The role of cuticular hydrocarbons in adaptations to changing climatic conditions and in sexual communication of Anopheles mosquitoes

Malaria is a vector-borne disease that currently threatens half of the world population. Anopheles mosquitoes transmit malaria, and many tools have been developed to prevent mosquito bites, such as mosquito repellents and insecticide-treated bed nets. Despite the huge reductions in malaria since the millennium, present control methods have stalled, partly due to emerging insecticide resistance in malaria mosquito vectors. In addition, mosquitoes invade new regions of the world, thus increasing the risk of malaria to people. Better understanding of mosquito biology and ecology could lead to the development of novel methods of mosquito vector control.

Here we will focus on two species/species complexes of Anopheles mosquitoes, and will study how a class of chemical compounds that is found on their bodies helps mosquitoes to recognize mating partners and to colonize new areas. These compounds are cuticular hydrocarbons, and they form a waxy layer on the mosquito cuticle – their analogue of skin. In other insects, cuticular hydrocarbons are known to have two roles. They prevent water loss – desiccation, which is likely to occur in hot tropical environments where mosquitoes live. They are also used as an attractive perfume for recognizing appropriate mating partners. However, the role of cuticular hydrocarbons in malaria mosquitoes is not well known, and this project sets out to test it.
We will focus on the two Anopheles species that we selected because of the special interest that they present.

The first species, Anopheles stephensi, are native to India, but have in the past 10 years invaded the Horn of Africa. Upon migration from India, these mosquitoes had to adapt to and survive in dry and hot climate of the Arabian peninsula and East Africa. Thus, any adaptations to different environmental conditions must also be extremely recent and are happening very rapidly. We have a chance now to study this unique biological process as it occurs, and we predict that changes in cuticular hydrocarbons help these mosquitoes in their invasion of Africa. In addition, An. stephensi also have to distinguish their potential mating partners from the native African Anopheles species. This means that their attractive perfumes, if they use them at all, might have been modified – this again brings us to study cuticular hydrocarbons.

The second species of interest, Anopheles farauti, inhabits northern Australia, Papua New Guinea, the Solomon islands and Vanuatu. In fact, this is not one species but a complex of 8 closely related species, some of which occur at the same locations, and some live on islands in isolation from their relatives. We so far have studied 1 of the 8 species that inhabits Northern Australia. We found that cuticular hydrocarbons of the males and females of this species are very different. This exciting finding implies that they may indeed use cuticular hydrocarbons as the perfume to select their mates as it has been shown in many other insect species. We now want to extend our study to the other sibling species, and see whether their cuticular hydrocarbons are different between males and females. We predict that they are, but are modified slightly when the relatives of the mosquitoes live at the same location.

The finding that An. farauti and/or An. stephensi use chemical compounds to find their mates will have profound implications for other mosquito species and mosquito control strategies. Mosquito genes and proteins, responsible for production and perception of cuticular hydrocarbons, may then be targeted in a variety of ways, leading to novel methods of malaria vector control that we urgently need. In addition, if we find evidence that rapidly changing cuticular hydrocarbons helps mosquitoes adapt to changing climate, this will help the scientists predict how mosquito populations may migrate and invade around the world in the future. This may guide prevention strategies that will save millions of human lives.

UKRI grant link

Climate Change
Measurement of Transmission

Jul 2021 — Jul 2023

$115,000

Ethiopia

Anopheles stephensi