Dose-dependent response characteristics of antennal lobe neurons in the male moth Agrotis segetum (Lepidoptera: Noctuidae)

Responses of antennal lobe neurons to different amounts of the female-produced pheromone blend and to its individual components were investigated in Agrotis segetum males using intracellular recording methods. We identified three physiological types of antennal lobe neurons, categorized according to their response thresholds to single pheromone components and to the blend: generalist neurons, component-specific neurons and blend-specific neurons. Response and specificity of antennal lobe neurons were largely dose dependent. In most cases specific responses occurred only at low stimulus amounts, while increasing concentrations often resulted in an increase of the number of pheromone stimuli to which the neuron responded. Dose-response relationships often differed between different stimuli activating a neuron. Accepted: 24 May 1997     

Structure and function of antennal lobe neurons in the male turnip moth,Agrotis segetum (Lepidoptera: Noctuidae)

Interneurons with dendritic branches in the antennal lobe of the male turnip moth, Agrotis segetum (Schiff., Lepidoptera: Noctuidae), were investigated with intracellular recording and staining methods. Seventeen projection neurons that transmit information from the antennal lobe to higher centers in the brain displayed dendritic arbors in the male specific macroglomerular complex (MGC) and responded to chemical components of the female sex pheromone used in species-specific sexual communication. Most of the projection neurons responded to several of the pheromone components tested, and a precise correlation between the location of the dendritic arborization and the physiological response could not be demonstrated. One MGC-projection neuron fit the definition of blend specialist. It did not respond to the individual components of the behaviorally active pheromone blend, but showed a strong response to the components when combined in the species-specific blend. Some of the projection neurons also showed clear responses to phenylacetaldehyde, a flower-produced compound and/or to (E)-2-hexenal, a common green-leaf volatile. In eight neurons, the axonal projection could be followed to the calyces of the mushroom body, and subsequently to the inferior lateral protocerebrum.Four local interneurons were characterized both morphologically and physiologically. Each neuron arborized extensively throughout the antennal lobe, and each responded to one or several of the pheromone compounds, and/or to one or both of the plant-produced compounds. One of the local interneurons responded exclusively to the pheromone blend, but not to the individual components.Abbreviations AL antennal lobe - AN antennal nerve - CB cell body - E2H (E)-2-hexenal - IACT inner antennocerebral tract - ILPR inferior lateral protocerebrum - LH lateral horn of the protocerebrum - LN local interneuron - MB mushroom body - MGC macroglomerular complex - OACT outer antennocerebral tract - PAA phenylacetaldehyde - PN projection interneuron - RN receptor neuron - Z5-10:OAc (Z)-5-decenyl acetate - Z5-10:OH (Z)-5-decenol - Z5-12:OAc (Z)-5-dodecenyl acetate - Z7-12:OAc (Z)-7-dodecenyl acetate - Z9-14:OAc (Z)-9-tetradecenyl acetate     

Sex pheromone precursors in Spodoptera littoralis (Lepidoptera: Noctuidae)

Female pheromone gland extracts of Spodoptera littoralis were analyzed for pheromone precursors. Large amounts of fatty methyl esters were found and a positive relationship between the methyl esters and the pheromonal components was observed. The esters were identified on the basis of capillary gas chromatography, coupled gas chromatography with mass spectroscopy and dimethyl disulfide derivatization, and subsequent gas chromatography with mass spectrometry. The characteristic fatty esters of S. littoralis are methyl (Z)-9-tetradecenoate, (E)- and (Z)-11-tetradecenoate, (Z,E)-9,12-tetradecadienoate, (Z,E)-9,11-tetradecadienoate, and (Z)-11-hexadecenoate. The biosynthesis of the monosaturated acids involves probably the common E11 and Z11 desaturases and chain shortening. For the biosynthesis of the novel diene acids, we propose a second, specific desaturation of (Z)-9-tetradecenoate by an E11 desaturase to produce (Z,E)-9,11-tetradecadienoate or by an E12 desaturase to produce (Z,E)-9,12-tetradecadienoate.     

Spatial representation of odours in the antennal lobe of the moth Spodoptera littoralis (Lepidoptera: Noctuidae)

Glomeruli within the antennal lobe (AL) of moths are convergence sites for a large number of olfactory receptor neurons (ORNs). The ORNs target single glomeruli. In the male-specific cluster of glomeruli, the macroglomerular complex (MGC), the input is chemotypic in that each glomerulus of the MGC receives information about a specific component of the conspecific female sex pheromone. Little is known about how neurons that detect other odorants arborize in and amongst glomeruli. The present study focuses on how sex pheromones and biologically relevant semiochemicals are represented in the ALs of both sexes of the moth Spodoptera littoralis. To assess this, we optically measured odour-evoked changes of calcium concentration in the ALs. Foci of calcium increase corresponded in size and shape with anatomical glomeruli. More than one glomerulus was normally activated by a specific non-pheromonal odorant and the same glomerulus was activated by several odorants. All odorants and pheromone components tested evoked unique patterns of glomerular activity that were highly reproducible at repeated stimulations within an individual. Odour-evoked patterns were similar between individuals for a given odorant, implicating a spatial olfactory code. In addition, we demonstrated that activity patterns evoked by host-plant related volatiles are similar between males and females.     

Plant odour processing in the antennal lobe of male and female grapevine moths,Lobesia botrana (Lepidoptera: Tortricidae)

Moths of Lobesia botrana (Lepidoptera: Tortricidae) are confronted with different volatiles emitted from the host plant during the different seasons. To test the hypothesis of plasticity of central plant odour processing in moths of different generations in the future, we first investigated the responses of antennal lobe (AL) interneurons of laboratory-reared virgin and mated males and females. We used intracellular recording and staining techniques while stimulating the antenna with a range of host and non-host plant odours. The AL structure of L. botrana is similar to that found in other Lepidoptera species studied. The most frequent physiological responses for all types of moths were obtained with (E)-2-hexenal, and with thujyl alcohol and β-thujone, components of tansy, a behaviourally attractive non-host plant. Some broadly responding neurons were capable of distinguishing between different compounds through different response patterns (excitation/inhibition) and/or different dose-response characteristics. Response characteristics (response spectra, threshold and specificity) of neurons were similar, independent of sex or mating status of the moths. Significant differences between the groups were, however, found in the proportion of responding neurons for a few tested components.     

Interactions of mechanical stimuli and sex pheromone information in antennal lobe neurons of a male moth,<Emphasis Type="Italic"> Spodoptera littoralis</Emphasis>

Male moths respond to sex pheromone sources with up-wind flight behaviour. Localization of the odour source requires not only detection of the olfactory stimulus, but also other sensory input regarding, e.g. visual and mechanical stimuli. Thus, integration of different types of sensory input is necessary. It is, however, not known where in the central nervous system the integration of information regarding different sensory modalities takes place. Using intracellular recording and staining techniques, we investigated neurons in the antennal lobe of Spodoptera littoralis, during stimulation with a mechanical stimulus and a sex pheromone. Fifteen percent of all the neurons investigated responded to the mechanical stimulus and the majority of these neurons showed altered responses if the olfactory stimulus was added. A receptor neuron responding only to the wind stimulus was found to arborise in the antennal lobe. Most projection neurons responded with an enhanced action potential frequency to the combined stimulus. In local interneurons, enhancement, depression, or no change of the responses to the wind stimulus was found when the olfactory stimulus was added. The results suggest that neurons present in the antennal lobe integrate mechanosensory and olfactory input, possibly assisting the moths to orient during up-wind flight towards an odour source.     

The effects of the antennal flight posture and orientation on the pheromonal stimulation patterns experienced by male Spodoptera littoralis (Lepidoptera: Noctuidae)

Heads of Spodoptera littoralis males with their antennae artificiallyelevated and stabilized to imitate their flight posture, wereexposed at different inclinations to a mobile beam of pulsedpheromones. The electroantennogram patterns recorded for variouslinear tracks simulated in this manner were closely linked tothe spatial pheromone density distribution. Thus, during in-flightmate detection, the normally elevated antennae appear to functionas a sensitive, instantaneous detector of conspecific femalesex pheromone, informing the insect of contact with, amount,loss or recovery of the stimulant.     

Central nervous processing of behaviourally relevant odours in solitary and gregarious fifth instar locusts, Schistocerca gregaria

Physiological and morphological characteristics of antennal lobe neurons of solitary and gregarious fifth-instar nymphs of the desert locust, Schistocerca gregaria, were studied using intracellular recording and staining techniques. Physiological characteristics of antennal lobe neurons of both locust phases responding to stage-dependent aggregation pheromones, egg-laying attractants, a putative sex pheromone and plant-associated volatiles are described. Antennal lobe neurons showed excitatory, inhibitory, combined excitatory and inhibitory and delayed responses. In addition, one neuron␣showing an initial inhibition followed by an excitation and inhibition response was found. Pheromone-specific-, plant-specific- and pheromone-plant-generalist neurons were found in both locust phases. Antennal lobe neurons displayed stage- and phase-dependent differences in the processing of aggregation pheromone component input. Nymphal antennal lobe neurons showed stage-dependent response characteristics highly correlated with the preferential behavioural attraction to the nymphal aggregation pheromone. Phase-dependent differences were found in the response spectra and the sensitivity of the same neuron types. Neurons of solitary locusts responded significantly more frequently to some of the tested components than neurons of gregarious locusts. Furthermore, antennal lobe neurons of solitary locusts showed a higher sensitivity to most of the tested compounds. Accepted: 4 July 1998     

Lethal and sublethal effects of methoxyfenozide and spinosad on Spodoptera littoralis (Lepidoptera: Noctuidae)

Susceptibility to methoxyfenozide of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) larvae was determined through exposure of neonate and fourth instars to dipped and sprayed pepper, Capsicum annum L., leaves. Methoxyfenozide and spinosad were tested against adults of this noctuid by oral, residual, and topical application. In larvae, we evaluated five (range, 0.001-10 mg active ingredient [AI] /liter) and six (range, 1-250 mg [AI] /liter) concentration levels by instars, respectively, by using two application methods at three different age leaf residues (0, 3, and 6 d after application). According to LC50 values, no significant differences were observed between the same age leaf residues of both application methods at 96 and 72 h after ingestion treatment on neonates and fourth instars, respectively. Nevertheless, toxicity of methoxyfenozide decreased significantly after time. For both application methods, the LC50 values of the first leaf residue (0 d after application) were significantly lower than those of 6-d-old residues. Furthermore, larval weight of fourth instars fed for 48 h with pepper, Capsicum annum L., leaves containing methoxyfenozide was significantly suppressed. Spinosad and methoxyfenozide reduced in a dose-dependent manner the fecundity and fertility of S. littoralis adults when treated oral and residually. Likewise, when methoxyfenozide was administered orally in three different adult crosses, the fecundity was strongly affected, independently of the treated sex. We conclude that the combination of lethal and sublethal effects of methoxy-fenozide and spinosad might exhibit significant effects on the population dynamics of S. littolaris.     

Viral-enhancing activity of an optical brightener for Spodoptera littoralis (Lepidoptera: Noctuidae) nucleopolyhedrovirus

The effect of an optical brightener on the insecticidal activity of a Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) nucleopolyhedrovirus (SpliNPV) were examined in three instars of S. littoralis. LD₅₀ values of the SpliNPV were reduced from 33 to <5, 73 to 5.7 and 342 321 to 288 412 occlusion bodies for second, third and fourth instars, respectively, by the addition of 1% Tinopal UNPA-GX. Relative potencies were >66, 12.8, and 1.2 for second-. third- and fourth-instar S. littoralis larvae, respectively. Relative mortality between the treatments with and without the brightener decreased from third- to fourth-stage larvae. In terms of speed of kill, the ST₅₀ values of the baculovirus-infected larva were reduced from 210 to 159, 213 to 147, and 207 to 165 h for second-, third- and fourth-instar larvae, respectively, by the addition of the optical brightener at biologically equivalent doses.     

Bioefficacy of cadmium and lead on cotton leafworm Spodoptera littoralis (Lepidoptera: Noctuidae) larvae

The sensitivity of Spodoptera littoralis second and fourth instar larvae to the heavy metals cadmium (Cd) and lead (Pb) was investigated under laboratory conditions. Both Cd and Pb, even, at very low concentrations, had relatively high toxic effects on S. littoralis larvae. Cd was more toxic to S. littoralis larvae than Pb. In addition, the mean percentage feeding deterrence (FDI%) of Cd and Pb was concentration-dependent. The nutritional indices (consumption index, growth rate, efficiency of converted ingested and digested food, and approximate digestibility) of S. littoralis second and fourth instar larvae were more affected in Cd-treatments compared with those of Pb-treatments. Therefore, the presence of such heavy metals in the environment would exert an adverse impact on S. littoralis larvae and their development.     

Occurrence and characterization of a nucleopolyhedrovirus from Spodoptera littoralis (Lepidoptera: Noctuidae) isolated in the azores

A nucleopolyhedrovirus (SpliMNPV-Az) was isolated from diseased larvae of Spodoptera littoralis, collected at the Island of S. Miguel in Azores. The virulence of this isolate was tested against S. littoralis larvae in laboratory. LD₅₀ against 2nd and 3rd instars were not significantly different, 1.44 × 10⁴, 3.89 × 10⁴ OBs per larvae, respectively, but both were significantly different from that against 4th instar, which was 61.3 × 10⁴ OBs per larvae. The complete codons sequence of SpliMNPV-Az Polh gene obtained was 750 bp (NCBI GenBank Accession No. AY600451). This sequence was compared to other 38 polyhedrin genes from NPVs and to 6 granulin genes from GVs and resulted to be identical to the sequence of a SpliMNPV previously published, thus indicating that the natural host of SpliMNPV-Az must be S. littoralis. Genetic distances estimated from restriction enzymes profiles showed SpliMNPV-Az is close to the Egyptian SpliMNPV type B, despite some degree of genetic divergence suggested by slight differences observed on PstI profile.     

交配和温度对草地贪夜蛾性信息素通讯的影响

【目的】明确交配和温度对草地贪夜蛾Spodopterafrugiperda性信息素通讯的影响,为田间草地贪夜蛾的性信息素防治提供参考。【方法】采用溶剂浸提法提取草地贪夜蛾雌蛾性信息素腺体中的化学组分;利用气相色谱-质谱联用（GC-MS）技术对提取物中的组分进行化学鉴定;利用气相色谱（GC）技术分析雌蛾腺体中各组分的含量;利用触角电位（EAG）技术测定雄蛾对腺体各组分及性信息素类似物的电生理反应。在不同温度（20-35）℃下饲养草地贪夜蛾,以研究温度对其性信息素通讯的影响。【结果】GC-MS分析发现,草地贪夜蛾雌蛾腺体内含有Z7-12:Ac等7种组分。交配实验表明,雌蛾在1个暗期内只交配1次,在羽化后7 d内可交配多次,其中交配2次及以上的占44%（单对放置）和67%(30对放置)。交配显著抑制雌蛾在次日暗期（交配后第1个暗期）的求偶活动,但在交配后第2个暗期基本恢复正常;在交配后第1个暗期,雌蛾腺体中主要组分Z9-14:Ac的含量和比例较对照雌蛾显著升高,其他组分无显著变化。在20-35℃的饲养温度范围内,雌蛾腺体内16:Ac的含量在35℃时最高,在20℃时未能检测出;各测试温度下Z11-16:Ac的含量相差不显著;其余5种组分均在25℃时最高;主要活性组分Z7-12:Ac和Z9-14:Ac在35℃时显著降低。饲养温度对腺体内各组分的相对比例也有较大影响,12:Ac、Z11-14:Ac、Z11-16:Ac和16:Ac所占比例均在30-35℃时较高,而Z9-14:Ac则在20-25℃时较高。不同饲养温度所得雄蛾对腺体主要组分的触角电位反应无显著差异。【结论】交配显著抑制草地贪夜蛾雌蛾在次日的求偶行为;25℃饲养条件最适宜雌蛾腺体内性信息素等组分的合成。     

Ultrastructure of dissociated neurones from pupae of Spodoptera littoralis boisduval (Lepidoptera: Noctuidae) growing in culture

The aims of the present investigation were to determine whether pupal neurones could be grown in culture and maintained for sufficient periods of time to allow synapse formation, so that they could be used for pharmacological studies. Cells from dissociated nerve cords of pupae of Spodoptera littoralis (Lepidoptera : Noctuidae) were grown in vitro and their ultrastructure examined as part of a long-term study of the insect central nervous system (CNS). Over 90% of the cells in the cultures had ultrastructural characteristics that were typical of neurones, and these were also labelled by tetanus toxin. The neuronal cell bodies usually were spherical in cross-section with a prominent nucleus and nucleolus and cytoplasm containing numerous mitochondria, lysosomes, polysomes, and active Golgi bodies. After 24 hr in culture, the neurones produced long, axonal processes containing mitochondria and microtubules, and terminating in growth cones that contained large quantities of smooth-membraned cisternae. Nerve terminals commonly contained clear and dense-core vesicles often clustered around thickenings of the membrane. Preliminary electrophysiological experiments demonstrated an excitable component within the neuronal membrane.     

草地贪夜蛾的性信息素通讯研究进展

草地贪夜蛾Spodoptera frugiperda原产于美洲,具有长距离迁飞特性。该虫于1988年入侵欧洲,2016年入侵非洲,并引起巨大的粮食损失,2018年入侵亚洲,2019年从缅甸传入中国,并在短时间扩散至全国10多个省。草地贪夜蛾依赖性信息素通讯,实现雌雄间识别、交配和繁衍,为了深入研究草地贪夜蛾的性信息素通讯及其机制并开发更高效的预测预报和防治技术,本文综述了草地贪夜蛾性信息素通讯的研究现状。1967年首次报道草地贪夜蛾性信息素为顺9-十四乙酸酯,随后发现有不同的鉴定结果,1986年确认其性信息素由顺9-十四乙酸酯和顺7-十二乙酸酯两个组分组成,其比例为96.6∶3.4时表现出最强的引诱活性。除此而外,对不同地理种群的研究发现,草地贪夜蛾雌蛾的信息素腺体提取物还存在顺9-十二乙酸酯、顺11-十六乙酸酯和反7-十二乙酸酯,田间实验表明这些物质在性信息素通讯中也可发挥作用。根据分子标记和喜食寄主,草地贪夜蛾可分为玉米品系和水稻品系。两个品系在外部形态上无法区分,性信息素组分也相同,但在组分比例上存在一定的差异。两个品系间存在一定程度的生殖隔离,但室内可以正交和反交并产生可育的F1代,F1代的性信息素比例与母本的比较相似。关于草地贪夜蛾雄性对性信息素的感受机制方面研究较少,仅见有感器形态的鉴定和对性信息素组分的触角电位反应研究的报道。根据目前草地贪夜蛾在我国的发生情况及其性信息素通讯机制的研究现状,我们建议尽快开展以下研究：(1)鉴定草地贪夜蛾我国入侵种群的雌性性信息素,尽快用于其种群动态监测及防治;(2)研究草地贪夜蛾雄性对性信息素的嗅觉编码机制;(3)研究草地贪夜蛾两个品系的行为隔离程度及其演化结局。     

Sex pheromone blend of Manduca sexta: Responses of central olfactory interneurons to antennal stimulation in male moths

Recently, chemical analysis of solvent rinses of the external surfaces of pheromone glands from female Manduca sexta revealed a blend of 12 aldehydes, including the previously identified sex pheromone component, (E,Z)-10,12-hexadecadienal (bombykal). Previous electrophysiological studies showed that olfactory (deutocerebral) interneurons in the antennal lobes of males exhibited a wide range of responsiveness to pheromonal stimulation of the ipsilateral antenna. These experiments were performed with crude extracts of pheromone glands as well as two synthetic compounds: the major pheromone component, bombykal, and (E,Z)-11,13-pentadecadienal, a mimic of a second component of the female's pheromone blend. Using intracellular methods, we have now reexamined similar olfactory interneurons, using each of the 12 chemically identified components as well as synthetic blends of various combinations of them. Eight of the 12 components isolated from female glands elicited some form of response in olfactory interneurons in males. In accordance with biochemical and behavioral data, the most potent are bombykal and two trienals, (E,E,E)- and (E,E,Z)-10,12,14-hexadecatrienal. We also conclude that the C₁₅ dienal is selective for one of the trienal receptors on the antenna, but is much less potent than the natural trienal stimulant.     

Diurnal rhythm in expression and release of yolk protein in the testis of Spodoptera littoralis (Lepidoptera: Noctuidae)

Circadian clocks (oscillators) regulate multiple life functions in insects. The circadian system located in the male reproductive tract of Lepidoptera is one of the best characterized peripheral oscillators in insects. Our previous research on the cotton leafworm, Spodoptera littoralis, demonstrated that this oscillator controls the rhythm of sperm release from the testis and coordinates sperm maturation in the upper vas deferens (UVD). We demonstrated previously that a protein that functions as yolk protein in females is also produced in cyst cells surrounding sperm bundles in the testis, and is released into the UVD. Here, we investigated the temporal expression of the yolk protein 2 (yp2) gene at the mRNA and protein level in the testis of S. littoralis, and inquired whether their expression is regulated by PER-based molecular oscillator. We describe a circadian rhythm of YP2 accumulation in the UVD seminal fluid, where this protein interacts with sperm in a circadian fashion. However, we also demonstrate that yp2 mRNA and YP2 protein levels within cyst cells show only a diurnal rhythm in light/dark (LD) cycles. These rhythms do not persist in constant darkness (DD), suggesting that they are non-circadian. Interestingly, the per gene mRNA and protein levels in cyst cells are rhythmic in LD but not in DD. Nevertheless, per appears to be involved in the diurnal timing of YP2 protein accumulation in cyst cells.     

Quadriflagellar primary spermatocytes in the cotton leafworm,Spodoptera littoralis (Boisd.) (Noctuidae,Lepidoptera)

Summary The surface morphology of primary spermatocytes from testicular cysts of the last instar larvae of Spodoptera littoralis was examined by scanning electron microscopy (SEM). At this stage, each primary spermatocyte possesses four developing flagella, directed towards the lumen of the cyst. The identical length of flagella in all primary spermatocytes from a single cyst indicates that the initiation and rate of flagellar growth are synchronized. Some asynchrony can, however, be observed in the translocation of flagella to secondary spermatocytes during the first meiotic division.