Temperature modulation of behavioural thresholds controlling male moth sex pheromone response specificity

ABSTRACT. The response specificity of male Oriental fruit moths, Grapholita molesta (Busck) and pink bollworm moths, Pectinophora gossypiella (Saunders), to different blends and doses of pheromone is altered dramatically by temperature. When acclimated and tested in a flight tunnel at 20^oC males of both species exhibit a high degree of specificity, with peak response levels occurring to a narrow range of blend-dose combinations close to the natural blend. When tested at 26^oC, however, males exhibit a significantly lower degree of specificity, with peak response occurring to a broader range of treatments. The change in response specificity results from shifts in behavioural threshold effects influencing plume orientation and initiation of upwind flight, as well as from arrestment of upwind flight, occurring later in the flight sequence. The observed changes in male behaviour suggest that the effect of temperature is directly on neural pathways involved in the perception of odour, and not simply the result of an increase in motor activity or a significant change in the release rate of the pheromone. The results support the threshold hypothesis for pheromone perception (Roelofs, 1978) as a general principle in the Lepidoptera, but also show that the degree of response specificity can be significantly affected by temperature.     

Isolation and characterization of polymorphic microsatellite loci from the pink bollworm Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae)

Thirteen polymorphic microsatellite markers were developed from an enriched partial genomic library for the pink bollworm, Pectinophora gossypiella (Saunders), one of the most important cotton pests in the world. The total number of alleles ranged from two to 12 for a sample of 50 individuals and the expected heterozygosity at these loci ranged from 0.042 to 0.830. Although the presence of null alleles in some loci is suspected, these polymorphic markers are likely to provide useful tools for the population genetic studies of this species.     

Evolutionary trade-offs of insect resistance to Bacillus thuringiensis crops: fitness cost affecting paternity

Evolution of resistance to insecticides provides a useful model for examining fitness trade-offs associated with adaptation to stress. Here, we examined male reproductive costs in pink bollworm (Pectinophora gossypiella) resistant to an insecticidal protein of Bacillus thuringiensis (Bt) produced by transgenic cotton, using contrasts between two pairs of related susceptible and resistant strains. Without competition for access to females, no costs affecting reproductive success of resistant males were observed. Resistant and susceptible males had similar mating frequency and fertility. Additionally, fecundity of females mated to resistant and susceptible males was comparable. In competition for matings with virgin females, resistant and susceptible males had comparable success in one strain, whereas susceptible males tended to mate more often than resistant males in the other. However, irrespective of strain origin, resistant males that mated first sired significantly less offspring than susceptible males that mated first. The reduced first-male paternity in resistant males may involve reduced sperm precedence caused by mutations in a cadherin gene linked with resistance to Bt cotton.     

The diversity of Bt resistance genes in species of Lepidoptera

Although the mode of action of Cry1A toxins produced by Bacillus thuringiensis is fairly well understood, knowledge of the molecular mechanisms by which lepidopteran species have evolved resistance to them is still in its infancy. The most common type of resistance has been called "Mode 1" and is characterized by recessive inheritance, >500-fold resistance to and reduced binding by at least one Cry1A toxin, and negligible cross-resistance to Cry1C. In three lepidopteran species, Heliothis virescens, Pectinophora gossypiella, and Helicoverpa armigera, Mode 1 resistance is caused by mutations in a toxin-binding 12-cadherin-domain protein expressed in the larval midgut. These mutations all interrupt the primary sequence of the protein and prevent its normal localization in the membrane, presumably removing a major toxic binding target of the Cry1A toxins. In Plutella xylostella, however, Mode 1 resistance appears to be caused by a different genetic mechanism, as Cry1A resistance is unlinked to the cadherin gene. Mapping studies in H. virescens have detected an additional major Cry1A resistance gene, which on the basis of comparative linkage mapping is distinct from the one in P. xylostella. An additional resistance mechanism supported by genetic data involves a protoxin-processing protease in Plodia interpunctella, and this is likely to be different from the genes mapped in Plutella and Heliothis. Thus, resistance to Cry1A toxins in species of Lepidoptera has a complex genetic basis, with at least four distinct, major resistance genes of which three are mapped in one or more species. The connection between resistance genes and the mechanisms they encode remains a challenging task to elucidate.     

Antennal resolution of pulsed pheromone plumes in three moth species

Male antennae of Cadra cautella,Pectinophora gossypiella, and Spodoptera exigua were presented with 20-ms-duration pulses of their two-component pheromone at rates of 1 to 33 Hz. Fourier analyses of electroantennograms resolved the temporal structure of trains of pheromone filaments delivered at up to 33 Hz for C. cautella and S. exigua and 25 Hz for P. gossypiella. Pheromone components tested separately for each species were generally equivalent in filament resolution to complete blends. Ambient temperatures of 18, 23 and 28 °C affected filament resolution only slightly, with poorer ability to discriminate rapidly pulsed signals at 18 °C. The question of how, or indeed if, such frequencies are conserved beyond the peripheral nervous system, remains.     

棉红铃虫自然种群的生命统计特征

1978-1988年,在湖北省江汉平原棉区,用编制特定年龄生命表的方法,研究棉红铃虫Pectin ophora gossypiella(Saunders),第1至3代的自然种群生命统计特征值。 世代存活率(占)为3.23,4.01和1.46;各虫态发育阶段(X)与相应阶段存活率的关系为：y₁=61.66e-0.58s、Y₂= 142.47e^-0.73s、 y₃=146.68e^-0.80s种群鹃势指数(I)：1.12、2.03和0.45;每雌蛾平均及最高产卵量：35(253)、51(235)、31(293)粒;自然内禀增长率(r')为0.0390、0.0403和0.0026;净增殖率?：4.39、4.43和2.04;周限增长率(兄)：1.0398、1.0411和1.0026;世代长度(T)：38、37和276日;种群加倍时间(t)18、l7和26,天。上列十个生命统计值已成为组建棉红铃虫的计算机辅助决策模型所必须的基质。 第二代是全年的关键世代,各代钻蛀期的幼虫数及越冬期的幼虫数是影响下一世代或次年种群数量的关键虫态,钻蛀期幼虫的自然死亡是致死的主导因子。     

Comparative studies of predation among feral,commercially-purchased,and laboratory-reared predators

The predatory activities of commercially-purchased adult Hippodamia convergens Guérin-Méneville and two laboratory-reared strains of adult Geocoris punctipes (Say) were compared with their feral counterparts. In single prey choice feeding tests, commercially-purchased and feral H. convergens were provided copious amounts of silverleaf whitefly, Bemisia argentifolii Bellows & Perring adults or eggs of pink bollworm, Pectinophora gossypiella (Saunders). Commercially-purchased H. convergens devoured more pink bollworm eggs and at a faster rate than the feral H. convergens. In contrast, feral H. convergens consumed more adult whiteflies and at a faster rate than commercial H. convergens. In multiple feeding choice tests, two distinctly different laboratory-reared strains and feral G. punctipes were provided a cotton leaf disk containing copious amounts of silverleaf whitefly eggs, nymphs, and adults. Virtually no predation was observed on whitefly eggs, but both laboratory strains of G. punctipes fed on more whitefly nymphs and adults than the feral G. punctipes. Moreover, both of the laboratory strains had a significantly faster feeding rate on adult whiteflies and spent significantly less time feeding on plant tissue than the feral strain. These results suggest that the augmentative biological control candidates retained their ability to prey on these selected prey items, even after being displaced from their overwintering site (H. convergens) or being reared in captivity (G. punctipes) for over 40 generations. Handling editor: Patrick De Clercq. This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a recommendation for its use by the USDA.     

不同世代棉红铃虫性信息素的释放速率及两种组分的比例

本文采用单个活雌蛾腺体的性信息素气体收集技术,对不同世代及实验室人工饲养的CZ品系棉红铃虫Pectinophora gossypiella(Saunders)性信息素释放速率作定量分析.结果表明,各类虫源的性信息素释放速率具有明显差异;而棉红铃虫性信息素中两种组分顺,顺-7,11-十六碳二烯醇醋酸酯和顺,反-7,11-十六碳二烯醇醋酸酯的比例保持在54.8±1.2:45.2±1.2的范围;取食相同的同一代棉红铃虫的雌蛹重与其成虫的性信息素释放速率具有正相关性.     

A new RNA picorna — Like virus in the cotton pink bollwormPectinophora gossypiella (Lep.: Gelechiidae) in Egypt

A new virus infecting the pink bollwormPectinophora gossypiella has been detected and purified from dead larvae collected from naturally infested cotton fields. The purified icosahedric virions measured 27±1 nm in diameter and contained RNA genome. Three capsid proteins of 31.7, 32.6 and 47.4 Kd have been separated on polyacrylamide gel. The purified virus was not highly infectious to the host larvae revealed while the pupal period survived from infected larvae was significantly prolonged. The virus particles infecting the midgut cells are grouped in paracrystallin arrays. The virus was vertically transmitted through infected adults. The main characteristics of this virus place are quite relative to the Picornavirus group.

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Résumé Un nouveau virus infectant le ver rose du cotonnier,Pectinophora gossypiella, a été isolé et purifié à partir de larves mortes récoltées en champ de coton. Les virions purifiés de 27±1 nm de diamètre, ont une forme icosaédrique et contiennent un génome à ARN. Trois protéines capsidaires de 31,7, 32,6 et 47,4 Kd ont été trouvées dans les virions. Le virus purifié n'est pas hautement infectieux pour les larves, cependant la durée du stade chrysalide est supérieure chez les lots infectés artificiellement. Dans les tissues atteints, les virions sont dispersés dans le cytoplasme des cellules de l'intestin ou bien groupés en amas paracrystallins de même type que chez d'autres insectes infectés avec des picornavirus. Les adultes malades transmettent ce virus à leur descendance. Par sa forme, sa taille et ses caractéristiques chimiques, ce virus libre peut être placé près des Picornavirus d'insectes.

     

Selection for altered pheromone-component ratios in the pink bollworm moth,Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Female pink bollworm moths, Pectinophora gossypiella(Saunders), were selected for altered component ratios of the long-distance sex pheromone, (Z, E)-and (Z, Z)-7,11- hexadecadienyl acetate. Selection for 12 generations increased the mean (± SD) percentage of the (Z, E)isomer from 42.9 ± 1.0 in the parental generation to 48.2 ± 1.2. Although statistically significant, a change of this magnitude may be transparent to males because of their relatively broad response spectrum. Selection for a lower percentage of the (Z, E)isomer yielded no change in the mean pheromone ratio. The total amount of pheromone produced declined in both selected lines. In the line selected for females producing a high percentage of the (Z, E)isomer, the duration of wing fanning by males to high (Z, E)blends was elevated.