The Last of Us, one of the most HBO hit shows just got it’s Season 1 finale. The show is based on a popular video game franchise, features a parasitic fungus that turns its host into a zombie-like creature. The fungus, known as Cordyceps, has become a popular topic of discussion among gamers and science enthusiasts alike. While the depiction of Cordyceps in The Last of Us may seem far-fetched, the fungus is actually real and has some fascinating properties.
Cordyceps is a type of parasitic fungus that infects insects and arthropods, such as ants and caterpillars. The fungus invades the host’s body and eventually takes over, manipulating the host’s behavior to its advantage. In some cases, the fungus will cause the host to climb to a high location, where it will spread its spores and infect other nearby hosts.
This behavior is what inspired the depiction of Cordyceps in The Last of Us, where the fungus infects humans and turns them into aggressive creatures.
Cordyceps is a type of parasitic fungus that infects insects and arthropods, such as ants and caterpillars. The fungus invades the host’s body and eventually takes over, manipulating the host’s behavior to its advantage. In some cases, the fungus will cause the host to climb to a high location, where it will spread its spores and infect other nearby hosts. This behavior is what inspired the depiction of Cordyceps in The Last of Us, where the fungus infects humans and turns them into aggressive creatures.
While Cordyceps has some fascinating properties, it is not capable of infecting humans in the same way that it infects insects. However, there are some documented cases of humans being infected with Cordyceps, but these cases are extremely rare and typically only occur in people with weakened immune systems.
Despite the fact that Cordyceps cannot infect humans in the same way that it infects insects, the fungus has become popular in traditional medicine and is believed to have numerous health benefits. Cordyceps is commonly used in traditional Chinese medicine as a treatment for a variety of conditions, including fatigue, asthma, and kidney disease.
In addition to its medicinal properties, Cordyceps has also been the subject of scientific research. Scientists have discovered that the fungus contains a variety of bioactive compounds that have the potential to be used in the development of new drugs. Cordyceps has been shown to have anti-inflammatory, antioxidant, and anti-cancer properties, among others.
The depiction of Cordyceps in The Last of Us has sparked interest in the fungus and has brought attention to its unique properties. While the idea of a parasitic fungus infecting humans and turning them into zombies may seem like science fiction, the reality of Cordyceps is equally fascinating. As scientists continue to study the fungus, it is possible that Cordyceps may one day be used to develop new treatments for a variety of medical conditions.
Of course the easiest explanation would be that cats hate water and think you are in danger, but the truth may be a little more complicated than that.
The short truth is that nobody really knows why cats meow at you while you shower, but there are some probable reasons put forth by both professional and amateur researchers.
Cats Are Afraid Of Water
Some people have theorized that cats meow at you when you shower because they think you are in some sort of danger. However, if this is true, it may not be due to the water involved because if they aren’t seeing the water (such as when you have closed the bathroom door), then how would they know about it?
If the meowing is indeed a meow of caution or concern, then it could have nothing to do with water at all and more to do with their general behavior in regards to you, their owner.
Cats and Closed Doors
A concerned meow is usually due to what cats tend to perceive as danger, but after ruling water out, what are we left with? A number of other factors come to mind, especially their notorious separation anxiety. Many cats will follow you around the house, and if yours is one of them then think about the sudden shock of closing a door between you and them.
Cats tend to meow on one side of a door because they hate to be trapped. Think of putting a cat in a bedroom, basement, bathroom, closet, etc, and remember the sound of their cries. Sounds a lot like the same type of meow you hear when you take a shower, doesn’t it?
Showers Make High Pitched Sounds
Cats can hear very high pitched sounds. That’s why they created cat whistles, to get a cat’s attention. So one theory that makes sense is that a shower tends to cause the pipes to make fairly high pitched noises consistently throughout the shower. If you heard an annoying high pitched sound for a long period of time, that might make you go crazy as well!
A number of fake news websites dedicated to spiritual topics, holistic health and conspiracy theories push a fake but somewhat convincing narrative that cats and dogs can see spirits because they can see ultraviolet light
However, there is no data that suggests any animal can see beings made of light, and there’s a really easy way to prove it — with ultraviolet goggles.
The narrative of cats seeing spirits started after popular science sites like Live Science published articles discussing a research paper regarding ultraviolet light in mammals that suggest cats could see ultraviolet light. There’s just one problem: the study which Live Science mentions doesn’t say anything about proof of seeing light beings at all. That didn’t stop sites like The Mind Unleashed and Disclose TV from speculating about seeing spirits and running with it.
The study, published in 2014, concludes that some mammals can see UV light because of the way their lenses are shaped and structured.
We examined lenses of 38 mammalian species from 25 families in nine orders and observed large diversity in the degree of short-wavelength transmission. All species whose lenses removed short wavelengths had retinae specialized for high spatial resolution and relatively high cone numbers, suggesting that UV removal is primarily linked to increased acuity. Other mammals, however, such as hedgehogs, dogs, cats, ferrets and okapis had lenses transmitting significant amounts of UVA (315–400 nm), suggesting that they will be UV-sensitive even without a specific UV visual pigment.
A search through the study, however, does not suggest that it can see ghosts, or even any sort of light beings at all.
The simple truth is that if these UV light empowered mammals could see some sort of beings made of light that humans can’t, then all it would take for a human to confirm the existence of these beings would be to wear UV goggles or capture video with UV cameras. Alas, the fact that this hasn’t happened means these websites are simply pushing an exciting narrative to get you to click and make them some money.
UV Light In Mammals: The Actual Science
Just because there’s no evidence of cats seeing ghosts doesn’t mean the science isn’t still pretty cool! And it doesn’t mean cats don’t see things that we can’t. At least in terms of how much of a light range from the electromagnetic spectrum they can see versus that of humans, the research suggests that some mammals can in fact see UV light, which allows them to “see in the dark” despite having some trouble seeing in brighter daylight the way humans can.
As one paper from biologists R. H. Douglas and G. Jeffery at the Royal Society of Biological sciences says, although ultraviolet sensitivity is widespread among the animal kingdom, it is still considered very rare in mammals, being restricted to just a few species which have a visual pigment maximally sensitive below 400 nanometers. However, it also says that even animals without such a pigment will be UV-sensitive if they have ocular media that transmit these wavelengths, as all visual pigments absorb significant amounts of ultraviolet light if the energy level is sufficient enough to allow it.
The researchers also showed us that hooded seals native to the Arctic Ocean and North Atlantic have eyes that are extremely sensitive to ultraviolet light. This allows the seals to actually spot polar bears hiding in the snow as UV is reflected by snow and ice but absorbed by the bears’ white fur.
It’s remarkable how little we know about Earth. How many species do we share this planet with? We don’t know, but estimates vary from millions to a trillion. In some respects we know more about the Moon, Mars and Venus than we do about the ocean’s depths and the vast sea floors.
But humans are inquisitive creatures, and we’re driven to explore. Chasing mythical or mysterious animals grabs media headlines and spurs debates, but it can also lead to remarkable discoveries.
The recent photographing of a live night parrot in Western Australia brought much joy. These enigmatic nocturnal birds have been only sporadically sighted over decades.
Another Australian species that inspires dedicated searchers is the Tasmanian tiger, or thylacine. A new hunt is under way, not in Tasmania but in Queensland’s vast wilderness region of Cape York.
This is the first photograph of a live night parrot, taken in Western Australia in March 2017. Bruce Greatwitch
Other plans are afoot to search for the long-beaked echidna in Western Australia’s Kimberley region.
In the case of the thylacine, old accounts from the region that sound very much like descriptions of the species raise the prospect that perhaps Cape York isn’t such a bad place to look after all.
But in reality, and tragically, it’s very unlikely that either of these species still survives in Australia. For some species there is scientific research that estimates just how improbable such an event would be; in the case of thylacines, one model suggests the odds are 1 in 1.6 trillion.
Chasing myths
The study and pursuit of “hidden” animals, thought to be extinct or fictitious, is often called cryptozoology. The word itself invites scorn – notorious examples include the search for Bigfoot, the Loch Ness Monster or Victoria’s legendary black panthers.
The search for Bigfoot is an extreme case of cryptozoology.
Granted, it’s probably apt to describe those searches as wild goose chases, but we must also acknowledge that genuine species – often quite sizeable ones – have been discovered.
In some cases, like the giant squid, these animals have been dismissed as legends. The reclusive oarfish, for example, are thought to be the inspiration for centuries of stories about sea serpents.
Oarfish can grow up to 8 metres long and swim vertically through the water. Commonly inhabiting the deep ocean, they occasionally come to shallow water for unknown reasons. AAP Image/ Coastal Otago District Office
Technology to the rescue
Finding rare and cryptic species is self-evidently challenging, but rapid advances in technology open up amazing possibilities. Camera traps now provide us with regular selfies of once highly elusive snow leopards, and could equally be used with other difficult-to-find animals.
Candid camera, snow leopards in the Himalayas.
Environmental DNA is allowing us to detect species otherwise difficult to observe. Animal DNA found in the blood of leeches has uncovered rare and endangered mammals, meaning these and other much maligned blood-sucking parasites could be powerful biodiversity survey tools.
Acoustic recording devices can be left in areas for extended time periods, allowing us to eavesdrop on ecosystems and look out for sounds that might indicate otherwise hidden biological treasures. And coupling drones with thermal sensors and high resolution cameras means we can now take an eagle eye to remote and challenging environments.
Drones are opening up amazing possibilities for biological survey and wildlife conservation.
The benefits of exploration and lessons learned
It’s easy to criticise the pursuit of the unlikely, but “miracles” can and do occur, sometimes on our doorstep. The discovery of the ancient Wollemi pine is a case in point. Even if we don’t find what we’re after, we may still benefit from what we learn along the way.
I’ve often wondered how many more species might be revealed to us if scientists invested more time in carefully listening to, recording and following up on the knowledge of Indigenous, farming, and other communities who have long and intimate associations with the land and sea.
Such an approach, combined with the deployment of new technologies, could create a boom of biological discovery.
Euan Ritchie, Senior Lecturer in Ecology, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University
Insects navigate in much the same way that ancient humans did: using the sky. Their primary cue is the position of the sun, but insects can also detect properties of skylight (the blue light scattered by the upper atmosphere) that give them indirect information about the sun’s position. Skylight cues include gradients in brightness and colour across the sky and the way light is polarised by the atmosphere. Together, these sky “compass cues” allow many insect species to hold a stable course.
At night, as visual cues become harder to detect, this process becomes more challenging. Some can use the light of the moon but one insect, the nocturnal dung beetle Scarabaeus satyrus, uses light from the Milky Way to orient itself. To find out exactly how this process works, my colleagues and I constructed an artificial Milky Way, using LEDs, to test the beetles’ abilities. We found that they rely on the difference in brightness between different parts of the Milky Way to work out which way to go.
Scarabaeus satyrus holds its course with apparent ease every night. They take to the air at dusk in the African Savanna, in search of the fresh animal droppings on which they feed. But they are not alone and, to escape competition from other dung beetles, they construct a piece of dung into a ball and roll it a few meters away from the dung pile before burying and consuming it.
Where am I supposed to take this thing? Shutterstock
To avoid returning to their starting point, they maintain a straight path while rolling their ball. Scientists discovered that the beetles could do this even on moonless clear nights. So in 2009, a group of researchers took some beetles on a trip to the planetarium in Johannesburg, and watched them try to orient themselves under different star patterns.
They found the beetles could hold their course well when the planetarium displayed just the Milky Way, the streak of light across the night sky produced by the disc-shaped arrangement of the stars in our galaxy. But the beetles became disoriented when only the brightest stars in the sky were shown.
What was still unclear was exactly what kind of compass cue the beetles extracted from the Milky Way. We knew, for example, that night-migrating birds learn the constellations surrounding the sky’s northern centre of rotation, much as sailors did before the advent of modern navigation systems. These constellations remain in the northern part of the sky as the Earth rotates, and so are a reliable reference for north–south journeys.
The planetarium experiments had shown that the beetles don’t use constellations of bright stars, but perhaps they could learn patterns within the Milky Way instead. My colleagues and I then proposed that the beetles might perform a brightness comparison, identifying either the brightest point in the Milky Way or a brightness gradient across the sky that is influenced by the Milky Way.
Artificial Milky Way
We used our artificial night sky to test this theory, constructing a simplified Milky Way streak that simulated different patterns of stars and brightness gradients. We found that the beetles became lost when given a pattern of stars within the artificial Milky Way. The beetles only maintained their heading when the two sides of the steak differed in brightness.
This suggests nocturnal beetles do not use the intricate star patterns within the Milky Way as their compass cue, but instead identify a brightness difference across the night sky to set their heading. This is similar to what their day-active relatives do when the sun is not visible but instead orient themselves using the brightness gradient of the daytime sky.
Night-time compass. Shutterstock
This brightness-comparison strategy may be less sophisticated than the way birds and human sailors identify specific constellations, but it’s an efficient solution to interpreting the complex information present in the starry sky—given how small the beetles’ eyes and brains are. In this way, they overcome the limited bandwidth of their information processing systems and do more with less, just as humans have learnt to do with technology.
This straightforward brightness comparison strategy is particularly effective over short distances. So although Scarabaeus satyrus is the only species known to hold its course in this way, the technique may also be used by many other nocturnal animals that perform short journeys at night.
This controversial move was welcomed by commercial rhino breeders, who argue that legalising safe, sustainable horn removal from living animals could prevent wild rhino poaching. But animal preservation groups have warned that any legal trade would have the opposite effect.
Poaching has indeed reached new heights this year. On March 7, a rhinoceros was killed in the Thoiry zoo, near Paris, and its main horn was sawed off and stolen. This is the first time a living rhinoceros in a European zoo has been killed for its horn.
That same week, in South Africa, 13 rhinos were found dead in a single day, decimated by poachers.
Only 62 rhinos were poached across Africa in 2006. The following year this figure shot up to 262 animals, then 1,090 by 2013, 90% of which were killed in South Africa.
Rhinoceros are divided into five separate species. Africa (mainly South Africa, Namibia, Kenya, and Zimbabwe) is home to white rhino (around 20,400 specimens, 18,500 of which are in South Africa) and the black rhino (5,200 specimens, 1,900 of which are in South Africa). As their names indicate, the Indian rhino (3,500 specimens living in India and Nepal), the Sumatran rhino (250 animals) and the Javan rhino (only 50 animals) are found in Asia.
Depending on its age and species, an adult rhinoceros can have up to a few kilograms worth of horn, the white rhino being the best endowed (up to 6kgs). Indian and Javan rhinos have only one horn, while the other three species have two.
In 2015, a total of 1,342 white and black rhinos were poached across the continent. Over the last few years, as many (or more) rhinoceros have been killed in South Africa than are naturally born in Kruger National Park and on private farms put together.
Bogus medicinal properties
Rhino horn, highly valued in China and Vietnam, is used in traditional Asian medicine to treat fevers and cardiovascular disease. More recently, it has been prescribed as a cancer treatment and an aphrodisiac.
While there is no scientific evidence for such medicinal properties, these unfounded beliefs are feeding soaring Asian demand for powdered rhino horn. Prices are skyrocketing: up to US$60,000 a kilo, which is more expensive than gold.
In truth, rhino horn is simply a formation of keratin, a protein found in human nails and animal claws, with a few amino acids and minerals, phosphorus and calcium.
Controlling a lucrative criminal market
Criminal trade in wild animals constitutes one of the world’s largest illegal markets, according to the UN, along with drugs, counterfeit products and human trafficking. Each year, it affects tens of millions of specimens of animals and plants.
With support from Interpol, Europol, the World Customs Organisation and the United Nations Office on Drugs and Crime (UNODC), CITES applies the ban on rhinoceros-horn trading. Using a system of permits and certificates delivered under special conditions, CITES regulates the market for rhinos and about 35,000 other wild species, categorised into three groups according to the level of protection required.
The white rhino, which is not necessarily threatened with extinction, is an appendix species II for South Africa and Swaziland, meaning the trade there must be controlled in order not to jeopardise the animal’s survival. For all other African range states, the white rhino is listed on appendix I: all trade of this endangered species is forbidden, except for non-commercial purposes such as scientific research.
Appendix III contains species that are protected in at least one country, which has sought assistance in controlling their trade.
Prior to the 2000s, and up until 2007, pressure on consumer countries (Yemen, Korea, Taiwan and China) to stop the rhino trade helped reduce poaching activity, leading to an increase in the African rhino population.
But demand for rhino horn surged in the mid-2000s, chiefly in Vietnam, because of rumours that a government official suffering from cancer went into remission after its use.
Likewise, there is still demand in China and Hong Kong for wealth-signaling objects made of rhino horn, such as libation cups and jewellery.
Where, then, do all these horns come from? According to UNODC, today the major shipments of rhino horn originate primarily in South Africa, followed by Mozambique (where rhinos are gone, but poachers have dipped into stocks at South Africa’s Kruger National Park), Zimbabwe and Kenya.
Both the United Arab Emirates and Europe have served as trading routes. In 2011, the Czech government discovered that some of its citizens were selling trophies they had hunted in South Africa to Vietnamese traders. Some 90 rhino horns were also stolen from museums and auction houses across Europe between January 2011 and June 2012 by the Irish Rathkeale Rovers, a gang since dismantled by Europol.
The import of trophies
Though the international rhino horn trade has been forbidden since 1977, CITES recognises some exceptions. It allows, for instance, limited hunting of Appendix II and I species, including, under exceptional circumstances, of endangered white and black rhinoceros
This allowance recognises that well-managed and sustainable hunting is actually consistent with and contributes to conservation efforts. It provides both livelihood opportunities for rural communities and incentives for habitat conservation. And it generates benefits that can be invested in conservation.
It also demonstrates that effective conservation, management and monitoring plans and programs are in place in a number of African range states, meaning that some populations are recovering enough to sustain limited off-takes as trophies.
Though bringing these rhinoceros-hunting trophies (including horns) hunted in South Africa home as personal property is authorised by CITES, their sale is not. Trophies may then be exported to certain African countries under specific conditions (a non-detriment finding by the exporting country is required beforehand).
Rhino horns are sought after for social status and medicine, and even trophies are hunted down. Wikilmages/Pixabay
Between 2006 and 2011, 1,344 hunting trophies, including African rhino horns from both species [were legally exported](https://cites.org/sites/default/files/fra/cop/16/prop/F-CoP16-Prop-10.pdf (page 5) as personal property. They mainly came from South Africa, where just under 75 trophy-hunting expeditions were organised prior to 2006, and to a lesser extent, Namibia. Vietnam was the top importing country, ahead of the US, Spain and Russia.
After a sudden upsurge in requests for hunting permits from Vietnam, where it was discovered that rhino horns had been illegally sold, South African authorities in 2012 put an end to permits for Vietnamese nationals.
Opening the market?
As demonstrated in last week’s South African court case overturning the ban on the rhino trade, some countries are showing signs of restlessness under the current CITES regime.
Swaziland, for instance, would also like to see change. During the last international meeting of CITES signatory parties in late September 2016, this small country submitted a proposal to allow limited regulated trade in white rhino horn. It has a small population of about 75 white rhinos living protected in parks.
Between 1988 and 1992, an intense period of poaching wiped out 80% of Swaziland’s rhino population. This left it with a large stock of horns that it would like to be able to sell. The proposition was voted down by the majority of CITES countries.
Now, South Africa’s legal U-turn could open a new avenues for the rhino trade. Most South African farmers believe that the ban only encourages poaching and that they themselves could fulfil Asian demand by providing horns from living animals.
Farmers know how to cut the horn with a saw so that it will grow back, a painless procedure for the animal that is put under anaesthetic for around 15 minutes. Protecting rhinos on ranches costs them millions of dollars as they face raids from poachers.
The current poaching crisis differs from a prior crisis in the 1990s in two ways. First, the illegal rhino horn trade has been taken over by organised crime groups because it is less severely punished than other illegal trades (although this is changing thanks to new legislation introduced in most countries).
Then there’s the skyrocketing traffic to East Asia, which reveals the region’s ever-growing demand of miscellaneous African animal products for traditional Asian medicine, from rhino horns to elephant ivory and, now, the skin of domestic African donkeys
What can be done?
Conservation groups should remain resolute at this critical juncture.
National, regional and sub-regional networks have intensified their fight against this transnational criminal market and are now being coordinated by the International Consortium on Combating Wildlife Crim, which brings together CITES with various anti-fraud organisations. Thus far, their battle has produced very good results.
It is now up to Asian authorities to raise awareness and discourage the use of rhino horn. China has already taken steps in this direction and, in November 2016, Vietnamese authorities burnt a stock of rhino horn.
Still, some say it will take a generation to change attitudes. Can the planet’s remaining 30,000 rhinoceros survive until then?
Translated from the French by Alice Heathwood for Fast for Word.
When you think about typical African wildlife, a few animals almost certainly spring to mind: zebras, wildebeest, lions, cheetahs and buffaloes. But fossil records tell us that these species aren’t originally from Africa.
In fact, their ancestors originated in Asia when Africa was separated from the rest of the world by sea, between 40 and 50 million years ago. Members of the “Big Five” and other animals most of us consider thoroughly African only arrived on the continent after the formation of a land bridge in the Levant (a section of the ancient Eastern Mediterranean) with Asia around 30 million years ago.
Before that, a very different group of mammals – the Afrotheria or “African beasts” – lived on the continent. This superorder, or clade, consists of several creatures you’d recognise today. Among them are dassies (rock hyrax), sea cows, golden moles, sengis (elephant shrews) and aardvarks.
Afrotheria: a family tree full of very different-looking relatives. Esculapio/Wikimedia Commons
These animals are all related to elephants; though they look very different externally, inside they share unique DNA signatures inherited from a common ancestor born more than 60 million years ago on African soil. Most are still endemic to the continent.
The ancestral line of all these creatures is deeply rooted in Africa, except for the sea cows which was a mystery for a very long time. Their genes confirm that they’re Afrotherians. So one would expect them to have their evolutionary origin in Africa, but the oldest fossils ever recorded were actually found in Jamaica, on the opposite shore of the Atlantic Ocean. One set of fossils was found in 1855; a second in 2001. These belonged to the four legged Prorastomidae, a family of primitive, amphibious sea cows which looked like hippos.
This discrepancy suggested that sea cows’ ancient ancestors weren’t African, which is paradoxical for representatives of the Afrotherians. But thanks to two more recent fossil discoveries, one in Senegal and one in Tunisia, my colleagues and I at the University of Montpellier in France were able to solve this mystery. Sea cows are quintessentially African. Here’s how we found out.
A deep dive into geological time
Decades of collaborations between palaeontologists from the University of Montpellier and various African countries has resulted in the university having a vast collection of beautiful fossils. By 2013, most of these had already yielded their secrets – but two were still puzzling the experts.
One was a vertebra found during a dig in Senegal. The other was a piece of ear bone found in Tunisia. After hours of anatomical comparisons and endless discussions with specialists all around the world, we finally managed to prove that these remains belonged to the earliest known sirenians – the family to which sea cows belong.
A curious sea cow. Alex Churilov/Shutterstock
The vertebra was nearly identical to those found in Jamaica. The piece of ear bone was a little older (dating back 48 million years) and looked more primitive than those of the Jamaican species. These evidence suggest that sea cows existed and were already widespread in Africa well before their descendants crossed the ocean and reached the New World. Both ancient Jamaican and African sea cows had four legs and lived on land. Like ancient Cetaceans – whales, dolphins and porpoises – sea cows started as terrestrial animals and later evolved into aquatic mammals.
A live heritage
Now we can confidently say that sea cows are truly 100% African mammals. They’re in good, if limited company: there are fewer than 100 extant Afrotherian species but they represent a sixth of overall mammalian genetic diversity.
Mammals are divided into six big clusters called clades. One clade represents all living species descended from a single common ancestor – so, if we could come back in the past, we would see all the lineages of existing mammals coming down to only six remote ancestors.
When geneticists discovered that the very different animals who make up the Afrotherian clade were related, they also realised that Afrotheria were becoming increasingly rare. Most went extinct after they were out-competed by the arrival of Asian species in Africa 30 million years ago.
Confirming that sea cows are Afrotherians means the clade is more diverse than we thought, and adds to an understanding of its evolutionary history. That, in turn, helps us understand its current standing and even examine scenarios for its future conservation.
Ocean life is largely hidden from view. Monitoring what lives where is costly – typically requiring big boats, big nets, skilled personnel and plenty of time. An emerging technology using what’s called environmental DNA gets around some of those limitations, providing a quick, affordable way to figure out what’s present beneath the water’s surface.
Fish and other animals shed DNA into the water, in the form of cells, secretions or excreta. About 10 years ago, researchers in Europe first demonstrated that small volumes of pond water contained enough free-floating DNA to detect resident animals.
Researchers have subsequentlylooked foraquatic eDNAin multiplefreshwater systems, and more recently in vastly larger and more complexmarineenvironments. While the principle of aquatic eDNA is well-established, we’re just beginning to explore its potential for detecting fish and their abundance in particular marine settings. The technology promises many practical and scientific applications, from helping set sustainable fish quotas and evaluating protections for endangered species to assessing the impacts of offshore wind farms.
Who’s in the Hudson, when?
In our new study, my colleagues and I tested how well aquatic eDNA could detect fish in the Hudson River estuary surrounding New York City. Despite being the most heavily urbanized estuary in North America, water quality has improved dramatically over the past decades, and the estuary has partly recovered its role as essential habitat for many fish species. The improved health of local waters is highlighted by the now regular fall appearance of humpback whales feeding on large schools of Atlantic menhaden at the borders of New York harbor, within site of the Empire State Building.
Preparing to hurl the collecting bucket into the river. Mark Stoeckle, CC BY-ND
Our study is the first recording of spring migration of ocean fish by conducting DNA tests on water samples. We collected one liter (about a quart) water samples weekly at two city sites from January to July 2016. Because the Manhattan shoreline is armored and elevated, we tossed a bucket on a rope into the water. Wintertime samples had little or no fish eDNA. Beginning in April there was a steady increase in fish detected, with about 10 to 15 species per sample by early summer. The eDNA findings largely matched our existing knowledge of fish movements, hard won from decades of traditional seining surveys.
Our results demonstrate the “Goldilocks” quality of aquatic eDNA – it seems to last just the right amount of time to be useful. If it disappeared too quickly, we wouldn’t be able to detect it. If it lasted for too long, we wouldn’t detect seasonal differences and would likely find DNAs of many freshwater and open ocean species as well as those of local estuary fish. Research suggests DNA decays over hours to days, depending on temperature, currents and so on.
Fish identified via eDNA in one day’s sample from New York City’s East River. New York State Department of Environmental Conservation: alewife (herring species), striped bass, American eel, mummichog; Massachusetts Department of Fish and Game: black sea bass, bluefish, Atlantic silverside; New Jersey Scuba Diving Association: oyster toadfish; Diane Rome Peeples: Atlantic menhaden, Tautog, Bay anchovy; H. Gervais: conger eel., CC BY-ND
Altogether, we obtained eDNAs matching 42 local marine fish species, including most (80 percent) of the locally abundant or common species. In addition, of species that we detected, abundant or common species were more frequently observed than were locally uncommon ones. That the species eDNA detected matched traditional observations of locally common fish in terms of abundance is good news for the method – it supports eDNA as an index of fish numbers. We expect we’ll eventually be able to detect all local species – by collecting larger volumes, at additional sites in the estuary and at different depths.
In addition to local marine species, we also found locally rare or absent species in a few samples. Most were fish we eat – Nile tilapia, Atlantic salmon, European sea bass (“branzino”). We speculate these came from wastewater – even though the Hudson is cleaner, sewage contamination persists. If that is how the DNA got into the estuary in this case, then it might be possible to determine if a community is consuming protected species by testing its wastewater. The remaining exotics we found were freshwater species, surprisingly few given the large, daily freshwater inflows into the saltwater estuary from the Hudson watershed.
Filtering the estuary water back in the lab. Mark Stoeckle, CC BY-ND
Analyzing the naked DNA
Our protocol uses methods and equipment standard in a molecular biology laboratory, and follows the same procedures used to analyze human microbiomes, for example.
eDNA and other debris left on the filter after the estuary water passed through. Mark Stoeckle, CC BY-ND
After collection, we run water samples through a small pore size (0.45 micron) filter that traps suspended material, including cells and cell fragments. We extract DNA from the filter, and amplify it using polymerase chain reaction (PCR). PCR is like “xeroxing” a particular DNA sequence, producing enough copies so that it can easily be analyzed.
We targeted mitochondrial DNA – the genetic material within the mitochondria, the organelle that generates the cell’s energy. Mitochondrial DNA is present in much higher concentrations than nuclear DNA, and so easier to detect. It also has regions that are the same in all vertebrates, which makes it easier for us to amplify multiple species.
We tagged each amplified sample, pooled the samples and sent them for next-generation sequencing. Rockefeller University scientist and co-author Zachary Charlop-Powers created the bioinformatic pipeline that assesses sequence quality and generates a list of the unique sequences and “read numbers” in each sample. That’s how many times we detected each unique sequence.
To identify species, each unique sequence is compared to those in the public database GenBank. Our results are consistent with read number being proportional to fish numbers, but more work is needed on the precise relationship of eDNA and fish abundance. For example, some fish may shed more DNA than others. The effects of fish mortality, water temperature, eggs and larval fish versus adult forms could also be at play.
Just like in television crime shows, eDNA identification relies on a comprehensive and accurate database. In a pilot study, we identified local species that were missing from the GenBank database, or had incomplete or mismatched sequences. To improve identifications, we sequenced 31 specimens representing 18 species from scientific collections at Monmouth University, and from bait stores and fish markets. This work was largely done by student researcher and co-author Lyubov Soboleva, a senior at John Bowne High School in New York City. We deposited these new sequences in GenBank, boosting the database’s coverage to about 80 percent of our local species.
Study’s collection sites in Manhattan. Mark Stoeckle, CC BY-ND
We focused on fish and other vertebrates. Other research groups have applied an aquatic eDNA approach to invertebrates. In principle, the technique could assess the diversity of all animal, plant and microbial life in a particular habitat. In addition to detecting aquatic animals, eDNA reflects terrestrial animals in nearby watersheds. In our study, the commonest wild animal detected in New York City waters was the brown rat, a common urban denizen.
Future studies might employ autonomous vehicles to routinely sample remote and deep sites, helping us to better understand and manage the diversity of ocean life.
Myths about diseases spread like wildfire. Malaria is a case in point. The Conversation Africa’s Health and Medicine Editor Joy Wanja Muraya asked Tabitha Mwangi to help sort out fact from fiction.
Mosquitoes only bite at night.
Not entirely true.
There are two types of mosquitoes that bite mostly at night; the Anopheles mosquito that transmits malaria and it’s noisier cousin, the Culex mosquito which spreads lymphatic filariasis, – also known as elephantiasis – that presents as severe swelling in the arms, legs or genitals.
A year-long study in Western Kenya showed that 15% of the mosquitoes bite between 6pm to 9pm while the majority (85%) bite from 9pm till morning. Data from this study puts further emphasis on the value of sleeping under an insecticide treated bednet.
But there are other mosquitoes, such as the Aedes mosquitoes – easily identified by their zebra stripped legs – that are active mostly during the day. They spread viruses that cause dengue, zika, Chikugunya and rift valley fever.
The fact that this mosquito is active during the day makes it harder to control the diseases it spreads because bed nets aren’t an option.
Eating garlic before I sleep will repel mosquitoes.
There’s no scientific evidence to support this.
Garlic does produce a sulphur compound known as allicin which has some anti-bacterial, anti-fungal and anti-parasitic activities. Researchers have looked at it’s impact on mice that have been infected with malaria. In mice, use of allicin leads to a reduction in the number of malaria parasites in the blood, the higher the dose of allicin, the longer the mice survived. But no research has been done on its effect on the human immune system.
Garlic oils are marketed as insect repellents but their efficacy is uncertain.
Mosquitoes like to bite women and children more than men.
This isn’t true, though there’s some evidence that they’re partial to pregnant women.
In The Gambia researchers found that pregnant women are twice as attractive to mosquitoes than non pregnant women.
The research involved 36 pregnant women and 36 women who weren’t pregnant. The two groups slept in separate huts under bed nets. In the morning, researchers collected and counted the mosquitoes found in the separate huts.
Twice as many mosquitoes were found in the huts in which the pregnant women had slept. There were two possible explanations for this. The first is that mosquitoes are attracted to carbon dioxide which pregnant women produce more of. In advanced pregnancy, women exhale 21% greater volumes than non pregnant women.
The second possible explanation is that pregnant women’s tummies are 0.7°C warmer than non pregnant women which could attract mosquitoes.
But there was an additional factor that the researchers suggested could have affected the results. Pregnant women – particularly women in advanced pregnancy – had to leave their huts at night more often than non-pregnant women because they need to urinate frequently.
Mosquitoes die after feeding.
This is not true. Male mosquitoes feed on sugary things while female mosquitoes need blood for their eggs to develop.
After feeding on blood, a female mosquito will rest to digest the blood and wait for the eggs to be ready.
The female mosquito rests for about two to three days then lays her eggs in water. After laying between 50 to 200 eggs, she then searches for another blood meal in order to lay another batch of eggs.
During her lifetime the female tries to lay as many eggs as she can which requires several blood meals.
In a laboratory, female mosquitoes can live for up to one month. But in natural conditions, few survive beyond one to two weeks.
Once you get malaria, you will never get it again.
Researchers have spent years monitoring people in malaria endemic areas to learn the patterns of immunity.
My PhD research involved collecting data on malaria from about 1,000 people in Coastal Kenya for two years. Children under five years had, on average, one clinical attack of malaria every year.
Malaria cases declined steeply after that and it was rare for adults who lived in this malaria endemic areas to have clinical attacks.
Other studies have shown that when highly immune adults spent long periods of time in places where they weren’t being bitten by infected mosquitoes, they could lose some of thatimmunity.
Scientists know that solid immunity to malaria only occurs in people who are constantly challenged. But it’s still not clear how this happens. This is one of the reasons why developing a malaria vaccine that works well has proved so difficult.
Mosquitoes only like the blood of humans.
This is true for some mosquitoes, but because female mosquitoes need a blood meal, most will take it from wherever they can find it. For example, livestock kept outside the homestead can attract mosquitoes. There’s even been a suggestion that cattle should be treated with insecticide as a malaria control strategy.
Scientists in Argentina have discovered a frog that glows in moonlight and at twilight. Fluorescence in terrestrial environments had previously only been traced to a few species of insects and birds and had never been scientifically reported in any of the world’s 7,000-plus amphibian species.
A team of herpetologists made the headline-grabbing discovery in the outskirts of the city of Santa Fe, Argentina, while collecting frogs to research the biochemical cloricia in amphibians. They sought out the polka-dot tree frog (Hypsiboas punctatus), a species found throughout South America, because its translucent skin allows the accumulation of biliverdin (a blue-green bile pigment) to be seen with the naked eye.
But when they shone a UVA light on the frogs, they did not see the faint red biliverdin emission they had anticipated. Rather, what they saw was a bright and beautiful cyan fluorescence. So luminous were the frogs that under the black light they glowed in the dark, helping the scientists locate specimens. This fluorescence was present in all of the 100-plus polka-dot tree frogs collected.
The polka-dot tree frog’s translucent skin appears to glow because it allows a high level of transmission of light in the green and red parts of the electromagnetic spectrum, while blocking transmission of blue light.
The peculiar cyan fluorescence, which we found originated in its skin glands and lymph nodes, belongs to a family of derivatives of the molecule dihydroisoquinolinone. The compounds were named “hyloins”, after the amphibian family Hylidae, to which the tree frog belongs.
Fluorescence can be an important biosignal for visual communication, helping these frogs locate each other. The perceived brightness depends on several factors: the proportion of photons arising from fluorescence compared to those reflected by the animal; the spectral lighting conditions of the environment where the amphibians live; and the sensitivity of frogs’ eyes to different colours.
In the case of Hypsiboas punctatus, we found that under twilight-nocturnal conditions, between 18% and 30% of all the light (photons) emanating from the frog’s skin were florescent. That’s a substantial proportion, enough to add significant fluorescence to the typical green (in daylight) colouration of the frog, enhancing its visibility.
Finding fluorescence in a land animal is particularly interesting because it has been generally considered irrelevant but for its presence in some insects (spiders, scorpions, beetles, butterflies, moths, dragonflies, millipedes) and in two avian species, parrots and parrotlets. In parrotlets, differences in feather fluorescence between sexes have been found to serve a function in mating and attraction.
With the polka-dot tree frog, we expect that its fluorescence plays a role in inter-species visual communication (because it matches the sensitivity of the frogs’ eyes photoreceptors for blue and green). We do not believe that it has any relevance to mating, as florescence does not seem to differ between females and males.
What else glows?
The discovery of fluorescence in frogs – a species previously unknown to exhibit it – has renewed interest in searching for other glow-in-the-dark amphibians.
Beetles also display fluorescence.
The finding also opens additional avenues for future research. A more detailed study on the spectral sensitivity of the eye photoreceptors of Hypsiboas punctatus, for example, would help us calculate the amount of light reaching each of the polka-dot tree frog’s photoreceptors and better understand the species’ visual perception.
We are also interested in evaluating the photophysical properties of the purified free fluorophores found in this study, including their chemical and biochemical makeup. They could potentially be used as fluorescent markers or labels in molecular biology or biotechnology, allowing microscopic detection of biomolecules.
Finally, this discovery has given scientists a strong hint for the answer to an important question in biophotophysical research: does naturally occurring fluorescence act as a biosignal, or is it simply a non-functional outcome of certain pigments’ chemical structure?
The polka-dot tree frog’s moonlight glow suggests strongly that, yes, fluorescence matters.
Scientists involved in this work were: Carlos Taboada (Bernardino Rivadavia Argentina Museum of Natural Sciences-CONICET and the University of Buenos Aires, INQUIMAE-CONICET); Andrés E. Brunetti (Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo); Federico N. Pedron (University of Buenos Aires, INQUIMAE-CONICET and the Department of Inorganic, Analytic and Physical Chemical Chemistry, FCEN); Fausto Carnevale Neto (Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo); Darío A. Estrin (University of Buenos Aires, INQUIMAE-CONICET and the Department of Inorganic, Analytic and Physical Chemical Chemistry, FCEN); Sara E. Bari (University of Buenos Aires, INQUIMAE-CONICET); Lucía B. Chemes (Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas de Buenos Aires-CONICET); Norberto Peporine Lopes (Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo); María G. Lagorio (University of Buenos Aires, INQUIMAE-CONICET and the Department of Inorganic, Analytic and Physical Chemical Chemistry, FCEN); and Julián Faivovich (Bernardino Rivadavia Argentina Museum of Natural Sciences-CONICET and University of Buenos Aires Department of Biodiversity and Biologial Experimentation, FCEN).
