Semi-field experiments highlight importance of maize and rice pollen on oviposition site choice and larval development in An. arabiensis

Background Members of the Anopheles gambiae complex such as Anopheles gambiae s.s., Anopheles coluzzii , and Anopheles arabiensis are among the key malaria vectors in sub-Saharan Africa. These species are often abundant in areas of intense rice and maize farming with temporary water pools reflecting the dependence of their larvae on the pollen shed in such pools as food. This study explored the oviposition preference of wild-caught gravid An. arabiensis in response to maize and rice pollen in artificial aquatic habitats in a semi-field system. Methods Experimental breeding habitats were set-up in two large compartments of a semi-field system. Rice and maize pollen were respectively added in eight randomly selected habitats in both compartments while the other eight were used as control without pollens. Forty gravid An. arabiensis were released in each compartment and left overnight to choose egg-laying habitats. Consequently, eggs were sampled and counted. A second experiment was conducted following a similar procedure above and the counted eggs were returned to the respective habitats and the development of the resultant larvae were monitored and recorded until pupation. Results Pollen types strongly affected the oviposition behaviour of gravid An. arabiensis . Females preferred to lay eggs in habitats with rice pollen on the water surface over those with maize pollen, and in habitats with maize pollen over pollen-less controls. The development of larvae was significantly affected by the type of pollen in the habitats. The highest total number of An. arabiensis offspring were produced in habitats with rice pollen than maize and those with no pollen. However, larval development success was comparatively lower in habitats containing rice pollen than those with maize and without pollen suggesting that habitats with rice pollen were overcrowded. Conclusion This study demonstrates that pollen types on the surface of aquatic habitats influence the oviposition site selection behaviour of gravid An. arabiensis and has carry-over effect on the developmental success of their offspring.