Mosquito (Diptera: Culicidae) Diversity and Community Structure in Doi Inthanon National Park, Northern Thailand

Urbanization and human activities create new suitable aquatic habitats for the immature stages of mosquitoes in many countries. This also applies to Doi Inthanon National Park in northern Thailand, which is named for the highest mountain in the country. Despite its popularity, there is no information regarding mosquito diversity and community structure in the different ecosystems of the park. Monthly collections of immature stages from various habitats were conducted from August 2004 to December 2005 using dipping and sucking methods. The specimens collected from each habitat were reared to adults and identified based on their morphology. Diversity parameters and community structure were statistically analyzed. A total of 140 species (3795 specimens) belonging to 15 genera were identified. Among these, four genera (Culex, Aedes, Anopheles, and Uranotaenia) had high species richness, each represented by 48, 27, 19, and 15 species, respectively. Aedes albopictus was the most relatively abundant species, representing 6.7% of the total number of captured specimens, followed by Tripteroides aranoides (5.6%) and Cx. mimulus (5%). Species richness in natural habitats was significantly higher than in artificial containers. Species richness and abundance were highest in the rainy season. In comparison to agricultural areas and villages, mosquito diversity was found to be higher in forest areas. Ground pools, stream pools, rock pools, bamboo stumps, bamboo internode, and rice fields were the most preferred natural habitats. The results indicate that Doi Inthanon National Park has a high mosquito diversity. Each species exhibits differences in abundance and distribution in different habitats, which is useful information for planning conservation measures and vector control in the park.

Illustrated keys to the mosquitoes of Thailand. VI. Tribe Aedini

Illustrated keys for the identification of the fourth-instar larvae and adult females of the mosquito species of tribe Aedini in Thailand are presented, along with the geographic distribution of the species and the known habitats of their immature stages. The keys are the first to encompass the recent revisionary studies of tribe Aedini. One hundred and seventy-five species of Aedini belonging to 38 genera and 18 subgenera are recognized in Thailand. Two species of genus Armigeres, two of genus Collessius, and one of genus Downsiomyia are undescribed. Himalaius simlensis [formerly Aedes (Finlaya) simlensis], Hopkinsius (Yamada) albocinctus [formerly Aedes (Finlaya) albocinctus], Downsiomyia nipponica and Downsiomyia saperoi [formerly species of Aedes (Finlaya)], and Hulecoeteomyia pallirostris [formerly Ochlerotatus (Finlaya) pallirostris] are new country records. Aedimorphus (formerly a subgenus of Aedes), Cancraedes, and Rhinoskusea (formerly subgenera of Ochlerotatus) are recognized as genera, and genus Petermattinglyius includes species previously included in Diceromyia (formerly a subgenus of Aedes) in Thailand. Heteraspidion, Huangmyia, Stegomyia, and Xyele are newly recognized subgenera of genus Stegomyia (formerly a subgenus of Aedes), which includes eight species without subgeneric placement. Two unidentified and unplaced species were discovered in Thailand.

Molecular and cytogenetic evidence of three sibling species of the Anopheles barbirostris Form A (Diptera:Culicidae) in Thailand

Nine isoline colonies of Anopheles barbirostris Form A, derived from individual isofemale lines from Chiang Mai, Phetchaburi, and Kanchanaburi, were established in our insectary at Chiang Mai University. All isolines shared the same mitotic karyotype (X(1), X(2), Y(1)). Molecular analysis of deoxyribonucleic acid (DNA) sequences and polymerase chain reaction (PCR) products of ITS2, COI, and COII regions revealed three distinct groups: A1 (Chiang Mai), A2 (Phetchaburi), and A3 (Kanchanaburi). Crossing experiments among the three groups exhibited strong reproductive isolation, producing low and/or non-hatched eggs, and inviable and/or abnormal development of the reproductive system of F(1)-progenies. Asynaptic regions along the five polytene chromosome arms of F(1)-hybrid larvae clearly supported the existence of three sibling species within A. barbirostris Form A, provisionally named species A1, A2, and A3.

Illustrated keys to the mosquitoes of Thailand V. Genera Orthopodomyia, Kimia, Malaya, Topomyia, Tripteroides, and Toxorhynchites

Illustrated keys for the identification of the fourth-instar larvae and adults of species representing six genera of mosquitoes in Thailand are presented, along with information about the geographic distribution of the species and the habitats occupied by their immature stages. Fifty-nine species belonging to genera Orthopodomyia, Kimia, Malaya, Topomyia, Tripteroides, and Toxorhynchites are recognized. Topomyia argyropalpis, To. bifurcata, To. gracilis, To. spathulirostris, To. tenuis, To. tipuliformis, and To. vijayae are included as new country records, and ten undescribed species, four in Topomyia, four in Toxorhynchites, and two in Tripteroides, are recognized.

Illustrated keys to the mosquitoes of Thailand. IV. Anopheles

Illustrated keys for the identification of the larvae and adult female Anopheles mosquitoes of Thailand are presented along with distribution maps, tabulated bionomics information, and a checklist. A total of 73 species are treated, including 71 previously and newly described species (An. cracens = dirus B, An. scanloni = dirus C, An. baimaii = dirus D, An. latens = leucosphyrus A, and An. epiroticus = sundaicus A). Also, two undescribed species are included, i.e., An. minimus C and a new species near An. gigas. Thirty-four chromosomal forms of 14 species are discussed, with suggestions provided for resolving their taxonomic status.

Illustrated keys to the mosquitoes of Thailand III. Genera Aedeomyia, Ficalbia, Mimomyia, Hodgesia, Coquillettidia, Mansonia, and Uranotaenia

Illustrated keys for the identification of fourth-instar larvae and adult females of seven genera of mosquitoes are presented, along with the geographic distribution of each species and the known immature habitats. Sixty-seven mosquito species belonging to genera Aedeomyia, Ficalbia, Mimomyia, Hodgesia, Coquillettidia, Mansonia, and Uranotaenia are recognized in Thailand. Hodgesia bailyi and Uranotaenia (Pfc.) abstrusa are included as new country records, and four new undescribed species in the subgenus Uranotaenia are reported.

Aedine mosquito species (Diptera: Culicidae: Aedini) occurring in Thailand with their current generic and subgeneric status, and new country records

A list of the currently valid generic and species-level taxa of tribe Aedini in Thailand is provided. Its purpose is to enable entomologists, public health personnel and mosquito control workers to more quickly become familiar with recent formal taxonomic changes within the tribe. New country records of four species of Armigeres are reported.

Illustrated keys to the mosquitoes of Thailand I. Background; geographic distribution; lists of genera, subgenera, and species; and a key to the genera

This is the first of a series of six sections that will cover 436 species of mosquitoes currently known to occur in Thailand. In this section we provide information on the background, geographic distribution, bionomics, lists of genera, subgenera, and specie of mosquitoes that occur in Thailand, and a key to the genera. The sections, listed below will be published as separate supplements in following issues of this journal: II. Key to the Culex; III. Key to the Aedeomyia, Ficalbia, Mimomyia, Hodgesia, Coquillettidia, Mansonia, and Uranotaenia. The additional 3 supplements consisting of the Key to the Tribe Aedini; Key to the Anopheles; and the Keys to the Armigeres, Heizmannia, Orthopodomyia, Malaya, Topomyia, Tripteroides, and Toxorhynchites will be published as they are completed. At the conclusion of this project, one large supplement to the Southeast Asian Journal of Tropical Medicine and Public Health will be produced that includes all of these keys in a single document.

Illustrated keys to the mosquitoes of Thailand. II. Genera Culex and Lutzia

Illustrated keys for the identification of the fourth-instar larvae and adult females of the mosquito genera Culex and Lutzia is presented, along with information on the geographic distribution of each species, and bionomics. Eighty-two species belonging to subgenera Culex, Culiciomyia, Eumelanomyia, Lophoceraomyia, and Oculeomyia of genus Culex, and three species belonging to subgenus Metalutzia of genus Lutzia are recognized in Thailand. Subgenus Oculeomyia includes a probable new species near Cx. infula and Lt. vorax is recognized as a new country record.

Estimates of gene flow among Anopheles maculatus populations in Thailand using microsatellite analysis

We report an analysis of seven microsatellite loci in eight populations of Anopheles maculatus mosquitoes dispersed over a distance of approximately 1,100 km in Thailand. A wide spectrum of genetic variability, with mean heterozygosities ranging from 0.738 to 0.847 were found. Based on microsatellite analysis, geographic populations of An. maculatus can be grouped into two clusters; one includes upper and lower northern populations that extend from approximately 11 degrees to 16 degrees north latitude, and the other (southern populations) extends south from about 7 degrees to 6 degrees north latitude. Wright's F(ST) and Slatkins's R(ST) for all seven microsatellite loci indicated low estimates of differentiation among all populations (mean values of F(ST) and R(ST) = 0.0406 and 0.051, respectively, corresponding to the Nm values of 5.91 and 4.65, respectively), and suggested that gene flow occurs among populations. However, there is some restriction of gene flow between the northern and southern populations. Geographic barriers could be limiting factors for greater gene flow between populations.

Sequence heterogeneity in copia-like retrotransposons in Anopheles (Diptera: Culicidae) in Thailand

Degenerate primers and the polymerase chain reaction (PCR) detected a conserved region of copia-like reverse transcriptase from Anopheles mosquitoes in Thailand. A total of 43 subclone PCR fragments of the size expected for reverse transcriptase of copia-like elements was isolated from Anopheles dirus (Peyton & Harrison) subspecies A, Anopheles maculatus (Theobald) subspecies E, Anopheles nivipes (Theobald), and Anopheles subpictus Grassi. Sequence analysis of subclones confirmed the identity of these sequences as copia-like reverse transcriptase sequences. The sequences displayed varying degrees of sequence heterogeneity, in contrast to the limited diversity seen in copia-like elements in Drosophila. Phylogenetic analysis of the amino acid sequences of the subclones showed that the majority of the retroelements were clustered together, implying that sequence divergence during vertical transmission of the copia-like retrotransposons has been a major factor in the evolution of copia-like retroelements in Anopheles species. Additionally, there is evidence that horizontal transfer of this transposon group among certain divergent taxa also may have played a role in their evolution.

Metaphase karyotypes of Anopheles of Thailand and Southeast Asia. VI. The Pyretophorus and the Neomyzomyia series, subgenus Cellia (Diptera:Culicidae)

A total of 6 species of the Pyretophorus (4 species) and Neomyzomyia (2 species) series of the subgenus Cellia of Anopheles were used for metaphase karyotype analysis. Anopheles subpictus and An. vagus exhibit 4 and 2 forms of mitotic karyotypes, respectively, which are attributable to different types of Y chromosomes. Such distinctive mitotic chromosomes may reflect interspecies differences within each of these 2 taxa. Two distinct species, An. indefinitus and An. sundaicus, show similar metaphase karyotypes, particularly with regard to the size and shape of the sex chromosomes. Likewise, An. tessellatus and An. kochi, which are distinct species of the Neomyzomyia Series, also have metaphase karyotypes that resemble each other. They exhibit a typical feature of telocentric sex chromosomes resembling those of the An. dirus complex and the other species of the Leucosphyrus Group. Like the other cases of the Oriental Anopheles, heterochromatin has played a significant role in chromosome evolution of the 6 species.

Microsatellite polymorphism in Anopheles maculatus, a malaria vector in Thailand

Dinucleotide microsatellites were characterized from Anopheles maculatus, a species of mosquito that transmits malaria. A partial genomic library of An. maculatus, consisting of 3,960 kilobases (kb), was screened with either (GT)12 or (CT)12 probes. Approximately 1.5% of the recombinants contained sequences that hybridized to either (GT)12 or (CT)12 dinucleotide probes, suggesting that microsatellites are abundant in the genome of An. maculatus. Estimation of abundance of the two dinucleotide repeats revealed that (GT)n or (CA)n microsatellites occur on average every 68 kb and (CT)n or (GA)n repeats every 495 kb. Among 23 microsatellite loci sequenced, four loci were selected to synthesize primers to perform polymerase chain reaction scoring for genetic polymorphism in a population of An. maculatus. A high level of polymorphism was observed with all four microsatellite loci analyzed. The number of alleles detected at each locus ranged from eight to 12 and the heterozygosities ranged from 0.25 to 0.54. A total of 42 alleles were found among four microsatellite loci. The large number of alleles and polymorphic nature resolved from microsatellite loci make these markers valuable for the study of population genetic structure and gene flow. Knowledge of gene flow is required to develop vector control strategies using genetic manipulations of malaria vector populations.

Observations on nocturnal biting activity and host preference of anophelines collected in southern Thailand

Over a 13-month period, 5,127 adult female mosquitoes were collected on human bait during multiple collecting periods between 1800 and 0600 h in 5 villages in southern Thailand. There were marked differences in the biting activity of different species at each of the villages studied. Anopheles maculatus and Anopheles sawadwongporni were collected most often at dusk or in the first hours of darkness between 1800 and 2100 h. Although specimens of Anopheles dirus were collected consistently between 1900 and 0400 h, peak collections were made between 2000 and 2300 h. Anopheles minimus was collected consistently throughout the night without a clearly discernible peak. Of more than 2,400 Anopheles mosquitoes collected in CDC light traps, 133 specimens (5.4%) contained blood, nearly all of which was identified by enzyme-linked immunosorbent assay (ELISA) to be of bovine origin. Ten specimens contained blood from more than one host species.

Seasonal abundance and parity rates of Anopheles species in southern Thailand

Mosquitoes were collected with human bait, animal bait, and CO2-baited light traps during a 13-month period in 5 villages located along the Myanmar border in southern Thailand. Altogether, 11,608 adult females consisting of 21 anopheline species were collected. Abundance of species varied according to the village where collections were made. In one village that was studied most intensely, Anopheles minimus was the most commonly collected species, representing 55.6, 10.6, and 56.5% of the human bait, cattle bait, and light trap collections, respectively. In addition, An. minimum was abundant throughout the year, whereas Anopheles maculatus was most commonly collected in July and August coincident with the rainy season. Anopheles sawadwongporni, abundant at the beginning and the end of the rainy season, was most commonly collected in June. Anopheles dirus was most abundant in April; however, it represented only 3.6% of all mosquitoes collected that month. Of 813 females collected in Palao-U Village and dissected, 38.9% were parous.

Metaphase karyotypes of Anopheles of Thailand and Southeast Asia: V. The Myzomyia Series, subgenus Cellia (Diptera:Culicidae)

Metaphase karyotypes of 9 species of the Myzomyia Series show intra- and interspecific differences based on quantitative variation and distribution of constitutive heterochromatin in the sex chromosomes or the centromeric regions of the autosome pairs or both. Anopheles jeyporiensis and Anopheles aconitus each exhibit 4 forms of mitotic karyotypes, which may reflect interspecific differences within each taxon. The well-defined genetic species within the Anopheles minimus and the Anopheles culcifacies complexes clearly exhibit distinctive metaphase karyotypes that can be used as diagnostic characters for separating these sibling species, which are difficult to identify by morphological criteria alone. Our analysis on metaphase karyotypes of Anopheles pampanai, Anopheles varuna, and Anopheles flavirostris also confirms their morphological identification based on heterochromatin differences in the sex chromosomes and autosome 2.

Detection of Plasmodium vivax and Plasmodium falciparum circumsporozoite antigen in anopheline mosquitoes collected in southern Thailand

During a 13-month study on the ecology of malaria vectors in five villages in southern Thailand, Anopheles specimens collected on human-bait, bovid-bait, and in light traps were tested for the presence of Plasmodium vivax and P. falciparum circumsporozoite antigen by enzyme-linked immunosorbent assay. Plasmodium vivax antigen was detected in seven specimens and P. falciparum in 21 specimens, together representing 0.4% of the 7,938 specimens tested. In one village, Palao-U, circumsporozoite antigen was detected in 16 (0.7%) of the 2,196 specimens tested. In this village, combined rates of infection with P. falciparum and P. vivax were 0.6% for An. minimus, 1.1% for An. sawadwongporni, and 1.5% for An. maculatus. Circumsporozoite antigen was also detected in An. dirus, An. nivipes, An. barbirostris group, and An. hyrcanus group specimens. Combined P. falciparum and P. vivax entomologic inoculation rates in the wet season (March-October) were 0.05 for An. minimus, An. maculatus, and An. dirus, but 0 for An. sawadwongporni. Rates were higher in the dry season (November-February): 0.26 for An. minimus, 0.13 for An. maculatus, 0.13 for An. sawadwongporni, and 0 for An. dirus. The vectorial capacity, calculated based on human biting rate and rate of survival, of An. minimus during the dry season was more than two-fold higher than that of An. maculatus, the species with the second highest vectorial capacity.

Larval habitats of malaria vectors and other Anopheles mosquitoes around a transmission focus in northwestern Thailand

We sampled 199 bodies of water for Anopheles larvae around a malaria-endemic village near Mae Sot, Thailand, over 2 years. Anopheles dirus species A and D occurred in 54 small, well-shaded, stream and temporary ground pools. The larval habitat of species D is reported for the first time. Anopheles minimus species A occurred in 8 samples from slow-moving streams, in 8 from rice fields, and in 2 from ground pools. Anopheles pseudowillmori occurred in one sample from a ground pool, in 3 from streams, and in 9 from rice fields.

Metaphase karyotypes of Anopheles of Thailand and Southeast Asia: IV. The Barbirostris and Umbrosus species Groups, subgenus Anopheles (Diptera: Culicidae)

Metaphase karyotypes of 2 and 3 species of the Umbrosus and the Barbirostris Groups, respectively, of the subgenus Anopheles occurring in Thailand and Indonesia show inter- and intraspecific differences with respect to the amount and distribution of constitutive heterochromatin in the sex chromosomes and/or autosomes. Four forms of metaphase karyotypes have been recognized in the wild samples of Anopheles barbirostris based on differences in size and shape of X and Y chromosomes. It is not known whether forms A, B, and C of the metaphase karyotype of An. barbirostris found in Thailand represent inter- or intraspecific differences. However, form D, which occurs only in Indonesia, may represent a mitotic karyotype of a distinct species closely related to An. barbirostris. Anopheles campestris and An. barbumbrosus are each readily separated from An. barbirostris by mitotic chromosomes. Anopheles umbrosus and An. letifer of the Umbrosus Group also exhibit heterochromatin variation in the X chromosomes. These 2 species can be readily distinguished by the gross morphology of mitotic karyotypes, particularly the X and Y chromosomes.

Metaphase karyotypes of Anopheles of Thailand and Southeast Asia: I. The Hyrcanus Group

Metaphase karyotypes of 6 species of the Hyrcanus Species Group of the subgenus Anopheles show constitutive heterochromatin variation in X and Y chromosomes. Anopheles peditaeniatus exhibits the most extensive variation in the size and shape of heterochromatic sex chromosomes, with 3 types of X and 5 types of Y chromosomes. Anopheles nitidus shows the least variation, with only 2 types of X chromosomes. Anopheles sinensis and An. crawfordi each have 2 forms of metaphase karyotype in the heterochromatin of the Y chromosome. It is not known whether the 2 forms of metaphase karyotype in these 2 species represent inter- or intraspecific differences. The 2 forms of heterochromatic sex chromosomes observed in An. argyropus and An. nigerrimus may suggest the existence of sibling species complexes within each of these species.