1. Nur Faeza A Kassim *, C.E. Webb, R.C. Russell, Qinning Wang Department of Medical Entomology, University of Sydney & Westmead Hospital, Australia. Culex molestus and implications for mosquito-borne disease risk in Australia

2. BACKGROUND  Culex pipiens subgroup of mosquitoes includes some of the most important vector species internationally.  4 species in Australia including Culex molestus (Forskal).  Culex molestus closely associated with subterranean urban environments.  Introduced into Australia in 1940s during WWII, with US military movement in Melbourne.  Will this species play a role in the transmission of exotic arboviruses such as West Nile virus and endemic arboviruses such as Murray Valley encephalitis virus.  Risk for urban water storage?

3. AIMS  To better understand the biology of this species, in particular, the biological factors that predispose this species to be a potentially important urban pest species.  An understanding of the biology and ecology of this species is crucial for the establishment of laboratory colonies and further experimentation.  To investigate the genetic similarity of Culex molestus within Australia and overseas.

4. METHODS  A laboratory colony of Culex molestus was established from field collected specimens from Sydney region.  A series of controlled laboratory experiments were conducted to investigate:  Mating  Adult nutritional influence on fecundity  Oviposition (egg-laying) preference  Temperature & nutritional influence on larval development Nur Faeza A Kassim, Cameron E Webb and Richard C Russell (2012) Culex molestus Forskal (Diptera: Culicidae) in Australia: colonization, stenogamy, autogeny, oviposition and larval development. Australian Journal of Entomology 51, 67-77.

5. RESULTS 95%  Approximately 95% of all female Culex molestus laid their first batch of eggs without taking a blood meal indicating the species is strongly autogenous.  Females delayed their first blood meal until after their autogenous egg raft had been laid, despite the availability of a host.

6. RESULTS % MATED MOSQUITOES  All adult mosquitoes successfully mated (as indicated by the detection of viable sperm) in confined spaces indicating Culex molestus is strongly stenogamous.

7. RESULTS 0 20 40 60 80 100 120 AutogenyBlood fed Number of eggs per egg raft  All females readily took a blood meal prior to developing their second batch of eggs with post-blood feeding egg rafts significantly (P<0.05) larger than autogenous egg rafts.

8. RESULTS 0 5 10 15 20 25 0%50%100% Oviposition water quality (percentage of hay infusion) Number of egg rafts  The females did not display a preference for highly organic oviposition water indicating and readily laid eggs in clean water.

9. RESULTS MEAN AUTOGENY RATE (% Mosquitoes with eggs without blood meal) Larval development rates were reliant on temperature rate but adults emerging from larvae raised at a mean daily temperature of 12.0 o C maintained the ability to lay autogenous egg rafts.

10. METHODS Mosquito genetic analysis: -  DNA Extraction (95 mosquito specimens from 19 locations).  Microsatellite as a genetic marker.  7 Primers: CQ11, CQ26, CxpGT4, CxqGT4, CxpGT46, CxpGT12 & CxqGT6b.  Polymerase Chain Reaction (PCR) amplification.  Capillary gel electrophoresis of amplified PCR products.  Using UPGMA to generate a dendrogram (TPGA).

11. RESULTS A dendrogram based on allele size frequencies of seven genetic loci by unweighted pair-group method with arithmetic average. The numbers at the nodes indicate the 100 replicate bootstraps.

12. CONCLUSIONS  Culex molestus is perfectly adapted to urban environments.  This adaptation allows the mosquito to remain active throughout the year and in close contact with humans.  The delay of blood feeding until post-autogenous egg-laying may reduce risk of arbovirus transmission.  Culex molestus specimens from Australia had a strong genetic similarity and they were close related compared with Culex molestus specimens from overseas.  Further investigation is required to determine the importance of this species and their habitats to mosquito-borne disease risks.

13. ACKNOWLEDGEMENTS  Merilyn Geary and Karen Willems of Department Medical Entomology for their advice and assistance on colonisation techniques.  Sydney Olympic Park for mosquito collections.  Australian Entomological Society (AES) for Student Travel Support.  Malaysia Government for a national grant for graduate work in Australia.

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