Ontogenetic divergence of the phytoparasitic nematodesMacroposthonia nainitalensis andM. tenuiannulata (Criconematidae, tylenchia)

Promorphogenesis, egg cleavage, and gastrulation proceed inMacroposthonia nainitalensis similarly to other phytonematodes of the subclass Tylenchia. Before the onset of gastrulation, the greatest similarity was observed in a descendant of the micromere 2b, which separates macromeres of the third division. Deviations from the general line of development started in this species during embryonal organogenesis with the formation of an external epithelium with a special rough surface layer, which was absent in the embryos of other phytonematodes. In addition, during this period of acceleration, the digestive system developed, while peristaltic changes in body shape appeared at the tadpole stage. Later, somatic muscle development was enhanced in the first instar larvae ofM. nainitalensis, while in the second instar larvae ofMacroposthonia spp., somatic muscle cells were located at an acute angle to the longitudinal body axis. In addition, denticles—microchaetae—appeared in the second to fifth instar larvae of these nematodes. All of these features, which have not been observed in other phytonematodes of the subclass Tylenchia, help the peristaltic crawling ofMacroposthonia spp. In contrast to other Tylenchia, the musculocutaneous sac did not develop inMacroposthonia spp. However, there are similarities in the development of the digestive and genital systems.     

Development of the larval ovary in the moth, Plodia interpunctella

The morphogenesis of ovaries and the organization of germ cells within them were visualized during the larval stages of the moth, Plodia interpunctella. The germ cells were observed by utilizing confocal microscopy coupled with immuno-fluorescent staining for the alpha-crystallin protein 25 (alphaCP25). The alphaCP25 was previously shown to be specific to germ cells of pupae and adults, and this study shows that alphaCP25 is present in larval germ cells as well. A cluster of 28 germ cells that stain for alphaCP25 was found in the gonads of newly hatched first instar larvae. The founding germ cells became segregated into four clusters, most likely by somatic cell intrusion, around the beginning of the second instar. Division of the primary germ cells began by the end of the second instar and the formation of all cystoblasts appeared to be completed within the four ovarioles by the end of the third instar. Within the ovarioles of third instar larvae, the germ cells were organized with a distal cap of seven germ cells which was segregated from the majority of the germ cells. The main body of germ cells was arranged around a central germ cell-free core as a spiral. Divisions of the cystoblasts to form cystocyte clusters were nearly completed during the fourth (last) larval instar. These features suggest that the strategy to produce follicles in moths is fundamentally different from the fruitfly, Drosophila. It appears that during the initial stages of ovary development in P. interpunctella, the primary germ cells undergo stage-complete divisions that are completed prior to the onset of the next set of divisions, which results in a complete complement of follicles available by the time of adult eclosion, while in Drosophila the primary germ cell divisions are initiated in the adult stage, and follicles are produced individually as resources are available.     

Sensitivity differences displayed by Drosophila melanogaster larvae of different ages to the toxic effects of growth on media containing aflatoxin B1.

Using Drosophila melanogaster, the relative sensitivities of various larval stages to the toxic effects of growth on media supplemented with either 0.44 or 0.88 ppm aflatoxin B1 (AFB1) were determined. Two strains of fruit flies were tested: strain A-11 which is relatively resistant to AFB1 induced toxicity, and strain A-9 which is quite sensitive. Eggs, mid-first, mid-second and early-, mid- and late-third instar larvae were transferred onto AFB1 media and allowed to complete larval and pupal development and eclose as adults. At the 0.44 ppm concentration, strain A-11 showed no effect, while only first instar larvae of strain A-9 showed significant mortality rates for first instar larvae, but the A-9 larvae die at higher rates than the A-11 larvae. In addition, second and third instar larvae of strain A-9 show significant mortality rates when grown at 0.88 ppm AFB1, while these stages are not affected in strain A-11.     

Impact of oilseed rape expressing the insecticidal cysteine protease inhibitor oryzacystatin on the beneficial predator Harmonia axyridis (multicoloured Asian ladybeetle)

Insect-resistant transgenic plants have been suggested to have deleterious effects on beneficial predators through transmission of the transgene product by the pest to the predator. To test this hypothesis, effects of oilseed rape expressing the cysteine protease inhibitor oryzacystatin-1 (OC-1) on the predatory ladybird Harmonia axyridis were investigated using diamondback moth Plutella xylostella as the pest species. As expected, oilseed rape expressing OC-1 had no effects on either development or survival of the pest, which utilizes serine digestive proteases. Immunoassays confirmed accumulation of the transgene product in pest larval tissues at levels of up to 3 ng per gut. Characterization of proteolytic digestive enzymes of H. axyridis demonstrated that larvae and adults utilize cysteine and aspartic proteases; the former activity was completely inhibited by oryzacystatin in vitro. However, when H. axyridis larvae consumed prey reared on OC-1 expressing plants over their entire life cycle, no significant effects upon survival or overall development were observed. The inhibitor initially stimulated development, with a shortening of the developmental period of the second instar by 27% (P < 0.0001) accompanied by a 36% increase in weight of second instar larvae (P = 0.007). OC-1 had no detrimental effects on reproductive fitness of adult H. axyridis. Interestingly there was a significant increase in consumption of OC-1 dosed prey. The results show that prey reared on transgenic plants expressing a protein which inhibited ladybird digestive enzymes in vitro had no effects in vivo; the ladybird was able to up-regulate digestive proteases in response to the inhibitor.     

The two duplicated insecticyanin genes, ins-a and ins-b are differentially expressed in the tobacco hornworm, Manduca sexta.

Two gene-specific probes were generated from the unique sequences in the 3' non-coding regions of the two insecticyanin genes, ins-a and ins-b to study the developmental expression of these genes in Manduca sexta. Both genes were initially transcribed in the freshly hatched first instar larvae and then expressed in the epidermis and to a lesser degree in the fat body during every larval feeding stage. In the epidermis of the 4th and 5th instar larvae, both mRNAs appeared shortly before ecdysis and accumulated to maximal levels within a day. As the larval epidermis became pupally committed on day 3 of the 5th (final) instar, INS-a mRNA quickly decreased, whereas INS-b mRNA showed a second peak of accumulation. In the fat body, both genes showed a similar expression pattern within the 4th instar to that of the epidermis except that levels were lower and ins-b mRNA dominated. In the final instar, only ins-b mRNA was present in significant amount. These findings not only reveal that the two duplicated insecticyanin genes have diverged in their expression pattern but also demonstrate, for the first time, that fat body also expresses insecticyanin genes.     

黑水虻消化道形态及组织结构的观察

本文比较了不同发育阶段黑水虻Hermetia illucens消化道的形态学差异,掌握了幼虫消化系统的组织学特征。利用体视镜观察黑水虻5龄幼虫、预蛹及成虫的消化道形态,利用光学显微镜和扫描电镜观察幼虫消化道各段(前肠、中肠、后肠)的显微及超微结构。结果表明：黑水虻幼虫及预蛹的消化道均由前肠(食道和前胃)、中肠及后肠组成,从幼虫到成虫,消化道的长度不断缩短。与幼虫和预蛹相比,成虫消化道形态变化明显,前胃消失,出现了嗉囊及胃盲囊,中肠进一步缩短,后肠分化为回肠、结肠和直肠。组织学观察结果显示,幼虫的唾液腺开口于口腔,由膨大的管状腺体和腺管组成。食道由特化为角质刺突的内膜层及发达的肌层组成,其末端延伸至前胃。前胃膨大为球状,包括三层组织结构。根据上皮细胞形态的差异,中肠可分为四个区段。后肠薄,肠腔内褶丰富,肠壁可见数量较多的杆状细菌。马氏管开口于中、后肠交界处,包括4支盲管,管内壁密布微绒毛。黑水虻消化道形态随发育阶段的变化,反映了各阶段摄食及消化生理的差异。幼虫消化道各段具有各自典型的组织学特征,其前、中、后肠可能分别承担了食物接纳与初步消化、消化与吸收以及重吸收功能。本研究结果为进一步了...     

Chemical interaction between the larva of a dipteran parasitoid and its coleopteran host: a case of exploitation of the communication system during the searching behaviour?

The robber fly Mallophora ruficauda is one of the principal apicultural pests in the Pampas region of Argentina. As adults, the flies prey on honey bees and other insects; while, as larvae, they parasitize scarab beetle larvae. Females of M. ruficauda lay eggs away from the host in tall grasses. After being dispersed by the wind, larvae drop to the ground, where they dig in search of their hosts. It is known that second instar larvae of M. ruficauda exhibit active host searching behaviour towards its preferred host, third instar larva of Cyclocephala signaticollis, using host-related chemical cues. Furthermore, previous works show that these chemical cues are produced in the posterior body half of hosts. However, the precise anatomical origin of these cues and whether they mediate any behaviour of C. signaticollis larvae remains yet unknown. In order to determine the precise origin of the chemical cue, we carried out olfactometer assays with different stimuli of extracts of the posterior C. signaticollis body half. Additionally, we tested whether C. signaticollis is attracted to any of the same extracts as in the previous experiments. We found that both second instar of M. ruficauda and third instar of C. signaticollis are attracted to extracts of the fermentation chamber (proctodeum). This is the first report of attraction of conspecific larvae in scarab beetles. We discuss a possible case of system communication exploitation in an immature parasitoid-host system.     

Ingestion of Pythium spp. by larvae of the fungus gnat Bradysia impatiens (Diptera:Sciaridae)

Mycelium, oospores and zoospore cysts of Pythium spp. were fed to larvae of the fungus gnat Bradysia impatiens. The fungal structures were all ingested and provided a complete nutritional source for the insect's development from egg to adult. Mycelium seemed the major source of food as only empty fragments were found either in the digestive tract or in larval faeces. Oospores appeared intact and were viable both during passage through the tract and when expelled. Germination of oospores was normal. Most encysted zoospores also survived passage through the gut, although some appeared damaged. After transferring recently-fed larvae to a new food source, oospores were still detected in the digestive tract 48 h later. These results show that the larval stage of B. impatiens may serve as an important vector for Pythium spp.     

Drosophila fibronectin: a protein that shares properties similar to those of its mammalian homologue.

This is the first report on the existence in Drosophila of a protein with properties similar to those of vertebrate fibronectin that we shall refer to as Drosophila fibronectin. Rabbit antibodies against human plasma fibronectin have allowed the detection of this molecule in Drosophila haemolymph; common epitopes are shared by the two proteins. Drosophila fibronectin with a subunit mol. wt of approximately 230 kd is a glycoprotein which binds to denatured mammalian collagen. It is present throughout development and is as abundant in embryos as in larvae and adult flies. Drosophila fibronectin is differentially expressed during embryogenesis, a small amount being present before the blastoderm stage. Its concentration increases at gastrulation and reaches a steady-state value at the end of organogenesis. Drosophila fibronectin is predominantly detected by immunofluorescence on frozen sections of 16 h embryos in the extracellular spaces lying between the different tissues and organs. In mature third instar larvae, most of the staining is concentrated in fat body and imaginal discs, and the pattern strongly supports an extracellular localization of the protein. In addition, it is shown that Drosophila embryonic cells can functionally utilize vertebrate fibronectin for their spreading and differentiation. Finally, injection of antihuman plasma fibronectin antibodies in early embryos leads to the same phenotype as injection of Arg-Gly-Asp-containing peptides. This result suggests that one of the Arg-Gly-Asp-bearing protein(s) involved in gastrulation might be fibronectin.     

Spermiogenesis of the testes of juvenile hormone-treated silkworm larvae,Bombyx mori

• 1.1. To examine changes in the percentages of testicular cells such as 1C cells (spermatids and spermatozoa), 2C cells (G1 somatic cells, spermatogonia and secondary spermatocytes), 2–4C cells (somatic and germinal cells in S phase) and 4C cells (G2 somatic cells and primary spermatocytes), we isolated nuclei from the testes of silkworm larvae and subjected them to flow cytometric analysis.
• 2.2. In control testes, 1C cells appeared at day 0 of the fifth instar, increased gradually by spinning and increased steeply at 2 days later still spinning. The percentage of 2C cells decreased gradually after ecdysis to the fifth instar. The percentage of 4C cells increased from day 2 to day 5 of the fifth instar and decreased after day 11 of this instar. Cells in S phase remained constant through the fifth instar.
• 3.3. An injection of juvenile hormone analog, methoprene, at day 0 of the fifth instar did not inhibit spermiogenesis, but resulted in increased 2C cells and decreased 4C cells dose-dependently. In contrast, the same treatment at day 2 of the fifth instar did not change the percentages of 1C, 2C and 4C cells of the testes at all, suggesting that the testes changed sensitivity to the hormone at larval development.
• 4.4. Repeated injections of methoprene to induce the appearance of dauer larvae resulted in a complete block of the development of 1C cells.

     

Laboratory experiments on factors affecting oviposition site selection in Toxorhynchites amboinensis (Diptera: Culicidae), with a report on the occurrence of egg cannibalism

Laboratory experiments tested the effects of water quality and the presence of conspecific and heterospecific immatures on oviposition by Toxorhynchites amboinensis (Doleschall). The females showed a highly significant preference for oak leaf infusion water over distilled water. When twenty starved third and fourth instar Tx.amboinensis larvae were present in the water, substantially fewer eggs were counted from pots containing these conspecifics, than from controls in which no larvae were present. Numbers of eggs from pots containing starved second instar larvae did not differ significantly from controls. Observations of larval behaviour while oviposition was occurring suggested that egg numbers were reduced in containers because of egg cannibalism with third and fourth instar larvae, and not because the larvae caused a deterrent effect. Subsequent experiments confirming the occurrence of substantial egg cannibalism by third and especially fourth instar larvae are described. As with larvae, the presence of Tx.amboinensis pupae in the water had little effect on oviposition. If placed in the water 24 h prior to test, pupae very slightly enhanced its attractiveness, but if introduced immediately before test there appeared to be a slight deterrent effect. With heterospecific larvae, twenty fourth instar Ae.aegypti larvae introduced into infusion water 24 h before test rendered the water slightly attractive, while water in which Ae.aegypti larvae had been reared for 48 h proved highly repellent.     

Field investigation of pomegranate fruit worms in Taif and laboratory evaluation of Bacillus thuringiensis against Ectomyelois ceratoniae

Field observation during the period of pomegranate production (from May to October) in Taif showed that pomegranate fruits are attacked by two insects, Ectomyelois ceratoniae and Virachola livia. Survey results indicate that the larvae of Ectomyelois ceratoniae was more effective compared with the larvae of Virachola livia. Biological control tests were carried out with commercial Bacillus thuringiensis against the second and fourth instar larvae of Ectomyelois ceratoniae under laboratory conditions. Fourth instar larvae were the most sensitive to bacteria at different concentrations (ppm) compared with the second instar larvae. The survival resulting from higher concentrations was lowest. Larvae fed on dry grapes treated by Bt. appeared to be changed in body color to the white before death.     

Juvenoid action on the total body metabolism in larvae of a noctuid moth

A juvenoid compound known as methoprene has no effect on growth and respiratory metabolism in penultimate instar larvae that contain endogenous juvenile hormone. In the last larval instar the juvenoid induces enormously large somatic growth and postpones pupal ecdysis although it does not increase the overall metabolic intensity beyond certain limits.The metabolic changes caused by the juvenoid were more pronounced when connected with formation of the supernumerary larval instars. After this developmental change the larvae further continued to grow on and turned finally into the conspicuous giants. The overall metabolic capacity of the supernumerary larval tissues surpassed the above limitations determined by the body of a normal last instar larva. However, unlike in some other species, there was no hypermetabolic response to juvenoid treatments in this material.     

Effect of host age on life cycle and morphological characteristics of Glyptapanteles liparidis (Hymenoptera: Braconidae), a parasitoid of Acronicta rumicis (Lepidoptera: Noctuidae)

The life cycle of Glyptapanteles liparidis was 23.75 ± 1.26, 21.95 ± 2.44 and 20.83 ± 0.78 days when fed on the first, second and third instar larvae of Acronicta rumicis, respectively. Although insufficient numbers hindered statistical analysis, the life cycle of G. liparidis appeared to be shortest, 19 days, when fed on fourth instar larvae. The life cycle of G. liparidis tends to shorten as the larvae of A. rumicis fed upon are more advanced. The body length, forewing length and head capsule width of female G. liparidis fed on first instar larvae of A. rumicis were greater than those of males, while the antennae of males were longer than those of females. When fed on second instar larvae, there was no difference in body length and head capsule width between males and females, but the male antennae were longer than the female, and the female forewings were longer than the male. When fed on third instar larvae, there was no significant difference in head capsule width between the sexes, but female body length and forewing length were greater than the male, and the male antennae were longer than the female. On the whole, females were bigger than males in terms of body length and forewing length, while antennae of the males were longer than those of the females. There was no difference in head capsule width between males and females. Body length, antenna length, forewing length and head capsule width of male and female G. liparidis were relatively larger when fed on first instar larvae of A. rumicis than when fed on second and third instar larvae.     

新烟碱类杀虫剂拌种对马铃薯甲虫幼虫食物利用和生长发育的影响

为研究马铃薯甲虫Leptinotarsa decemlineata（Say）幼虫取食新烟碱杀虫剂噻虫嗪和吡虫啉处理（有效成分18 g/100 kg种薯拌种）播种90 d后马铃薯叶片的消化吸收和生长发育情况,在室内采用重量法测定了幼虫取食量、体重增加量、食物利用率,近似消化率以及蛹重等营养指标。 结果表明：70%噻虫嗪种子处理可分散粉剂拌种后,马铃薯甲虫幼虫的取食量、体重增加量、食物利用率、食物转化率、近似消化率和相对生长率以及蛹重显著低于10%吡虫啉可湿性粉剂拌种和空白对照（P＜0.05）,发育历期显著长于10%吡虫啉可湿性粉剂拌种和空白对照（P＜0.05）;而10%吡虫啉可湿性粉剂拌种后,马铃薯甲虫幼虫的取食量和3～4龄期的体重增加量与空白对照差异显著（P＜0.05）,蛹重、1～2龄幼虫的体重增长量、食物利用率、食物转化率、近似消化率、相对生长率和生长发育历期与空白对照差异不显著（P＞0.05）。 说明70%噻虫嗪种子处理可分散粉剂拌种对马铃薯甲虫幼虫的取食有显著抑制作用,不能很好地满足其生长发育营养物质的需要,幼虫取食其叶片后,近似消化率和相对生长速率显著降低,生长发育历期显著延长。 这有利于减少当季世代数,降低危害。     

外源补充多巴胺对异色瓢虫突变体gr生长发育及鞘翅颜色的影响

异色瓢虫Harmonia axyridis是我国常见的一种捕食性天敌昆虫,其基于黑色素的体色在环境适应中发挥着重要作用.多巴胺(dopamine,DA)是昆虫合成黑色素的一类重要前体物质,同时在调节生理活动方面具有重要作用,但尚不清楚多巴胺在异色瓢虫生长发育中的作用.本实验室前期发现一异色瓢虫浅色突变体gr,其体色的黑化程度明显浅于野生型.本研究以该突变体为研究对象,以添加不同浓度DA的人工饲料(10 mg/g(D-H)、1 mg/g(D-M)、与0.1 mg/g(D-L))饲养幼虫,测定生长发育相关参数及新羽化成虫的鞘翅颜色参数.结果显示:桃蚜Myzus persicae饲喂至2龄的gr取食对照饲料后无法成功发育至3龄,而取食添加DA的饲料后可发育至4龄,但不同饲料间的存活率无显著差异,同时D-L处理的3龄幼虫发育时间显著短于D-H与D-M.桃蚜饲喂至4龄后取食人工饲料,D-M处理的化蛹率、羽化率、雌雄虫体重及鞘翅黑色斑点的Brightness值均高于其它两种饲料及对照处理,并且D-L处理新羽化成虫鞘翅黑色斑点的Brightness值最小(颜色最黑).上述结果表明DA在异色瓢虫幼虫生长发育中具有重要作用,但受浓度影响;幼虫期补充DA可影响成虫鞘翅颜色.     

Developmental changes in dopamine levels in larvae of the fly Chymomyza costata: comparison between wild-type and mutant-nondiapause strains

Dopamine and two related catecholamines, L-3,4-dihydroxyphenylalanine (DOPA) and N-acetyl dopamine (NADA), were analyzed in whole body and tissue samples taken throughout late larval development of the drosophilid fly Chymomyza costata, which enters facultative diapause as a mature 3rd instar larva in response to short photophase. Wild-type (W) and mutant-nondiapause (M) strains reared under diapause inducing (d) and preventing (nd) photophases were compared. Developmental changes in the whole body of dopamine levels showed some general features irrespective of fly strain and rearing conditions: sharp major peaks during moult from second to third instar larva and during pupariation; lower minor peaks around the middle of both 2nd and 3rd instars. Significant differences between the strains and conditions were also found: dopamine levels were lower throughout the 2nd instar and during the 2nd to 3rd instar moult of mutant strain larvae (M/d) as compared to wild-type larvae (W/nd and W/d); while the late 2nd and late 3rd instar larvae destined to diapause (W/d) maintained relatively high dopamine concentrations, their counterparts destined to continuous development (W/nd and M/d) significantly decreased dopamine levels prior to the 2nd to 3rd instar moult or pupariation. Possible relationship between the dopamine levels and diapause induction/onset in C. costata larvae is discussed. Integument contained more than 90% of the dopamine found in the whole body. The gut and central nervous tissues showed relatively low pools of dopamine, only trace amounts were detected in haemolymph and no dopamine was found in fat body. DOPA levels were low and stable throughout larval development of both W and M strains and under both conditions. NADA levels peaked during second halves of 2nd and 3rd instars of both strains, then dropped to trace levels and were elevated again during 2nd to 3rd instar moult as well as in tanned prepupae. No elevation of NADA levels was recorded in 3rd instar W/d larvae which entered diapause.     

short gastrulation, a mutation causing delays in stage-specific cell shape changes during gastrulation in Drosophila melanogaster

Mutations at the short gastrulation locus affect the timing of certain early morphogenetic events occurring during gastrulation in Drosophila melanogaster. Specifically, the invagination and subsequent closing of the posterior midgut and the anterior midgut appear to be delayed in these embryos. In addition, their germbands do not extent the full distance anteriorly on the dorsal side of the embryo. The dorsal cells are abnormally thick and fall into extremely deep dorsal folds as the germband extends. sog embryos continue development, but form disorganized first instar larvae. Normal sog expression is required in the zygote, but not in the mother for normal embryonic development and viability. Analysis of adult and larval gynandromorphs indicates that sog expression is required only in the ventral and/or anterior and posterior ends of the embryo, arguing that the dorsal abnormalities caused by the mutation are secondary consequences of defects elsewhere in mutant embryos.     

转Bt基因抗虫棉对棉铃虫拒食作用及其机理研究

转Bt基因抗虫棉对 3 ,4,5龄棉铃虫幼虫的抗性表现形式为拒食作用 ,且随幼虫龄期的增加拒食作用明显降低 ,其中对 5龄幼虫的拒食作用很低。取食Bt棉后 ,3 ,4,5龄棉铃虫幼虫中肠消化酶比活力均较对照有所减退 ,且随幼虫龄期的增加减退率明显降低 ,其中对 5龄幼虫减退率最低。由此 ,解释了Bt棉对 3龄及 3龄以上棉铃虫幼虫抗性表现形式、抗性随不同幼虫龄期的差异性 ,及其抗性差异性的消化机理。