Evolution

Mosquito love songs provide clues about immunity

A new study investigates how a mating cue called “harmonic convergence” might affect immunity in offspring

August 26, 2021
The Scitech
 

When choosing a mate, a female will use a male’s ability to beat his wings at the same frequency as her own as a cue for a male’s fitness and desirability.

A new Cornell study of Aedes aegypti mosquitoes investigates how a mating cue called “harmonic convergence” might affect immunity against parasites, bacteria and dengue virus in offspring, which has important implications for trade-offs male mosquitoes make between investing energy towards immunity or investing it on traits that impact mating and fitness. “We decided to look to see if the cues that a female responds to might correlate with the downstream genes that a male passes on to offspring that could protect them against parasites and pathogens,” said Courtney Murdock, associate professor in the Department of Entomology in the College of Agriculture and Life Sciences. The study was published in Nature Communications Biology.

In their study, the researchers separated harmonically converging pairs and non-converging pairs of Aedes aegypti, which transmit dengue, yellow fever, chikungunya and Zika viruses. Males and females of each group were housed together for up to four days. Though females avoid mating with non-converging males in the wild, the males will harass the female into mating under these conditions. They tested humoral melanization, a defence response where insects will coat a pathogen or parasite with melanin in its gut in order to wall it off and prevent infection. They did this by injecting a tiny bead into the mosquitoes’ midsection, and then removing the bead and assessing whether the bead was uncoated, partially coated or fully coated. They also injected mosquitoes with fluorescently labelled Escherichia coli bacteria and tested how well they grew after 24 hours. And they exposed the females (as males don’t feed on blood) to dengue virus and looked for its presence in tissues, especially saliva glands, from where the virus is transmitted during a blood meal. Overall, males were less capable of melanizing beads and resisting bacterial infections than females. Additionally, male offspring from converging parents were significantly less able to melanize compared with nonconverging male offspring. At the same time, these males fended off bacterial infection better than their nonconverging peers at rates similar to females when they were young, but their defences dropped rapidly as they aged. With regard to dengue, females from converging parents showed higher immunity early in life, which waned and matched offspring from nonconverging parents as they aged. But overall, the presence of virus found in saliva was so low that the researchers concluded more study is needed.

Source: Cornell University news release