Scientists Discover Jellyfish Sleep Even Though They Don’t Have Brains
Sleeping is widely regarded as a good way to recharge your brain, but that raises a particularly perplexing question: do animals without brains sleep? The answer is, surprisingly, yes, at least when it comes to jellyfish.
Earlier today, three graduate student researchers at the California Institute of Technology (Ravi Nath of the Sternberg laboratory, Claire Bedbrook of the Gradinaru laboratory, and Michael Abrams of the Goentoro laboratory) announced they have discovered that jellyfish sleep. You probably wonder how the team was even able to quantify what would be considered sleep in animals without brains or spines, but before they started the experiment, the researchers debated, considered, and finally devised the three necessary criteria for sleep that they used in the study:
- The animal must exhibit a period of demonstrably reduced activity, otherwise known as “quiescence.”
- The animal must respond slower to stimuli during this period.
- The animal must show an increased desire to enter a period of quiescence when deprived of it.
These criteria were devised by examining sleep in other animals, including humans. “When humans sleep, we are inactive, we often can sleep through noises or other disturbances which we might otherwise react to if we were awake, and we’re likely to fall asleep during the day if we don’t get enough sleep,” explained Bedbrook.
The jellyfish chosen for the experiment study was the most evolutionarily primitive one on the planet: a Cassiopea jellyfish, or just simply Cassiopea. Unlike most jellyfish, Cassiopea spends most of its life lying upside down on the ocean floor like some weird, fleshy, pulsating sea plant. During the study, cameras monitored this animal 24/7, and the researchers noted the jellyfish pulsed slower at night, 39 times per minute instead of the regular 58 times per minute during the day. This slower pulse fulfilled the “period of reduced activity/quiescence” criterion, but what about the other two?
To show that the Cassiopea react slower during this period of reduced activity, the researchers placed the jellyfish on a platform in the study tank and pulled the platform out from under it when it started “sleeping.” Normally, Cassiopea would immediately swim to the bottom of the tank, but at night, the team discovered it floated listlessly in the water for up to five seconds before heading to the tank floor. This suggests the Cassiopea jellyfish isn’t readily aware of its environment when it enters a period of quiescence, which fulfilled another sleep criterion and left the final one, an increased desire to sleep when deprived of sleep.
The only way to show that animals experience an increased desire to sleep when deprived of it is to, well, deprive them of sleep, which is exactly what the team did; they “poked” the Cassiopea awake by pulsing water at them every 10 seconds for 20 minutes. Just as the researchers predicted, the jellyfish fell asleep during the day, thus fulfilling the final criterion and demonstrating even jellyfish sleep. However, the researchers considered the possibility that the period of quiescence wasn’t sleep but instead some analogous sleep-like state, so they exposed the jellyfish to compounds known to induce sleep in other animals, such as melatonin. The jellyfish reacted just as the researchers predicted, which, according to Abrams, means the mechanism determining the Cassiopea‘s sleep is “similar to those of other organisms — including humans.”
I know what you’re thinking: why is determining if jellyfish sleep so important? Well, normally when we think about sleep, we think about resting our brains to convert short-term memory into long-term memory and to rejuvenate our cognitive functions. However, jellyfish don’t have brains and thus don’t have memories and cognitive functions as we know them, which raises the question: why do jellyfish need sleep? The study might not shed any light on this particular question, but, according to Nath, “This finding opens up many more questions: Is sleep the property of neurons? And perhaps a more far-fetched question: Do plants sleep?” Only time will tell just how much we can discover about sleep, including its evolutionary origins.
Chinese Dinosaur Might Have Been as Iridescent as a Hummingbird
Earlier this month, I wrote an article on a toy line of scientifically accurate Velociraptor action figures with plumage inspired by modern birds. I mused how impressive it would be if prehistoric raptors had been covered by feather patterns not unlike those in the toy line. Little did I know that two weeks later, researchers would reveal that some theropods had iridescent feathers that outshine David Silva’s velocifigures.
The Caihong juji, Mandarin for “rainbow with a big crest” (or just Caihong for short), was a “paravian theropod,” a clade commonly known for its winged forelimbs (even though many weren’t capable of flight) and enlarged sickle foot claws. In 2014, a farmer in the Qinlong County in the Hebei Province of Northeastern China gave a nearly complete Caihong fossil, feathers included, to The Paleontological Museum of Liaoning. Finding a complete skeleton is rare in paleontology and proved very helpful to the researchers. However, you might wonder just how scientists were able to determine the iridescent nature of the Caihong’s plumage. Two words: fossilized melanosomes.
Melanosomes are organelles that create, store, and transport melanin, which determines the pigments/colors of animal hair, fur, skin, scales, and feathers. Upon examining the Caihong’s head, crest, and tail feathers with an electron microscope, scientists discovered platelet-shaped structures similar in shape to the melanosomes that give hummingbirds their iridescent coloring. The rest of the body feathers had melanosome structures similar to those in the grey and black feathers of penguins, which would have made for an odd sight: a duck-sized dinosaur with body feathers as drab as a raven’s and head and neck feathers more colorful than a peacock’s.
The inferred feather coloration of the Caihong is not its only unusual feature, though. The dinosaur had longer arm and leg feathers than its relatives, and its tail feathers created a “tail surface area” that was larger than the famous proto-bird the Archaeopteryx. Furthermore, the Caihong had bony crests, which while common among most dinosaurs, are almost unheard of among paravian theropods. But, more importantly, it had proportionally long forearms, which is a feature of flight-capable theropods, even though scientists believe the Caihong didn’t fly. While this dinosaur apparently has the earliest examples of proportionally long forearms in the theropod fossil records, it still falls in line with the belief that the evolution of flight-capable feathers outpaced the evolution of flight-capable skeletons. The melanosomes, however, are the more intriguing discovery, since they are the earliest examples of “organized platlet-shaped nanostructures…in dinosaurian feathers.”
While paleontologists are confident the Caihong’s platelet structures are melanosomes, the researchers understand that their discovery is based partially on inference and could potentially be incorrect. If the structures aren’t melanosomes, well, that invalidates this entire article. But that’s what paleontology is all about: examining the evidence, creating inferences supported by that evidence, and changing those inferences when new information becomes available. Still, the concept of dinosaurs with iridescent feathers is pretty cool. If you want to learn more about the Caihong juji, you can read the original article on Nature.
Scientists Discover Velociraptor’s Cousin, and It Looks Like a Swan
When we hear the word Velociraptor, we usually think about the clever girls from Jurassic Park/World. In my case, I think about Dinobot from Beast Wars, but that’s neither here nor there, because after you’re done reading this article, you won’t be able to get the following thought out of your head: Velociraptors are related to a dinosaur best described as a prehistoric swan. Good luck ever seeing ol’ sickle claw the same way again.
Say hello to the Halszkaraptor essuilliei (Halszka for short), a dinosaur recently discovered at Ukhaa Tolgod (part of the Djadochta Formation in the Gobi Desert in Mongolia) by a team of paleontologists led by Andreau Cau of the Geological Museum Capellini in Bologna, Italy. Halszka’s around 75 million years old, which means he was alive during the late Cretaceous period during what is known as the Campanian age. And if you’re wondering why he looks like a swan, that’s because, according to a 3D synchrotron analysis (a process that uses x-rays so powerful they can only be produced in facilities the size of football stadiums), he’s semi-aquatic. Doesn’t he just look adorable?
Halszka belongs to the suborder therapod, known for specimens such as Tyrannosaurus Rex, the Velociraptor, and the ostrich. Therapods are known for their efficacy on land, but until the Halszkaraptor’s discovery, scientists thought they were exclusive to solid ground. Sure, some therapods might have eaten fish from time to time, but Halszka is the only known therapod with aquatic tendencies.
“The first time I examined the specimen, I even questioned whether it was a genuine fossil,” explained Cau. “This unexpected mix of traits makes it difficult to place Halszka within traditional classifications.” Given the long, swan-like neck, dinky flippers, and sickle-shaped claws reminiscent of the Velociraptor, I can’t blame him for being confused. Zoologists went through the same problem when they examined the first known platypus back in 1799; who wouldn’t be confused by such disparate features? “When we look beyond fossil dinosaurs, we find most of Halszkaraptor‘s unusual features among aquatic reptiles and swimming birds,” Cau continued. “The peculiar morphology of Halszkaraptor fits best with that of an amphibious predator that was adapted to a combined terrestrial and aquatic ecology: a peculiar lifestyle that was previously unreported in these dinosaurs. Thanks to synchrotron tomography, we now demonstrate that raptorial dinosaurs not only ran and flew, but also swam!”
Halszka now proudly sits as the first of a new genus of amphibious dinosaurs, capable of using its legs to walk on land and swim through the water and with a posture likely similar to those of modern day ducks and swans. Since the Gobi Desert, especially the Djadoctha Formation, appears to be a hotbed of important paleontological finds, many of which are therapods related to Halszka, who knows how many other amphibious dinosaurs are waiting to be discovered? Halszka could either be one of many previously undiscovered swimming raptors or as unique as the Mesonychid; nature’s first and only attempt at a hoofed predator.
If you are interested in reading Cau’s paper on the Halszkaraptor essuilliei, you can read the article on Nature. However, if you do not have a subscription, you should either read the Science Daily article or Andreau Cau’s personal blog (it is in Italian but an English translation is readily available on the page).
Researchers Use Stem Cells to Help Rats with Paraplegia Walk Again
Spinal cord injuries (SCIs) harm the nerves housed in the spinal cord, often causing irreversible damage to the body and its functions. Normally, physicians and other clinicians can only help people adapt to their SCIs instead of healing them, but researchers at Tel Aviv University and the Technion-Israel Institute of Technology might have discovered an essential key in the search for a possible cure. Just a word of warning: this article contains descriptions of animal experimentation, so some information might not be suitable for some readers.
Dr. Shulamit Levenberg of the Technion-Israel Institute of Technology recently led a multi-university study to determine if lab rats with simulated complete spinal cord injuries could regain the use of their hind legs with the introduction of stem cells and tissue engineered scaffolds. Some stem cells had been induced to differentiate (i.e., develop into different type of cells such as support cells), while others hadn’t been induced at all. And, the scaffolds were designed to “provide a 3D environment in which cells can attach, grow and differentiate, maintain cell distribution, and provide graft protection following transplantation.” In other words, the scaffolds made sure the stem cells grew as intended and weren’t accidentally damaged.
Researchers took lab rats and surgically removed a small portion of the lamina (the bony plates of the vertebrae that protect the spinal column and the vulnerable nerves) and cut through all of the nerves. Since incomplete spinal cord injuries only damage some nerves and can, for example, leave people unable to move their legs but capable of feeling through them or vice versa, the researchers had to sever all the nerves to simulate a complete spinal cord injury. Some rats were then implanted with the scaffold and stem cells (some of which were induced and some of which were not) to bridge the severed nerves. Other rats were implanted only with the scaffold, and a control group received neither scaffold nor stem cells.
After the scaffolds and stem cells were implanted, the researchers stitched up all the rats, including the control group, and observed them for any improvements. Rats that received both the scaffold and induced stem cells recovered better than the other groups; 42% of these rats were able to walk and support their body weight with their hind legs after three weeks. Furthermore 75% of this group reacted to stimuli in their hind legs and tail. Fewer rats with the non-induced stem cells recovered as fully as the rats with the induced stem cells. Furthermore, researchers found the scaffold-only group could not respond to any stimuli in their hind legs or tail, and rats in the control group did not improve at all.
While the study demonstrates that induced stem cells coupled with tissue engineered scaffolds could potentially help people with SCIs walk again, the number of rats who fully recovered was fairly low. Still, the results are promising and lay the groundwork for future studies that might one day develop a cure for SCIs. The full article on Levenberg’s study can be found on Frontiers.
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