Thursday, May 28, 2009
Of all environments, space must be the most hostile: It is freezing cold, close to absolute zero, there is a vacuum, so no oxygen, and the amount of lethal radiation from stars is very high. This is why humans need to be carefully protected when they enter this environment.
New research by Ingemar Jönsson and colleagues published in the September 9 issue of Current Biology, a Cell Press journal, shows that some animals —the so-called tardigrades or 'water-bears'— are able to do away with space suits and can survive exposure to open-space vacuum, cold and radiation.
This is the first time that any animal has been tested for survival under open-space conditions. The test subjects were chosen with great care: Tardigrades —also known as water-bears— are tiny invertebrate animals from 0.1 to 1.5mm in size that can be easily found on wet lichens and mosses. Because their homes often fall dry, tardigrades are very resistant to drying out and can resurrect after years of dryness. Along with this amazing survival trick comes extreme resistance to heat, cold and radiation —so tardigrades seemed like an ideal animal to test in space.
The dried-up tardigrades were aboard the FOTON-M3 spacecraft launched by the European Space Agency (ESA) in September 2007 and were exposed to open space conditions —i.e. to vacuum, UV radiation from the sun and cosmic radiation— in a low Earth orbit of around 270km altitude. After their safe return to Earth, it turned out that while most of them survived exposure to vacuum and cosmic rays alone, some had even survived the exposure to the deadly levels of solar UV radiation, which are more than 1000 times higher than on the surface of the Earth. Even more so, the survivors could reproduce fine after their space trip.
The tardigrades extreme resistance to UV radiation is perhaps most surprising. UV rays consist of high-energy light particles that cause severe damage to tissue, as is evident when you get a sun-burn. But more so, they can also damage the cell's genetic material, causing for instance skin cancers. For this reason UV is deadly for most organisms —it is even used as a sterilising agent. As Jönsson and colleagues write: "How these animals were capable of reviving their body after receiving a dose of UV radiation of more than 7000 kJm-2 under space vacuum conditions […] remains a mystery." It is conceivable that the same cellular adaptations that let them survive drying out might also account for their overall hardiness.
Monday, May 25, 2009
Saltwater or estuarine crocodile (Crocodylus porosus) is the largest of all living crocodilians and reptiles. It is found in suitable habitats throughout Southeast Asia, Northern Australia, and the surrounding waters. The Alligator Rivers are misnamed after the resemblance of the saltwater crocodile to alligators as compared to freshwater crocodiles, which also inhabit the Northern Territory.
The saltwater crocodile has a longer muzzle than the mugger crocodile, and is twice the length of its breadth at the base. The saltwater crocodile has fewer armor plates on its neck than other crocodilians, and its broad body contrasts with that of most other lean crocodiles, leading to early unverified assumptions that the reptile was an alligator.
An adult male saltwater crocodile's weight is 880 to 3,000 pounds (400–1,360 kg) and length is normally 4 to 5.1 metres (13–17 ft), though very old males can be 6 metres (20 ft) or more. This species has the greatest sexual dimorphism of any modern crocodilian, with females being much smaller than males. Typical female body lengths in the range of 2.1 to 3.5 metres (6.9–11 ft). The largest female on record measured about 4.2 metres (14 ft). The mean weight of the species as a whole is roughly 450 kilograms (990 lb).
The largest size saltwater crocodiles can reach is the subject of considerable controversy. The longest crocodile ever measured snout-to-tail and verified was the skin of a deceased crocodile, which was 20 feet (6.1 m) long. Since skins tend to shrink slightly after removal from the carcass, this crocodile's living length was estimated at 20.7 feet (6.3 m) and it probably weighed well over 1,200 kilograms (2,600 lb). Incomplete remains (the skull of a crocodile shot in Orissa) have been claimed to come from a 7.6 metres (25 ft) crocodile, but scholarly examination suggested a length no greater than 7 metres (23 ft). There have been numerous claims of crocodiles in the 9 metres (30 ft) range: the individual shot in the Bay of Bengal in 1840, reported at 10 metres (33 ft); another killed in 1823 at Jala Jala on Luzon reported at 8.2 metres (27 ft); a reported 7.6 metres (25 ft) crocodile killed in the Hooghly River in the Alipore District of Calcutta. However, examinations of these animals' skulls actually indicated animals ranging from 6 to 6.6 metres (20–22 ft).
Saltwater crocodiles are very dangerous animals, but data on attacks is limited outside of Australia, and estimates of human fatalities vary wildly between dozens to thousands annually. It is likely that, given this species' low population within most of its non-Australian/New Guinean range, the number of attacks is probably within the lower range of estimates. Most attacks by adult "salties" are fatal, given the animals' size and strength. In Australia, attacks are rare and usually make headlines when they do occur.
Attacks on humans:
Dr. Adam Britton, a researcher with Big Gecko, has been studying crocodilian intelligence. In so doing, he has compiled a collection of Australian saltwater crocodile calls, and associated them with behaviors. His position is that while crocodilian brains are much smaller than those of mammals (as low as 0.05% of body weight in the saltwater crocodile), they are capable of learning difficult tasks with very little conditioning. He also infers that the crocodile calls hint at a deeper language ability than currently accepted. He suggests that saltwater crocodiles are clever animals that can possibly learn faster than lab rats. They have also learned to track the migratory route of their prey as the climate changes.
Wednesday, May 20, 2009
The Leopard seal (Hydrurga leptonyx) is the second largest species of seal in the Antarctic (after the Southern Elephant Seal), and is near the top of the Antarctic food chain. It is most common in the southern hemisphere along the coast of Antarctica and on most sub-Antarctic islands. It can live twenty-six years, possibly more. Orcas are the only natural predators of leopard seals.
The leopard seal is large and muscular, with a dark grey back and light grey on its stomach. Its throat is whitish with the black spots that give the seal its common name. Females are generally slightly larger than the males on average. The bulls are generally 2.5 m (8.2 ft) to 3.2 m (10.5 ft) and weigh between 200 kg (441 lb) and 453.5 kg (1,000 lb), while cows are between 2.4 meters (7.9 feet) and 3.4 meters (11.2 feet) in length and weigh between 225 kg (496 lb) and 591 kg (1,303 lb). 
Compared to most phocids, the Leopard seal is highly evolved for its role as keystone predator. Although it is a true seal and swims with its hind limbs, it has powerful and highly developed forelimbs similar to sea lions, giving it a similar maneuverability, a classic example of convergent evolution.
In 2003, a leopard seal dragged a snorkeling biologist underwater to her death in what was identified as the first known human fatality from a leopard seal. However, numerous examples of aggressive behavior, stalking, and attacks on humans had been previously documented. The leopard seal has previously shown a particular predilection for attacking the black, torpedo-shaped pontoons of rigid inflatable boats, necessitating that researchers equip their craft with special protective guards to prevent them from being punctured. The leopard seal has also been known to snap at people's feet through holes in the ice.
This seal is dangerous.
Tuesday, May 19, 2009
The Tasmanian tiger or Thylacine was by far the largest carnivorous marsupial of recent times. Its overall appearance is very canid-like. Total body length is around 1 meter. The tail length is around 50-65 cm. The tail itself is very thick close to the body and quickly tapers to a point. It is around 60 cm in height at the shoulder. The upper body is brownish/grey with a pale underside. There are 13-19 black vertical stripes that run from the mid-back to the base of the tail. The face is grey with white markings around the eyes. The fur is short and thick. Their skull has a length of 22 cm and the dental formula is: i 4/3, c 1/1, pm 3/3, m 4/4. Tasmanian tiger's long canines, shearing premolars, and grinding molars, all of which are quite similar to those of dogs. The feet are padded and leave a five-toed print. The females pouch is located by her tail and has a fold of skin covering the four mammae.
Tasmanian tigers lived only on the island of Tasmania in recent history, but fossil record shows that it was also found in New Guinea and Australia as recently as 3000 years ago. Competition with dogs brought by aborigines eliminated it in Australia and New Guinea. These dogs ran wild, becoming the dingo, which entirely filled its niche. A large population survived on Tasmania, where there are no dingoes. But when the Europeans arrived and settled in Australia and Tasmania the Tasmanian tiger was thought to be a livestock killer, especially when sheep were introduced in 1824. This was never substantiated, but because of this misconception the privet sector and the government hunted the Tasmanian tiger from 1830-1909 for bounty. In 1830, the Van Diemens Land Company, a pastoral company in Northwest Tasmania, introduces the first bounty on the Tasmanian tiger, claiming that the animal attacked sheep.
Extinction may not be forever after all; so hope the Australian scientists behind an ambitious project to clone the extinct Tasmanian tiger.
The project to bring the Tasmanian tiger back from extinction began in 1999 when Australian Museum scientists extracted DNA from an ethanol-preserved female pup in its collection.
We will see in a future if it is possible it to come back to the life, or as it has been said in several mass media, it is possible that the wolf marsupial is living , hidden from the man.Look that beautiful
Monday, May 18, 2009
Jaguars are the largest of South America's big cats. They once roamed from the southern tip of that continent north to the region surrounding the U.S.-Mexico border. Today significant numbers of jaguars are found only in remote regions of South and Central America—particularly in the Amazon basin.
These beautiful and powerful beasts were prominent in ancient Native American cultures. In some traditions the Jaguar God of the Night was the formidable lord of the underworld. The name jaguar is derived from the Native American word yaguar, which means "he who kills with one leap."
Unlike many other cats, jaguars do not avoid water; in fact, they are quite good swimmers. Rivers provide prey in the form of fish, turtles, or caimans—small, alligatorlike animals. Jaguars also eat larger animals such as deer, peccaries, capybaras, and tapirs. They sometimes climb trees to prepare an ambush, killing their prey with one powerful bite.
Most jaguars are tan or orange with distinctive black spots, dubbed "rosettes" because they are shaped like roses. Some jaguars are so dark they appear to be spotless, though their markings can be seen on closer inspection.
Jaguars are still hunted for their attractive fur. Ranchers also kill them because the cats sometimes prey upon their livestock.