Imagine opening your eyes for the first time as a brand new baby. The world is so mysterious, full of obstacles and strange shapes. And yet it does not take babies all that long to get their bearings, to latch on to their parents, and to start interacting. How do they do this so quickly? A new study published in Science proposes that babies of mammals dream about the world they are about to enter before being born, developing important skills.
The team, led by professor Michael Crair, who specializes in neuroscience, ophthalmology, and visual science, wanted to understand why when mammals are born, they are already somewhat prepared to interact with the world.
"At eye opening, mammals are capable of pretty sophisticated behavior," said Craig, "But how do the circuits form that allow us to perceive motion and navigate the world? It turns out we are born capable of many of these behaviors, at least in rudimentary form."
Unusual retinal activity
The scientists observed waves of activity radiating from the retinas of newborn mice before their eyes first open. Imaging shows that soon after birth, this activity disappears. In its place matures a network of neural transmissions that carries visual stimuli to the brain, as explained by a Yale press release. Once it reaches the brain, the information is encoded for storage.
What's particularly unusual about this neonatal activity is that it demonstrates a pattern that would happen if the animal was moving forward in its environment. As the researchers write in the study, "Spontaneous waves of retinal activity flow in the same pattern as would be produced days later by actual movement through the environment."
VIDEO: RETINAL WAVES IN NEONATAL MICE
Crair explained that this "dream-like activity" makes sense from an evolutionary standpoint, as it helps the mouse get ready for what will happen to it after it opens its eyes. It allows the animal to "respond immediately to environmental threats," Crair shared.
What is creating the waves?
The scientists also probed what is responsible for creating the retinal waves that mimic forward motion. They turned on and off the functionality of starburst amacrine cells — retinal cells that release neurotransmitters — and discovered that blocking them stopped the retinal waves from flowing, which hindered the mouse from developing the ability to react to visual motion upon birth. These cells are also important to an adult mouse, affecting how it reacts to environmental stimuli.
Graphic showing the origin and functionality of directional retinal waves.Michael C. Crair et al, Science, 2021.
What about human babies?
While the study focused on mice, human babies also seem to be able to identify objects and motion right after birth. This suggests the presence of a similar phenomenon in babies before they are born.
"These brain circuits are self-organized at birth and some of the early teaching is already done," Crair stated. "It's like dreaming about what you are going to see before you even open your eyes."
Considering how much sharks are feared by humans, it is a bit of a surprise that scientists don't know much about the predators. For example, until recently, sharks were thought to be solitary creatures searching the seas for food on their own. Now it appears that some sharks are quite social.
Another mystery is how these prehistoric swimming and eating machines digest food. Although scientists have made 2D sketches of captured sharks' digestive systems based on dissections, there is a limit to what can be learned in this way. Professor Adam Summers at University of Washington's Friday Harbor Labs says:
"Intestines are so complex, with so many overlapping layers, that dissection destroys the context and connectivity of the tissue. It would be like trying to understand what was reported in a newspaper by taking scissors to a rolled-up copy. The story just won't hang together."
Summers is co-author of a new study that has produced the first 3D scans of a shark's intestines, which turns out to have a strange, corkscrew structure. What's even more bizarre is that it resembles the amazing one-way valve designed by inventor Nikola Tesla in 1920. The research is published in the journal Proceedings of the Royal Society B.
What a 3D model reveals
Video: Pacific spiny dogfish intestine youtu.be
According to the study's lead author Samantha Leigh, "It's high time that some modern technology was used to look at these really amazing spiral intestines of sharks. We developed a new method to digitally scan these tissues and now can look at the soft tissues in such great detail without having to slice into them."
"CT scanning is one of the only ways to understand the shape of shark intestines in three dimensions," adds Summers. The researchers scanned the intestines of nearly three dozen different shark species.
It is believed that sharks go for extended periods — days or even weeks — between big meals. The scans reveal that food passes slowly through the intestine, affording sharks' digestive system the time to fully extract its nutrient value. The researchers hypothesize that such a slow digestive process may also require less energy.
It could be that this slow digestion is more susceptible to back flow given that the momentum of digested food through the tract must be minimal. Perhaps that is why sharks evolved something so similar to a Tesla valve.
What is Tesla's valve doing there?
Above, a Tesla valve. Below, a shark intestine.Credit: Samantha Leigh / California State University, Domi
Tesla's "valvular conduit," or what the world now calls a "Tesla valve," is a one-way valve with no moving parts. Its brilliance is based in fluid dynamics and only now coming to be fully appreciated. Essentially, a series of teardrop-shaped loops arranged along the length of the valve allow water to flow easily in one direction but not in the other. Modern tests reveal that at low flow rates, water can travel through the valve either way, but at high flow rates, the design kicks in. According to mathematician Leif Ristroph:
"Crucially, this turn-on comes with the generation of turbulent flows in the reverse direction, which 'plug' the pipe with vortices and disrupting currents. Moreover, the turbulence appears at far lower flow rates than have ever previously been observed for pipes of more standard shapes — up to 20 times lower speed than conventional turbulence in a cylindrical pipe or tube. This shows the power it has to control flows, which could be used in many applications."
A deeper dive
Summers suggests the scans are just the beginning. "The vast majority of shark species, and the majority of their physiology, are completely unknown," says Summers, adding that "every single natural history observation, internal visualization, and anatomical investigation shows us things we could not have guessed at."
To this end, the researchers plan to use 3D printing to produce models through which they can observe the behavior of different substances passing through them — after all, sharks typically eat fish, invertebrates, mammals, and seagrass. They also plan to explore with engineers ways in which the shark intestine design could be used industrially, perhaps for the treatment of wastewater or for filtering microplastics.
It could fairly be said, though, that Nikola Tesla was 100 years ahead of them.
Dumpster-diving trash parrots
In a study about these smart birds just published in Science, researchers define animal culture as "population-specific behaviors acquired via social learning from knowledgeable individuals."
Co-lead author of the study Barbara Klump of the Max Planck Institute of Animal Behavior in Konstanz, Germany says, "[C]ompared to humans, there are few known examples of animals learning from each other. Demonstrating that food scavenging behavior is not due to genetics is a challenge."
An opportunity presented itself in a video that co-author Richard Major of the Australian Museum shared with Klump and the other co-authors. In the video, a sulphur-crested cockatoo used its beak to pull up the handle of a closed garbage bin — using its foot as a wedge — and then walked back the lid sufficiently to flip it open, exposing the bin's edible contents.
Major has been studying Cacatua galerita for 20 years and says, "Like many Australian birds, sulphur-crested cockatoos are loud and aggressive." The study describes them as a "large-brained, long-lived, and highly social parrot." Says Major, "They are also incredibly smart, persistent, and have adapted brilliantly to living with humans."
(Research regarding some of the ways in which wild animals adapt to the presence of humans has already produced some fascinating results and is ongoing.)Clever cockie opens bin - 01 youtu.be
The researchers became curious about how widespread this behavior might be and saw a research opportunity. After all, says John Martin, a researcher at Taronga Conservation Society, "Australian garbage bins have a uniform design across the country, and sulphur-crested cockatoos are common across the entire east coast."
Martin continues, "In 2018, we launched an online survey in various areas across Sydney and Australia with questions such as, 'What area are you from, have you seen this behavior before, and if so, when?'"
Word gets around
Credit: magspace/Adobe Stock
Although the cockatoos' maneuver was reported in only three suburbs before 2018, by the end of 2019, people in 44 areas reported observing the behavior. Clearly, more and more cockatoos were learning how to successfully dumpster dive.
As further proof, says Klump, "We observed that the birds do not open the garbage bins in the same way, but rather used different opening techniques in different suburbs, suggesting that the behavior is learned by observing others." One individual bird in north Sydney invented its own method, and the scientists saw it grow in popularity throughout the local population.
To track individual birds, the researchers marked 500 cockatoos with small red dots. Subsequent observations revealed that not all cockatoos are bin-openers. Only about 10 percent of them are, and they are mostly males. The other cockatoos apparently restrict their education to a different lesson: hang around with a bin-opener, and you will get supper.
Thanks to the surveys, the researchers consider the entire project to be a valuable citizen-science experiment. "By studying this behavior with the help of local residents, we are uncovering the unique and complex cultures of their neighborhood birds."
