inside the jelly, Cyanea capillata gonads (yellow parts) in oral lobes.
- awesome photographs by Alexander Semenov
For decades, flower hat jellyfish managed to keep their early lives a secret.
In adulthood, the jellyfish are striking, with a nest of fluorescent tentacles that look like party streamers, but pack a nasty sting. In infancy, well, scientists didn’t know. Aquarists tried, unsuccessfully, to raise the animals in tanks to understand what happens before the jellyfish are fully grown.
"They just aren’t like other jellies," said Wyatt Patry, senior aquarist at the Monterey Bay Aquarium in California.
Now, Patry and colleagues report they’ve finally raised the jellyfish in captivity. In a new paper, the researchers describe the elusive species’ life cycle, from egg to larva to single-tentacled polyp to juvenile to adult.
Scientists at the aquarium first bought a group of flower hat jellies back from Japan in 2002 for an exhibit on jellyfish. At the time, aquarists tried to mate and culture the species (scientifically named Olindias formosus), but they just couldn’t seem to get the jellies to release any sperm or eggs.
Patry said the researchers tried performing in vitro fertilization and exposing the jellies to stresses that might make them release sex cells. The creatures produced some larvae, but they didn’t grow much larger than that stage. Ultimately, it seemed that the scientists were missing some cue the jellyfish needed for reproduction.
When it came time for another jellyfish show in 2012, the team tried again. They kept groups of flower hat jellies in small tanks with mesh netting to keep the creatures off the bottom, where detritus and rotting pieces of half-eaten fish settled. The scientists don’t exactly know what they did right the second time around, but during routine maintenance, they discovered fluorescent jellyfish polyps attached to the wire mesh and glowing under a blue light.
Jellyfish larvae attach themselves to a solid surface and become stalklike polyps, which then bud into juvenile “medusae” — what jellyfish are called when they reach their most recognizable, umbrella-shaped form. Jellyfish polyps persist for an unknown amount of time. The polyps of flower hat jellies were unusual in that they had a single, highly active tentacle.
"They just look like little sea anemones," Patry told Live Science. "They seem to use the tentacle to sweep around their position to capture food."
Patry hopes the new information might help scientists and wildlife managers look for the species in the wild — and predict when and where “blooms” of the jellyfish could affect beachgoers.
Flower hat jellies kill and eat entire fish, and their venom is powerful enough to inflict a painful rash on humans. The mark looks like a burn, said Patry. (Take it from him. He said he usually gets stung a couple of times a year.) A 2007 review of jellyfish incidents recorded around the world found one death associated with flower hat jellies, in Japan in the 1970s.
The findings on young flower hat jellies were published in June in the Journal of the Marine Biological Association of the United Kingdom.
(Click each image for short details)
Every year for nearly four decades, Nikon has received hundreds of entries in its Small World microscope photography contest. Every year, the images are more amazing, and this year’s winners — selected from nearly 2,000 submissions — are undoubtedly the best yet.
Super-close-ups of garlic, snail fossils, stinging nettle, bat embryos, bone cancer and a ladybug are among the top images this year. The first place winner (above) shows the blood-brain barrier in a living zebrafish embryo, which Nikon believes is the first image ever to show the formation of this barrier in a live animal.
“We used fluorescent proteins to look at brain endothelial cells and watched the blood-brain barrier develop in real-time,” the winners, Jennifer Peters and Michael Taylor of St. Jude Children’s Research Hospital, in Memphis, said in a press release. “We took a 3-dimensional snapshot under a confocal microscope. Then, we stacked the images and compressed them into one – pseudo coloring them in rainbow to illustrate depth.”
Here are the top 20 photomicrographs from the 38th Nikon Small World competition, selected for their originality, informational content, and visual impact by a panel of scientists, journalists and optical imaging experts. — Continue over at WiredScience
Spirogyra, a type of green algae, is common to freshwater areas and consists of over 400 currently described species. Spirogyra is so named because its light-absorbing chloroplasts are arranged in a prominent spiral shape running along the length of each cell. Commonly found in clean waters, this algae’s outer cell wall can dissolve in water, making it slimy to touch.
Image captured and submitted by Dennis Quertermous, University of Alabama.
(Image caption: Astrocyte activity is shown in green in this slice of tissue from the brain region that controls movement in mice. Internal, structural elements of the astrocytes are shown in magenta; cell bodies are in red. Credit: Amit Agarwal and Dwight Bergles, courtesy of Cell Press)
A new study from The Johns Hopkins University shows that the brain cells surrounding a mouse’s neurons do much more than fill space. According to the researchers, the cells, called astrocytes because of their star-shaped appearance, can monitor and respond to nearby neural activity, but only after being activated by the fight-or-flight chemical norepinephrine. Because astrocytes can alter the activity of neurons, the findings suggest that astrocytes may help control the brain’s ability to focus.
The study involved observing the cells in the brains of living, active mice over long periods of time. A combination of genetically engineered mice and advanced microscopy allowed the researchers to visualize the activity of astrocyte networks in different regions of the brain to learn how these abundant supporting cells are controlled.
The scientists monitored astrocytes in the area of the brain responsible for controlling movement and saw that the cells often increased their activity as the mice walked on treadmills — but not always, and sometimes astrocytes became active when the animals were not moving. This lack of consistency suggested to the researchers that the astrocytes were not responding to nearby neurons, as had been thought.
Similarly, astrocytes in the vision processing area of the brain did not necessarily become active when the mice were stimulated with light, but they were sometimes active, even in the dark. The team solved both mysteries when they tested the idea that the astrocytes needed a signal to “wake them up” before they could respond to nearby neurons. That is how they found that norepinephrine, the brain’s broadly distributed fight-or-flight signal, primes the astrocytes in both locations to “listen in” on nearby neuronal activity.
“Astrocytes are among the most abundant cells in the brain, but we know very little about how they are controlled and how they contribute to brain function,” says Dwight Bergles, Ph.D., professor of neuroscience, who led the study. “Since memory formation and other important functions of the brain require a state of attention, we’re interested in learning more about how astrocytes help create that state.”
For example, Bergles says, “We know that astrocytes can regulate local blood flow, provide energy to neurons and release signaling molecules that alter neuronal activity. They could be doing any or all of those things in response to being activated. It is also possible that they act as a sort of megaphone to broadcast local norepinephrine signals to every neuron in the brain.” Whatever the case may be, researchers now know that astrocytes are not idle loiterers. This ability to study astrocyte network activity in animals as they do different things will help to reveal how these cells contribute to brain function.
This research was published in the journal Neuron on June 18.
Inside the world of infection
Fungal pathogens manage to simultaneously pacify their plant victim’s defences whilst seizing host nutrition, creating a very difficult situation for any plant that becomes infected.
Here you can see three different stages of the fungal hyphae of Magnaporthe grisea invading and taking-over a plant cell.
Top panel: After 48h of infection
Middle panel: After 72h of infection
Bottom panel: After 96h of infection
Rice blast disease, which is caused by M.grisea, is one of the greatest pathogen threats to rice crops globally and since rice is an important food source its impact can be devastating.
Scientists from the Institute of Biological, Environmental and Rural Sciences at Aberystwth University, which is strategically funded by BBSRC, are studying the mechanisms behind fungal pathogen infection eventually hoping to reduce this major threat to modern agriculture.
Image from Mr Hassan Zubair from IBERS, Aberystwyth University
For more images of plant infection to go: