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

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?

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.

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,

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.

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.

RESULTS 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.

RESULTS %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.

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.

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).

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.

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.

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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