Genetically Modified Mosquitos Could Eradicate Wild Populations By Only Producing Male Offspring

by Lisa Winter

Over 200 million people are infected by malaria each year, and the majority of the 627,000 deaths per year are children younger than five. The disease is carried by mosquitos who act as vectors for the parasite. It’s only transmitted to humans by female mosquitoes, as they’re the only ones who bite. A team of researchers led by Andrea Crisanti of the Imperial College London managed to genetically modify mosquitos to produce 95% male offspring, eliminating mosquito populations along with the risk of malaria. The results of the study were published in Nature Communications.

In most species of mosquito, the females need a blood meal in order to acquire the nutrients to create viable eggs. When she does, she can lay about 200 eggs at a time in water, and up to 3,000 eggs over the course of her lifetime. About half of those offspring will be daughters, many of whom will live long enough to produce that amount of offspring also. For humans living near mosquitos carrying the parasite that causes malaria, those numbers of female mosquitos present a very real threat.

But what if the numbers could be skewed so that the sex ratio favors males, who are harmless to humans? This is exactly what Crisanti’s team set out to do with Anopheles gambiae, a species of mosquito endemic to sub-Saharan Africa, where 95% of malaria deaths occur. The researchers modified the males with the enzyme I-Ppol, which excises the X chromosome during spermatogenesis. This renders sperm that would produce daughters to be non-functional, while the sperm that will create male offspring are unaffected. As a result, about 95% of the resulting offspring are male.

Next, modified males were introduced to five caged wild-type populations. As the males mated with the females, they passed along the same mutation until it dominated the population. For four of the five populations, it took only six generations for the mosquitos to die out due to a lack of females.

“What is most promising about our results is that they are self-sustaining,” co-author Nikolai Windbichler said in a press release. “Once modified mosquitoes are introduced, males will start to produce mainly sons, and their sons will do the same, so essentially the mosquitoes carry out the work for us.”

This study was the first to successfully manipulate mosquito sex ratios, and it was done in a big way. The researchers hope that this information will be used to develop genetic mutations to be used in the wild, bringing large populations of mosquitos to their knees.

“The research is still in its early days, but I am really hopeful that this new approach could ultimately lead to a cheap and effective way to eliminate malaria from entire regions,” added lead author Roberto Galizi. “Our goal is to enable people to live freely without the threat of this deadly disease.”

Of course, while eradicating the mosquitos would be fantastic for eliminating the threat of malaria, what other affects would it have? Wouldn’t there be harsh consequences for the ecosystem? After all, mosquitos have been on the planet for about 100 million years and represent 3,500 species. As it turns out, mosquitos wouldn’t really be missed if they were to disappear ( While mosquitos can act as pollinators as well as a food source for other animals, their absence would be merely a temporary setback before another species filled the niche. Of course, there is a gamble in assuming the replacement organism would be harmless.

“Malaria is debilitating and often fatal and we need to find new ways of tackling it. We think our innovative approach is a huge step forward. For the very first time, we have been able to inhibit the production of female offspring in the laboratory and this provides a new means to eliminate the disease,” Crisanti explained.

Each year, sub-Saharan Africa loses about $12 billion in economic productivity due to malarial infections. Considering developed areas in these countries have per capita incomes of about US$1500, this would have very real implications for the quality of life for people in those areas. Eliminating that disease would also allow doctors and hospitals to address other health concerns, and the environment would likely benefit from not having to use insecticides.

Termite Genome Reveals Details of “Caste System”

The genome of the termite has just been sequenced, and it is revealing several clues about how the pests create their rigid social order.

For instance, the new genome, detailed today (May 20) in the journal Nature Communications, uncovers some of the underpinnings of termites’ caste system, as well as the roots of the males’ sexual staying power.

Like other social insects— such as ants, honeybees and some wasps — termites live in highly structured “caste systems,” with each creature programmed to perform a rigidly defined job. A select few termite kings and queens reproduce, while drones and soldiers work, defend the colony or care for young.

Yet termites evolved their social structure independently from ants and bees, which belong to an order known as Hymenoptera.

To understand how this happened, Jürgen Liebig, a behavioral biologist at Arizona State University, and his colleagues collected dampwood termites(Zootermopsis nevadensis nuttingi) that lived in Monterey, California. The researchers then sequenced the genome of the insects and measured how those genes were expressed, or turned on and off.

The research revealed several insights about termite sexual and social behavior.

Termite society is roughly half males and half females. Termites have sexually active kings as well as queens, and kings make sperm throughout their lifetimes. Dampwood termite males also have testes that shrivel and grow seasonally.

Ants and honeybees, in contrast, live in predominantly female societies, and ant sex is a one-time affair.

“Their societies generally consist of females — the males are only there to fly out, mate and die,” Liebig told Live Science.

Sure enough, the termites had more gene variants associated with sperm production and degradation, and those genes were expressed to a greater extent than in ants, Liebig said. That finding suggested those genetic differences contributed to male termites’ sexual longevity.

The termite genome also contains a high fraction of genes that are turned off by chemical tags, or methyl groups, the researchers found. In honeybees, this process of methylation sets the fate of individual animals, determining their place in the caste system. The new findings suggest a similar process may be at play in termites.

In addition, both ants and termites communicate via chemical smell signals sensed by receptors on their antennas.

But while ants venture out for food, these particular termites spend their whole lives dining on one piece of wood.

The new analysis revealed that the termites have far fewer cell types for recognizing individual chemicals, probably because they rarely face off against foreign termites or search for food. They simply don’t need to recognize as many smells, Liebig said.

However, some termite species, such as Australian mound-building termites, do forage and encounter foreigners along the way, so as a follow-up, the team would like to see if those termites can detect a greater array of chemicals, Liebig said.

Lab rats given a 6th sense through a brain-machine interface


Duke University researchers have effectively given laboratory rats a “sixth sense” using an implant in their brains.

An experimental device allowed the rats to “touch” infrared light – which is normally invisible to them.

The team at Duke University fitted the rats with an infrared detector wired up to microscopic electrodes that were implanted in the part of their brains that processes tactile information.

The results of the study were published in Nature Communications journal.

The researchers say that, in theory at least, a human with a damaged visual cortex might be able to regain sight through a device implanted in another part of the brain.

Lead author Miguel Nicolelis said this was the first time a brain-machine interface has augmented a sense in adult animals.

The experiment also shows that a new sensory input can be interpreted by a region of the brain that normally does something else (without having to “hijack” the function of that brain region).

“We could create devices sensitive to any physical energy,” said Prof Nicolelis, from the Duke University Medical Center in Durham, North Carolina.

“It could be magnetic fields, radio waves, or ultrasound. We chose infrared initially because it didn’t interfere with our electrophysiological recordings.”

His colleague Eric Thomson commented: “The philosophy of the field of brain-machine interfaces has until now been to attempt to restore a motor function lost to lesion or damage of the central nervous system.

“This is the first paper in which a neuroprosthetic device was used to augment function – literally enabling a normal animal to acquire a sixth sense.”
In their experiments, the researchers used a test chamber with three light sources that could be switched on randomly.

They taught the rats to choose the active light source by poking their noses into a port to receive a sip of water as a reward. They then implanted the microelectrodes, each about a tenth the diameter of a human hair, into the animals’ brains. These electrodes were attached to the infrared detectors.

The scientists then returned the animals to the test chamber. At first, the rats scratched at their faces, indicating that they were interpreting the lights as touch. But after a month the animals learned to associate the signal in their brains with the infrared source.

They began to search actively for the signal, eventually achieving perfect scores in tracking and identifying the correct location of the invisible light source.

One key finding was that enlisting the touch cortex to detect infrared light did not reduce its ability to process touch signals.

Thanks to Kebmodee for bringing this to the attention of the It’s Interesting community.