Abstract
AbstractSalinity tolerance is an important trait that governs the ecology of disease‐vector mosquitoes by determining their choice of larval habitat, and consequently their ecological and geographical distribution. Here, we used laboratory strains to determine the osmotic responses of larvae of obligate freshwater disease‐vector mosquitoes (Aedes aegypti,Aedes albopictus,Anopheles coluzzii,An. gambiae,Culex pipiens, andCx. quinquefasciatus) and assessed their relationship with salinity tolerance. First, we analyzed the acute dose–mortality response of fourth‐instar larvae to salinity; then, we measured their hemolymph osmolality after 24‐h exposure to varying salinities. We found thatAe. albopictuswas the most tolerant species, followed byAn. coluzzii,Ae. aegypti,Cx. quinquefasciatus, andAn. gambiae, in decreasing order.Cx. pipienswas the least tolerant species. All mosquitoes were hyper‐iso‐osmoregulators, but with species‐specific differences. Specifically, hemolymph osmolality in deionized water varied among species, andCx. pipiensand the twoAedesspecies showed the lowest and highest osmolality. Although all species were osmoconformers at higher salinity values, hemolymph osmolality approached environmental osmolality more rapidly in species of theCulexgenus, compared withAedesspecies where it increased slowly. Moreover, hemolymph osmolality in deionized water was significantly correlated with tolerance to salinity across species. This could allow predicting the salinity tolerance of untested species on the basis of their osmoregulatory ability. However, this correlation disappeared when considering the hemolymph osmolality of larvae exposed to salinities higher than deionized water.
Highlights
Aquatic organisms are often confronted in their habitat with changing salinity to which they have to adapt
The relationship between osmoregulation and salinity tolerance is not well known in freshwater species, despite the fact that salinity tolerance is an important determinant of local adaptation and evolutionary history (Munoz et al 2008, Pinceel et al 2013, Arribas et al 2014)
Salinity tolerance This study investigated the salinity tolerance in larvae of six laboratory strains of the major vector mosquitoes belonging to three different genera: Ae. albopictus, An. coluzzii, Ae. aegypti, Cx. quinquefasciatus, An. gambiae, and Cx. pipiens
Summary
Aquatic organisms are often confronted in their habitat with changing salinity to which they have to adapt. In other salt-tolerant Culicidae species, osmoregulation involves morphological changes in the larval posterior and anterior rectum, and a change in the composition and location of dorsal anterior rectum (DAR) and non-DAR cells that regulate ion excretion and absorption (Bradley 1987, Smith et al 2008, Beyenbach and Piermarini 2009, Xiang et al 2012, White et al 2013) In some species, such as Aedes taeniorhynchus, the progressive exposure of mosquito larvae to increasing salinities has selected populations with different levels of adaptation to local conditions, enabling some populations to tolerate salinities in excess of seawater (Bradley and Philips 1977)
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