麦长管蚜唾液中几种酶的鉴定、活力测定与功能分析

用Parafilm膜夹营养液法,以两种食料介质饲喂麦长管蚜Macrosiphum avenae 3龄若蚜并收集其唾液,对唾液中的酶类进行了鉴定、活力测定和功能分析。结果表明,在20%蔗糖介质提取液中,鉴定有果胶酶、多酚氧化酶和纤维素酶; 在水介质提取液中鉴定有纤维素酶; 两种介质提取液中都未鉴定出过氧化物酶。酶活力测定结果表明, 在20%蔗糖介质提取液中, 每30头蚜虫分泌的果胶酶、多酚氧化酶和纤维素酶的酶活力分别为2.59×10^-3 U/g、7×10^-3 U/g和7.89×10^-3 U/g; 在水介质提取液中,纤维素酶活力为3.68×10^-3 U/g。行为反应试验结果表明,果胶酶处理麦苗的挥发物组分能引起麦长管蚜寄生性天敌燕麦蚜茧蜂Aphidius avenae和捕食性天敌七星瓢虫Coccinella septempunctata 的嗅觉偏好反应,因此,果胶酶在麦长管蚜取食诱导小麦植株的间接防御反应中具有重要作用。     

温度对烟蚜茧蜂发育、生殖的影响

在恒汨１０、１５、２０、２５和３０℃实验条件下,测定了云南省玉溪地区烟蚜茧蜂（Ａｐｈｉｄｉｕｓ ｇｉｆｕｅｎｓｉｓ Ａｓｈｍｅａｄ）的发育历期和生殖力等生物学参数。结果显示,烟蚜茧蜂发育速率与温度的关系符合逻辑斯蒂曲线,即２５℃从卵至习化所需历期最短（１０．６７ｄ）,３０℃发育历期稍有延长（１１．６ｄ）。卵至羽化的发育起点温度为３．３℃,有效积温为２６６．０日度。烟蚜茧峰雌蜂羽化当天即可产卵,在产     

Effects of Wind Speed and Atmospheric Pressure on Mate Searching Behavior in the Aphid Parasitoid Aphidius nigripes (Hymenoptera: Aphidiidae)

The effects of wind speed and atmospheric pressure on male mate searching behavior, modulated by a female sex pheromone, were investigated in the aphid parasitoid Aphidius nigripes (Hymenoptera: Aphidiidae). Male A. nigripe generally did not reach females at wind speeds of 100 cm/sec, as the majority of individuals taking flight in the pheromone plume (81.8%) were unable to sustain upwind flight. At lower wind velocities, male responsiveness to females generally decreased with distance from the source. However, wind speeds approaching the upper threshold (100 cm/sec) tended to eliminate this distance effect. Therefore, there appears to be a trade-off between the need for higher wind speeds to detect the pheromone source from long distances, and a reduction in male flight capacity as wind velocity increases. Our results also indicate that chemical communication in A. nigripes could be affected by variations in atmospheric pressure, as we observed a relationship between pressure fluctuations in the 24 hr prior to testing and male responsiveness to females. The importance of these abiotic factors on mate searching behavior is discussed within the context of the reproductive biology of A. nigripes.     

不同营养层次挥发物对燕麦蚜茧蜂寄主搜寻行为的影响

“Ｙ”型管嗅觉计及风洞测定试验明,小麦植株,麦长管蚜（Sitobion avenae),禾谷缢管蚜（Rhopalosiphum padi)对燕麦蚜蜂（Aphidius avenae)雌蜂的吸引作用较小,而有蚜植株及蚜害植株对其吸引作用较大,并以麦长管蚜有蚜植株的吸引作用最强,尽管该蜂对禾谷缢管蚜的寄生率极你,工作量 由其危害诱导产生的挥发性信息化僵物对该蜂仍具有较强的吸引作用,GC－MS鉴定结果表明,麦蚜取食诱导的挥发性信息化合物主要是2－莰烯,6－甲基－5－已烯－2－酮,顺－3－已酰酸酯有水杨酸甲酯,其中6－甲基－5－已烯－2－酮和6－甲基－5－已烯－2－醇对燕麦蚜划蜂的吸引作用最强,水杨酸酯无明显吸引作用。     

Foraging patterns of two aphid parasitoids, Lysiphlebus testaceipes and Aphidius colemani on banana

The searching behaviour of two aphid parasitoids, Lysiphlebus testaceipes (Cresson) and Aphidius colemani Viereck (Hymenoptera, Aphidiidae), was analysed. Both species searched banana plants (Musa spec.) infested with the banana aphid Pentalonia nigronervosa Coq. in a different way. L. testaceipes restricted its search to open plant structures and avoided concealed areas. A. colemani partitioned its time spent on the plant between open and concealed areas. This general pattern was independent of aphid colony size and was also observed in the absence of aphids. As a consequence of these searching tactics, the borders of a host patch differed for both parasitoid species. For L. testaceipes, the patch consisted only of aphids feeding on open structures, while it comprised the whole aphid colony for A. colemani. The observed searching patterns resulted in a different exploitation of the aphid colonies.

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Zusammenfassung Eine Analyse des Suchverhaltens der beiden Blattlausparasitoide Lysiphlebus testaceipes (Cresson) and Aphidius colemani Viereck zeigte, daß beide Arten Bananenpflanzen (Musa spec.), die von der Bananenblattlaus Pentalonia nigronervosa Coq. befallen waren, auf unterschiedliche Weise absuchten. L. testaceipes beschränkte seine Wirtssuche auf frei zugängliche Pflanzenteile und vermied ein Eindringen in geschützte Pflanzenstruckturen. Dagegen hielt sich A. colemani gleichermaßen häufig auf offenen und in geschützten Pflanzenteilen auf. Dieses generelle Suchmuster war unabängig von der Blattlauskoloniegröß und wurde auch beim Fehlen von Wirten beobachtet. Als Konsequenz aus diesem unterschiedlichen Suchverhalten ergaben sich verschiedene Patchgrenzen für beide Parasitoide. Für L. testaceipes bestand der Patch nur aus Blattläusen, die an frei zugänglichen Pflanzenstrukturen saugten, während der Patch für A. colemani alle Blattläuse einschließlich der Tiere umfaßte, die sich in geschützten Pflanzenteilen aufhielten. Damit führte dieses unterschiedliche Suchverhalten beider Parasitoidenarten zu einer unterschiedlichen Ausnutzung der Blattlauskolonien.

     

Soil community composition drives aboveground plant–herbivore–parasitoid interactions

Soil organisms can influence higher trophic level aboveground organisms, but only very few studies have considered such effects. We manipulated soil community composition of model grassland ecosystems by introducing nematode communities, microorganisms, neither or both groups. Above ground, aphids ( Rhopalosiphum padi ) and parasitoids ( Aphidius colemani ) were introduced, and we measured individual performance and population dynamics of plants, aphids and parasitoids. In microcosms with nematode inoculations either with or without microorganism inoculation, aphids offspring production was significantly reduced by 31%. Aphid populations on both host plants Agrostis capillaris and Anthoxanthum odoratum were lowest in microcosms with combined nematode and microorganism inoculations. Opposite results were found for parasitoids. While the number of emerged parasitoids did not differ between treatments, parasitoid mortality and the proportion of males were significantly lower in microcosms with nematode and microorganism inoculations. Parasitized aphids were significantly larger in microcosms with nematodes inoculated. Plant biomass did not differ, but in the preferred host plant A. odoratum , foliar phenolic content was reduced in the presence of nematodes, and also the concentration of amino acids in the phloem. This study shows that the composition of the soil community matters for aboveground multitrophic interactions.     

Distribution of superparasitization in the aphid parasite, Aphidius sonchi

The frequency distributions of eggs of the aphid parasite, Aphidius sonchi Marshall, offered 25, 50, 100 or 200 aphids per flowering shoot per female per day were determined for three consecutive days. The numbers of eggs within aphids were neither consistently overdispersed nor underdispersed, except at the two lower levels of host availability on the first day when the parasites laid large numbers of eggs into a small proportion of the hosts. These results suggest that female A. sonchi do not avoid ovipositing in already parasitized hosts under these conditions.

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Résumé Pendant trois jours consécutifs, on a étudié la fréquence de distribution des oeufs d'Aphidius sonchi Marshall, par femelle et par jour, en présence de 25, 50, 100 et 200 pucerons par rameau florifère. Les effectifs d'oeufs dans les pucerons ne révèlent ni une sur-dispersion, ni une sous-dispersion, sauf aux deux plus faibles concentrations d'hôtes, où les parasites ont pondu le premier jour un plus grand nombre d'oeufs dans une faible proportion d'hôtes. Ces résultats suggèrent que les femelles d'A. sonchi, dans ces conditions, n'évitent pas de pondre dans des hôtes déjà parasités.

     

Biology of Aphidius rhopalosiphi, a parasitoid of cereal aphids

Summary Aphidius rhopalosiphi produced 212 offspring on average but in one case 509 deposited eggs were found. Superparasitization occurred but the frequency distribution of parasitoid larvae in aphids differed significantly from random, indicating a certain degree of host discrimination. Average life span of adults was 13.1 days and sex ratio was 1:1. It changed in time among successively produced offspring.Handling time was about 2 sec and was somewhat longer in the fourth instar than in the second. Second and third aphid instars were preferred for oviposition. Functional response was sigmoid and at an aphid density of 100 aphids per cage percentage parasitization decreased.

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Résumé Nous avons examiné quelques aspects des relations entre le parasitoïde Aphidius rhopalosiphi et son hôte Sitobion avenae. La fécondité potentielle à l'émergence (144 ufs) était inférieure à la fécondité réalisée: nombre de pucerons momifiés (212). La plupart des ufs étaient pondus dans la première semaine de la vie imaginale (fig. 1). Le super-parasi-tisme s'est produit dans les conditions expérimentales, mais la distribution des larves (fig. 2) s'écartait souvent de la distribution au hasard, ce qui indiquait une certaine discrimination parmi les hôtes.La longévité moyenne était de 13,1 jours et le maximum de 23 jours. Le taux sexuel (fig. 3) pour l'ensemble de la descendance était 1/1, mais changeait dans le temps. Après le premier jour de ponte, plus de femelles que de mâles étaient obtenues; mais après 6 jours, il n'y avait presque plus que des mâles.Le taux de rencontre des aphides et des parasitoïdes augmentait avec la taille (fig. 4a). Le temps de prospection de l'hôte était en moyenne de 2 secondes, mais dans certains cas il atteignait 10 secondes ou plus. La proportion de rencontres efficaces était plus faible au 4ème stade (fig. 4b). Il n'y avait pas de différence significative dans le nombre de larves de parasitoïdes obtenues par rencontre pendant les stades 1 à 3 des pucerons, mais elle était significativement inférieure au 4ème stade par rapport au second. Les taux globaux de succès (taux de rencontre et nombre de larves formées par rencontre) étaient plus élevés aux 2ème stades des pucerons. La réponse fonctionnelle était sigmoïde (fig. 5).

     

Recognition of heterospecific parasitism: Competition between Aphidiid (Aphidius ervi) and Aphelinid (Aphelinus asychis) parasitoids of Aphids (Hymenoptera: Aphidiidae; Aphelinidae)

The solitary parasitoids Aphidius erviHaliday (Hymenoptera: Aphidiidae) and Aphelinus asychisWalker (Hymenoptera: Aphelinidae) attacked but generally did not oviposit in pea aphids parasitized by the other species. Wasps selectively oviposited in unparasitized hosts when given a choice. Host discrimination depended on the recognition of internal cues. Females of A. asychiseither could not recognize or ignored A. ervi'sexternal host marking pheromone. Under most conditions, A. ervisurvived in superparasitized hosts, killing competing A. asychislarvae by physical attack and possibly physiological suppression. The outcome of larval competition was not affected by oviposition sequence or age difference between larvae; A. asychissurvived only when it had substantially completed larval development before the host was superparasitized by A. ervi.It is suggested that competition for host resources incurs a cost, for the winner in terms of reduced size or increased development time and for the loser in terms of lost progeny and searching time. Consequently, heterospecific host discrimination can be functional. Internal, and probably general, cues enable wasps to recognize and avoid oviposition in hosts already parasitized by an unrelated species.