Endocrine manipulations and ontogenesis of male sexual behaviour in Locusta: studies on azadirachtin-induced over-aged nymphs

ABSTRACT. Dose-response relations of the moult-inhibitory and lethal effects of azadirachtin (AZA) injected into fifth and fourth instar hoppers of Locusta migratoria migratorioides are presented. The optimal dose for obtaining maximum number of long-surviving over-aged nymphs is 1.6 and 1.0 μg of AZA per insect for young fifth and fourth instar nymphs, respectively. Over-aged male nymphs are capable of exhibiting sexual behaviour. The mating behaviour of fifth instar over-aged male nymphs, and of chemically allatectomized but otherwise similar over-aged male nymphs (obtained by combined precocene treatment and injection of AZA), with and without injections of exogenous Juvenile Hormone III (JH), is investigated quantitatively; the results are compared with those obtained for normal, chemically allatectomized, and chemically allatectomized plus JH-injected adult males. Over-aged fifth instar male nymphs show a low intensity of mating behaviour and in chemically allatectomized ones this intensity is even lower. Injections of JH intensify the mating behaviour of chemically allatectomized fifth instar over-aged male nymphs in a dose-dependent way, but less markedly so than in chemically allatectomized adult males. We conclude that the intensity of male mating behaviour of the over-aged nymphs is subnormal and their response to the mating behaviour intensifying effect of the JH is weaker than that of adult males. The relations between endocrine factors and ethological ontogenesis of male sexual behaviour in locusts are discussed.     

Endocrine manipulations and ontogenesis of male sexual behaviour in Locusta: studies on precocene-induced early adultiforms

ABSTRACT. Fourth- and third-instar permanent adultiforms of Locusta migratoria migratorioides (R.&F.) were produced by applying 7-ethoxy-precocene II (precocene III) to hoppers in earlier stages. The mating behaviour of male adultiforms and the effects of injected exogenous juvenile hormone III (JH) on this behaviour were investigated quantitatively and the results were compared to those obtained for normal adult males and for adult males chemically allatectomized by precocene III. Fourth- and third-instar adultiform males exhibited sexual behaviour and injections of JH intensified this behaviour in a dose-dependent manner, though the number of repeated injections in which a cumulative dose is administered was found to be not less important than the amount of the cumulative dose itself. Huge repeated doses (6×144=864 μg) of JH temporarily induced normal intensity of mating behaviour in fourth-instar male adultiforms. The same doses of JH intensified mating behaviour also in third-instar adultiform males, but less markedly so than in fourth-instar ones. For restoring temporarily normal intensity of mating behaviour in chemically allatectomized but morphogenetically normal adult males, much smaller doses (2×36=72, or 2×72=144μg) of JH were sufficient. In contrast, even huge doses of JH were unable to induce mating behaviour in normal (no precocene-treated) male hoppers. Thus, the ethological ontogenesis (='ethogenesis') of the male's mating behaviour, including the response of the system to JH, is clearly accelerated by precocious metamorphosis. However, this is not a simple 'all or none' effect, because adultiforms in earlier stadia exhibit less intense male mating behaviour and more limited response to JH than adultiforms in later stadia or adults.     

Effects of the corpora allata on sexual receptivity and completion of oocyte development in females of the cricket, Gryllus bimaculatus

Abstract Allatectomy of young penultimate nymphs of Gryllus bimaculatus De Geer (Gryllidae) resulted in prothetelic creatures which exhibited reproductive competence. The same operation performed on young last instar nymphs resulted in moulting to morphologically normal adults. Allatectomized morphologically normal adult females, as well as prothetelic ones, showed the same level of sexual receptivity as untreated control females. Allatectomized morphologically normal and prothetelic females laid viable eggs, but rate of egg laying and number of eggs produced by these females were much reduced in comparison with the controls. Administration of methoprene (a Juvenile Hormone analogue) to allatectomized females restored egg production to a more or less normal rate. Removal of the spermatophore within 10 min of copulation had no effect on subsequent sexual receptivity of the females, nor on the reduced rate of egg laying by the allatectomized females, but did affect the rate of egg laying by control females.
It is suggested that the corpora allata (CA) and the Juvenile Hormone (JH) play no major role in controlling basic sexual receptivity of G.bimaculatus females, and do not have an all-encompassing control on egg production, though they do exert a marked quantitative effect on the rate of egg production.     

Effects of juvenile hormone treatment on phase changes and pheromone production in the desert locust,Schistocerca gregaria (Forskal) (Orthoptera: Acrididae)

The roles of juvenile hormone III (JH III) on phase changes and pheromone production were examined in laboratory-reared gregarious desert locust, Schistocerca gregaria (Forskal). The hormone was applied to 5th instar nymphs and newly emerged adult locusts. Generally, the 5th instar nymphs exhibited a higher sensitivity to hormone treatments than the adults. Hormone applications inhibited pheromone production (as measured by the amounts of phenylacetonitrile released). In addition, JH III had a significant effect on the external colouration and absorbance ratios of the haemolymph pigments. It is concluded that the effects of exogenous JH III on gregarious locusts represent a shift towards the solitarious phase.     

The morphological and behavioural effects of precocene II on Locusta

The precocious adultiform larvae produced by topical applications of precocene II to early 4th instar Locusta were found to be intermediate between normal 5th instar larvae and normal adults on behavioural as well as morphological criteria. Precocious adultiforms walked significantly smaller distances in 2 hr than normal larvae, but slightly more than normal adults. The adultiforms jumped significantly greater distances without wing movements than normal larvae, but they also made frequent, short, adult-type jumps with wing movements. Most advanced adultiforms made jumps of both types whereas normal adults made only a small percentage of the larval-type jumps. Apparently the central nervous organisation of the adultiforms provides equally and separately for both larval and adult behaviour patterns, rather than compounding the two.Increasing doses of precocene above 100 μg produced more advanced adultiforms, and there was some indication that morphologically similar types produced by different doses may differ in their behaviour.     

Juvenile hormone activity in larvae and adult females of the locust, Schistocerca gregaria

The isolation and purification of fractions with juvenile hormone activity from whole animal extracts of larvae, and from extracts of haemolymph from larvae and adults is described. Using the Galleria bioassay three such fractions were isolated from both third and fourth instar hoppers and from adult females. The chromatographic behaviour of these fractions indicates that one contains JH III, but the other two contain unknown juvenilizing compounds.     

Effects of hexane extract of Lantana camara leaves on reproductive bioactivities of Dysdercus koenigii Fabricius (Heteroptera: Pyrrhocoreidae)

Effects of hexane extract of Lantana camara leaves were investigated on reproductive bioactivities of Dysdercus koenigii by assessing mating behavior, oviposition behavior and fertility of the adults emerged from treated fifth instar nymphs. Leaves of L. camara were extracted in hexane by ‘cold extraction method’. The fifth instar nymphs were treated with the extract by ‘dry film residual method’ for 24 h and the adults emerged from these nymphs were used for the experiments. The results indicated that treated males showed altered courtship behaviour, lesser number of mounting attempts and took relatively more time to mate than the normal males. The treated females, very often, exhibited mating refusal and non-receptive behaviour towards the courting males. This led to decrease in percent successful mating. Also, the mating in the treated insects frequently got disrupted and terminated prior to insemination. The treatment of the females with the extract resulted in alteration of their oviposition behaviour. Consequently, the treated females laid lesser number of egg batches and total number of eggs in their life span. Although the eggs laid by the treated females were fertile, the percent hatchability was lesser than normal. The results signify that hexane leaf extract of L. camara possesses phytochemicals, which adversely impaired the reproductive bioactivities of D. koenigii. Therefore, some of these compounds individually or synergistically can be employed in integrated pest management of D. koenigii by hampering its reproductive potential.     

The consumption, digestion and utilization of food by Locusts

A comparative study was made of the consumption, digestion and utilization of cabbage by the 3rd-, 4th- and 5th-instar hoppers of Schistocerca gregaria and Locusta migratoria. The rate of consumption (C.I.) and the digestibility (except in 3rd instar) of cabbage by Locusta hoppers were greater than by Schistocerca hoppers. However, weight increase, growth rate (except in 4th instar), gross and net efficiency of food utilization were found to be significantly higher in Schistocerca hoppers than in Locusta hoppers. The total live weight gain of Schistocerca hoppers for a period of 18 days was about twice that in Locusta hoppers. Slower growth rate and lesser efficiency of food utilization by Locusta hoppers were considered to be due to nutrient imbalance of cabbage for Locusta.

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Zusammenfassung Es wurde eine vergleichende Untersuchung des Verbrauchs, der Verdauung und der Ausnutzung von Kohl durch das 3., 4. und 5. Larvenstadium von Schistocerca gregaria und Locusta migratoria durchgeführt. Die Verbrauchsrate (C.I.) und die Verdaulichkeit von Kohl war (mit Ausnahme des 3. Larvenstadiums) bei Locusta-Larven größer als bei Schistocerca-Larven. Jedoch erwiesen sich Gewichtszunahme, Wachstumsrate (mit Ausnahme des 4. Larvenstadiums), Brutto- und Netto-Wirkungsgrad der. Nahrungsverwertung bei Schistocerca-Larven als signifikant höher als bei denen von Locusta. Die gesamte Lebendgewichtszunahme von Schistocerca-Larven war über einen Zeitraum von 18 Tagen etwa zweimal so groß wie bei Locusta-Larven. Die langsamere Wachstumsrate und der geringere Wirkungsgrad der Nahrungsausnutzung durch die Locusta-Larven werden als Folge der nutritiven Unausgeglichenheit von Kohl für Locusta angesehen.

     

Parallel control mechanisms underlying locomotor activity and sexual receptivity of the female German cockroach,Blattella germanica (L.)

We have studied the effects of ovaries, juvenile hormone (JH) and mating on locomotor activity and sexual receptivity of female German cockroaches. Our results indicate that locomotor activity and sexual receptivity are under the same control mechanisms. The ovary served as a negative masking factor for the locomotor circadian rhythm, but did not affect the frequency of locomotor activity. We conclude that JH controls the locomotor activity of females from the following evidence: (1) increasing locomotion of virgin females coincided with an increasing volume of the corpora allata; (2) allatectomy reduced female locomotion significantly; (3) after absorbing the JH analogue (fenoxycarb) through their tarsi, allatectomized females regained their high level of locomotor activity. Since the daily locomotor activity of allatectomized and ovari-allatectomized females changed cyclically with continuous (non-cyclic) contact of fenoxycarb, an unidentified factor which was independent of ovarian development is proposed to regulate cyclic locomotor activity. In addition to controlling the frequency of locomotor activity, JH was essential for the expression of the locomotor circadian rhythm because allatectomy abolished the circadian rhythm expressed in ovariectomized females. Mating significantly decreased the frequency of locomotor activity and the degree of sexual receptivity. The inhibitory effect of mating resulted from the transmission of a mating signal through the ventral nerve cord when sperm was transferred successfully. The mating experiments with allatectomized and ovariectomized females showed that JH was the major factor in regulating the expression of sexual receptivity.     

Development of imaginal competence to adipokinetic hormone in Locusta: Lipid and carbohydrate levels,and glycogen phosphorylase activity in azadirachtin-induced over-aged nymphs

• 1.1. Adipokinetic responses to injection of synthetic adipokinetic hormone I (sAKH) and relevant physiological parameters were studied in azadirachtin-induced 31 to 34-day-old Vth-instar over-aged male nymphs of Locusta migratoria which did not undergo the metamorphic moult to adult.
• 2.2. The resting lipid and carbohydrate levels in the haemolymph and sAKH-induced activation of fat body glycogen phosporylase did not differ markedly between over-aged nymphs, normal nymphs and normal adults.
• 3.3. Total fat body glycogen phosphorylase activity and the effect of sAKH on haemolymph carbohydrate level in over-aged nymphs were similar to those in normal adults and differed from those in normal nymphs.
• 4.4. sAKH-induced elevation of haemolymph lipid level in the over-aged nymphs was higher than in normal nymphs but lower than in normal adults; thus, the over-agad nymphs attained only a partial adult competence in this respect.

     

Muscle activity underlying sexual behaviour in male locusts (Locusta migratoria) after normal and hormonally disturbed development

Abstract. . The activities of three sets of muscles, representing the major components of the abdominal muscle system, were recorded in the pregenital abdominal segments of adult males of Locusta migratoria. The muscular activities were associated with three consecutive actions of the male's mating behaviour: abdominal lowering, S-bending and hooking-up. These three actions depend mainly on the relative coordination of the dorsal versus ventral longitudinal muscles; the activity of the dorsoventral muscles is rather unpredictable, except in the sixth and seventh abdominal segments where they are regularly involved in hooking-up. Studies on male sexual behaviour-linked muscle activity in precocene-induced fifth-instar adultiforms and azadirachtin-induced fifth-instar over-aged nymphs revealed no distinct differences between these creatures and normal mature males. Therefore the muscle activities associated with these adult-specific behavioural acts can be released precociously, i.e. their occurrence is not dependent on a distinct series of instars. Moreover, the results obtained with over-aged nymphs demonstrate that morphogenesis and ethogenesis (i.e. formation of neural circuits controlling adult-specific behaviour) are not closely dependent on each other.     

褐飞虱体内保幼激素滴度变化及其与翅型分化的关系

用高压液相色谱及放射化学法,分别测定了褐飞虱Nilaparvata lugens 1～5龄若虫体内的保幼激素滴度与保幼激素酯酶活性变化,并用保幼激素类似物(ZR-515)进行体表点滴加以验证。结果表明,褐飞虱雌、雄4龄若虫期及雄虫的5龄若虫初期,短、长翅型间体内保幼激素滴度差异明显,可以认为该阶段是其翅型分化的关键时期。     

Postembryonic development of mating behavior in the male cricket Gryllus bimaculatus DeGeer

Summary The intact male nymph cricket, Gryllus bimaculatus DeGeer, was found to show mating-like behavior, that is, courtship-like behavior (CSLB) and copulation-like behavior (CPLB), in the 7th and 8th (last) instars. The 8th instar nymph exhibited less CSLB and CPLB than the adult but much more than the 7th instar nymph. The movement patterns of CSLB and CPLB were essentially the same as those of adults except for motor acts requiring the use of the genitalia. CSLB was short and often ceased spontaneously before it switched to CPLB. CPLB also ended earlier than in adults. The occurrence of CSLB and CPLB was almost zero the few days around ecdysis. The nymph was very sensitive to disturbance, so that he often stopped courtship for more than 30 min after stimulation. CSLB was similarly induced in the male nymph (8th instar) by pairing with a female adult, male adult, female nymph (8th) and male nymph (8th). The female nymph (8th) was observed to mount not only the male adult but also the male nymph (8th). A fixed time sexual refractoriness forming a basis of cyclical mating activity was not present after CPLB in the nymph. It appeared in association with the emergence of spermatophore protrusion behavior around day 3 after the imaginal molt. In fledglings, there were some transitions during the sexual maturation process, such as failures in hook hanging, spermatophore extrusion, and spermatophore transfer to the female. The decerebration experiments on nymphs and fresh adults agreed with behavioral observations. These results suggest that the development of mating behavior in the male cricket is a process of enhancement of basic motor patterns but not a process of addition of new movements by changes in pattern generation circuits in the central nervous system.Abbreviations CPLB copulation-like behavior - CPPT interval between copulation and spermatophore protrusion - CSCP interval between calling song and copulation - CSLB courtship-like behavior - CSS courtship song - PTCS interval between spermatophore protrusion and calling song - SPE spermatophore extrusion     

Effect of exogenous juvenile hormones on mating behaviour and yellow colour in allatectomized adult male desert locusts

ABSTRACT. A comprehensive dose–response study of exogenous juvenile hormones, JHI and JHIII, on mating behaviour and on yellowing was carried out in allatectomized, crowded adult Schistocerca americana gregaria males. Injections of either hormone induced mating behaviour, but topical applications were almost completely ineffective. In contrast, topical applications were at least as effective as injections for inducing yellow colour. Induction and/or intensity of mating behaviour was dependent on the number of (repeated) administrations (from one to eight) and on the cumulative dose (80 or 160/μg) of the hormone, but these factors, within the above ranges, showed no distinct dose-response relationship to yellowing. Even 160/μg of cumulative dose, given in the relatively most effective way (eight repeated injections of 20 /μg each), did not fully restore mating behaviour; the level of maximum intensity reached about half of that obtained for non-allatectomized controls. JHI and JHIII did not differ markedly in this respect, but a 1:1 mixture of the two hormones improved the effect, revealing a mild synergy. JHI induced maximum or near maximum yellowing, but JHIII, under any conditions tested, was unable to induce full yellowing. The effect was always temporary; after cessation of JH administrations mating behaviour rapidly declined and the yellow colour slowly faded. The results indicate that the response of the two physiological systems (male mating behaviour and yellowing) to exogenous JH is completely independent. Although, depending on conditions of administration and on the kind of hormone, exogenous JHs were able to restore mating behaviour and yellowing, effective doses were extremely high. These conclusions are further discussed.     

Persistence of phonotaxis in females of four species of crickets following allatectomy

The role of Juvenile Hormone III in phonotaxis, mating behavior and egg production of cricket females from Gryllus campestris, Gryllus bimaculatus, Teleogryllus commodus, and Acheta domesticus was investigated.

Variations induced by juvenile hormone and precocene II in the metabolic rate of 3 species of insects

The effects of juvenile hormone and precocoene II on the metabolic rate of Blattela germanica L. (Blattaria, Blattellidae), Spilostethus pandurus Scop. (Heteroptera: Lygaeidae) and Oncopeltus fasciatus Dallas (Heteroptera: Lygaeidae) 5th instar nymphs and adults have been investigated. Direct volumetric method was used to determine the oxygen consumption rate. JH produced a stage and/or sex dependent increase in the metabolic rate according to the species considered. On the other hand, PII decreased oxygen consumption in Blattella germanica and S. pandurus fifth instar and males, whereas O. fasciatus metabolic rate was not affected by the treatment.     

Effects of Ocimum sanctum hexane extract on survival and development of Dysdercus koenigii Fabricius (Heteroptera: Pyrrhocoriedae)

Abstract

The effects of hexane extract of Ocimum sanctum leaves on the survival, longevity, growth and development of the Dysdercus koenigii Fabricius were investigated. Newly emerged fifth instar nymphs were exposed to nine concentrations ranging from 0.00625% to 10% of the extract for 24?h by “dry film residual method.” The results indicated that the extract has adverse effect on various life activities studied. The effects were dose related; exposure to a dose of 5% or more causes high mortality. Normal adults were not produced from the nymphs treated with extract concentrations of 1.25% or more. The treated nymphs exhibited developmental malformation. The gas chromatography and mass spectroscopy analysis of the extract revealed presence of chemical compounds having insecticidal and juvenile hormone (JH) mimicking activities. Some of the compounds act as precursors of JH biosynthetic pathways. Therefore, these compounds may individually or synergistically can be used in management of D. koenigii and other insect pests.     

亚洲柑橘木虱成虫和5龄若虫在感染黄龙病的柑橘上的取食行为及获菌效率比较

【目的】亚洲柑橘木虱Diaphorina citri是柑橘的毁灭性病害——黄龙病亚洲种‘Candidatus Liberibacter asiaticus’(‘C las’)的主要传播媒介。本研究的目的是明确木虱成虫和5龄若虫的取食行为、获菌效率是否有差异,以及寄主感染黄龙病是否对5龄若虫取食产生影响。【方法】利用直流型刺吸电位仪(DC-EPG Giga-4)记录柑橘木虱成虫和5龄若虫在携带黄龙病的酸橘Citrus reticulata cv.Sunki嫩梢上10 h的取食行为,用qPCR单头检测其获得黄龙病病原菌的效率,并比较5龄若虫在感病和健康植株嫩梢上的取食行为。【结果】柑橘木虱成虫与5龄若虫在感染黄龙病的酸橘上的取食行为有显著差异。5龄若虫比成虫更快地开始在韧皮部和木质部进行吸食,口针在韧皮部的总过程以及吸食时间显著长于成虫。此外,5龄若虫和成虫在EPG测定(同时饲菌)10 h后获菌率分别为37.5%和20.0%,若虫明显高于成虫。寄主植物感染黄龙病对5龄若虫的取食行为有一定的影响,表现在感病植株上的刺探次数、唾液分泌次数和韧皮部吸食次数都显著少于健康植株,而两者分泌唾液和韧皮部吸食时间没有显著差异。另外,在感病植株上首次韧皮部取食出现时间较在健康植株上要早。【结论】在同等时间下,柑橘木虱5龄若虫比成虫在感染黄龙病的酸橘上的取食能力更强、取食量更大、获菌率更高,原因可能是若虫需要更多的营养物质供其生长发育所致。寄主感染黄龙病对木虱5龄若虫的取食有利,使其更快地开始取食,而且更改取食位点次数变少,推测可能与黄龙病菌破坏了植物的防御有关。     

Actions juvénilisante,chromatotrope, gonadotrope,et cardiotrope de- JH-III sur Locusta migratoria

The effects of JH-III, a chemical compound close to JH, are studied on different functions in which the corpora allata are involved. JH-III shows a clear prothoracotropic effect by shortening the length of the instar in which it is injected. Doses which comprised between 50 and 200μg/animal have a real juvenilizing and chromatotropic effect. But in all cases the effect is lower because this one is produced by the same doses of JH or by an implantation of one pair of corpora allata. JH-III allows the oöcytes of allatectomized females to develop. On control insects JH-III is not able to increase cardiac activity but at doses of 200 μg/animal it counterbalances the 10 per cent decrease brought about by allatectomy.JH-III, despite its chemically closeness to natural JH, appears to be less potent than more distant compounds such as Altozar and Altosid.     

Identification and partial characterization of juvenile hormone esterase from cotton pest Dysdercus cingulatus

Juvenile hormone esterase (JHE), a selective enzyme that hydrolyzes the methyl ester of insect juvenile hormone plays an important role in regulating metamorphosis in nymphs as well as reproduction in adults. Studies on JH degradation provide insight into the possibilities of physiological disruption in the insects. In the present study, the JH degrading enzyme, JHE from the cotton pest Dysdercus cingulatus (Heteroptera) is characterized. Electrophoretic analysis of haemolymph during various developmental stages showed the JHE bands prominent only on the final day of 5th instar nymph, and the esterase substrate specificity confirmed the presence of JHE isoforms. In an attempt to clone cDNA of JHE gene from the final instar nymphs, mRNA isolated from fat bodies was coupled with JHE gene-specific primers and the cDNA was synthesized using RT-PCR. The PCR amplified cDNA showed the presence of JHE isoforms in D. cingulatus.