Evolution of larval segment position across 12 Drosophila species*

Many developmental traits that are critical to the survival of the organism are also robust. These robust traits are resistant to phenotypic change in the face of variation. This presents a challenge to evolution. In this article, we asked whether and how a well-established robust trait, Drosophila segment patterning, changed over the evolutionary history of the genus. We compared segment position scaled to body length at the first-instar larval stage among 12 Drosophila species. We found that relative segment position has changed many times across the phylogeny. Changes were frequent, but primarily small in magnitude. Phylogenetic analysis demonstrated that rates of change in segment position are variable along the Drosophila phylogenetic tree, and that these changes can occur in short evolutionary timescales. Correlation between position shifts of segments decreased as the distance between two segments increased, suggesting local control of segment position. The posterior-most abdominal segment showed the highest magnitude of change on average, had the highest rate of evolution between species, and appeared to be evolving more independently as compared to the rest of the segments. This segment was exceptionally elongated in the cactophilic species in our dataset, raising questions as to whether this change may be adaptive.     

Biostratigraphy and stage boundaries of the upper Cretaceous–early Paleogene successions in southern Galala area,North-Eastern Desert,Egypt

The foraminiferal contents of three surface sections [Gebel Tarboul, Wadi Tarfa (WT) and Bir Dakhl (BD) sections] in southern Galala area, North-Eastern Desert, Egypt, have been studied in detail and used in biostratigraphy and chronostratigraphy of the upper Cretaceous–Paleogene successions. Sixty-nine planktonic foraminiferal species belonging to 23 genera have yielded 17 biozones. They are given in ascending order: Globotruncana aegyptiaca Interval Zone (IZ), Gansserina gansseri IZ, Contusotruncana contusa–Racemiguembelina fructicosa IZ, Abathomphalus mayaroensis IZ, P1c, P2, P3, P3a, P3b, P4, P4a, P4b, P4c, P5, E1, E2, E3, E4 and E5. Moreover, local and widespread regional hiatus was detected in the pelagic to hemipelagic sequence during Cretaceous–Paleogene boundary in southern Galala Sub-basin. This hiatus corresponds to the Early Maastrichtian–Early Eocene in Gebel Tarboul, the interval between Late Maastrichtian–Early Paleocene throughout WT sequences and Late Maastrichtian–Late Paleocene in BD section.     

METAMORPHOSIS OF THE LARVA OF THE POLYCHAETE ARENICOLA CRISTATA. MORPHOLOGY OF THE ‘HOUR-GLASS’ STAGE

The constricted ‘waist’ of the metamorphosing larva of the polychaete Arenicola cristata is described, using light and electron microscopy. The constriction is shown to be the consequence of the discharge and collapse of a post-trochal ring of epithelial cells which remain as functional components of the post-metamorphic juvenile. Morphological differentiation of neuro-effector and interneuronal contacts is initiated at this time. Muscular and neural changes are discussed in terms of their role in effecting metamorphosis.     

Brugia pahangi: Immunization with early L3 ES alters parasite migration,and reduces microfilaremia and lymphatic lesion formation in gerbils (Meriones unguiculatus)

Previous studies have shown that intradermally (ID) injected Brugia pahangi L3s migrate through various tissues and into the lymphatics of gerbils in a distinct pattern. Excretory/secretory products (ES) produced at the time of invasion of B. pahangi are likely to be important in this early migration phase of the parasite life cycle in their rodent host. Hence, early L3 ES was collected from 24 h in vitro cultures of B. pahangi L3 larvae and used in immunization experiments to investigate the effect of immunity to early L3 ES on worm migration, survival and development of B. pahangi. Immunization of gerbils with ES in RIBI adjuvant produced antibodies to numerous ES proteins eliciting a strong humoral response to ES and indirect fluorescent antibody (IFA) assay using anti-ES serum recognized the ES proteins on the surface of B. pahangi L3 larvae. Following ES immunization, gerbils were challenged either ID or intraperitoneally (IP) with 100 L3s of B. pahangi and euthanized at 3 or 106 days post inoculation (DPI). Immunization with early ES slowed the migration of ID inoculated L3 at 3 DPI and significantly altered the locations of adult worms at 106 DPI. Immunization did not induce protection in any treatment group. However, immunized animals had significantly fewer microfilariae per female worm suggesting the antigens in ES are important in microfilariae development or survival in the host. The number of lymphatic granulomas was also significantly reduced in ES immunized animals. It is important to note that microfilariae serve as a nidus in these granulomas. Our results shows immunization with early Brugia malayi L3 ES alters the worm migration, affects circulating microfilarial numbers and reduces lymphatic granulomas associated with B. pahangi infection in gerbils.     

采收期对青皮核桃果实生理特性与耐贮性的影响

以‘中林5号’(早熟)、‘辽宁4号’(中熟)、‘西扶1号’(中晚熟)青皮核桃果实为试材,于8月上、中、下旬3个采收期采果,在0~1℃冷藏过程中测定贮期生理指标和保鲜效应。结果显示:(1)各采收期和各品种果实呼吸强度(RI)均呈双峰型变化;8月中旬采收的果实呼吸峰出现较早,其纤维素酶(Cx)活性较另2个采收期多1个高峰;多聚半乳糖醛酸酶(PG)活性增强最早,其贮后核仁酸价上升幅度最大,果实腐烂最快。(2)8月下旬同期采收的3个品种果实的贮期各生理指标变化趋于一致;贮藏54d时,果实腐烂率依次为‘辽宁4号’>‘中林5号’>‘西扶1号’。(3)‘辽宁4号’核仁可溶性蛋白质含量越高,贮后下降率最大。研究表明,青皮核桃果实采后生理代谢活性与耐贮性主要与采收时期有关,受品种影响较小,且8月中旬采收的果实采后生理代谢旺盛,耐贮藏性均最差;‘辽宁4号’果实在各采收期的耐贮性均小于其他品种果实。     

小叶锦鸡儿灌丛下土壤水分对降雨的响应

以科尔沁沙地主要固沙灌木小叶锦鸡儿为研究对象,在其生长季次降雨21.5 mm后180 h内,利用TDR和微渗仪测量小叶锦鸡儿灌丛下不同部位的土壤含水量和土壤蒸发,并计算该灌丛下不同部位储水量和水量平衡.结果表明:降雨结束后初期,灌丛枝干的茎流作用使其根部的土壤含水量明显高于其他部位;灌丛根部水分的入渗速率大于灌丛中部和灌丛外缘.因冠幅的庇荫作用,灌丛下蒸发量小于灌丛外裸露沙地.水量平衡表明:小叶锦鸡儿灌丛下降雨后前期蒸散量明显高于灌丛外裸露沙地,与灌丛下根系的分布有直接关系.     

Evaluation of an indigenous parasitoid Habrobracon gelechiae (Hymenoptera: Braconidae) for biological control of light brown apple moth Epiphyas postvittana (Lepidoptera: Tortricidae) in California

Light brown apple moth, Epiphyas postvittana (Walker), is a newly invasive pest in California. Habrobracon gelechiae Ashmead is an indigenous North American ectoparasitoid of lepidopterans. Using E. postvittana as the host, we determined H. gelechiae host stage preference for oviposition and suitability for larval growth: the parasitoid attacked second to fifth instars, but preferred older (third to fifth) host larvae for oviposition, laying more eggs per clutch on the largest (fifth instar). Offspring survival was better on larger (third to fifth instars) hosts. Adult survival and fecundity and immature temperature development were studied at three key temperatures. At 12°C, H. gelechiae failed to oviposit. At 22 and 30°C, H. gelechiae had, respectively, egg to adult developmental times of 15.4 and 8.7 days, adult female survival of 54.8 and 27.2 days, lifetime parasitism of 39.9 and 21.8 hosts and 181 and 151 eggs per female, an intrinsic rate of increase of 0.107 and 0.165, and mean generation time 30.7 and 18.9 days. We studied intraguild interactions with the endoparasitoid Meteorus ictericus Nees, and found that H. gelechiae did not discriminate against hosts that were parasitised by M. ictericus. Neither the paralysing venom injected by H. gelechiae or the presence of the ectoparasitoid's eggs or larvae arrested M. ictericus development. We also conducted a field release of H. gelechiae on two plant species commonly infested by E. postvittana and showed that H. gelechiae was able to locate and attack moth larvae on both hosts.     

Malaria parasite liver stages render host hepatocytes susceptible to mitochondria-initiated apoptosis

Intracellular eukaryotic parasites and their host cells constitute complex, coevolved cellular interaction systems that frequently cause disease. Among them, Plasmodium parasites cause a significant health burden in humans, killing up to one million people annually. To succeed in the mammalian host after transmission by mosquitoes, Plasmodium parasites must complete intracellular replication within hepatocytes and then release new infectious forms into the blood. Using Plasmodium yoelii rodent malaria parasites, we show that some liver stage (LS)-infected hepatocytes undergo apoptosis without external triggers, but the majority of infected cells do not, and can also resist Fas-mediated apoptosis. In contrast, apoptosis is dramatically increased in hepatocytes infected with attenuated parasites. Furthermore, we find that blocking total or mitochondria-initiated host cell apoptosis increases LS parasite burden in mice, suggesting that an anti-apoptotic host environment fosters parasite survival. Strikingly, although LS infection confers strong resistance to extrinsic host hepatocyte apoptosis, infected hepatocytes lose their ability to resist apoptosis when anti-apoptotic mitochondrial proteins are inhibited. This is demonstrated by our finding that B-cell lymphoma 2 family inhibitors preferentially induce apoptosis in LS-infected hepatocytes and significantly reduce LS parasite burden in mice. Thus, targeting critical points of susceptibility in the LS-infected host cell might provide new avenues for malaria prophylaxis.     

Ontogenic variation in response of Brassica campestris L. to cadmium toxicity

Abstract

Rapeseed (Brassica campestris L.) cv Pusa Gold plants, exposed to different cadmium (Cd) levels (0, 25, 50 and 100 mg kg^?1 soil) in greenhouse, pot culture experiment, were analyzed with reference to distribution of metal, accumulation of biomass and the degree of growth stage Cd-sensitivity. A significant maximum decrease in plant biomass was observed at Cd-exposed flowering stage followed by pre-flowering and post-flowering stages. Activities of enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) differentially increased; while, the concentrations of non-enzymatic antioxidants such as ascorbic acid (AsA) and glutathione (GSH) drastically decreased in plants exposed to Cd at various growth stages. However, the concentrations of GSH and AsA decreased maximally in plant groups exposed to Cd at their flowering stage. The maximum Cd-accumulation occurred in roots followed by leaves and stem. Various Cd levels inhibited also the contents of plant nutrients such as nitrogen (N), phosphorous (P), potassium (K) and sulfur (S) in leaves. The present endeavor hence concludes the existence of close relationships among growth parameters, Cd-sensitivity of phenological stages of the crop and the components of antioxidant system in rapeseed plants exposed at various growth stages.     

Gene expression and activity of antioxidant enzymes in barley (Hordeum vulgare L.) under controlled severe drought

The objective of the present study was to determine the activity of antioxidant enzymes: superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) and the expression of their genes in two barley genotypes under controlled severe drought. To fulfill this objective, 21-day-old barley plants of two genotypes: Rum and Yarmouk were exposed to controlled severe drought (25% field capacity) for 2, 9, and 16 days. The activity of SOD was significantly high in Rum genotype after 2 days of drought treatment. In Yarmouk genotype, the activity of APX was significantly high after 2 and 9 days of drought treatment. In Rum genotype, CAT2 was upregulated after 9 days of drought treatment and SOD and APX were upregulated after 16 days of drought treatment, whereas CAT2, SOD, and APX were upregulated in Yarmouk genotype after 2 days of drought treatment. The results indicate a unique pattern of activity and gene expression of the antioxidant enzymes in the two barley genotypes under controlled severe drought. Moreover, the data suggest that each genotype utilizes different molecular and biochemical responses under the same drought conditions.