Scientists reveal how boa constrictors breathe while squeezing the life out of their prey
Scientists reveal how boa constrictors breathe while squeezing the life out of their prey
Boa constrictors, snakes that coil around prey and squeeze it to death before swallowing it whole, prevent suffocating themselves during the process by adjusting the sections of the ribcage they use to breathe, a new study has found.
Unlike humans who have diaphragm muscles beneath the rib cage, the snakes rely entirely on the fine control they have on different sections of their rib cage when constricting prey and digesting dinner, noted the study, published on Thursday in the Journal of Experimental Biology.
When the snakes are fully squeezing prey to death and the ribs can no longer move, the hind section of the lung pulls air into it, working like bellows, say the scientists, including those from Brown University in the US.
Researchers attached tiny metal markers to two ribs in each reptile – one a third of the way down the snake’s body and another halfway along – to visualise how the ribs moved using X-rays.
A blood pressure cuff was placed over the ribs in both regions, and the pressure was gradually increased to immobilise the snakes.
“Either the animals did not mind the cuff or became defensive and hissed to try to get the researcher to leave... This was an opportunity to measure some of the biggest breaths snakes take,” study co-author John Capano said, adding that the reptiles filled their lungs in when hissing.
Reconstructing the rib movements of the snakes, scientists found that boa constrictors could control the movements of ribs in different portions of the rib cage independently.
When the snakes were gripped by the blood pressure cuff a third of the way along the body, they breathed using the ribs further back, swinging the ribs backward while tipping them up to draw air into the lungs.
However, when the ribs toward the rear of the lung were constricted, the snakes breathed using the ribs closer to the head.
Scientists said the ribs at the far end of the lung only moved when the forward ribs were gripped, drawing air deep into the region, even though it has a poor blood supply and does not provide the body with oxygen.
Based on the analysis, researchers said the far end of the lung was behaving like bellows, pulling air through the front section of the lung when it could no longer breathe for itself.
Scientists also filmed and recorded nerve signals controlling the rib muscles when constricted by the blood pressure cuff, which revealed that the ribs were not simply being held immobile.
In the sections of the snake constricted by the cuff, researchers could not find any nerve signals, suggesting the snakes had shifted to breathing by activating a different set of ribs further along the body.
Since subduing and digesting prey is one of the most energy-intensive activities for boas, scientists said it was likely essential that they evolved the ability to adjust where they breathe before adopting this lifestyle.
“It would have been difficult for snakes to evolve those behaviours without the ability to breathe,” Dr Capano said.
“This study provides a new perspective on snake evolution and suggests that modular lung ventilation evolved during or prior to constriction and large prey ingestion, facilitating snakes’ remarkable radiation (species diversity) relative to other elongate vertebrates,” scientists wrote.
Mass migration: the reason birds are flocking to cities
Mass migration: the reason birds are flocking to cities
The concept of the migratory bird is nothing new. We learn early on that birds fly south for the winter in search of shelter and food.
Some species of migrating birds are increasingly attracted to life in the big city – but these unnatural environments can be deadly.
Ana Morales stepped through the shrubbery, scanning the airwaves with a radio receiver. The device had picked up a signal from a transmitter that she and colleagues had previously attached to a Swainson's thrush, a small brown and white speckled bird native to the Americas. The same signal had popped up on Morales' handheld receiver a few days earlier, emanating from exactly the same bush in a park on the edge of Montreal in Canada.
This was a worry. It seemed so unlikely that the transmitter remained attached to a live bird – more likely, it had fallen off and was hanging on a branch. Just to make sure, Morales, a graduate student at McGill University, gave the berry-laden shrub a gentle shake – and then a flutter of feathers among the branches and shadows caught her eye. To her surprise, the thrush, very much alive and healthy, was hopping about the bush in protest at having been disturbed. This little bird had hung around for longer than she expected.
Swainson's thrushes migrate from northern areas to Central and northern South America every autumn. But some make a "pit stop" in and around cities such as Montreal. For a study published last month, Morales and her colleagues had been researching how Swainson's thrushes balance the need to migrate quickly – so as to maximise its benefits – with the need to refuel, such as by stopping over in places like Montreal. They caught and radio tagged a total of nearly 80 of the birds.
Around a million redwings migrate to the UK every year (Credit: Getty Images)
Huge numbers of migrating birds visit cities all around the world on their extraordinary journeys, which often cover thousands of kilometres. It is not always obvious why they come to urban locations. Some appear to be attracted by light. Others, such as the Swainson's thrush in its bush full of berries, seem to enjoy the food on offer. But cities are not always friendly to outsiders.
The death toll, sadly, is staggering. Some migrating birds, for example, are killed by domestic cats while others collide with buildings. Many thousands of birds die every year in New York alone when they crash into the brightly lit windows of skyscrapers, a well-known problem in megacities (Read more from BBC Future about why this happens). More recently, a flock of blackbirds was filmed dropping from the sky onto a street in the city of Chihuahua in north-west Mexico, leaving many dead.
And yet, scientists are discovering that towns, while dangerous, can sometimes help to support migrating species. So how do we ensure that cities act more as travel lodges – and not death traps – for these species?
During their study, Morales and her colleagues found that Swainson's thrushes make surprisingly long stopovers in Montreal, where many of the birds moult – a process through which the birds shed and regrow some of their feathers. That helps to prepare them for the long migration. It's like putting a new set of tyres on your car.
"It's pretty amazing that this small green area can support a bird for 40 days," says Morales, marvelling at how contented the thrushes seemed. The birds might move to this urban green space precisely because it is rich in resources such as berries and water.
Any bird landing in a city park could find such rewards, if they are present, but what draws birds to a bustling metropolis in the first place? It could largely be to do with light, says Morales' co-author Barbara Frei at Environment and Climate Change Canada, a department of the Canadian government.
No one knows exactly why birds are attracted to artificial light at night but there is ample evidence for this effect. One possibility, Frei says, is that birds – which use starlight and other phenomena to navigate – are naturally enticed by points of light.
More than 100 years ago, the Irish anatomist and ornithologist Charles Patten was stationed at a lighthouse off the coast of Ireland where he observed this phenomenon first-hand. According to his reports, mind-boggling swarms of migrating birds would fly towards the lighthouse and, unfortunately for them, crash into its windows. Many of these birds died, which allowed Patten to collect and study them. But back then, sources of very bright, artificial light were uncommon whereas today, electric light is visible practically everywhere at night.
The yellow-rumped warbler mostly migrates at night, travelling around 312 km per day (194 miles per day) in the spring (Credit: Getty Images)
Many millions, possibly even billions, of migrating birds die as a result of this every year. The tallest, brightest buildings situated along known migratory flight paths are likely the most deadly. Research suggests the huge McCormick Place convention centre in Chicago, for instance, caused up to 11,567 bird deaths between 2000 and 2020.
"A lot of the light isn't really necessary," says Frank La Sorte, at Cornell University, when referring to urban lighting in general. "It's excessive."
Switching more lights off at night when birds are migrating could save thousands of avian lives, he says. A study published last year estimated that by turning out half of the lights in McCormack Place in the spring and autumn, bird mortality could be reduced by nearly 60%.
The pull that urban light has on migrating birds is unlikely to be exclusive to large cities. Simon Gillings at the British Trust for Ornithology lives in Cambridge in the UK, a city with a population of just 130,000. The tallest building, Cambridge University's library tower, stands at less than 50m (164ft). "It's hardly Manhattan," he admits.
The more interesting concept is the migration of certain birds to cities. What do they want in urban areas, and how can we help them survive?
Gillings wanted to find out whether even a small city like this would act as a significant light-emitting beacon, attracting migrating birds at night. He and several volunteers placed audio recorders in their gardens during the autumn of 2019 and together recorded many thousands of hours of night-time audio.
"Anybody that starts doing that suddenly realises there's this huge wealth of birds moving around," says Gillings, marvelling at the range of bird calls captured by the recordings.
To comb through the data, he used an artificial intelligence system that automatically counted the number of calls in the recordings that were made by three migratory species – redwings, song thrushes and blackbirds.
This revealed a clear correlation. A greater number of calls from these species were picked up in gardens in densely populated, brightly lit urban areas. Gillings cautions that it is possible the number of birds flying over gardens in the study simply made more noise when flying near to bright light. However, it is at least some evidence that there is increased activity from migrating birds in locations with heightened illumination.
Gillings says that our first port of call should be to reduce the light emitted in urban areas in order to avoid unnecessarily attracting species such as redwings and song thrushes into towns and cities during their migration. People might ensure that security lights point downwards, for example, or that cycle paths are illuminated with low-level lighting only, he suggests. Other research indicates that red light may be less attractive to birds when they are migrating.
Among the many small birds that migrate huge distances every year in the Americas are warbler species such as the yellow-rumped warbler and the Nashville warbler. Some birds of these species travel all the way from North America to Mexico.
When the researcher Jorge Schondube and doctoral student Rodrigo Pacheco-Muñoz, both studying ecology at the National Autonomous University of Mexico, began tagging and recording these warblers at various locations in and near to the city of Morelia, they quickly found something unexpected. The birds that they captured in green spaces within the city were just as healthy in terms of body mass, feather condition and number of parasites as birds of the same species captured at non-urban sites, including a national park outside Morelia.
Schondube says he was surprised how well the warblers in built-up areas were faring: "Most of the time, I thought of those birds as birds that were going to die." But this proved not to be the case.
He also notes that 10 years ago there were no records of the Nashville warbler inside Morelia. But it seems to have taken to relying on well-watered, mature trees in urban green spaces more recently. Well-developed trees can harbour hundreds of insect species and can therefore support warblers, which are insectivores.
When they're not migrating, Swainson's thrushes are usually found in dense forests, chasing after insects or plucking berries off branches (Credit: Alamy).
Because the birds seemed so content among city trees, the researchers argue that providing adequate tree cover could help to accommodate migrating birds should they choose to enter cities. The pair note that they rarely if ever find these warblers in city spaces that aren't so green, which may also indicate the importance of parks as a foothold.
Footholds can, though, become pitfalls, warns Frances Bonier at Queen's University in Ontario. An urban green space might attract birds but not actually provide all the resources that they need when they are breeding, for instance. This is known as an ecological trap.
And Gillings adds that, while a smattering of trees and green roofs in a city will be of benefit to some birds, others require wetlands or large, dense forests to really thrive. Still more rely on pristine coastal areas and so on. It would be a mistake to think we can compensate for the destruction of such habitats by making cities a bit greener. At the end of the day, those specialist species that rely on the world's rich diversity of habitats are the ones most at risk.
With that important caveat in mind, it remains important to ensure that cities are accommodating for wildlife, says Frei. Bird migration routes just happen to bring them close to many cities all around the world, and our bright lights draw them in. Frei proposes that urban planning take this into account. The designers of every new park or housing estate could include some vegetation suitable for birds and other species, for instance.
"We should plan it for all different things together – it's good for people, it's good for the planet, it's good for the wildlife," she asserts.
Pacheco-Muñoz agrees. Cities seem like the antithesis of nature but they really don't have to be because, in reality, they are already full of it. And, as is now clear, they draw many migrating species towards them.
"We need to think of cities as ecosystems," says Pacheco-Muñoz. "If we think about it, we are the masters of this ecosystem – and we can decide how to manage this place."
Reference: Stars Insider
Larva ant queen looks like an alien doll in trippy new microscope images
Larva ant queen looks like an alien doll in trippy new microscope images
Every queen needs a crown. For the queen ant Monomorium triviale, that crown bursts and bubbles out of her head, back and abdomen while she's still a larva — leaving worker ants little confusion about who's the boss, even when the boss is a baby.
Provided by Live Science The larva of a Monomorium triviale queen ant looks like an alien doll
M. triviale are amber-colored ants native to China, Japan and South Korea. The queen ants of the species can produce offspring by laying unfertilized eggs — no males necessary — in a process called thelytokous parthenogenesis. In fact, a new study published March 3 in the journal Zootaxa points out, no male M. triviale have ever been identified; all known M. triviale ants fit into two categories: sterile female workers and fertile queens.
In their new study, researchers wanted to better understand the differences between these two ant classes, starting at the earliest larval stages. The team collected some M. triviale nests from a thicket in the suburbs of Kyoto, Japan, then transferred the immature colony members to artificial nests in a laboratory. There, the researchers studied the ant larvae using several types of high-definition microscopy.
As the worker and queen ants developed, they periodically shed their exoskeletons, taking on strange new forms (or "instars") with every molting. Both queens and workers started as oblong blobs, before developing mouthparts and tiny, spiky hairs along their bodies within a few days of hatching, the researchers wrote.
As the worker and queen ants developed, they periodically shed their exoskeletons, taking on strange new forms (or "instars") with every molting. Both queens and workers started as oblong blobs, before developing mouthparts and tiny, spiky hairs along their bodies within a few days of hatching, the researchers wrote.
But in her final larval form, the queen ant pulled off a look unlike any other. Her body had gone almost completely hairless, the team found, and had instead sprouted 37 doorknob-like lumps, or "tubercles" all along its length, giving her a look something like an alien plushie doll, or a Panic Pete squeeze toy from a parallel universe.
When the researchers probed the interior of these tubercles, they found that the lumps were made of extended skin and cuticle, and they were about twice as thick as any other part of the queen's body. The lumps contained no muscle, ducts or specialized parts, raising the question: What are the ant queen's fleshy lumps actually good for?
The study authors couldn't say for sure, but they pointed to five possible explanations from a 1976 paper whose authors had looked at the morphology of various ant larvae. The structures could help support the larvae's bodies, allow them to cling to nest ceilings or walls, or they might help queens defend against cannibal attacks from other larvae, the researchers wrote.
Alternatively, the lumps could be involved in feeding, possibly being used to hold food to the larva's body surface, or to help pass food between larvae.
"The function of queen-specific tubercles of the M. triviale larvae is still unclear at this time," the authors of the new study wrote in the paper. "Behavioral observations of the interaction between the workers and the queen larvae… will help us understand the hidden but essential roles larvae play in complex ant societies."
It's a lot of look, but M. triviale's larva queens pull it off. Now, scientists just need to figure out why.
Originally published on Live Science.
Everything we know about the Joro - the giant flying spiders multiplying across the East Coast
Everything we know about the Joro - the giant flying spiders multiplying across the East Coast
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An invasive spider species called the Joro has made inroads in Georgia. Big, bright, and capable of weaving webs ten feet deep, the spiders have already managed to freak out some Georgians who have had first hand encounters with the insects.
But will the spiders pose a problem as they continue to spread throughout the eastern US, or will they simply be a bright new addition to the nation's diverse catalog of fauna?
What is a Joro spider?
Joro spiders are big, at least by US standards. The creatures can grow to 3 inches, and have colorful blue and yellow markings on their bulbous bodies, with red markings on their undersides. Their size makes them comparable to the Carolina Wolf Spider, which is the largest wolf spider in the country.
Huntsman spiders, another invasive spider species from Asia which now lives in subtropical regions of Florida, Texas, and California, have larger leg spans but smaller bodies than the Joro.
The spiders are native to Japan and are believed to have traveled to the US as stowaways on cargo ships. Entomologists believe the spiders will be able to survive the cold temperatures of East Coast winters thanks to their fast metabolisms. Because they can survive the cold, they will likely become a permanent fixture in North America.
Joro spiders weave thick, golden webs, and can even use their silk as a sort of parachute that allows them to float through the air to new locations. While that feature allows to to traverse some distance, researchers believe the Joro will likely spread throughout the rest of the US in the same manner they arrived here in the first place; hitching a ride with traveling humans.
Are Joro spiders dangerous?
Only if you're a small insect, like a mosquito or a crop-destroying brown stink bug. While the spiders do hunt using venom, their bites are not harmful to humans.
Despite their namesake - the mythical Japanese JorÅgumo, a spider that can turn itself into a beautiful woman to feast on unsuspecting men - the spiders don't pose any real threat to humans.
If a Joro were to bite a human or a pet, it may not even register, as the spiders' fangs are believed to be too small in most instances to break skin. Bites that do register pain have been compared to bee stings.
The most alarming aspect of the spiders is almost certainly their size, as most Americans are not accustomed to seeing large spiders out in the wild. Their webs are proportional to the spiders' size, and may be intimidating to those who encounter them without knowing about the Joro. Compounding the fear some may experience when encountering a large spider is the fact that they tend to live in groups, meaning it would not be unreasonable for someone to find not just one Joro, but several.
Unfortunately for arachnophobes, the spiders also tend to set up their webs near the edges of forest and alongside people's houses, so the chances of encountering one if you live on the East Coast is fairly high.
Andy Davis, a research scientist in the Odum School of Ecology at the University of Georgia, told NPR that the best thing for people to do if they encounter the spiders is to just leave them alone.
"If they're literally in your way, I can see taking a web down and moving them to the side, but they're just going to be back next year," Mr Davis said.
Will they harm the US ecosystem?
While any new species can upset the balance of an ecosystem, entomologists have not been ringing alarm bells over the new spiders.
Some invasive species prompt calls from local officials to kill them on sight due to the threat they pose local ecosystems. Last year, officials in New York, Pennsylvania, and Ohio called on residents to kill any spotted lanternflies they saw on sight, as the bugs feed on over 70 types of trees and plants. If left unchecked, the insects would cause substantial harm to regional flora.
The Joro spider does not appear to pose that same threat, according to entomologists. If anything, they may be a beneficial addition to the US ecosystem as they tend to eat biting pest insects. Further, they may prove a fruitful source of food for birds and other larger predators.
Reference: Independent: Graig Graziosi
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