février 2016 ~ sciencelovers

dimanche 28 février 2016

Spider

23:58:00 kais

Home is where the heart is. And it’s also where the beetles, spiders, ants and flies are.

A study published Tuesday in the journal Peerj by researchers at North Carolina State University found that we share our houses with over 500 species of arthropods — you know, insects, spiders and other creepy crawlies. In the first study of its kind, the researchers visited 50 homes near Raleigh, North Carolina and searched high and low for multi-legged cohabitants, ending up with more than 10,000 samples.

Unexpected Insect Diversity

Analyzing the collected samples one by one turned up a staggering array of arthropods, comprising not only common species like house flies and dust mites but also crickets, aphids, lacewings and hundreds more. In all, they found 6 classes of arthropods with 34 orders and 304 families represented. Houses averaged 62 families apiece. Although they found over 500 species in homes in total, only a little more than 200 were present in any one house, with an average of around 100.

All of the 50 houses sampled contained ants, beetles, flies and spiders, although the species of each varied. Common arthropod guests included silverfish, cockroaches and mosquitos, and all but two percent of households had some form of lice. In all, only 5 out of 554 rooms sampled turned up no results at all.

Here’s more unsettling news about your segmented roommates: Researchers noted that their results are based on conservative estimates of arthropod populations, meaning there are likely many more species represented in houses across the country. They also searched only in open spaces, leaving out insect-friendly locales such as the insides of walls and underneath furniture.

The researchers say that some of the most common species they found in the houses studied have also been discovered at archaeological sites, indicating a long history of cohabitation with humans.

Leopard

02:00:00 kais

VICTIMES. Une double rangée de clôtures coiffées de barbelés comme une longue balafre sur les montagnes enneigées du Cachemire : cette frontière, l'une des plus militarisées au monde, a sectionné en deux le territoire de la faune de la région. Construite en 2007 par l'Inde, l'infranchissable barrière court sur des centaines de kilomètres au milieu des sapins, empêchant les groupes armés séparatistes de s'infiltrer depuis le Pakistan voisin. Mais elle bloque aussi la migration de nombre d'espèces autrefois abondantes dans la région, entraînant ainsi leur déclin, selon des experts en vie animale. À défaut d'écumer librement la région himalayenne, des ours bruns ou des léopards, coincés côté pakistanais, en sont réduits en période de disette à s'approcher des villages, ce qui leur coûte souvent la vie...

Léopards, ours et ongulés disparaissent

Dans le hameau perché de Arang Kel, à plus de 2.500 mètres d'altitude, les habitants disent ne pas avoir d'autre choix que d'abattre les prédateurs pour préserver leur bétail. "Nos moutons, chèvres et vaches sont vulnérables et parfois (les animaux sauvages) attaquent aussi les humains", explique à l'AFP Roshan Khan, un villageois sexagénaire. "C'est pour cela qu'ils sont abattus". "Ils sont contraints de s'approcher des zones habitées pour chercher de la nourriture et se font tuer par les gens lorsqu'ils attaquent le bétail", confirme Yousuf Qureshi, ancien directeur du service en charge de la faune dans le Cachemire pakistanais. Quelque 35 léopards et au moins cinq ours ont été tués de cette façon depuis 2007, opine Naeem Dar, qui travaille également à la direction de la faune et des pêcheries du Cachemire pakistanais. Plusieurs espèces ont complètement disparu du côté pakistanais de la ligne de démarcation, déplorent les responsables. C'est le cas du markhor, une espèce de chèvre sauvage dotée de longues et majestueuses cornes en forme de ruban. "La barrière fait obstacle et leur migration (depuis le Cachemire indien) a pris fin, déplore M. Qureshi. C'est une tragédie". Même chose pour le hangul, ou cerf du Cachemire, autrefois très présent et aujourd'hui "totalement disparu" du côté pakistanais, souligne-t-il.

Victimes collatérales

La barrière est non seulement électrifiée mais peut atteindre près de quatre mètres de haut en certains endroits. La zone est également parsemée de mines antipersonnel, de capteurs thermiques et de mouvements, de systèmes d'éclairage et d'alarme. L'Inde et le Pakistan, nés de la partition de l'Inde britannique en 1947 et tous deux en possession de l'arme nucléaire, n'ont jamais réussi à s'entendre sur la question du Cachemire, que chacun revendique dans son intégralité. Ils se sont livré deux guerres en son nom, et malgré l'actuelle ligne de démarcation tracée lors d'un cessez-le-feu en 2003, aucune solution au conflit n'est en vue. L'armée indienne se félicite de l'efficacité de la barrière contre les infiltrations de séparatistes depuis le Pakistan. Les entrées illégales ont été réduites "à quasiment rien", estime le lieutenant-général indien S K Dua, commandant du 15e corps d'armée, basé à Srinagar. Mais "la barrière sur la ligne de démarcation a perturbé l'habitat des animaux et limité leur territoire", déplore Muhammad Arshad, cadre d'une ONG locale, Himalaya Welfare Organization.

La barrière n'est pas la seule menace pesant sur la vie sauvage. Les tirs échangés occasionnellement entre les soldats des deux camps effraient les animaux. "Une fois qu'ils ont abandonné leur habitat, ils ne reviennent plus", souligne M. Qureshi. Cet habitat souffre aussi de la déforestation. Les hivers sont rudes dans la vallée de Neelum et les habitants n'ont d'autre choix que de se chauffer au bois. À l'époque de la création de l'Inde et du Pakistan en 1947, la forêt couvrait 24 % du sol du Cachemire pakistanais. Cette proportion est tombée aujourd'hui à 11 %. Pour les villageois, l'angoisse ne se limite pas aux attaques de prédateurs sur leur cheptel : ils disent craindre aussi la prison ou des amendes pour braconnage s'ils abattent les animaux sauvages. "Il faut trouver une solution", plaide le villageois Roshan Khan. La solution "pour protéger ces espèces", selon M. Quereshi ? "Il faut que l'Inde et le Pakistan fassent la paix dans la région et démantèlent la barrière". Autant dire que l'espoir est mince...

samedi 27 février 2016

Les requins

01:38:00 kais

Poignards, scies découpeuses de chairs... les dents des requins sont des armes redoutables ! Et il ne faut pas compter sur la mauvaise hygiène bucco-dentaire des squales, ni sur leur tendance à mordre dans des corps solides très durs, pour leur laisser des trous dans le sourire : leurs dents se renouvellent en permanence. Aucun risque donc pour leurs malheureuses proies de croiser un vieux requin édenté... De fait, ces prédateurs disposent d'une rangée de dents extérieure. Mais ils possèdent également d'autres rangées de dents, sur le rebord interne de leur mâchoire. Seule la rangée extérieure est fonctionnelle. Les autres viennent remplacer chaque dent tombée, un peu comme si elles étaient sur un tapis roulant. Chez les requins, nul besoin de rendez-vous chez le dentiste. De quoi rendre plus d'un humain jaloux ! Quel est le secret du renouvellement permanent de la dentition des requins ? Des chercheurs de l’université de Sheffield (Angleterre) ont découvert les mécanismes biologiques qui sous-tendent cette géniale mécanique. Peut-être une piste pour des traitements permettant de les "réveiller" chez l'homme.

Les gènes des dents perpétuelles

L'étude, publiée dans la revue scientifique Developmental Biology en février 2016, a permis d'identifier un réseau de gènes grâce auxquels les requins développent des dents tout au long de leur vie, ainsi que le rôle d'un certain type de cellules (des cellules épithéliales) situées dans leurs gencives dans l'effet "tapis roulant". Il s'agit de quatre gènes (Hh, Wnt / β-caténine, Bmp et FGF), qui existent chez les animaux depuis 450 millions d’années. Nous les possédons donc également. Seulement nos cellules épithéliales ne seraient activées que deux fois dans notre vie : au premier âge, lors de l'apparition des dents, et pendant l'enfance, lorsque les dents de lait sont remplacées par les dents définitives. Les chercheurs estiment donc envisageable de pouvoir "réactiver" ces cellules à des fins thérapeutiques. Reste à trouver comment modifier à l'envie l'expression de ces gènes.

vendredi 26 février 2016

Gorillas

01:57:00 kais

Gorillas sing and hum when eating, a discovery that could help shed light on how language evolved in early humans.

Singing seems to be a way for gorillas to express contentment with their meal, as well as for the head of the family to communicate to others that it is dinner time.

Food-related calls have been documented in many animals, including chimpanzees and bonobos, but aside from anecdotal reports from zoos, there was no evidence of it in gorillas.

To see if they make these noises in the wild,Eva Luef, a primatologist at the Max Planck Institute for Ornithology in Seewiesen, Germany, observed two groups of wild western lowland gorillas in the Republic of the Congo.

jeudi 25 février 2016

Javan tiger

02:21:00 kais

The Javan tiger was a big cat, but not in comparison to other tiger species. The males weighed in at 220 to 310 pounds and the females averaged 170 to 250 pounds. Their small size was thought to be attributed to the size of the available prey in their native land of Java, Indonesia. The theory is that the smaller the prey, the smaller the predator.

At one point, the Javan tigers inhabited all of Java. In the mid 1800s to mid 1900s the native people viewed these tigers as pests and chased them off to the remote mountainous areas. By 1972, the remaining tigers were sectioned off to the Meru Betiri National Park Reserve. Unfortunately, the protection of the reserve was not enough.

Due to hunting, loss of forest habitat and lack of prey, the number of Javan tigers dwindled. The last members were spotted in the reserve in 1976 and the Javan tigers were officially declared extinct in 2003, joining the ever growing list of recently extinct species

mardi 23 février 2016

Huge space

21:11:00 kais

new study suggests that there are around 700 quintillion planets in the universe, but only one like Earth. It’s a revelation that’s both beautiful and terrifying at the same time.
Astrophysicist Erik Zackrisson from Uppsala University in Sweden arrived at this staggering figure — a 7 followed by 20 zeros — with the aid of a computer model that simulated the universe’s evolution following the Big Bang. Zackrisson’s model combined information about known exoplanets with our understanding of the early universe and the laws of physics to recreate the past 13.8 billion years.
Zackrisson found that Earth appears to have been dealt a fairly lucky hand. In a galaxy like the Milky Way, for example, most of the planets Zackrisson’s model generated looked very different than Earth — they were larger, older and very unlikely to support life. The study can be found on the preprint server arXiv, and has been submitted to The Astrophysical Journal.

Rethinking Copernicus

Zackrisson’s work suggests an alternative to the commonly held assumption that planets similar to Earth must exist, based on the sheer number of planets out there. Ever since Copernicus put forth the theory that Earth is not the center of the universe, scientists have expanded the map of the cosmos and diminished our planet’s relative uniqueness. Current estimates hold that there are some 100 billion galaxies in the universe containing about 10^18 stars, or a billion trillion.

One of the most fundamental requirements for a planet to sustain life is to orbit in the “habitable zone” of a star — the “Goldilocks” region where the temperature is just right and liquid water can exist. Astronomers have, to this point, discovered around 30 exoplanets in the habitable zones of stars. Simply extrapolating that figure based on the known number of stars suggests that there should be about 50 billion such planets in the Milky Way alone. Probability seems to dictate that Earth-twins are out there somewhere.

But according to Zackrisson, most planets in the universe shouldn’t look like Earth. His model indicates that Earth’s existence presents a mild statistical anomaly in the multiplicity of planets. Most of the worlds predicted by his model exist in galaxies larger than the Milky Way and orbit stars with different compositions — an important factor in determining a planet’s characteristics. His research indicates that, from a purely statistical standpoint, Earth perhaps shouldn’t exist.

Killer Whale ORCA

09:19:00 kais

With sleek black backs and bright white bellies and eye patches, killer whales, or orcas, are easily distinguishable from other aquatic animals.

One of the ocean’s largest predators, male orcas can grow to 9.5 m (32 ft) in length, while females are slightly smaller at 8 m (23 ft). They live primarily where the water is cold but can live anywhere from the polar regions right up to the equator. This massive range makes orcas the most widespread of all sea creatures.

True to their name, killer whales are effective hunters. They prey on seals, sea lions, fish, sea birds, turtles, octopuses, and squid. Orcas will even attack other whales, including the enormous blue whale which can measure over three times their size. They have also been known to breach the surface to grab sea lions and seals, even partially jumping onto ice floes to reach their target.

Killer whales hunt in pods, or groups, in a way similar to wolves. They circle their prey and force them into smaller areas before attacking. Once cornered, the orcas take turns biting and ramming their prey.

Sending sound waves that travel underwater, killer whales use echolocation as a means for hunting. The reverberating sound provides information about an object’s location, size, and shape. Echolocation is also used as a form of communication. Each pod has a distinctive sound it uses to communicate among its members.

There are thought to be three types of pods: transient, resident, and offshore. Transient pods are constantly on the move following food sources. Resident pods generally stay in one area close to shore, while offshore orcas prefer the open waters. Currently, scientists are not clear as to why there are contrasting pod behaviors. Some believe it is because there are actually several species of orca, but more research must be conducted in order to test that theory.

TURTLE

00:17:00 kais

Turtles are basically reptiles. They are characterized by a shell that develops from their ribs and serve as a protective cover. The earliest known turtles date back to around 215 million years and are therefore considered to be the oldest members of the reptile family. The largest of turtles are aquatic though they do not lay eggs under water. They do breath under water though. When threatened these beautiful creatures can envelop inside their shells however, if rolled over they are very vulnerable.

lundi 22 février 2016

A virus is taming Australia’s bunny menace, and giving endangered species new life

12:09:00 kais

For more than 150 years, Australia has been plagued by rabbits. First introduced by an English settler as hunting fodder in 1859, the European rabbit population soon ballooned to an estimated 10 billion, contributing to extensive environmental damage and the extinction of some native species. Over the past century, biologists tried—and largely failed—to stem the tide with fences, poisons, and pathogens.

Now, an accidental approach seems to be taming the invasion. Since scientists unintentionally released a deadly rabbit virus in 1995, it has wrought havoc on the bunnies—and allowed some endangered native mammals to recover, according to a new study in the journal Conservation Biology.

Ironically, Australia’s viral progress began with a mortifying error. Government researchers were experimenting with the rabbit haemorrhagic disease virus (RHDV) on Wardang Island, off South Australia’s coast, when renegade flies picked up the pathogen and transported it to the mainland. Luckily, the containment failure became a smashing success: The virus eradicated an estimated 60% of Australia’s rabbits, acting with particular lethality in arid areas. The government officially released the disease in 1996.

As RHDV spread, researchers documented encouraging ecosystem changes. Native vegetation bounced back, and populations of large herbivores such as kangaroos increased.

Still, no one was quite certain how RHDV’s advance was affecting some groups of animals, including Australia’s small desert mammals. Several rodents, such as the dusky hopping mouse and the plains mouse, had nearly vanished during the rabbit takeover. So had the crest-tailed mulgara, a hamster-sized marsupial that preys on lizards and insects. Both the dusky hopping mouse and the plains mouse are considered vulnerable by the International Union for the Conservation of Nature (IUCN), and the mulgara is listed as endangered in South Australia.

Recently, however, scientists have noticed hints of a startling comeback. Driving through the desert at night, for instance, biologists now “see dusky hopping mice in your headlights everywhere,” says Reece Pedler, an ecologist at the South Australian Department of Environment, Water and Natural Resources. “It’s become pretty clear that something major has changed.”

To get a clearer picture, Pedler and colleagues pulled together 45 years of mammal trapping surveys conducted by the state government, mining companies, and nongovernmental groups. When they compared records from before and after RHDV’s arrival, they found that small mammal populations had skyrocketed in the years following the introduction of the rabbit virus. The crest-tailed mulgara increased its “extent of occurrence”—the area in which a species has been sighted—nearly 70-fold. The dusky hopping mouse and the plains mouse more than tripled and doubled their occurrence, respectively.

The surveys suggested that RHDV deserved credit for the resurgences. South Australia’s small mammal populations tend to boom after heavy rainfalls, but Pedler notes that the biggest recoveries happened in dry years. Correlation may not equal causation, but, Pedler says, “everything is pointing toward the reduction in rabbits” as the cause of the rebound.

The findings fit with what other biologists are seeing. According to Brian Cooke, an ecologist at the University of Canberra who was not involved with the new study, “there have been remarkable changes in arid zone vegetation since RHDV was released 20 years ago.” Cooke’s own research has documented ecological benefits in a different suite of species: When he removed rabbits from experimental plots, he observed recovery in kangaroos and wombats. “With data for small mammals pointing in the same direction, it is making an even stronger case” for the benefits of RHDV, Cooke says.

Why would a bunny bust lead to a native mammal boom? Pedler offers two explanations. First, the end of rabbit overgrazing allowed native vegetation to grow back, providing food and shelter for mice and mulgaras. But that’s not all. When Pedler and his team poured over the trapping records, they observed precipitous declines in rabbit predators such as feral cats and foxes. The virus had likely rippled through the food web, starving these invasive predators, which had been devouring native species along with rabbits—a chain reaction called a trophic cascade.

Australia annually spends millions of dollars removing cats and foxes, which are responsible for most of the country’s mammal extinctions. According to Pedler, however, further viral introductions offer an efficient ecological alternative to traps and poisons. “Cats and foxes could be controlled much more cheaply, at a much larger scale, by removing their rabbit prey,” Pedler says.

Thanks to RHDV, the small mammals now recovering from the rabbit menace may qualify for downgrading on IUCN’s “red list.” And viral control could soon become even more effective. Later this year, Australia plans to unleash a new strain of RHDV, which is expected to work better in moist climes. “Rabbits are so ubiquitous they are just regarded as part of the background by many people,” says Cooke—but perhaps not for long.

dimanche 21 février 2016

Some Of The Strangest Exoplanets In Space

23:20:00 kais

The silica particles swept along by HD 189773b’s harsh winds may form glass, and could even be responsible for the planet’s azure color. TrES-2b, on the other hand, appears blacker than both coal and black acrylic paint.

Scientists aren’t entirely sure why the planet reflects less than 1% of the light that hits it, but theorize that chemicals in its atmosphere might absorb the light.

Africanized Honey

15:02:00 kais

An experiment gone wrong, in 1957 a Brazilian bee keeper who was trying to interbreed European and African honey bees accidently let some of his “pets” get away. Much more aggressive than their European counterparts, these genetically mixed “killer bees” have since then spread through out the Americas. They have come to be feared in some regions because of their tendency to swarm relentlessly and aggressively chase their victims for miles.

Deaths talker scorpio

14:56:00 kais

This highly venomous scorpion residing primarily in North Africa and the Middle East is responsible for over 75% of scorpion related deaths every year. Although healthy adults usually only feel unbearable pain, children that are envenomated suffer fever, coma, convulsions, and paralysis before their lungs fill up and they drown in their own fluids.

vendredi 19 février 2016

L'hippocampes

15:54:00 kais

Chez les hippocampes, c'est le mâle qui garde les œufs dans son ventre, subit les contractions et accouche.

Dans le monde animal, la palme du "superpapa" pourrait bien revenir à l'hippocampe : chez ce poisson, c'est en effet le mâle qui porte les œufs dans son ventre et qui met bas. L'équipe du film Les superpapas de la nature, diffusé sur France 2 dimanche 21 février 2016 à 16h25, a capturé ce moment extraordinaire d'accouchement paternel" chez l'une des deux espèces d'hippocampe de l'Hexagone,Hippocampus hippocampus.

"On rencontre ces hippocampes marron à pointes blanches près de Toulon. Mais l'accouchement est impossible à filmer dans la nature : les bébés font 3 millimètres le long et avec le courant marin et la turbidité de l'eau, on ne voit rien", explique Pascal Cardeilhac, réalisateur du documentaire. L'équipe de tournage s'est donc installée dans la nurserie del'Institut océanographique Paul Ricard, qui élève ces poissons en voie de disparition, puis les relâche dans la nature. "Nous avons installé un lit de camp près de l'aquarium pour ne rien louper de l'accouchement, se souvient avec amusement le réalisateur. Le père a des contractions, puis il expulse une dizaine de petits. Mais c'est près de cent œufs qui ont éclos dans sa poche ventrale. En tout, l'accouchement peut durer 4 à 5 heures". Au début du cycle de reproduction, la femelle transfère ses œufs dans la poche ventrale du mâle, qui les féconde. Là, ils se développent et éclosent au bout de trois semaines. Le père n'a alors "plus qu'à" expulser les petits, qui sont autonomes dès leur naissance. Mais quel intérêt pour l'hippocampe d'avoir un mâle accoucheur ? "Le rôle du père est d'accélérer le rythme de reproduction : la femelle peut refaire des œufs pendant les trois semaines où c'est le mâle qui porte les œufs", avance Pascal Cardeilhac. Les hippocampes ont donc développé une stratégie de la quantité pour palier le fort taux de mortalité de leurs descendants. Pour autant, les parents ont une certaine notion du couple : "en aquarium, la mère reconnaît à quel mâle elle a confié ses œufs. Plus surprenant, elle vient parfois toucher le ventre du père entre deux expulsions, comme un geste de soutien".

jeudi 18 février 2016

Dangerous fish: Puffer

14:25:00 kais

The puffer, which is also called swellfish, or blowfish, is any member of a group of about 90 species of fishes of the family Tetraodontidae, noted for their ability when disturbed to inflate themselves so greatly with air and water that they become globular in form. Puffers are found in warm and temperate regions around the world, primarily in the sea but also, in

some instances, in brackish or fresh water. They have tough, usually prickly skins and fused teeth that form a beaklike structure with a split in the center of each jaw. The largest puffers grow about 90 cm (3 feet) long but most are considerably smaller.

Many species are poisonous; a highly toxic substance, tetraodontoxin, is especially concentrated in the internal organs. Although this substance can cause death, puffers are sometimes used as food. In Japan, where the fishes are called fugu, they must be carefully cleaned and prepared by a specially trained chef.

mercredi 17 février 2016

Star Wars

15:08:00 kais

If converted to the iconic Star Wars' opening crawl, this headline would read, "Just a few days ago, they discovered hundreds of galaxies kinda not that far away..." That's because researchers from four countries converged in Australia and used a radio telescope to detect a total of 883 relatively near galaxies heretofore blocked from view by something called the Zone of Avoidance. Their findings, published in the Astronomical Journal, could shed some light on a cosmic force dubbed the Great Attractor...and the nature of our universe.

mardi 16 février 2016

Danger Belgique

16:13:00 kais

La Belgique vient de redémarrer deux vieilles centrales, malgré les découverte l’an dernier de 16 000 fissures sur deux des réacteurs, et une explosion survenue récemment dans un autre. Ils risquent de provoquer un nouveau Tchernobyl, en plein cœur de l’Europe.

La semaine dernière, près de 900 000 membres européens d’Avaaz ont remporté une campagne exigeant des inspections internationales, et fait en sorte que les médias s’emparent de cette inquiétante affaire. Si nous sommes assez nombreux à nous rallier à cet appel aujourd’hui, nous pouvons mobiliser l’agence de l’ONU pour l’environnement, puis faire fermer les centrales, tant qu’une évaluation exhaustive des risques n’est pas conduite.

La Belgique met les bouchées doubles pour résoudre cette crise. Si aujourd’hui, nous faisons entendre le plus grand appel jamais lancé en faveur de la sûreté énergétique, nous pouvons créer un précédent en Europe et faire le premier pas vers la fermeture de dizaines de centrales dangereuses de part le monde.

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