Arrest, resorption, or maturation of oöcytes in Aedes aegypti: dependence on the quantity of blood and the interval between blood meals

ABSTRACT. After emergence, the follicles of A. aegypti double in length and the oöcytes may deposit a small amount of yolk, but within 2 days growth is arrested. Renewed growth and vitellogenesis, as well as the number of eggs finally produced, depends on the quantity of blood ingested. All females, given either a small (1 μl) or large (4 μl) meal of rat blood by enema, began yolk deposition in a nearly equal number of oöcytes, and each oöcyte had about the same amount of yolk 8 h later. Within 48 h, females fed 4 μl had each produced more than 100 eggs, whereas females fed 1 μl either had continued yolk deposition in some oöcytes, while most degenerated, or had all re-entered oögenic arrest. Consequently, 48 h after the 1 μl meal, a female had either c. 50 or 0 eggs. Even by 14 h after a 1-μl meal, females were either committed to re-enter oögenic arrest or to complete maturation of some oöcytes and resorb the yolk of others. This was shown by removing and examining one ovary 14 h after a blood meal and then giving a second blood meal. The second meal stimulated meal maturation in the remaining ovary, but only in those females whose oöcytes had been in oögenic arrest when the first ovary was examined; the second meal had no effect on females whose first ovary had contained both vitellogenic and degenerating oöcytes. Oösorption was not reversed by a second blood meal. Our results do not support the hypothesis that the female 'evaluates' the ingested meal and begins vitellogenesis in an 'appropriate' number of oöcytes. The results demonstrate that the ovary is an unreliable indicator of the frequency of blood-feeding, when females take a small meal.     

Some observations on the histology of the ovary and RNA synthesis in the ovarian tissues of the starfish, Henrida sanguinolenta

The general histology of the ovary and the cellular morphology of oöcytes in Henricia sanguinolenta (Muller) Bell is described.
The single nucleolus in the germinal vesicle begins to multiply when the oöcyte is 90 μm in diameter, either by fragmentation or by budding and it reaches several hundred in number in a full grown oöcyte of 1200 μm in diameter. At no time during the oöcyte growth is RNA synthesis in the nucleolus or any other parts of the oöcyte detected by autoradiographic techniques. However, follicle cells and coelomocytes in the ovary are actively synthesizing RNA during this period.
The inactivity of RNA synthesis in oöcytes is discussed.     

Some observations on the development and cyclic changes of the oöcytes in a brooding starfish, Leptasterias hexactis

There are two ovaries in each arm and each ovary bears a single oviduct which opens orally at the interradial angle. The ovarian wall consists of three layers: mesothelium, muscular-connective tissue layer and germinal epithelium. The haemal space between the germinal epithelium and muscular-connective tissue layer is filled with a PAS positive fluid. It is suggested that this space may provide storage and transportation of nutrient to the germ cells.
The oögonium, situated along the germinal epithelium, is distinguished from the surrounding follicle cells by its clear cytoplasm and large nucleus with a single nucleolus. It measures 10 to 15 μ in diameter.
The development of primary oöcytes is divided into premeiotic, growth and germinal vesicle migration stages. The distribution of mitochondria seems to indicate the existence of a definite polarity in the young oöcytes; but this soon disappears at the beginning of vitellogenesis. Morphological evidence seems to suggest that some of the yolk granules may be synthesized first in follicle cells and then transferred into the oöcyte. Histochemical tests indicate that the yolk platelet is a carbohydrate-protein-lipid complex.
The first meiotic division occurs six hours after sperm penetration and the second meiotic division follows two hours later.
Monthly measurement of the oöcyte throughout a year indicates a well-defined annual spawning cycle; however, the growth of an oöcyte from an oögonium to a mature oöcyte requires about two years.     

Haemolymph vitellogenin,juvenile hormone,and oöcyte growth in the adult cockroach Nauphoeta cinerea during first pre-oviposition period

In the cockroach Nauphoeta cinerea the incorporation of a protein of low solubility into the oöcytes begins at day 5 of its adult life. An immunologically identical protein appears in the haemolymph two days earlier. The concentration of this protein, i.e. ‘vitellogenin’ in the haemolymph increases up to the onset of yolk incorporation into the oöcytes. During ovarian development no correlation could be detected between vitellogenin titre and several other parameters (ovary dry weight, length of the basal oöcytes, haemolymph protein concentration, body weight and age when ovulation occurred). In young females vitellogenin titre depends on the age, i.e. the volume of the corpora allata and hence on the presence and the titre of JH. During the period of egg maturation the total haemolymph protein concentration generally tends to drop while materials not precipitable by trichloracetic acid circulate at higher concentration after ecdysis and before ovulation.Early decapitation prevents vitellogenin synthesis and oöcyte growth, but when JH is applied to decapitated females, the normal vitellogenin titre is re-established, ovarian development, however, cannot be fully resumed. A dose-response curve shows that serial application of the hormone is much more effective than single large doses. Farnesylmethylester, a JH mimic, is about a hundred times less active, but more persistent than JH. Copulation seems to enhance the synthesis and release of endogenous JH, while food and water uptake are necessary to guarantee and optimal ovarian development. JH and high vitellogenin titre never restore ovarian development in females deprived of food and/or water or in those decapitated shortly after ecdysis.     

Activity of the corpora allata in the adult female migratory locust

Juvenile hormone was detected in the haemolymph of adult female Locusta by a modified Galleria bioassay. The hormone was present in the haemolymph immediately after the final ecdysis, but could not be detected after this time until the end of the period of somatic growth just before the start of ovarian development. During the first gonotrophic cycle the levels of juvenile hormone in the haemolymph could be related to the growth of the proximal oöcytes. The volumes of the corpora allata could be related to haemolymph juvenile hormone levels during the first gonotrophic cycle. Ovariectomy had no effect on haemolymph juvenile hormone levels or on the volumes of the corpora allata.     

Water balance during vitellogenesis by the American cockroach: Hydration of the oöcytes

The volume and water content of the terminal and penultimate oöcytes rise sharply during the last 2 days of the 6 day vitellogenic cycle. The ingestion of ³H₂O during each day of the cycle has been determined and the subsequent flux of radioactivity into and out of the haemolymph has been measured.It appears that water consumed during the first 2 days of the cycle contribute the most water to the oötheca. The flux of haemolymph water and its possible immediate storage is discussed in regard to oöcyte hydration.     

Oxygen consumption of engorged nymphs and unfed adults of Hyalomma asiaticum ticks (Acari: Ixodidae) exposed to various photoperiods

The oxygen consumption of engorged nymphs of Hyalomma asiaticum was measured at various intervals after drop-off from mice hosts. Duration of nymphal development to the emergence of adults was 25–32 days at 25°C. The oxygen consumption was high immediately after completing the blood meal (193–248 mm³ g^-1 h^-1 but decreased significantly 18 days later (at 25°C) to 45–65 mm³ g^-1 h^-1. It increased again before ecdysis (81–102 mm³ g^-1 h^-1, and also after ecdysis in freshly moulted adults (177–220 mm³ g^-1 h^-1. The oxygen consumption in 8-month-old adult ticks was very variable ranging from 40–42 to 172 mm³ g^-1 h^-1. Neither engorged nymphs nor unfed adult ticks showed any dependence of their respiratory metabolism on the photoperiodic regimes tested (LD 20:4 and LD 12:12, with or without transfer to an alternative photoperiod after engorgement of nymphs).     

The effect of temperature on the behaviour and development of Triatoma brasiliensis

Abstract. The effects of temperature on the development of early stages and the thermopreference of nymphs and adults were analysed in the haematophagous bug Triatoma brasiliensis Neiva, 1911 (Hemiptera, Reduviidae). Egg hatching, mortality of nymphs, feeding and moulting success of the early stages of T. brasiliensis were all affected by temperature. While high rates of egg hatching were observed between 25 and 27 °C, no hatching occurred at 12, 19 and 38 °C. The mortality of first‐instar nymphs was highest at 38 °C, at which no insects survived after 10 days of exposure. Feeding success was only affected at the lowest temperature (12 °C). No ecdysis was observed in the groups exposed to 12, 19 and 21 °C. Recently fed fourth‐instar nymphs preferred to stay at a temperature of approximately 30 °C. The preferred temperature began to decline gradually to approximately 27 °C during ecdysis, reaching 26 °C at 30 days after ecdysis. After a second blood meal, the insects' preferred temperature was again approximately 30 °C. The thermopreference pattern of females was similar to that of nymphs. Nymphs and females showed a daily fluctuation in their preferred temperature, moving towards higher values at the beginning of the dark phase, and choosing lower ones after this time interval, at which they remained until the end of the light phase. The females laid their eggs in all sectors of the arena, although the largest numbers of eggs were found between 28 and 32 °C.     

Simultaneous determination of molting and juvenile hormone titers of the greater wax moth

A simple and rapid extraction procedure was developed to determine simultaneously the molting hormone (MH) and juvenile hormone (JH) activity in a single insect tissue sample. From the onset of the last larval stage to adult eclosion of the greater wax moth, Galleria mellonella, three JH peaks were noted: at the time of the sixth larval ecdysis, 1 day before the seventh larval ecdysis, and at the time of adult eclosion. Three MH peaks were recorded for the male: at 1 day before the sixth larval ecdysis, 1 day before the seventh larval ecdysis, and 2 days after pupation. In the female, a fourth peak was shown at the time of adult eclosion. This fourth peak exhibits the highest molting hormone activity of all samples, 1600 Musca units/g of fresh tissue or an equivalent of 5.6 μg/g of ecdysterone. Eighty per cent of this MH accumulated in the ovary. The significance of MH and JH titers as related to the endocrine regulation of development is discussed in the light of this finding.     

BIOSYNTHESIS OF ECDYSONE IN THE ISOLATED ABDOMEN OF THE SILKWORM,BOMBYX MORI*

During pupal-adult development of the silkworm, Bombyx mori, the ecdysone titer changes, exhibiting two maxima in the females: one on the second day of pupal development and the other just before adult emergence. During the second maximum, ecdysone accumulates in the ovaries. It also accumulates in isolated abdomens, which were prepared just after pupal ecdysis and induced to initiate adult development by injection with β-ecdysone. Several lines of evidence suggest that ecdysone is synthesized in the ovary itself.     

Absence of insect juvenile hormones in the American dog tick,Dermacentor variabilis (Say) (Acari:Ixodidae), and in Ornithodoros parkeri Cooley (Acari:Argasidae)

Synganglia, salivary gland, midgut, ovary, fat body and muscle alone and in combination from the ixodid tick, Dermacentor variabilis (Say), or the argasid tick, Ornithodoros parkeri Cooley, were incubated in vitro in separate experiments with L-[methyl-(3)H]methionine and farnesoic acid or with [1-(14)C]acetate. Life stages examined in D. variabilis were 3 and 72 h old (after ecdysis) unfed nymphs, partially fed nymphs (18 and 72 h after attachment to the host), fully engorged nymphs (2 d after detachment from host), 3 and 72 h old (after eclosion) unfed females, partially fed unmated females (12-168 h after attachment to host) and mated replete females (2 d after detachment from the host). Those from O. parkeri were third and fourth stadium nymphs and female O. parkeri, 1-2 d after detachment. Corpora allata from Diploptera punctata, Periplaneta americana and Gromphadorina portentosa were used as positive controls in these experiments. No farnesol, methyl farnesoate, JH I, JH II, JH III, or JHIII bisepoxide was detected by radio HPLC from any tick analysis while JH III, methyl farnesoate, and farnesol were detected in the positive controls. To examine further for the presence of a tick, insect-juvenilizing agent, Galleria pupal-cuticle bioassays were conducted on lipid extracts from 10 and 15 d old eggs, unfed larvae (1-5 d after ecdysis), unfed nymphs (1-7 d after ecdysis), and partially fed, unmated female adults (completed slow feeding phase) of D. variabilis. Whole body extracts of fourth stadium D. punctata and JH III standard were used as positive controls. No juvenilizing activity in any of the tick extracts could be detected. Electron impact, gas chromatography-mass spectrometry of hemolymph extracts from fed, virgin (forcibly detached 7 d after attachment) and mated, replete (allowed to drop naturally) D. variabilis and fully engorged (1-2 d after detachment) O. parkeri females also failed to identify the common insect juvenile hormones. The same procedures were successful in the identification of JH III in hemolymph of fourth stadium D. punctata. Last stadium nymphal (female) O. parkeri implanted with synganglia from second nymphal instars underwent normal eclosion to the adult. The above studies in toto suggest that D. variabilis and O. parkeri do not have the ability to make the common insect juvenile hormones, and these juvenile hormones do not regulate tick metamorphosis or reproduction as hypothesized in the literature.     

Protein synthesis in the fat body of Leucophaea maderae during vitellogenesis

During the early stages of vitellogenesis in Leucophaea, vitellogenin accounted for most if not all of the secreted protein synthesized by the fat body. Synthesis began about 5 days after mating and continued until 24 hr or so before the formation of the oötheca. Ligation resulted in the degeneration of the oöcytes, the first evidence of which was seen within 24 hr. Ligation also curtailed the synthesis of vitellogenin at about the same time. Isolated abdomens treated with an analog of juvenile hormone commenced vitellogenesis within 12 to 24 hr and measureable oöcyte growth occurred after 5 days. Despite continued synthesis of vitellogenin, the oöcytes in isolated abdomens always degenerated.     

Influence of a juvenile hormone analogue on vitellogenin synthesis and oögenesis in larvae of Nauphoeta cinerea

In experiments on the synthesis of the vitellogenic protein, farnesylmethylester, a juvenile hormone (JH) analogue, was injected into female Nauphoeta cinerea larvae at various stages during their development. Two and 4 days after injection, 2 μl of haemolymph were assayed in a vitellogenin immunodiffusion test. In second last and last instar larvae less than 6 days before adult ecdysis, high doses (100 μg) of farnesylmethylester are necessary to induce vitellogenin synthesis, whereas older last stage larvae and decapitated adults respond to small doses (1 μg) with the synthesis of vitellogenin. It seems that the competence to synthesize the vitellogenic protein changes at the time of induction of the moulting process. If farnesylmethylester is injected into last instar larvae with a supposedly high titre of ecdysone, the vitellogenic protein can be detected in the haemolymph of a small percentage of animals only.Oöcyte maturation can be observed in last instar larvae injected after the fifth to ninth day with farnesylmethylester. The observed volume changes of the corpora allata suggest that an absence of JH for a short time is necessary for the oöcytes to become competent to grow. Last instar larvae treated with farnesylmethylester become larval-adult intermediates with partly developed oöcytes, demonstrating a simultaneous juvenilizing and gonadotropic influence of the JH analogue. In last instar larvae injected with farnesylmethylester a partial degeneration of already maturing oöcytes is induced at the time when the ecdysone titre is supposedly high and the possible reasons for this are discussed.     

高温对稻褐飞虱发育与生殖的影响

通过高温处理及交配产卵实验,探讨了高温对稻褐飞虱Nilaparvata lugens (Stal)发育与生殖的影响。研究了不同高温条件对褐飞虱若虫发育历期、产卵量、产卵前期、寿命等生物学特性的影响。34℃以上高温导致褐飞虱若虫发育历期延长。高温处理4龄若虫使羽化后的雌成虫产卵量减少。高温处理不同日龄雌成虫也致使其产卵量减少,其中以1日龄短翅型、3日龄长翅型的产卵量影响最大。高温处理后褐飞虱寿命缩短。高温恒温处理,对短翅型雌成虫的产卵前期影响不大,但能延长长翅型雌成虫的产卵前期;而高温变温处理致使短、长翅型雌成虫的产卵前期均延长。高温变温对褐飞虱生殖的影响程度大于高温恒温。高温处理组雌、雄成虫与对照组相应的成虫交配试验表明,高温对雌性的影响大于雄性。实验初步确定34℃为对褐飞虱发育与生殖产生影响的临界温度。     

Sporogonic development of Hepatozoon americanum (Apicomplexa) in its definitive host, Amblyomma maculatum (Acarina)

Light microscopic observations of the sporogonic development of Hepatozoon americanum are described in its acarine host, Amblyomma maculatum. Laboratory-reared nymphal ticks were fed on 2 dogs infected with H. americanum. Nymphal ticks were sampled daily, starting 3 days after being placed on a parasitemic dog, until 18 days after infestation (PI), and then every 3 or 4 days until replete nymphs molted. Ticks were examined as unstained wet mounts and hematoxylin-eosin-stained paraffin sections. Gametes were found within the gut cells of nymphs 4 and 6 days PI. Although differentiation of gamonts into gametes was not detected, syngamy and sporogony were observed. Sporogony appears to occur wholly within tick gut cells, followed by release of mature oocysts into the hemocoel. The earliest evidence of sporoblast formation was observed 23 days PI and of sporozoite formation, 10 days later. Mature oocysts were first found 42 days PI in newly molted adult ticks. Most adult ticks (>98%) that were dissected contained mature oocysts. Oocysts were multisporocystic, and sporocysts contained a variable number of sporozoites. Oocysts in various stages of development were often seen within the same tick, and the number of mature oocysts ranged from 4 to 573.     

Effects of starvation and feeding upon corpus allatum activity and oöcyte growth in adult female Periplaneta americana

Direct radiochemical determinations of juvenile hormone (JH) biosynthesis by corpora allata (CA) isolated from starved and re-fed Periplanteta americana have been employed to elucidate the humoral mechanisms involved in the modulation of reproductive activity in response to food availability. When starvation was initiated in mature adult females at the time of formation of an oötheca the next oötheca was normally deposited 5 to 6 days later, a delay of 2–3 days, and a third oötheca was formed by only 50% of starved females. The terminal oöcytes in the remaining females were either resorbed or maintained in an arrested state. Ovarian development had effectively ceased after 2 weeks of starvation but recommenced within 3 days of re-feeding. The CA of most starved females exhibited 2 activity cycles following food withdrawal. The first peak occurred on day 1 of the starvation period and was coincident with the timing for fed controls. The second peak was delayed by about 2 days and the activity of the CA then declined to the extent that glands from animals starved for more than 11 days were completely inactive. Feeding, after 10 or 16 days starvation, resulted in a resumption of CA activity which was detectable in some animals within 24 hr, and very high rates of JH biosynthesis were found 4 or 5 days later. The results suggest that P. americana can readily and efficiently modulate egg production in response to food supply, and that control is effected through alterations in JH production by the CA. The use of farnesenic acid as a biochemical probe indicates that CA inactivity after long periods of starvation does not arise because malnutrition has caused complete metabolic shut-down in the glands, and that JH biosynthesis is basically modulated at a control point prior to the last two enzymic stages in the pathway.     

The effect of relative humidity on the behaviour and development of Triatoma brasiliensis

Abstract The preference for relative humidity (RH) and suitability of different levels of this environmental parameter were investigated in the haematophagous bug Triatoma brasiliensis Neiva, 1911 (Hemiptera, Reduviidae). The hygropreference of T. brasiliensis was studied using a RH gradient and the effect of different RHs on the egg hatching, nymph mortality and moulting success was also analysed. The results show that egg hatching in first-instar nymphs of T. brasiliensis was lower at extreme RHs and, particularly, it was lowest at 9.3% RH. The survival of starved nymphs was not affected by RH, but the percentage of engorged nymphs and the ecdysis success of these nymphs once fed was diminished strongly by high humidity. Fourth-instar nymphs preferred to stay at the lowest RH during the first 5 days after feeding and during ecdysis. This preference changed markedly during starvation. Fifteen days after ecdysis, the bugs moved towards intermediate humidities, and 30 days after ecdysis they even preferred the most humid sectors of the gradient. Females preferred to lay eggs in dry environments, suggesting that they may not have a particular hygropreference for oviposition, but that they simply lay their eggs at the RHs where they prefer to stay.     

A fine structural survey of the development of the adult fat body of Leptinotarsa decemlineata

The fat body of a female Colorado potato beetle, Leptinotarsa decemlineata, at adult ecdysis, contains a large number of protein granules which are composed of light and dark zones. Part of the light zone in some of these granules is believed to be urate. During the first two days after adult ecdysis, fat body development is not essentially different in females reared either under long- or short-day conditions. Protein granules and large vacuoles disappear and the first cell organelles are regenerated. The effect of the photoperiod on the histological structure of the fat is expressed after these events. In females reared under long-day conditions, the fat body becomes specialized for vitellogenin synthesis. Under short-day conditions, the fat body stores massive amounts of lipid until day 6 after adult ecdysis. Then the first electron-dense protein granules develop near the nucleus, and on day 10 the first autophagic vacuoles are seen. These structure changes are discussed in connection with the known biochemical properties of the adult faty body of Leptinotarsa.     

PREDATION OF THE LADYBEETLE CHILOCORUS KUWANAE ON THE SCALE UNASPIS YANONENSIS

Abstract The prey consumption of ovipositing female adults of the ladybeetle Chilocorus kuwanae on the scale Unaspis yanonensis was found to be significantly greater than that of the male adults. At 25°C one female adult ladybeetle, on average, would consume 42. 7 female scale adult per day while one male adult only destroyed 22. 3 female scale adults. However, after a deprivation of the prey for 48 h, this difference was eliminated. A C. kuwanae female adult had to prey on at least 15 U. vanonensis female adults in order to lay eggs. The funcional responses of the beetle adults to densities of different stages of the scale followed Holling's type 1. The functional responses to female scale adults indicated that the maximum prey consumption went up with the increase in temperature from 16°C to 35°C, and dropped sharply at 37°C. However, temperature did not alter the type of the functional response. Rased on the predation of C. kuwanae adults on U. yanonensis female adults, the minimum critical, optimal and maximum critical temperatures for their attack were estimated to be 10. 6°C, 31. 5°C and 38. 2°C respectively. The increase in predation space or in predator density could result in a reduction in the attack rat-e, but with the increase of predator density, the effect of predation space became much smaller. C. kuwanae adults preferred male pupae to other stages of the scale, and their preference for various stages of the prey was in the order of male pupae, 2nd-instar male nymphs, 2nd-instar female nymphs, adult females and kinstar nymphs.