| Background and ObjectivesMosquito-borne diseases have been epidemic in Guangdong province,but mosquito investigation is lacking especially in the Eastern Region with dated and not correctly recorded mosquito fauna literatures. Our mosquito investigation was carryed out in the villages and the suburb of East Guangdong province for understanding mosquito distribution in the region.Micronecta formosana Matsumura was found coincidently in the investigation, which is as a natural enemy of mosquito larvae. Micronecta formosana belongs to genus Micronecta,family Corixidae , infraorder Nepomorpha, order Hemiptera of Class Insecta.There is no gene information available about Micronecta formosana in GenBank. In addition, the position of Corixidae and the phylogenetic relationships among the families in infraorder Nepomorpha have been controversial. The phylogenetic relationships of these water bugs and potentiality to use Micronecta formosana for mosquito control were explored.For understanding the relation between salivary gland proteins and disease transmission,salivary gland proteins were analyzed on Ae.albopictus Skuse and Ar.subalbatus Coquillett.Methods(1) Mosquito larvae and pupae were collected intermittently with 14 times in 8 different areas from September 2007 to November 2009 in East Guangdong province. Species were identified according to taxonomy of adults and 4th instar larvae.(2) Predation of Micronecta formosana was observed on three prey species: Cx. wilfedi Colless, Ae.macfarlanei Edwards and Ae.albopictus Skuse in the Laboratory.(3) PCR were performed to amplify partial 18S rDNA and 28S rDNA sequences of Micronecta formosana. Phylogenetic trees were built based on partial 28S rDNA sequences of 45 species, including 43 species of 11 families in infraorder Nepomorpha and 2 outgroup species.(4) Two-dimensional electrophoresis was used to detect species or gender difference of Ae.albopictus and Ar.subalbatus adults.Results(1) 10 collected mosquito species were Cx.pipiens quinquefasciatus Say, Cx.torrentium Martini, Cx.tritaeniorhynchus Giles, Cx.pallidothorax Theobald, Cx.shebbearei Barraud, Cx.wilfredi, Ae.albopictus,Ae.macfarlanei, Ar.subalbatus, and Lutzia.fuscanus Wiedemann.(2) 24h Predation : The prey capacity of Micronecta formosana was stronger on Cx.wilfedi than on Ae.macfarlanei (P<0.017); The capacity difference was not found between Cx.wilfedi and Ae.albopictus (P>0.017), or betweeen Ae.albopictus and Ae.macfarlanei (P>0.017). Micronecta formosana prefered 1st and 2nd larvae to 3rd and 4th larvae or pupae (P<0.003 and P<0.017).There were no prey difference between 3rd and 4th larvae and pupae (P>0.017). There was no survival ability difference of Micronecta formosana in series dilution river water (10-1, 10-2, 10-3, 10-4)(P>0.05), but the difference was existed in original river water and breeding ground water (P<0.05).(3) One 18S rDNA and two 28S rDNA partial sequences were amplified by PCR and sequenced and obtained GenBank numbers HM038007,HM038008 and HM038009. Phylogenetic analysis showed Micronecta formosana belonging to family Corixidae with the highest identity with Diaprepocoris barycephalus Kirkaldy (92.8%). Corixidae is as a sister group to Aphelocheiridae and Naucoridae. The infraorder Nepomorpha is grouped into six superfamilies (11 families): Corixoidea (Corixidae), Naucoroidea (Naucoridae+Aphelocheiridae), Notonectoidea (Notonectidae+Potamocoridae), Pleoidea (Pleidae+Helotrephidae), Ochteroidea (Ochteridae+Gelastocoridae). Nepoidea (Nepoidae +Belostromatidae).(4) Salivary gland proteins analysis with two-dimensional electrophoresis: There were eight female salivary gland proteins existed in Aedes albopictus. Three of the eight were also found in female Ar.subalbatus. The other five were uniquely existed in female Ae. albopictus.Conclusions(1) Investigation renewed mosquito information with three new record species in the Province. Dominant pecies were Ae.albopictus ,Ar.subalbatus and Lu.fuscanus in residential areas. The important disease transmitting vectors are Ae.albopictus for Dengue and Chikungunya Cx.pipiens quinquefasciatus for lymphatic filariasis and Japanese Encephalitis, Cx.tritaeniorhynchus for Japanese Encephalitis and Ar.subalbatus for heartworm disease(Dirofilariaimmitis), which which implied us to increase prevention and monitor to these mosquito- borne diseases.(2) Micronecta formosana was an effective predator for different instar larvae of different species mosquitoes. It has good viability in different environment and it is a hopeful candidate of mosquito biological control.(3) Corixidae belongs to a sister group with Aphelocheiridae and Naucoridae. There are four controversial families as Pleoidae, Aphelocheiridae, Potamocoridae and Helotrephidae. The results support Pleoidae belonging to superfamily Pleoidea still in the infraorder Nepomorpha, Helotrephidae to superfamily Helophhidea, Aphelocheiridae to superfamily Naucoroidea with Naucoridae, and Potamocoridae to superfamily Notonectoidea with Notonectidae.(4) The results of two-dimensional electrophoresis suggest the five unique salivary gland proteins in female Ae.albopictus should be related with dengue and other aedine transmitting diseases. The other three female unique proteins may be related with molecular basis of blood sucking mechanism.
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