THE EVOLUTION OF INCREASED SALINITY TOLERANCE IN LARVAE OF AEDES MOSQUITOS - A PHYLOGENETIC ANALYSIS

The osmoregulatory abilities of the larvae of two species of mosquito, Aedes nigro-maculis and Aedes melanimon, were examined. Both species are closely related to known saline-tolerant species. We examined the saline tolerance of these two species by performing survival tests in water ranging from 10% to 100% seawater. Aedes nigromaculis showed inc reased mortality above 30% seawater, while A. melanimon showed high ra tes of survival in all salinities tested Fluorescence and electron mic roscopic studies reveal the presence of a single rectal segment in A. nigromaculis larvae, as is characteristic of obligate freshwater speci es, and two distinct rectal segments in A. melanimon, as is characteri stic of euryhaline osmoconforming larvae. Information on the physiolog ical capacities of these two species, along with a similar knowledge o f other key species, allowed us to map physiological information on a previously established phylogeny. Our results demonstrate the usefulne ss of physiological and morphological information in elucidating the e volutionary history of this group.