Posts Tagged ‘Nature’

by EMILY MAKOWSKI

Plants pollinated by nectar-drinking bats often have flowers that reflect ultrasonic waves, making it easier for the animals to locate flowers through echolocation. But one cactus does the opposite—it absorbs more ultrasound in the area surrounding its flowers, making them stand out against a “quieter” background, according to a preprint published on bioRxiv last month.

Espostoa frutescens is a type of column-shaped cactus found only in the Ecuadorian Andes mountains. It has small flowers on its side that open at night, attracting bats as they fly from flower to flower in search of nectar. One of its main pollinators is Geoffroy’s tailless bat (Anoura geoffroyi).

“Bats are really good pollinators,” Ralph Simon, a postdoc in Wouter Halfwerk’s lab at Vrije Universiteit Amsterdam and the lead author of the preprint, tells The Scientist. “They carry a lot of pollen in their fur, and they have a huge home range so they can transport pollen from plants that grow far apart. For plants with a patchy distribution pattern like this cactus, it’s especially beneficial to rely on bats for pollination,” he says.

For bats to find the flowers at night, they use echolocation, emitting ultrasonic calls too high for humans to hear that bounce off objects and allow the bats to form a mental map of their surroundings. Some plants have evolved techniques that take advantage of this sonar system and allow bats to better detect flowers, such as making their petals more concave, forming a more reflective surface that can bounce more echolocation back to the bat. But E. frutescens takes a different approach.

Each of E. frutescens’s flowers are surrounded by an area of wooly hairs called the cephalium. Simon and colleagues knew from past measurements that the hairs were sound-absorbent, and were interested in seeing whether this part of the cactus could be involved in helping bats find the flowers. They attached a microphone and speaker to a device resembling the shape and size of a bat head in order to mimic a bat, and played prerecorded echolocation calls to the cacti and measured how much sound was reflected back to the bat replica.

The team found that the hairy cephalium absorbed ultrasound, and that the greatest absorption occurred above 90 kHz, in the range of the frequency of Geoffroy’s tailless bat’s echolocation call. The sound that bounced back to the microphone from the cephalium area was about 14 decibels quieter than the sound that bounced off the non-hairy part of the cacti.

It’s a “totally different mechanism” than the reflection method other cacti use, says Simon. “Instead of making the flowers conspicuous, it dampens the background. The background absorbs the ultrasound, and the flowers show up in [the middle of] this absorbent fur.”

This mechanism makes sense from a communication standpoint, writes May Dixon, a graduate student studying bat behavior in Mike Ryan’s lab at the University of Texas at Austin who was not involved with the study, in an email to The Scientist. “If you are trying to send a message, you have to think not only about the message itself but also the context. For example, if you are calling someone, you should be loud enough for them to hear, sure, but you should also call from a quiet place,” she says.

“There is something wonderful about the ways that plants have found to communicate with animals through evolution,” Dixon notes. “A cactus has no sense of what it is to be a bat—it can’t see, smell, or echolocate—but here it is, sending a bat a message in a language that a bat can understand.”

The cephalium appears to have originally evolved to protect flowers from environmental stressors such as UV rays, drying out, getting too cold, or being eaten, but “during evolution, it co-opted another function, and it functions as a sound absorbing structure as well,” says Simon. The evolution of this mechanism benefits both cactus and bat. “From the bat point of view, with this mechanism, they save time. And for them, it’s important to save time, because they have to visit several hundred flowers each night to get enough energy,” he says.

The current study did not look at whether sites on the plants with the highest sound absorption in the bats’ echolocation range “indeed resulted in the highest detection and visitation rates by bats,” says Jan Komdeur, an evolutionary ecologist at University of Groningen in the Netherlands who did not participate in the research, in an email to The Scientist. In the future, researchers could investigate how often real-life bats approach hairy versus experimentally manipulated hairless flowers, he suggests.

Jorge Schondube, an ecologist at the Universidad Nacional Autónoma de México who was not involved with the study, agrees that research on real-life bats is needed. “The pattern’s very clear, but now [researchers] need to show how the mechanism is actually changing the behavior of the bats,” he says.

Still, he’s impressed by the findings so far. “Nature is very creative. And by being creative, it allows the origin of completely new and unimaginable things. It’s really surprising that something like this can happen, and the paper shows it really, really beautifully. . . . What we’re seeing here is something that has not been seen before in terms of sound.”

https://www.the-scientist.com/news-opinion/ecuadorian-cactus-absorbs-ultrasound–enticing-bats-to-flowers-66981?utm_campaign=TS_DAILY%20NEWSLETTER_2020&utm_source=hs_email&utm_medium=email&utm_content=82166272&_hsenc=p2ANqtz-9in3Tqjl731fVW0JE_k3Ht2NOEvCOnql7E5ADhmEp4j43Rrs5Q6gxTipSPvHXAs-8C6MvOvVFdBpktnFeyya1pvZPF2A&_hsmi=82166272

Even on land, crocodiles are no fish out of water. While these reptiles might look lazy and slow sunning on the bank, they can easily pick up speed when necessary, and a scary number can gallop or bound like a horse or a dog.

Bounding is when an animal’s forelimbs hit the ground at the same time, with the back legs pushing off soon after; meanwhile, a gallop is a four-beat sequence whereby the fore and hindlimbs take turns landing.

Freshwater crocodiles from Australia (Crocodylus johnstoni) were historically thought to be the only species capable of doing both. But that’s not actually true. Not even close.

It turns out even scientists have underestimated these creatures. Past research suggested only a handful of croc species were able to gallop, but a new study now adds five more to the mix, suggesting it’s a whole lot more common than we ever thought.

Setting up video cameras around a zoological park in Florida, veterinary scientists analysed the gaits and speeds of 42 individuals from 15 species of crocodylia, which includes true crocodiles (family Crocodylidae), alligators and caimans.

While alligators and caimans were only able to trot on land, the team noticed eight species of crocodile capable of galloping or bounding.

They claim their study is the first to properly document galloping in the Philippine crocodile (Crocodylus mindorensis), the Cuban crocodile (C. rhombifer), the American crocodile (C. acutus), the West-African slender-snouted crocodile (Mecistops cataphractus) and the dwarf crocodile (Osteolaemus tetraspis).

Judging by how common this skill appears to be, there might even be more species that can do the same. There have already been anecdotal reports of galloping in species such as the marsh crocodile (C. palustris) and the New Guinea crocodile (C. novaeguineae).

“We were really surprised at one major thing – despite the different gaits crocodiles and alligators use, they all can run about as fast,” John Hutchinson, a specialist in evolutionary biomechanics at the Royal Veterinary College (RVC), told PA.

No matter what their size, almost every species studied was able to reach nearly 18 kilometres per hour (11 mph), whether it be through trotting, galloping or bounding.

Only crocodiles, however, could use their legs asymmetrically, providing longer stride frequencies, especially among those with smaller body sizes. Why alligators cannot do this remains uncertain, but the researchers think this skill is probably ancestral and has less to do with speed than we thought.

“We suspect that bounding and galloping give small crocodiles better acceleration and manoeuvrability, especially useful for escaping from danger,” explains Hutchinson

“It seems like alligators and caiman stand their ground rather than run away with an extreme gait.”

Similar to other studies, the researchers think the crocodile’s unusual asymmetrical gait came from a long-lost ancestor that lived on the land and had longer legs.

If this is right, it could mean that the ancestors of the alligators somehow lost this ability or no longer express it.

But there’s also another possibility that is rarely acknowledged: the common ancestor of today’s 20 crocodile species may have actually evolved this asymmetrical gait as opposed to inheriting it.

Looking at related species could clear up some of the confusion – the gharial is an Asian fish-eating crocodile that lies outside the Crocodyloidea  and Alligatoroidea ancestry, so if they can be shown to have asymmetrical gaits, it could shed light on how this skill appeared.

But similar to crocodiles and alligators, the gaits of the gharial’s are not well documented, so there’s clearly a lot more research that needs to be done.

“Together, our new observations of asymmetrical gaits and our broader dataset on locomotor kinematics spanning the clade Crocodylia considerably expand our knowledge of their behaviours and natural history,” the authors conclude.

“Importantly, this combined evidence strongly refutes the popular notion that only a few crocodiles use asymmetrical gaits.”

The study was published in Scientific Reports.

https://www.sciencealert.com/approach-with-caution-more-crocodile-species-than-we-thought-can-reach-a-gallop

By Chelsea Whyte

Sometimes stress can be good for a fish. When there are more predators around, killifish in Trinidad grow more brain cells than those that face no predators, and they do so even into adulthood.

“I was surprised to find this because in previous studies, we found that predators inhibit the production of brain cells,” says Kent Dunlap at Trinity College in Connecticut. It seems that killifish swim their own way.

Dunlap and his colleagues examined the brains of a type of wild caught killifish (Rivulus hartii) from three streams on the Caribbean island. In each stream, they gathered about eight adult fish from a location with a high number of predators and about eight from a location with little to no predation. They only used males because previous research on these fish showed that predation affects male but not female brains.

The researchers measured the size of the males’ brains as well as the density of newly grown cells. They found that fish from both spots in each stream had brains similar in size relative to their bodies, but those that had to fight off more predators had nearly double the amount of new brain cells. Dunlap says this may mean that instead of fairly static brains that respond to predators in a timid way, the new brain cells could allow for more responsive behaviour.

To sort out whether this effect is genetic or purely a response to their environment, Dunlap and his team raised fish from each location and then dissected their brains. In the lab, even with an absence of predators, they saw that the increased brain cell growth persisted in fish descended from those that lived in high-predation areas.

“Over evolutionary time, predation has caused the populations to differ genetically, so there’s this intrinsic difference now that’s upheld,” says Dunlap. He adds that this pattern would likely show up in other animals that continue to grow brain cells into adulthood.

“We mammals and birds, once we reach sexual maturation our body and brain don’t grow very much,” he says. “But fish grow throughout their lifetime, as do many other non-birds and non-mammals.”

Journal reference: Royal Society Proceedings B, DOI: 10.1098/rspb.2019.1485

Read more: https://www.newscientist.com/article/2226787-predators-may-make-prey-get-smart-and-grow-more-brain-cells/#ixzz67ovnyDlk


This piglet had some cells from a monkey but died within a week of birth
Tang Hai

By Michael Le Page

Pig-primate chimeras have been born live for the first time but died within a week. The two piglets, created by a team in China, looked normal although a small proportion of their cells were derived from cynomolgus monkeys.

“This is the first report of full-term pig-monkey chimeras,” says Tang Hai at the State Key Laboratory of Stem Cell and Reproductive Biology in Beijing.

The ultimate aim of the work is to grow human organs in animals for transplantation. But the results show there is still a long way to go to achieve this, the team says.

Hai and his colleagues genetically modified cynomolgus monkey cells growing in culture so they produced a fluorescent protein called GFP. This enabled the researchers to track the cells and their descendents. They then derived embryonic stem cells from the modified cells and injected them into pig embryos five days after fertilisation.

More than 4000 embryos were implanted in sows. Ten piglets were born as a result, of which two were chimeras. All died within a week. In the chimeric piglets, multiple tissues – including in the heart, liver, spleen, lung and skin – partly consisted of monkey cells, but the proportion was low: between one in 1000 and one in 10,000.

It is unclear why the piglets died, says Hai, but because the non-chimeric pigs died as well, the team suspects it is to do with the IVF process rather than the chimerism. IVF doesn’t work nearly as well in pigs as it does in humans and some other animals.

The team is now trying to create healthy animals with a higher proportion of monkey cells, says Hai. If that is successful, the next step would be to try to create pigs in which one organ is composed almost entirely of primate cells.

Something like this has already been achieved in rodents. In 2010, Hiromitsu Nakauchi, now at Stanford University in California, created mice with rat pancreases by genetically modifying the mice so their own cells couldn’t develop into a pancreas.

Pig-human chimeras

In 2017, Juan Carlos Izpisua Belmonte’s team at the Salk Institute in California created pig-human chimeras, but only around one in 100,000 cells were human and, for ethical reasons, the embryos were only allowed to develop for a month. The concern is that a chimera’s brain could be partly human.

This is why Hai and his team used monkey rather than human cells. But while the proportion of monkey cells in their chimeras is higher than the proportion of human cells in Belmonte’s chimeras, it is still very low.

“Given the extremely low chimeric efficiency and the deaths of all the animals, I actually see this as fairly discouraging,” says stem cell biologist Paul Knoepfler at the University of California, Davis.

He isn’t convinced that it will ever be possible to grow organs suitable for transplantation by creating animal-human chimeras. However, it makes sense to continue researching this approach along with others such as tissue engineering, he says.

According to a July report in the Spanish newspaper El País, Belmonte’s team has now created human-monkey chimeras, in work carried out in China. The results have not yet been published.

While interspecies chimerism doesn’t occur naturally, the bodies of animals including people can consist of a mix of cells. Mothers have cells from their children growing in many of their organs, for instance, a phenomenon called microchimerism.

Journal reference: Protein & Cell, DOI: 10.1007/s13238-019-00676-8

Read more: https://www.newscientist.com/article/2226490-exclusive-two-pigs-engineered-to-have-monkey-cells-born-in-china/#ixzz67RYaU5XS


S. roeselii is shown here contracting down to where it’s holding onto a surface.

By Yasemin Saplakoglu

Tiny, brainless blobs might be able to make decisions: A single-celled organism can “change its mind” to avoid going near an irritating substance, according to new findings.

Over a century ago, American zoologist Herbert Spencer Jennings conducted an experiment on a relatively large, trumpet-shaped, single-celled organism called Stentor roeselii. When Jennings released an irritating carmine powder around the organisms, he observed that they responded in a predictable pattern, he wrote in his findings, which he published in a text called “Behavior of the Lower Organisms” in 1906.

To avoid the powder, the organism first would try to bend its body around the powder. If that didn’t work, the blob would reverse the movement of its cilia — hairlike projections that help it move and feed — to push away the surrounding particles. If that still didn’t work, the organism would contract around its point of attachment on a surface to feed. And finally, if all else failed, it would detach from the surface and swim away.

In the decades that followed, however, other experiments failed to replicate these findings, and so they were discredited. But recently, a group of researchers at Harvard University decided to re-create the old experiment as a side project. “It was a completely off-the-books, skunkworks project,” senior author Jeremy Gunawardena, a systems biologist at Harvard, said in a statement. “It wasn’t anyone’s day job.”

After a long search, the researchers found a supplier in England who had collected S. roeselii specimens from a golf course pond and had them shipped over to Gunawardena’s lab. The team used a microscope to observe and record the behavior of the organisms when the scientists released an irritant nearby.

First, they tried releasing carmine powder, the 21st century organisms weren’t irritated like their ancestors were. “Carmine is a natural product of the cochineal beetle, so its composition may have changed since [Jennings’] day,” the researchers wrote in the study. So they tried another irritant: microscopic plastic beads.

Sure enough, the S. roeselii started to avoid the beads, using the behaviors that Jennings described. At first, the behaviors didn’t seem to be in any particular order. For example, some organisms would bend first, then contract, while others would only contract. But when the scientists did a statistical analysis, they found that there was indeed, on average, a similar order to the organisms’ decision-making process: The single-celled blobs almost always chose to bend and alter the direction of their cilia before they contracted or detached and swam away, according to the statement.

What’s more, the researchers found that, if the organism did reach the stage of needing to contract or detach, there was an equal chance that they would choose one behavior over the other.

“They do the simple things first, but if you keep stimulating, they ‘decide’ to try something else,” Gunawardena said. “S. roeselii has no brain, but there seems to be some mechanism that, in effect, lets it ‘change its mind’ once it feels like the irritation has gone on too long.”

The findings can help inform cancer research and even change the way we think about our own cells. Rather than being solely “programmed” to do something by our genes, “cells exist in a very complex ecosystem, and they are, in a way, talking and negotiating with each other, responding to signals and making decisions,” Gunawardena said. Single-celled organisms, whose ancestors once ruled the ancient world, might be “much more sophisticated than we generally give them credit for,” he said.

The findings were published Dec. 5 in the journal Current Biology.

https://www.livescience.com/single-celled-organisms-decisions.html?utm_source=notification

by David Nield

Scientists researching a key aspect of biochemistry in living creatures have been taking a very close look at the tiny Caenorhabditis elegans roundworm. Their latest results show that when these nematodes get put under more biochemical stress early in their lives, they somehow tend to live longer.

This type of stress, called oxidative stress – an imbalance of oxygen-containing molecules that can result in cellular and tissue damage – seems to better prepare the worms for the strains of later life, along the same lines as the old adage that whatever doesn’t kill you, makes you stronger.

You might think that worm lifespans have no bearing on human life. And surely, until we have loads more research done in this field, it would be a big leap to say the same principles of prolonging one’s lifespan might hold true for human beings.

But there’s good reason to put C. elegans through the paces. This model organism has proven immensely helpful for researchers trying to better understand key biological functions present in worm and human alike – and oxidative stress is one such function.

The little wriggly creatures are known to have significant variations in their lifespan even when the whole population is genetically identical and grows up in the exact same conditions. So the team went looking for other factors that affect C. elegans’ longevity.

“The general idea that early life events have such profound, positive effects later in life is truly fascinating,” says biochemist Ursula Jakob from the University of Michigan.

Jakob and her colleagues sorted thousands of C. elegans larvae based on the oxidative stress levels they experienced during development – this stress arises when cells produce more oxidants and free radicals than they can handle. It’s a normal part of the ageing process, but it’s also triggered by exercise and a limited food supply.

One way to measure this stress is by the levels of reactive oxygen species (ROS) molecules an organism produces – simply put, this measurement indicates the biochemical stress an organism is under. In the case of these roundworms, the more ROS were produced during development, the longer their lifespans turned out to be.

To explain how this effect of ROS might come about, the researchers went looking for changes in the worms’ genetic regulation, specifically those genes that are known to be involved in dealing with oxidative stress.

While doing so, they detected a key difference – the nematodes exposed to more ROS during development appeared to have undergone an epigenetic change (a gene expression switch that can happen due to environmental influences) that increased the oxidative stress resistance of their body’s cells.

There are still a lot of questions to answer, but the researchers think their results identify one of the stochastic – or random – influences on the lifespan of organisms; it’s something that has been hypothesised in the field of the genetics of ageing. And down the line, it may turn out to be relevant for ageing humans, too.

“This study provides a foundation for future work in mammals, in which very early and transient metabolic events in life seem to have equally profound impacts on lifespan,” the researchers conclude.

The study has been published in Nature.

https://www.sciencealert.com/biological-stress-in-early-life-could-be-one-of-the-keys-to-a-long-lifespan?perpetual=yes&limitstart=1

By Layal Liverpool

We have checked the pulse of a wild-living blue whale for the first time, and discovered something remarkable. When blue whales dive for food they can reduce their heart rates to as low as 2 beats per minute. This is well below the rates the large animals were calculated to have. Previous predictions were that the whales would have a resting heart rate of 15 beats per minute.

The finding is particularly extraordinary given that whales have an energetically demanding feeding method, says Jeremy Goldbogen at Stanford University, California. During lunge feeding, a blue whale engulfs a volume of prey-filled water that can be larger than its own body.

From a large inflatable boat in Monterey Bay, California, Goldbogen and his team used a 6-metre pole to attach heart rate monitors to a single blue whale. The monitors were held in place with suction cups. The researchers were then able to monitor the whale’s heart rate for almost 9 hours. They detected heart rates of just 2 to 8 beats per minute hundreds of times.

The whale dived for as long as 16.5 minutes at a time, reaching a maximum depth of 184 metres, and stayed at the surface for intervals ranging from 1 to 4 minutes. The whale’s heart rate was at its lowest when it was diving for food and shot up after it resurfaced, reaching a peak of 37 beats per minute.

The reduction in heart rate during dives enables whales to temporarily redistribute oxygenated blood from the heart to other muscles needed for lunging, says Goldbogen. Whales then recover upon resurfacing by dramatically increasing their breathing and heart rate, he says.

These results demonstrate “the quite extraordinary level of flexibility and control that these diving mammals have over their heart rate and blood flow”, says Sascha Hooker at the University of St Andrews, UK.

Recent technological advances have enabled these kinds of readings to be collected from free-living whales, says Hooker. “These are opening the door to a much greater understanding of how these animals are able to perform some quite amazing feats of diving and exercise,” she says.

Journal reference: PNAS, DOI: 10.1073/pnas.1914273116

Read more: https://www.newscientist.com/article/2224674-a-blue-whales-heart-beats-just-twice-a-minute-when-it-dives-for-food/#ixzz66PRZuGAd