Sockeye salmon 'sense magnetic field of home'

Salmon use the Earth's magnetic field to navigate across the ocean as they return to their home rivers to breed, research suggests.

Each year millions of fish make the journey home in one of the toughest migrations of the animal kingdom.

The memory of the magnetic field where they first entered the sea helps them find their way back, say US scientists,according to BBC.

The data, in Current Biology, provide the first direct evidence that salmon use geomagnetic cues in migration.

Other marine animals, including turtles and seals, may also use the same homing mechanism, say researchers.

The journey of adult sockeye salmon from the northern Pacific Ocean back to the individual freshwater rivers of their birth is one of the toughest migrations of all animals.

There are several theories for how salmon locate their nurseries after spending years out at sea.

One hypothesis, known as natal homing, is that salmon use both chemical and geomagnetic cues to find their way home.

In order to test the theory, researchers studied fisheries data spanning 56 years charting the return of salmon to the Fraser River in British Columbia.

The route the fish chose to swim around Vancouver Island matched the intensity of the geomagnetic field near their home rivers.

 Sockeye salmon live in the northern Pacific Ocean, but breed in freshwater

  After spending several years in the ocean reaching sexual maturity, they return to the freshwater rivers in which they were born during the summer months

 During spawning, each female lays 2,000 eggs, before both the males and females die

 Young salmon mature in the freshwater nurseries, and at two years of age they depart for the open ocean

Nathan Putman, a researcher at Oregon State University, told BBC News: "For salmon to find their way back home, they remember the magnetic field that exists where they first enter the sea as juveniles, and once they reach maturity, they seek that same coastal location, with the same magnetic field.

 "In other words, salmon remember the magnetic field where they enter the ocean and come back to that same spot once they reach maturity."

Sea turtles, elephant seals and many other fish, including eels, tuna and sturgeon, have a similar migratory strategy, he added.

James J Anderson and Chloe Bracis of the University of Washington say the work supports recent modelling studies showing geomagnetic imprinting is feasible to return salmon to their home river. It also complements laboratory findings that trout olfactory systems can detect geomagnetic fields.

M.Wassouf

Vegetation Changes in Cradle of Humanity: Study Raises Questions About Impact On Human Evolution

The bipedal human ancestor or the grassland encroaching on the forest? A new analysis of the past 12 million years' of vegetation change in the cradle of humanity is challenging long-held beliefs about the world in which our ancestors took shape -- and, by extension, the impact it had on them.

The research combines sediment core studies of the waxy molecules from plant leaves with pollen analysis, yielding data of unprecedented scope and detail on what types of vegetation dominated the landscape surrounding the African Rift Valley (including present-day Kenya, Somalia and Ethiopia), where early hominin fossils trace the history of human evolution,according to Science Daily.

"It is the combination of evidence both molecular and pollen evidence that allows us to say just how long we've seen Serengeti-type open grasslands," said Sarah J. Feakins, assistant professor of Earth sciences at the USC Dornsife College of Letters, Arts and Sciences and lead author of the study, which was published online in Geology on Jan. 17.

Feakins worked with USC graduate student Hannah M. Liddy, USC undergraduate student AlexaSieracki, Naomi E. Levin of Johns Hopkins University, Timothy I. Eglinton of the EidgenössischeTechnischeHochschule and RaymondeBonnefille of the Universitéd'Aix-Marseille.

The role that the environment played in the evolution of hominines -- the tribe of human and ape ancestors whose family tree split from the ancestors of chimpanzees and bonobos about 6 million years ago -- has been the subject of a century-long debate.

Among other things, one theory dating back to 1925 posits that early human ancestors developed bipedalism as a response to savannas encroaching on shrinking forests in northeast Africa. With fewer trees to swing from, human ancestors began walking to get around.

While the shift to bipedalism appears to have occurred somewhere between 6 and 4 million years ago, Feakins' study finds that thick rainforests had already disappeared by that point -- replaced by grasslands and seasonally dry forests some time before 12 million years ago.

In addition, the tropical C4-type grasses and shrubs of the modern African savannah began to dominate the landscape earlier than thought, replacing C3-type grasses that were better suited to a wetter environment. (The classification of C4 versus C3 refers to the manner of photosynthesis each type of plant utilizes). While earlier studies on vegetation change through this period relied on the analysis of individual sites throughout the Rift Valley -- offering narrow snapshots -- Feakins took a look at the whole picture by using a sediment core taken in the Gulf of Aden, where winds funnel and deposit sediment from the entire region. She then cross-referenced her findings with Levin who compiled data from ancient soil samples collected throughout eastern Africa.

"The combination of marine and terrestrial data enable us to link the environmental record at specific fossil sites to regional ecological and climate change," Levin said.

R.S

Discovery in Synthetic Biology Takes Us a Step Closer to New 'Industrial Revolution'

Scientists report that they have developed a method that cuts down the time it takes to make new 'parts' for microscopic biological factories from 2 days to only 6 hours.

The scientists, from Imperial College London, say their research brings them another step closer to a new kind of industrial revolution, where parts for these biological factories could be mass-produced. These factories have a wealth of applications including better drug delivery treatments for patients, enhancements in the way that minerals are mined from deep underground and advances in the production of befouls, according to Science Daily.

Professor Paul Freemont, Co- Director of the Centre for Synthetic Biology and Innovation at Imperial College London and principle co-investigator of the study, which is published February 1 in the journal Nucleic Acids Research, says: "Before the industrial revolution most items were made by hand, which meant that they were slower to manufacture, more expensive to produce and limited in number. We are at a similar juncture in synthetic biology, having to test and build each part from scratch, which is a long and slow process. We demonstrate in our study a new method that could help to rapidly scale up the production and testing of biological parts."

Parts made up of DNA are re-engineered by scientists and put into cells to make biological factories. However, a major bottleneck in synthetic biology is the lack of parts from which to build new types of factories. To build parts using the current time-consuming method, scientists have to re-engineer DNA in a cell and observe how it works. If it functions according to their specifications, then the scientists store the part specifications in a catalogue.

Now, scientists from Imperial College London have devised a much quicker method that does away with the need for them to re-engineer a cell every time they want to make a new part. The team say their work could lead to vast new libraries of off-the-shelf components that could be used to build more sophisticated biological factories.

James Chappell, co-author of the study from the Centre for Synthetic Biology and Innovation at Imperial College London, says: "One of the major goals in synthetic biology is to find a way to industrialise our processes so that we can mass produce these biological factories much in the same way that industries such as car manufacturers mass produce vehicles in a factory line. This could unlock the potential of this field of science and enable us to develop much more sophisticated devices that could be used to improve many facets of society. Excitingly, our research takes us one step closer to this reality, providing a rapid way of developing new parts."

In the study, the Imperial researchers demonstrate for the first time that the same method can be achieved in a test tube outside of a cell. This involves extracting from cells the machinery that produces mRNA and proteins and providing the energy and building blocks to help them survive in test tubes. The team then add their re-programmed DNA to the solution and observe how it functions.

The advantage of this method is that scientists can develop litres of this cell-like environment so that multiple re-programmed DNA can be tested simultaneously, which speeds up the production process of parts.

The next stage of the research is to expand the types of parts and devices that can be developed using this method. They also are aiming to develop a method using robots to speed up and make the whole process automated.

Professor Richard Kitney, co- Director of the Centre for Synthetic Biology and Innovation at Imperial College London says: "Synthetic biology is seen by the British Government as having the potential to create new industries and jobs for the benefit of the UK economy. This work is part of a wider, major research programme within the Centre to develop technology that can be used across a range of industrial applications."

M.Wassouf

Aztec Conquest Altered Genetics Among Early Mexico Inhabitants, New DNA Study Shows

For centuries, the fate of the original Otomí inhabitants of Xaltocan, the capital of a pre-Aztec Mexican city-state, has remained unknown. Researchers have long wondered whether they assimilated with the Aztecs or abandoned the town altogether.

According to new anthropological research from The University of Texas at Austin, Wichita State University and Washington State University, the answers may lie in DNA. Following this line of evidence, the researchers theorize that some original Otomies, possibly elite rulers, may have fled the town. Their exodus may have led to the reorganization of the original residents within Xaltocan, or to the influx of new residents, who may have intermarried with the Otomí  population, according to Science Daily.

Using ancient DNA (aDNA) sampling, Jaime Mata-Míguez, an anthropology graduate student and lead author of the study, tracked the biological comings and goings of the Otomí people following the incorporation of Xaltocan into the Aztec empire. The study, published in American Journal of Physical Anthropology, is the first to provide genetic evidence for the anthropological cold case.

Learning more about changes in the size, composition, and structure of past populations helps anthropologists understand the impact of historical events, including imperial conquest, colonization, and migration, Mata-Míguez says. The case of Xaltocan is extremely valuable because it provides insight into the effects of Aztec imperialism on Mesoamerican populations.

Historical documents suggest that residents fled Xaltocan in 1395 AD, and that the Aztec ruler sent taxpayers to resettle the site in 1435 AD. Yet archaeological evidence indicates some degree of population stability across the imperial transition, deepening the mystery. Recently unearthed human remains from before and after the Aztec conquest at Xaltocan provide the rare opportunity to examine this genetic transition.

As part of the study, Mata-Míguez and his colleagues sampled mitochondrial aDNA from 25 bodies recovered from patios outside excavated houses in Xaltocan. They found that the pre-conquest maternal aDNA did not match those of the post-conquest era. These results are consistent with the idea that the Aztec conquest of Xaltocan had a significant genetic impact on the town.

Mata-Míguez suggests that long-distance trade, population movement and the reorganization of many conquered populations caused by Aztec imperialism could have caused similar genetic shifts in other regions of Mexico as well.

In focusing on mitochondrial DNA, this study only traced the history of maternal genetic lines at Xaltocan. Future aDNA analyses will be needed to clarify the extent and underlying causes of the genetic shift, but this study suggests that Aztec imperialism may have significantly altered at least some Xaltocan households.

R.Sawas

Cats killing billions of animals in the US

Cats are one of the top threats to US wildlife, killing billions of animals each year, a study suggests.

The authors estimate they are responsible for the deaths of between 1.4 and 3.7 billion birds and 6.9-20.7 billion mammals annually.

Writing in Nature Communications, the scientists said stray and feral cats were the worst offenders.

However, they added that pet cats also played a role and that owners should do more to reduce their impact.

The authors concluded that more animals are dying at the claws of cats in the United States than in road accidents, collisions with buildings or poisonings.

The domestic cat's killer instinct of has been well documented on many islands around the world.

Felines accompanying their human companions have gone on to decimate local wildlife, and they have been blamed for the global extinction of 33 species.

But their impact on mainland areas has been harder to chart.

To find out more, researchers from the Smithsonian Conservation Biology Institute (SCBI) and the US Fish and Wildlife Service carried out a review of studies that had previously looked at the predatory prowess of cats.

Their analysis revealed that the cat killings were much higher than previous studies had suggested: they found that they had killed more than four times as many birds as has been previously estimated.

Birds native to the US, such as the American Robin, were most at risk, and mice, shrews, voles, squirrels and rabbits were the mammals most likely to be killed.

Dr Pete Marra from the SCBI said: "Our study suggests that they are the top threat to US wildlife."

The team said that "un-owned" cats, which they classified as strays, feral cats and farm cats, were killing about three times as many animals as pet cats, but that their owners could do more to limit the impact.

Dr Marra said: "We hope that the large amount of wildlife mortality indicated by our research convinces some cat owners to keep their cats indoors and that it alerts policymakers, wildlife managers and scientists to the large magnitude of wildlife mortality caused by cat predation."

A spokeswoman for the UK's animal welfare charity the RSPCA said that a properly fitted collar and bell could reduce a cat's success when hunting by at least a third.

R.S