Embryogenesis and oögenesis in alate virginoparae,gynoparae, and oviparae of the aphid Myzus persicae, in relation to photoperiod

The study reports on the effects of prenatal and/or postnatal exposures to short-night or long-night conditions, and of crowding, on embryogenesis and oögenesis in alate virginoparae, gynoparae, and oviparae of a holocyclic strain of the green peach aphid, Myzus persicae, from Yakima, Washington State.In alate virginoparae raised at a density of 10–20 per radish seedling in a short-night regime (8 hr darkness per diem), 3–4 embryos occurred in each of their 10 ovarioles, when the aphids attained adulthood. More than 30 larvae were deposited by most of these alatae. However, in young adult gynoparae, raised at these densities in a long-night regime (15 hr darkness per diem), only one viable embryo (a presumptive ovipara) occurred per ovariole. The follicle containing this embryo was followed by 1–2 abnormal follicles in each ovariole, and the number of larvae deposited by a gynopara was generally less than 10. In young adult oviparae similarly raised under a long-night regime, only one egg typically occurred in each of their 10 ovarioles, and the eggs deposited by an ovipara (only after it had mated) generally numbered less than 10. Alate virginoparae and gynoparae contained an additional embryo in some of their ovarioles when these morphs were raised at a lower density (1–5 per plant).Presumptive gynoparae partially developed the reproductive features of alate virginoparae when transferred to a short-night regime at birth; the converse was true when presumptive alate virginoparae were transferred to a long-night regime early in larval life. Oviparae maintained in short nights from before birth developed the appearance of apterous virginoparae but still produced eggs rather than embryos. However, their oögenesis was enhanced and eggs (10–20) were deposited by them without prior mating. Under all regimes tested, oviparae were always deposited early in the larviposition sequence of their alate mothers, and the number of oviparae deposited never exceeded 15.The possible involvement of juvenile hormone in the regulation of these events and the ecological significance of the results are discussed.     

Fitness effects of two facultative endosymbiotic bacteria on the pea aphid,Acyrthosiphon pisum,and the blue alfalfa aphid,A. kondoi

The effects of two bacterial endosymbionts, designated PASS and PAR, were evaluated on the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera:Aphididae), in which they occur facultatively, and on the blue alfalfa aphid, A. kondoi Shinji, in which these bacteria have not been found in natural populations. Subclones of pea aphids and blue alfalfa aphids, derived from parent aphid clones that did not contain PASS or PAR, were infected with one or both bacteria, generating PASS- and/or PAR-positive subclones with minimal genetic differences from the parent clones. Under laboratory conditions at 20 °C, PAR consistently reduced the fecundity (by between 19 and 60%) of subclones derived from three different parent pea aphid clones on bur clover, Medicago hispida Gaertn. PAR had intermediate effects on pea aphids reared on sweet pea, Lathyrus odoratus L., and had no significant effect on pea aphids on alfalfa, Medicago sativa L. The effect of PASS was either neutral or negative, depending on parent clone as well as host plant. Also at 20 °C, PASS reduced fecundity (70–77%) and longevity (40–48%), and increased the age of first reproduction (by up to 1.5 days) of blue alfalfa aphid reared on alfalfa and clover. PAR had a less dramatic effect (e.g., 30–39% reduction in fecundity) on these traits of blue alfalfa aphid. In contrast, PAR and PASS increased the fitness of pea aphid subclones of one parent clone reared for three generations at 25 °C on each of the three test plants. Without facultative bacteria, fecundity of the parent clone was reduced to a mean total of < 6 offspring per adult at this elevated temperature, but with PASS or PAR, mean total fecundity of its subclones was > 35. However, this ameliorative effect of facultative bacteria at 25 °C was not found for two other sets of parent clones and their derived subclones. Alate production in pea aphids was significantly increased in large populations of two PASS- and PAR-positive subclones relative to their parent clones. Attempts to transmit PASS or PAR horizontally, i.e., from aphid to aphid via feeding on host plants (bur clover), were unsuccessful.     

黑龙江省哈尔滨地区吸虫塔有翅蚜种群动态

【目的】明确吸虫塔对作物蚜虫防控的指导意义,明确中国黑龙江省哈尔滨地区有翅蚜(和大豆蚜)的种群动态,为大豆蚜虫防控提供预警信息。【方法】2009至2012年通过吸虫塔监测哈尔滨地区有翅蚜及有翅大豆蚜动态结合当年田间大豆蚜动态调查。【结果】哈尔滨吸虫塔全年收集有翅蚜量为0.6~1.7万头不等。具1~3个高峰(不同年份有翅蚜发生高峰数量不同),高峰期时间1个月左右,位于7月中旬至10月中旬之间。周有翅蚜量达200头时预示着有翅蚜高峰期的到来,高峰期有翅蚜量可占年有翅蚜量的90%以上。同一地区不同年份有翅蚜高峰期时间不同。吸虫塔有翅大豆蚜亦具1~3个高峰期,时间位于当年有翅蚜的高峰期时间内,为短短的1周或几周,高峰期蚜量占全年采集有翅大豆蚜量的80%~95%。田间大豆蚜只存在一个高峰,2009、2010、2012年田间大豆蚜高峰期均与吸虫塔收集的大豆蚜高峰期相重叠,且峰值日期一致。【结论】吸虫塔可以很好地反应当年田间大豆蚜的种群动态,表现在高峰期及高峰点的预测,可为大豆蚜的预测预报提供预警信息。     

Host plant and crowding effects in the induction of alatae in the large pine aphid, Cinara pinea

Alate virginoparae of Cinara pinea occur on Scots pine trees only during June and early July, when population numbers are at their highest. Crowding experience during nymphal life promotes the development of winged adults, but only if the tree is in the stage of active shoot growth. Later in the season when shoots are mature, alatae are suppressed, irrespective of crowding. Changing daylength and temperature do not appear to influence alate production and maternal experience of crowding has no effect on the nymphal response. The possible nature of the host plant effect is discussed in the light of this and previous work.

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Résumé Les virginipares ailés de Cinara pinea apparais sent sur Pinus sylvestris L. uniquement en juin et au début juillet, quand les effectifs de la population sont au plus haut. Des expériences de surpeuplement pendant le dernier stade larvaire n'induisent le développement d'adultes ailés que si l'arbre est au stade où la croissance des pousses est active. Plus tard dans la saison, quand les pousses sont mûres, les ailés sont réprimés, quel que soit le surpeuplement. Les modifications de la longueur du jour et de la température ne semblent pas influencer la production d'ailés et le surpeuplement subi par les mères n'a pas d'effet sur la réponse des larves âgées. La nature de cet effet de la plante-hôte est envisagée à la lumière de cette étude et de travaux précédents.