Competence of Macrotermes michaelseni (Isoptera: Macrotermitinae) larvae to differentiate into soldiers under the influence of juvenile hormone analogue (ZR-515, methoprene)

It has been shown that only third instar larvae of Macrotermes michaelseni have the competence to differentiate into presoldiers under the influence of juvenile hormone analogue (JHA). The timing of events leading to presoldier formation was independent of JHA dose above the threshold. Further studies with homogeneous groups of third instar larvae of different ages showed that only larvae of a certain age (0–6 days) could respond to topically applied JHA to produce presoldiers and intercastes (intermediate forms). Older larvae did not respond, hence, 0–6 days interval is the competence period for presoldier differentiation in this species. It seems also that the corpora allata of those individuals which differentiate into presoldiers become activated during the competence period, possibly by the parents or other means.     

In vivo stimulation of vitellogenesis in Aedes aegypti with juvenile hormone,juvenile hormone analogue (ZR 515) and 20-hydroxyecdysone

Decapitated blood-fed Aedes aegypti mosquitoes do not undergo normal oöcyte maturation. Topical application of 1.25 ng JH analogue (ZR 515) or 250 ng JH-I restored ovarian development in 70–80% of the treated females. The rate of vitellogenin synthesis in these animals was 80% of normal blood-fed controls.When ligated abdomens were treated, 125 pg ZR 515 or 12.5 ng JH-I were sufficient to restore ovarian development in 80% of the animals. The rate of vitellogenin synthesis in these animals was 70% of normal blood-fed controls. On the other hand, injection of 1.25 μg 20-hydroxyecdysone was needed to restore ovarian development and vitellogenin synthesis in decapitated and abdominally ligated females.These experiments indicate that JH concentrations closer to the physiological norm than 20-hydroxyecdysone, can restore ovarian development and vitellogenin synthesis in vivo.     

Morphogenetic effects of juvenile hormone and juvenile hormone mimics on adult development of Drosophila

The morphogenetic effects of t,t-farnesol, Law-Williams juvenile hormone analogue, dichlorofarnesenic acid ethyl ester (DFAEE), and a syntetic racemic or isomeric mixture of C₁₈ juvenile hormone (JH), when applied topically to pharate pupae and adults of D. melanogaster have been studied. Of these various agents tested, only DFAEE and JH affected adult development and eclosion and the pharate pupae were the most sensitive to these agents. The racemic mixture of JH induced the secretion, in the abdomen, of a supernumerary cuticle indistinguishable from that of the pupa; it, in addition, retarded the synthesis of brown eye pigments, general body pigmentation, and affected the differentiation of various internal organs and cuticular structures of the abdomen. By comparing the effects of JH with those of Minute (M) and bobbed (bb) mutations on the adult development, it is suggested that JH, by retarding genetic translation mimics M or bb.     

Mutagenicity testing of the juvenoid methoprene (ZR-515) by means of the Drosophila wing spot test

The juvenile hormone analogue methoprene, which is used in insect pest control, was subjected to mutagenicity testing by means of the Drosophila wing spot test. Larvae heterozygous for recessive wing trichome mutations were exposed to a sublethal dose of methoprene. Wings of emerged adult females were inspected for the presence of phenotypically mutant mosaic spots. Methoprene exhibited a weak mutagenic effect. The fact that only small mosaic clones were induced is discussed.     

Effects of juvenile hormone analogue treatment in adult females of the ovoviviparous cockroach,Blaptica dubia (Dictyoptera,Blaberidae)

Adult females of the ovoviviparous Argentinian cockroach, Blaptica dubia, were repeatedly treated with either 100?μg methoprene or 100?μg pyriproxyfen in 5?μL acetone either during the first vitellogenic cycle or during the period of gestation. Treatment during the first vitellogenic cycle (days 2–20 of adult life) did not inhibit vitellogenesis and oocyte growth, but prevented the formation of an ootheca. This was accompanied with a significant reduction of the titer of juvenile hormone (JH) III and an increased amount of ecdysone (E) and 20-hydroxyecdysone (20E) in the haemolymph of the animals. Treatment of adult females during the period of gestation (days 30–70) resulted in a complete degradation and resorption of the ootheca and induced another vitellogenic cycle. Again, this was associated with a decrease in haemolymph JH III titer, but an increase in the concentrations of free ecdysteroids.     

Tissue-specific effects of the juvenile hormone analogue ZR 515 during metamorphosis in Drosophila cell cultures

The juvenile hormone analogue ZR 515 has specific effects on ecdysone-induced metamorphic differentation of Drosophila cells cultured in vitro. The number of vesicles containing imaginal cuticular structures is reduced to 10% of control levels. Similarly, the differentiation of adult fat body is partly inhibited by ZR 515. The differentiation of adult tubular and fibrillar muscles, however, is not affected. ZR 515 does not inhibit cuticle secretion by tracheal cells and larval epidermal cells.     

Effects of dopamine on juvenile hormone metabolism and fitness in Drosophila virilis

The effects of dopamine (DA) on juvenile hormone (JH) metabolism and fitness (estimated as fecundity and viability levels under heat stress (38 °C)) in Drosophila virilis have been studied. An increase of DA level obtained by feeding with DA reduced fitness of wild-type (wt) flies under stress, and decreased JH degradation in young wt females while increasing it in sexually mature wt females. A decrease in DA levels resulted from 3-iodo-tyrosine treatment and caused a decrease in JH degradation in sexually mature wt and heat sensitive (hs) mutant females (DA level in hs females is twice as high in wt females). A dramatic decrease in viability under stress and fecundity under normal conditions in wt, but not hs, females was observed. 3-iodo-tyrosine treatment also reduced the number of oocytes at stages 8-14, delayed oocyte transition to stage 10 and resulted in the accumulation of mature eggs in wt females. It delayed maturation of wt, but not hs, males as well, but did not affect their fertility. This advances our understanding of the regulation of JH metabolism by DA in Drosophila and suggests a crucial role for the basal DA level in fitness.     

Vitellogenin induced in adult male Diploptera punctata by juvenile hormone and juvenile hormone analogue: Identification and quantitative aspects

The effect of the juvenile hormone analogue hydroprene on the appearance in the haemolymph of the yolk-protein precursor vitellogenin in male Diploptera punctata has been assessed using rocket immuno-electrophoresis. Vitellogenin was induced in a dose-dependent fashion, with a minimum dose of 10 μg hydroprene required for its appearance. Implantation of male corpora allata into male and female hosts also resulted in the appearance of vitellogenin in the haemolymph of the hosts, with females showing apparent greater sensitivity to the implantation.The identity of vitellogenin in male haemolymph was further confirmed using Ouchterlony double immunodiffusion and SDS polyacrylamide gel electrophoresis of immunoprecipitates. The electrophoretic pattern of immunoprecipitated haemolymph from females and hydroprene-treated males was similar, further confirming that the immunoprecipitable product was in fact vitellogenin.     

Effects of juvenile hormone analogue on ecdysis prevention induced by precocene in Rhodnius prolixus (Hemiptera:Reduviidae)

Precocene II, added to the meal of fourth-instar larvae of Rhodnius prolixus (25 micrograms/ml of blood), induced an increase in the duration of the molting cycle. This effect was related to the decrease of both the nuclear area of the prothoracic gland cells and the mitotic activity in epidermal cells. Juvenile hormone analogue applied topically (60 micrograms/insect) together with Precocene II treatment avoided atrophy of the prothoracic glands and induced a higher number of epidermal mitosis accelerating the time of subsequent ecdysis. A possible relationship between juvenile hormone and production of ecdysone is discussed.     

Effects of the juvenile hormone analogue methoprene and dietary protein on male melon fly Bactrocera cucurbitae (Diptera: Tephritidae) mating success

The effect of access to dietary protein (P) and the topical application of a juvenile hormone analogue (methoprene (M)) on mating behaviour of male melon fly Bactrocera cucurbitae was assessed in the laboratory and in field cages. Age, dietary protein and methoprene application increased the mating success and influenced the mating behaviour. Treatment with methoprene (M+) to protein-deprived (P−) males had only a modest effect on the acceleration of sexual maturity, but application of methoprene (M+) to protein-fed (P+) males greatly accelerated sexual maturity. Protein diet (P+) increased mating success of males in comparison to protein-deprived (P−) males. Protein and methoprene have a synergistic effect on mating behaviour, since M + P+ treated males exhibit reduced mating latency and achieved higher mating in younger ages than methoprene and/or protein-deprived males. Copulation duration was correlated with nutritional status and M + P+ males copulated longer at the age of advanced sexual maturity than M − P+ males. Our results suggest that in this species with a lek mating system, females discriminate between the males based on their sexual signals, which were influenced by protein in the adult diet, methoprene application and age. The results are discussed in the light of mating competitiveness of precocious treated young males and their relevance to Sterile Insect Technique application against this pest species.     

In vitro induced pinocytotic activity by a juvenile hormone analogue in oocytes of Drosophila melanogaster

Summary Pinocytotic activity has been analyzed in Drosophila oocytes following either in vivo or in vitro exposure to horseradish peroxidase. The enzyme tracer gains access to the yolk spheres only when supplied to the oocyte in vivo. In oocytes cultured in vitro, peroxidase remains restricted to the residual coated vesicles and to the tubular profiles formed in excess in the cortical ooplasm.In an attempt to induce peroxidase uptake by oocytes cultured in vitro, various incubations were tested. Among these, hemolymph from both sexes is capable of promoting peroxidase uptake up to a level comparable to that detectable in vivo. On the other hand, fat body extracts fail to promote such cellular activity. Finally, the juvenile hormone analogue ZR-515 is shown to be the only factor required to promote pinocytotic activity under the experimental conditions tested. The observations are interpreted to indicate that vitellogenin has no inductive role on pinocytosis but simply acts by adhering to the forming coated vesicles which in turn are produced by the oolemma in response to the action of juvenile hormone.     

Effects of a juvenile hormone analogue, pyriproxyfen, on the apterous form of soybean aphid (Aphis glycines)

The soybean aphid, Aphis glycines Matsamura, is an eastern Asian soybean [Glycine max (L.) Merr.] pest which can reduce soybean yield. We determined the effects of pyriproxyfen, a juvenile hormone analogue, on development, mortality, longevity and fecundity of A. glycines under laboratory conditions. Distance Insect Growth Regulator, containing ∼11.2% pyriproxyfen, was applied at two concentrations, 50 and 150 mg/l, to first and fourth instar nymphs. When first or fourth instar A. glycines were treated with pyriproxyfen, some nymphs became supernumerary‐molted nymphs with 1–3 extra molts or were sterilized. Mortality of treated first instar nymphs was >68% greater than the control group and longevity was reduced by >40%. The higher concentration of pyriproxyfen reduced fecundity of first instar nymphs when they reached adulthood by ∼79%. Pyriproxyfen similarly affected fourth instar nymphs. Mortality of treated fourth instar nymphs was ≥15% greater than the control group and longevity was reduced by >24%. Both concentrations of pyriproxyfen lowered the fecundity of fourth instar nymphs by >27%. Pyriproxyfen also had other sublethal effects on fourth instar nymphs which became apparent when they molted to adulthood. In a few instances they developed wing pads and many produced dead, deformed or abnormal neonates that lacked appendages.     

Effects of juvenile hormone on the ecdysone response of Drosophila Kc cells

Drosophila Kc cells are ecdysone-responsive: hormone treatment leads rapidly to increased synthesis of several ecdysone-inducible polypeptides (EIPs) and to commitment to eventual proliferative arrest. Later, the treated cells undergo morphological transformation, cease to proliferate, and develop new enzymatic activities, notably, acetylcholinesterase (AChE) activity. These responses have proven useful as models for studying ecdysone action. Here we report the sensitivity of Kc cells to another important insect developmental regulator--juvenile hormone (JH). We find that JH inhibits some, but not all, aspects of the ecdysone response. When Kc cells are treated with ecdysone in the presence of either natural JHs or synthetic analogues, the morphological and proliferative responses are inhibited and AChE induction is blocked. Most striking is that JHs protect the cells from the rapid proliferative commitment induced by ecdysone alone. The JH effects exhibit reasonable dose-response curves with half-maximal responses occurring at very low JH concentrations. Nonetheless, even at high JH concentrations the inhibitory effects are incomplete. It is interesting that EIP induction appears to be refractory to JH. It seems clear that JH is not simply a generalized inhibitor of ecdysone-induced responses.     

Effects of a juvenile hormone analogue on honey bee foraging behaviour and alarm pheromone production

Worker honey bees treated with 250 μg of the juvenile hormone analogue methoprene shifted from the broodnest to the food storage region prematurely and displayed precocious foraging behaviour. Treatments with 25 and 2.5 μg caused slight but non-significant effects. Methoprene did not influence individual foraging performance as measured by mean number of foraging trips/h, mean amount of time spent foraging/h or mean duration of the total foraging period. Methoprene also induced premature production of two alarm pheromones, 2-heptanone and isopentyl acetate. These results support the hypothesis that juvenile hormone regulates temporal division of labour in the honey bee colony.     

Effects of three compounds with anti-juvenile hormone activity and a juvenile hormone analogue on endogenous juvenile hormone levels in the tobacco hornworm, Manduca sexta

The ability of three anti-juvenile hormones and one juvenile hormone analogue to reduce in vivo juvenile hormone levels in Manduca sexta has been investigated. Two compounds. FMev (tetrahydro-4-fluoromethyl-4-hydroxy-2H-pyran-2-one) and ETB (ethyl-4-[2-(tert-butylcarbonyloxy)butoxy]-benzoate) reduced the titres of juvenile hormones I and II to near the levels of detection in topically treated larvae. Precocene III (7-ethoxy-6-methoxy-2,2-dimethylchromene) was inactive but the juvenile hormone analogue hydroprene was as effective as the two anti-juvenile hormones in reducing endogenous juvenile hormone titres in larvae. FMev was also shown to reduce the level of juvenile hormones II and III in pharate adults.     

Evidence for a juvenile hormone receptor involved in protein synthesis in Drosophila melanogaster

The larval fat body of newly eclosed adults of Drosophila melanogaster was found to contain a single major binding protein specific for juvenile hormone (JH). Binding to this protein was saturable, of high affinity, and specific for JH III. The protein has a subunit molecular weight (Mr) of 85,000, as determined by photoaffinity labeling. The same or similar JH-binding protein was found in larval fat body and cuticle of third instar larvae and in male accessory glands and heads of newly eclosed adults. It was not found in several other tissues in adults. Male accessory gland cytosol from wild-type flies was found to contain a single binder with a dissociation constant (KD) of 6.7 nM for JH III; a binder in similar preparations from the methoprene-tolerant (Met) mutant had a KD value 6-fold higher. JH III stimulated protein synthesis in glands cultured in vitro, but this effect was reduced in Met flies as compared to wild-type flies, establishing a correlation between JH binding and biological activity of the hormone. In addition, glandular protein accumulation during the first 2 days of adult development was less in Met flies than in wild-type flies. These results strongly suggest that the binding protein we have identified mediates this JH effect in male accessory glands and thus is acting as a JH receptor.