The Global Fool

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Wasting Syndrome and Starfish Die-Off
Feb09

Wasting Syndrome and Starfish Die-Off

By Roberta Attanasio Up and down the U.S. and Canada Pacific coastlines, starfish are disappearing, dying by the millions of a mysterious disease that makes them “turn into goo.” The disease — starfish wasting syndrome — initially causes white lesions that lead to death of body tissue. Eventually, the arms twist and tear off — and they do not regenerate (healthy starfish may shed their arms, but then new ones are formed in a relatively short time). At the end, the entire body of the wasting starfish disintegrates. The wasting syndrome affects about a dozen starfish species, but has been noticed mostly in sunflower starfish (Pycnopodia helianthoides) and ochre stars (Pisaster ochraceus). Starfish die-offs have been observed along the California coast in 1983 and 1997 — however, this year, the die-off is occurring at an unprecedented rate. No cause has been identified, but speculations abound. Claims that Fukushima radiation could be implicated in the die-off have been disproved by Chris Mah (a researcher at the Smithsonian National Museum of Natural History and one of the world’s leading experts on starfish), on the basis of three major considerations — the syndrome pre-dates Fukushima by 3 to 15 years, it occurs on both East and West coasts, and it does not seem to affect any other marine life in these regions. Gary Wessel, a professor at Brown University, told NBC News that a combination of stressors, both pathogenic (a new bacterium or virus) and environmental (a change in ocean temperature) may be responsible for the syndrome. He also thinks that the disease is unlikely to affect humans or other larger marine life. An accepted explanation is that an infectious microbe (a virus, bacterium, fungus or other) could impair the starfish immune system, making them susceptible to secondary bacterial infections that ultimately cause wasting. Back in November, Pete Raimondi, a professor at the University of California, Santa Cruz, told the Los Angeles Times “Imagine a wound on your finger that you never treated. The bacteria would continue to build up and just eat away the flesh until it fell off. That’s how this disease goes.” Global warming is an important factor in the occurrence of disease outbreaks of infectious microbes that affect marine life. Increasing temperatures favor the growth of these microbes and allow their spread across an extended geographical range. In addition, increasing temperatures induce heat stress, which adversely affects the defense/immune mechanisms. Indeed, the spread and progression of the wasting syndrome — in starfish and other species — are temperature-sensitive and increase at warmer temperatures. The starfish is a voracious predator and a keystone species — a species that plays a critical role in maintaining the structure of an ecological community. Starfish eat snails, sea urchins,...

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A Toxoplasma’s Journey: From Cats to Sea Otters
Jan19

A Toxoplasma’s Journey: From Cats to Sea Otters

By Roberta Attanasio Toxoplasma gondii is a single-celled parasite that infects most warm blooded animals. In 2012, it landed in the news because of its ability to hijack the arousal circuitry of rats — the parasite activates a part of the brain normally engaged in sexual attraction. Rats infected with it are not afraid to approach cats and behave as they would in the presence of a sexually receptive female rat. What happens next? The cat easily catches and eats the infected rat and, in doing so, also catches the parasite — the parasite is happy as it reproduces sexually only in cats. The parasite’s oocysts — sometimes called “eggs” — are later dispersed in the cat’s droppings and, from there, get to infect other animals, including humans. In the news or not, Toxoplasma gondii — T. gondii or Toxo for short — has been popular for a long time. Indeed, one-third of people around the world have been infected with it. According to the Centers for Disease Control and Prevention, more than 60 million men, women, and children in the U.S. carry T. gondii. Most people do not show any symptoms. However, the parasite causes significant damage to the unborn child if a woman becomes infected for the first time during pregnancy. It also causes severe disease in people with a compromised immune system. Now, let’s add a few more elements to the cat-becomes-infected-and-infects-people story. Cats become infected by eating animals that harbor the parasite in their tissues, for example infected mice, rats and birds. Then, infected cats shed large numbers (hundreds of millions) of parasite oocysts in their feces for one or two weeks. Once in the environment, the oocysts infect not only animals such as mice, rats and birds, but also farm animals such as cows, sheep, pigs, and chickens. People may become infected by eating undercooked meat or unwashed vegetables or, as we’ll see later in this post, uncooked or undercooked seafood. In addition, people may become infected through other routes. T. gondii also infects marine mammals and causes significant mortality in southern sea otters (Enhydra lutris nereis), an endangered species. How does T. gondii end up in sea otters? Researchers at the University of California, Santa Cruz and at the University of California, Davis, designed an elegant study to answer this question. The study — A New Pathogen Transmission Mechanism in the Ocean: The Case of Sea Otter Exposure to the Land-Parasite Toxoplasma gondii — was published last month (December 18, 2013) in the open-access, peer-reviewed scientific journal PLOSone. Southern sea otters live in giant kelp forests along the California coast. Kelp forests — one of the most productive ecosystems in the world — are composed of dense strands formed by kelp (large brownish seaweeds...

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Sustainability in Action: Christmas Trees Provide Habitat for Coho Salmon
Dec29

Sustainability in Action: Christmas Trees Provide Habitat for Coho Salmon

By Roberta Attanasio There are many remarkable features of salmon, and one of these is their ability to travel thousands of miles in the ocean, struggle with river currents and waterfalls, and finally reach their hatching place. Indeed, salmon live in the ocean, but are born and spawn in freshwater rivers and streams. The young salmon spend at least some of their early lives in freshwater, before swimming to the sea — where they grow and mature. With a few exceptions, Pacific salmon spawn only once and die within days of digging their nests in the gravel and mating.   Coho salmon — one of seven species of Pacific salmon — is famous for its acrobatic leaps out of the water and can be found in most waters that drain into the north Pacific Ocean, from Japan and Siberia to Alaska and California. Now, it’s even at home in the Great Lakes, as it can adapt to live entirely in fresh water. Coho fry —  juveniles that have absorbed their egg sac — live in rivers and streams for over a year, feeding on zooplankton, insects and small fish, and they’re happy to see Christmas trees around them. Indeed, fish utilize underwater trees as cover from predators as well as for foraging and spawning — programs that recycle Christmas trees as aquatic habitat for fish are becoming more popular across the country. One of these programs — “Christmas for Coho” —  is organized and implemented by the Tualatin Valley chapter of Trout Unlimited, a conservation group whose members are Northwest Oregon residents. The program is already in its third year. Volunteers collect used Christmas trees and transport them to the Northwest Oregon coast — trees are then placed into an off channel wetland near Seaside to provide appropriate habitat for Coho salmon. Mike Gentry, one of the group members involved in the Christmas for Coho project, told the Portland Tribune that underwater photos show fish congregating under the trees even before volunteers finish their work in the river. According to NOAA’s National Marine Fisheries Service, salmon species have been declining dramatically on the West coast of the United States during the past several decades. Various human-induced and natural factors are responsible for this decline. Currently, a variety of conservation initiatives are underway, for example captive-rearing in hatcheries and removal and modification of dams that obstruct salmon migration. Other important conservation initiatives involve the restoration of degraded habitat — the Christmas for Coho project is one of these initiatives. Christmas trees replace the woody debris that are now sparsely present in backwaters and wetlands because of modifications of the natural...

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The Great Global Die-Off: Frogs and Lymphocytes
Oct28

The Great Global Die-Off: Frogs and Lymphocytes

By Roberta Attanasio Frogs and other amphibians – salamanders and caecilians – have been declining worldwide during the past few decades at an alarming rate. According to a June 2012 assessment by the International Union for the Conservation of Nature and Natural Resources (IUCN), about 41 percent of amphibian species are at risk of extinction, and some are already extinct. Like many other inhabitants of our planet, amphibians have been hit hard by climate change and habitat loss – and not only. Amphibians have also been decimated by the spread of chytridiomycosis, which is defined by the IUCN as the single most devastating infectious disease of vertebrate animals. In a historical article published in 2008, David Wake and Vance Vredenburg state: “A general message from amphibians is that we may have little time to stave off a potential mass extinction.”   The deadly chytridiomycosis is caused by Batrachochytrium dendrobatidis (Bd), a fungus found on all continents except Antarctica. According to epidemiological evidence described in an article published in 2004, the Bd fungus was present in African clawed frogs (Xenopus laevis) in their native South Africa as early as the mid-1930s. African clawed frogs infected with Bd do not show any clinical sign of disease and can carry the fungus for long periods of time without dying. Therefore, these frogs are Bd carriers and transmit the fungus to vulnerable species. Worldwide dissemination of Bd started in the 1930s because of the international trade of African clawed frogs. From the 1930s to 1950s, large numbers of these frogs were caught in the wild in southern Africa and exported across the world, mostly for use in the first human pregnancy tests and scientific research. Results from a study recently published in the journal PLOSone confirm that Bd was present as a stable, endemic infection in Xenopus populations in Africa prior to their worldwide distribution, which likely occurred via international live-amphibian trade. Vance Vredenburg, lead author of the study, said: “Today, these frog populations are often found in or near urban areas, probably because hospitals released them into the wild when new pregnancy testing methods were invented in the 1960s.” Bd proliferates in skin cells and rapidly kills amphibians by disrupting skin function – it impairs the skin’s ability to absorb electrolytes. A few years ago, a group of scientists from Australia found that, in diseased frogs, the skin’s ability to take up sodium and potassium ions from the water decreases by more than 50 percent, leading to a sharp decline of these ions in the blood and eventually causing cardiac arrest and death. Despite these recent discoveries, there was an unanswered question: “Why is the amphibian immune system so inept at clearing the fungus?” Now, a team of investigators from Vanderbilt University reports, in an article published in the journal Science and entitled...

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Global Reforestation: How Likely Is It?
Oct15

Global Reforestation: How Likely Is It?

By The Editors Forests are plant communities dominated by trees and, because of their nature, rely on dynamic associations of living organisms that undergo constant change – deforestation may be easily followed by reforestation, either natural or man-driven. How likely is it that global reforestation will occur? According to a recently published study entitled “Outlook on a worldwide forest transition“, it is not likely. Results of the study indicate that — unless we substantially boost agricultural production or we consume less food — the forest cover of the planet will continue to decline over the next two centuries until it stabilizes at 22% of global land cover and 1.4% of wild pasture. In other words,  just 22% of the land surface of the planet will remain forested. Our planet is experiencing a serious global decline in forests. Indeed, over 70 million hectares of forest have been lost during the last two decades — an area greater than France, or about 0.5% of global land area — mostly because of the expansion of agricultural land needed to feed a growing population. The long-term challenge is feeding the human population while still conserving the natural habitat and reversing global deforestation. To predict future global forest trends, the authors of the study (Chris Pagnutti, Chris T. Bauch, and Madhur Anand) used data on the global use of land encompassing hundreds of years – data provided by the United Nations Food and Agriculture Organization (FAO) and other sources. They incorporated the data into a mathematical model designed to capture how transitions in land use, including deforestation and reforestation, are driven by three key factors: agricultural yield, per capita food consumption, and world population change over time. The historical trends show that food consumption is rising faster than agricultural productivity. Thus, as mentioned above, the global forest cover is predicted to further decline. Unless new technological advances lead to increasing agricultural yields, or strategies to decrease food consumption are introduced over the next century, a switch to global reforestation remains unlikely. Under an alternative scenario, in which food production and consumption stabilize, reforestation could increase the global forest cover to about 35% — if stabilization occurs within the next 70 years. The researchers suggest that equal effort should be directed towards finding ways to boost agricultural yield, disseminate those technologies to developing countries, and decrease per capita consumption. Anand, one of the investigators, elaborates, “What is new here is the provision of a set of quantitative guidelines (the mathematical model outputs) that demonstrate exactly how much improvements to agricultural yield or decreases in consumption will affect forest cover dynamics in time.” Whether or not it will be possible to reverse the decline in forests...

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