Abstract
BackgroundAedes aegypti mosquito, the principal global vector of arboviral diseases, lays eggs and undergoes larval and pupal development to become adult mosquitoes in fresh water (FW). It has recently been observed to develop in coastal brackish water (BW) habitats of up to 50% sea water, and such salinity tolerance shown to be an inheritable trait. Genomics of salinity tolerance in Ae. aegypti has not been previously studied, but it is of fundamental biological interest and important for controlling arboviral diseases in the context of rising sea levels increasing coastal ground water salinity.ResultsBW- and FW-Ae. aegypti were compared by RNA-seq analysis on the gut, anal papillae and rest of the carcass in fourth instar larvae (L4), proteomics of cuticles shed when L4 metamorphose into pupae, and transmission electron microscopy of cuticles in L4 and adults. Genes for specific cuticle proteins, signalling proteins, moulting hormone-related proteins, membrane transporters, enzymes involved in cuticle metabolism, and cytochrome P450 showed different mRNA levels in BW and FW L4 tissues. The salinity-tolerant Ae. aegypti were also characterized by altered L4 cuticle proteomics and changes in cuticle ultrastructure of L4 and adults.ConclusionsThe findings provide new information on molecular and ultrastructural changes associated with salinity adaptation in FW mosquitoes. Changes in cuticles of larvae and adults of salinity-tolerant Ae. aegypti are expected to reduce the efficacy of insecticides used for controlling arboviral diseases. Expansion of coastal BW habitats and their neglect for control measures facilitates the spread of salinity-tolerant Ae. aegypti and genes for salinity tolerance. The transmission of arboviral diseases can therefore be amplified in multiple ways by salinity-tolerant Ae. aegypti and requires appropriate mitigating measures. The findings in Ae. aegypti have attendant implications for the development of salinity tolerance in other fresh water mosquito vectors and the diseases they transmit.
Highlights
Aedes aegypti mosquito, the principal global vector of arboviral diseases, lays eggs and undergoes larval and pupal development to become adult mosquitoes in fresh water (FW)
Chitinbinding properties are ascribed to RR-1, RR-2, CPAPs, CPCFC, CPFL and TWDL families [39]
Our results showed that the chitin-binding RR-1 and RR-2 family proteins were prominent among all the cuticle proteins and the 21 brackish water (BW)-specific cuticle proteins identified in shed Fourth instar larva (L4) cuticles
Summary
The principal global vector of arboviral diseases, lays eggs and undergoes larval and pupal development to become adult mosquitoes in fresh water (FW). From an origin in tropical forests where it blood fed on animals, Aedes aegypti adopted a preference for developing near human habitations and blood feeding on humans, and spread widely to become the principal vector of important arboviral diseases including dengue, chikungunya, yellow fever, and Zika [1,2,3] It is regarded as an obligate fresh water (FW) mosquito that lays eggs (oviposits) and undergoes larval and pupal (preimaginal) development in natural (e.g. rainwater pools, leaf axils) and anthropogenic (e.g. water storage tanks, discarded containers) FW collections near human habitation [4,5,6,7,8]. Genetic changes for salinity tolerance can rapidly spread among Ae. aegypti populations within this small peninsula, increasing the transmission and prevalence of dengue and chikungunya that are endemic in the peninsula [9, 18, 24]
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