"Great Pond Snail" (Lymnaea stagnalis)
…a species of large freshwater Lymnaeid snail which boasts a wide Holarctic distribution. Great pond snails occur solely in freshwater habitats, with individuals typically preferring slowly running or standing water bodies. Like many other freshwater snails L. stagnalis is an opportunistic feeder feeding on a range of organic matter.
People ask Google everything under the sun. One of the most commonly searched questions in the world is “What Is Love?” Allow us at SciShow to explain.
Ask us YOUR most pressing questions in reblogs or with #WMAQ elsewhere on the internet and we’ll answer a bunch of them in a video!
People ask Google everything under the sun. One of the most commonly searched questions in the world is “How do I get rid of hiccups?” Allow us at SciShow to explain.
Don’t forget to tag your most burning questions with #WMAQ — we will answer a bunch of them in a new video at the end of the month!
Developing zebrafish embryo
Our understanding of how animals grow from a single cell to billions of cells has benefited tremendously from the easy-to-visualize nature of zebrafish embryos. This video begins roughly two hours after a zebrafish egg has been fertilized and covers approximately 24 hours of the embryo’s life. In less than a day, the embryo will progress through dramatic changes in shape as cells move and specialize in a process called gastrulation. By 9 hours after fertilization, the rudimentary brain will start to thicken, and by 12 hours, premature eyes form. Muscular twitches begin and exaggerate from 20 hours onward before the heart even starts beating properly. Within three days from the start of its one-cell journey, the fish will reach the length of a sesame seed before swimming in search of food.
Video by Dr. Andrei Kobitski, Dr. Jens Otte and Dr. Johannes Stegmaier, Karlsruhe Institute of Technology, Germany.
SciShow Space takes you through perhaps the scariest part of every space mission — re-entry. How do astronauts survive the turbulent return to Earth’s atmosphere? Math, y’all!
APOLLO 11 FRUITCAKE — In the days of the Apollo space program, NASA knew that you can’t take a giant leap for mankind on an empty stomach. They provided the moon-bound astronauts with three meals per day, adding up to approximately 2,800 calories. This included tasty treats like pudding, brownies, and fruitcake. Though fruitcake has a somewhat infamous rep for being rather indestructible, NASA’s food mavens made sure it was compressed and protected with a 4-ply, laminated film coating to guard against flavor loss, moisture, oxygen invasion, spoiling, or excess crumbling.
Human sensitivity to wetness plays a role in many aspects of daily life. Whether feeling humidity, sweat or a damp towel, we often encounter stimuli that feel wet. Though it seems simple, feeling that something is wet is quite a feat because our skin does not have receptors that sense wetness. The concept of wetness, in fact, may be more of a “perceptual illusion” that our brain evokes based on our prior experiences with stimuli that we have learned are wet.
So how would a person know if he has sat on a wet seat or walked through a puddle? Researchers at Loughborough University and Oxylane Research proposed that wetness perception is intertwined with our ability to sense cold temperature and tactile sensations such as pressure and texture. They also observed the role of A-nerve fibers—sensory nerves that carry temperature and tactile information from the skin to the brain—and the effect of reduced nerve activity on wetness perception. Lastly, they hypothesized that because hairy skin is more sensitive to thermal stimuli, it would be more perceptive to wetness than glabrous skin (e.g., palms of the hands, soles of the feet), which is more sensitive to tactile stimuli.
Davide Filingeri et al. exposed 13 healthy male college students to warm, neutral and cold wet stimuli. They tested sites on the subjects’ forearms (hairy skin) and fingertips (glabrous skin). The researchers also performed the wet stimulus test with and without a nerve block. The nerve block was achieved by using an inflatable compression (blood pressure) cuff to attain enough pressure to dampen A-nerve sensitivity.
They found that wet perception increased as temperature decreased, meaning subjects were much more likely to sense cold wet stimuli than warm or neutral wet stimuli. The research team also found that the subjects were less sensitive to wetness when the A-nerve activity was blocked and that hairy skin is more sensitive to wetness than glabrous skin. These results contribute to the understanding of how humans interpret wetness and present a new model for how the brain processes this sensation.
“Based on a concept of perceptual learning and Bayesian perceptual inference, we developed the first neurophysiological model of cutaneous wetness sensitivity centered on the multisensory integration of cold-sensitive and mechanosensitive skin afferents,” the research team wrote. “Our results provide evidence for the existence of a specific information processing model that underpins the neural representation of a typical wet stimulus.”
The article “Why wet feels wet? A neurophysiological model of human cutaneous wetness sensitivity” is published in the Journal of Neurophysiology.
35,000 walruses all hanging out at the same beach in Alaska? Why? Does global warming have anything to do with it? And what have we learned after 20 years of studying the effects of marijuana? SciShow News explains.
What the heck is this? Last week, we asked you about this curiosity found in the Connecticut River. Today, the jury is back. Eric Schultz, an associate professor of ecology and biology at the University of Connecticut, says it’s a bryozoan.
Likely called pectinatella magnifica, this colonial organism (made up of individual animals called zooids), can either attach itself to other river objects or float freely. Very cool animal and a great photo. Thanks for the submission!