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Sergio Carvalho via Flickr // CC BY-NC-ND 2.0
Sergio Carvalho via Flickr // CC BY-NC-ND 2.0

5 Strange Microbes (and 1 Bonus Organism)

Sergio Carvalho via Flickr // CC BY-NC-ND 2.0
Sergio Carvalho via Flickr // CC BY-NC-ND 2.0

The world is teeming with life, and we're always discovering new species—including some that stretch the limits of how we view and classify biological life forms. Here are a few that clearly don't play by the rules.

1. BDELLOID ROTIFERS

Diego Fontaneto via Wikimedia Commons // CC BY 2.5

 
Bdelloid rotifers are microscopic superstars inside a drop of water. These tiny transparent animals—which can be found all over the world (even Antarctica!)—are masters of survival and reproduction. When water becomes scarce, they dry up like brine shrimp, surviving for years completely desiccated. When water returns, they rehydrate themselves and continue on as good as new. Rotifers are all female and reproduce asexually, laying eggs that don't need to be fertilized and are essentially clones of themselves. While they're not the only animal that doesn't need a member of the opposite sex to reproduce, they're more successful than others: Bdelloid rotifers have evolved into 450 species. How can a creature evolve if it's only producing clones? Random mutations would produce changes, but cannot explain the rotifers' 80-million-year survival and successful speciation.

The secret to rotifers' evolution is that they steal genes from other living things. DNA analysis of bdelloid rotifers shows that about 10 percent of their genes come from bacteria, fungi, and plants. How does that happen? It turns out that bdelloid rotifers are also masters at surviving ionizing radiation, which damages DNA. The creatures are able to repair their own DNA, but can incorporate new genes (from the surrounding environment or something they ate) in the repair process. Over time, the new genes are used to adapt to the environment, leading to the evolution of new rotifer species as well as incorporating the necessary genetic material to protect against parasites.

2. EUGLENA

Deuterostome via Wikimedia Commons // CC BY-SA 3.0

 
Euglena is a genus that contains hundreds of species of single-cell organisms that are not plant nor animal nor bacteria, but have features of all three. Most species of Euglena are mixotrophs that power themselves based on environmental conditions. When sunlight is present, for example, Euglena will use it to make food by photosynthesis using chloroplasts, the genes for which may have been taken from engulfed alga sometime in Euglena's evolutionary history. When there is no sunlight, Euglena ingests surrounding substances like an animal to get energy. But what's really amazing about Euglena is that its behavior can be useful to humans. A company in Japan is looking into using some species of Euglena for food and biofuel, and other species might be used to clean the environment as they eat pollutants.

3. TRICHOPLAX ADHAERENS

Bernd Schierwater via Wikimedia Commons // CC BY 4.0

 
Among multicellular animals, the microscopic Trichoplax adhaerens is the master of minimalism. It's so simple, in fact, that for decades it was assumed that it was only a larval stage of another animal. T. adhaerens is comprised of just four types of cells, and is basically two sheets of cells with some more cells in between. It has no organs and no discernible front or back, though it does have a distinct upper and lower side—the organism uses that lower side both to eat and to adhere to surfaces. It can move either by changing shape or by using tiny cilia on its outer layers. It's perhaps not surprising T. adhaerens has an extremely simple genome, too, with 98 million base pairs, compared to over 3 billion for humans. They reproduce by splitting, by budding, or by sexual reproduction. Scientists don't know exactly how they manage the sexual reproduction; organisms have been observed degenerating into eggs, but fertilization is still a mystery.

4. TARDIGRADES

Tardigrades, also called water bears or moss piglets, resemble eight-legged faceless bears, except they're generally a half-millimeter long. Hundreds of species of these tiny animals are found in every kind of environment on earth, but they prefer to be among moss, algae, and lichen. While ocean-based tardigrades are pretty normal, land and fresh water tardigrades are famously hard to kill. If the environment is dry, they dry up too, and go into a dormant state that they emerge from when wet conditions return, even years later. They can survive boiling or freezing temperatures. They can survive in the vacuum of space and in high pressure conditions. They can survive radiation that would kill lesser animals.

In case you want a tardigrade of your own, the International Society of Tardigrade Hunters has instructions for collecting them. A low-power microscope should suffice for observation.

5. GEOGEMMA BAROSSII

A thermal vent. Image Credit: Sergio Carvalho via Flickr // CC BY-NC-ND 2.0

 
A microbe of the Archaea domain, Geogemma barossii is a microbe that likes it hot. This hyperthermophile, sometimes referred to as Strain 121, grows optimally at 220°F, but does just fine at 250°F (or 121°C, hence the name). It doesn't die until temperatures go over 266°F—one of the highest-known temperature tolerances of any living thing. The discovery of G. barossi's heat tolerance in 2003 gave pause to medical specialists when they realized that their sterilization procedures would not kill this microbe. However, Strain 121 cannot grow in the range of a human's body temperature, so it isn't considered infectious. Its normal home is thermal vents in the ocean floor.

BONUS: GROMIA SPHAERICA

The size of a grape, Gromia sphaerica is too big to be a microbe—but this single-celled organism is too cool not to include. This ancient relative of the amoeba lives at the bottom of the ocean, and was first discovered in the Arabian Sea in 2000. Adult specimens can grow to be 1.5 inches in diameter, or as small .019 inches. While a single cell that big is pretty strange, the most remarkable thing about G. sphaerica is the trails they leave behind on the sea floor. They weren't created by the organisms rolling downhill (they can actually move uphill), and they weren't created by ocean currents. Somehow, these big cells moved on their own and are heavy enough to leave a trail behind them. That raises questions about fossil trails from the Precambrian that scientists assumed were left by multicellular animals, but may have been left before multicellular life arose.

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Scientists Use a CT Scanner to Give Whales a Hearing Test
Ted Cranford
Ted Cranford

It's hard to study how whales hear. You can't just give the largest animals in the world a standard hearing test. But it's important to know, because noise pollution is a huge problem underwater. Loud sounds generated by human activity like shipping and drilling now permeate the ocean, subjecting animals like whales and dolphins to an unnatural din that interferes with their ability to sense and communicate.

New research presented at the 2018 Experimental Biology meeting in San Diego, California suggests that the answer lies in a CT scanner designed to image rockets. Scientists in San Diego recently used a CT scanner to scan an entire minke whale, allowing them to model how it and other whales hear.

Many whales rely on their hearing more than any other sense. Whales use sonar to detect the environment around them. Sound travels fast underwater and can carry across long distances, and it allows whales to sense both predators and potential prey over the vast territories these animals inhabit. It’s key to communicating with other whales, too.

A CT scan of two halves of a dead whale
Ted Cranford, San Diego State University

Human technology, meanwhile, has made the ocean a noisy place. The propellers and engines of commercial ships create chronic, low-frequency noise that’s within the hearing range of many marine species, including baleen whales like the minke. The oil and gas industry is a major contributor, not only because of offshore drilling, but due to seismic testing for potential drilling sites, which involves blasting air at the ocean floor and measuring the (loud) sound that comes back. Military sonar operations can also have a profound impact; so much so that several years ago, environmental groups filed lawsuits against the U.S. Navy over its sonar testing off the coasts of California and Hawaii. (The environmentalists won, but the new rules may not be much better.)

Using the CT scans and computer modeling, San Diego State University biologist Ted Cranford predicted the ranges of audible sounds for the fin whale and the minke. To do so, he and his team scanned the body of an 11-foot-long minke whale calf (euthanized after being stranded on a Maryland beach in 2012 and preserved) with a CT scanner built to detect flaws in solid-fuel rocket engines. Cranford and his colleague Peter Krysl had previously used the same technique to scan the heads of a Cuvier’s beaked whale and a sperm whale to generate computer simulations of their auditory systems [PDF].

To save time scanning the minke calf, Cranford and the team ended up cutting the whale in half and scanning both parts. Then they digitally reconstructed it for the purposes of the model.

The scans, which assessed tissue density and elasticity, helped them visualize how sound waves vibrate through the skull and soft tissue of a whale’s head. According to models created with that data, minke whales’ hearing is sensitive to a larger range of sound frequencies than previously thought. The whales are sensitive to higher frequencies beyond those of each other’s vocalizations, leading the researchers to believe that they may be trying to hear the higher-frequency sounds of orcas, one of their main predators. (Toothed whales and dolphins communicate at higher frequencies than baleen whales do.)

Knowing the exact frequencies whales can hear is an important part of figuring out just how much human-created noise pollution affects them. By some estimates, according to Cranford, the low-frequency noise underwater created by human activity has doubled every 10 years for the past half-century. "Understanding how various marine vertebrates receive and process low-frequency sound is crucial for assessing the potential impacts" of that noise, he said in a press statement.

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Women Suffer Worse Migraines Than Men. Now Scientists Think They Know Why
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iStock

Migraines are one of medicine's most frustrating mysteries, both causes and treatments. Now researchers believe they've solved one part of the puzzle: a protein affected by fluctuating estrogen levels may explain why more women suffer from migraines than men.

Migraines are the third most common illness in the world, affecting more than 1 in 10 people. Some 75 percent of sufferers are women, who also experience them more frequently and more intensely, and don't respond as well to drug treatments as men do.

At this year's Experimental Biology meeting in San Diego, researcher Emily Galloway presented new findings on the connection between the protein NHE1 and the development of migraine headaches. NHE1 regulates the transfer of protons and sodium ions across cell membranes, including the membranes that separate incoming blood flow from the brain.

When NHE1 levels are low or the molecule isn't working as it's supposed to, migraine-level head pain can ensue. And because irregular NHE1 disrupts the flow of protons and sodium ions to the brain, medications like pain killers have trouble crossing the blood-brain barrier as well. This may explain why the condition is so hard to treat.

When the researchers analyzed NHE1 levels in the brains of male and female lab rats, the researchers found them to be four times higher in the males than in the females. Additionally, when estrogen levels were highest in the female specimens, NHE1 levels in the blood vessels of their brains were at their lowest.

Previous research had implicated fluctuating estrogen levels in migraines, but the mechanism behind it has remained elusive. The new finding could change the way migraines are studied and treated in the future, which is especially important considering that most migraine studies have focused on male animal subjects.

"Conducting research on the molecular mechanisms behind migraine is the first step in creating more targeted drugs to treat this condition, for men and women," Galloway said in a press statement. "Knowledge gained from this work could lead to relief for millions of those who suffer from migraines and identify individuals who may have better responses to specific therapies."

The new research is part of a broader effort to build a molecular map of the relationship between sex hormones and NHE1 expression. The next step is testing drugs that regulate these hormones to see how they affect NHE1 levels in the brain.

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