Mosquitoes bite more often during droughts to stay hydrated

When the rain pours after a long, harsh drought, there is often a sudden influx of mosquitoes buzzing around and seemingly appearing out of nowhere.

Despite grueling dry spells that last for weeks, mosquitoes manage to survive and bounce back quickly once the rain arrives. But how do these tiny creatures manage to make such a rapid comeback?

In a recent study, scientists at the University of Cincinnati have unraveled some fascinating answers to this puzzling phenomenon.

Mosquitoes bite for recovery

Mosquitoes are hardy insects – some of which are infamous for spreading diseases like malaria to humans.

While you might imagine that the mosquito population would dwindle during a drought as water sources dry up, the reality is quite the opposite.

Mosquitoes have a unique survival strategy that entails quenching their thirst with blood. They bite more frequently to keep up their hydration levels.

“We’re finding that mosquitoes bite people more than we imagined, unfortunately,” said Christopher Holmes, the study’s lead author.

Climate change only adds to the challenge, as milder winters are advantageous to mosquito populations, noted Holmes.

Hungry for more: The mosquito’s lifeline

Typically, female mosquitoes feed on a blood meal to produce eggs. Within four days of a blood feast, they lay their eggs and seek another blood target to repeat the cycle. However, when faced with a drought, they tweak this cycle.

Instead of waiting to lay their eggs after a blood meal, drought-prompted mosquitoes feed more frequently to stay hydrated. This, in turn, increases the likelihood of spreading diseases like dengue, Zika, or malaria. It is a fascinating yet worrisome survival technique.

According to the researchers, people have assumed drought reduces mosquito populations and the spread of diseases. However, their study finds otherwise.

Survival of the fittest

To investigate how mosquitoes survive during droughts, the team studied genetically-altered individuals in which certain senses, such as the detection of carbon dioxide, were impaired. Mosquitoes use the presence of carbon dioxide to detect their prey.

The researchers made an interesting observation. If mosquitoes couldn’t sense carbon dioxide, they couldn’t locate a host to bite and consequently succumbed to the dry spell.

Furthermore, UC doctoral student Souvik Chakraborty pointed out a remarkable survival trait in mosquito eggs.

“The Aedes aegypti mosquito is resistant to drying out. Its eggs can survive, sometimes for as long as a year,” said Chakraborty, adding that the mosquito eggs hatch instantly when touched by rainwater.

The researchers also found that some mosquito species can tolerate cold temperatures. They engorge themselves on nectar before winter, store huge lipid deposits, and lay eggs as soon as it gets warm.

Ancient survivors with a deadly bite

The oldest known mosquitoes date back to the early Cretaceous period, about 125 million years ago.

Over this impressively long period, the mosquito’s survival mechanisms have evolved to ensure its continued existence in the food chain – where it is food for a range of creatures including fish, birds and bats.

However, their survival comes at a cost to humans. Each year, diseases spread by mosquitoes claim more than 700,000 lives.

According to Benoit, understanding the biology of mosquitoes is crucial in comprehending their survival and reproduction mechanics.

As we progress in understanding the resilience of these insects, we move closer to taming the significant health challenges they present.

Mitigating the mosquito threat

The University of Cincinnati research emphasizes the need to act on mosquito-borne diseases in a changing climate.

As mosquitoes adapt to harsher conditions and expand their territories due to milder winters, public health strategies must evolve in tandem.

New methods of mosquito control, such as eco-friendly repellents or genetic interventions, could reduce their population and disease transmission rates.

Moreover, advanced surveillance systems that predict mosquito outbreaks based on climate patterns can empower communities to take preventive measures before the diseases spread.

With continued research, scientists hope to come up with innovative solutions to protect human health while gaining a better understanding of how these durable insects remain so resilient.

The full study was published in the journal iScience.

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