Effect of KK-42 on growth,development, molting,and metamorphosis of the european corn borer,Ostrinia nubilalis (Hübner)

KK-42 (1-benzyl-5-[(E)-2,6-dimethyl-1,5-heptadienyl]imidazole), administered by feeding, delayed the growth and development of nondiapause-bound and diapause-bound Ostrinia nubilalis larvae and increased the length of the instar. At doses of 80–240 ppm, 62–100% of nondiapause-bound fourth instars precociously pupated or remained as fourth instars, while 52–100% of diapause-bound fourth instars did not molt to the fifth instar. Injection of these nondiapause- and diapause-bound KK-42-fed fourth instars with ecdysone elicited a molt and resulted in the production of larval-pupal intermediates. When mature fourth instar controls were similarly injected, they molted into normal fifth instars. These results support the view that KK-42 delays/inhibits ecdysteroid production. Both eupyrene and apyrene spermiogenesis were prematurely initiated in nondiapause-bound fourth instars that were fed on medium containing 160 ppm KK-42. Fenoxycarb, a potent juvenile hormone mimic, rescued nondiapause-bound fourth instars from precocious pupation. All fenoxycarbtreated larvae either molted to the fifth instar or remained as fourth instars and eventually died. These results support the view that treatment with KK-42 inhibits JH production. When KK-42 treatment was begun in the third instar, a considerable number of nondiapause-bound and some diapause-bound third instars precociously molted to the fifth instar. There was a correlation between weight and the incidence of precocious molting in that third instars destined to skip the fourth instar attained a weight, as pharate fifth instars, of two to three times more than pharate fourth instar controls. Similarly, fourth instars that were destined to undergo precocious pupation attained a weight, as pharate pupae, that was approximately two times more than pharate fifth instar controls. More potent analogues of KK-42 may prove useful in controlling populations of 0. nubilalis by interfering with their growth, development, and metamorphosis. © 1995 Witey-Liss, Inc.

1 This article is a US Government work and, as such, is, in the public domain in the United States of America.

     

Inhibitory Action of an Imidazole Compound on Ecdysone Synthesis in Prothoracic Glands of the Silkworm, Bombyx mori

The precocious pupation was induced either by allatectomy at the time of third ecdysis or by topical application of an imidazole compound (KK-42; 1-benzyl-5-[( E )-2, 6-dimethyl-1, 5-heptadienyl] imidazole) to the fourth (penultimate) instar larvae of the silkworm, Bombyx mori. However, the critical period for KK-42 treatment in induction of precocious pupation was longer than that for allatectomy. The effects of KK-42 depended on the doses applied and a half-maximum dose was estimated to be approx. 10 μg/larva. KK-42 suppressed the increase in hemolymph ecdysteroid titres leading to larval ecdysis in controls. Ecdysteroid levels remained at low levels for about 6 days after the treatment, followed by an increase toward precocious pupation. When the prothoracic glands from the mature fifth instar larvac were incubated in vitro in Grace's medium containing various concentrations of KK-42, secretion of ecdysone into the medium was suppressed depending upon the doses of KK-42 added and a half-inhibition concentration was estimated to be approx. 1 nM. Thus, KK-42 was shown to be an inhibitory agent to ecdysteroid secretion in silkworm larvae.     

Analysis of precocious metamorphosis induced by application of an imidazole derivative to early third instar larvae of the silkworm,Bombyx mori

When an imidazole derivative (KK-42) was applied to day 1 third instar larvae of the silkworm, Bombyx mori, 100% underwent precocious metamorphosis at the end of the fourth instar. Thus, the fourth instar becomes the last instar in these KK-42–treated larvae. The endocrine systems underlying the precocious metamorphosis were analyzed in the present study. Hydroprene application during the prolonged third instar after KK-42 treatment can prevent precocious metamorphosis, and the results showed dose-dependent and stage-specific effects. From analysis of the developmental changes in ecdysteroid levels in both KK-42–treated larvae and KK-42– and hydroprene-treated larvae, we conclude that changes in JH levels during the third larval instar can modify the secretion pattern of prothoracic glands and that during the next larval instar, very low ecdysteroid levels during the early stages of the presumptive last (fourth) larval instar are directly related to precocious metamorphosis. Arch. Insect Biochem. Physiol. 36:349–361, 1997. © 1997 Wiley-Liss, Inc.     

Upregulation of the immune protein gene hemolin in the epidermis during the wandering larval stage of the Indian meal moth, Plodia interpunctella

Expression of hemolin, which generates an immune protein, was up-regulated in wandering fifth instar larval stage of Plodia interpunctella. The mRNA level peaked in the middle of the wandering stage. Major expression was in the epidermis, rather than in the fat body or gut. To test a possible ecdysteroid effect on hemolin induction we treated with RH-5992, an ecdysteroid agonist, and KK-42, which inhibits ecdysteroid biosynthesis in both feeding and wandering fifth instar larvae. When feeding larvae were treated with RH-5992 the hemolin mRNA level was increased. When wandering larvae were treated with KK-42 its level was reduced. In addition, when KK-42-treated larvae were subsequently treated with RH-5992 the hemolin mRNA level was recovered. These results strongly suggest that ecdysteroid up-regulates the expression of hemolin mRNA. Hormonal and bacterial effects on hemolin induction were further analyzed at the tissue level. Major induction of hemolin mRNA was detected following both RH-5992 treatment and bacterial injection in the epidermis of both feeding and wandering larvae. Minor induction of hemolin was detected in the fat body following a bacterial injection, but not RH-5992 treatment. We infer that in P. interpunctella larvae, the epidermis is the major tissue for hemolin induction in na?ve insects and in insects manipulated with bacterial and hormonal treatments.     

Controlled ecdysteroid accumulation in eggs of the silkworm,Bombyx mori,by an imidazole compound (KK-42), and embryogenesis in these eggs

An imidazole compound (KK-42), a potent inhibitor of ecdysone synthesis, was applied to the female pharate adult of the silkworm, Bombyx mori, to control ecdysteroid accumulation in developing ovaries and mature eggs. KK-42 applied on day 2 or later completely suppressed an increase in ecdysteroid content in developing ovaries. The inhibitory action of KK-42 was restricted to vitellogenic follicles, i.e., those in which active ecdysteroid synthesis is occurring. Ecdysteroid content in the mature eggs of moths remained at the level accumulated in ovaries before KK-42 application. Thus, KK-42 was shown to be a novel agent to suppress the ecdysteroid accumulation in eggs. Eggs containing different amounts of ecdysteroids showed different levels of embryonic development. About 80% of the eggs which contained less than 10 ng free ecdysteroids/g eggs were not fertilized. More than 80% of the eggs containing less than 40 ng/g eggs of free ecdysteroids initiated embryogenesis but failed to hatch. Larvae hatched from almost all eggs which accumulated free ecdysteroids of more than 150 ng/g. Thus, maternal ecdysteroids appear to be required at different titers for fertilization, embryogenesis, and hatching of the silkworm larvae. © 1994 Wiley-Liss, Inc.     

A Role for Ecdysteroids in the Induction and Maintenance of the Pharate First Instar Diapause of the Gypsy Moth,Lymantria dispar

Several lines of evidence suggest a novel regulatory mechanism for diapause regulation in the gypsy moth. We propose that ecdysteroids play a role in the induction and maintenance of the pharate first instar larval diapause in this species. A 55 kDa gut protein that is indicative of diapause is expressed in intact and neck-ligated pharate larvae but is not expressed when a ligature is placed posterior to the prothorax, site of the prothoracic gland. Guts cultured in vitro for 12 h cease to synthesize the 55 kDa protein, but synthesis of the protein resumes if the culture medium is enriched with a prothorax extract from pharate larvae or a prothoracic gland extract from fifth instar larvae. Injection of 20-hydroxyecdysone or the ecdysteroid agonist, RH-5992, into isolated abdomens stimulates synthesis of the diapause-specific 55 kDa protein, suggesting that the essential factor from the prothorax is an ecdysteroid. KK-42, an imidazole derivative known to inhibit ecdysteroid biosynthesis, averts diapause when applied to prediapausing pharate first instar larvae, but this effect can be countered by application of 20-hydroxyecdysone or RH-5992, i.e. KK-42 treated pharate larvae that are exposed to an ecdysteroid or RH-5992 readily enter diapause. A chilling period (120 days at 5 degrees C) is normally adequate to prompt an immediate termination of diapause when pharate larvae are transferred to 25 degrees C, but if such larvae are held in hanging drop cultures with ecdysteroids they fail to terminate diapause. Together, these results suggest that ecdysteroids are essential for the induction and maintenance of diapause and imply that a drop in the ecdysteroid titer is essential for diapause termination. Copyright 1997 Elsevier Science Ltd. All rights reserved     

Effects of an imidazole derivative (KK-42) on development and ecdysteroid production in Locusta migratoria (Insecta, Orthoptera)

The imidazole derivative KK-42 was applied in various experimental conditions to larvae and adult females of Locusta migratoria. The effect of this compound was monitored on the development of larvae, on oocyte growth in adult females and on the development of eggs laid by these females. KK-42 had only minor effects on postembryonic development; anticipation of imaginal moult was never observed. In contrast oocyte and egg development were markedly affected by KK-42: this effect is however not related to modifications of the synthesis of ecdysteroids in the ovaries.     

Induction of non-diapause eggs in Bombyx mori by a trehalase inhibitor

The effect of validoxylamine A (VAA), a potent and specific trehalase inhibitor, on the induction of non-diapause in Bombyx mori was examined. The VAA induced non-diapause eggs and prevented the glucogen accumulation in the eggs. Trehalase activity of the pupal ovary was effectively inhibited by the VAA injection.     

3S-(+)-3,7-Dimethyl-1,5-Octadiene-3,7-Diol and Ionone Derivatives from Tea

1-Isobutyl-5-(4-phenoxyphenyl)imidazole (KK-98), an inhibitor of juvenile hormone (JH) biosynthesis in the cockroach, and related imidazole compounds were evaluated against silkworm, Bombyx mori, for their activity to induce precocious metamorphosis. KK-98 induced precocious metamorphosis in the 4th instar larvae at high doses. Replacement of the 4-phenoxy group by a 3-phenoxy or 3-benzyloxy group on the benzene ring increased the activity. Among this series of compounds, 5-(3-benzyloxyphenyl)-1-isopropylimidazole (8) showed the highest activity. The induction of precocious metamorphosis by compound 8 was rescued by the simultaneous application of methoprene, a JH minie. When newly molted 3rd instar larvae were treated with a high dose of compound 8, a few larvae formed larval-pupal intermediates in the 3rd instar stage, which has not been formed by treating of any other imidazoles so far.     

Functional response of Chrysoperla carnea (Neuroptera: Chrysopidae) to Helicoverpa armigera (Lepidoptera: Noctuidae): Effect of prey and predator stages

Abstract Understanding predator–prey interactions has a pivotal role in biological control programs. This study evaluated the functional response of three larval instars of the green lacewing, Chrysoperla carnea (Stephens), preying upon eggs and first instar larvae of the cotton bollworm, Helicoverpa armigera Hübner. The first and second instar larvae of C. carnea exhibited type II functional responses against both prey stages. However, the third instar larvae of C. carnea showed a type II functional response to the first instar larvae of H. armigera, but a type III functional response to the eggs. For the first instar larvae of C. carnea, the attack rate on H. armigera eggs was significantly higher than that on the larvae, whereas the attack rate of the second instar C. carnea on H. armigera larvae was significantly higher than that on the eggs. For the third instar larvae of C. carnea, the attack rate on the larvae was 1.015 ± 0.278/h, and the attack coefficient on the eggs was 0.036 ± 0.005. The handling times of the third instar larvae on larvae and eggs were 0.087 ± 0.009 and 0.071 ± 0.001 h, respectively. The highest predation rate was found for the third instar larvae of C. carnea on H. armigera eggs. Results of this study revealed that the larvae of C. carnea, especially the third instar, had a good predation potential in controlling H. armigera eggs and larvae. However, for a comprehensive estimation of the bio‐control abilities of C. carnea toward H. armigera, further field‐based studies are needed.     

Activity of gut alkaline phosphatase,proteases and esterase in relation to diapause of pharate first instar larvae of the gypsy moth,Lymantria dispar

Two distinctly different patterns of gut enzyme activity were noted in relation to diapause in pharate first instar larvae of the gypsy moth, Lymantria dispar. Trypsin, chymotrypsin, elastase, aminopeptidase and esterase activities were low at the initiation of diapause and through the period of chilling needed to terminate diapause. At the completion of a 150 day chilling period, activity of each of these enzymes quickly increased when the pharate larvae were transferred to 25°C. By contrast, activity of alkaline phosphatase (ALP) increased rapidly at the onset of diapause, remained elevated throughout diapause, increased again during postdiapause, and then dropped at the time of hatching. In addition, zymogram patterns of ALP activity differed qualitatively in relation to diapause: several bands were detectable during the pre- and postdiapause periods, but only one band, a band of high mobility, was visible during diapause. The ALP isozyme present in diapausing pharate larvae had a pH optimum of 10.6. Diapause in the gypsy moth can be averted by application of an imidazole derivative, KK-42, and pharate larvae treated with KK-42 showed elevated protease and esterase activity, low ALP activity, and expressed ALP isozymes with low mobility. Thus the overall patterns of gut enzyme activity and the ALP zymogram in KK-42 treated individuals were similar to those observed in untreated individuals at the termination of diapause. Our results suggest a unique pattern of enzyme activity in the gut that is regulated by the diapause program. Arch. Insect Biochem. Physiol. 37:197–205, 1998. © 1998 Wiley-Liss, Inc.     

Effects of the parasitization of a braconid, Apanteles, on the blood of its host, Pieris

Parasitization of a braconid wasp, Apanteles glomeratus, of larvae of a common cabbage butterfly, Pieris rapae crucivora, caused changes in differential haemocyte count (DHC), total haemocyte count (THC), and encapsulative capacity against dead eggs of Apanteles in the fourth and fifth instar host larvae.However, no correlation could be found between the number of Apanteles eggs deposited and THC of the middle fourth instar host larvae or between the number of parasitoid larvae and specific gravity of the haemolymph from the late fifth instar host larvae.From the changes in DHC and in THC of both non-parasitized and parasitized Pieris larvae, an increase in the number of plasmatocytes of non-parasitized Pieris larvae in the early fourth instar period was supposed to be due to transformation of prohaemocytes into plasmatocytes, and a low population of plasmatocytes of parasitized larvae in the comparable period was assumed to be due to a suppression of transformation of prohaemocytes by some factor released from the parasitoid eggs.Failure of the parasitized fourth instar Pieris larvae to encapsulate injected dead eggs of Apanteles indicated that the parasitoid embryos were, in some way, actively inhibiting the encapsulation reactions of the host.The increase in THC of the parasitized fifth instar larvae could not be ascribed to a decrease in the volume of host haemolymph. Rather it could be interpreted by a suppression of adhesive capacity of haemocytes in the host haemocoel to tissue surfaces.Reduced encapsulative capacity of the parasitized fifth instar larvae might be attributed either to a depression of the adhesive activity of plasmatocytes resulting from a depletion of energy source for haemocytes in the host haemolymph by parasitization, or from an active suppression of adhesiveness of the plasmatocytes by secretions from ‘giant cells’ (teratocytes) originated from the parasitoid.     

Desensitization of fifth instar Spodoptera litura to azadirachtin and neem

The deterrence of azadirachtin, in its pure form and as a constituent of neem seed extract, to fifth instar Spodoptera litura (Fab.) larvae, was measured using cabbage, Brassica oleraceae (L.) var. capitata, leaf disc assays. Paired-choice assays, in which larvae could choose between feeding on a treated (1.3 ng azadirachtin per square cm leaf area) or an untreated leaf disc for 2 h, were conducted at 24 h intervals throughout the fifth instar. In addition, no-choice assays, in which larvae could feed on only one leaf disc (10 ng azadirachtin per square cm leaf area) for 1.5 h, were conducted consecutively over a six hour period at the beginning of the fifth instar. The effects of hunger and habituation on desensitization in our no-choice tests were partitioned. After repeated exposures, larvae became desensitized to pure azadirachtinal in both choice and no-choice tests, but did not desensitize to neem containing the same absolute amount of azadirachtin in choice tests. Hunger was responsible for approximately one third of the desensitization response in the no-choice tests. Sensitivity to azadirachtin was independent of age within the fifth instar.     

F污染桑叶对家蚕繁殖力的影响

对不同抗Ｆ性蚕品种的幼虫短期添食梯度浓度ＮａＦ研究Ｆ对桑蚕生殖的影响,结果表明,只要个体能正常羽化产卵,Ｆ对怀卵数、产卵数、产卵率和孵化率都无明显影响,低浓度的Ｆ对强抗Ｆ性品种蚕的生殖似有促进作用;但５龄期添食高浓度的Ｆ可引起怀卵数、产卵数和孵化率下降;Ｆ主要港集在马氏管、中肠等组织中,蚕卵中Ｆ的含量极低     

In vivo and in vitro photoperiodic induction of diapause using isolated brain-suboesophageal ganglion complexes of the silkworm,Bombyx mori

By use of a bivoltine silkworm race which shows a long-day photoperiodic response after induction during the last (5th) instar, we tried to programme photoperiodic induction in the isolated brain-suboesophageal ganglion complex in vivo and in vitro. A pair of the complexes from a newly ecdysed 5th-instar female was transplanted into the abdomen of a late 5th-instar larva and exposed to long-day (20 h light: 4 h dark) or short-day (8 h light: 16 h dark) conditions for 3 cycles. The short-day-exposed complexes elicited the production of diapause eggs in the recipient silkworms destined to become non-diapause egg producers, whereas the long-day-exposed brain complexes produced non-diapause eggs. Transplant experiments of the brain-suboesophageal ganglion complex using isolated abdomens showed a similar result. The brain complexes from newly ecdysed females of the 5th-instar were cultured in Grace's insect medium under 20 h light: 4 h dark or 8 h light: 16 h dark for 4 cycles, respectively. After in vitro culture, a pair of complexes was implanted into the abdomen of a late 5th-instar larva destined to become a non-diapause egg producer, and the diapause incidence in the resultant moths was examined. The brain complexes which received the short-day cycles induced a large portion of diapause eggs, whereas those which received the long-day conditions induced non-diapause eggs. The connection of corpora cardiaca and corpora allata with the brain complex had no influence on the result. Suboesophageal ganglia which had been cultured in vitro and implanted elicited a remarkable production of diapause eggs, but cultured brains were ineffective in producing diapause eggs, regardless of the photoperiod experienced. These results demonstrate that photoperiodic induction of the silkworm can be programmed in in vivo and in vitro culture systems, and that components of the photoperiodic clock (photoreceptor, clock, and counter system) are located in the brain-suboesophageal ganglion complex, possibly in the brain itself.     

Corazonin reduces the spinning rate in the silkworm,Bombyx mori

The insect neuropeptide, [Arg⁷]-corazonin was injected into larvae of the silkworm, Bombyx mori to investigate its influence on development and behavior. A single injection of 50 pmol of corazonin into the fourth and fifth instar larvae induced prolongation of the spinning period in all experimental groups except for those injected on day 10 of the fifth instar. The injection also caused a prolongation of the pupal period in some experimental groups, while it had no effect on the timing of larval ecdysis and the length of feeding period of the fifth instar. The spinning period was significantly prolonged even at a low dose of 1 pmol. Both the spinning rate and the rate of increase in hemolymph ecdysteroid level during the spinning stage were reduced by injection of corazonin. However, corazonin injection during days 5-7 of the fifth instar reduced the spinning rate without influencing the ecdysteroid level until the end of day 8, thereafter the rate of increase in hemolymph ecdysteroid level was slower in the corazonin-injected larvae than in the control larvae. Therefore, the suppressed ecdysteroid level observed in the corazonin-injected larvae appears to be a result rather than a cause of the reduced spinning rate. This study is the first published report for the corazonin effect on the behavior in insects.     

Teratocytes of the solitary endoparasitoid Meteorus gyrator (Hymenoptera: Braconidae): morphology, numbers and possible functions

Abstract. Laboratory studies investigated the development of teratocytes derived from the eggs of the parasitoid Meteous gyrator (Thun.) in its host, the tomato moth Lacanobia oleracea (L.). At hatching, each parasitoid egg produced an average of approximately 1000 teratocytes, but this number declined to approximately 400 during the course of parasitism. The teratocytes increased in size markedly, such that 7 days after egg hatch their mean diameter was approximately four times that of the cells immediately after dissociation. The haemolymph of parasitized hosts had reduced phenoloxidase activity, and teratocytes inhibited phenoloxidase activity when coincubated with plasma from nonparasitized hosts. The injection of teratocytes into nonparasitized fifth‐instar L. oleracea larvae suppressed growth and induced a supernumerary moult in some larvae. A number of parasitism‐specific proteins were detected in the haemolymph of parasitized hosts, and incubation of teratocytes in culture media indicated that these cells were a source of at least two of these proteins.     

Influence of the braconid Glyptapanteles liparidis on the juvenile hormone titer of its larval host,the gypsy moth,Lymantria dispar

The increase in the juvenile hormone (JH) III titer in the hemolymph of Lymantria dispar larvae that were parasitized by the endoparasitoid braconid, Glyptapanteles liparidis, during the host's premolt to third instar, coincided with the molt of the parasitoid larvae to the second instar between day 5 and 7 of the fourth host instar. It reached a maximum mean value of 89 pmol/ml on day 7 of the fifth instar while it remained below 1 pmol/ml in unparasitized larvae. Only newly molted fifth instar hosts showed a low JH III titer similar to that of the unparasitized larvae. JH II, which is the predominant JH homologue in unparasitized gypsy moth larvae, also increased relative to controls in the last two samples (days 7 and 9) from parasitized fourth and fifth instars. Compared to unparasitized larvae, a generally reduced activity of JH esterase (JHE) was found in parasitized larvae throughout both larval stages. The reduction in enzyme activity at the beginning and at the end of each instar, when the JHE activity in unparasitized larvae was high, may be in part responsible for the increased JH II and JH III titers in parasitized larvae. Ester hydrolysis was the only pathway of JH metabolism in the hemolymph of unparasitized and parasitized gypsy moth larvae as detected by chromatographic assays. © 1996 Wiley-Liss, Inc.     

亚洲玉米螟末龄幼虫促前胸腺激素与蜕皮甾类激素滴度的变化

用放射免疫分析法(Radioimmunoassay,RIA)以12小时间隔测定了亚洲玉米螟Ostrinia tfurnacalis末龄非滞育幼虫血淋巴中蜕皮甾类激素滴度.通过前胸腺体外培养,以12小时间隔测定了前胸腺体外分泌活性的变化.发现二者的变化在相同发育阶段是一致的.在亚洲玉米螟上建立了促前胸腺激素(PTTH)体外测定法,并用此法以24小时间隔测定了末龄幼虫脑和血淋巴中PTTH滴度.发现血淋巴中PTTH滴度在末龄第5和7天各有一高峰,脑中只在第5天有一高峰.