Hydra is a genus of small, simple, fresh-water animals that possess radial symmetry. Hydra are predatory animals belonging to the phylum Cnidaria and the class Hydrozoa. They can be found in most unpolluted fresh-water ponds, lakes, and streams in the temperate and tropical regions and can be found by gently sweeping a collecting net through weedy areas. They are multicellular organisms which are usually a few millimetres long and are best studied with a microscope. Biologists are especially interested in Hydra due to their regenerative ability; and that they appear not to age or to die of old age.
Hydra has a tubular body up to 10 mm (0.39 in) long when extended, secured by a simple adhesive foot called the basal disc. Gland cells in the basal disc secrete a sticky fluid that accounts for its adhesive properties.
At the free end of the body is a mouth opening surrounded by one to twelve thin, mobile tentacles. Each tentacle, or cnida (plural: cnidae), is clothed with highly specialised stinging cells called cnidocytes. Cnidocytes contain specialized structures called nematocysts, which look like miniature light bulbs with a coiled thread inside. At the narrow outer edge of the cnidocyte is a short trigger hair called a cnidocil. Upon contact with prey, the contents of the nematocyst are explosively discharged, firing a dart-like thread containing neurotoxins into whatever triggered the release which can paralyse the prey, especially if many hundreds of nematocysts are fired.
Hydra has two main body layers, which makes it “diploblastic”. The layers are separated by mesoglea, a gel-like substance. The outer layer is the epidermis, and the inner layer is called the gastrodermis, because it lines the stomach. The cells making up these two body layers are relatively simple. Hydramacin is a bactericide recently discovered in Hydra; it protects the outer layer against infection.
The nervous system of Hydra is a nerve net, which is structurally simple compared to mammalian nervous systems. Hydra does not have a recognizable brain or true muscles. Nerve nets connect sensory photoreceptors and touch-sensitive nerve cells located in the body wall and tentacles.
from Rare Animals
PUBLISHED JULY 18, 2014
Cast into northern European wetlands, bog bodies have long appeared as opaque to archaeologists as their dark and watery graves. But new clues are coming in the centuries-old mystery of their origins.
Over 500 Iron Age bog bodies and skeletons dating to between 800 B.C. and A.D. 200 have been discovered in Denmark alone, with more unearthed in Germany, the Netherlands, the United Kingdom, and Ireland. (Read “Tales From the Bog” in National Geographic magazine.)
Much of the bodies’ skin, hair, clothes, and stomach contents have been remarkably well preserved, thanks to the acidic, oxygen-poor conditions of peat bogs, which are made up of accumulated layers of dead moss.
Tollund Man, for example, found in 1950 on Denmark’s Jutland Peninsula and perhaps the most famous bog body in the world, still “has this three-day beard—you feel he will open his eyes and talk to you. It’s something that not even Tutankhamun could make you feel,” said Karin Margarita Frei, a research scientist who studies bog bodies at the National Museum of Denmark.
In Denmark, about 30 of these naturally mummified corpses are housed in museums, where scientists have worked for decades to figure out who these people were and why they died.
Because some bear horrific wounds, such as slashed throats, and were buried instead of cremated like most others in their communities, scientists have suggested the bodies had been sacrificed as criminals, slaves, or simply commoners. The Roman historian Tacitus started this idea in the first century A.D. by suggesting they were deserters and criminals. (See National Geographic’s pictures of bog bodies.)
But ongoing research is uncovering an entirely new dimension: When alive, these people of the bog may have instead been special members of their villages, which in the early Iron Age were loosely scattered across Denmark.
New chemical analyses applied to two of the Danish bog bodies,Huldremose Woman and Haraldskær Woman, show that they had traveled long distances before their deaths. What’s more, some of their clothing had been made in foreign lands and was more elaborate than previously thought.
"You sacrifice something that is meaningful and has a lot of value. So maybe people who [had] traveled had a lot of value," Frei told National Geographic at the Euroscience Open Forum in Copenhagen in June.
For Europeans dating as far back as the Neolithic period 6,000 years ago, bogs were both resources and possibly ominous supernatural portals, according to Ulla Mannering, an expert in ancient textiles at the National Museum of Denmark.
The bogs’ peat, which could be burned for heating homes, was valuable in tree-scarce Denmark, and an ore called bog iron was made into tools and weapons.
Among prehistoric people, “when you take things, you also offer things,” said Mannering.
This may be why the Danish villagers would deposit “gifts” of clothes, old shoes, slaughtered animals, battered weapons, and, for a period of 500 years, people into the black abyss of the bogs. (Related:"Medieval Christian Book Discovered in Ireland Bog.")
Danish Iron Age cultures left no written records, so their religious beliefs are unknown, Mannering noted.
"Very Fine Lady"
When peat harvesters began accidentally unearthing bog bodies in the mid to late 1800s, many were discovered without clothing, solidifying the view that they had been simple people, Frei said. (Watch a National Geographic Channel video about bog mummies.)
Tollund Man, for instance, was found with a belt but no clothes. “It doesn’t make sense to be naked and have a belt,” Frei pointed out.
Frei wondered, then, if some of the bog bodies’ clothing had dissolved in the bogs over the centuries. So she decided to examine Huldremose Woman, a mummy discovered in 1879 wearing a checkered skirt and scarf, both made of sheep’s wool, and two leather capes.
Using microscopes, she discovered that tiny plant fibers were stuck to the 2,300-year-old woman’s skin—remnants of ancient underwear, which later analyses revealed were likely made of flax.
Next, Frei performed a first-of-its-kind analysis of the strontium isotope contained in the flax and in the wool from the skirt and scarf.
Researchers analyzed the isotopes, or different varieties, of atoms in the strontium preserved in the flax and wool fibers. These atoms provide a chemical insight into the geology of the region where the plant and sheep lived.
The results show that the plant fibers taken from threads of the underwear grew on terrains geologically older than those of Denmark—those typical of northern Scandinavia, such as Norway or Sweden—suggesting that Huldremose Woman may have come from somewhere else, according to research published in 2009 in the Journal of Archaeological Science.
Frei also did an analysis of strontium isotopes in Huldremose Woman’s skin. Humans absorb strontium through food and water, and it’s especially prevalent in our teeth and bones—though many bog bodies are found without teeth and bones because of the acidic conditions.
read more from Nat Geo
Microbiologists based in California have discovered bacteria that survive by eating pure electrons rather than food, bringing an entirely new method of existence to awareness and raising questions about possibilities for alien life.
The ‘electric bacteria’ – as they have been dubbed by the team that discovered them – take energy from rocks and metal by feasting directly on their electrons. The hair-like filaments the bacteria produce carry electrons between the cells and their environment.
The biologists from the University of Southern California (USC) found that the new discovery joins more than ten other different specific type of bacteria that also feed on electricity – although none in quite the same way.
“This is huge. What it means is that there’s a whole part of the microbial world that we don’t know about,”Kenneth Nealson of USC told New Scientist.
Nealson explained the process by which the bacteria function. “You eat sugars that have excess electrons, and you breathe in oxygen that willingly takes them,” he said. Human cells break down the sugars in order to obtain the electrons – making the bacteria that only absorb the electrons that much more efficient.
“That’s the way we make all our energy and it’s the same for every organism on this planet,” Nealson said. “Electrons must flow in order for energy to be gained.”
Some of the bacteria even have the ability to make ‘bio-cables’ – a kind of microbial collection of wires that can conduct electricity as well as copper – renowned for its high electrical conductivity.
Such ‘nanowires’ were first discovered in a separate study conducted by researchers at Aarhus University in Denmark. Their presence raises the possibility that one day bacteria could be used in making subsurface networks for people to use.
“Tens of thousands of bacteria can join to form a cable that can carry electrons over several centimeters,” the New Scientist video on the subject points out.
read more from RT
New Zealand’s hot pools are some of most extreme ecosystems on Earth, with salty, acidic water up to 90 degrees Celsius. Now University of Waikato scientists are studying the bacteria that can survive in them in the hopes of finding the key to future medicines and scientific breakthroughs: http://bit.ly/VE7dbr