Black light trap collections in Wangging county and Yanji city,Jilin Province,China, August 2006–2007

Adult mosquito surveillance was conducted using black light traps in August of 2006 and 2007 at Wangging county and Yanji city, Jilin Province, China to identify the distribution of anopheline mosquitoes in northern China. A total of 2459 female mosquitoes comprising three genera and eight species including Anopheles (Anopheles) lesteri, An. (Ano.) kleini, An. (Ano.) pullus, Culex inatomii, Cx. orientalis, Cx. pipiens, Cx. bitaeniorhynchus and Aedes vexans nipponii were collected. The most commonly collected species was An. kleini which had not been previously reported from China. Anopheles sinensis sensu stricto is commonly collected throughout China, but was not collected from these areas.     

Immunostaining for allatotropin and allatostatin-A and -C in the mosquitoes <Emphasis Type="Italic">Aedes aegypti</Emphasis> and <Emphasis Type="Italic">Anopheles albimanus</Emphasis>

Confocal laser-scanning microscopy was used to carry out a comparative study of the immunostaining for three families of neuropeptides, viz., allatostatin-A (AS-A), allatostatin-C (AS-C) and allatotropin (AT), in adult female mosquitoes of Aedes aegypti and Anopheles albimanus. The specific patterns of immunostaining for each of the three peptides were similar in both species. The antisera raised against AT, AS-A, and AS-C revealed intense immunoreactivity in the cells of each protocerebral lobe of the brain and stained cells in each of the ventral ganglia and neuronal projections innervating various thoracic and abdominal tissues. Only the AS-A antiserum labeled immunoreactive endocrine cells in the midgut. The distribution of the peptides supports the concept that they play multiple regulatory roles in both species.This work was supported by NIH grant AI 45545 to F.G.N. and CONACyT G-37186-M to M.H.R.     

Malaria transmission risk by the mosquito Anopheles baimaii (formerly known as An. dirus species D) at different hours of the night in North-east India

The risk of acquiring malaria transmitted by Anopheles baimaii Sallum & Peyton, 2005, formerly known as An. dirus species D (Sallum et al., 2005) (Diptera: Culicidae), at different hours of the night in a forest-fringed village of Assam, North-east India was assessed through all-night mosquito landing catches during 1995-2000. An estimated overall mean biting rate of 36.1 bites/person/night (95% CI = 26.2-45.8), a sporozoite rate of 1.9% (95% CI = 1.1-2.9%) and a parous rate of 58.7% (95% CI = 55.3-62.0%) were recorded. Parous and sporozoite-positive females tended to be caught mainly before midnight. The effective entomological inoculation rate was the highest (0.249 positive bites/person/night) from 21.00 to 24.00 hours, suggesting that the second quartile of the night is the most risky period for malaria transmission by An. baimaii. Considering that approximately 21% of mean inoculations take place before 21.00 hours, it appears that there is a need for appropriate protective measures during the pre-bed time period to supplement the impact of insecticide-treated nets against An. baimaii in north-east India.     

Structural and evolutionary analyses of the Ty3/gypsy group of LTR retrotransposons in the genome of Anopheles gambiae

The recent availability of the genome of Anopheles gambiae offers an extraordinary opportunity for comparative studies of the diversity of transposable elements (TEs) and their evolutionary dynamics between two related species, taking advantage of the existing information from Drosophila melanogaster. To this goal, we screened the genome of A. gambiae for elements belonging to the Ty3/gypsy group of long-terminal repeat (LTR) retrotransposons. The A. gambiae genome displays a rich diversity of LTR retrotransposons, clearly greater than D. melanogaster. We have characterized in detail 63 families, belonging to five of the nine main lineages of the Ty3/gypsy group. The Mag lineage is the most diverse and abundant, with more than 30 families. In sharp contrast with this finding, a single family belonging to this lineage has been found in D. melanogaster, here reported for the first time in the literature, most probably consisting of old inactive elements. The CsRn1 lineage is also abundant in A. gambiae but almost absent from D. melanogaster. Conversely, the Osvaldo lineage has been detected in Drosophila but not in Anopheles. Comparison of structural characteristics of different families led to the identification of several lineage-specific features such as the primer-binding site (PBS), the gag-pol translational recoding signal (TRS), which is extraordinarily diverse within the Ty3/gypsy retrotransposons of A. gambiae, or the presence/absence of specific amino acid motifs. Interestingly, some of these characteristics, although in general well conserved within lineages, may have evolved independently in particular branches of the phylogenetic tree. We also show evidence of recent activity for around 75% of the families. Nevertheless, almost all families contain a high proportion of degenerate members and solitary LTRs (solo LTRs), indicative of a lower turnover rate of retrotransposons belonging to the Ty3/gypsy group in A. gambiae than in D. melanogaster. Finally, we have detected significant overrepresentations of insertions on the X chromosome versus autosomes and of putatively active insertions on euchromatin versus heterochromatin.     

Close association of invading Plasmodium berghei and beta integrin in the Anopheles gambiae midgut

We have used confocal microscopy and an antibody against Anopheles gambiae beta integrin to study this protein's distribution in the mosquito midgut and its relationship to invading Plasmodium berghei parasites. An extensive reorganization of integrin is seen to take place in the midgut epithelial cells following the uptake of either non-infected or parasite-infected blood meal, probably reflecting the reshaping of the gut due to the presence of the food bolus and the peritrophic membrane that surrounds it. Furthermore, malaria parasites are coated with beta integrin immediately upon entry into the epithelium, independent of whether they develop intra- or extracellularly. Although this coat is shed a few days after the invasion, beta integrin remains concentrated in the cells surrounding the maturing oocyst for several days. Finally, the antibody detects a structural change in the midgut epithelial cells in the immediate vicinity of the invading ookinete, which is consistent with Plasmodium-induced apoptosis followed by wound healing. This intimate association suggests a specific role of beta integrin in the invasion process.     

The Physical Gene Hsp70 Map on Polytene Chromosomes of Anopheles darlingi from the Brazilian Amazon

In situ hybridization was used to determine the physical location of the Hsp70 genes in salivary polytene chromosomes of Anopheles darlingi from Manaus and Macapá, Brazil, and to assess the usefulness of the Hsp70 locus as a genetic marker in A. darlingi populations. In both populations, the double markings corresponding to the Hsp70-12A and Hsp70-14A genes were located on the right arm of chromosome 2. The Hsp70 locus was considered to be an excellent marker for studying chromosomal evolution and relationships among A. darlingi populations.     

疟疾媒介斯氏按蚊印度品系经溴氰菊酯或溴氰菊酯增效剂选择后的繁殖劣势

了解敏感和抗性蚊虫的繁殖适合度对于规划和实施蚊虫防治计划具有重要意义。本研究分别将斯氏按蚊Anopheles stephensi幼虫用溴氰菊酯(AnD_L)及溴氰菊酯和PBO混配制剂(1∶5) (AnD_P), 或斯氏按蚊成虫用溴氰菊酯(AnD_A) 进行选择后, 在实验室内检测了起源于印度德里的斯氏按蚊亲本（AnS）和抗性品系 (AnR) 的繁殖适合度的变化,从繁殖力、生育力、卵孵化率和生殖营养周期的长度等方面评价了斯氏按蚊的繁殖适合度。结果表明：与AnS品系相比, AnR品系的生殖营养周期缩短了60%~73%。与AnS品系相比, AnR品系的产卵量显著降低, 降幅达14.5%~37.9%,对溴氰菊酯抗性最强的AnD_L40品系的产卵量降低得最多。这些结果说明溴氰菊酯抗性与繁殖劣势之间可能存在正相关。与亲本品系相比, AnD_L40品系的卵孵化率降低了19.4%~30.9%, 进一步证实了这一相关性。在RD_P品系中观察到繁殖适合度降低, 表明溴氰菊酯增效剂的选择不仅在降低溴氰菊酯抗性水平而且在降低抗性个体频率上的效率。在对溴氰菊酯几乎不具有抗性的成虫品系的选择中繁殖适合度降低, 暗示溴氰菊酯作为灭杀斯氏按蚊成虫剂的效果要好于作为杀幼虫剂的效果。这些结果提示, 通过对斯氏按蚊实施不同抗性治理策略, 种群中抗性基因型的繁殖适合度的降低可消除杂合子和抗性纯合子。     

The association between the phytoplankton, Rhopalosolen species (Chlorophyta; Chlorophyceae), and Anopheles gambiae sensu lato (Diptera: Culicidae) larval abundance in western Kenya

Algae are important food resources of the larvae of the African malaria vectors, Anopheles gambiae Giles and Anopheles arabiensis Patton (Anopheles gambiae sensu lato), and other zooplankton, but empirical evidence remains meager about the agal flora in ephemeral water bodies. The animals present in natural aquatic habitats in western Kenya were sampled from July to November 2002 to study abiotic and biotic environmental factors determining A. gambiae sl larval abundance. The five highest concentrations of third and fourth instars and pupae (hereafter referred to as old-stage larvae) were sampled in conjunction with the unicellular epizoic green algae, Rhopalosolen species (Chlorophyta; Chlorophyceae). Canonical correspondence analysis revealed that the presence of Rhopalosolen species was the most important determinant of the animal assemblage. The density of old-stage A. gambiae sl larvae was positively correlated with the presence of Rhopalosolen species, but the density of first and second instars of A. gambiae sl was not. The water bodies with Rhopalosolen sp. yielded larger mosquitoes in spite of the higher density of larvae. We demonstrated that the productivity of water bodies in terms of the larvae of malaria vectors can differ in magnitude depending on the agal flora. We discuss phytoplankton as a regulator of mosquito larval populations.     

Activation process of the mosquitocidal delta-endotoxin Cry39A produced by Bacillus thuringiensis subsp. aizawai BUN1-14 and binding property to Anopheles stephensi BBMV

Most delta-endotoxins produced by Bacillus thuringiensis require proteolytic processing in order to become active. The in vitro and in vivo activation processes of Cry39A, a delta-endotoxin that is highly toxic to Anopheles stephensi, were investigated. Cry39A with a molecular mass of 72 kDa was processed in vitro into a 60 kDa fragment by trypsin and gut extract from A. stephensi larvae. N-terminal amino acid sequencing of the 60 kDa fragment revealed that trypsin and the protease(s) in the gut extract cleaved Cry39A between Arg(61) and Gly(62). In contrast, 40 and 25 kDa polypeptides were generated in vivo by intramolecular cleavage of the 60 kDa fragment in A. stephensi larvae. Further, a co-precipitation assay was used to investigate the binding property of the activated Cry39A to A. stephensi BBMV. Cry39A bound to A. stephensi BBMV specifically and did not compete with the Cry4Aa toxin. This indicated that the binding molecule(s) for Cry39A might differ from those for Cry4A. In addition, Cry39A preferentially bound to the Triton X-100-insoluble membrane fraction.