Losing Their Bite

Scientists have discovered which genes are associated with biting and non-biting in the pitcher plant mosquito.

Bradshaw-Holzapfel Lab, University of Oregon

The spread of such devastating diseases as malaria, dengue, Zika, and West Nile relies on mosquitos that transmit these pathogens when taking a blood meal from a potential host. No biting, no transmission. Traditional preventative efforts have focused on eradication of mosquitos—and/or their breeding sites—and deterrence, with physical or chemical barriers. A third route to disease control—genetically altering mosquitos so they do not bite—is a potential option, following a new study of Wyeomyia smithii, a mosquito species generally found along the east coast and parts of the interior of Canada and the United States.

Though some mosquito species are non-biting nectar feeders, W. smithii is the only species known to have some populations that bite and other populations that have evolved to feed on nectar. Entomologist David Denlinger of Ohio State University and an international team of scientists compared these different W. smithii populations to determine whether their genetics differed along with their lifestyles.

The team compared the genes of biting W. smithii from Florida to non-biting W. smithii from Maine. In addition, strains of non-biting and biting W. smithii derived from a mixed Florida population were identified in the lab and compared. In both cases, the team found that biting mosquitoes had genes related to much higher metabolic costs than non-biters—genes associated with their ability to benefit from a blood meal. Biters also had more genes associated with detecting hosts, while non-biters had more genes associated with vision. “This was a bit of surprise,” says Denlinger, adding that visual acuity might be more important when looking for plants.

Pinpointing these genetic differences is key to understanding what causes the evolutionary transition from biting to non-biting mosquitos. “If nature already has a situation where mosquitos have lost their ability to take a blood meal,” says Denlinger, “it should also be possible for us to someday switch off their blood-feeding drive.” (Proceedings of the National Academy of Sciences)