Acipenser sinensis NatureServe Explorer Species Reports &#8212; NatureServe Explorer is a source for authoritative conservation information on more than 50,000 plants, animals and ecological communtities of the U.S and <a href="https://www.earth.com/image/the-fall-rhapsody-in-ottawa/">Canada.</a> NatureServe Explorer provides in-depth information on rare and endangered species, but includes common plants and animals too. NatureServe Explorer is a product of NatureServe in collaboration with the Natural Heritage Network.
ITIS Reports &#8212; ITIS (the Integrated Taxonomic Information System) is a source for authoritative taxonomic information on plants, animals, fungi, and microbes of North America and the world.
FWS Digital Media Library &#8212; The U.S. Fish and Wildlife Service&#8217;s National Digital Library is a searchable collection of selected images, historical artifacts, audio clips, publications, and video.The Chinese sturgeon (Acipenser sinensis; Chinese: 中華鱘; pinyin: zhōnghuá xún) is a critically endangered member of the family Acipenseridae in the order Acipenseriformes. Historically, this anadromous fish was found in China, Japan, and the Korean Peninsula, but it has been extirpated from most regions due to habitat loss and overfishing. It is strictly protected by the Chinese government, named a &#8220;national treasure&#8221; much like its mammalian counterpart, the giant panda. China has several conservation programmes, including reserves specifically aimed at this species and restocking through release of juveniles in the Yangtze River.

Acipenser sinensis

Diving birds such as puffins and penguins face a higher risk of extinction compared to non-diving birds, according to a study from the Milner Centre for Evolution at the <a href="https://www.bath.ac.uk/">University of Bath</a>. The researchers explained that a highly specialized foraging strategy makes these birds less capable of adapting to changing environments.



"Given the new evolutionary pressures being applied to the world's biodiversity by climate change, understanding if highly specialized taxa are evolutionarily ‘trapped’ in their current niches is of great interest," wrote the study authors.



Dr. Jane Younger and Joshua Tyler studied the evolution of diving in modern waterbirds. They set out to investigate how diving has impacted the morphology of these birds, how the species evolved to increase diversity, and the risk of extinction among waterbirds.&nbsp;



"We show that diving has been acquired independently at least 14 times within waterbirds, and this acquisition is apparently irreversible, in a striking example of asymmetric evolution," said the study authors.



The experts determined that body size evolved differently among waterbirds depending on the type of diving they did. They also found that diving traits were not reversed by evolution.



"Three key diving techniques are employed within waterbirds: wing-propelled pursuit diving (e.g. penguins), foot-propelled pursuit diving (e.g. cormorants) and plunge diving (e.g. gannets)," explained the researchers.&nbsp;



The study revealed that wing divers and foot divers tend to have larger body sizes adapted for swimming. On the other hand, plunge divers tend to be more constrained in their body size, as they were better adapted for flying than swimming.



“Our work shows that rather than being a random process, there are predictable patterns to evolution," said Tyler. “Waterbirds were grouped together as being highly related following genetic analysis of the bird family tree in 2015, so I wanted to investigate how evolving to be able to dive had affected their body shape, niche adaptation and evolutionary diversity."



“For example, penguins are highly adapted for their environment - they have a torpedo body shape that helps them swim fast, but they don’t fly and they can’t move that well on land."



“This means they can’t easily adapt to other environments or types of diet. In contrast, plunge divers like gulls are more generalists - they eat anything from fish to Cornish pasties - and we found they are exploding in diversity."



“Our data show that the specialist birds are in more trouble in terms of future extinction, and may be evolving into an evolutionary dead end.”



The study is published in the journal <a href="http://dx.doi.org/10.1098/rspb.2022.2056">Proceedings of the Royal Society B Biological Sciences</a>.



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By <a href="mailto:csexton@earth.com">Chrissy Sexton</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Editor



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Diving birds face a greater risk of extinction

Diving birds such as puffins and penguins face a higher...

Every year, an estimated one-third of the U.S. population uses DEET to protect themselves from the bites of insects such as <a href="https://www.earth.com/news/mosquitos-use-unbreakable-system-to-track-human-blood/">mosquitos</a> and ticks. DEET (N,N-diethyl-meta-toluamide) is the active ingredient in more than 120 different repellent products that come in the form of sprays, lotions and roll-ons, or impregnated materials such as towelettes and wipes. It is an important weapon in the fight against diseases, such as Zika, West Nile fever, dengue and malaria that are carried by mosquitos, and diseases such as Lyme and Rocky Mountain spotted fever that are spread by ticks.&nbsp;



Although DEET has been used effectively to keep these disease-bearing insects at bay since 1957, when it was first made available to the public, there are some issues with its use. It has an unpleasant odor that puts some people off, and its repellent effects do not last very long before it has to be reapplied. To be effective, it has to be applied at the correct concentration, and even then there are some people who have reported sensitivity, with symptoms such as rashes, skin irritation, numb or burning lips, nausea, headaches,&nbsp;and dizziness. DEET also has the property of damaging certain materials, including plastics.



Researchers in many laboratories have sought chemical alternatives to DEET, and to the other popular repellent, known as picaridin. Although some synthetic substances have shown promise, none has proved as effective as DEET or picaridin at disrupting a mosquito’s ability to locate humans. &nbsp;Francesca Dani, from the University of Firenze, Italy, and her colleagues, had some previous success using two plant-based natural repellents that they modified to extend the protective timespan beyond that of DEET. However, they still wished to improve on these products further.&nbsp;



In their new research, published in the American Chemical Society's <a href="http://dx.doi.org/10.1021/acs.jafc.2c05537">Journal of Agricultural and Food Chemistry</a>, Dani and her colleagues synthesized additional cyclic hydroxyacetals from inexpensive, commercially available carbonyls. The new cyclic compounds had pleasant, much fainter odors and were easier to dissolve in water, meaning they can be formulated without high concentrations of alcohol. Some were as effective as DEET and picaridin at repelling Asian tiger mosquitos, which have spread widely in the U.S. and carry diseases, including encephalitis, dengue and dog heartworm.&nbsp;



Like picaridin, these new formulations provided human volunteers with more than 95 percent protection from bites for at least eight hours, while DEET’s protection rapidly declined below that level after just two hours. Toxicity of some of the most active new compounds was comparable to or lower than that of the traditional repellents. Two hydroxyacetals were also less likely to cause immune reactions or to penetrate cell layers than picaridin.&nbsp;



According to the authors, an ideal skin repellent needs to have the following attributes: highest repellent activity at low dose; negligible acute or chronic toxicity for humans, animals, and the environment; negligible or faint and pleasant odor; non-greasy feeling on the skin; resistance to abrasion from clothing, evaporation, and absorption from the skin surface; should not wash-off from sweat or rain; and should be easy to formulate in a water medium.



During their research, the scientists assessed all these attributes and found that their specifically formulated cyclic acetals and hydroxyacetals have potential to tick most of the boxes and could be effective repellents. The researchers conclude that their compounds represent a new class of promising mosquito repellents that can compete favorably with DEET and picaridin in terms of efficacy and safety.



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By <a href="mailto:bosman@truewan.co.za">Alison Bosman</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer



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Chemists take a new approach to developing insect repellents

Every year, an estimated one-third of the U.S. population uses...

In the formation of potentially habitable <a href="https://www.earth.com/news/astronomers-have-found-a-planet-that-could-support-life/">planets</a>, ices are a vital ingredient since they are the main source of several critical elements, such as carbon, hydrogen, oxygen, nitrogen, and sulfur (referred collectively as “CHONS”). These basic elements are important ingredients in both planetary atmospheres and molecules such as alcohols, sugars, or simple amino acids.



Now, using the James Webb Space Telescope (JWST), an international team of astronomers has obtained for the first time an in-depth inventory of the deepest and coldest ices in a molecular cloud. Besides simple ices like water, the experts identified frozen forms of a variety of molecules, ranging from carbonyl sulfide, ammonia, and methane to the simplest organic molecule methanol. To date, this is the most comprehensive mapping of the icy ingredients available to create future generations of planets and stars, before they are heated during the emergence of young stars.



“Our results provide insights into the initial, dark chemistry stage of the formation of ice on the interstellar dust grains that will grow into the centimeter-sized pebbles from which planets form in disks,” said study lead author Melissa McClure, an astronomer at the <a href="https://www.universiteitleiden.nl/en/science/astronomy">Leiden Observatory</a> in the Netherlands. “These observations open a new window on the formation pathways for the simple and complex molecules that are needed to make the building blocks of life.”



The scientists also found evidence for more complex molecules and, although they did not yet manage to definitely attribute these signals to specific molecules, this is a major step toward the identification of complex molecules present in the icy depths of molecular clouds before stars are born.



“Our identification of complex organic molecules, like methanol and potentially ethanol, also suggests that the many star and planetary systems developing in this particular cloud will inherit molecules in a fairly advanced chemical state,” explained study co-author Will Rocha, another&nbsp; astronomer at Leiden. “This could mean that the presence of precursors to prebiotic molecules in planetary systems is a common result of star formation, rather than a unique feature of our own solar system.”



Moreover, by detecting the sulfur-bearing ice carbonyl sulfide, the experts were able to estimate for the first time the amount of sulfur embedded in icy pre-stellar dust grains. As in the case of the other CHONS elements, this amount is less than the total amount expected to be present in the examined cloud, based on its density. Future research is needed to understand where these elements are hiding.&nbsp;



“The fact that we haven’t seen all of the CHONS that we expect may indicate that they are locked up in more rocky or sooty materials that we cannot measure,” McClure explained. “This could allow a greater diversity in the bulk composition of terrestrial planets.”



“This is just the first in a series of spectral snapshots that we will obtain to see how the ices evolve from their initial synthesis to the comet-forming regions of protoplanetary disks. This will tell us which mixture of ices - and therefore which elements - can eventually be delivered to the surfaces of terrestrial exoplanets or incorporated into the atmospheres of giant gas or ice planets,” she concluded.



The study is published in the journal <a href="https://www.nature.com/articles/s41550-022-01875-w">Nature Astronomy</a>.



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By <a href="mailto:andrei.ionescu5891@gmail.com">Andrei Ionescu</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer



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Astronomers map the “dark chemistry” of outer space

In the formation of potentially habitable planets, ices are a...

Protected natural areas in the UK are struggling to halt declines in insects and <a href="https://www.earth.com/video/spiders-are-using-their-webs-to-extend-their-hearing/">spiders</a>. Protected habitats including nature reserves, Sites of Special Scientific Interest (SSSIs) and Special Areas of Conservation have long been a key tool in conservation efforts.



A <a href="https://www.sciencedirect.com/science/article/pii/S0006320722004372">new study</a> collating records for 1,230 invertebrate species between 1990 and 2018 suggests that protected areas can still experience biodiversity decline.



Researchers from the <a href="https://www.ceh.ac.uk/">UK Centre for Ecology &amp; Hydrology</a> (UKCEH) found that while protected areas were richer in species than unprotected areas, both have suffered similar rates of decline in native insects and spiders over the past 30 years. In particular, the study found severe declines among pollinators, such as bees and hoverflies.



“We see parallel trends for invertebrates in both protected and unprotected areas,” said Dr. Rob Cooke, lead author of the study. “It is worrying, as you would expect species to show more positive trends in protected areas.”



The researchers used data from invertebrate recording schemes that contained observations of ants, bees, hoverflies, ladybirds, spiders and wasps. The team examined changes in biodiversity throughout the study period.



The results showed that there were almost double the number of rare species in protected areas compared to unprotected parts of the UK. These trends remained stable in both protected and unprotected areas, suggesting that rare species benefit from conservation efforts. However, strong declines were found for common species, especially in protected areas.



The study showed that between 1990-2018:



<ul><li>Occupancy of all invertebrates in protected areas declined by 12.8% while in unprotected areas it declined by 11.5%.</li><li>Pollinators declined by 17.5% in protected areas and 20.3% in unprotected areas</li><li>Common species declined by 12.8% in protected areas and 6% in unprotected areas</li></ul>



“Protected areas are often designated specifically to help rare species. But the more common species appear to be falling through the cracks. It should serve as a warning as today’s common species can be tomorrow’s rare species," said Dr. Cooke.



The experts suggest more can be done, such as evidence-based policies, targets and management focused more on the effectiveness, rather than just the coverage of protected areas. The research team is optimistic that this signals an opportunity to strengthen protected areas and better conserve biodiversity.



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By <a href="mailto:katherinebucko@gmail.com">Katherine Bucko</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer



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Protected areas are failing to safeguard biodiversity

Protected natural areas in the UK are struggling to halt...

A recent study led by the <a href="https://www.st-andrews.ac.uk/">University of St Andrews</a> in Scotland has found that humans retain an understanding of gestures made by other great apes, such as chimpanzees, bonobos, or orangutans, even though we no longer use them ourselves. The identification of over 80 gestural signals that are shared across a variety of non-human apes provides the first evidence of intentional <a href="https://www.earth.com/news/pigs-lack-the-skills-for-referential-communication/">communication</a> outside human language.



The scientists tested humans’ understanding of the ten most common gestures employed by chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) using an online game in which over 5,500 participants were asked to watch 20 short videos of ape gestures and select the meaning of each gesture from four possible answers.&nbsp;



The results revealed that participants performed significantly better than expected by chance, correctly identifying the meaning of the gestures more than 50 percent of the time. Moreover, providing contextual information about what the apes were doing only marginally increased participants’ success rates in interpreting the meaning of the gestures.



While video playback experiments have traditionally been used to test human language comprehension in non-human primates, this experiment reversed the paradigm in order to assess humans’ ability to understand the gestures of our closest evolutionary relatives. While the results clearly show that we have a strong capacity of understanding these gestures, it is still unclear whether this ability is genetically inherited, or whether humans and other primates share an ability to understand meaningful signals due to their general intelligence, similar social types of interactions and goals, and physical resemblance.



“All great apes use gestures, but humans are so gestural – using gestures while we speak and sign, learning new gestures, pantomiming etc. – that it’s really hard to pick out shared great ape gestures just by observing people. By showing participants videos of common great ape gestures instead, we found that people can understand these gestures, suggesting that they may form part of an evolutionarily ancient, shared gesture vocabulary across all great ape species including us,” concluded lead author Kirsty Graham, a research fellow in Psychology and Neuroscience at St Andrews.



The study is published in the journal <a href="http://dx.doi.org/10.1371/journal.pbio.3001939">PLOS Biology</a>. In addition, people can take a quiz version of the experiment <a href="https://research.sc/participant/login/dynamic/505CF355-CEF5-44ED-B2F1-2CBA484BD2FA">here</a>.&nbsp;



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By <a href="mailto:andrei.ionescu5891@gmail.com">Andrei Ionescu</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer



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Humans can understand the gestures of other great apes

A recent study led by the University of St Andrews...

Birds make use of a range of different mating systems to maximize their reproductive output. Ninety percent of bird species are monogamous, meaning that they have a single partner during a <a href="https://www.earth.com/news/plastic-additives-reduce-breeding-success-of-corals/">breeding</a> season. Partnerships may last only the time it takes to raise the chicks, or they may last a lifetime, as in the case of swans and geese. Having two parents sharing the work in this way reduces the load on each parent and is considered the most effective way of ensuring chick survival.



However, a small percentage of birds are polygamous. This means that a bird will have two or more partners of the opposite sex at the same time, and parents will not share equally in chick-rearing duties. In the case where a male can monopolize a group of females, this is called polygyny. He will protect and fertilize all the females, but will play no part in brood rearing. Where a female mates with several males (polyandry), she leaves each male to brood and rear the chicks alone, while she seeks out more breeding opportunities.&nbsp;



Scientists do not know why these different mating systems have evolved. They assume that each system maximizes the reproductive output of birds in different environmental circumstances, but this has not been proven. In a new study, an international team led by scientists from Bath university has analyzed the genomes of 150 bird species, spanning all the major bird families and from locations across the world, and has come up with a novel explanation for the evolution of polygamy in birds.&nbsp;



The researchers measured the levels of heterozygosity in the genomes of the birds. This refers to the extent of differences between the genes inherited from a bird’s mother and from its father. Greater heterozygosity is an indication of increased genetic diversity, which is important for bird populations to be able to adapt to changing environmental circumstances. But when the researchers estimated the levels of genetic diversity across each species, there was no evidence that polygamous species were any more diverse than monogamous species.



They also looked at the frequency of gene mutations in each species and whether these mutations affected the production of the proteins they coded for, or whether they were “silent”. The former, called non-synonymous polymorphisms, are often detrimental to the individual, whereas silent mutations are not expressed and are generally harmless.



The results, published in the journal <a href="http://dx.doi.org/10.1093/evolut/qpac010">Evolution</a>, showed that, relative to the number of silent mutations, the polygamous bird species had significantly fewer potentially damaging mutations that changed the coding sequences for proteins.&nbsp;



Kees Wanders, PhD student at the <a href="https://www.bath.ac.uk/">University of Bath</a> and first author of the paper, explained the significance of this result: “Species evolve through natural selection, where harmful mutations are removed from the population in the long term because individuals with the mutation don’t survive long enough to breed, or individuals with beneficial adaptations survive for longer. However, species also evolve through sexual selection, where evolution is shaped by individuals competing for access to mates, so that only the most desirable characteristics are successfully passed down to offspring.”



“This research suggests that sexual selection aligns with natural selection in birds, so that harmful mutations are removed more efficiently in polygamous populations, where sexual selection is particularly strong.”



Previous studies on fruit flies (Drosophila melanogaster) in the laboratory have also identified genetic differences that occur in male and female flies that are polygamous, in comparison with those that are monogamous. These genetic changes are not necessarily beneficial to the females, but appear to serve the interests of the males.



“There are many different theories about why polygamy evolved in these [animal] species, but we’ve found the first evidence that it increases the efficiency of natural selection by rooting out harmful mutations and avoiding the effects of inbreeding," said Wanders. "It’s been previously observed by others in the lab in fruit flies, but this is the first time it’s been observed in wild populations of birds.”



“I had a hypothesis that in polygamous species, where individuals can’t easily find a mate and have to travel further to find a breeding partner, that this would mean there would be more genetic diversity in these species. However, we were surprised to find there was no evidence for this - instead we found that these species had fewer harmful mutations," said study co-author Dr. Araxi Urrutia.



“Despite this apparent evolutionary advantage, most birds tend to stick together to raise their chicks because it gives their offspring a better chance of survival.”



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By <a href="mailto:bosman@truewan.co.za">Alison Bosman</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer



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Polygamous birds carry fewer harmful genetic mutations

Birds make use of a range of different mating systems...

A new study led by the <a href="https://illinois.edu/">University of Illinois Urbana-Champaign</a> (U of I) has examined two ecosystems – one with pumas and one without – to better understand the ways <a href="https://www.earth.com/news/prehistoric-megatooth-sharks-were-apex-predators/">apex predators</a> impact the abundance, diversity, and habits of other animals, including smaller predators. By using grids of motion-activated cameras, the experts followed multiple members of the order Carnivora to clarify how the largest carnivore in each locale influenced the presence and behavior of other animals from the same ecosystem.



“Nobody’s really looked at how the whole carnivore community changes when you lose that top predator,” said lead author Alex Avrin, a scientist at the <a href="https://wildlife.ca.gov/">California Department of Fish and Wildlife</a>, who conducted this study as an M.S. student at the U of I.



Previous research has shown that pumas tend to suppress populations of medium-sized predators such as coyotes, which generally do their best to avoid pumas. By reducing coyote populations, the presence of pumas allows other smaller carnivores to flourish. Moreover, since pumas leave behind a large amount of carrion, a host of scavengers ranging from microbes to birds can feast on these remains. By contrast, coyotes target smaller species and consume most of what they kill, thus leaving less behind for other animals.



To compare the dynamics of ecosystems with and without pumas - and explore whether in the absence of pumas, coyotes step up and fill the role of the apex predator – the scientists deployed grids of motion-activated cameras in various locations in the southern Santa Cruz Mountains of California (which has a large population of pumas, as well as coyotes, bobcats, gray foxes, racoons, and stripped skunks) and across the vast military installation of Fort Hood, Texas (which has the same populations of carnivores but no pumas).



As expected, the recordings revealed that in places where pumas were present, coyotes were rarely seen. Although other carnivores also appeared to avoid pumas, they used areas frequented by pumas more than coyotes, but at times where pumas were absent. By contrast, in Fort Hood, coyotes had a different effect on other carnivores.



“If coyotes were filling that same apex role that pumas do, we would expect them to suppress bobcats - their next largest competitor - releasing the smaller carnivores. And what we found is that they really just suppressed everything – bobcats and the other carnivores,” Avrin reported.



However, the researchers observed that, in the absence of pumas, more intensive grazing by deer occurred. Since coyotes cannot control those larger prey populations in the same way, they end up suppressing mostly smaller prey populations.



“This study gives us a fuller picture of the changes that occur when an apex predator goes missing. While many people think that smaller carnivores can move into the apex role, we see that mesocarnivores like coyotes don’t provide the same effects as a true apex predator. This highlights how important it is to keep each species in place for an intact ecological community,” concluded senior author Maximilan Allen, a professor of Natural Resources and Environmental Sciences at the U of I.



The study is published in the journal <a href="http://dx.doi.org/10.1002/ecs2.4383">Ecosphere</a>.



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By <a href="mailto:andrei.ionescu5891@gmail.com">Andrei Ionescu</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer



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What happens when an apex predator goes missing?

A new study led by the University of Illinois Urbana-Champaign...

In 1947, the <a href="https://thebulletin.org/">Bulletin of Atomic Scientists</a> established a so-called “<a href="https://www.earth.com/news/doomsday-clock-midnight-apocalypse/">Doomsday Clock</a>” in order to provide a measurement of the global existential threats the world faced at the dawn of the nuclear weapons age. Now, by setting the clock at 90 seconds to midnight – the closest it has been since its establishment – an international team of scientists is warning that humanity’s continued existence is at greater risk than ever before, particularly as a result of Russia’s invasion of Ukraine.



“We are living in a time of unprecedented danger, and the Doomsday Clock time reflects that reality. Ninety seconds to midnight is the closest the clock has ever been set to midnight, and it’s a decision our experts do not take lightly,” said Rachel Bronson, the president and CEO of the Bulletin.



The hands of the clock are set each year by the Bulletin’s science and security board, with the assistance of a wide range of scientists worldwide, including ten Nobel prize laureates. While in 1953, after the first detonation of a hydrogen bomb, the clock was set two minutes to midnight, and during the Cuban missile crisis in 1962 at seven minutes to midnight, in 2020, it was set at a record 100 seconds to midnight – a record now once more broken due to the Ukraine crisis.



“Russia’s war on Ukraine has raised profound questions about how states interact, eroding norms of international conduct that underpin successful responses to a variety of global risks. And worst of all, Russia’s thinly veiled threats to use nuclear weapons remind the world that escalation of the conflict – by accident, intention, or miscalculation – is a terrible risk,” the experts wrote in a <a href="https://thebulletin.org/2023/01/press-release-doomsday-clock-set-at-90-seconds-to-midnight/#post-heading">statement</a> accompanying the decision.



At the clock announcement, a journalist from the Russian state-run news agency <a href="https://tass.com/">Tass</a> asked whether the provision of modern armaments to Ukraine by the West had an impact on arms control and the risk of a nuclear war, and thus on the deeply disturbing change in the Doomsday Clock.



“The U.S. and Russia have a strong shared interest in avoiding nuclear war and in minimizing nuclear risks and we should be able to pursue this,” answered Steve Fetter, a professor of Public Policy at the <a href="https://www.umd.edu/">University of Maryland</a>. “U.S. military assistance to Ukraine may complicate those efforts, but I think [it] is essential for the long-term risks of nuclear war, nuclear proliferation, that Ukraine is able to resist the invasion and repel Russian forces. And so we should do everything we can to support Ukraine in that,” he concluded.



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By <a href="mailto:andrei.ionescu5891@gmail.com">Andrei Ionescu</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer



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Doomsday Clock set closer to midnight than ever before

In 1947, the Bulletin of Atomic Scientists established a so-called...

Living organisms need <a href="https://www.earth.com/news/rapid-changes-in-oxygen-linked-to-first-mass-extinction/">oxygen</a> in order to respire, which involves converting stored chemical energy into useful forms such as heat and kinetic energy. They require this energy in order to move, grow, reproduce and carry out all their daily activities. Plants produce oxygen via the process of photosynthesis, but animals have to take it in from the air or water in which they live.&nbsp;



Oxygen is not very soluble in water and it diffuses slowly through this medium. This means that aquatic ecosystems are particularly vulnerable to low oxygen conditions, known as hypoxia. If levels of dissolved oxygen (DO) are too low, aquatic organisms are affected. Fish and other aquatic species may die, altering the food chains and community structure in the ecosystem.&nbsp;



Although a lot of research on hypoxia (the depletion of DO below levels known to be harmful to fish and other aquatic aerobic life) has been conducted in lakes, as well as in coastal and marine ecosystems, not much is known about the prevalence of hypoxia in rivers or streams. Overall, it was thought to be a rather rare occurrence when rivers or streams experienced hypoxia, but little research has been done. Oxygen levels are usually related to the photosynthetic activity of plants, and the flow of water; moving water carries more oxygen than water that stands still.



Until now, the prevalence and dynamics of hypoxia outbreaks in inland rivers and streams has not been known. A new study led by&nbsp;Professor Joanna Blaszczak from the <a href="https://www.unr.edu/">University of Nevada, Reno</a> shows hypoxia is not a rare event in the world’s rivers and streams at all. On the contrary, it is far more common than was once thought.&nbsp;



The team of researchers used data from published reports to assess the distribution, frequency, and global extent of riverine hypoxia using 118,369,376 paired DO and water temperature measurements from 125,158 unique locations in 93 countries and territories across six continents. The data spans over 100 years from 1900 to 2018.



The report, published in the journal&nbsp;<a href="https://aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lol2.10297">Limnology and Oceanography Letters</a>, defines hypoxia as having an oxygen concentration of less than 2 milligrams per liter of water. According to the findings, hypoxia was recorded in rivers and streams in 53 countries, with 12.6 percent of all locations in the study exhibiting at least one hypoxic measurement over the study period.&nbsp;



“Hypoxia in coastal waters and lakes is widely recognized as a detrimental environmental issue, yet we have lacked a comparable understanding of hypoxia in rivers,” said Professor Blaszczak, who is with the University’s&nbsp;<a href="https://www.unr.edu/cabnr">College of Agriculture, Biotechnology &amp; Natural Resources</a>. “While 12.6 percent might not seem like a huge percentage, previously it was generally thought that occurrences of hypoxia in rivers and streams were exceedingly rare. Having demonstrated the presence of hypoxia in one of every eight river locations is definitely a game changer in terms of how we need to think of and give attention to the issue of hypoxia in rivers and streams."



Professor Blaszczak explained that, in the past, DO readings were taken manually with a hand-held probe. However, advances in measuring hypoxia over the past 15 years, using field-deployable dissolved oxygen sensor technology, have enabled researchers to measure oxygen levels constantly, and far more accurately. The team found that oxygen levels are higher during the day than at night, because photosynthesis takes place during the hours of daylight, enriching the water with oxygen.



“Photosynthesis by algae produces oxygen that is released into the water column,” explained Professor Blaszczak. “So, you’re not getting a true picture of hypoxia occurrence if you only measure during the day. Hypoxic conditions are much more likely to develop in the early morning hours, after the lack of photosynthesis all night. The newer technology allows for us to capture that data.”



The data showed that that hypoxia in rivers was most present in warmer, smaller and lower-gradient, stiller waters, where oxygen isn’t being “stirred” into the water from turbulence. Blaszczak says the research found these conditions occur most often in rivers that drain naturally occurring wetlands, as well as in rivers draining some urban areas, where human actions have created hypoxic conditions.



“We as people managing waters often influence these conditions - by extracting water, building dams and increasing the amount of organic matter released into rivers, for example,” said Professor Blaszczak. “We can set up these conditions of very low flows. Rivers surrounded by wetlands and urban areas had about the same probability of hypoxia occurrence. That shows that while it can occur naturally, we also can create these conditions that are conducive to hypoxia.”&nbsp;



The widespread, short-term occurrence of hypoxia in rivers across the globe was concerning to the researchers. Not only does low oxygen concentration threaten the lives of aquatic organisms, but it also stimulates the release of methane and nitrous oxide, both of them greenhouse gases that contribute to global warming and climate change.&nbsp;



“There’s just nothing good about hypoxia in rivers or other bodies of water,” said Professor Blaszczak. “We can’t eliminate it completely, but we can certainly do a better job of monitoring it and take actions to prevent it, rather than to stimulate it.”



The dataset on river and stream hypoxia across the globe will help researchers to monitor the changes in future. Blaszczak says that, looking at data from 1950 to 2018, there does not seem to have been an overall global increase in hypoxic conditions in rivers. This is a positive finding, even though there are some locations, such as in the U.S. state of Florida, where the presence of hypoxia has become far more extreme.&nbsp;



She embarked on leading the study after attending a workshop in September 2018, held in Switzerland and convened by Jim Heffernan and Tom Battin from Duke University. The workshop aimed to advance the global understanding of the dynamics of hypoxia in rivers and streams and was supported by the Swiss National Science Foundation and the U.S. National Science Foundation.



Professor Blaszczak suggests that more monitoring with the newer technology is key to mitigating the harmful effects of hypoxia in rivers in future.



“We need to further develop our capacity to identify when and where rivers are vulnerable to the development of hypoxic conditions, so that we can guide river management in the face of continuing climate and land-use change. Supporting ongoing monitoring and expanding monitoring to regions where data is sparse is essential."



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By <a href="mailto:bosman@truewan.co.za">Alison Bosman</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Staff Writer



Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.

Hypoxia is a serious problem in rivers worldwide

Living organisms need oxygen in order to respire, which involves...

Researchers at <a href="https://duke.edu/">Duke University</a> have discovered that glassfrogs make themselves transparent by hiding most of their red blood cells in their liver. According to the experts, this strategy allows the frogs to attain transparency when they are the most vulnerable.



"There are more than 150 species of known glassfrogs in the world, and yet we’re really just starting to learn about some of the really incredible ways they interact with their environment," said study co-lead author Jesse Delia.



"Transparency in animals is a complex form of camouflage involving mechanisms that reduce light scattering and absorption throughout the organism," wrote the study authors.



"In vertebrates, attaining transparency is difficult because their circulatory system is full of red blood cells (RBCs) that strongly attenuate light. Here, we document how glassfrogs overcome this challenge by concealing these cells from view."



The northern glassfrog Hyalinobatrachium fleischmanni is only a few centimeters in length and is most active at night, when the frogs are better able to blend with the surrounding landscape. During the day, glassfrogs become transparent to protect themselves while they sleep.



“When glassfrogs are resting, their muscles and skin become transparent, and their bones, eyes and internal organs are all that’s visible,” said study co-first author Carlos Taboada. “These frogs sleep on the bottoms of large leaves, and when they’re transparent, they can perfectly match the colors of the vegetation.”



The researchers explained that in vertebrates, attaining transparency is difficult because their circulatory system is full of red blood cells that strongly attenuate light. Glassfrogs are some of the only terrestrial vertebrates that can achieve transparency.&nbsp;



“If these frogs are awake, stressed or under anesthesia their circulatory system is full of red blood cells and they are opaque,” explained Delia. “The only way to study transparency is if these animals are happily asleep, which is difficult to achieve in a research lab. We were really banging our heads against the wall for a solution.”



"Using photoacoustic imaging to track RBCs in vivo, we show that resting glassfrogs increase transparency two- to threefold by removing ~89% of their RBCs from circulation and packing them within their liver," wrote the study authors.



Photoacoustic microscopy (PAM) involves shooting a safe laser beam of light into tissue, which is converted into sound waves to create biomedical images of the molecules.&nbsp;



“PAM is the ideal tool for non-invasive imaging of red blood cells because you don’t need to inject contrast agents, which would be very difficult for these frogs,” explained Professor Junjie Yao.&nbsp;



“The red blood cells themselves provide the contrast, because different types of cells absorb and reflect different wavelengths of light. We could optimize our imaging systems to specifically look for red blood cells and track how much oxygen was circulating in the frog’s bodies.”



“The primary result is that whenever glassfrogs want to be transparent, which is typically when they're at rest and vulnerable to predation, they filter nearly all the red blood cells out of their blood and hide them in a mirror-coated liver - somehow avoiding creating a huge blood clot in the process,” said study co-author Sönke Johnsen. “Whenever the frogs need to become active again, they bring the cells back into the blood stream, which gives them the metabolic capacity to move around.”



The researchers said that this process raises questions about how the frogs can safely store almost all their red blood cells in their liver without clotting or damaging their peripheral tissues. They noted that one potential next step is to study this mechanism and how it could one day apply to vascular issues in humans.&nbsp;



“Our successful collaboration has been a great example of how multiple disciplines can jointly advance science in the most synergistic way,” said Professor Yao. “We are extremely excited about the future interactions between the biology and engineering teams. With all the strength on board, the sky is the limit.”



The study is published in the journal <a href="https://www.science.org/doi/10.1126/science.abl6620">Science</a>.



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By <a href="mailto:csexton@earth.com">Chrissy Sexton</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Editor



Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.

Glassfrogs achieve transparency by hiding their red blood cells

Researchers at Duke University have discovered that glassfrogs make themselves...

On an uninhabited island in Alaska, scientists have discovered that wolves are preying on sea otters after nearly wiping out the local deer population. Researchers from <a href="https://oregonstate.edu/">Oregon State University</a> and the Alaska Department of Fish and Game believe this is the first case of <a href="https://www.earth.com/news/sea-otters-have-a-secret-ability-to-generate-heat/">sea otters</a> becoming the primary food source for a land-based predator.



"Sea otters (Enhydra lutris) and wolves (Canis lupus) are two apex predators with strong and cascading effects on ecosystem structure and function. After decades of recovery from near extirpation, their ranges now overlap, allowing sea otters and wolves to interact for the first time in the scientific record," wrote the study authors.&nbsp;



The research was focused on Pleasant Island, which is located near Glacier Bay about 40 miles west of Juneau. In this region, sea otters were wiped out from fur trade hunting in the 1800s and 1900s.&nbsp;



Sea otters are now legally protected under the Marine Mammal Protection Act (MMPA). They were reintroduced to the Pleasant Island area in the 2000s, and wolves were introduced in 2013.



"After wolf colonization, we quantified shifts in foraging behavior with DNA metabarcoding of 689 wolf scats and stable isotope analyses, both revealing a dietary switch from Sitka black-tailed deer (Odocoileus hemionus), the terrestrial in situ primary prey, to sea otters," wrote the study authors.



"Here we show an unexpected result of the reintroduction and restoration of sea otters, which became an abundant marine subsidy for wolves following population recovery. The availability of sea otters allowed wolves to persist and continue to reproduce, subsequently nearly eliminating deer."



The researchers determined that in 2015, deer made up 75 percent of the wolves' diet, while sea otters made up 25 percent. By 2017, the wolves were primarily feeding on sea otters, while deer made up only seven percent of their diet. This pattern continued through the end of the study period in 2020.



“Sea otters are this famous predator in the near-shore ecosystem and wolves are one of the most famous apex predators in terrestrial systems,” said study co-author Professor Taal Levi. “So, it’s pretty surprising that sea otters have become the most important resource feeding wolves. You have top predators feeding on a top predator.”



“The thing that really surprised me is that sea otters became the main prey of wolves on this island,” said study co-author Gretchen Roffler. “Occasionally eating a sea otter that has washed up on the beach because it died, that is not unusual. But the fact that wolves are eating so many of them indicates it has become a widespread behavior pattern throughout this pack and something that they learned how to do very quickly.



“And from the work we are doing investigating kill sites, we are learning that wolves are actively killing the sea otters. So, they aren’t just scavenging sea otters that are dead or dying, they are stalking them and hunting them and killing them and dragging them up onto the land above the high tide line to consume them.”



The study is published in the journal <a href="https://www.pnas.org/">Proceedings of the National Academy of Sciences</a>.



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By <a href="mailto:csexton@earth.com">Chrissy Sexton</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Editor



Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.

Clash of the top predators: wolves are eating sea otters

On an uninhabited island in Alaska, scientists have discovered that...

In a recent study from <a href="https://www.ecu.edu.au/">Edith Cowan University</a>, experts report that the frequency of exercise seems to be much more important than the duration. The research suggests that a little bit of physical activity could be the most beneficial approach to exercise, particularly when it comes to <a href="https://www.earth.com/news/how-hibernating-bears-could-help-humans-prevent-muscle-loss/">muscle</a> strength.



In collaboration with experts at Niigata University and Nishi Kyushu University, the researchers designed a four-week training study in which three groups of participants performed an arm resistance exercise. The experts measured changes in muscle strength and muscle thickness, which is an indicator of muscle size.



The exercise consisted of "maximal voluntary eccentric bicep contractions." During these contractions, muscles were lengthened as the participants lowered a heavy dumbbell in a bicep curl.



Two groups were asked to perform 30 contractions per week - with one group doing six contractions a day, five days a week (6x5 group). The third group performed 30 contractions in a single day, once a week (30x1 group).&nbsp;



In addition, a control group performed six contractions one day per week. After four weeks, the control group did not show any changes in muscle strength or muscle thickness.



Individuals who were assigned to complete 30 contractions on a single day did not show any increase in muscle strength. The thickness of their muscles, however, increased by 5.8 percent.



Meanwhile, the 6x5 group saw increases in muscle strength of more than 10 percent, with a similar improvement in muscle thickness as the 30x1 group.&nbsp;



According to Professor Ken Nosaka, the study suggests that very manageable amounts of exercise- done regularly - can have a real effect on people’s strength. “People think they have to do a lengthy session of resistance training in the gym, but that’s not the case. Just lowering a heavy dumbbell slowly once or six times a day is enough.”



Professor Nosaka noted that while the study required participants to exert maximum effort, early findings from current, ongoing research indicated similar results could be achieved without needing to push as hard as possible.



“We only used the bicep curl exercise in this study, but we believe this would be the case for other muscles also, at least to some extent. Muscle strength is important to our health. This could help prevent a decrease in muscle mass and strength with aging," said Professor Nosaka.



“A decrease in muscle mass is a cause of many chronic disease such as cardiovascular disease, type 2 diabetes, some cancers, dementia, plus musculoskeletal problems such as osteoporosis.”



While it is not yet clear why resistance exercises with eccentric contractions are more effective in smaller doses, Professor Nosaka said it may relate to how often the brain is asked to make a muscle perform in a particular manner. However, he also emphasized the critical importance of resting muscles throughout training.



“In this study, the 6x5 group had two days off per week. Muscle adaptions occur when we are resting; if someone was able to somehow train 24 hours a day, there would actually be no improvement at all," explained Professor Nosaka.



“Muscles need rest to improve their strength and their muscle mass, but muscles appear to like to be stimulated more frequently.”



Professor Nosaka said there needed to be more emphasis on the importance of making exercise a daily activity, rather than hitting a weekly minute goal.



“If you’re just going to the gym once a week, it’s not as effective as doing a bit of exercise every day at home."&nbsp;



"This research, together with our previous study, suggests the importance of accumulating a small amount of exercise a week, than just spending hours exercising once a week.



“We need to know that every muscle contraction counts, and it’s how regularly you perform them that counts.”



The study is published in the <a href="https://onlinelibrary.wiley.com/journal/16000838">Scandinavian Journal of Medicine and Science in Sports</a>.



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By <a href="mailto:csexton@earth.com">Chrissy Sexton</a>, <a href="https://www.earth.com/staff/">Earth.com</a> Editor



Check us out on <a href="https://www.earth.com/earthsnap/">EarthSnap</a>, a free app brought to you by Eric Ralls and Earth.com.

It's not how much, but how often we exercise that counts

In a recent study from Edith Cowan University, experts report...