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Older than the dinosaurs

On a spring evening along the banks of the River Thames, thousands of mayflies can be seen engaging in what may be one of the world’s oldest dances. In the fading light, the males make a steep vertical climb, flip over and float back to Earth – wings and tail outstretched in a skydiving posture so as to drop slowly through the sky.

Mayflies are among the world’s oldest winged insects, emerging roughly 300m years ago – long before dinosaurs walked the Earth. Even the Mesopotamian poem the Epic of Gilgamesh, one of the oldest pieces of literature, makes reference to the short-lived mayfly. Over the epochs, the insect’s basic design has changed very little compared with the fossils of their ancestors.

“They have retained these odd characteristics and we can probably assume that they’ve been doing this [dance] for hundreds of millions of years, and yet we don’t really know why,” says Samuel Fabian, a research fellow at the University of Oxford who studies the aerial behaviours of insects.

Now, Fabian and his colleagues at Imperial College London think they finally have an answer. In new research published in the Journal of Experimental Biology, the scientists reconstructed the flight behaviour of the common mayfly, filming large swarms in the London borough of Richmond in 3D and analysing the insects’ flight paths.

In further simulations, the scientists found that male mayflies would stop their pursuit of any target that dropped beneath the horizon

“The problem is that the males have almost no filter,” Fabian says. “You can give them a beach ball – which, as far as I’m concerned, looks quite different from a female mayfly – and males will go right up to that much larger object and try to mate with it.”

Things get even trickier in low-light conditions, as females look almost identical to males even at close range. By staying below the females, males ensure their romantic energy is well spent. This is especially critical because mayflies do not have much time, only living from a few hours to a few days, during which they must pass on their genes.

Acing such reproductive goals is crucial to the species’ long-term survival. There are more than 3,000 mayfly species living in the world’s freshwater creeks, rivers, ponds and lakes. But many of Britain’s 51 species are now in a state of decline – another victim of what scientists call the “insect apocalypse”.

A 2019 global review estimated that 40% of the world’s insects were declining, while another study suggests more than 1 in 10 species could be lost by the end of the century.

From 2015 to 2021, the nonprofit conservation group WildFish carried out a riverfly census of Britain’s chalk streams. These streams are some of the cleanest waterways, fed by cool springs that flow from aquifers through chalk, a form of limestone. The species that live here are often very sensitive to pollution.

The census found that Britain’s chalk streams had lost 41% of their mayfly species on average compared with 1998. “In many lowland catchments, the spectacular hatches that once defined early summer have diminished dramatically, reflecting decades of mounting pressure on freshwater ecosystems,” says Janina Gray, head of science and policy at WildFish. “Pollution, sediment runoff, reduced river flows and rising water temperatures are all eroding the conditions these insects depend on.”

Other research suggests that even modest pollution in many English rivers may be enough to kill up to 80% of mayfly eggs, laid in riverbeds.

For now, Fabian encourages Britons to relish the ancient spectacle while they still can.

“This behaviour is something that pretty much everyone, at certain times of the year, should be able to see,” he says.

“These are quite urban places with lots of traffic, but they’re still hanging on and they’re still doing this dance that they have probably been doing since before Britain was separated from mainland Europe.”

The Guardian

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Do Vitamin C Serums Boost Sun Protection?

Sunscreen does two important jobs. It is largely used for its UVB protection benefits – blocking the rays that cause sunburn and are a major contributor to the development of skin cancer. But it also blocks UVA radiation, filtering out the rays that lead to signs of ageing.

Vitamin C does neither of these things, says Rosalind Simpson, a professor of dermatology at the University of Nottingham. That said, it is thought to help prevent sun damage in a different way.

“Antioxidants such as vitamin C have become a hot topic,” Simpson says. “People are really interested in whether they can improve skin appearance by neutralising free radicals created by UV exposure and pollution. Those free radicals contribute to the breakdown of collagen and loss of skin firmness.”

Whereas sunscreen acts as a kind of UV filter, antioxidants are thought to provide an additional line of defence. UVA exposure generates unstable free radicals in the skin, which can damage cells by disrupting their structures, and Vitamin C is believed to stop them doing this.

A 1996 study examined the effectiveness of antioxidants, including vitamins C and E, with and without sunscreen, in protecting against UV-induced skin damage. It found that vitamin C appeared to enhance protection against UVA-induced skin damage, but only when used alongside sunscreen. The researchers concluded that antioxidants may provide additional protection when combined with established sun-protection products.

“Nothing is a substitute for a good quality, broad-spectrum sunscreen with UVA and UVB protection and sensible habits when in the sunshine,” says Simpson.

That means wearing sunscreen, reapplying it regularly, and limiting direct sun exposure during the hottest parts of the day.

The Guardian

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Five-second rule is a myth

You drop a piece of cucumber on the floor. Do you immediately throw it in the bin or reassure yourself of the age-old “five-second rule” and reckon it’s fine to pop it in your mouth after a quick rinse?

If you fall into the latter camp, John Tregoning, professor of vaccine immunology at Imperial College London, has some bad news. He refers to three studies into bacteria transfer that all point towards the rule being false.

In the first, scientists looked at what happens when a range of foods (bread, buttered bread, watermelon and gummy bears) were dropped on a range of surfaces (tile, steel, wood, and carpet) that had been coated with bacteria. “They transferred almost immediately,” he says, adding that the worst combination for transfer happened when wet food hit a solid surface (watermelon on tile or steel).

Another study – where cooked sausage was dropped on to surfaces – showed that bacteria transferred on to the meat even if they had been applied to the surface hours earlier. It showed that “if you put a piece of contaminated chicken on to a work surface and then, two hours later, drop your piece of bread on to it, you can still pick up bacteria from it. It’ll be there for about 24 hours,” he says.

The final paper looked at the “five-second rule” for medical objects in the operating room. Perhaps unsurprisingly, it found that if surgeons drop something on the floor, they need to wash that instrument with detergent for it to be safe to use again.

What does all this mean for your fallen cucumber? “I think you have to accept it’s gone,” says Tregoning. Rinsing it with water won’t be enough to guarantee it’s clean. That’s especially the case if you’re particularly susceptible to infections, or if your dog might have walked something terrible through the house (even hours earlier).

THE GUARDIAN

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Saudi Arabia’s Tawakkalna app offers Hajj services in 19 languages

Saudi Arabia’s national digital platform Tawakkalna is providing Hajj-related government services in 19 languages for pilgrims and workers during the 1447H Hajj season, as part of wider efforts to improve the pilgrimage experience through advanced digital solutions.

The initiative comes within the efforts of the Saudi Data and Artificial Intelligence Authority to strengthen integration between government service entities during Hajj and support pilgrims throughout their journey, from arrival in the Kingdom and entry into Mecca and the holy sites to visits to the Prophet’s Mosque in Madinah and departure back to their home countries.

The app supports Arabic, English, Indonesian, Hindi, Urdu, Turkish, French, Bengali, Persian, Malay, Russian, Chinese, Filipino, German, Dutch, Japanese, Italian, Spanish and Portuguese.

Pilgrims can access a range of services through the platform, including Hajj permits linked to the unified digital Hajj permit platform “Tasreeh”, as well as permits related to entering Mecca, work authorisations, volunteer permits and vehicle permits issued by various government entities.

According to officials, Tawakkalna is designed to serve as a trusted digital companion for pilgrims by supporting daily movement and offering a smoother and safer digital experience during Hajj and visits to Madinah after the pilgrimage.

The app also allows users to book visits to Al Rawdah Al Sharifah through the Nusuk gateway service integrated into the platform.

Additional services available during Hajj include multilingual access to the Arafah sermon, an emergency assistance service called “Assefni”, live weather updates for the holy sites, Qibla direction, prayer times and digital Quran services.

Saudi authorities said the services are part of broader efforts aligned with the Pilgrim Experience Programme under Saudi Vision 2030, which prioritises improving services for pilgrims and Umrah performers through smart technology solutions.

The Tawakkalna platform currently offers more than 1,300 services in cooperation with over 350 government entities across sectors including health, education, justice, tourism and professional services, with more than 35 million users registered on the app.