You may have missed… potential new gel contraceptive; major fire risk increase as air gets thirstier; ant ‘milk’; and rainbow film tells sugars apart.

Pupae ‘milkshakes’ bring all the ants to the yard

US entomologists have discovered that immature ant pupae produce a milk-like substance that other ants consume, according to a new study in Nature. The fluid contains hormones and psychoactive substances, so may influence the behaviour and physiology of colony members.

Ant eggs first hatch into worm-shaped larvae that have no eyes or legs and rely on adult ants to provide food. Then, once the larva is large enough, it metamorphoses into a pupa, during which some species spin a cocoon for protection while others remain uncovered. In the final stage the pupa emerges as an adult.

Before now, scientists presumed that pupae don’t interact with the colony, but new research shows that pupae secrete large amounts of a nutrient-rich substance just before hatching. This substance is either consumed directly by adult ants or by the developing larvae, which are placed on the pupae by the adults.

Scientists found that larvae that cannot access the secretion exhibit stunted growth and poor survival, while pupae left to sit in their own secretions develop fungal infections and die. This behaviour was previously unobserved because scientists focused on ant colonies, rather than individuals, and in a colony the secretions never accumulate because its consumed so quickly.

A potential new way to prevent pregnancy

Scientists have designed a non-hormonal gel that reinforces the cervical mucus barrier, offering a potential alternative to spermicides and contraceptive pills.

According to a new study in the journal Science Translational Medicine, tests on ovulating female sheep resulted in a 98 percent average decrease in uterine sperm numbers, compared with the untreated control animals. For comparison, contraceptive pills are between 91-99% effective.

Rather than killing sperm as spermicides do, the gel blocks sperm from entering the uterus by reinforcing the cervical mucus’ natural capacity as a barrier that isolated the vagina from the uterus and upper reproductive tract.

The researchers crosslinked molecules of mucin – the proteins that give mucus its lubricating property – with chitosan, a fibrous substance used in medical materials such as hydrogels, meshes, and sutures, to temporarily thicken the cervical mucous.

Lab experiments using human cervical mucous and sperm shows a reduction in sperm penetration after one minute and full sperm blockage after five minutes.

“Vaginal gels like this can be applied in seconds,” says senior author Thomas Crouzier, a biopolymers researcher at KTH Royal Institute of Technology, Sweden.

 “We imagine that a product like this should be usable from seconds to a few hours before sexual intercourse. The effect could last for hours but diminish over time as the mucus barrier is replaced naturally.”

Major fires are an increasing risk as the air gets thirstier

Greater water demand in the atmosphere means an increase in forest fire risk for at least an extra 30 days per year, new Australian research has found.

Researchers examined a global climate dataset and satellite records of fire activity in all of the world’s forests over the last 20 years and found that there is a strong link between fire activity and vapour pressure deficit (VPD) – a measure of the atmosphere’s “thirst.”

VPD describes the difference between how much moisture is in the air and how much moisture the air can hold when it’s saturated. The bigger the difference, the greater the air’s drying power.

The results show that forest fire is much more likely above a certain threshold in VPD and this differs between forest types – lower in boreal and temperate forests, and higher in Mediterranean, subtropical and tropical forests.

Importantly, warmer air can hold more water, which means that VPD increases – and fuels will dry out more often – with rising temperatures due to climate change.

“Without strong climate action, there will be many more days each year – at least 30 – when Earth’s forests cross over into this critical flammability zone. This means we’re likely to see more major fires, with all the risks that come with them,” says lead researcher Dr Hamish Clarke from the University of Melbourne FLARE Wildfire Research group.

The study has been published in Nature Communications.

A rainbow film for telling sugars apart

Chinese chemists have created a film that, when stretched evenly with a simple apparatus, can tell different sweeteners apart. The material works by enhancing the unique shifts in fluorescence intensity of 14 sugars tagged with a fluorescent dye, distinguishing between them in beverages and sweat samples.

The film was made by embedding closely packed, ordered rows of polystyrene nanospheres into a stretchable film of polyethyl acrylate. The resulting gummy material initially looks red, but, when stretched with a uniform force, its colour shifts through the rainbow – from red to pink, orange, yellow-green, light green, and finally to dark green.

The researchers mixed six commercially available drinks with fluorescent dyes, creating fluorescent complexes. By dotting them onto the film, which was then stretched, the fluorescence intensities were measured at two different wavelengths of light.

Because each sample’s sugar-dye complexes produced unique signals, they could be distinguished from each other.

Based on these results, the researchers say that the material could be incorporated into wearable devices for environmental, clinical or health monitoring of sugar, or modified to detect other substances. 

The research has been published in ACS Nano.