Oviposition site selection behaviour of female Anopheles arabiensis

Abstract

Mosquitoes of the Anopheles gambiae sensu lato complex consist of nine morphologically indistinguishable species. Some females of the species transmit Plasmodium and preferentially lay eggs in aquatic habitats with different biophysical compositions. These biophysical compositions likely influence their oviposition site selection behaviour. However, little is known about the influence of these biophysical factors on the oviposition site selection behaviour of gravid An. arabiensis. Black basins were planted in two compartments of a semi-field; water was added and used as aquatic habitats. Dragonfly nymphs, backswimmer nymphs, adult diving beetles, maize and rice pollens, and intraspecific and interspecific mosquito larvae were randomly inoculated into each habitat. Wild-caught gravid Anopheles arabiensis were released into each compartment to lay eggs. In some objectives, eggs were counted and returned to the habitats, and the resultant larvae were counted until pupation. In one objective, no external organism was added in small (30 cm diameter, 20 l) and large (60 cm diameter, 40 l) basins, while in another, only small habitats were used and inoculated with intraspecific and interspecific 1st larval instars and left for 72 hrs. Subsequently, gravid An. arabiensis were released, and the resultant 3rd larval instars were preserved for molecular analyses. Gravid An. arabiensis preferred habitats with rice pollen, smaller habitat sizes, and those without predators and competitors. Larvae significantly developed into 4th instar and pupae in habitats with maize pollen and those without predators and larval competitors compared to their comparators. Skip-oviposition was higher across smaller than larger habitats, those without larval competitors, followed by conspecific larvae. Habitat size, macroinvertebrate predators, larval competitors, and rice and maize pollens in larval habitats are important biophysical factors influencing oviposition site selection behaviour in female An. arabiensis and hence can be harnessed for larval control against malaria.