Cytogenetic evidence for a complex of species within the taxon Anopheles maculatus (Diptera: Culicidae)

Two largely independent studies of chromosomes from natural populations of Anopheles maculatus provide evidence for several genetic species within the taxon. (1) Polytene chromosome variation shows four different rearrangements of arm 2 and three rearrangements of the X chromosome. There is strong evidence for three species. Two allopatric populations represent either dramatic geographic variation for two independent inversion systems within one of the genetic species, or represent two additional species. Their species status remains unresolved by this work. (2) Heterochromatic variation occurs in both X and Y chromosomes as revealed by Giemsa-banding of mitotic chromosomes from larval brains. The distribution and association of these various sex chromosomes give further evidence of a species complex. A preliminary correlation of these two kinds of chromosomal variation is given.     

按蚊属一新种(双翅目:蚊科)

记述采自云南思茅市水塘内按蚊1新种,讨论了新种与近缘种的鉴别特征。模式标本保存于云南省寄生虫病防治所。     

Role of species composition in malaria transmission by the Anopheles funestus group (Diptera: Culicidae) in Ghana

Malaria remains a public health problem in Ghana, with Anopheles gambiae and Anopheles funestus as the predominant vectors. While much information exists on the species composition of An. gambiae, very little exists for An. funestus. This study was carried out to determine the species composition of An. funestus Giles populations from three ecological areas in Ghana and investigate their role in malaria transmission. Mosquitoes were collected using human landing and pyrethrum spray methods. A total of 10,254 Anopheles individuals were collected, out of which An. funestus constituted 53.6% (5,496). An. funestus sensu stricto (s.s.) and Anopheles lessoni were identified as the only members of the An. funestus group in all three ecological areas. All 62 sporozoite positive specimens that were identified as An. funestus s.s. were highly anthropophilic with a human blood index in the range of 80–96%, whereas more than 83% of the An. leesoni had fed on either bovine, goat, or sheep. Malaria transmission was higher in the Sahel savannah area than the rest of the ecological zones, with An. funestus s.s. being implicated as a vector of malaria in all ecological zones. Anopheles leesoni occurred in all the ecological areas but played no role in malaria transmission. The study established the importance of An. funestus s.s. in malaria transmission in Ghana.     

Isolation and characterization of microsatellite loci in the mosquito Anopheles stephensi Liston (Diptera: Culicidae)

The mosquito Anopheles stephensi is an important malaria vector in India, Pakistan, Iran and Afghanistan. Differences in egg morphology and chromosomal characters have been described between urban and rural forms of this mosquito but the population genetic structure remains unclear. In India this species is mainly urban, rural populations are largely zoophilic and not thought to transmit malaria. In eastern Afghanistan and the Punjab and Northwest Frontier Province, Pakistan, it is the major malaria vector. We have developed primers for 16 microsatellite loci to assist in defining the population structure and epidemiological importance of this mosquito.     

Vector competence of Anopheles lesteri Baisas and Hu (Diptera: Culicidae) to Plasmodium vivax in Korea

Three anopheline mosquitoes in Korea were studied for their abilities as vectors for Plasmodium vivax. The female mosquitoes of Anopheles lesteri, An. pullus and An. sinensis were allowed to suck malaria patient blood until fully fed, and they were then bred for 2 weeks to develop from malaria parasites to sporozoites. The result from the above confirmed the sporozoites in one An. lesteri of one individual and five An. sinensis of six individuals. We also confirmed that An. sinensis was the main vector to transmit malaria and An. lesteri as well as An. sinensis were able to carry Korean malaria parasites. Therefore, we propose that diversified study is needed to manage malaria projects.     

Biting activity and host preference of the malaria vectors Anopheles maculatus and Anopheles sawadwongporni (Diptera: Culicidae) in Thailand

Adult mosquitoes in the Anopheles maculatus group were surveyed from different regions of Thailand and five different species were morphologically identified, including Anopheles maculatus, Anopheles sawadwongporni, Anopheles notanandai, Anopheles dravidicus, and Anopheles willmori. Blood‐feeding activity and host preference of two species, Anopheles maculatus and Anopheles sawadwongporni, were observed during a one‐year period at Pu Teuy Village, Sai Yok District, Kanchanaburi Province, west‐central Thailand. Both species were more prevalent during the wetter period of the year and each had a greater predilection to feed on cattle than humans. Primary feeding activity occurred between 20:00‐23:00 and a smaller peak at 01:00‐03:00. Findings are discussed relative to the importance of these two vectors for malaria transmission in Pu Teuy.     

Isolation and characterization of polymorphic microsatellite markers from Asian malaria mosquito Anopheles sinensis (Diptera: Culicidae)

Microsatellite-containing region were isolated and characterized in Anopheles sinensis, a primary vector of malaria parasites in Asia. An enrichment protocol yielded 252 microsatellite sequences. We designed primers to amplify 20 unique microsatellites, 14 of which amplify cleanly and were polymorphic. A survey of 24 individuals showed that 12 loci are highly variable with the number of alleles ranging from two to 11, and expected heterozygosity ranging from 0.116 to 0.903. These markers will be useful for population genetic studies and genome mapping in A. sinensis.     

尼日利亚南部阿贝奥库塔地区冈比亚按蚊复合体的形态特征研究（双翅目：蚊科）

对采自尼日利亚南部城市阿贝奥库塔冈比亚按蚊复合体Anopheles gambiae complex的形态特征进行了研究。依据2005年8月至2006年7月灯诱捕获的364个冈比亚按蚊复合体标本,分别对它们的触角、翅、喙、前足、中足和后足6个部位的长度进行了测量,对月平均值进行回归分析,同时利用差异系数（co-efficient of difference,CD）进行近缘分析。分析显示,各特征的长度平均值雨季大于旱季,但是回归分析表明长度变化与季节不显著相关（P>0.05）。差异系数分析结果表明,仅触角长度和翅长显示此复合体为两个不同的种群(CD>1.28),而其他特征值表明为同一种群。因此,该研究结果提示触角长度及翅长对冈比亚按蚊复合体近缘种的区分有重要参考价值。     

DNA Barcodes indicate members of the Anopheles fluviatilis (Diptera: Culicidae) species complex to be conspecific in India

Anopheles fluviatilis, a major vector of malaria in India has been described as a complex of three sibling species members, named as S, T and U, based on variations in chromosomal inversions. Also, ribosomal DNA markers (repetitive Internal Transcribed Spacer 2 (ITS2) and 28S D3 region) were described to differentiate these three sibling species members. However, controversies prevail on the genetic isolation status of these cryptic species. Hence, we evaluated this taxonomic incongruence employing DNA barcoding, the well established methodology for species identification, using 60 An. fluviatilis sensu lato specimens, collected from two malaria endemic eastern states of India. These specimens were also subjected to sibling species characterization by ITS2 and D3 DNA markers. The former marker identified 31 specimens among these as An. fluviatilis S and 21 as An. fluviatilis T. Eight specimens amplified DNA fragments specific for both S and T. The D3 marker characterized 39 specimens belonging to species S and 21 to species T. Neither marker identified species U. Neighbor Joining analysis of mitochondrial cytochrome c oxidase gene 1 sequences (the DNA barcode) categorized all the 60 specimens into a single operational taxonomic unit, their Kimura 2 parameter (K2P) genetic variability being only 0.8%. The genetic differentiation (F_ST) and gene flow (N_m) estimates were 0.00799 and 62.07, respectively, indicating these two ‘species’ (S & T) as genetically con‐specific intermixing populations with negligible genetic differentiation. Earlier investigations have refuted the existence of species U. Also, this study demonstrated that An. fluviatilis and the closely related An. minimus could be taxonomically differentiated by the DNA Barcode approach (K2P = 5.0%).     

Energy-state dependent responses of Anopheles gambiae (Diptera: Culicidae) to simulated bednet-protected hosts

In nature, Anopheles gambiae mosquitoes are found at various energy levels and such females must choose between seeking somatic energy from sugar sources and obtaining both somatic and gametic energy from blood hosts. We used a straight-tube olfactometer containing a simulated unobtainable blood host (human foot smell protected by a net) as well as a sugar source (honey odor). We assessed female probing rate and residence time at the net as a function of energy state (0, 24, 48, 72-h starved). In our trials, 0-h starved females showed low response to human odor, low probing rate, and residence time at the human odor site. By contrast, both 48 and 72-h individuals showed high response to foot odor, longer residence time, and higher probing rates. Seventy-two-h females also flew towards the honey source less often than other groups. Our findings suggest that managing sugar sources might be a viable strategy for influencing mosquito biting behavior.     

Susceptibility of Field Populations of Anopheles sinensis (Diptera: Culicidae) to Bacillus thuringiensis subsp. israelensis

The susceptibility of Anopheles sinensis to Bacillus thuringiensis subsp. israelensis (Bti) was evaluated through exposure to varying concentrations of Bti. Mosquitoes were collected from five field populations of southern and central China (Zhongshan, Hengxian, Wuchang, Xinzhou, and Ruichang) and compared with a standard laboratory strain. The LC₅₀ values were 146.4, 50.4, 57.9, 50.0, 41.6 and 24.6 ng/mL, respectively. Differences in susceptibility to Bti ranging from 1.7 to 5.9-fold compared with the laboratory strain. The Zhongshan strain had the greatest resistance. At low doses, Bti displayed residual effects. Peak mortality occurred from the first to the fourth day. Exposure to low doses increased the duration of larval development and decreased the duration of pupal development, indicating that low doses of Bti have a sublethal effect on their hosts.     

Flight tone of field‐collected populations of Anopheles gambiae and An. arabiensis (Diptera: Culicidae)

Abstract.Laboratory colonies of the human malaria vectors Anopheles gambiae Giles and An. arabiensis Patton have distinct flight tones. If flight tone similarly distinguishes natural populations of these sympatric sibling species, it may play a role in reproductive isolation of swarms that are otherwise behaviourally identical. To assess the fidelity of flight tone differences in natural populations, flight tone was measured in the F1 progeny of mosquitoes of both species captured in western Kenya. Flight tone distributions of wild An . gambiae and An. arabiensis were similar to their laboratory conspecifics. However, interspecies comparisons of flight tone of wild mosquitoes revealed significantly different but overlapping distributions for both sexes. Furthermore, when the effect of body size on flight tone was determined, there was a positive correlation between wing length and flight tone for both sexes of An. gambiae and An. arabiensis , suggesting that mosquito size is a significant variable affecting flight tone. Although these findings diminish any practical benefit of flight tone as a diagnostic tool in species identification, its potential role in pre‐mating species recognition needs further investigation.     

Insecticide Susceptibilities of Anopheles sinensis (Diptera: Culicidae) Larvae from Paju-shi, Korea

A study was conducted to determine the susceptibility of Anopheles sinensis larvae, malaria vector, from Paju‐shi (Gyonggi‐do) to 24 pesticides including 11 pyrethroids, 11 organophosphates, 1 pyrazole analogue and another pesticide. The mosquito larvae showed the most highly susceptible to chlorfenapyr with LC₅₀ of 0.0063 ppm followed by spinosad, temephos, fenthion and beta‐cyfluthrin with 0.03, 0.0366, 0.0367 and 0.0998 ppm, respectively, and fluvalinate (>128 ppm) was the least susceptible. Also, 11 pesticides of them were compared with Goyang strain (Gyonggi‐do) of data 1992. The development of resistance was noticed to cypermethrin and permethrin as much of 73.59 and 6.23 folds at LC₅₀, respectively, and also fluvalinate was showed high resistance development. In generally, the pyrethroid insecticides were showed higher development of resistance than organophosphorus insecticides.     

Effect of larval rearing temperature on adult female morphology of Anopheles (Nyssorhynchus) albimanus (Diptera: Culicidae)

Summary

Time to pupation, percent survival to pupation, and percent adult emergence of Anopheles albimanus Wiedemann decreased at higher larval rearing temperature. Mosquitoes reared at 30°C experienced higher mortality during the pupal stage than did mosquitoes reared at 22°C. Analysis of variance revealed that wing length and costal wing spot patterns of adult female A. albimanus were affected by larval rearing temperature. Female A. albimanus reared at 22°C had longer wings, and larger basal pale + prehumeral pale, prehumeral dark, and humeral pale costal wing spots than did female siblings reared at 30°C. Female A. albimanus reared at 30°C had larger subcostal pale spots than did female siblings reared at 22°C. Analyses of 2x2 contingency tables indicated that sex ratio was independent of larval rearing temperature, whereas survival to the adult stage and coalescence of wing spots were not independent of rearing temperature. The need to examine stability of morphological characters under differing environmental conditions is discussed.     

林氏按蚊线粒体全基因组序列的测定及基于线粒体基因组的按蚊属系统发育分析(英文)

【目的】对林氏按蚊Anopheles lindesayi完整的线粒体基因组进行测序及分析,依据已知的线粒体基因组构建并讨论按蚊属蚊虫的分子系统发育关系。【方法】对林氏按蚊线粒体基因组进行测序、注释,并对其基本特征和基本组成进行分析。基于串联的13个蛋白质编码基因的核苷酸序列和氨基酸序列,用ML法和贝叶斯法构建林氏按蚊和按蚊属其他32种蚊虫的系统发育树,据此探讨按蚊属蚊虫的系统发育关系和系统分类。【结果】林氏按蚊线粒体基因组全长为15 366 bp,包含13个蛋白质编码基因,22个tRNA基因,2个rRNA基因和一段控制区。林氏按蚊线粒体基因组呈现明显的AT偏斜和GC偏斜,AT偏斜为正,GC偏斜为负。除了COX1使用TCG和ND5使用GTG作为起始密码子以外,其他蛋白质编码基因的起始密码子均遵循ATN原则;终止密码子为TAA或者T。除了tRNA^Ser(AGN)以外,其他的tRNA基因均呈现典型的三叶草二级结构。控制区AT含量最高,为94.54%。滑窗分析显示蛋白质编码基因是用于构建亚属或属水平系统发育关系的最佳分子标记。系统发育树强烈支持塞蚊亚属Cellia、按蚊亚属Anopheles、徕蚊亚属Nyssorhynchus和柯特蚊亚属Kerteszia均为单系群。小五斑按蚊An. atroparvus和四斑按蚊An. quadrimaculatus A这两个种聚到一起,从传统的形态分类上讲,它们和林氏按蚊均属于按蚊亚属按蚊系蚊虫。但本研究构建的4个系统发育树均显示,(小五斑按蚊An. atroparvus+四斑按蚊An. quadrimaculatus A)和林氏按蚊被属于迈蚊系的中华按蚊分开,这为两个系的分类提供了新的论点。【结论】本研究获得了林氏按蚊的完整的线粒体基因组,探析了按蚊属的线粒体基因组特征和系统发育关系,为进一步研究蚊科线粒体基因组和系统发育关系提供了依据。     

中华按蚊OCT家族基因的多样性及序列特征

[目的]在全基因组水平鉴定、分类和命名中华按蚊Anopheles sinensis有机阳离子转运体(organic cation transporter,OCT)家族基因,为昆虫OCT基因提供信息框架.[方法]从NCBI,VectorBase和EMBL数据库下载冈比亚按蚊An.gambiae、黑腹果蝇Drosophil...