Saturday, August 30, 2008

The Mysteries Of Camouflage And Mimicry

In nature, any species is sought after by other predator or prey species, which detect it through their senses (sight, hearing, smell). Victims can defend through venoms, unpleasant smells, run, or by deceiving the sensory input of their predators. One method is camouflage and mimicry. It is a balance between prey and predator bypassing this defense.

To camouflage (homochromy) in order to escape predators or to surprise the possible preys is to melt into the hues and shapes of the environment. The method can be simple or elaborated (the inversed shadow), making the animal melt into its environment.

Polar animals, like the polar bear and polar owl, are white. In the savanna, lions employ camouflage. They remain for large periods of time immobile in the bush without anybody being aware they are there, due to their tawny color. This tactic is especially efficient during the dry season, when the prey is scarce and the lions cannot afford losing food for being detected early by their prey. The same camouflage color is used by the African ground squirrels or prairie dogs, which use the autumn hues in their coat for deceiving predators.

Many insects (like grasshopers), snakes and birds (like parrots) have a green color that makes them difficult to distinguish in the grass or in the forest. Movie makers spend a lot of time detecting a leopard in the wild, even if they are abundant in an area... Most bottom fishes, like rays and angelfish, cannot be distinguished from the substrate. Some animals have cryptic shadow: they are dark above and light below, like tuna and many other fishes.

Homochromy can change with the season, like the ptarmigan and arctic hare, which are brown in the summer and white during winter.

Homotypy goes further than camouflage: the animals copy natural elements or plant organs with an amazing precision. Stick insects really look like a stick (their name Phasmatodea comes from the Greek "phasma" "phantom") and even imitate during their movements the shaking of a stick blown by the wind. Some Thai stick insects even mimic dead branches covered by lichens. The same imitation is made by some caterpillars and beetles (like Petrognatha gigas of western Africa). Leaf insects not only imitate a green leaf with nerves, but also the attack of fungi on the imaginary leaf! The same patterns are achieved by some Brazilian locusts.

The leafy sea dragons, relatives of the sea horses, can be differentiated with difficulty from algae.

Orchid mantis (Hymenopus coronatus) from southeastern Asia mimics so well a pink flower, that pollinating insects go straight into the killing arms of this predator, while others praying mantis from the same are mimic tree bark. Many moths too mimic tree bark.

Some caterpillars replace a plant bud before turning into a cocoon and the cocoon looks exactly like the replaced bud.
The tiny black toads (Oreophrynella) from the Roraima tepui in Venezuela have the color and texture of the rocks on which they live and this is also the case with many butterflies and the tree bark or dead leaves.

Some butterflies from Costa Rica completely lack color, being completely transparent. The frogmouths from Australia and nightjars have a plumage that makes them difficult to distinguish from the tree bark.

The chameleons' ability to change color is well-known, depending in which environment they are found at a given moment. But they are amateurs compared to the ability of the octopuses, cuttlefish or flounders.

Some animals play dead as an active method of defense: many predators will only eat prey which is alive...The opossum is the most famous when it comes to playing dead, hence the term "playing possum". Many snakes, too, use this strategy, and besides the immobility, they expel through some anal glands a decomposing corpse scent... Besides discouraging animals that eat only living prey, playing possum also convinces some large animals that the individual is no threat to their young.
Many insects (like wasps or caterpillars), spiders, venomous fish and snakes (like kraits and coral snakes) and toxic amphibians (like salamanders, fire-bellied toads and poison dart frogs) warn about their toxicity through bright colors and elaborated patterns.

That's why many species have developed mimicry: imitating the colors and patterns of the real dangerous animals, so that their predators won't attack them, being deceived.

There are flies imitating the color of the wasps and many non-toxic butterflies imitating toxic species of butterflies. Over 15 genera of non-venomous snakes imitate in Americas the model of the highly venomous coral snakes... The Myrmecium spiders mimic nasty ants.

There are even non-toxic moths imitating the ultrasounds emitted by toxic moths, being avoided this way by the bats. Sometimes, the predator imitates the prey, to get closer easier, like in the case of some beetles. Some parasite flies imitate the bumble bees in whose nest they depose their eggs.
The caterpillar of a hawk moth, Hemeroplanes ornapus, from Central America, has a length of 8-10 cm (3.2-4 in). When menaced, the pseudopods of the rear part hold the body (using sucking cups), while the thorax dilates to maximum, and this coupled with two fake shiny eyes and the hanging of the fore part of the body, make the caterpillar resemble a small snake.

Saturday, July 19, 2008

Cleopatra's Mystery Lives On

Reports of Cleopatra's beauty are apparently exaggerated, according to articles published in the British media. On the occasion of her exhibition this month in the British Museum in London, some reports in the media would have us believe that Cleopatra was hook-nosed, dumpy and had bad teeth!
A report in a "quality" publication said that "Cleopatra, the queen of ancient Egypt who seduced Julius Caesar and Mark Anthony with her supposedly irresistible beauty, has been revealed as short, frumpish and in need of a good dentist.. eleven statues show the queen as plain looking with a streak of sterness, and (she) appears to be plump".
Yet, throughout the lengthy reports, no hard evidence was given for the ugly cartoons published supposedly depicting the legendary queen. Furthermore, no explanation has been given for her magical influence and ability to seduce the most powerful men of her time. Her charm was attributed only to strength of character and mental charisma.
Even the statues on display and the coins carrying Cleopatra's head show a royal looking image with firm features and wide eyes. There may be a slight exaggeration of the nose proportion in one of the statues, but the coin illustrates a fine pointed nose, in good proportion to the face. Cleopatra was certainly not ugly.
Unless it is a publicity stunt for the exhibition, no self-respecting Egyptologist would take such descriptions of Cleopatra seriously. Even the curators of the British Museum admit that very few portraits of the queen survived, and they are anything but consistent. The evidence of contemporary description of Cleopatra was discounted out of hand, in these reports, because the writers, such as Cicero, were born a few years after Cleopatra's death. There was mention of her irresistible charm, her seductive voice and eloquent speech. Cicero wrote in the first century BC:
"Her character, which pervaded her actions in an inexplicable way when meeting people, was utterly spellbinding. The sound of her voice was sweet when she talked".
The evidence given for being fat, is also flimsy. Her ancestors were believed to suffer from weight problems! There is also no evidence of Cleopatra being only 5 ft. tall, except a description in a recent catalogue that she was "petite". As for the alleged teeth problem, that was attributed to "…eating the awful Egyptian bread"! In the same report, the ancient queen was described as "…taking care of herself. Her diet, including plenty of fruit and vegetables as well as fish and meat, was healthily balanced". This apparent contradiction was not explained by the writer.
The issue of Cleopatra's beauty is beyond doubt. The love of two powerful men of her era testified to that. Caesar went as far as putting up a golden statue of Cleopatra in the Temple of Venus in Rome, making her the first living human to share a temple with a Roman God - a frank recognition of her divinity and beauty by Caesar himself.

Tuesday, June 3, 2008

The Mystery of River Nile

This river is the maker of the oldest civilization recorded by the historical sources: 5,000 years ago, the Egyptian state emerged on its banks. It is best known as the longest river on the planet. Nile is consensually considered so as it has 6,695 km in length, even if some say that Amazon is longer (6,800 km). The problem is that nobody could tell where Amazon ends, due to its huge mouth. Anyway, while Amazon is the mightiest river on the planet (with a debit of 200,000 cubic meters/second, 20 % of the freshwater volume penetrating the oceans), Nile has a 60 times lower debit, as it does not receive any affluent on its last 2.400 km (1.500 mi). Moreover, the Nile's debits fluctuate a lot, as it receives the most abundant waters during the rainfall on the Ethiopian Plateau. But the role played by the Nile in human life and history is much more important. The Nile starts from molten snow and rainfall, which make torrents like Mobuku and Semliki in the Ruwenzori Mountain (a glacier-covered equatorial mountain, with a maximum height of 5,119 m / 17,633 ft). Semliki enters Lake Albert. Another southern source is located in Burundi, at a height of 2,050 m (6,830 ft): Kasumo. Then, from the large Lake Victoria, the Nile starts under the name Kagera for emptying itself into the Mediterranean, on the place where 2,300 years ago Alexander the Great founded the famous city of Alexandria. The river crosses Burundi, Uganda, Sudan and Ethiopia before entering Egypt. From Lake Victoria, the Nile starts through cascades that are 4 m (13 ft) tall and 150 m (500 ft) wide. The Nile enters Lake Kyoga, which acts like
a sponge. Further, two granite bars make a strait, just 6 m (20 ft) wide, making the Nile fall from 40 m (133 ft), forming the Murchinson Falls. Further on, the Nile enters Lake Albert and from this lake, it heads northward. The Nile is swift in this portion, being called Bahr-el-Gebel (the river of the mountains). Then, the Nile crosses a huge area of swamps, called "Sadd" (halt) by the Arabs. This is a world dominated by papyrus twice the height of a man. The area is as large as the Sargasso Sea and is difficult for navigation.After 750 km (480 mi), with the No Lake, the world of the swamps has ended. Until the confluence with the Blue Nile, the proper Nile is called the White Nile (Bahr-el-Abiad). The river has lost much of its forces in the swamps as much of its waters evaporate here. But it is strengthened by Sobat River, an affluent coming from Ethiopia. It is so large now that the Arabs call it "Bahr" (sea). The river has crossed 2,600 km (1,650 mi) and the landscape along its banks turns gradually from steppes to desert, while "Black Africa" turns into the world of the Islam. After the dam Gebel Aulia, the Nile approaches Khartoum, where it will be joined by the Blue Nile. There are more 3,000 km (1,900 mi) to the Mediterranean. The Blue Nile has 1,500 km (900 mi) and its source is in Sakala (Ethiopia), a sacred place for the Ethiopian Christians. After emerging at the height of 2,900 m (9,660 ft), it crosses Lake Tana (at 1,760 m (5,860 ft). From Lake Tana, the river crosses various cascades. In Sudan it is called Bahr-elAzrak (ashy river). The two Niles join after the second bridge of Khartoum. The Blue Nile comes with a daily debit of 141 million cubic meters of water, representing 80 % of the total debit of the Nile. The river is called after the confluence Bahr-el-Nil. In Karthoum, Nile receives also its last affluent: Atbara River, coming filled with mud (varying from red to green) from the Ethiopian Plateau. Now the Nile is 2-4 km (1.2-2.4 mi) wide and is spotted with islands. Through the desert crossed by the Nile, vegetation growth is restricted at a fringe of about 1.5 km (1 mi) along the river's banks and life is concentrated on a strip few km wide alongside the banks. From Khartoum, the Sudanese capital, to Assouan, 6 cataracts are found on the Nile. The first cataract is located 200 km (125 mi) north of Khartoum. On the fifth cataracts, papyrus beds, gone from Egypt since the time of the pharaohs, can still be seen.
This portion in northern Sudan is the area were the ancient kingdom of Nubia flourished. For a while, even Egypt was ruled by Black Nubian pharaohs. One of the longest reservoirs on Earth was built at Assouan on the Nile from 1958 to 1970: Lake Nasser, which is 550 km (344 mi) long and with a maximum width of 35 km (22 mi). The reservoirs lay between Egypt (mostly) and Sudan, and required the removal of the temples of Abu Simbel to a 64 m (213 ft) higher place. The Nile made possible the development of the oldest state known, Egypt, in the middle of the Sahara desert, one of the toughest on Earth. But the Egyptian civilization thrived on its banks 10,000 years ago, while the Egyptian empire rose 5,000 years ago. 12,000 years ago the Nile was much stronger, crossing a savanna, where nowadays we see only dry desert, and receiving numerous strong affluents on its course. But 10,000 years ago the drought was already felt. 6,000 years ago, two cultures were known in Egypt: the Merimde Culture in the north, around Nile's Delta and Badarian Culture in the middle Egypt, around the city of Asyut. From the union of these two cultures, the first great nation-state in the history rose, flourishing for three millennia and leaving us awesome monuments, like the monumental pyramids at the Abu Simbel, Karnak, Philae. The agriculture in the Nile Valley was strictly connected to the annual flooding, which occurred between July and September, covering huge areas. The inundations meant the Egyptian agriculture did not require irrigations. Still, some crops required stocking water and irrigation. Of course, the Nile was for the Egyptians the backbone of their unity and the main transport route. The Nile allowed a centralization of the political, military and economical power that permitted the emergence of a huge trained work power necessary for the building of the huge monuments, priceless values of the human civilization. Due to the steady food supply provided by the fertilizing Nile, Egypt was one of the most stable ancient states till its conquest by the Romans led by Julius Caesar in 30 B.C. Even today, Egypt is the most populous country in the Middle East and North Africa, due to Nile that can provide the food (directly and indirectly) for such a large population. At Cairo, the Nile is just 800 m (0.5 mi) wide. Its meanders are hidden by the high buildings. Many changes have occurred in the last decades: new canals, dams and bridges. Nile Delta, made by the two mouth of the river, Rosette and Damiette, is a triangle with the side of 200 km (125 mi). 20 million people inhabit this "agricultural lung". The delta is crossed by a network of smaller arms, canals and ditches. From its forking point, the Nile still has to make 500 km (310 mi). The Eastern Nile heads northwards after Zifta dam, avoiding Tantah, a quite contaminated industrial center, but crossing Mansurah, a 200,000 inhabitants city, joining Lake Menzaleh, and then reaching Damiette, a furniture center, before entering the Mediterranean. The western Nile, after Sa el-Hagar (built over the ancient Sais) encounters the Edfina dam, which protects the fields from the invasion of the sea waters. Still, in the last decades, the salinity of the irrigation waters has risen. Through the palm oases, the branch reaches Rosette, a town turned famous because here the famous hieroglyph basalt stone, used by Champollion to decode the ancient Egyptian hieroglyphs was discovered. Here, at Rosette, the Nile is as wide as in Cairo, with banks invaded by palm trees.

Friday, May 30, 2008

A Mystery -The Petrified Forest

One of the wonders of the American southwest is found in northeastern Arizona: an enormous petrified forest, a real geological treasure the scientists learned about to the end of the 19th century.
Petrified Forest National Park from Arizona comprises a surface of 218,533 acres (341.5 sq mi; 885 km²) of petrified wood, mostly of the coniferous species Araucarioxylon arizonicum, 170 million years old, since the Jurassic epoch. In some moment, whole forests were flooded. These conditions made the wood to get mineralized, turning into quartz, jasper and agate. Normally, the wood would have turned into coal. After that, the forest was covered by red and yellow sediments, which later were removed by wind and water. This explains the preservation of the fossil wood and the large variety of colors some specimens exhibit. The red and yellow hues are the result of large particulate forms of iron oxide, the yellow being limonite and the red being hematite. The purple hue is caused by extremely fine spherules of hematite distributed throughout the quartz matrix.The trunks did not grow there, but were carried by waters, which piled them, making deposits up to 50 m (160 ft) thick. But in this case, it was mineralized. For its exceptional beauty, the petrified wood was early exploited for making furniture, jewels and art objects. Large surfaces of the petrified forest were even dynamited. In 1906, the area was declared National Monument (protected by law) and in 1962 its status was turned into National Park. With all the protective measures, the stealing of the fossil wood continued, the statistic confirming that annually 12 tonnes of the petrified wood are extracted illegally. Araucarioxylon were trees 60 m (200 ft) high that measured more than 60 cm (2 ft) in diameter. Fossils frequently show boreholes of insects, as well as fossilized hives of prehistoric bees.The genus Araucarioxylon is close or even synonymous to the modern genus Araucaria, which today is restricted to southern South America, Australia, New Caledonia, New Zealand and Norfolk Island.

Thursday, April 24, 2008

Deep Mystery : How Can French Clay Kill Flesh-eating Bacteria?

When the Buruli ulcer, nasty flesh-eating eruptions of Mycobacterium ulcerans, broke out in Ivory Coast a decade ago, two French green clays worked best, removing the specter of surgery or amputation. One clay induced excruciating pain, but in several days it induced skin tissue regeneration on the open wound. A second variety, mixed with shea butter (a plant oil), induced no pain and cured the oozing ulcer in several months. In France, these iron-rich clays have been used for centuries.Now a team led by mineralogist Lynda Williams of Arizona State University (A.S.U.) in Tempe has been attempting to explain the healing powers of the French clays."This clay was unique in that they were very small particle size, 200 nanometers, or 1/400 the width of a human hair," said Williams. The producer companies (Agriletz and Agricur) did not expose the source of the clays, but French mineralogists guess they are made of volcanic ash deposits from the French Massif Central. First tests were made on Escherichia coli, the all-over present food infecting bacteria, but after that on all kinds of bacteria, from Salmonella to antibiotic-resistant Staphylococcus aureus. "That's when we first discovered that the first clay promoted bacterial growth and the second killed it," said Wiliams. "The strains that we are using are the same ones that pharmaceutical companies use to test their antibiotics. All of the gram-negative pathogenic bacteria to humans that we've tested, we can kill completely." said co-author Shelley Haydel, A.S.U. microbiologist. Like many antibiotics, the clay stopped the reproduction of those bacteria it could not kill. "The number of cells we start with is 107 Staphylococcus aureus. After 24 hours, that level reduces tenfold." said Haydel. But the tests have not solved the puzzle: how do they do it? Chemical analysis found no particular minerals or metals in the clay explaining the antibacterial powers and added water did not affect this effect.
The killing powers were preserved even when the clays were heated to over 1,000o F (550o C), but lost over 1,650o F (900o C), when the clay's structure was affected, leaving behind only the heaviest elements, like radioactive cesium, selenium and toxic arsenic. "E. coli can tolerate 200 parts per million and we're talking about 50 ppm. The clay's antibacterial effect appears to be chemical rather than physical, because its strength diminishes as it loses positively charged molecules and it does not smother the bacteria or cause its cell walls to burst. After six hours, you can see a [bacterial cell] surface that is kind of wormy or grainy. It doesn't look like something is precipitating at the surface. Maybe something is going into the cell and damaging it that way." said Williams. The clay could combine the antibacterial powers of its many various elements. "I think these clays are buffering water to keep whatever's toxic to bacteria in there. If we remove the clay from water, I think it's not going to work." said Williams.
The age also affects the clays' power. "We went back and got some from the same batch and it didn't kill. This clay has been sitting outside in a pile for 10 years. It could have oxidized and maybe the oxidation state has affected the antibacterial properties." said Williams. Two other clays with similar antibacterial powers have been detected. "They're all different mineralogically, though they have a general structure in common. We're trying to compare the properties of these antibacterial clays and see what's going on." said Williams. Researchers do not neglect the variant that clays could boost the human immune system reaction to the infection, which M. ulcerans can inhibit. "Even if you removed the antibacterial properties, do the clays have any effect on wound healing? What is the body's response? Are you stimulating tissue regeneration? We already use maggots and leeches in hospitals. Why don't we use clays?" said Haydel.

Wednesday, April 16, 2008

The Mysteries of Chinese Writing

Chinese writing is thought to have resisted for 4,500 years. And the greatest danger for it was the attempt of replacing it with the Latin script. But this did not work due to ethno-political reasons: while those from the Han ethnic group regard themselves as Chinese proper, they speak 13 different languages (not dialects!), even if amongst them, Mandarin is the most spoken and official. The phonetic Latin writing revealed they cannot understand one another by speech but by their common writing, which makes use of about 5,000 morphemes. Combinations of characters create Chinese words.
From the time of Qin Dynasty (which give the western name of China) onwards, a standard written language has filled the gaps between the various Chinese languages.But now Chinese archaeologists investigating ancient rock carvings claim that they have discovered proofs that modern Chinese script is thousands of years older than people believed. Scientists have detected over 2,000 pictorial symbols, as old as 8,000 years, on cliff faces in the north-west of China. The ancient symbols display a strong similarity to later morphs of ancient Chinese characters. Scholars had thought Chinese symbols came into use about 4,500 years ago. Based on the Damaidi carvings, found in the 1980s, covering 15 sq km (5.8 square miles) and depicting over 8,000 individual figures like the sun, moon, stars, gods and scenes of hunting or grazing, it was believed that the Chinese writing is about 4,500 years old and pottery inscriptions from Henan province (central China) were of similar age . "We have found some symbols shaped like both pictures and characters," Li Xiangshi, a cliff carving expert at the North University of Nationalities in Ningxia Hui autonomous region, told Xinhua news agency. "The pictographs are similar to the ancient hieroglyphs of Chinese characters and many can be identified as ancient characters." To make a comparison, the Greek script is about 3,000 years old. The Latin script, based on the Greek, is even younger, about 2,500 years old. The Arab script is younger, almost 1,500 years old.

Saturday, April 12, 2008

The Mysterious Colours Of Autumn Leaves

Every autumn we look in melancholy at the falling leaves. But before falling, the leaves get yellow and orange with shades of red. But why this diversity in the color of the fallen leaves? The undergraduate research project of Emily Habinck at the University of North Carolina at Charlotte, revealed that the color of the autumn leaf was connected to the amount of nutrients in the soil. She found that on a North Carolina
floodplain with a soil abundant in nitrate (a nutrient that delivers nitrogen to the plants), yellow was the dominant color in the autumn "carpet", while the hillside, with poorer soils, were dominated by red during the fall. Even trees with typical red autumn leaves had even redder hues on poorer soils. A 2006 research led by William Hoch, a plant physiologist at Montana State University, connected the synthesis of anthocyanin red pigments in leaves to fall sunlight. "It wasn't until I read his paper that it became a full story," Habinck said. Leaves change color in the fall when trees stop the photosynthesis while withdrawing their nutrients from the leaves to be stored into their roots. "[The tree] pulls as many of these in as it can, then tries to drop just a skeleton of a leaf when it's done", Hoch told National Geographic. But the food withdrawal is not a rapid process, and in the meantime, leaves are left vulnerable to harmful light waves. "Anthocyanins protect leaves by "shading" them from excessive sunlight during the plant's relatively vulnerable autumn season," Hoch explained.Plants genetically engineered not to synthesize anthocyanins could not withdraw as many nutrients from their leaves. "So the bottom line is that the plants that were able to produce red pigments were able to squeeze more of the nutrients out of their leaves than the ones that couldn't. Thus, plants living in nutrient-poor soils benefit more from anthocyanin than those living on better soils.", said Hoch. "Scientists only recently made these connections, because when most other leaf-peepers are taking their fall-color tours, biologists are busy with academics. Most people's field season is in the summer," said Habinck.