decreases to just single oocytes. The first oocytes at the diplotene stage appear in foetuses aged 11.5–12 weeks. Oocyte transition to the dictyotene stage is observed in single oocytes after 16 weeks of development, but active bivalent decondensation begins after 26 weeks.The formation of a follicular layer takes place not earlier than around the oocyte at the diplotene stage. Follicle genesis occurs after 11–12 weeks. Transformation of primordial follicles into primary ones is intensified after 19–20 weeks. By the moment of birth, the majority of oocytes in the human ovary are contained in primary follicles, and only a few are contained in primordial ones. The number of secondary and tertiary antral follicles is extremely small. The dynamics of degeneration of germ cells throughout intra-uterine development is also described.     

多巴脱羧酶对异色瓢虫生殖力的调控机制

[目的]为了探究多巴脱羧酶(DOPA decarboxylase,DDC)对异色瓢虫Harmonia axyridis生殖力的影响及其调控机制.[方法]利用RNA干扰技术(RNA interference,RNAi),将异色瓢虫4龄幼虫的DDC基因(HaDDC)抑制表达,成虫羽化后第8天开始统计20 d内累计产卵量及产...     

Ovariolenverlängerung und eiablage bei der termite Kalotermes flavicollis Fabr

Zusammenfassung Die Oogenese der Termite Kalotermes flavicollis Fabr. wurde nach der Form der Oocyten in Phasen gegliedert (Abb. 2). Die panoistisehen Ovariolen enthalten in linearer Anordnung Oocyten der verschiedensten Entwicklungsstadien. Beide Ovarien haben insgesamt 14 Ovariolen (Abb. 1). Diese Zahl findet sich in Larven, Nymphen, Soldaten und in Geschlechtstieren unterschiedlichen Alters. Die einzelnen Ovariolen eines Weibchens enthalten unterschiedliche Anzahlen von Oocyten. Es reifen immer nur einige Oocyten gleichzeitig (Abb. 6, 7).Junge Geschlechtstiere legen anfangs nur wenige Eier. Die Eiproduktion erhöht sich später mit dem Ansteigen der Zahl der Individuen in der Kolonie. Eine erhebliche Erhöhung der Eiproduktion ist bei alten Geschlechtstieren aus großen Völkern festzustellen. Diese Erhöhung der Eiproduktion kommt dadurch zustande, daß die Ovariolen in die Länge wachsen und sich die Zahl der Oocyten im Vitellarium erhöht (Abb. 5a, b, c und 8a, b, c). Es besteht nämlich eine Korrelation zwischen der Ovariolenlänge und der Zahl der abgelegten Eier pro Zeiteinheit. Die Verlängerung der Ovariolen kommt unter dem Einfluß des Volkes zustande. Es kommt zu keiner Verlängerung der Ovariolen bei Weibchen, die länger als zwei Jahre nach dem Schwärmen isoliert gehalten werden. Die Verlängerung der Ovariolen könnte durch die Menge und Art der Nahrung oder ouch durch Wirkstoffe zustande kommen.Der Dottereinbau setzt erst ein nach der Geschlechtstierhäutung, die zu einem imaginalen oder neotenischen Geschlechtstier (Ersatzgeschlechtstier) führen kann. Der Zeitpunkt des Einsetzens des Dottereinbaus fällt bei der Imago zusammen mit dem Einsetzen der Pigmentierung. Es besteht eine Korrelation zwischen Zahl der dottereinbauenden Oocyten pro Ovariole und der zunehmenden Verlängerung der Ovariolen. Es wurden his zu sieben dottereinbauende Oocyten in einer Ovariole festgestellt (Abb. 8a, b, c).

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Summary A subdivision of the oogenesis in Kalotermes flavicollis Fabr. (Isoptera) is described according to the form of the oocytes (Fig. 2). Each ovariole (panoistic type) contains a linear array of oocytes in varying stages of development. Both ovaries together consist of 14 ovarioles (Fig. 1). This number is found in larvae, nymphs; soldiers; in young reproductives and in reproductives aged some years. The number of oocytes varies in the ovarioles of a female. Mature eggs occurs at the same time only in few of ovarioles (Fig. 6, 7).Young reproductives lay only few eggs. The production of eggs increases with increasing number of individuals of the colony. A marked increase of egg production is observed in old reproductives of big colonies. This increase of egg production results from growth in length of the ovarioles and from an increase of the number of oocytes in the vitellarium (Fig. 5a, b, c and 8a, b, c). The length of the ovarioles is correlated with the number of eggs laid within a certain period. The lengthening of the ovarioles is caused by influences from the individuals of the colony. No lengthening of ovarioles took place in females kept singly for more than two years after swarming. The lengthening of the overioles seems to depend on the quantity and the quality of food and/or vitamins.The deposition of yolk takes place only after moulting into a reproductive (imago or neoteinic = replacement reproductive). The start of yolk deposition occurs simultaneously with the start of pigmentation. The number of yolk depositing oocytes increases with the increase of the length of the ovariole. Up to seven yolk depositing oocytes were observed in each single ovariole (Fig. 8a, b, c).

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Worker laying in leafcutter ant Acromyrmex subterraneus brunneus （Formicidae, Attini）

We studied the process of offspring production in queenless colonies of Acromyrmex subterraneus brunneus, and particularly evaluated the ovary development of workers as a function of their age. For this, subcolonies were set up and evaluated at different periods of isolation from the queen （2, 4 and 6 months）, besides individually labeled age groups. The subcolonies were assessed according to offspring production and ovaries containing oocytes or not. The evaluations showed worker oviposition and development of males originating from worker-laid eggs. At 2 months＇ absence of the queen, eggs and larvae were found, with eggs in a higher proportion than larvae. After 4 months, the proportion of eggs had reduced while larvae had increased, and a pupa was found in one subcolony. At 6 months, besides a higher share of larvae, one pupa and one adult male were found. Dissection of workers revealed ovaries containing oocytes during the periods of evaluation. Only a group of medium-sized and large workers, 23.3%, 20.9% and 37.5% of the population from each period assessed in queenless subcolonies respectively, presented developed oocytes in the ovary. The same was observed in colonies with a queen, with 17.6%, 19.6% and 7.8% of the group of dissected workers from each time period, respectively. With respect to worker age, we observed by dissection of the ovary, that the greatest percentage of individuals with ovarioles containing oocytes occurred at 45 days （6 weeks） up to 90 days （12 weeks）. These results probably are associated with the workers reproduction and the laying of trophic and reproductive eggs in colonies with and without a queen; these eggs have distinct functions in each situation.     

The relationship between mating and oogenesis in monarch butterflies (Lepidoptera: Danainae)

We studied the relationship between the timing of mating and oogenesis in monarch butterflies (Danaus plexippus) to determine (1) the potential for male nutrient input into eggs and (2) whether mating stimulates egg development. Most females mated soon after they started maturing eggs. One and 2 days after mating, females contained the same number of mature oocytes as virgin females of the same age, while 3 days after mating they contained more mature oocytes than did virgins. These results confirm the potential for male-derived nutrients to augment oocyte production, but indicate that mating is not required for oocyte maturation to occur.     

OVARIAN DEVELOPMENT AND OOSORPTION IN AUTOGENOUS FEMALES OF THE BLOWFLY,LUCILIA CUPRINA (WIED.)

Nearly 90% of nulliparous females of a laboratory selected autogenous strain of the sheep blowly, Lucilia cuprina, developed mature oocytes when fed only sucrose and water. The mean number of oocytes matured by those females which reached maturity was about 100. In the few females which did not reach maturity, ovarian development ceased early in vitellogenesis. Females had approximately 250 ovarioles, and when given ad libitum access to sheep liver, matured virtually all their primary oocytes. Flies given limited amounts of protein-rich material matured more oocytes than individuals given only sucrose and water; the apparent efficiency of conversion of ingested protein to ovary protein was of the order of 50%.

In females fed only sucrose and water or limited amounts of protein-rich material, the reduction in the number of oocytes resulted from oosorption initiated early in vitellogenesis. Oosorption was initiated earlier in females fed only sucrose and water, which were destined to resorb of the order of 150 oocytes, than in females which resorbed about 65 oocytes after having consumed a limited amount of protein-rich material.

Mating increased slightly both the proportion of females expressing autogeny and the number of oocytes matured.     

Ovary structure in a presocial insect,Elasmucha grisea (Heteroptera,Acanthosomatidae)

First generation egg clusters of Elasmucha grisea are more closely guarded than second generation clusters. The ovaries of this species are structured to enhance this behavior. The population of E. grisea from S-W Poland breeds in the spring (May–June) and late summer (July–August). The second generation clutches contain fewer eggs and are destroyed 3–4 days after oviposition by predators and parasitoids.The ovary structure in the studied species differs from that found in other Heteroptera. The average number of ovarioles per ovary is 24 while in the other investigated species the number of ovarioles per ovary is 6–7. Lateral oviducts are elongated and the ovarioles are arranged in a pennate pattern. Each ovariole contains only one growing ovarian follicle. Differentiation of the ovarioles and ovarian follicles is synchronised thus enabling simultaneous oviposition. A comparative analysis of the ovary structure during the life cycle, particularly the presence of atresive ovarian follicles in the ovarioles of egg- and nymph guarding females, as well as the shape and structure of the apical part of the tropharium all support the hypothesis of cooperation between females in E. grisea. A similar ovary structure has been observed in the Coccoidea (Hemiptera, Homoptera) which indicates presocial behavior.     

Morphology of the ovaries of Sphaerodema (Diplonychus) rusticum (Heteroptera,Belostomatidae)

The female reproductive system of Sphaerodema rusticum consists of a pair of ovaries, two lateral oviducts, a median common oviduct, and a median spermatheca. Accessory glands are absent. Each ovary has five free ovarioles branching from the oviduct. Each ovariole consists of a terminal filament, germarium, vitellarium, brown mass, and an exceptionally long pedicel. The terminal filament consists of a central core, interstitial cells, and an outer sheath. In the germarium, which consists of trophic and prefollicular regions, the trophic region or nurse cell chamber is divided into four histologically differentiated zones, distinguished as zones I–IV. Nutritive cords, originating from the posterior end of the trophic core in zone IV extend centrally and join the developing oocytes in the prefollicular chamber and the vitellarium. The compact prefollicular tissue at the base of the trophic core gives rise to prefollicular cells which, after encircling the young oocytes, become modified into follicular epithelial cells, the interfollicular plug, and epithelial plug. The young oocytes descend into the vitellarium and gradually develop into mature oocytes. A compound corpus luteum is observed simultaneously in all the ovarioles of both ovaries after ovulation. Below the epithelial plug there is an accumulation of material, the “brown mass,” which develops cyclically in correlation with the ovulation cycle. Each pedicel stores five mature chorionated eggs ready for oviposition. The epithelium of the anterior region of the pedicel secretes a PAS-positive material. General morphology and histology of the subdivisions of the ovarioles are described.     

Viability of Culex pipiens pipiens eggs affected by nutrition and aposymbiosis

Raisins were a better source of carbohydrate than sucrose for reproduction by autogenous Culex pipiens. A blood meal increased the number of eggs per raft from 49 autogenously to 114. Eggs of aposymbiotic females produced autogenously did not hatch, but 34% of the eggs were viable if the mosquitoes fed on chickens. With repeated blood meals the number of eggs per raft and the rate of embryonation and hatching declined in each successive gonotrophic cycle. In about $\text{1}\text{4}$ of the unhatched eggs of normal females there were no fully developed embryos, while many more of the unhatched eggs of aposymbiotic females contained no evidence of embryonic development. After the fifth blood meal, neither normal nor aposymbiotic insects oviposited. The ovaries of the nulliparous females contained approximately 10% of the potential number of mature terminal oocytes. Proximally in the ovarioles there were dilatations and coiled tracheoles indicating egg resorption. There were fewer parous follicles in aposymbiotic than in normal females. Larval rearing water, i.e., infusion in which larvae had been reared, was more attractive than fresh infusion for oviposition by normal, autogenous mosquitoes. The degree of embryonation of the eggs was lower and the hatching success rate was poorer in fresh infusion than in larval rearing water.     

RELATION BETWEEN OVARIAN MATURATION AND ACTIVITY OF THE CORPORA ALLATA IN SEASONAL FORMS OF THE BUTTERFLY, POLYGONIA C-AUREUM L.

In summer form adults of Polygonia c-aureum, the ovary develops soon after emergence and eggs mature a few days later. However, in autumn form adults, having been kept in laboratory conditions, only several mature eggs are found about four weeks after emergence. The allatectomy during the larval period prevents egg maturation in adults of both forms. When the corpora allata from the summer form of both sexes are transplanted into allatectomized adults of the autumn or summer form, the ovary develops as in the case of summer form adults. But the corpora allata of both sexes of the autumn form are not effective in inducing the ovarian maturation. Environmental factors, especially day-length and temperature during the larval period, may act through the neuroendocrine system to induce the activity of the corpora allata in the adult life.     

Acquisition of meiotic competence in the rat: Role of gonadotropin and estrogen

Oocytes were removed from the follicles of rats at 15 to 31 days of age, and their ability to resume meiosis (“meiotic competence”) in vitro was correlated with their diameter and the stage of follicular development. The majority of oocytes explanted on day 15 did not resume meiosis when placed in culture, but the percentage of competent oocytes increased from 14.1% ± 3.0% on day 20 to 67.6% ± 3.3% on day 26 of age. This ability to resume maturation correlated well (r = 0.98) with the increase in diameter of oocytes and coincided with the development of antral follicles. Hypophysectomy on day 15 of age, but not on day 20, reduced the percentage (P < 0.001) and number (P < 0.001) of competent oocytes and was accompanied by a reduction in diameter of oocytes. Treatment with PMSG or E₂ increased the number (P < 0.001) and percentage (P < 0.001) of competent oocytes. These results suggest that the ability of oocytes to mature in vitro is dependent upon stimulation by gonadotropins and that this action of gonadotropin may be mediated by production of estrogen within the follicles.     

Development and Fecundity of Reesimermis nielseni,a Nematode Parasite of Mosquitoes

Maturation of the mermithid nematode Reesimermis nielseni to the adult stage began by the tenth day after emergence of the nematodes from their hosts at ambient temperatures (24-27 C). Most postparasitic males and females reached the adult stage after 50 and 70 days, respectively. The first females exhibiting egg development and oviposition were observed 25-30 days after emergence, but some oviposition was still taking place 150 days later. Reesimermis nielseni laid an average 2,480 eggs per female over an 18-day oviposition period. A majority of the mature eggs hatched within 7 h after the cultures were flooded. The preparasites are short-lived, and only a few were able to infect exposed hosts after 72 h.     

Effects of sugar feeding on carbohydrate and lipid metabolism in a parasitoid wasp

Lifetime patterns of carbohydrate and lipid metabolism were compared in starved and sucrose‐fed adults of the parasitoid Macrocentrus grandii (Goidanich) (Hymenoptera: Braconidae). As expected, sucrose‐fed individuals lived longer than did starved individuals. Macrocentrus grandii males and females eclosed with levels of simple storage sugars (presumably primarily trehalose) and glycogen that were below maximum levels recorded from sucrose‐fed parasitoids. Both of these nutrients dropped to very low levels in starved individuals within 4 days post‐emergence and were maintained at high levels in sucrose‐fed individuals throughout their lives. Lipid reserves at emergence represented the highest lipid levels for both sexes in the two diet treatments, with levels declining over the lifetimes of males and females from both diet treatments. Our results therefore suggest that dietary sucrose is used to synthesize trehalose and glycogen, but not lipids in M. grandii. Also, in contrast to the patterns observed for the simple sugars and glycogen, lipid levels in starved individuals did not drop below levels observed in sugar‐fed individuals. The average number of mature eggs carried by females at emergence was 33 and increased to approximately 85 in sucrose‐fed and 130 in starved females by the age of 5 d in the absence of hosts. The egg maturation rate was therefore higher in starved than in sugar‐fed females. Potential explanations for this unexpected result are discussed.     

柑桔爆皮虫卵巢发育动态

本研究利用室内饲养成虫,对柑桔爆皮虫的蛹及正常取食和交配、正常取食但未交配以及正常交配但未取食三种处理的雌成虫的卵巢发育进行了系统观察。结果显示：该虫具有1对卵巢,每侧有5根卵巢管。前两种处理的雌虫卵巢管均能正常发育,成虫寿命在30天左右; 没有取食的雌虫寿命只有7天左右,在其卵巢管的生长区和成熟区均无卵形成。根据卵巢的形状、卵的产生过程、卵巢萼内有无卵粒以及卵黄沉积情况等将卵巢发育程度分为6个级别,即发育初期（0级）、卵黄沉积前期(Ⅰ级)、卵黄沉积期(Ⅱ级)、成熟待产期(Ⅲ级)、产卵盛期(Ⅳ级)和产卵末期(Ⅴ级)。每头雌虫最高怀卵量在140粒左右,根据雌虫怀卵量变化趋势,推测正常取食和交配的柑桔爆皮虫雌虫在出孔后10天左右开始产卵,产卵历期可达22天左右。据此提出该虫卵巢管发育到成熟待产期(Ⅲ级)之前（即羽化出孔后10天之内）为出孔成虫的防治适期。     

In vitro and in vivo maturation of oocytes from gonadotrophin-treated brushtail possums

The time course of nuclear maturation of oocytes was examined in brushtail possums, Trichosurus vulpecula. Oocytes were recovered from ovarian follicles > 2 mm in diameter after pregnant mares' serum gonadotrophin/porcine luteinizing hormone (PMSG/LH) treatment (in vivo matured) or 72 hr after PMSG treatment (in vitro matured). Oocytes recovered from small (< 2 mm) and large (> 2 mm) follicles were also assessed for their ability to mature in vitro. Staining with the DNA-specific dye Hoechst 33342 was used to assess the stage of nuclear development by fluorescence microscopy. The process of nuclear maturation progressed rapidly in vivo, as oocytes collected at 20-27 hr post-LH all had a GV, but by 28-29.5 hr post-LH approximately a third of eggs were MII. By 30-hr post-LH, more than 70% of oocytes had reached MII stage and all ovulated eggs were MII. In vitro, all oocytes were at germinal vesicle stage at the start of culture. After 24 hr of culture, 67% of oocytes had progressed to metaphase I/anaphase I of meiosis. After 36 hr, 25% of oocytes had completed maturation to metaphase II, increasing to 52% after 48 hr. Maturation of oocytes after 48 hr in culture was unaffected by the presence or absence of granulosa cells, PMSG or LH/porcine follicle stimulating hormone (FSH). More oocytes from large follicles (55%) completed maturation by 48 hr than from small follicles (15%). The potential of oocytes to mature after 48 hr in culture was dependent on the follicle harvested having reaching a critical diameter of 1.5 mm.