Animals thrive without oxygen

We can’t survive for very long without oxygen. Researchers thought the same was true for every other animal, until an Italian and Danish team found tiny animals thriving in oxygen-free sediments deep below the Mediterranean Sea.

A Loricifera called Spinoloricus: tougher than it looks! Image: Danovaro et al (2010)/BMC Biology

The tiny animals are known as Loricifera, and they grow to just one millimetre long. They were found living in anoxic (or oxygen-free) sediment on the Mediterranean seafloor, in conditions that would kill other animals fairly quickly.

Anoxic basins in the Mediterranean seabed are some of the most extreme environments on Earth. Over 3000 metres below the waves, a thick layer of salty brine collects in shallow basins, preventing oxygen dissolved in the seawater from reaching the sediment. The sediment is also packed with poisonous hydrogen sulphides, and the water at that depth is under extreme pressure, meaning the Loriciferans need a whole host of specialist adaptations just to survive. They rely on a trick used by many extreme-living single-celled organisms to generate energy without using oxygen, but this is the first time anyone has seen a multi-cellular animal do so.

But how do researchers know that the Loriciferans were spending their entire lives in the anoxic basins? The tiny beasts may have just drifted in from another patch of seabed, died, and then been scooped up in the sediment samples. To make sure this wasn’t the case the researchers used a fluorescent dye that only stains living cells, showing many of the Loriciferans were still alive. They also showed that there was no way the creatures could just have drifted into the basin in which they were found.

Researchers have known for a long time that bacteria, viruses and other single-celled organisms can survive in such hostile conditions, but this is the first evidence that multi-cellular animals can live, and reproduce – the researchers found several Loriciferans carrying eggs – quite happily in this bizarre alien world.

Paper reference: Danovaro, R., Dell’Anno, A., Pusceddu, A., Gambi, C., Heiner, I. and Kristensen, R.M. (2010) The first metazoa living in permanently anoxic conditions. BMC Biology, 8:30 doi:10.1186/1741-7007-8-30

‘Sauna-like’ planet found orbiting distant star

A newly-discovered planet orbiting a distant star is covered by deep oceans, according to an international team of astronomers. The ‘water world’ is only a little larger than Earth, but it is much less dense, leading the astronomers to suggest it is exceptionally watery, with a small rocky core.

...but what good's an ocean without a beach? Image: Hypothesisnow

With a ‘surface’ temperature of 190^oC, the planet may also have a rather steamy, ‘sauna-like’, atmosphere.

The planet, named GJ 1214b, consists of almost 50% water: in comparison, only around 0.06% of the Earth’s mass is water, despite it being known as the ‘blue planet’. Astronomers inferred the existence of the planet from the way it dimmed the light of its parent star every time it passed in front of it – once every 1.6 days. It also causes the star to wobble slightly as it orbits – another tell-tale sign of an orbiting planet.

The amount of light-dimming and the wobble told astronomers the size and mass of GJ 1214b, which in turn allowed them to work out its density. GJ1214b is slightly larger than Earth (its radius is 2.68 times that of Earth) and much less dense (1.9 grams per centimetre³ compared to Earth’s 5.5 grams per cm³. The only plausible way a planet could be that big but weigh so little would be if it consisted of lots of water around a rocky core, perhaps with a thin atmosphere of hydrogen and helium.

The presence of liquid water is rather exciting because, as far as we know, water is one of the prerequisites of life, and finding inhabited planets is one of the long-term goals of astronomy. The new discovery also takes us one step closer to finding a truly Earth-like planet out there somewhere. NASA’s Kepler space telescope is sensitive enough to find exo-planets even smaller than GJ 1214b, so maybe one day we’ll find a home-from-home. The only tricky part then will be actually getting there…

Paper Reference: Charbonneau , D., et al, (2009). A super-Earth transiting a nearby low-mass star. Nature, 462, p891-894. doi:10.1038/nature08679

Life on Earth is quite unlikely

Scientists have concluded that life is unlikely to form on planets around stars like our Sun because these stars emit high levels of x-rays and ultraviolet light early in their existence – both deadly to life as we know it.

“The Sun does not seem like the perfect star for a system where life might arise.” said Professor Edward Guinen from Villanova University in the USA, who carried out the work alongside other researchers from the USA and from the Netherlands. Guinen and colleagues suggest that smaller, cooler stars called orange dwarfs are the best places to look for life. Orange dwarfs live much longer than yellow stars like our Sun, and their “goldilocks zone” – the area of space surrounding the star in which planets are most likely to harbour life – will also last much longer, giving life a better chance of getting started.

And it doesn’t stop there. According to Guinen, “we have also found indications that planets like Earth are also not necessarily the best suited for life to thrive”. Instead, larger planets may be better suited to harbouring life because they can hold on to their atmospheres for longer due to their stronger gravity. They also have much larger iron cores, which support a more powerful magnetic field for longer, protecting the atmosphere and any developing life from harmful cosmic rays.

The researchers made their surprising discovery by looking at other stars very similar to our Sun, but which are much younger. The Sun, at 4.5 billion years old, is in a relatively calm phase of its lifecycle. In its early days, when it was less than half a billion years old, the Sun went through a wild phase, throwing out massive amounts of destructive radiation and making it very hard for life to survive.

Obviously life on Earth has survived despite the odds, but the work could alter where we look in our ongoing hunt for extraterrestrial life. There are many more orange dwarfs than there are Sun-like stars in the galaxy, so maybe it will be easier than we thought to find life out there.

Stars - they grow up so fast... Image: IAU

Are we happy?

“Happiness is the meaning and the purpose of life, the whole aim and end of human existence” – Aristotle.

Happiness is something we all aspire to. But how happy are we, really? Psychologists have struggled to answer this question for many years, but a team of American scientists might have found one way to do so reliably.

By analysing the words bloggers use, the scientists have come up with a way to monitor the happiness of the entire blogging population of the United States. As so many blog posts are published, the scientists could track the daily changes in the mood of the country.

Perhaps unsurprisingly, 9/11 is an unhappy day for the blogosphere, with an increase in words such as “lost”, “anger” or “tragedy” and a decrease in positive words such as “happy”. In contrast, the day on which the current US President was elected was much happier; dominated as it was by words such as “proud”, “hope” and “win”.

Using the personal details provided by many bloggers, the scientists also found that young people are least happy, and happiness increases with age, up to a point. Beyond the age of 60, happiness seems to decrease.

Finally, there is a subtle change in happiness over the course of an average week. Sunday is the happiest day, with happiness dipping mid-week. Personally, I’m not surprised!

Measuring happiness is a tricky business. People tend to misreport (intentionally or otherwise) their own happiness, and researchers cannot gain a reliable measure of someone’s happiness from observation alone. To overcome these difficulties, the new technique uses a list of words scored for their happiness: for example, on a scale of 1 – 9, “love” scores 8.72, “pancakes” 6.08, and “suicide” 1.25. By averaging the score of the words used, the scientists could determine the happiness of the blog post. The individual results could then be combined to monitor the happiness of the whole blogosphere.

So is this study a useful tool for checking our mental health, or a sinister Orwellian mind-reading device?

Happily, the study is open access, so you can make up your own mind here.

Big is beautiful

Say you were pregnant. Would you choose to give birth to a really big baby? Writing as a male who never has to face such a daunting prospect, I’m reasonably sure I’d say no. For some males (yes, males), however, the answer is a resounding yes. In fact, the males in question go so far as to choose the largest female available to make sure they father the biggest babies.

I am, of course, talking about seahorses – famous for the fact that it is male seahorses who get pregnant and give birth. Scientists from the University of Zurich in Switzerland have shown that the males of one species of seahorse, Hippocampus abdominalis, prefer large females over small ones, probably because large females produce larger eggs. Large eggs mean large babies, and large baby seahorses have more chance of surviving to adulthood. The effect of this preference on the females has been to cause an increase in female body size over time: they are now noticeably larger than the males.

Using a cleverly designed fish tank, the scientists gave males a choice between two females. The males regularly chose the largest of the pair and began to perform their elaborate mating rituals to entice her.  In contrast, females showed no clear mating preference when allowed to choose between two males.

Compared with many other animal species this is a complete role reversal. Females invest a lot of energy in producing eggs and are usually very choosy about their mates. Males tend to adopt a much less choosy “quantity over quality” approach, as sperm are cheap. In seahorses, things are a little more complicated. Male seahorses invest a lot of energy in their babies, so want to make sure the young they raise have the best start in life. Because of this, males have more to gain from carefully choosing the best females than the females do from choosing suitable males.

One question remains, however: what effect does the size of the males have on offspring survival? Not much, according to the scientists. The research paper states clearly that even “small H. abdominalis males can carry exceptionally large broods”. Ouch.

Male pregnancy - now there's a bad idea. Image credit: Joanne Merriam. Used under GNU free documentation licence