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Found on my deck. We live next to a lake. Don't know if a bird dropped it? Not sure whether to save it? Has scalloped front legs and a point from the end of what I think are wings. Antennae, mouthparts. Back legs either deformed or partly missing because can't propel forward, just rolling side to side I put it in a pen to keep it safe for now.
That is a mole cricket. Order Orthoptera, family, Gryllotalpidae https://en.wikipedia.org/wiki/Mole_cricket I'm not surprised you live by a lake. They burrow in sandy soil or sand, often right up to the water's edge. They can fly, but spend most of their time underground. You do not need to save it, as it will find its way back to its home if you just let it go. They are not pests. They don't bite, or spread disease.
Rising carbon dioxide could leave tiny lake dwellers defenseless
Water fleas (Daphnia pulex shown) raise spiky defenses when sensing predators are near. But too much carbon dioxide in lake water may dull their senses. That could leave the critters at risk of being eaten.
February 13, 2018 at 6:45 am
As people continue to burn fossil fuels, levels of carbon dioxide in the atmosphere have been rising. Some of that excess has dissolved into the world’s oceans. But levels of this greenhouse gas have also been rising in some lakes, a new study finds. Too much of this CO2 in the water may leave some tiny animals in the water too sleepy to fend off predators. This could be a problem because they are an important part of many lake food webs.
These animals are water fleas. Not true fleas, they are a type of tiny crustacean. (As such, they’re related to shrimp and lobsters.) They get their name from the way they appear to jump about in the water. The ones studied here were two different species of pinhead-sized Daphnia (DAFF-nee-uh). They are at the bottom of many freshwater food webs. That means they serve as a primary entrée in the diet of somewhat bigger animals.
Average carbon dioxide levels (straight lines) increased in four German lakes over 35 years (top). (These levels were measured as the partial pressure of CO2 dissolved in the lake water in microatmospheres, a unit of pressure.) Each lake also showed an overall decrease in pH (bottom). L.C. Weiss et al/Current Biology 2018
Long-term measurements of the chemistry of lake water are rare. But researchers found data on four lakes in Germany. Those data covered the period from 1981 to 2015. They showed how much CO2 levels had risen over that time, as pH levels dropped. (pH is a measure of acidity.)
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Rising CO2 in the atmosphere has increased levels of the gas dissolved into Earth’s oceans. That has made them more acidic. Studies show that this ocean acidification alters the behaviors of many species. It’s been less clear whether rising CO2 levels also were affecting lakes and other bodies of freshwater. It also was not clear how freshwater critters might be coping with any change, says Linda Weiss. She’s an aquatic ecologist at Ruhr University Bochum in Germany.
Her team compared the data from the German lakes. Over 35 years, they found, the lakes’ pH fell by an average of 0.01 per year. Carbon dioxide levels increased during that time by a yearly average of 16 microatmospheres. (That is a unit of air pressure.)
And water pH levels fall, the researchers now show, the behavior of the water fleas will change.
The scientists shared these data online January 11 in Current Biology.
To probe the pH effects on water fleas, Weiss and her team studied the crustaceans’ behavior in the lab. Predators that feed on Daphnia include the larvae of phantom midges. While dining on the water fleas, those midges release a chemical. Various species of water fleas respond to the chemical by arming themselves with an array of natural defenses. Some raise forbidding neck spikes. Others grow giant “helmets” that make them tougher to swallow.
Scientists confirm ‘greenhouse’ effect of human’s CO2
But in waters with high CO2, the fleas’ ability to sense the predators appeared dulled. They seemed to grow sleepy and unaware of the chemical signaling hungry midges.
The team tested the critters in waters containing both the scary midge chemical and three different levels of CO2. The scientists measure that gas in units known as microatmospheres (microatm). The lowest level was 2,000 microatm. Although it is considered high, this level is now common in lakes. They then compared this to two higher levels, 11,000 and 16,000 microatm. Both species of flea were less defensive at the higher levels of CO2. They displayed fewer neck spikes or developed smaller crests.
Further tests revealed that the elevated CO2 was responsible. It was not due to the more acidic pH. It’s unclear exactly why higher CO2 levels lower the Daphnias’ defenses. However, the researchers suggest the gas may act as a narcotic and blunt the water flea’s senses.
Explainer: Ocean acidification
The chemistry and environment of lakes can vary widely. As such, Weiss says, it is difficult to draw firm conclusions from the new findings. Many lakes are warming. And many are already saturated in carbon dioxide and now shedding the excess to the air. Others are still absorbing it and becoming more acidic.
Caleb Hasler is a biologist in Canada at the University of Winnipeg in Manitoba. He was not involved in the study. Hasler says it also is unclear how other freshwater species — including predators — might be affected by growing CO2 levels in water.
Occasional studies have looked at, as here, particular species. Maybe they were plankton. Or fish. Or shellfish. And looking at all of these, he says, “The effect seems to be highly variable.”
Still, studies such as the new one on water fleas show that measuring long-term changes in CO2 and biological impacts will be important to understanding ecosystem effects, Hasler says. And for starters, he says, “Showing that there is an impact on an important species is pretty significant.”
acidic An adjective for materials that contain acid. These materials often are capable of eating away at some minerals such as carbonate, or preventing their formation in the first place.
acidification A process that lowers the pH of a solution. When carbon dioxide dissolves in water, it triggers chemical reactions that create carbonic acid.
annual Adjective for something that happens every year.
aquatic An adjective that refers to water.
array A broad and organized group of objects. Sometimes they are instruments placed in a systematic fashion to collect information in a coordinated way. Other times, an array can refer to things that are laid out or displayed in a way that can make a broad range of related things, such as colors, visible at once. The term can even apply to a range of options or choices.
atmosphere The envelope of gases surrounding Earth or another planet.
average (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
behavior The way something, often a person or other organism, acts towards others, or conducts itself.
biology The study of living things. The scientists who study them are known as biologists.
carbon The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.
carbon dioxide (or CO2) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they&rsquove eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas). Carbon dioxide acts as a greenhouse gas, trapping heat in Earth&rsquos atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
chemical signal A message made up of molecules that get sent from one place to another. Bacteria and some animals use these signals to communicate.
chemistry The field of science that deals with the composition, structure and properties of substances and how they interact. Scientists use this knowledge to study unfamiliar substances, to reproduce large quantities of useful substances or to design and create new and useful substances. (about compounds) Chemistry also is used as a term to refer to the recipe of a compound, the way it&rsquos produced or some of its properties. People who work in this field are known as chemists.
crustaceans Hard-shelled water-dwelling animals including lobsters, crabs and shrimp.
Daphnia Also known as water fleas, these are actually small, freshwater crustaceans. They are near the bottom of the food chain, serving as a major energy source for many small fish.
data Facts and/or statistics collected together for analysis but not necessarily organized in a way that gives them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.
defense (in biology) A natural protective action taken or chemical response that occurs when a species confront predators or agents that might harm it. (adj. defensive)
ecology A branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.
ecosystem A group of interacting living organisms &mdash including microorganisms, plants and animals &mdash and their physical environment within a particular climate. Examples include tropical reefs, rainforests, alpine meadows and polar tundra.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of components in some electronics system or product).
food web (also known as a food chain) The network of relationships among organisms sharing an ecosystem. Member organisms depend on others within this network as a source of food.
fossil fuel Any fuel &mdash such as coal, petroleum (crude oil) or natural gas &mdash that has developed within the Earth over millions of years from the decayed remains of bacteria, plants or animals.
freshwater A noun or adjective that describes bodies of water with very low concentrations of salt. It&rsquos the type of water used for drinking and making up most inland lakes, ponds, rivers and streams, as well as groundwater.
greenhouse A light-filled structure, often with windows serving as walls and ceiling materials, in which plants are grown. It provides a controlled environment in which set amounts of water, humidity and nutrients can be applied &mdash and pests can be prevented entry.
greenhouse gas A gas that contributes to the greenhouse effect by absorbing heat. Carbon dioxide is one example of a greenhouse gas.
larva (plural: larvae) An immature life stage of an insect, which often has a distinctly different form as an adult. (Sometimes used to describe such a stage in the development of fish, frogs and other animals.)
midges Any of many types of small flies that often live around water. Some are blood-sucking insects others can derive their energy from eating plants. Frequently mistaken for mosquitoes, midges can transmit disease or move pollutants through an ecosystem.
narcotic A drug (such morphine) or some natural compound that may be prescribed to dull the senses &mdash especially pain &mdash or cause a relaxation to induce deep sleep. Overdoses of these agents may lead to coma, convulsions and death.
pH A measure of a solution&rsquos acidity or alkalinity. A pH of 7 is perfectly neutral. Acids have a pH lower than 7 the farther from 7, the stronger the acid. Alkaline solutions, called bases, have a pH higher than 7 again, the farther above 7, the stronger the base.
plankton A small organism that drifts or floats in the sea. Depending on the species, plankton range from microscopic sizes to organisms about the size of a flea. Some are tiny animals. Others are plantlike organisms. Although individual plankton are very small, they form massive colonies, numbering in the billions. The largest animal in the world, the blue whale, lives on plankton.
predator (adjective: predatory) A creature that preys on other animals for most or all of its food.
pressure Force applied uniformly over a surface, measured as force per unit of area.
species A group of similar organisms capable of producing offspring that can survive and reproduce.
Mayfly Species Ephemerella excrucians (Pale Morning Dun)
For trout (if not anglers), this single species is arguably the most important mayfly in North America. In terms of sheer numbers, breadth of distribution and hatch duration, it has a good argument.
Ephemerella excrucians or Pale Morning Dun usually follows its larger sibling Ephemerella dorothea infrequens with which it shares the same common name. What it often lacks in size by comparison is made up for with it's duration, often lasting for months with intermittent peaks. This close relationship with infrequens has led many anglers to confuse Pale Morning Dun biology with that of the multivoltine ( Multivoltine: Having more than one generation per year. ) Baetidae species, having disparate broods that decrease in size as the season advances. Sharing the same common name has not helped to alleviate this misconception.
Until recently, Ephemerella excrucians was considered primarily an upper MidWestern species of some regional importance commonly called Little Red Quill among other names. Recent work by entomologists determined that it is actually the same species as the important Western Pale Morning Dun (prev.Ephemerella inermis), and the lake dwelling Sulphur Dun of the Yellowstone area, (prev.Ephemerella lacustris). Since all three are considered variations of the same species, they have been combined into excrucians, being the original name for the type species reported as far back as the Civil War. Angler speculation had simmered for some time that the stillwater loving Ephemerella lacustris was much more widespread, inhabiting more water types then previously thought and could account for many large sulfurish ephemerellids found in still to very slow water locations throughout the West. With the revisions, this discussion is now moot.
Ephemerella excrucians variability in appearance, habitat preferences, and wide geographical distribution are cause for angler confusion with the changes in classification. They can be pale yellow 18's on a large Oregon river, creamy orange 14's on western lakes and feeder streams, large olive green on CA spring creeks as well as tiny sulfur ones in many Western watersheds. Then there's the little Red Quill on small streams in Wisconsin. Yet, all are the same species.
Regions: East, Midwest, West
Time Of Year (?): April through October with peaks of a month or more within this period depending on location
Preferred Waters: All water types except warm river systems and infertile high country lakes
Time Of Day (?): Late morning and early evening in the West late afternoon to evening in the East
Habitat: Highly variable, though the greatest concentrations occur in weedy riffles and runs
Water Temperature: Varies with location
Time Of Day: Morning and again at dusk in the West only dusk in the East, where they're not important
Habitat: See notes
Diet: Detritus ( Detritus: Small, loose pieces of decaying organic matter underwater. ) and algae
Current Speed: Slow to fast in the West medium to fast in the East
Substrate: All types, but prefer gravel and cobble with weed growth or the edges of weed beds in spring creeks
08 – Pipevine Swallowtail Caterpillar
Pipevine Swallowtail Caterpillar
By Meganmccarty (Own work) [Public domain], via Wikimedia Commons
The Pipevine Swallowtail is a fascinating fluorescent blue butterfly that is commonly found in Northern and Central America.However, its larvae is a weird creature with tinted visor shades for eyes and a quadruple row of blunt horns covering its body. What’s also interesting about these creatures,is that they feed primarily on the Pipevine, a poisonous plant, and retain the toxins from the leaves in their own body.
Why is it important to evaluate benthic macroinvertebrates?
Benthic macroinvertebrates are commonly used as indicators of the biological condition of waterbodies. They are reliable indicators because they spend all or most of their lives in water, are easy to collect and differ in their tolerance to pollution. Macroinvertebrates respond to human disturbance in fairly predictable ways, are relatively easy to identify in the laboratory, often live for more than a year and, unlike fish, have limited mobility. In fact, because they cannot escape pollution, macroinvertebrates have the capacity to integrate the effects of the stressors to which they are exposed, in combination and over time. Biologists have been studying the health and composition of benthic macroinvertebrate communities for decades.
Tube-dwelling sea creatures may be oldest known parasites
Tubes housing sea creatures (white) are anchored to a clam-like animal in this artistic graphic. Analysis of fossils from 512 million years ago suggest the tube-dwellers may have stolen food from the mouths of their hosts.
Zhifei Zhang/Northwest Univ.
More than 500 million years ago, tube-dwelling creatures spent their lives stuck to the shells of clam-like sea animals called brachiopods (BRAK-ee-oh-podz). Scientists now believe those tube dwellers may be the earliest known parasites.
Parasites are organisms that must live in or on other organisms to stay alive. And their host pays a price.
Explainer: How a fossil forms
Usually, parasites don’t become fossils, says Tommy Leung. That’s because their bodies are often small and soft, he explains. Leung is a parasite specialist who did not take part in the new study. He works at the University of New England in Armidale, Australia.
Parasites are “an integral part of life on Earth,” he says. But it’s been hard to tell when the parasite lifestyle emerged. It likely was very, very long ago, he notes. Today, he notes, “Practically every living thing has some kind of parasitic thing living on or in them.”
Five years ago, scientists reported finding one early parasite. It was a type of tongue worm. Fossils showed that these organisms lived on sea crustaceans some 425 million years ago. Earlier fossils had only hinted at possible parasites.
Scientists Say: Fossil
Now, a fossil bed of brachiopods in Yunnan, China, offers strong evidence for parasites from almost 100 million years earlier. Zhifei Zhang is a paleontologist at Northwest University in Xi’an, China. He was part of a team that described these parasites June 2 in Nature Communications. The fossilized animals they studied date back to 512 million years ago.
Thousands of brachiopod fossils at the site had been clustered in sediment once covered by the sea. Hundreds of them had tube-shaped structures anchored to the outside of their shells. The mouthlike parts of the tubes fanned out along the shell’s opening edges. These tubes appeared only on brachiopods — never alone or on other animals. This suggests that the tube-dwelling creature needed the brachiopod to survive.
This fossilized clam-like sea animal is encrusted with tubes that housed a possible type of tube-dwelling parasite. Zhifei Zhang/Northwest Univ.
The brachiopods were likely filter feeders. That means they caught whatever food drifted into their open shells. Zhang and his colleagues wondered if the tube-dwellers had been snatching food at the shell’s edge, before the brachiopod could eat it. If true, then tube-covered brachiopods would get less food. And that means they should weigh less than brachiopods without the tube dwellers.
To investigate, Zhang’s group estimated the mass of brachiopods with and without tubes. Tube-free ones almost always were heavier than their tube-covered companions. And that was true regardless of how many tubes were present.
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The study “demonstrates these organisms had an intimate association,” says Leung. But he isn’t convinced their relationship was truly parasitic. Brachiopods with more tubes should be worse off, he says. In fact, that wasn’t true. While brachiopods with tubes were smaller, Leung says, this might not be due to parasitism. Instead, the tube creatures might just have preferred to anchor onto smaller shells.
Brachiopods hosting tube dwellers might become stressed only when food becomes scarce, for instance. Or it could be that the tube dwellers catch food that would be too small for the brachiopods. “With these kinds of relationships, the answer isn’t always that this is good or bad,” Leung says. They tend, he says, to be “more complicated than that.”
colleague: Someone who works with another a co-worker or team member.
crustaceans: Hard-shelled water-dwelling animals including lobsters, crabs and shrimp.
filter: (n.) Something that allows some materials to pass through but not others, based on their size or some other feature. (v.) The process of screening some things out on the basis of traits such as size, density, electric charge.
filter feeder: A water-dwelling animal that collects its nutrients or prey by filtering them out of the water. Some of the best known examples are bivalves, such as clams and mussels.
fossil: Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.
host: (in biology and medicine) The organism (or environment) in which some other thing resides. (v.) The act of providing a home or environment for something.
organism: Any living thing, from elephants and plants to bacteria and other types of single-celled life.
paleontologist: A scientist who specializes in studying fossils, the remains of ancient organisms.
parasite: An organism that gets benefits from another species, called a host, but doesn’t provide that host any benefits. Classic examples of parasites include ticks, fleas and tapeworms.
sea: An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.
sediment: Material (such as stones and sand) deposited by water, wind or glaciers.
shell: The protective, hard outer covering of mollusk or crustacean, such as a mussel or crab.
Journal: Z. Zhang et al. An encrusting kleptoparasite-host interaction from the early Cambrian. Nature Communications. Published online June 2, 2020. doi: 10.1038/s41467-020-16332-3.
Journal: D.J. Siveter et al. A 425-million-year-old Silurian Pentastomid Parasitic on Ostracods. Current Biology. Vol. 25, June 15, 2015. doi: 10.1016/j.cub.2015.04.035.
About Jonathan Lambert
Jonathan Lambert is the staff writer for biological sciences, covering everything from the origin of species to microbial ecology. He has a master’s degree in evolutionary biology from Cornell University.
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Hovering Hawkmoths Slow Down Their Brains to See in the Dark
Finding food in the dark requires some skill, especially if you’re a hawkmoth. These insects slurp flower nectar with a long mouthpart akin to a giant bendy straw—all while hovering in midair as their food sources sway in the breeze.
“Doing all of that in light levels where I wouldn’t be able to see the hand in front of my face, that’s a pretty remarkable behavior for an animal with a brain much smaller than a pea,” says Simon Sponberg, a neuromechanist at Georgia Tech. Now, Sponberg and his colleagues have found that hawkmoths have adopted an unusual trick to achieve such a feat of the senses: Under low light conditions, the insects can actually slow down the way their brains process light. While this comes at a cost—a slower reaction time—the insects mostly feed on flowers that move at just the right speed.
“They actually avoid a trade-off, because they get the additional sensitivity of slowing down their visual systems, but they don’t slow it down to where they would do really poorly at tracking the natural flowers that they care about,” explains Sponberg. “They’re very attuned to their environment.”
Hawkmoths have compound eyes made up of facets called ommatidia. These are covered in sheaths that bend specific wavelengths of light to hit small bundles of visual nerve cells, which then send signals to the brain. The brain compiles a mosaic from the wealth of signals to create an image. In the dark, the sheath pulls back, and the eye absorbs as many wavelengths of light as possible.
“The mechanism is different, but the effect is sort of like widening the aperture of a camera," says Sponberg. "It collects light over a larger region of space,” making for a brighter picture. However, this effect is not enough to let the moth truly see in the dark. “It allows the moths to see about a thousand times better than they would normally be able to see in terms of light sensitivity. But that’s way insufficient for being able to see at night,” says Sponberg.
Some neuroscientists had suggested that the insects, which do most of their feeding at dusk, might actually be slowing down their light perception—a bit like slowing the shutter speed on a camera to expose an image longer. “The animal would integrate light for a longer period of time so that it could collect more light and be more sensitive to dimly lit objects,” says Sponberg.
To investigate, Sponberg’s lab built robotic flowers that could sway at controlled speeds. The team monitored how hawkmoths responded to flowers moving at different speeds and in varying light levels. By calculating the insects' reaction times, the researchers saw that the moth motions matched up with mathematical models of slower brain processing. On average, the moths responded to floral motion 17 percent slower in the dark. The moths’ ability to track the swaying flowers seemed to cap at 2 Hertz, or two sways per second. Anything higher and they missed their target, the team reports today in Science.
Seen from above, a hawmoth moves with a swaying robotic flower as it feeds. The video has been slowed down four times to better see the moth's motion. (Sponberg Lab, Georgia Tech)
The researchers aren’t exactly sure which neurons are slowing down in the insects' brains. The moths aren’t changing the way they move, though, so the speed adjustments must be happening in the part of the brain that controls vision. “It’s not just how fast they can see, it’s how fast they can accelerate back and forth—the combination of both the physics of their brain and the physics of their body,” says Sponberg.
So is the moths' speed limit arbitrary, or does it have actual implications in the wild? The team selected flowers frequented by hawkmoths. Outside, they recorded videos of the flowers moving and tracked their speed. Flowers don’t just sway at a nice, steady speed. However, the team found that whether they were blowing to one side or moving back and forth, the flowers weren’t moving faster than 2 Hertz at least 90 percent of the time.
This time seen from the side, a hawkmoth tracks a robotic flower under dim light. Slower moving flowers proved easier for the moths to track. (Sponberg Lab, Georgia Tech)
When these moths slurp up nectar, they also pollinate the plant. In the pollination game, the sights and smells of certain plants have often evolved to be finely tuned to the senses of their preferred pollinator. The new work suggests that motion may be just as coordinated. But whether it's the flower or the insect that sets limits on this relationship remains unclear. “It would be difficult to prove, either way,” notes Eric Warrant, a zoologist at Lund University in Sweden, who also wrote a perspective piece on the study.
Down the line, understanding hawkmoth vision and flight could have applications in robotics, notes Noah Cowan, an engineer at Johns Hopkins University. The findings could “provide clues as to how to build a better control system or flight system,” he explains.
And from a basic biology perspective, “the fact that the moths slow down just enough to still respond to the speed of moving flowers is really cool, and it shows how well the moth brain is adapted to its environment,” adds Jessica Fox, a neuroscientist at Case Western Reserve who was not affiliated with the study. Plenty of other insects have to navigate diverse light environments—from fruit flies to nocturnal bees and wasps. While these bugs might not have adapted their visual processing in exactly the same way, it’s possible that other animals employ similar strategies.
“The hawkmoth is the first animal in which we've seen this strategy," says Fox, "but I bet it won't be the last.”
About Helen Thompson
Helen Thompson writes about science and culture for Smithsonian. She's previously written for NPR, National Geographic News, Nature and others.
Hot, Hot Cities
Why is it so hot in the city, anyway? Urban areas are usually hotter than rural areas because of something called the urban heat island effect. The urban heat island effect is due to a decrease in plants and an increase in concrete, like sidewalks and streets that cover the land in urban areas. When the sun shines on a city, the concrete absorbs heat. All of that trapped heat is then slowly released, which means that the city stays hot even after the sun goes down.
'Resurrecting' tiny lake-dwelling animals to study evolutionary responses to pollution
A University of Michigan biologist combined the techniques of "resurrection ecology" with the study of dated lake sediments to examine evolutionary responses to heavy-metal contamination over the past 75 years.
To accomplish this, Mary Rogalski hatched long-dormant eggs of Daphnia, tiny freshwater crustaceans also known as water fleas, that accumulated in the lake sediments over time.
After rearing the critters in the lab, she exposed them to various levels of two heavy metals to see how their sensitivity to the environmental contaminants changed over time. Surprisingly, she found that sensitivity to copper and cadmium increased as the levels of those toxic metals rose in the lakes she studied.
"These findings are unexpected because evolutionary theory predicts that a population should adapt quickly to a stressor like this and become less sensitive to it, not more sensitive to it. It is difficult to explain the results of this study," said Rogalski, a postdoctoral researcher in the U-M Department of Ecology and Evolutionary Biology.
In one of the lakes, Daphnia hatched from sediments dating to around 1990 -- when copper contamination was at its peak -- were 46 percent more sensitive to copper exposure than individuals from the 1940s, a period with lower levels of copper contamination.
Rogalski reports her finding in a study published online Feb. 16 in the journal The American Naturalist. The study was part of her dissertation research at the Yale University School of Forestry & Environmental Studies and involved fieldwork at three Connecticut lakes.
Scuba divers collected 5-inch-diameter sediment cores from the lake bottoms. Rogalski then estimated sediment ages based on the presence of radioactive materials and measured concentrations of copper and cadmium in the layers back to the late 1800s.
Copper contamination in the lakes was largely due to yearly applications of copper sulfate to control nuisance algae. The cadmium likely came from industrial and agricultural development in the region over the past century.
In the lab, Rogalski isolated dormant or "diapausing" Daphnia ambigua eggs from various dated sediment layers, then hatched and raised them. She measured Daphnia's changing sensitivity to copper and cadmium by exposing them to various levels of the metals in glass flasks and determining the median lethal concentration.
In one Connecticut lake where copper contamination has declined recently, she found that Daphnia remain sensitive to the metal 30 years after peak exposure. An adult Daphnia is about the size of a very coarse grain of sand.
"It is difficult to know what mechanisms are driving this evolutionary pattern," Rogalski said. "Even so, this research suggests that we need to do more to uncover both the drivers and implications of maladaptation in nature."
Paleolimnology is the study of ancient lakes from their sediments and fossils. The branch of experimental paleolimnology that Rogalski used in this study has been dubbed "resurrection ecology" by its practitioners.
Human activities can drive strong and rapid evolutionary changes in wild animal populations. Those evolutionary responses often leave the population better able to cope with the new environmental conditions, a process called adaptation through natural selection.
For example, a newly introduced pesticide may kill the vast majority of the insects it targets. But the survivors can then give rise to a pest population that is resistant to the chemical.
But some populations fail to adapt to changing environments or can wind up worse off than they were beforehand, an occurrence known as maladaptation.
Maladaptive outcomes are less common than adaptive one and are less studied. In many cases, it is impossible to examine a population's response to a stressor over multigenerational timescales without conducting a long-term study that could take decades to complete.
The Daphnia crustacean, with its diapausing eggs, provides a time machine of sorts, allowing researchers to examine long-term evolutionary responses to environmental stressors by reviving and rearing dormant organisms trapped in lake bottoms.
"Daphnia offer a system where examining historic evolutionary trajectories is possible," Rogalski wrote in The American Naturalist. "Hatching diapausing eggs from dated lake sediments and culturing clonal lineages in the lab allows us to examine how populations change through time and the genetic basis underlying those changes."
Interesting Insights from the Water Dragon!
While the water dragon has a mythical name, it is actually a perfect species to explain several different biological concepts that are very real.
Though the human pineal gland is buried deep within our brains, it is connected to neurons in the eye. When our eyes perceive light, a signal is sent to the pineal gland. This signal causes the pineal gland to stop producing melatonin, a hormone crucial to our sleep and wake cycles. When no or very little light is detected by the pineal gland, it again starts to release melatonin. This hormone affects many parts of your brain and body – preparing you for sleep! This helps regulate our circadian rhythm and keeps our bodies healthy.
Parthenogenesis is an ability that some animals have to reproduce asexually, even though the species is normally sexually reproducing. Through parthenogenesis, a female is able to create viable offspring – without ever having been fertilized by a male. Essentially, this is equivalent to a virgin birth!
The water dragon is one of only a few species that has been observed completing parthenogenesis. Through this process, an unfertilized egg goes through a duplication event to become a diploid cell. If the female’s genetics do not contain a large number of deleterious recessive mutations, the offspring can be viable. Studies on water dragons have shown that parthenogenesis does occur, and genetic analysis showed that these offspring were almost identical to the female they came from.
Interestingly, parthenogenesis is seen in a number of other reptiles including garter snakes, Colombian rainbow boas, and common boas. However, it is much more common in invertebrates like insects, snails, worms, and microscopic organisms. Still, parthenogenesis has been seen in birds, sharks, and other groups – though it is usually limited to a single species and is incredibly rare.