Found 19 Resources containing: Invertebrates-Physiology
Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons, in 1843 / by Richard Owen ; from notes taken by William White Cooper ; and revised by Professor Owen ; illustrated by numerous woodcuts
"London : Printed by A. Spottiswoode"--Verso of half-title.
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SCNHRB has two copies, both in original purple publisher's cloth binding, blind-embossed decorations, title in gilt on spine, yellow endpapers.
SCNHRB copy 1 (39088000956573) has 16-page publisher's catalog, dated July 1845, bound-in at end.
SCNHRB copy 1 stamped at head of title: S.F. Baird.
SCNHRB copy 1 stamped on title page: Library, U.S. National Museum, Smithsonian Institution Feb 9 1882 [manuscript accession no.] 124364.
SCNHRB copy 1 with binder's ticket: Bound by Westleys & Clarke, London.
SCNHRB copy 2 (39088000956581) has 16-page publisher's catalog, dated June 1,1843, bound-in at end.
SCNHRB copy 2 has bookplate of William Healey Dall.
SCNHRB copy 2 has bookseller's label: William Wesley, bookseller & publisher ... London.
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Über die Gattungen der Seeigellarven. Siebente Abhandlung über die Metamorphose der Echinodermen. Vorgetragen in der Königl. Akademie der Wissenschaften zu Berlin am 17. November 1853. Von. Joh. Müller
Principles of zoology touching the structure, development, distribution, and natural arrangement of the races of animals, living and extinct with numerous illustrations : Part 1, Comparative physiology : for the use of schools and colleges by Louis Agassiz and A.A. Gould
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SCNHRB copy (39088013487095) has card pasted to 1st front free endpaper with Agassiz's ink signature.
SCNHRB copy stamped on p. : Division Marine Invertebrates, carded Oct 30 1959.
SCNHRB copy stamped on p. , t.p., p. , p. : Withdrawn Smithsonian Institution.
SCNHRB copy bound in original brown publisher's cloth, blind-embossed design, title in gilt on spine; housed in an archival box.
SCNHRB copy (39088013487095) has card pasted to 1st front free endpaper with Agassiz's ink signature
SCNHRB copy bound in original brown publisher's cloth, blind-embossed design, title in gilt on spine; housed in an archival box
SCNHRB copy stamped on p. , title page, p. , p. : Withdrawn Smithsonian Institution
SCNHRB copy stamped on p. : Division Marine Invertebrates, carded Oct 30 1959
Lectures on the comparative anatomy and physiology of the vertebrate animals, delivered at the Royal College of Surgeons of England, in 1844 and 1846. By Richard Owen ... Part I.--Fishes ..
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Newborn Shrimp Often Undergo Sex Reversal, but Ocean Acidification Could Disturb That Natural Process
Every spring, young shrimp in the Mediterranean Sea turn from male to female—an important stage in their reproductive development. This change happens due to an abundance of a certain type of microalgae that the occasionally neon green-tinted shrimp rely on for their species’ survival. However, as ocean acidification intensifies, it could change the chemical makeup of the microalgae, potentially stunting the shrimp’s reproductive progress and threatening their existence, researchers report this week in PLOS ONE.
The shrimp, Hippolyte inermis Leach, dine on a specific kind of microalgae called Cocconeis scutellum parva, which flourishes in the seagrass meadows of the Mediterranean Sea, including acidified vents in the Bay of Naples. Eating the microalgae regulates the shrimp’s reproductive cycle.
Scientists have been fascinated by the sexual development of these odd little shrimp for years. Although Hippolyte inermis is considered a hermaphrodite like many other crustaceans, it is unusual in that it rapidly transitions from male to female without ever passing through an intermediate stage with attributes of both. This sex-reversal system has two distinct reproductive seasons. During the fall when Cocconeis microalgae is scarce, the majority of newborn shrimp are born male. After the spring, their male gonads age and drop off in a single molt and an ovary develops.
But younger shrimp who are born in the spring when microalgae are abundant can develop immediately into females by going through an even more rapid sex-reversal. Previous studies showed Cocconeis is responsible for this quick change. By releasing a still-unknown compound when eaten, Cocconeis kills the cells in the shrimp’s male sex gland, causing it to transition prematurely. This springtime switch helps restore balance after the population takes a hit in winter when predators, like black scorpionfish, devour the shrimp.
Lead author of the study Mirko Mutalipassi, a marine biotechnologist at the Stazione Zoologica Anton Dohrn in Naples, emphasizes that the shrimp’s dependence on the microalgae is so strong that their population growth syncs up with microalgae blooms.
“It’s really important for these shrimp,” Mutalipassi says. “This is the stabilizing factor for their natural population, because it allows the shrimp the ability to produce a lot of eggs and avoid being wiped out due to predation.”
The presence of such a strong plant-animal relationship in acidic conditions inspired Mutalipassi to use it as a tool for studying how increased ocean acidification will impact this ecosystem. “I’m really fascinated by co-evolution, both from a physiological point of view and a molecular point of view,” he says. “It’s a really interesting way to look at how two organisms interact with each other. It’s also a good model to study the effect of global changes on microalgae and invertebrates.”
Mutalipassi used the shrimp population as a probe to see what happens to the chemical composition of the microalgae as the ocean becomes more acidic. The research team grew Cocconeis at two different acidity levels: one at the present conditions, and one based on the predicted rise in ocean acidity over the next century as carbon dioxide levels increase. Afterward, they fed newborn shrimp one of the two groups of microalgae and observed whether they had different numbers of females, which would indicate a change in the microalgae’s compound that drives the shrimps' development.
The team’s results were surprising. Unlike some other microalgae that have failed to thrive under high CO2 levels, Cocconeis flourished, growing four times more cells under acidified conditions. This increase in growth implies that the microalgae could have a competitive advantage in acidified oceans of the future.
In contrast, the shrimp that were fed microalgae grown in higher levels of water acidification ended up with about half as many females as the shrimp that were fed the normal microalgae. Such a drastic difference suggests that the chemical compound that destroys the shrimp’s male sex glands may be changed by the acidified conditions, producing fewer females. In other words, Cocconeis thrives, but the shrimp suffer.
“This work is a neat example of researchers pushing beyond some of the basic questions of survival and growth of a single organism to also examine the relationships between species,” marine biologist Kaitlyn Lowder of the Scripps Institution of Oceanography at University of California San Diego says in an email. “To better understand what our marine ecosystems will look like in the future, it is incredibly important to look at the interaction between trophic levels, which can be difficult to do in a lab setting.”
Seemingly subtle changes like this that could trigger domino effects in an ecosystem are emblematic of the impact of climate change. As ocean acidification continues to disrupt the conditions of seawater, researchers are scrambling to learn how such changes might influence even the tiniest lifeforms on our planet.
Lowder, who was not involved in this study, argues that studying changes to the behaviors of organisms is crucial for gaining awareness about the changing environment. “It is only by pursuing these questions about the sexual transition of shrimp … that us scientists can get a better idea of what our oceans might look like in the future,” she says. “And importantly, [we can] have more stories about the potential impacts of ocean acidification to increase the public concern about this ongoing change to our oceans.”
Mutalipassi holds similar views, arguing that the chemical compound is really an “infochemical” for the environment—an underwater version of a canary in a coal mine.
“We now know that ocean acidification can disrupt a delicate ecological relationship that evolved over a million years,” Mutalipassi says. “This means that we have idiosyncratic consequences with the changes we are doing to our world.”
He also points out that the microalgae-shrimp relationship is only one of many that could be affected. “The impact of ocean acidification is bigger than what we see in the study,” he says. “We are just looking at a small piece of the puzzle.”
As Antarctica’s largest native land animal, the Antarctic midge—a flightless insect measuring less than one centimeter long—spends around nine months of the year frozen solid. But Belgica antarctica’s impressive abilities don’t end there: Devi Lockwood of the New York Times reports that midge larvae can also survive temperatures as low as -15 degrees Celsius, the loss of up to 70 percent of their bodily fluids and as long as a month without oxygen.
A new study published in the Journal of Experimental Biology suggests the invertebrate species owes its resilience to a combination of rapid cold hardening (a physiological process that enables animals to endure in freezing environments) and slightly warmer temperatures in its underground habitat. The research is still in early stages, but as Lockwood points out, a better understanding of midges’ survival in extreme conditions could eventually lead to innovations centered on human health.
Researchers led by Nicholas Teets of the University of Kentucky assessed B. antarctica’s endurance strategies during a field survey conducted in early 2018. According to the Times, the entomologist and his colleagues collected specimens by digging through seal and penguin excrement. Next, the scientists note in the paper, they exposed the midge larvae to a range of freezing conditions: Some were housed at 2 degrees Celsius for the duration of the experiment, while others were “directly frozen,” or plunged straight from 2 degrees to -9 degrees. The third group, subjected to rapid cold hardening, spent two hours adjusting from 2 degrees to -5 degrees, then 24 hours acclimating to -9 degrees.
Ultimately, the team found that larvae treated with rapid cold hardening bounced back from stress faster than their directly frozen counterparts; members of the group also exhibited significantly higher metabolic rates during recovery. Although the exact science behind the process remains unclear, the researchers point out that changes associated with rapid cold hardening appear to occur at the cellular level.
“These results provide strong evidence that RCH protects against a variety of sublethal freezing injuries,” Teets and his team write in the study. The mechanism further “allows insects to rapidly finetune their performance in thermally variable environments.”
Another factor in midges’ survival is their microhabitat. As the Times’ Lockwood notes, larvae live beneath Antarctica’s soil and snowpack. Here, temperatures hover around just below zero—considerably warmer than the southernmost continent’s average air temperature of below -20 degrees Celsius.
Speaking with the Gleaner’s Douglas White, co-author Leslie Potts—a graduate student in Teets’ Insect Stress Biology Lab—says studying midges and other native Antarctic species could one day help scientists develop better methods of preserving organs for transplant. Additional research may also yield insights on how extreme cold can help fight disease.
Come February 2020, Teets, Potts and an international group of collaborators will build on these findings during a return trip to Antarctica. According to a University of Kentucky press release, the scientists hope to compare the Antarctic midge with three other insect species, further explore how it survives in such a challenging environment and gauge how the continent’s changing climate has affected the species.
“I’ve always been interested in life at the extremes,” Teets tells the Lexington Herald-Leader’s Sydney Momeyer. “... And here’s an insect that is one of the most, if not the most, stress tolerant of its time.”
The earth’s atmosphere is made up of a lot of nitrogen (78 percent), a bit of oxygen (21 percent), a splash of argon (0.93 percent), a small amount of carbon dioxide (0.038 percent) and trace amounts of other gases. But it has not always been so. The composition of gases in the atmosphere can change (and is changing now as we burn fossil fuels), and the fossil record reveals how something as deceptively simple as air can influence the history of life.
If you visited what is now North America 300 million years ago, near the close of the Carboniferous period, you would have been greeted by a very unfamiliar scene. The landscape was dominated by vast swamps filled with huge lycopods (relatives of club mosses that grew to the size of trees), amphibious vertebrates up to nearly 20 feet in length and enormous arthropods. The Meganeura, a relative of the dragonfly that had a wingspan more than two feet across, buzzed through the air over the giant Arthropleura, a nine-foot-long millipede. Never before or since have terrestrial invertebrates grown to such prodigious sizes.
The trigger for this rampant gigantism was a peculiar, newly evolved characteristic of plants that drove oxygen levels to as high as 35 percent of the atmosphere during the Late Carboniferous. Lush equatorial forests produced a considerable amount of oxygen as a byproduct of photosynthesis, but that alone wasn’t enough to drive atmospheric oxygen to such high levels. The cause was the chemical compound lignin, which plants use to build themselves up. Bacteria of the time were so inefficient at breaking down lignin in dead plants that they left behind a huge amount of carbon-rich plant material to become sequestered in the swamps (and eventually to transform into the rich coal deposits that gave the Carboniferous its name). Bacteria use oxygen as they break down carbon-rich material, but lignin prevented this process until bacteria evolved the ability to decompose the compound. This biological quirk caused oxygen levels to soar.
The surplus of oxygen allowed amphibians, which take in some of the gas through their skins, to breathe more efficiently and grow to larger sizes. Arthropods breathe in a different way: they possess a network of branching tubes called tracheae that connect small openings in an invertebrate’s exoskeleton to its cells, and oxygen seeps through the body via this system. In an oxygen-rich atmosphere, more oxygen could be diffused through this branching network, and this opened up evolutionary pathways that allowed arthropods, too, to grow to gargantuan proportions. The fact that the oxygen would have increased the air pressure as well meant that the large flying insects of the time would have gotten more lift for each beat of their wings, allowing flying arthropods to reach sizes that are structurally impossible for their present-day relatives.
While the giant arthropods were crawling and buzzing about, the first amniotes—lizard-like vertebrates that had broken their link with the water through their ability to reproduce via shelled eggs—were also diversifying. During the next chapter of earth’s history, the Permian (about 299 million to 251 million years ago), these early relatives of dinosaurs and mammals gave rise to a variety of new forms, with the relatives of early mammals (collectively known as synapsids), especially, gaining ecological dominance. For the first time, terrestrial ecosystems supported an interconnected network of predators and herbivores of various sizes, and by about 250 million years ago there were approximately 40 different families of land-dwelling vertebrates inhabiting the globe. But at the period’s close almost all of that diversity was extinguished by the greatest natural catastrophe this planet has ever known.
During the early days of paleontology, naturalists marked off boundaries in geological history by the abrupt, mass disappearance of some species from the fossil record followed by the appearance of a new, different fauna. They did not realize it at the time, but what they were doing was marking off mass extinctions, and the one that ended the Permian was perhaps the worst in earth’s history. Up to 95 percent of all known sea creatures were wiped out, as were 70 percent of terrestrial animals. University of Bristol paleontologist Michael Benton has called this event “when life nearly died.”
Identifying a mass extinction event is not the same as explaining it, however, and the catastrophe at the end of the Permian is perhaps the most puzzling murder mystery of all time. Scientists have proposed a list of possible extinction triggers, including global cooling, bombardment by cosmic rays, the shifting of continents and asteroid impacts, but many paleontologists’ prime suspect now is the intense eruptions of the Siberian Traps, volcanoes that covered nearly 800,000 square miles of what is now Russia with lava.
The earth was much warmer at the end of the Permian than it is today. The atmosphere was relatively rich in carbon dioxide, which fueled a hothouse world in which there were almost no glaciers. The eruption of the Siberian Traps would have added vast amounts of greenhouse gases into the atmosphere, causing further global warming, increasing ocean acidity and lowering atmospheric oxygen levels. These drastic changes to the atmosphere and resulting environmental effects would have caused many organisms to asphyxiate from the lack of oxygen, while others would have died from an excess of carbon dioxide in the blood or otherwise perished because they were physiologically unable to cope with these new conditions. Where rich, diverse communities of organisms once thrived, the extinction left only “crisis” communities of a few species that proliferated in the vacant habitats.
Though these changes to the atmosphere greatly pruned the evolutionary tree 251 million years ago, they did not make the planet permanently inhospitable. Life continued to evolve, and levels of oxygen, carbon dioxide and other gases continued to fluctuate, spurring the climate from “hothouse” to “icehouse” states numerous times.
The earth may now be entering a new hothouse era, but what is unique about the present is that humans are taking an active role in shaping the air. The appetite for fossil fuels is altering the atmosphere in a way that will change the climate, adding more carbon dioxide and other greenhouse gases to the mix, and these fluctuations could have major implications for both extinction and evolution.
The earth’s present conditions are different enough from those of the Late Permian that a similar catastrophe is unlikely, but the more we learn about ancient climates, the more clear it is that sudden changes in the atmosphere can be deadly. A recent study led by biogeochemist Natalia Shakhova, of the International Arctic Research Center, suggests that we may be approaching a tipping point that could quickly ramp up the global warming that is already altering ecosystems around the world. An immense store of methane, one of the most potent greenhouse gases, lies beneath the permafrost of the East Siberian Arctic Shelf. The permafrost acts as a frozen cap over the gas, but Shakhova found that that the cap has a leak. Scientists aren’t sure whether the methane leak is normal or a recent product of global warming, but if current projections are correct, as the global climate warms, sea level will rise and flood the East Siberian Arctic Shelf, which will melt the permafrost and release even more of the gas. As more greenhouse gases build up, the planet inches ever closer to this and other possible tipping points that could trigger rapid changes to habitats all over the world.
Perhaps the peculiar conditions that allowed giant arthropods to fly through air composed of 35 percent oxygen will never be repeated, and we can hope that the earth does not replay the catastrophe at the end of the Permian, but in fostering a hothouse climate our species is actively changing the history of life on earth. How these changes will affect us, as well as the rest of the world’s biodiversity, will eventually be recorded in the ever-expanding fossil record.
Bugs have an image problem.
But those creepy-crawly pests have a defender in May Berenbaum, head of the University of Illinois' entomology department. For the past three decades, Berenbaum has hosted the annual Insect Fear Film Festival in hopes of dispelling stereotypes people hold about bugs. She screens films, cartoons and shorts with an insect theme—past festivals include "Mantis Movies", "Alien Arthropods!" and "Pesticide Fear!"—and discusses the movies, and their biological inaccuracies, with the audience afterward.
Berenbaum was not always a lover of the six-legged. She was afraid of insects until an entomology course in college helped conquer her fear. Now, she uses her festival to convert others.
"I can totally relate to people who don't like insects,"she says. "It's probably because they don't know very much about them. This [festival] is an enjoyable, pleasant way to overcome any aversion to insects that arises from, at least, a lack of familiarity people have."
Here are some of Berenbaum's favorite movies featuring arthropod antagonists—and where, in their plot lines, the screenwriters stray from actual science:
The Tuxedo (2002): An unlikely bug-thriller lead
In this Jackie Chan action flick, an evil-doer wants to taint the world's water supply with a special kind of bacteria that somehow causes water to dehydrate rather than quench thirst. The bacteria are disbursed by water striders, the bugs that skate along the surface of water.
"An unlikely insect group to feature in any movie," says Berenbaum, but it's critical to the plot. The insects must be able to land on water supplies without triggering any surface alarms. The bad guy keeps a queen water strider in an underground lab to help carry out his plan, but, as Berenbaum told famed movie critic Roger Ebert when the film first came out, water striders don't have queens.
"There are about 500 species of gerrids in the world and, as far as I know, not a single one of those 500 species is eusocial (i.e., has a complex social structure with reproductive division of labor and cooperative brood care)," she said. "I don't even know of an example of maternal care in the whole group."
Mosquito (1995): Texas Chainsaw Massacre meets bug horror
When mosquitoes feed on the corpses of aliens who crash-land in the Michigan wilderness, they grow into 3-foot-long blood-sucking monsters that prey on campers.
"I don't know of any example of a blood meal containing a nutrient that would cause an exponential increase in size," says Berenbaum. Bug spray isn't enough to send these insects packing. In the film, Gunnar Hansen, the actor who also plays Leatherface in Texas Chainsaw Massacre, uses a chainsaw to dispatch the beasts—"a very novel biological control mechanism," notes the entomologist.
The Bees (1978): Horror, with a stinging message
A new, deadly species of killer bees descends upon mankind, and a team of scientists works to stem their spread. The researchers, one played by John Saxon, develop a system for translating the communications of the bees, which, as it turns out, are super intelligent creatures with some strong opinions on how humans are treating the environment.
In the end, Saxon's character interprets a message from the bees to the United Nations, calling on humans to take better care of the world. Berenbaum says while bees do communicate among themselves, a sentence-for-sentence translation doesn't seem likely.
Also, she says with a laugh, throughout the movie, scientists say "pherones" instead of "pheromones."
Monster from Green Hell (1958): Space-bound wasps strike African jungle
What happens when scientists expose wasps to outer space radiation? The insects mutate into giant killing machines—or, so say the filmmakers of Monster From Green Hell.
In the movie, a rocket filled with the wasps crashes in the heart of the African jungle, and the heroes must embark on an expedition to find the oversized bugs. "The biological attribute that I like best about these giant wasps is that they indeed did have compound eyes, like wasps do," Berenbaum says, "but the compound eyes rolled in their sockets, which compound eyes don't do."
Mimic (1997): Designer bugs wreak havoc in New York's subways
"Sometimes, what is regarded as cinematically good is biologically just as ridiculous," says Berenbaum. So is the case with Mimic, perhaps the most acclaimed film of Berenbaum's picks.
Scientists develop hybrid insects genetically engineered to kill cockroaches that are spreading a strange disease plaguing New York City. But soon, the lab-created bugs evolve so they can attack their human prey in the New York subways by imitating 6-foot tall people.
Mimic is one of many insect horror films featuring larger-than-life monsters, but bugs really aren't meant to be big, explains Berenbaum. "Their physiology, their basic body plan does not work well for large organisms," she says. "An insect is built to be small. That's why they're so successful."
Berenbaum likes this movie's back story: Academy Award-winning actress Mira Sorvino struck up a friendship with famed entomologist Thomas Eisner to prepare for her role. Later, Eisner named a chemical excreted by beetles after her, calling it "mirasorvone."
Beginning of the End (1957): Giant grasshoppers on the prowl
Grasshoppers grow to enormous proportions after digging into some irradiated food at a U.S. Department of Agriculture test facility in central Illinois. They terrorize small towns as they close in on Chicago, and the military scrambles to respond. "We can't drop an atom bomb on Chicago!" says researcher Dr. Ed Wainwright, played by Peter Graves, after hearing the military's pitch for a particularly aggressive containment strategy.
Eventually, Wainwright broadcasts a frequency to lure the grasshoppers into Lake Michigan. So, what do the filmmakers get wrong?
"A shorter list would be about what is accurate," Berenbaum says of Beginning of the End, one of her favorite insect movies. "Radiation-induced mutations rarely produce giant vegetables—and even more rarely produce giant grasshoppers," she notes. But there are shades of truth in the film's climax. Grasshoppers do indeed use acoustic communication, but Berenbaum isn't sure they'd respond to the siren song in the movie.
Tail Sting (2001): Sky-high scorpions
Mutated scorpions escape the cargo hold of a jumbo jet flying from Australia to Los Angeles in this low-budget film. The large bugs were developed to cure disease, but they end up terrorizing the plane.
"The whole concept of scorpions the size of Volkswagens ...," Berenbaum says with a chuckle. "Arthropods, with the exception of marine crustaceans, don't get that big."
Berenbaum says many insect horror films follow the same structure: Scientists invent something, something goes awry and a hero saves the day. What changes is the technology itself—from radiation in the 1950s to genetic engineering today. "You can learn a lot [about the development of science] from bad science fiction," she says.
The first time Tim Mousseau went to count birds in Fukushima, Japan, radiation levels in the regions he visited were as high as 1,000 times the normal background. It was July 2011, four months after the Tohoku earthquake and subsequent partial meltdown at the Fukushima-Daiichi nuclear power plant, and the nation was still recovering from massive infrastructure damage. Still, when Mousseau and his research partner rented a car and drove up from Tokyo, they encountered little resistance on the road.
“I knew we had to get there and capture as best we could the early effects [of radioactive contamination] that nobody had really looked for,” he remembers thinking after seeing news of the Fukushima disaster. “Ultimately we realized that our best possible approach for that first year was simply to start doing bird counts.”
Now, after four years surveying bird populations in 400 sites around Fukushima-Daiichi, Mousseau and his team have assembled a grim portrait of the disaster’s impact on local wildlife, using bird populations as a model system. Even though radioactivity has dropped throughout the region, their data show that bird species and abundances are in sharp decline, and the situation is getting worse every year.
“At first only a few species showed significant signs of the radiation’s effects,” Mousseau says. “Now if you go down and around the bend maybe five or ten kilometers [from a safe zone] to where it’s much, much hotter, it’s dead silent. You’ll see one or two birds if you’re lucky.”
Mousseau’s team conducted almost 2,400 bird counts in total and gathered data on 57 species, each of which showed specific sensitivity to background radiation. Thirty of the species showed population declines during the study period, the team report in the March issue of the Journal of Ornithology. Among these, resident birds such as the carrion crow and the Eurasian tree sparrow demonstrated higher susceptibility than migratory species, which didn’t arrive in the region until a few weeks after the partial meltdown in early March.
Nuclear accidents are rare in human history, so we have very little data about such radiation’s direct effects on wildlife. Mousseau has spent the past 15 years drawing comparisons between nuclear events to help build up our knowledge base and fill in the gaps. For instance, while there are no official published records of the Chernobyl disaster’s early impact on wildlife, plenty of work has been done in recent years to assess Chernobyl's ecosystem post-accident, from local birds to forest fungi.
When Mousseau returned to Fukushima in 2012, he began capturing birds in irradiated zones that had patches of bleach-white feathers. It was a familiar sign: “The first time I went to Chernobyl in 2000 to collect birds, 20 percent of the birds [we captured] at one particularly contaminated farm had little patches of white feathers here and there—some large, some small, sometimes in a pattern and other times just irregular.”
His team thinks these white patches are the result of radiation-induced oxidative stress, which depletes birds’ reserves of the antioxidants that control coloration in their feathers and other body parts. In Chernobyl, the patches have a high coincidence with other known symptoms of radiation exposure, including cataracts, tumors, asymmetries, developmental abnormalities, reduced fertility and smaller brain size.
By 2013, the birds Mousseau was counting in Fukushima had white patches big enough to be seen through binoculars.
Presented together, Mousseau thinks such data sets on Chernobyl and Fukushima could offer significant evidence for radiation’s prolonged, cumulative effects on wildlife at different stages after a nuclear disaster. But other experts have a completely different take on the available information.
“I’m not convinced about the oxidative stress hypothesis, full stop,” says Jim Smith, editor and lead author of Chernobyl: Catastrophe and Consequences and an expert on pollution in terrestrial and aquatic ecosystems. “The radiation levels in both Fukushima and Chernobyl are currently low-dose, and the antioxidant capacity of a cell is way, way bigger than the oxidizing capacity of the radiation at those levels,” he says. This would mean the white feather patches—and perhaps the overall bird declines—are being caused by something other than radiation.
Birds’ feathers often change color as a byproduct of aging, much like our hair color changes as we get older. They also get replaced in molt cycles a few times a year and require new doses of melanin every time to retain their pigment. According to Yale evolutionary ornithologist Richard Prum, this opens the door for pigment mutations to occur quite regularly—whether or not a bird lives in or passes through a radiation zone.
“It’s a bit like fixing a car: the problem may be obvious, but there are lots of moving parts,” says Prum, who studies the evolution of avian plumage coloration. “Melanin stress can manifest in the same way—such as white feathers—under a variety of circumstances, and the causes behind it can be very diverse. Just this winter I saw four species with abnormal white pigmentation visit my feeder at home, but I’m not too worried about radiation levels in New Haven.”Wild boars are just some of the animals that seem to be thriving in the Chernobyl exclusion zone. (VASILY FEDOSENKO/Reuters/Corbis)
Prum says he had heard the ecosystem at Chernobyl was doing quite well, an opinion defended by Mousseau’s critics. Back at the University of Portsmouth in the U.K., Smith primarily studies aquatic invertebrates, and in some of Chernobyl’s most contaminated lakes he has actually observed increased levels of biodiversity following the accident.
“Many of the literature studies on animals find it difficult to distinguish between the early effects of high doses shortly after the accident and later effects of much lower subsequent doses,” Smith says. “Plus some of them don’t properly account for the ecosystem impacts of removal of humans.”
Back in 2000, Robert Baker and Ron Chesser of Texas Tech University published a paper characterizing Chernobyl as a wildlife preserve, established thanks to the absence of humans since the accident. Both scientists have maintained that biodiversity and species abundance in Chernobyl and Fukushima are, in the long term, not adversely affected by radiation.
“Despite our best efforts, post-accident field studies aren’t sufficient to give us a clear picture,” says Chesser. “They offer no good controls, because we aren’t working with data from before the accident.” Chesser suggests that physiological aberrations of the sort Mousseau has observed are not conclusive results of chronic radiation exposure. Instead, they reflect other sources of oxidative stress including reproduction, immune response to infection and disease and strenuous physical activity such as migration.
“All the evidence that I grew up with and read in the last 60 years tells me [Mousseau’s findings] are probably wrong,” Chesser says, explaining why he disputes radiation as the cause behind the bird declines in Japan. “I don’t intend to cast aspersion on anyone, but if your evidence is really outside the norm, you better have some extraordinary data to back that up.”
Mousseau acknowledges that his research methods deviate from those of “old-school radiation biologists,” whose work has typically measured responses to radiation based on Geiger counter readings of individual animals. Not caring about the exact levels of radioactivity, as Mousseau says he does not, understandably ruffles some feathers.
“We’re strictly motivated by measurements of ecological and evolutionary response,” Mousseau says. “Our extraordinary evidence relates to these censuses, these massively replicated bionic inventories across a landscape scale and in both locations, and that has not been done in any rigorous way by any of these other groups.
“The data are not anecdotal, they’re real and rigorous,” he adds. “They’re replicated in space and time. How you interpret them is up for grabs, and certainly a lot more experimentation needs to be done in order to better appreciate the mechanism associated with these declines.” For their part, Mousseau’s team hopes next to understand why different bird species in their data appear to demonstrate varying levels of radioactive sensitivity. They’re headed to Chernobyl again next week, and back to Fukushima in July.
Update 5/1: James Smith's affiliation has been corrected; he is a professor at the University of Portsmouth.
Scientists are grooming an unlikely ally in the fight against mosquitoes and the deadly diseases they carry. Infecting mosquitoes with strains of a common bacteria can curb the insects' ability to carry and spread scourges like dengue, yellow fever and Zika, lab studies show.
And now it appears these bacterial infections, from a genus of microbes known as Wolbachia, are already at work in nature reducing the spread of malaria, at least in West Africa, something that hadn't been seen before in the real world.
“Wolbachia appears to be acting as a natural malaria control agent,” says molecular entomologist Flaminia Catteruccia, of Harvard University. “The true extent of this effect is still unknown as we only tested a small proportion of mosquitoes. It's still early days but it's a promising new tool that may provide an important contribution to our fight for malaria eradication.”
Catteruccia and colleagues examined 221 Anopheles female mosquitoes, the major vectors of African malaria, which were collected from homes in Burkina Faso. They found malaria parasites in 12 of them, a five percent ratio consistent with past studies. A whopping 116 of the mosquitoes, on the other hand, were infected with Wolbachia bacteria, which had been unknown in the species before the group spotted it in 2014.
But just a single mosquito was found to test positive for both Wolbachia and malaria, suggesting that the bacteria is effectively preventing malaria parasites from establishing themselves in mosquitoes where the bacteria is present, they report today in Nature Communications.
Female mosquitoes infected with Wolbachia also laid eggs and reproduced more rapidly than their counterparts, likely aiding the spread of the infection and its anti-malarial benefits throughout local populations. A sample of 602 mosquitoes showed that from 19 to 46 percent (depending on the sample year) carried the Wolbachia strain wAnga.
“Others have put Wolbachia into mosquitoes and have been able to show that when it's present it has an effect on limiting malaria parasites. But that was all done in a lab,” says biologist Luciano Moreira, of Brazil's Oswaldo Cruz Foundation and the global non-profit Eliminate Dengue.
“This group has found a population in Africa that was naturally infected, which is very interesting. In many parts of Africa, for example, malaria is a huge problem while in other places it doesn't seem to be as big of a problem. Maybe that's because mosquitoes in those areas are infected with Wolbachia. Here they found a situation where that might be happening in the real world and that's very important and exciting.”
The stakes are high. Mosquitoes are among the deadliest enemies of our own species. Because of the diseases they carry, these pests account for some 725,000 deaths every year. About 60 percent of those deaths are due to malaria.
Wolbachia is a common bacterium with many different strains. It infects millions of invertebrate species and more than half of all insects, but until recently wasn't known to occur in the major disease-carrying mosquito species.
Wolbachia isn't contagious like a cold virus. It's passed down only from mother to offspring, and the bacterium has some interesting ways of ensuring its own future.
The bacteria hijack the mosquito reproductive system. When males mate with females not carrying the same strain, their offspring aren't viable. The bacteria effectively sterilize the male's sperm.
Infected females can reproduce with males carrying a matching Wolbachia strain, or uninfected males, and will pass on Wolbachia to their offspring in either case. This gives infected females a reproductive advantage that allows them to invade a population if introduced and spread the infection widely.
It's not entirely clear what physiological methods the bacteria use to thwart other diseases that would crowd into their mosquito hosts. “These bacteria may somehow stimulate the mosquito immune system and render it more effective at killing malaria parasites; or alternatively they may compete for resources [perhaps critical fatty acids like cholesterol] that are also needed by Plasmodium,” says Catteruccia.
Whatever the reason, it's becoming increasingly clear that those methods can be effective.
Earlier this month Moreira co-authored a study in Cell Host & Microbe showing that Wolbachia blocked the spread of the Zika virus. His group fed human blood infected with Zika to mosquitoes, some with Wolbachia infections and some without. Those with Wolbachia ended up with far fewer Zika infections.
Catteruccia and colleagues also collected saliva from Zika-infected mosquitoes and injected it into others. Among the 80 mosquitoes without Wolbachia, 68 of them (85 percent) acquired a Zika infection. Of the 80 who did carry Wolbachia, none contracted Zika.
This preliminary work was promising but not surprising. Other projects have shown significant impacts on dengue, another disease spread by the same mosquito species.
Over a ten-week period in 2011, Scott O’Neill of Monash University (Australia) unleashed swarms of Wolbachia-infected mosquitoes into two northern Australian towns as part of Eliminate Dengue.
Not only did the insects survive, they thrived. And even today, most of the Aedes aegypti mosquitoes in the region carry Wolbachia.
“Now five years later the populations are still 85 or 90 percent positive for Wolbachia, so it's really been maintained and they've seen no local transmission of dengue in those areas,” Moreira says.
Eliminate Dengue is now operating similar projects in Indonesia, Vietnam, and Columbia. Moreira is running one in two small locations in Rio de Janeiro, Brazil.
“We did releases from August of last year to January of this year and are now in a monitoring phase,” he explains. “Every week we collect mosquitoes and our numbers show that at least 80 percent are infected with Wolbachia, so the infection is sustainable and that's very promising.”
Scott O'Neill adds that Eliminate Dengue is now working to expand the scale with much larger, randomized trials in Indonesia and Vietnam.
“At the same time we are preparing for large deployments over 1 to 3 million people in South America with the goal of learning how to undertake large deployments logistically as well as reduce the cost of deployment to under US $1 per person,” he adds.
Meanwhile, the first commercial use of the bacterium to fight mosquito-borne disease might occur right here in the United States on a backyard scale. The EPA is currently reviewing an application from MosquitoMate, a biotech company which hopes to market Wolbachia as a targeted pesticide against Asian tiger mosquito (Aedes albopictus).
The MosquitoMate method is to breed males with Wolbachia, then release them into the wild (or a homeowner's backyard) to breed with local females. Because none of the females naturally carry the bacteria, all these matings should be sterile and hopefully populations will plunge. The company, which was incubated at the University of Kentucky, has tested the approach in three different states over the past three years and reported some success.
The public comment period on the proposal ended May 31, and a decision is forthcoming.
Of course bacteria isn't the only intriguing option for controlling mosquito-borne disease—there are plenty of other deterrents and battling the bugs will likely take every weapon in the human arsenal. As this month's Smithsonian Magazine cover story details, gene editing techniques could be used to create disease-free mosquitoes—or even wipe out the insects entirely. But that method is sure to be controversial, and likely won't be practical for perhaps a decade.
Meanwhile the largely unsung Wolbachia bacteria may already be at work in the wild, and might be more easily co-opted for further gains.
“If we can find natural populations of mosquitoes that have Wolbachia we can try to put those mosquitoes into other areas where malaria is a huge problem,” Moreira says. “This is the final goal, many people are trying to find solutions for malaria and the other diseases and I think that Wolbachia is a very promising approach.”
One November night each year, beneath the full moon, more than 130 species of corals simultaneously spawn in Australia’s Great Barrier Reef. Some corals spew plumes of sperm, smoldering like underwater volcanoes. Others produce eggs. But most release both eggs and sperm, packed together in round, buoyant bundles as small as peppercorns and blushed in shades of pink, orange, and yellow.
At first, the parcels wait in the lips of corals. Then, in stunning unison, numerous corals lose their seeds, which hover momentarily above their parents, preserving the shape of the reef in an effervescent echo. Gradually, the bundles drift skyward.
The first time marine biologist Oren Levy witnessed this phenomenon, in 2005, he was near Heron Island, off the east coast of Australia. Fish, marine worms, and various predatory invertebrates zipped through the water, feeding on the coral confetti, which rose slowly from the reef in huge quantities. “It’s like the whole ocean wakes up,” says Levy, who now heads a marine ecology research team at Bar Ilan University in Israel. “You can watch videos, you can hear about it, but once you are actually in the midst of the biggest orgy on this planet, there’s nothing else like it.”
Corals continue to reproduce in the Great Barrier Reef today, though the sections that have escaped the ravages of climate change are rapidly shrinking. Swimming near the surface of the sea that memorable night 12 years ago, Levy encountered dense pink mats of accumulating eggs and sperm. There, drenched in moonlight, gametes from different colonies began to fuse and form free-swimming larvae, which would eventually settle on the seafloor, bud, and construct new coral citadels—a process now more vital than ever.
The moon is not the only environmental cue the corals use to achieve sexual synchrony on such a massive scale; water temperature and day length also matter. Yet the moon’s presence seems to be crucial. If the sky is too cloudy, and the moon obscured, the corals will often not spawn. Sometimes they delay until the next full moon. In the course of their studies, Levy and his colleagues revealed that not only do corals have light-sensitive neurons tuned to the dim blue wavelengths of moonlight, they also have genes that change their activity level in sync with the waxing and waning moon, regulating reproduction.
Scientists have known for centuries that the moon alters Earth’s ecosystems through gravity. As it spins around our planet, warping space-time, the moon contributes to a complex contortion of the oceans, producing twin bulges we call the tides. In turn, the daily marriage and separation of land and sea transforms the topography of numerous species’ homes and the access they have to food, shelter, and each other.
The moon also stabilizes Earth’s climate. Earth does not have perfect posture; it is tilted along its polar axis, circling the sun at an angle of about 23 degrees. The moon acts as an anchor, preventing the Earth from varying its axial tilt by more than a degree or two. Without the moon, our planet would likely wobble about like a dreidel, tilting a full 10 degrees every 10,000 years, and possibly oscillating the global climate between ice ages and hellish heat the likes of which no species has ever endured.
What is becoming increasingly clear, however, is that the moon also influences life in a more surprising and subtle way: with its light. Most organisms possess an array of genetically encoded biological clocks that coordinate internal physiology and anticipate rhythmic changes in the environment. These clocks are wound by various environmental cues known as zeitgebers (time givers), such as light and temperature.
Sunlight is the best-studied zeitgeber, but it turns out that for many aquatic creatures, moonlight is just as crucial. In the past few years, scientists have rekindled a long-neglected curiosity about the moon’s power to manipulate life, reviving studies on biology’s secret moon clocks.
In antiquity, the influence of the moon on earthbound life was intuited—and celebrated. Our ancestors revered the moon as the equal of the sun, a dynamic signature of time, and a potent source of fertility.
“Time was first reckoned by lunations, and every important ceremony took place at a certain phase of the moon,” wrote English classicist Robert Graves in The Greek Myths. A 25,000-year-old limestone carving discovered in a rock shelter in France depicts a pregnant woman holding what appears to be a bison horn with the swoop of a crescent moon and 13 small notches—a possible paean to reproductive and lunar cycles. And some early Meso-American cultures seemed to believe that the moon deity controlled sexuality, growth, rainfall, and the ripening of crops.
In more recent times, the importance of the moon to Earth’s creatures has been eclipsed by the great solar engine of life. The sun is searingly bright, palpably hot, bold, and unmissable; our steadfast companion for many of our waking hours. The moon is spectral and elusive; we typically catch it in glimpses, in partial profile, a smudge of white in the dark or a glinting parenthesis.
Sunlight bakes the soil, bends the heads of flowers, pulls water from the seas. Moonlight seems to simply descend, deigning to visit us for the evening. We still perceive the sun as the great provider—the furnace of photosynthesis—but the moon has become more like mood lighting for the mystical and occult; more a symbol of the spirit world than of our own. “There is something haunting in the light of the moon; it has all the dispassionateness of a disembodied soul, and something of its inconceivable mystery,” wrote Joseph Conrad in Lord Jim. The sun’s immense power over Earth and its creatures is scientific fact; to endow the moon with equal power is to embrace fairy tales and ghost stories.
Perhaps with such biases in mind, scientists in the past several decades have been much more interested in earthly life’s relationship with the sun than its potential interaction with the moon. This disparity widened around the 1970s and ’80s with the discovery of circadian clocks—sun-synced networks of genes, proteins, and neurons—in flies, rodents, and other lab animals. But nature itself has been far more impartial, especially in the oceans, where life first evolved. Numerous sea creatures also move in time with the silver pendulum of night.
Often, moonlight—independent of the tides—signals the start of a species-wide reproductive marathon. By syncing these orgies to particular phases of the moon—one of nature’s most prominent and reliable records of time—animals increase their chances of finding a mate and overwhelm opportunistic predators with their sheer numbers.
During certain phases of the moon, Sesarma crabs in Japan collectively scuttle across mountain slopes toward sea-flowing rivers, where they release their eggs and sperm. The annual migrations of Christmas Island crabs, which move in waves of crimson from forest to sea to mate and lay their eggs, also seems to be linked to moonlight’s shifting intensity. Moonlight even sharpens the visual acuity of horseshoe crabs, which come ashore on certain nights to mate. Likewise, studies suggest that the moon’s glow is one of the environmental triggers for synchronous spawning in tropical rabbit fish. Moonlight likely increases production of the hormone gonadotropin in these fish, which promotes gamete maturation.Bobtail squids house bioluminescent bacteria in their tissues. Viewed from below, the glowing cephalopods mimic the moon. (FLPA / Alamy)
In 2013, neurobiologist Kristin Tessmar-Raible and her colleagues published some of the most compelling evidence of a molecular moon clock in an ocean creature. They studied the marine bristle worm Platynereis dumerilii, which looks like an amber centipede with tiny feathered oars running the length of its body. In the wild, the bristle worm lives on algae and rocks, spinning silk tubes for shelter.
While reading studies from the 1950s and ’60s, Tessmar-Raible learned that some wild bristle worm populations achieve maximal sexual maturity just after the new moon, swimming to the ocean surface and twirling in circles in a kind of whirling dervish nuptial dance. The studies suggested that changing levels of moonlight orchestrated this mating ritual. “At first I thought this was really crazy in terms of biology,” says Tessmar-Raible, who notes that she grew up far from the ocean, “but then I started talking to colleagues in marine biology and realized that this might not be so uncommon.”
To learn more, Tessmar-Raible and her colleagues kept bristle worms in plastic boxes, feeding them spinach and fish food, and simulating typical and aberrant moon cycles with an array of standard light bulbs and LEDs. Worms raised in perpetual light or in entirely moonless day-night cycles never displayed reproductive rhythms. But worms reared with periodic nocturnal illumination synced their spawning rituals to the phases of their artificial moon.
As suggested by earlier studies, Tessmar-Raible found light-sensitive neurons in the worms’ forebrains. And genetic sequencing revealed that the bristle worm has its own versions of essential molecular clock genes found in terrestrial insects and vertebrates. Tessmar-Raible’s conclusion is that the worms have a robust lunar clock analogous to the more familiar sun-synced circadian clock. “This is an endogenous oscillator,” she says. “Something in the body preserves the memory of those nocturnal illuminations.”
In similar studies, Oren Levy and his colleagues collected pieces of living corals from Heron Island reef and housed them in large outdoor aquaria, some of which were exposed to ambient sunshine and moonlight, some shaded at night to block all moonlight, and some subjected to dim artificial light from sunset to midnight and then kept in the dark until sunrise. Each day for eight days before the estimated night of mass spawning, the researchers collected bits of corals from the different aquaria and analyzed the activity of their genes.
The corals in natural conditions spawned as predicted and expressed many genes only during or just before releasing their gametes. Corals subjected to artificial light and deprived of moonlight displayed anomalous gene expression and failed to release their gametes.
For other species, the moon’s light is more important as a navigational cue than as an aphrodisiac.
Migrating chum salmon swim more quickly and at shallower depths during a full moon, likely because they are using its light as a lodestar. Albatrosses and streaked shearwaters often fly more frequently and for longer periods of time under a full moon, perhaps because they can travel farther with increased visual acuity, or to avoid lurking ocean predators whose eyesight is improved by moonlit water. Newborn rabbit fish seem to depend on moon phases to reach safety: on the day before or during the new moon, when the sea is darkest, rabbit fish fry born in the open sea migrate en masse to the haven of coral reefs.
Even plankton move differently beneath the moon. Every day, in oceans around the world, plankton sink to greater depths, and rise again at night, most likely to avoid predation and feed in shallower waters under the cover of dark. Scientists are still not sure what drives this daily rhythm, but a biochemical clock synced to the sun is one of the primary hypotheses. During the Arctic winter, however, sunlight never reaches some regions of the ocean. A recent study suggests that plankton living in this frigid continuous dusk rely instead on the moon.
Some animals do not just change beneath the moon; they change into the moon. During the day, bobtail squid—speckled, peanut-sized cephalopods related to cuttlefish—bury themselves in sand to rest and hide from predators. At night, they emerge to feed on shrimp and worms. Having abandoned the seafloor and exposed themselves to potential danger, the tiny mollusks cloak themselves in an entirely different kind of camouflage.
Bobtail squid have evolved one of the most magical symbioses on the planet. Bioluminescent bacteria live within the folds of a chambered sac in the squid’s mantle, generating light that spills from the squid’s underside. A lens and color filter attached to this internal lantern—known as the light organ— modulate the microbial glow to mimic the light of the moon and stars filtering down through the water. In this way, bobtail squid erase their own shadow. Instead of seeing a conspicuous squid-shaped silhouette, any predator gazing up from below sees only more moonlit sea. Several other species—including deepwater fish, crustaceans, and true squid—use similar counter-illumination strategies.
The moon has always been simultaneously foreign and familiar, frustratingly distant yet teasingly intimate. It’s the nearest alien world to us, so close we consider it “ours”—our satellite, subject to our gravity. Yet for most of human history, the moon was fundamentally unreachable, regarded as an ethereal disc beyond our realm.
The history of our relationship with the moon is a history of closing that gap. On November 30, 1609, Galileo gazed at the moon through his telescope and concluded that its surface was not “uniformly smooth and perfectly spherical, as countless philosophers have claimed about it and other celestial bodies, but rather, uneven, rough, and full of sunken and raised areas like the valleys and mountains that cover the Earth.” Nearly four centuries later, we landed on the moon and stepped out of a spacecraft onto its rugged terrain. Now, anyone with Internet access can explore a virtual facsimile of the moonscape, courtesy of Google.
The more we have learned about the Earth and moon, the closer they have seemed. From the beginning of life on this planet, the moon—that looping mirror of the sun—without ever touching us, without generating light or heat of its own, profoundly shaped the rhythms of Earth and its collective life forms. The moon, our silver sister, was always right here with us, awash in our seas, pooling in our eyes, written into the planet’s very DNA.
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In a sprawling gallery of the Royal Ontario Museum, curators and technicians crowded around two large coolers that had recently arrived at the Toronto institution. Wriggling inside the containers were live sea lampreys, eel-like creatures that feed by clamping onto the bodies of other fish, puncturing through their skin with tooth-lined tongues, and sucking out their victims’ blood and bodily fluids. Staff members, their hands protected with gloves, carefully lifted one of the lampreys and plopped it into a tall tank. It slithered through the water, tapping on the glass walls with its gaping mouth, rings of fearsome teeth on full view.
Having explored its new environment, the lamprey settled onto the pebbles at the bottom of the tank. It will remain on display until March as part of a new exhibition exploring the oft-reviled critters that bite, pierce, scrape and saw their way through flesh to access their favorite food source: blood.
The exhibition, called “Bloodsuckers,” includes displays of other live animals—mosquitoes, ticks and leeches—interspersed throughout the gallery. And dozens of preserved specimens, arrayed down a long, curving wall, offer a glimpse into the diverse world of the roughly 30,000 species of bloodthirsty organisms across the globe. Among these critters are vampire moths, which can pierce the thick skins of buffalo and elephants. Vampire snails target sick and dying fish, making for easier prey. The oxpecker birds of Africa pluck ticks and other insects off large mammals—and then slurp blood from their hosts’ sores.
Sebastian Kvist, curator of invertebrates at the Royal Ontario Museum and co-curator of the exhibition, knows that these animals are likely to make some visitors shudder. But to him, blood-feeders are the loveliest of organisms, the result of a refined evolutionary process. Leeches are a particular favorite of Kvist’s, and his research focuses on the evolution of blood-feeding behavior, or hematophagy, in these predatory worms. Sometimes he even affectionately lets the leeches in his lab gorge themselves on his blood.
“When you have live animals in your care, they demand some respect,” he says. “I think that it is giving back to the leech what we're getting from them to donate our warm blood.”Leeches are still used today in a wide variety of medical procedures, from alternative therapies to FDA-sanctioned surgical uses. (Robertus Pudyanto vi Getty Images)
“Bloodsuckers” opens in a corridor bathed in red light, where an installation featuring three strands of red blood cells dangles from the ceiling. Blood is a hugely abundant food source, so it makes sense that wherever vertebrates exist, animals would arise to steal their life-sustaining fluids. Blood-feeding likely evolved repeatedly over the course of our planet’s history—“perhaps as many as 100 times,” according to Kvist. Bloodsucking creatures have no common ancestor, as the behavior has cropped up independently in birds, bats, insects, fish and other animal groups—a testament to its evolutionary value.
“I can think of no other system that’s [so] intricate that has evolved separately,” Kvist says. “And it makes blood-feeding as a behavior even more beautiful.”
Subsisting on a blood-heavy diet is tricky, however, and relatively few creatures have managed to retain this ability over time. “Thirty thousand [bloodsuckers] out of the roughly 1.5 or 1.6 million species [of animals] that have been described is a very, very small number,” Kvist says. “But it turns out that being able to feed on blood puts tremendous strain on your physiology, on your morphology, and on your behavior.”
For one, blood lacks B vitamins, which all animals require to convert food into energy. Many bloodsuckers thus host microscopic bacteria inside their bodies to provide these essential nutrients. Because blood is so iron-rich, it’s toxic to most animals in large amounts, but habitual blood-feeders have evolved to break it down.Display of an oxpecker, a bird that feeds on the blood of large mammals. (Jesse Milns, Courtesy of the Royal Ontario Museum)
Getting to the blood of a living creature is no mean feat either. Blood-feeding organisms have different ways of accessing their preferred snack. Mosquitoes, for instance, pierce the skin with their long, thin mouthparts, while certain biting flies boast serrated jaws that slash through flesh. But all of these methods risk being met with a deft swat from the host. To counteract this problem, some blood-feeders, like leeches, have mild anesthetics in their saliva, which help them go unnoticed as they feed. Certain creatures like vampire bats, lampreys and leeches also produce anticoagulants to keep their victims’ blood flowing, sometimes even after they’re done eating.
“A leech feeds five times its body weight in blood, up to ten times sometimes,” Kvist says. “If that blood congealed or clotted inside its body, then the leech would fall to the bottom [of the water] like a brick.”
Kvist and Doug Currie, the Royal Ontario Museum’s senior curator of entomology and co-curator of the exhibition, hope museum visitors gain a newfound appreciation for the elegance of bloodsucking organisms. Humans share a long and complicated relationship with blood-feeders. Leeches, for instance, were once seen as a life-saving force, and are in fact still used by medical experts today after certain types of surgery that overfull parts of the body with blood. But at the same time, we are unnerved by creatures that steal blood—a wariness that has persisted for centuries, as suggested by the fearsome bloodsuckers that populate folklore traditions around the world.
A natural history and culture institution, the Royal Ontario Museum also explores how blood-feeding, a trait that exists in nature, has crept into the human imagination and morphed into something fantastical. Monsters abound within the gallery. There are models of the chupacabra, a beast rumored to drain livestock of their blood, and the yara-ma-yha-who, which originated in the oral traditions of Australia and boasts blood suckers on its fingers and toes.
These creatures do not directly resemble any real blood-feeding animal. Instead, they speak to our “innate fear of something taking our life force,” says Courtney Murfin, the interpretive planner who worked with curators to craft the exhibition’s narrative.
Dracula, arguably the most famous of all the fictional bloodsuckers, may have a more tangible connection to the natural world. Legends of vampires predate Bram Stoker’s 1897 novel—visitors can see a first edition copy of the book at the exhibition—but the notion that these undead beings could transform into bats originated with Dracula. Vampire bats, which live in Mexico and Central and South America, feed on the blood of mammals and birds. They were first described in 1810 and documented by Charles Darwin in 1839. The animals may have influenced Stoker’s supernatural count.
Depictions of vampires in today’s popular culture run the gamut from cool to sexy to goofy. We can have fun with them now, Murfin says, because we know they aren’t real. But when vampire lore arose in eastern Europe in the early 1700s, the beasts were a source of true terror. Confusion about normal traits observed in decomposing bodies, like swollen stomachs and blood in the mouth, led to the belief that corpses could rise from their graves to feast on the blood of the living.
“They started digging up graves and staking the people to the ground … so they couldn't stand up at night,” Kvist says.
Fears about losing their blood to vampires did not, however, dampen Europeans’ enthusiasm for bloodletting, an age-old medical practice that sometimes involved applying leeches to the skin. The treatment can be traced back to the ancient world, where it arose from the belief that draining blood helped rebalance the body’s humors: blood, phlegm, yellow bile and black bile. Bloodletting reached its peak in the late 18th and early 19th centuries, when a “leech mania” swept across Europe and America. Pharmacies stored the critters in ornate jars—one is on display at the museum—and Hirudo medicinalis, or the European medicinal leech, was harvested to the brink of extinction.A 19th century “leech jar,” used to hold and display leeches in pharmacy windows. (Jesse Milns, Courtesy of the Royal Ontario Museum)
Bloodletters also had other ways of getting the job done. One corner of the exhibition is packed with a grisly assortment of artificial bloodletting tools: scarificators, which, with the push of a lever, released multiple blades for opening up the skin; glass cups that were heated and suctioned onto the skin, drawing blood to the surface; smelling salts, in case the procedure proved a bit too overwhelming for the patient.
While medical professionals no longer believe that leeching can cure everything from skin diseases to dental woes, leeches are still valued in medicine today. Hirudin, the anticoagulant in leech saliva, is unrivalled in its strength, according to Kvist. It’s synthesized in labs and given to patients in pills and topological creams to treat deep vein thrombosis and prevent strokes. Leeches themselves make appearances in hospitals. They’re helpful to doctors who perform skin grafts or reattachments of fingers, toes and other extremities. Newly stitched arteries heal more quickly than veins, so blood that is being pumped into the reattached area doesn’t flow back into the body, which can in turn prevent healing.
“Stick a leech on, and it will relieve that congestion of the veins,” says Kvist, who also studies the evolution of anticoagulants in leeches.
Earlier this year, Kvist received a call from Parks Canada asking for help with an unusual conundrum. A man had been apprehended at Toronto’s Pearson International Airport with nearly 4,800 live leeches packed into his carry-on luggage, and officials needed help identifying the critters. Kvist took a look at some of the leeches, which appeared to have been smuggled from Russia, and pinpointed them as Hirudo verbana. Because they are threatened by over-harvesting, this species is listed by the Convention on International Trade in Endangered Species of Wild Flora and Fauna, meaning it cannot be transported without a permit. Just what the man was doing with the bloodsuckers is unclear, but Kvist says he claimed to sell them for “New Age medicinal purposes.”
“There is a larger-than-we-think underground network of people that use leeches to treat a variety of ailments,” Kvist says. The Royal Ontario Museum took in around 300 of the contraband critters, and a few dozen are presently lounging in a display tank at “Bloodsuckers.”
While leeches have long been valued for their healing properties—scientifically valid or otherwise—some bloodsuckers are better known for their ability to transmit serious illnesses. Certain species of mosquito, for instance, spread West Nile, Zika and malaria. Ticks transmit Lyme disease. The exhibition does not shy away from exploring the dangers associated with blood-feeders, and it offers advice on how to protect yourself from infection.A visitor views a display of preserved blood-sucking specimens. (Jesse Milns, Courtesy of the Royal Ontario Museum)
“Some fears are real,” Kvist says. “Disease, unfortunately, is a necessary consequence of blood-feeding.”
Most blood-feeding animals, though, do not pose a serious threat to humans. In fact, bloodsuckers are vital to the health of our planet. Mosquitoes are an important food source for birds. Fish eat leeches. Even sea lampreys, which are invasive to the Great Lakes, can bring essential nutrients to the aquatic habitats where they spawn. And like all species, blood-feeders contribute to the Earth’s biodiversity—a richness of life that is fast declining due to factors like pollution, climate change and habitat degradation.
Many, many animal groups need to be part of conversations regarding biodiversity, Kvist says, but he and his colleagues opted to spotlight the bloodthirsty ones. The museum hopes to help visitors feel more comfortable living alongside these animals—even if they aren’t willing to volunteer an arm for a leech’s next meal.