Water quality and immatures of the M and S forms of Anopheles gambiae s.s. and An. arabiensis in a Malian village

Immatures of An. arabiensis, An. gambiae s.s., and its M and S forms were sampled every alternate day for a month in mid-rainy season from three sampling sites in each of the larval breeding habitats (rock pools, swamp, and puddles). Water quality was characterized by alkalinity, conductivity, dissolved oxygen (D.O.), nitrate, orthophosphate, pH, temperature, total dissolved solids (TDS), and turbidity. A type 3 analysis of the GENMOD model was used to examine the associations between the proportional frequencies of young (first and second instar larvae) and old (third and fourth instar larvae and pupae) or total immatures of species or forms among sampling sites within and among larval breeding habitats during a category of rainfall as influenced by water quality.

Of the 4,174 immatures sampled, 1,300 were molecularly identified to species and forms. Significant association between the proportional frequencies of young larvae of An. arabiensis, An. gambiae s.s., its M and S forms was found among sampling sites within habitats but not among larval breeding habitats. The proportional frequencies of young larvae of M and S forms varied daily perhaps due to recruitment, mortality, and dispersal within habitats. Conductivity and TDS had significant effects when the proportional frequencies of young larvae of M and S forms among sampling sites within habitats were significantly associated. Alkalinity, D.O., orthophosphate, pH, nitrate, temperature and turbidity had no effects on niche partitioning of species and forms among sampling sites within habitats. Rainfall did not affect the frequencies of these immatures.