Variation in pea aphid population development in three different habitats

Abstract.

• 1 Seasonal population growth rates for the pea aphid, Acyrthosiphon pisum Harris, were determined in three different host plant habitats; alfalfa, Medicago sativa (L.), clover, Trifolium pratense (L.), and peas, Pisum sativum (L.); over four years and eight places. It was possible to estimate a common intrinsic rate of increase for each host plant habitat.
• 2 An analysis of the relative influence of temporal, spatial and host plant habitat variation showed that the host plant habitat was most important in determining the growth rates of the populations, both in rate of build-up and decline.
• 3 Patterns of alate production in the three different habitats differed substantially between the annual peas and the two perennial legumes. During the summer, alate production was large and rapid in peas and remained low and constant in clover and alfalfa
• 4 Parasitism was highest in peas. The species composition of parasitoids differed between crops.
• 5 Aphids in annual peas had a higher intrinsic rate of increase and a faster rate of decline than in the two perennial legumes. This explains the presence of both migratory and sedentary forms among pea aphids.

     

寄主植物对瓜蚜酯酶活性及其耐药性的影响

寄主植物对瓜蚜无翅胎生雌蚜体重、体色、体内酯酶活性均有明显影响。取食笋瓜、南瓜、瓠子、黄瓜和冬瓜的瓜蚜,体重依次增加,体色渐深,而体内羧酸酯酶活性依次渐低。取食不同奇主植物的瓜蚜对杀虫剂的耐药性与其体内酯酶活性呈正相关。瓜蚜体内羧酸酯酶活性（X）与乐果对瓜蚜的LC50（Y）附会Y=8．3827X－67．8530（r=0．952）,与功夫菊酯对瓜蚜的LC50（Y）附合Y=1．040X－28．89（r=0．985）的线性关系。     

Responses of the Circadian Locomotor Activity Rhythm of Mus Booduga to Shifts in LD Schedules

The responses of the field mouse Mus booduga to shifts in schedules of LD cycles were monitored and the results were interpreted with the help of a PRC constructed for the same species. The results reveal that, M. booduga reentrained faster with a lesser number of transients after delay shifts than advance shifts, thus exhibiting “asymmetry effect.” A positive correlation was observed between the number of transients and the number of hours of shift. In most of the shifts, the sign of the transients (negative for delaying transients and positive for advancing transients) coincided with the direction of the shift. Interestingly, 11 and 12 h of advance shifting resulted in delaying transients. An 11-h advance shift can also be interpreted as a 13-h delay. Reentrainment through delaying transients is faster as compared to reentrainment through advancing transients. Thus, this animal might have taken a “shorter route,” as proved by the fact that an 11-h advance shift has evoked delaying transients. But a 13-h advance shift evoked only advancing transients. This prompts us to speculate that there may be a “phase jump” in M. booduga. Further, irrespective of whether L or D has been doubled in a 12-h shift, both evoked only delaying transients.     

Sex ratio regulation in the waspEupelmus vuilleti (crwf.), an ectoparasitoid on bean weevil larvae (Hymenoptera: Pteromalidae)

In Africa, the seeds and/or pods ofVigna unguiculata andVigna radiata (Papilionacea) are attacked in fields and storage structures by bruchid beetlesCallosobruchus maculatus andBruchidius atrolineatus, on which parasitoid communities can develop. One of these parasitoids is the solitary ectoparasitoidEupelmus vuilleti (Eupelmidae). The storage conditions ofV. unguiculata andV. radiata favor the overlapping of all host stages during several months. These conditions suggest that female parasitoids would vary the sex ratio of their offspring according to the different sizes or developmental stages of hosts. The sex ratio ofE. vuilleti was strongly related to the developmental stage of the hostC. maculatus. Under our experimental conditions, where superparasitism is rare, the proportion of daughters varied between 5 and 25% on the third larval stage but reached 70 to 90% on the pupae. The increase in the proportion of daughters was also observed in the absence of superparasitism. In this case, there was an absolute coincidence between the sex ratio of eggs laid and that of emerged adults. Manipulation of the sex of the egg by the females seems to take place at the time of the egg's fertilization. The relation between host weight and egg sex showed that the male eggs are preferentially laid on lighter host larvae and the female eggs on heavier ones.     

Biology ofTrichogramma ostriniae (Hym.: trichogrammatidae) reared onOstrinia nubilalis (Lep.: pyralidae) and survey for additional hosts

Trichogramma ostriniae has been identified as a candidate for biological control ofOstrinia nubilalis. As little was known about the biology of this parasitoid when reared onO. nubilalis, we undertook experiments to quantify biological parameters important to mass-rearing and ase ofT. ostriniae. When reared continuously onO. nubilalis, femaleT. ostriniae on average lived 2.7 days and produced 24 progeny. Continuous access to honey resulted in a four-fold increase in longevity and fecundity and a significant increase in the percentage of females parasitizing eggs. Rates of fecundity and parasitism decreased with age of female. Likewise, emergence rates and percentage of female progeny decreased with age of parental female.T. ostriniae successfully parasitizedO. nubilalis eggs until the blackhead stage. Most parasitism of eggs and eclosion of adults occurred during the first half of photophase. Eggs of 13 Lepidopterans were parasitized byT. ostriniae. Eggs of the Noctuidae, Pyralidae, and Plutellidae experienced higher levels of parasitism than others tested.T. ostriniae appears to be similar to other species ofTrichogramma in several respects and does not possess any characteristics that limit its potential for mass rearing and use for augmentative biological control ofO. nubilalis.     

Factors influencing host choice of the honey bee parasite Varroa jacobsoni Oud

Reproducing Varroa jacobsoni obtained from brood cells of Apis mellifera L. with 13–16 day old bees (pupae) and Varroa mites kept on adult bees for at least 8 days were simultaneously tested for their choice in three host types. Comparisons were made of attractiveness of Varroa jacobsoni to nurse bees, pollen foragers as to larvae from nearly capped brood cells. Host choices were observed in Petri dishes and in an Y-shaped olfactometer. Varroa jacobsoni obtained from capped brood cells showed a stronger preference for nurse bees in Petri dish simultaneous choice tests with pollen foragers or larvae than did mites which were previously kept on adult bees. In olfactometer simultaneous choice tests, the two mite test groups showed no clear difference in preferences for bees of different ages. The preference of Varroa jacobsoni for bees of different ages is therefore not only influenced by host factors but also by intrinsic factors in female mites that depend on the mite's reproductive stage.     

Effects of genetic and environmental host plant variation on the susceptibility of two noctuids toBacillus thuringiensis

TwoApium graveolens var.rapaceum (L.) cultivars that differ in their suitability for the survival and growth ofSpodoptera exigua (Hübner) andTrichoplusia ni (Hübner) were used to examine the effect of genetic and seasonal environmental variation in host plant suitability on the efficacy ofBacillus thuringiensis subsp.kurstaki (Berliner). The effects of host plant genotype andB. thuringiensis were generally independent, so thatB. thuringiensis efficacy was greatest on the resistant host plant cultivar. Host plant suitability varied within growing season for both insect species but, while host plant suitability decreased with increasing plant age forT. ni, the response ofS. exigua to plant age was not as clear. Within season variation in host plant suitability affectedB. thuringiensis efficacy and the interaction betweenB. thuringiensis and host plant cultivar forS. exigua but not forT. ni. Soluble protein and Folin-Denis phenolic concentrations of host plant tissue were not correlated with changes in host plant suitability to either insect species.     

HOST SPECIFICITY IN THE RED ALGAL PARASITES BOSTRYCHIOCOLAX AUSTRALIS AND DAWSONIOCOLAX BOSTRYCHIAE (CHOREOCOLACACEAE,RHODOPHYTA)1

The determinants of host specificity, which are poorly understood in red algal parasites, were studied in the red algal parasites Bostrychiocolax australis Zuccarello et West and Dawsoniocolax bostrychiae (Joly et Yamaguishi-Tomita) Joly et Yamaguishi-Tomita. Culture studies were performed to determine host range, sites of host resistance, and genetics of transmission of resistance. Both species parasitize Bostrychia radicans (Montagne) Montagne, whereas Bostrychiocolax australis also parasitizes Bostrychia moritziana (Sonder ex Kützing) J. Agardh and Stictosiphonia kelanensis (Grunow ex Post) R. J. King et Puttock. Isolates of B. radicans resistant to both parasites were found worldwide, often within the same population as susceptible isolates. On resistant Bostrychia species and isolates, specificity was manifested at three stages: 1) host penetration, in which the spore germ peg failed to penetrate the host cuticle/wall; 2) parasite–host cell fusion, in which the fusion cell died and the parasite died; and 3) growth, in which parasites grew but soon died; parasites rarely reproduced and infections did not continue in culture. Resistance to parasite infection was usually transmitted as a dominant trait and did not segregate as a single locus during meiosis. In certain crosses, transmission of resistance was non-mendelian.     

Endocytosis of 1,3-β-glucans by broad bean cells at the penetration site of the cowpea rust fungus (haploid stage)

Te penetration hypha of basidiospore-derived infection structures of the cowpea rust fungus (Uromyces vignae Barclay) in epidermal cells of the nonhost, broad bean (Vicia faba L.), was studied with the electron microscope after high-pressure freezing and freeze substitution. After fungal invasion of the epidermis, a plug in the penetration hypha separated the infection structures on the cuticle from the intraepidermal vesicle of the fungus. The plug and the fungal cell wall reacted with a polyclonal 1,3-β-glucan antibody. The plug in the haploid stage seems to have a task similar to the septum formed in the diploid stage of the fungus. Around the penetration hypha, the plant wall stained darkly and a papilla was deposited by the plant. In the papilla, 1,3-β-glucans were labelled by a monoclonal and a polyclonal antibody. In the infected epidermal cell, clathrin-coated pits, coated vesicles, partially coated reticula and multivesicular bodies were found. The contents of the coated pits, coated vesicles, partially coated reticula and multivesicular bodies bound to monoclonal and polyclonal 1,3-β-glucan antibodies. Accumulation and uptake of this paramural material into the plant cell by endocytosis is concentrated at the fungal penetration site. It may influence the host-parasite interaction.     

Identification of N-terminal helix capping boxes by means of 13C chemical shifts

Summary We have examined the ¹³C and ¹³C chemical shifts of a number of proteins and found that their values at the N-terminal end of a helix provide a good predictor for the presence of a capping box. A capping box consists of a hydrogen-bonded cycle of four amino acids in which the side chain of the N-cap residue forms a hydrogen bond with the backbone amide of the N3 residue, whose side chain in turn may accept a hydrogen bond from the amide of the N-cap residue. The N-cap residue exhibits characteristic values for its backbone torsion angles, with and clustering around 94±15° and 167±5°, respectively. This is manifested by a 1–2 ppm upfield shift of the ¹³C resonance and a 1–4 ppm downfield shift of the ¹³C resonance, relative to their random coil values, and is mainly associated with the unusually large value of . The residues following the N-cap residue exhibit downfield shifts of 1–3 ppm for the ¹³C resonances and small upfield shifts for the ¹³C ones, typical of an -helix.