Stories tagged Biological Populations Change Over Time

Aug
18
2014

Hallucigenia sparsa fossil: from the Burgess Shale
Hallucigenia sparsa fossil: from the Burgess ShaleCourtesy M. R. Smith / Smithsonian Institute
One of the strangest and more mysterious critters that scurried across the Middle Cambrian seafloor has baffled paleontologist since it was first identified in the 1970s. Was it a worm? Which side was up? Did it have legs or spikes or both? Was its head actually its tail? Did it have any extant descendents or was it an evolutionary dead-end? The worm-like creature was so baffling and so bizarre, it was given the very apropos name of Hallucigenia.

The tubular, spiked-worm possessed seven or eight pairs of legs and ranged in length from 2/5th of an inch to one and 1/4 inches and looks like something out of a bad dream. Early interpretations of their fossils were all over the map. The stiff spikes on it back were first thought to be its legs, and its legs misidentified as tentacles. What was thought to be its tail ended up being its head.

Using modern imaging technology, researchers from the University of Cambridge have been closely studying fossils from the famous Burgess Shale quarry located high in the Canadian Rockies, and are uncovering Hallucigenia's secrets. By studying the claws at the end of its legs they have been able to link it to modern velvet worms (onychophorans). Scientists have long suspected the two were somehow related but until now have failed to find anything significant to prove it. By studying Hallucigenia's claws they've determined that they're constructed of nested cuticle layers, very similar to how the jaws of velvet worms are organized. The similarity is no surprise since jaws are known to have evolved from a modified set of front legs.

But besides giving Hallucigenia a place in the lineage of life on Earth, the Cambridge team during the course of their study also discovered something else: that arthropods - which include crustaceans, spiders, insects and trilobites - aren't in fact as closely related to velvet worms as previously thought.

“Most gene-based studies suggest that arthropods and velvet worms are closely related to each other," said co-author Dr Javier Ortega-Hernandez. "However, our results indicate that arthropods are actually closer to water bears, or tardigrades, a group of hardy microscopic animals best known for being able to survive the vacuum of space and sub-zero temperatures – leaving velvet worms as distant cousins.”

SOURCE and LINKS

University of Cambridge story
Previous Buzz Post on Hallucigenia
The Cambrian Explosion
More about Tartigrade

Oct
07
2013

Enrolled trilobite: The trilobite's strategy of rolling itself up into a ball for protection dates back to some of its earliest known ancestors in the fossil record. This fossil trilobite (Isotelus?) was found in Late Ordovician shale in St. Paul, Minnesota.
Enrolled trilobite: The trilobite's strategy of rolling itself up into a ball for protection dates back to some of its earliest known ancestors in the fossil record. This fossil trilobite (Isotelus?) was found in Late Ordovician shale in St. Paul, Minnesota.Courtesy Mark Ryan
A new study appearing in Biology Letters shows that trilobites - everyone's favorite prehistoric water bug - developed an effective survival strategy much earlier than previously thought.

Trilobite fossils from Early Cambrian rock formations in the Canadian Rockies and elsewhere lend evidence that some of the earliest trilobites used enrollment (i.e rolling themselves up into a ball like an armadillo) to protect themselves from predators or the environment. Trilobite fossils found here in Minnesota are several million years younger dating back to the Late Cambrian through Late Ordovician Periods (500 - 430 mya) and are often found enrolled. It was an effective survival strategy.

Trilobites were arthropods, which meant they possessed exoskeletons, segmented bodies and jointed appendages. Their closest extant relative is the horseshoe crab. Trilobite bodies - for the most part - were comprised of a head (cephalon) positioned on a body (thorax) that was divided into three lobes: essentially an axial dividing a left and right pleura, and a tail (pygidium). The mouth (hypostome) was located on the underside. It's thought that most early trilobites were predators and/or scavengers who spent their lives roaming the sea floors looking carcasses, detritus or living prey to feed upon. Most trilobites possessed complex eyes (although some were eyeless). Like other arthropods (e.g. today's lobsters), trilobites would outgrow their exoskeletons, discarding them (molting) as they grew in size or changed shape. Their newly exposed soft skin soon hardened into a new, tough, outer casing. Once hardened, their segmented exoskeletons (composed of calcium carbonate) were ventrally flexible, giving them the ability to roll up into a ball should they need sudden protection from whatever threatened them.

Some early trilobite forms from Middle Cambrian-aged fossils had been viewed as incapable of enrolling but the new research based on much older fossils found in mudstones in the Canadian Rockies in Jasper Park pushes back the origins of the strategy to some of the earliest trilobites to appear in the fossil record (Suborder Olenellus). These appeared 10-20 million years earlier at the very beginnings of the Cambrian Period and show evidence of having already developed the ability to enroll.

Trilobites in some form or another existed across a span of more than 270 million years, a very successful run by any measure. The enrollment strategy certainly contributed to their longevity. Although trilobites were already in decline, the last of their kind were wiped out in the great extinction event that marked the end of the Permian Period and the start of the Triassic. They weren't the only casualty of the extinction: nearly 90 percent of Earth's species were terminated along with them.

Even though trilobites are extinct (they died out in the Permian Mass Extinction along with around 90 percent of Earth's species) they were an extremely successful and adaptable life form. No wonder they remain today a favorite among fossil collectors.

SOURCE and LINKS
Paper at Biology Letters
Major Trilobite features
A Guide to the Orders of Trilobites

Jun
05
2013

Does this make my feet look baboonish?: Some folks among us have more ape-like feet than others.
Does this make my feet look baboonish?: Some folks among us have more ape-like feet than others.Courtesy Mark Ryan
A recent study of visitors to the Boston Museum of Science has revealed that some humans - about 1 in 13 - have feet that are ape-like in their structure.

Our great-ape cousins such as chimpanzees have feet that are very flexible in their middle region due to something called the midtarsal break that allows their feet to bend in the middle, enabling them to grasp at branches for easier climbing through trees. So when a chimp lifts his foot off the ground, it just flops about - there's nothing to hold the bones together. Most humans, on the other hand (or should I say foot?), have the same joint but have ligaments that stretch across it making the foot more rigid and stable for upright walking. Australopithecus sediba, a human ancestor that lived 2 million years ago, has a foot structure that is more ape-like than human, so somewhere along the line our feet evolved probably to accommodate our bipedalism.

The study was done by Jeremy DeSilva, a functional morphologist from Boston University, whose main interest is the evolution of the human foot and ankle. In this recent study, museum visitors were requested to walk barefoot across a mechanized carpet while DeSilva's team observed their gaits and the structure of their feet as they walked.

The surprising results showed that 8 percent of the nearly 400 participants possessed a flexible midtarsal break in their foot, and displayed a pressure signature in their footprint that looked like that found in the footprints of non-human primates. Perhaps more surprising is the fact that those subjects who had the unusual foot-joint structure weren't even aware of it until DeSilva revealed it to them.

The study was published in the American Journal of Physical Anthropology.

SOURCES
BBC.com story
Popsci.com story
Jeremy DeSilva cv

Apr
29
2013

Coelacanth: model in the SMM paleo lab. Photo by Mark Ryan.
Coelacanth: model in the SMM paleo lab. Photo by Mark Ryan.Courtesy Fancy Horse (underwater background)
The genome of the coelacanth, the world's best known living fossil, has been sequenced by an international team of researchers and is revealing something scientists already suspected: that the primitive-looking fish has evolved more slowly than most other organisms. The coelacanth is related to the lungfish and several extinct Devonian fish species that are considered precursors to land dwelling tetrapods. Kerstin Lindblad-Toh is senior author of the study which appeared recently in the science journal Nature.

"We often talk about how species have changed over time, but there are still a few places on Earth where organisms don't have to change, and this is one of them," Lindblad-Toh said. "Coelacanths are likely very specialized to such a specific, non-changing, extreme environment -- it is ideally suited to the deep sea just the way it is."

Lindblad-Toh is scientific director of the Broad Institute's vertebrate genome biology group in Cambridge, Massachusetts, which did the genome research. The institute is linked to both MIT and Harvard.

The genetic map, which involved sequencing some 3 billion letters of DNA, also showed (via RNA content) that tetrapods - four-legged land dwelling animals - though related to both coelacanths and lungfish, are more closely related to lungfish and followed that line rather than that of the coelacanth. We humans also branched off that same line. The genome of a lungfish is composed of over 100 billion DNA letters, making it a much more difficult task to sequence, so for the time being, the coelacanth's DNA makes for a reasonable alternative for study.

"This is just the beginning of many analyses on what the coelacanth can teach us about the emergence of land vertebrates, including humans, and, combined with modern empirical approaches, can lend insights into the mechanisms that have contributed to major evolutionary innovations," said professor Chris Amemiya at the University of Washington, and the paper's co-author.

Fossil coelacanth: not much has changed in 350 million years.
Fossil coelacanth: not much has changed in 350 million years.Courtesy photo by Haplochromis via Wikipedia Creative Commons
When Louis Agassiz named the first fossil coelacanth back in 1836, the Swiss paleontologist probably never imagined that a nearly identical descendent of the primitively constructed Devonian-aged fish would one day be found still inhabiting the world's oceans. The coelacanth was thought to have gone extinct along with the non-avian dinosaurs at the end of the Cretaceous period. None have been found in the fossil record after that time, but two extant species are known today. The first specimen Latimeria chalumnae was netted off the coast of South Africa in 1938, near the Chalumnae river and retrieved by East London Museum curator Marjorie Courtenay-Latimer who discovered what she called "the most beautiful fish I'd ever seen" in the catch of local fisherman, Henrik Goosen. Since then several more coelacanths have been caught, including the Indonesian species, Latimeria menadoensis, from the Indian Ocean.

The remarkable prehistoric throw-back, sometimes referred to as "old four legs" because of its leg-like fins, hasn't changed much in its 350 million year history. A member of the clade of lobe-finned fishes called Sarcopterygii, coelacanths retain primitive characteristics such a notochord, a hollow fluid-filled tube made of cartilage that underlies the spine over the length of its body. In all other vertebrates, the notochord is an anatomical structure that appears briefly only during the embryonic stage but not in adults. Not so with the coelacanth. It also possesses, primitive shark-like intestines, a linear heart, and tightly-woven armor-like scales (known as cosmoid) that are only found on extinct species of fish. The coelacanth's brain case contains only 1.5 percent gray matter - the other 98.5 percent of space is filled with fat. The other end of the coelacanth body begins to taper before expanding into a strange, three-lobed tail. Its most notable features are its lobed pectoral and pelvic fins that are structured with bones that look like toes, and move in an alternating tetrapod manner. An electroreceptive rostal organ located in its snout is used to detect prey, and the coelacanth is the only living animal that can unhinge a section of the its cranium to increase the gape of its mouth, enabling it to consume larger prey.

The blue or brown, white-speckled coelacanths prefer deep-water environments, and can reach six and a half feet in length and weigh upwards to 175 pounds. For some reason no living coelacanth has managed to survive more than a single day in captivity. With a dwindling population estimated at only 500-1000 individuals, the coelacanth was declared an endangered species in 1989.

SOURCE and LINKS

Broad Institute news
Coelacanth info at dinofish.com
More coelacanth info
NatGeo article
Take Nova's Coelacanth Quiz

Feb
25
2013

OMG! Can nothing stop them?: According to a new study, mosquitoes, those buzzing, biting, itch-producing flying pests that make life miserable for many of Earth's inhabitants (mainly we humans), can easily adapt to Deet, one of the commonly used ingredients in insect repellents.
OMG! Can nothing stop them?: According to a new study, mosquitoes, those buzzing, biting, itch-producing flying pests that make life miserable for many of Earth's inhabitants (mainly we humans), can easily adapt to Deet, one of the commonly used ingredients in insect repellents.Courtesy Mark Ryan (with photo help from NASA)

We've all seen them, those great B-films where a giant, vicious monster from under the sea, or invaders from outer space arrive to cause mayhem across our cities and generally mess up our way of life. In the end, it seems no matter who or what it was that was attacking us, be it Mothra, Godzilla, or some race of belligerent extra-terrestrials, we could always count on the military to save our collective behind.

Unfortunately, with mosquitoes, that might now be the case anymore.

Scientists are reporting that Deet, one of the most widely used active ingredients in insect repellents, loses its effectiveness against mosquitoes shortly after those ubiquitous, blood-seeking winged vermin are first exposed to it.

Deet - the common name for N,N-diethyl-meta-toluamide - was developed by the US Army after the Second World War to help combat insects during jungle warfare. It was used extensively in the Korean and Vietnam wars, but mosquitoes seem to be able to adapt quickly to it.

"Mosquitoes are very good at evolving very very quickly", said Dr. James Logan of the London School of Hygiene and Tropical Medicine and co-author of the study. "There is something about being exposed to the chemical that first time that changes their olfactory system - changes their sense of smell - and their ability to smell Deet, which makes it less effective."

So what I want to know is where does that leave us here in Minnesota where the mosquito constantly competes with the Common Loon for the title of State Bird? Maybe it's time to start digging the bunker in the backyard.

SOURCE and LINKS
BBC Science news
Original study at Plos One
The Life Cycle of the Mosquito
All about mosquitoes on NatGeo

Sep
26
2012

Dead zombie bee: Up to 80 percent of bee hives along the West Coast may be impacted by the "zombie bee" phenomenon. Parasite flies plants inside the bees, like this one, that ultimately kill them.
Dead zombie bee: Up to 80 percent of bee hives along the West Coast may be impacted by the "zombie bee" phenomenon. Parasite flies plants inside the bees, like this one, that ultimately kill them.Courtesy wintersixfour
Zombies are all the rage these days, and not just on cable TV shows or at pub crawls.

There's a growing trend in "zombie bees" working its way around the West Coast. Just this week beekeepers in Washington state report finding evidence of "zombification" of their bees.

The impacted bees get their name for their changing behaviors once they host the parasitic flies that cause the trouble. While most bees spend their nights nestled snuggling in a comb, these "zombie bees" actually go out flying in very erratic patterns. Like many other night bugs, the zombie bees fly to light and usually die quite soon.

What's really at play is that the tiny parasitic flies plant eggs into the host bee. Those eggs grow into maggots that eat the inside of the host bee that ultimately cause its demise.

Evidence of zombie bees was first found in 2008 near Sacramento, Calif., and beekeepers around the west coast have seeing the spread of the problem in the years since.

Researchers are trying to figure out if this parasite problem is a factor in the bee population declines that have been going on nationwide. One researcher has set up a website – ZombeeWatch.org – to allow amateur beekeepers to share information about zombie bees they are finding around their hives. It is also looking for people who want to step forward to be "zombee hunters."

There has been one isolated report of zombie bees in South Dakota. So far, two investigations in Minnesota have turned up no evidence of zombie bees.

May
02
2012

Cumulative impact by humans on the ocean
Cumulative impact by humans on the oceanCourtesy National Center for Ecological Analysis and Synthesis
One of the great extinctions in Earth history occurred 252 million years ago when about 95 percent of all marine species went extinct. The cause or causes of the Great Dying have long been a subject of much scientific interest.

Now careful analyses of fossils by scientists at Stanford and the University of California, Santa Crux offer evidence that marine animals throughout the ocean died from a combination of factors – a lack of dissolved oxygen, increased ocean acidity and higher water temperatures. What happened to so dramatically stress marine life everywhere?

Geochemical and fossil evidence points to a dramatic rise in the concentration of carbon dioxide in the atmosphere, which in caused a rapid warming of the planet and resulted in large amounts of carbon dioxide dissolving into the ocean and reacting with water to produce carbonic acid, increasing ocean acidity. The top candidate for all this carbon dioxide? – huge volcanic eruptions over thousands of years in what is now northern Russia.

Why should the Great Dying be of more than just academic interest? Humans currently release far more carbon dioxide into the atmosphere than volcanoes and we are releasing carbon dioxide into the atmosphere at a rate that greatly exceeds that believed to have occurred 252 million years ago. The future of Earth’s oceans will be determined by human decision making, either by default or by design. What do we want our future ocean to be?

Mar
06
2012

Iridescence is usually a vanity thing in nature; birds and butterflies, for instance, use it to attract mates. This is Golden Mole: The tiny structures that help streamline the mole and make it water-repellant also give it its iridescence.
Golden Mole: The tiny structures that help streamline the mole and make it water-repellant also give it its iridescence.Courtesy Killer18
the type of thing that would be completely lost on a blind mole...or is it? In the case of the golden mole, iridescence is very much a part of its appearance, but according to a new study about the structure of hair, this iridescence takes on a more functional role. The nano-sized structures on the flattened, paddle-shaped hairs not only give the moles a lovely sheen (for animals that can actually see them), but may also help to repel water and streamline the moles as they move through the sand. This is definitely a case of function over form.

Jan
11
2012

Yesterday, I had the pleasure of attending Environmental Initiative's 2012 Legislative Preview, part of their Policy Forum series.

Basically, a bipartisan group of legislators discussed their environmental priorities with a diverse audience of public, private and nonprofit representatives for the purpose of providing

"a valuable first look at the most pressing environmental issues facing the state in anticipation of the upcoming legislative session."

MN Most Wanted: Asian carp, aquatic invasive species
MN Most Wanted: Asian carp, aquatic invasive speciesCourtesy State of Michigan

The biggest surprise to yours truly was the prevalence of carp among the discussion. Asian carp, AIS (aquatic invasive species), etc., etc.. Everyone appeared in agreement regarding the threat posed by carp, so the real question is what do we do about their impending invasion?

One repeated suggestion was to fund more research, specifically at the University of Minnesota. This is probably an important step towards defending our state waterways, and I think this story helps illustrate why:

"As yet, no technology can stop these downstream migrations; neither grates nor dangerous, expensive electrical barriers do the job.

But a wall of cheap, harmless bubbles just might—at least well enough to have a significant benefit."

Researchers at the U of MN have discovered that bubble barriers may deter 70-80% of carp migration. It's not the visual affect of the bubbles that prevents all but the most daring carp from penetrating the barrier, rather the noise -- equivalent to what you or I would experience standing about three feet from a jackhammer.

The bubble barrier has currently only been tested on common carp, but researchers involved in the experiment want to test the technology on Asian carp next.

In addition to the bubble barrier, U of M researchers are investigating whether Asian carp pheromones can be used to lure them into traps.

Oct
26
2011

Danse Macabre: Artwork Inspired by the Black Plague.
Danse Macabre: Artwork Inspired by the Black Plague.Courtesy Wikimedia Creative Commons
Halloween is coming up soon and what better way to scare the tar out of everybody than with another Black Plague story.

Researchers from Germany and Canada have now determined that the pathogen existing today that infects the human population with bubonic plague is the same one that caused the horrific pandemic known as the Black Plague (aka Black Death) during the Middle Ages,

In the 14th century (1347-1351) the the plague devastated much of Europe. It was brought on by the bacterium Yersinia pestis and thought to have originated in China. Rats, infested with fleas carrying the bacteria, spread the fatal pathogen via the trade routes and across Europe, wiping out one-third of the human population. This is a conservative estimate; some claim as much as 60 percent of the population was eradicated!

Whatever the case, imagine even a third of all your acquaintances, friends, and relatives suddenly dying from what one 14th century chronicler described as “so virulent a disease that anyone who only spoke to them was seized by a mortal illness and in no manner could evade death.”

And it was an extremely horrible death, to say the least, as Michael Platiensis makes clear in his writings from 1357:

“Those infected felt themselves penetrated by a pain throughout their whole bodies and, so to say, undermined. Then there developed on the thighs or upper arms a boil about the size of a lentil which the people called "burn boil". This infected the whole body, and penetrated it so that the patient violently vomited blood. This vomiting of blood continued without intermission for three days, there being no means of healing it, and then the patient expired.“

[Above quoted in Johannes Nohl, The Black Death, trans. C.H. Clarke (London: George Allen & Unwin Ltd., 1926), pp. 18-20]

The Black Plague was the second of three great waves of plague that raged across Europe during historical times. The first, known historically as the Plague of Justinian, took place in the 6th century and affected the Byzantine Empire and much of Europe. The last major wave, known as the Great Plague of London, killed about 100,000 of the city’s population in 1664-65. In the two centuries that followed, waves after wave of the plague continued to devastate the European population although on a lesser scale. These outbreaks although sometimes as virulent, were often more isolated regionally or within a city and kept Europe’s population from rebounding for a good century and a half.

The plague presents itself in three ways: bubonic, septicemic, and pneumonic. All three infections are caused by Y. pestis. With bubonic plague, the lymph nodes become painfully swollen into what are termed buboes – hence the name bubonic. Scepticemic plague, the rarest of the three forms, infects the blood. Both bubonic and scepticemic, if left untreated, result in death between 3-7 days after infection. Pneumonic is the most contagious since it infects the lungs and is easily spread through the air in a spray of water droplets. It’s also the most lethal and usually kills its victims in one to three days. Each form can present itself on its own or can progress into all three. It’s thought the Black Plague was mainly a combination of the bubonic and pneumonic forms. (The practice still used today of saying, “Bless you” after someone sneezes is a holdover from the 14th century plague) The only defense against the pandemic was avoidance of fleas and the fatally sick. Not easy to pull off when rats and the afflicted were widespread. Infected families were generally quarantined, their houses marked with a red cross, and left to fend for themselves.

The plague had a tremendous effect on European life in the Middle Ages. The Hundred Years’ War actually paused briefly in 1348 for lack of soldiers. The plague had wiped out too many of them. Economically, wages rose sharply because the workforce was also greatly reduced. Shop owners suffered because no one dared step outside the confines of their own homes, so supplies rose and prices dropped. The removal of the rotting corpses required relatives either doing it themselves and further risking infection, or paying premium prices for some other poor schlub to do it. The dead were buried as quickly as possible, often in mass graves.

In the recent research which appears in the Proceedings of the National Academy of Sciences, Dr. Johannes Krause and his colleagues extracted DNA from the tooth enamel of five corpses from one of these 14th century mass burial sites in London (under the Royal Mint!). Using the latest technology to sequence the DNA fragments, the researchers from the University of Tubingen in Germany, and McMaster University in Canada, decoded a circular genome called pPCP1 plasmid that comprises about 10,000 positions in the Y. pestis DNA. When they compared it with the genome of the pathogen’s current strain, the genetic information appeared to have changed very little over the past six centuries. (It should be noted that the researchers suspect the pathogen that occurred in the 6th century may have been a now-extinct strain of Y. pestis or one completely unrelated to bubonic plague.)

So, that means the very same nasty contagion – the one that terrorized and devastated so much of Europe for so many centuries in the Middle Ages - is still with us today. Luckily, the bubonic plague can be held at bay with antibodies if treated in time. But what happens if Yersinia pestis mutates into a strain against which current antibodies are useless? If that doesn’t make the hair on the back of your neck stand on end, I don’t know what will.

Happy Halloween!

SOURCES and LINKS
Scientific Computing story
The Black Plague by Dr. Skip Knox, Boise State
Plague symptons and signs – in case you get it
Nifty Black Death quiz – thanks Liza!