| Summary: | <p>Abstract</p> <p>Background</p> <p><it>Anopheles subpictus sensu lato</it>, a widespread vector of malaria in Asia, is reportedly composed of four sibling species A-D based on distinct cytogenetic and morphological characteristics. However <it>An. subpictus </it>species B specimens in Sri Lanka are termed <it>An. subpictus </it>B/ <it>An. sundaicus </it>because of recent genetic data. Differences in salinity tolerance and coastal/inland prevalence of <it>An. subpictus </it>sibling species that were not previously established in Sri Lanka are presented here.</p> <p>Results</p> <p>Specimens with morphological characteristics of all four Indian <it>An. subpictus </it>sibling species were found in Sri Lanka. Sibling species A, C and D tended to be predominant in inland, and <it>An. subpictus </it>species B/<it>An. sundaicus</it>, in coastal localities. Sibling species C was predominant in both adult and larval inland collections. Larvae of <it>An. subpictus </it>B/<it>An. sundaicus </it>were found in inland and coastal sites, including a lagoon, with salinity varying from 0 to 30 ppt. <it>An. subpictus </it>sibling species A, C and D larvae were present in water of salinity between 0 to 4 ppt. <it>An. subpictus </it>C, D and <it>An. subpictus </it>B/<it>An. sundaicus </it>larvae showed compatible differential salinity tolerance in laboratory tests. The first instar larvae of <it>An. subpictus </it>B/<it>An. sundaicus </it>showed 100% survival up to 15 ppt in comparison to species C and D where the corresponding values were 3 ppt and 6 ppt respectively. However all third instar larvae of <it>An. subpictus </it>B/<it>An. sundaicus </it>survived up to 30 ppt salinity whereas <it>An. subpictus </it>C and D tolerated up to 4 ppt and 8 ppt salinity respectively.</p> <p>Conclusions</p> <p>The results suggest that <it>An. subpictus </it>species B/<it>An. sundaicus </it>breed in fresh, brackish and nearly saline water while <it>An. subpictus </it>species C and D do so in fresh and less brackish waters in Sri Lanka, as in India. Because of the established role of <it>An. sundaicus s.l</it>. and <it>An. subpictus s.l</it>. as malaria vectors, the findings indicate a need for greater monitoring of brackish water breeding habitats in Asia. Tolerance to 15 ppt salinity may also constitute a simple method for differentiating <it>An. subpictus </it>B/<it>An. sundaicus </it>larvae from those of <it>An. subpictus </it>species C and D in field studies.</p>
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