Salinity tolerance of Aedes camptorrhynchus (Diptera: Culicidae) from two regions in southwestern Australia

Aedes camptorhynchus (Thomson) (Diptera: Culicidae) is widely distributed throughout southwestern Australia in both coastal and inland sites, and is a vector of Ross River virus (Togoviridae: Alphavirus). Larvae of this species are most commonly found in brackish to saline and hypersaline waters. In inland southwestern Australia secondary (anthropogenic) salinisation of agricultural land has led to widespread increases in the amount and saline standing water and available breeding habitat for Ae. camptorhynchus. Given the epidemiological significance of this mosquito species it is particularly important to understand the fundamental biology in order to inform vector management and environmental remediation strategies. We therefore sought to determine the salinity tolerance of Ae. camptorhynchus larvae collected from the coastal saltmarshes (coastal) and the southern wheatbelt (inland) of Western Australia. Ae. camptorhynchus neonate larvae were collected from the two sites and then reared in seawater or water from the source locations which were manipulated to saline concentrations ranging from 2.96 to 88.8 parts per thousand (p.p.t.) by dilution or addition of NaCl. Overall, Ae. camptorhynchus tolerated a wide range of salinities. The majority of Ae. camptorhynchus from the inland site that survived to adulthood did so at salinities between 8 and 30 p.p.t., whereas the majority of coastal mosquitoes that survived to adulthood did so in salinities between 22 and 52 p.p.t. Larvae were able to complete development in salinities up to 62 p.p.t., but none survived to adulthood at higher salinities. An increase in the number and distribution of Ae. camptorhynchus, associated with rising salinity, in previously freshwater habitats of inland southwestern Australia could have health consequences by increasing the potential for Ross River virus activity.