Effects of precocene and methoprene application in young adult Musca autumnalis

Abstract Observations were made on the relative rates of growth among corpora allata, ovarian follicles and fat bodies in diapausing and reproductive Musca autumnalis DeGeer. Rates of corpora allata growth were greater in long-day than in short-day animals. Topically applied precocene II reduced the size of the corpora allata. Two sequential doses of precocene inhibited vitellogenesis. Topically applied methoprene produced vitellogenesis in short-day flies and inhibited development of hypertrophied fat body. This work provides evidence that Juvenile Hormone is the primary agent controlling diapause and non-diapause (vitellogenic) development in the ovaries of face flies.     

Precocenes as pro-allatocidins in adult female Diploptera punctata: A functional and ultrastructural study

Adult mated females of the viviparous cockroach Diploptera punctata are moderately sensitive to precocenes. Oöcyte growth is inhibited and oviposition is delayed in insects topically treated with precocene II or precocene III. C₁₆ juvenile hormone release by corpora allata of precocene-treated insects is markedly inhibited when compared to corpora allata of acetone-treated controls. Electron microscopy of the corpora allata reveals that precocene treatment results in a disorganisation of the intracellular organelles. Topically applied precocene II reaches a high concentration in the haemolymph (0.5 mM 2 hr after topical application of 250 μg). C₁₆ juvenile hormone release by isolated corpora allata is inhibited by precocenes in vitro; half-maximal inhibition over a 3 hr period is obtained at 0.4 mM precocene II. In vitro inhibition of corpora allata by precocene II concentrations higher than 1 mM rapidly destroys the glands as evidenced by electron microscopy (total disintegration of cellular organelles) and by the virtual cessation of C₁₆ juvenile hormone synthesis by the corpora allata. Inhibition of C₁₆ juvenile hormone release by precocene is time-dependent and is not reversible over the short-term incubation in vitro. This inhibition does not appear to be related to the spontaneous activity of the glands in vitro, and it can be reduced by two epoxidase inhibitors. Precocenes are pro-allatocidins in this species: they are bioactivated within the corpora allata to cytotoxic epoxides.     

Antigonadotropic and antiallatal effects of precocene II in the firebrat, Thermobia domestica (Thysanura,Lepismatidae)

The sensitivity of an apterygote insect to precocene II was investigated for the first time in females of Thermobia domestica. Topical applications of this compound, which has been said to possess anti-juvenile hormone activity, were carried out at various times in the postecdysial period of a reproductive cycle, during intense vitellogenesis in the terminal oöcytes. The effects of treatment were observed on mortality, fecundity, insemination and also on the ultrastructure of corpora allata; they depend on the dose used and on the day of treatment. A single application of 10 μg/insect at the beginning of the postecdysial period induces antigonadotropic effects in females reared both with and without males. The effects of precocene add to those of non-insemination, which also elicits inhibition of oöcyte maturation. In addition, the cytotoxic action of precocene, leading to degeneration of the corpora allata, which is most probably irreversible, was demonstrated.     

Physiological correlates to courtship, mating, ovarian development and maternal behaviour in the ring-legged earwig

Abstract. The involvement of the endocrine system in courtship, mating, maternal behaviour and the gonadotrophic cycle was studied in the earwig, Euborellia annulipes, after application of JH III and, alternatively, precocene II. Topical application of 35 or 122 μg of JH III to newly eclosed females advanced the onset of courtship behaviour from 6.6 ± 1.3 days in acetone-treated controls to 1.4 ± 2.8 and 0.5 ± 2.5 days, respectively. Application of 6 μg of JH III had no effect on the onset of courtship behaviour. Applications of Juvenile Hormone had no significant effect on the age at first mating nor on the duration of mating, though the trend is towards advanced onset. The age at first oviposition was advanced by hormone treatment; clutch size and the proportion of offspring hatching was reduced by hormone treatment. The interclutch interval, size and proportion hatching of the second clutch were not affected by hormone treatment. Topical application of 50 μg of JH III to females on the day of oviposition shortened the total duration of maternal care from 15.4 ± 0.5 to 5.3 ± 1.7 days; whereas in acetone-treated and precocene II-treated groups maternal care lasted 16.1 ± 1.9 and 13.8 ± 1.6 days, respectively. The duration of maternal care was positively correlated with number of offspring hatching and fledging. In a corollary experiment, topical application of JH III significantly enhanced the onset of the second gonadotrophic cycle as assessed by basal follicle length; application of 20 μg of precocene II, either singly or in repeated doses, did not delay growth of basal follicles. Finally, repeated application of as much as 80 μg of precocene II had no effect on basal follicle length, nor on ovary wet weights. These results are consistent with the hypothesis that intermediate to high titres of JH are associated with oocyte growth, mating, and the cessation of maternal care; low titres of JH appear to be associated with the period of maternal behaviour and slow ovarian follicle development.     

Effects of ovariectomy and mating on the activity of the corpora allata in adult female Blattella germanica (L.) (Dictyoptera: Blattellidae)

In adult female cockroaches, the ovary greatly affects the synthesis of Juvenile Hormone (JH) by the corpora allata, and in females of some cockroach species, removal of the ovaries results in a permanent depression of JH synthesis. We report that the corpora allata in ovariectomised, adult virgins of the German cockroach, Blattella germanica (L.), increase and then decrease in activity, as they do in intact females. Moreover, the distal tubules in the left colleterial glands of ovariectomised females accumulate abundant protein, the production of which is regulated by JH. In both ovariectomised and sham‐operated females, the activity of the corpora allata more than tripled between days 1 and 4 of adulthood, during which the oöcytes of sham‐operated females grew considerably in length. The corpora allata of sham‐operated females produced even more JH on day 7, but very little on day 10, by which time all females had oviposited. The glands of ovariectomised females, by constrast, produced a similar amount of JH on day 7 as on day 4, but much less on day 10. Beginning on day 13, the activity of the corpora allata increased again in ovariectomised females, an increase that did not occur until day 22 in sham‐operated females. Mating of ovariectomised females on day 6 resulted in a significant increase in the activity of the corpora allata by day 10. We conclude that both the ovary and mating stimulate the synthesis of JH early in the reproductive cycle, but that neither is needed for the occurrence of a complete cycle of JH synthesis.     

Endocrine regulation of female contact sex pheromone production in the German cockroach, Blattella germanica

ABSTRACT The amount of the major component of the cuticular sex pheromone, 3, 11-dimethyl-2-nonacosanone, on individual female German cockroaches, Blattella germanica (L.), as a function of age was determined by gas-liquid-chromatographic analysis. Accumulation of phermone increased with age in both virgin and mated females. During the first gono-trophic cycle, the pheromone accumulated most rapidly when oocyte growth rates were maximal (days 5–10), and least rapidly while the female carried an ootheca (days 11–32). Pheromone accumulation was similar in virgin and mated females when the same physiological stages (determined by oocyte maturation) were considered. Inhibition of Juvenile Hormone release, through allatectomy, chemicals (precocene or fluoromevalonate), or through mechanical egg case implants, suppressed or delayed pheromone production and oocyte growth. The Juvenile Hormone analogue ZR512 induced allatectomized or head-ligated females and females with chemically or mechanically inhibited corpora allata to produce pheromone and enlarge their basal oocytes. Finally, ZR512 applied to intact females stimulated pheromone production in a dose-dependent manner.     

The effects of juvenile hormone, 20-hydroxyecdysone and precocene II on activity of corpora allata and the mode of negative-feedback regulation of these glands in the adult Colorado potato beetle

When the titre of juvenile hormone III in female Leptinotarsa decemlineata was elevated by the implantation of supernumerary corpora allata or by the injection of the hormone, the rate of endogenous hormone production by the host glands was significantly restrained, as determined by the short-term in vitro radiochemical assay. From denervation studies, it is suggested that during phases of elevated juvenile hormone titre, the corpus allatum activity is regulated via humoral as well as neural factors requiring intact nerve connections. Restrainment of gland activity appears to be mainly via the neural pathway. Isolated corpora allata were not influenced by 10^?5 M juvenile hormone III added to the incubation medium in vitro.Studies with farnesenic acid revealed that the final two enzymatic steps in the biosynthetic pathway of juvenile hormone are also diminished during prolonged neural inhibition of the corpora allata.20-Hydroxyecdysone and precocene II had no apparent effect on the corpus allatum activity of Leptinotarsa decemlineata.     

Precocene-induced sterility in F1 generation of Glossina morsitans morsitans

Precocene treatment does not disrupt the events of reproduction in Glossina morsitans morsitans or induce any apparent changes in treated tsetse. However, some females of the F₁ generation are either sterile or show retardations in follicle development. Sterility is not reversed spontaneously or with juvenile hormone analogues. The critical period for precocene action is related to each ovulation. The corpora allata of precocene-treated tsetse are normal, but those of F₁ sterile females are degenerate. The occurrence of retardation has enabled the characterisation of stages in follicle development in G. m. morsitans.     

Identification and action of juvenile hormone III from sexually mature alate females of the red imported fire ant,Solenopsis invicta

Analysis of extracts of hemolymph obtained from sexually mature alate females of Solenopsis invicta from monogyne colonies resulted in identification of juvenile hormone III (JH III). The average amount of JH III was 0.32±0.04 pmol/μmolof hemolymph. Topical application of 0.038 pmol of JH III was sufficient to stimulate alates to shed their wings in the presence of the queen. The time in which alates were induced to dealate decreased linearly with increasing concentrations of JH III from 0.038 to 3.8 pmol. However, higher JH III concentrations deviated from linearity and did not reach dealation times comparable with those that occur after mating flights. Thus, it appears that the mechanism of dealation that occurs when female alates are out of the influence of their queen is different from the one associated with mating flights. Application of 0.42 μmol of precocene II inhibited dealation of alates in queenless colonies. However, this inhibition was reversed after applying 38 pmol JH III to precocene-treated alates. The sizes of corpora allata (CA) from sexuals treated with JH III did not differ from those of controls. However, the sizes of CA were reduced in alates treated with precocene II. The results indicated that JH was important to dealation.     

A Juvenile Hormone analogue enhances homosexual behaviour in female‐deprived males of the migratory locust

In laboratory colonies of crowded migratory locusts Locusta migratoria (L.), homosexual behaviour (i.e. males mounting other males) is commonly observed. Female‐deprived males of Locusta migratoria migratorioides R. & F. mount each other in a characteristic mating position, often forming a group of several insects. When allatectomized males are placed together with intact, female‐deprived males, the former are usually mounted by the latter, demonstrating some degree of control involving the corpora allata over homosexual behaviour. This may be related to the positive effects of Juvenile Hormone (JH) or Juvenile Hormone analogues (JHAs) in enhancing male sexual behaviour, as is shown in some other insects. In the present study, a potent JHA (i.e. pyriproxyfen) is injected into a group of young, crowded L. m. migratorioides males, and an equivalent group of control males is maintained in a separate cage. Both groups are deprived of females. Three times a week, during 2‐h observation periods, JHA‐injected and control males are placed together in the absence of females, and homosexual mountings, per group and per individual, are recorded every 10 min. Observations are performed for 10 weeks. Analysis of these data, including the time spent in mounting behaviour, the percentage of individuals within a group involved in the behaviour during the observation periods and the identity of both partners, reveals that the JHA‐treated males show a more intense homosexual mating behaviour than control males in all quantified parameters. This is the first report of the enhancement of homosexual behaviour by an endocrine factor in insects.     

Re-evaluation of the role of corpora cardiaca in calling and oviposition behaviour of giant silk moths

Re-investigation of the role of the corpora cardiaca in the reproductive behaviour of the giant silkmoths, Hyalophora cecropia and Antheraea polyphemus, showed that this pair of glands plays no essential role, either in “calling” behaviour by virgin females or in increased oviposition due to mating. Removal of corpora cardiaca-corpora allata complexes, either from diapausing pupae or from freshly eclosed adult females, had no effect on the calling behaviour or on its timing in either species. Moreover after mating, these operated females laid eggs in the typical mated oviposition pattern. Furthermore, females in which there was only a nervous connection between the brain and the abdomen but no haemolymph circulation called normally and oviposited after mating.Although the corpora cardiaca were not essential for calling behaviour, hormogenates of corpora cardiaca-corpora allata complexes and blood from calling or ovipositing females induced a typical “calling” response in 30–60% of the isolated virgin H. cecropia abdomens tested. This activity was not species-specific as it was also found in Manduca sexta, but the restriction of major activity to corpora cardiaca extracts and haemolymph suggested that a neurosecretory factor may modulate the normal neural control of calling behaviour.     

Primer effect of queen pheromone on juvenile hormone biosynthesis in adult worker honey bees

Juvenile hormone synthesis in adult worker honey bees was measured by an in vitro corpora allata bioassay. Adult queenless workers exhibit higher rates of juvenile hormone biosynthesis than queenright workers. Hormone synthesis is not correlated with the volume of the glands. Extract of queen mandibular glands, applied to a dummy, reduces juvenile hormone biosynthesis in caged queenless workers to the level of queenright workers. The same result was obtained with synthetic (E)-9-oxo-2-decenoic acid, the principal component of the queen mandibular gland secretion. This pheromonal primer effect may function as a key regulating element in maintaining eusocial colony homeostasis. The presence of brood does not affect the hormone production of the corpora allata.Abbreviations BSA bovine serum albumin - CA Corpora allata - JH juvenile hormone - 9-ODA (E)-9-oxo-2-decnoic acid     

Effects of precocene I and II on flight behaviour in Oncopeltus fasciatus, the migratory milkweed bug

Treatment of newly emerged adult Oncopeltus fasciatus with the corpus allatum inhibitors. 7-methoxy-2,2-dimethyl chromene or 6,7-dimethoxy-2,2-dimethyl chromene (preocene I and II) results in an inhibition of long-term flight (presumed migratory) behaviour in both males and females and inhibition of oögenesis in females. Treatment of reproductive females with precocene briefly stimulates flight behaviour (which ceases in such females as oviposition begins) and then subsequently inhibits it. Oviposition also ceases in such females and oöcyte resorption occurs. Topical application or injections of JH III to precocenetreated animals results in immediate restoration of the tendency to make long tethered flights while corpora cardiaca extract injections, corpora cardiaca implantation, sham implantation, sham injections and sham topical applications were ineffective in restoring prolonged flight behaviour to precocene-treated animals.Restoration of flight by JH III injection was observed within 1 hr after treatment with the hormone. These results indicate that JH is necessary for prolonged flight and presumably migratory behaviour in this species and its stimulatory effect on flight behaviour is immediate. Possible mechanisms of action of the hormone on flight behaviour are discussed.     

Precocene sensitivity of corpora allata in adult female Locusta migratoria after electrocoagulation of the pars intercerebralis neurosecretory cells

Destruction, by electrocoagulation, of the median neurosecretory cells of the pars intercerebralis of 2-day old adult female Locusta migratoria completely suppressed normal juvenile hormone-biosynthetic activity of the corpora allata in most animals. For example, 6 days after electrocoagulation the rates of spontaneous juvenile hormone biosynthesis, measured by radiochemical assay of freshly isolated glands, showed a median value of less than $\text{1}\text{100}$ that of the corresponding sham operated controls, which were then in mid-vitellogenesis. Injection of graded doses (200–1600 μg) of precocene I at this time, followed by assays five days later, resulted in a similar decline of both corpus allatum volume and precocene epoxidase activity (measured by radiochemical assays of precocene I dihydrodiol formation in vitro) in pars intercerebralis-coagulated and sham-operated animals, when expressed as a percentage of their own zero precocene controls. Electrocoagulation of the pars intercerebralis largely prevented the normal increase in both corpus allatum volume and its epoxidase activity, so that by age 13 days these parameters were about 2.5-fold lower in coagulated vs control (sham operated) animals. In fact, electrocoagulation had no marked effect on the value of epoxidase activity per unit corpus allatum volume. It is concluded that the corpora allata from this species and stage are sensitive to precocene irrespective of whether they are active in biosynthesis of juvenile hormone.     

A pharmacological and endocrinological study of female insemination inPhormia regina (Diptera: Calliphoridae)

Injections of octopamine, dopamine, and the octopaminergic agonists, clonidine and naphazoline, into the thoracic hemocoel enhanced female insemination in sugar-fed (sexually unreceptive)Phormia regina. Topical applications of the juvenile hormone (JH) analogue, methoprene, also enhanced female insemination in sugar-fed (sexually unreceptive)P. regina. Since JH plays a role in receptivity in protein-fed females, it was originally hypothesized that one agonist, clonidine, enhanced female insemination by acting on the corpus allatum (CA) to increase JH biosynthesis. Two or three doses of the antiallatal agent, precocene II, prior to administration of clonidine, did not inhibit clonidine-enhanced female insemination. Removal of the corpus allatum also did not have a significant effect on clonidine-enhanced female insemination. Measurement of juvenile hormone (JH) biosynthesis/release in corpora allata, which were removed at 1, 3, 5, and 7 h postinjection, revealed that clonidine does not affect JH biosynthesis/release. Our study reveals a possible role for the biogenic amines in female insemination in insects. We suggest that the octopaminergic agonist, clonidine, acts downstream from the corpus allatum on the regulatory mechanisms involved in female insemination.     

Control of C-16 juvenile hormone biosynthesis in active corpora allata of female African locusts

Summary

Corpora allata from 8-day-old female Locusta migratoria, during the phase of yolk deposition, exhibit high rates of C-16 juvenile hormone (JH) biosynthesis. The effect of different potential factors which may be involved in the regulation of corpora allata activity is reported. The biosynthetic activity of corpora allata was determined by radiochemical assay.

In maturing females, no changes in corpora allata activity are detected during one daily cycle. Starvation reduces JH biosynthesis only 3 days after the beginning of the food deprivation. Suppression of the median neurosecretory material by electrocoagulation of the internal cardiaca tract (TCC-I) does not disturb JH biosynthesis whereas the transection of the allata I nerve fibres (NCA-I) or the electrocoagulation of the lateral neurosecretory pericarya results in a rapid decline of JH biosynthesis. These data indicate that the median and lateral allatotropins are different, and that only the lateral neurosecretory material exerts an allatostimulating action on corpora allata at the time of vitellogenesis. The corpora allata response to the median allatotropin changes during oocyte growth. C-16 JH and/or 20-hydroxyecdysone treatments in vitro (addition in the culture medium) and in vivo (injection in female) do not influence JH production in our experimental conditions.     

Ovarian sequestration of [14C]-inulin by an insect: An index of vitellogenesis

[¹⁴C]-Inulin injected into the blood of female milkweed bugs (Oncopeltus fasciatus) undergoing vitellogenesis is sequestered in the eggs. Determination of ovarian radiocarbon uptake gives a reproducible index of the progression of vitellogenesis that permits quantitative measurements prior to oviposition or under conditions where vitellogenesis is incomplete. This assay allows intra- and interspecific comparisons of the rates of juvenile hormone biosynthesis by corpora allata (CA) when these endocrine glands are transplanted into milkweed bug females, whose CA have been chemically destroyed with precocene. The method has the potential of distinguishing between nervous and hormonal regulation of the CA.     

Responsiveness of the adult cricket (Gryllus bimaculatus andAcheta domesticus) retrocerebral complex to allatostatin-1 from a cockroach,Diploptera punctata

Brain-retrocerebral complexes of female crickets,Gryllus bimaculatus andAcheta domesticus, treated with antibody to allatostatin-1 from a cockroach,Diploptera punctata, show extensive immunoreactivity. The results suggest that allatostatins or allatostatin-like molecules are produced in neurosecretory cells of the brain and are delivered to the corpora allata through nervous connections and/or via haemolymph. Radiochemical measurements of juvenile hormone III biosynthesis by isolated corpora cardiaca-corpora allata complexes from adultG. bimaculatus have been used to demonstrate an in vitro sensitivity of these glands to allatostatin-1 fromD. punctata. Allatostatin-1 is a relatively potent inhibitor of juvenile hormone III biosynthesis in corpora allata of both young adult females and males. In glands taken from 3-day virgin females, 50% inhibition of hormone biosynthesis is reached at ca. 3 nmol·l^-1 allatostatin-1. The inhibitory action of allatostatin-1 is rapid, dose-dependent and reversible. Addition of 200 mol·l^-1 farnesol to the incubation medium prevents inhibition of juvenile hormone III biosynthesis by allatostatin-1. Juvenile hormone III biosynthesis by isolated corpora allata of 3-day female house crickets,A. domesticus, is also susceptible to inhibition by 1 mol·l^-1 allatostatin-1.Abbreviations ASB2 Diploptera punctata allatostatin-5 - CA corpora allata - CC corpora cardiaca - Dip A-1 Diploptera punctata allatostatin-1 - HEPES 4-(2-hydroxyethyl)piperazine-1-ethanesulphonic acid - JH juvenile hormone(s) - Mas-AS Manduca sexta allatostatin - MF methyl farnesoate - NCA nervus corporis allati - NCC nervus corporis cardiaci - SEM standard error of mean - TRIS Tris(hydroxymethyl)aminomethane     

Function of the neuroendocrine complex in diapausing Pyrrhocoris apterus females

The role of the brain in inhibiting the action of corpora allata in diapausing short-day females was investigated by transplantation experiments. The function of the transplanted glands was evaluated by oviposition. Active glands from long-day females remained active for a long period of time after transplantation into short-day females, although in situ corpora allata were inhibited shortly after the transfer of females from long to short day. Moreover, inactive glands from short-day females became active after transplantation into other short-day females. In contrast, corpora allata remained inhibited when transplanted together with the brain in the neuroendocrine complex (brain-corpora cardiaca-corpus allatum) where the nervous connections between the brain and corpus allatum remained intact. It is therefore suggested that short-day conditions inhibit corpora allata via nervous connections with the brain.     

Precocious metamorphosis of the aphid Myzus persicae induced by the precocene analogue 6-methoxy-7-ethoxy-2,2-dimethylchromene

For up to three days after being treated with the precocene analogue 6-methoxy-7-ethoxy-2,2-dimethylchromene, adult green peach aphids (Myzus persicae) gave birth to offspring (alate and apterous virginoparae, males) which underwent precocious metamorphosis. Only a few precocious gynoparae and no precocious oviparae were recorded. The precocious aphids became adultoid in the third or fourth-instar as a result of corpus allatum destruction. They were able to develop mature embryos, but could not deposit them because of incomplete differentiation of the reproductive tract. The treatment did not induce the production of alate virginoparae in the experimental clone of Myzus persicae. However, a few males were born late in the reproductive sequence of treated apterae. The corpora allata of the treated adults appeared on histological examination to be unaffected by precocene.