You may have missed… antimicrobial CBD coating; a spider that walks like an ant; detecting myrtle rust; and screwdriver teeth fossils

This spider looks like a plant and walks like an ant

A species of tiny, colourful jumping spider, Siler collingwoodi, uses a combination of camouflage and movement mimicry to help evade other spiders which eat them – according to a new study in iSciences.

Researchers collected wild spiders from four geographic locations in southern Hainan, China, to compare to another type of jumping spider that doesn’t mimic ants, as well as five co-occurring ant species. They found that S. collingwoodi move like ants by raising their front legs to mimic antennae, bobbing their abdomens, and lifting their legs to walk in an ant-like manner. 

S. collingwoodi is not necessarily a perfect mimic, because its gait and trajectory showed high similarity with multiple ant species,” says first author Hua Zeng, an ecologist at Peking University, China. 

“Being a general mimic rather than perfectly mimicking one ant species could benefit the spiders by allowing them to expand their range if the ant models occupy different habitats.”

A small colourful spider on a pink flower
Siler collingwoodi. Credit: Yuchang Chen

They then explored the behaviour of two predators – a predatory spider and praying mantis – in experiments where they were given the choice of attacking an ant-mimicking spider or the other jumping spider.

“We initially thought that both predators would behave similarly in the antipredation experiments, but in fact the simulated ant locomotion of S. collingwoodi only worked for the jumping spider predator, while the praying mantis showed indiscriminate attacks on both ants and mimics,” says senior author Wei Zhang, an evolutionary ecologist at Peking University.

This difference might be driven by the fact that praying mantises are much larger than their prey, so they can get away with eating spiny, bitey ants without risking grave injury, but this is not the case for the predatory spiders.

Bizarre “screwdriver teeth” fossils found in Morocco

Scientists have discovered a new species of mosasaur – Stelladens mysteriosus – a sea-dwelling lizard that died out with the dinosaurs. According to a new study in the journal Fossils, they unearthed the strange, ridged teeth (unlike those of any known reptile) in Morocco.

The new species comes from the Late Cretaceous, was about twice the size of a dolphin, and had blade-like ridges running down its teeth arranged in a star-shaped pattern – reminiscent of a Phillips-head screwdriver.

The teeth were small, but not very long and had wear on the tips, which seems to rule out soft-bodied prey. The also weren’t strong enough to crush heavily armoured animals like clams or sea urchins.

Brown teeth with ridges from tip to base
Most mosasaurs had two bladelike, serrated ridges on the front and back of the tooth to help cut prey, however Stelladens had anywhere from four to six of these blades running down the tooth. Credit: Dr Nick Longrich

“That might seem to suggest it’s eating something small, and lightly armoured – thin-shelled ammonites, crustaceans, or bony fish – but it’s hard to know,” says Dr Nick Longrich from the Milner Centre for Evolution at the University of Bath, UK, who led the study. 

“There were weird animals living in the Cretaceous – ammonites, belemnites, baculites – that no longer exist. It’s possible this mosasaur ate something, and occupied a niche, that simply doesn’t exist anymore, and that might explain why nothing like this is ever seen again.

“Evolution isn’t always predictable. Sometimes it goes off in a unique direction, and something evolves that’s never been seen before, and then it never evolves again.”

Edible CBD coating could extend the shelf life of strawberries

Mouldy strawberries in plastic packets might at last be a thing of the past. To increase strawberries’ shelf life, scientists have incorporated cannabidiol – a non-hallucinogenic compound from cannabis known as CBD – and sodium alginate into an edible antimicrobial coating.

The researchers encapsulated CBD in a biodegradable polymer used in drug to produce nanoparticles, and mixed them with sodium alginate in water.  Strawberries were then submerged into solutions containing different amounts of nanoparticles before a second dip into a mixture of ascorbic acid and calcium chloride to turn the colourless coating into a gel.

Two photos of a strawberry, left looks fresh and right looks mushy
A strawberry enveloped in an edible CBD coating (left) still appeared fresh compared to an untreated berry (right) after 15 days. Credits: Adapted from ACS Applied Materials & Interfaces 2023, DOI: 10.1021/acsami.3c04036

After 15 days, CBD-treated samples ripened and decayed much more slowly than untreated ones, possibly because of reduced microbial growth. The research has been published in ACS Applied Materials & Interfaces.

Myrtle rust can now be detected before it’s visible

New Zealand researchers have found a way to quickly detect the deadly plant disease myrtle rust days before plants show signs of infection.

Caused by the fungal pathogen Austropuccinia psidii, myrtle rust is a major problem in Australia because it affects plants in the family Myrtaceae – which includes eucalypts, paperbarks, tea trees, and lily pillies.

Researchers innoculated rose apple leaves and used thermal imaging to detect decreases in leaf temperature in infected plants at least a day before symptoms could be seen. They also used a hyperspectral sensor to look at changes in the wavelength of light reflected from infected leaves and found the ratio of blue/green light reflected by infected leaves was noticeably different from healthy leaves up to three days before symptoms were visible. 

Two men in lab coats study a plant with sensors
Geospatial technician David Cajes and scientist Dilshan de Silva scanning for myrtle rust. Credit: Scion

“We are several years away yet, but we can see a time when nurseries will be using hand-held, mobile technology that will be able to detect myrtle rust infections before they are visible,” says Heidi Dungey, geneticist at Crown Research Institute Scion in New Zealand.

And because the equipment used can be mounted on drones, the team hopes to one day develop field-based methods to detect myrtle rust infections rapidly and remotely.

The results have been published in the journal Phytopathology.

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