CLOSE
Nick Hobgood via Wikimedia Commons // CC BY-SA 3.0
Nick Hobgood via Wikimedia Commons // CC BY-SA 3.0

Coral and Algae Have Been Friends for 212 Million Years

Nick Hobgood via Wikimedia Commons // CC BY-SA 3.0
Nick Hobgood via Wikimedia Commons // CC BY-SA 3.0

Some classics were just made to go together. Peanut butter and chocolate. Thanksgiving dinner and stretch pants. Scleractinian corals and dinoflagellate algae. And boy, do those two go way back—scientists looking at fossils say the two have been cohabiting since at least about 212 million years ago, in the Late Triassic Period. The researchers published their report today in the journal Science Advances.

Happy, healthy coral is essential for a happy, healthy reef. To stay happy and healthy, many modern corals have forged super close relationships with teeny algae called zooxanthellae. The corals give the algae a safe place to live and the chemical components for photosynthesis, while the algae make oxygen, keep the water clean, and produce all kinds of helpful nutrients. The pair really have a good thing going.

But just how long it’s been going on has been anybody’s guess. Previous studies on the pair’s relationship have been largely speculative, using data from modern-day corals to imagine their ancestors’ world.

Now, two new scientific techniques, one visual and one chemical, have allowed us to get a far more accurate picture of coral history.

Earlier this year, lead author Katarzyna Frankowiak and a number of her co-authors reported that they’d figured out how to tell if a fossilized hard coral had been in a relationship with algae. The trick, they said, is to look very closely at the coral’s skeleton to see how it had grown and aged. Even when the algae itself was long gone, its presence had left irrevocable (if microscopic) changes in the coral’s life.

For the new study, the researchers applied this technique to tiny samples of fossilized hard corals found near the former Tethys Sea in Turkey. They used a variety of high-powered microscopes to examine the fossils in the most minute of detail and found that the skeletons of these ancient, ancient samples looked a lot like those of modern symbiotic hard corals.

Algae activity (brown dots in the tissue, upper left image) is recorded in the coral skeleton as structural (growth bands; upper right image) and geochemical signatures. Such regular growth bands occur in Upper Triassic (ca. 220 Ma) scleractinian corals (lower images) as well. Image Credit: Isabelle Domart-Coulon (upper left), Jarosław Stolarski (upper right, and lower images)

The second new method concerned the corals’ chemical composition. The experience of living with algae alters a coral’s very molecules, changing the ratio of various oxygen, carbon, and nitrogen isotopes. And just as with the visual inspection, analysis of the fossil corals’ isotopes suggested that they’d been sharing their lives with zooxanthellae.

Analyzing the coral isotopes yielded another insight: the sea in which these buddies lived was likely in pretty poor condition. The fossil corals shared a similar ratio of nitrogen isotopes with modern symbiotic Bermuda corals, which are currently struggling in nutrient-starved waters. It’s possible, the researchers say, that these difficult conditions were what inspired the algae and the corals to band together in the first place.

nextArticle.image_alt|e
Ted Cranford
arrow
science
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.

nextArticle.image_alt|e
Scientific Reports, Fernando Ramirez Rozzi
arrow
Stones, Bones, and Wrecks
Humans Might Have Practiced Brain Surgery on Cows 5000 Years Ago
Scientific Reports, Fernando Ramirez Rozzi
Scientific Reports, Fernando Ramirez Rozzi

In the 1970s, archaeologists discovered a site in France containing hundreds of cow skeletons dating back 5000 to 5400 years. The sheer number wasn't surprising—human agriculture in that part of the world was booming by 3000 BCE. What perplexed scientists was something uncovered there a few decades later: a cow skull bearing a thoughtfully drilled hole. Now, a team of researchers has released evidence that suggests the hole is an early example of animal brain surgery.

Fernando Ramírez Rozzi, a paleontologist with the French National Center for Scientific Research, and Alain Froment, an anthropologist at the Museum of Mankind in Paris, published their findings in the journal Nature Scientific Reports. After comparing the opening to the holes chiseled into the skulls of humans from the same era, they found the bones bore some striking similarities. They didn't show any signs of fracturing from blunt force trauma; rather, the hole in the cow skull, like those in the human skulls, seemed to have been carved out carefully using a tool made for exactly that purpose. That suggests that the hole is evidence of the earliest known veterinary surgery performed by humans.

Trepanation, or the practice of boring holes into human skulls, is one of the oldest forms of surgery. Experts are still unsure why ancient humans did this, but the level of care that went into the procedures suggests that the surgery was likely used to treat sick patients while they were still alive. Why a person would perform this same surgery on a cow, however, is harder to explain.

The authors present a few theories, the first being that these ancient brain surgeons were treating a sick cow the same way they might treat a sick human. If a cow was suffering from a neural disease like epilepsy, perhaps they though that cutting a hole in its head would relieve whatever was agitating the brain. The cow would have needed to be pretty special to warrant such an effort when there were hundreds of healthy cows living on the same plot of land, as evidenced by the skeletons it was found with.

Another possible explanation was that whoever operated on the cow did so as practice to prepare them for drilling into the heads of live humans one day. "Cranial surgery requires great manual dexterity and a complete knowledge of the anatomy of the brain and vessel distribution," the authors write in the study. "It is possible that the mastery of techniques in cranial surgery shown in the Mesolithic and Neolithic periods was acquired through experimentation on animals."

Either way, the bovine patient didn't live to see the results of the procedure: The bone around the hole hadn't healed at all, which suggests the cow either died during surgery or wasn't alive to begin with.

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios