The World’s Smallest Vertebrate – A Tiny New Guinean Frog

Researchers from Louisiana State University have discovered the world’s new smallest vertebrate, a frog so small you could fit two on a dime end-to-end. From National Geographic:

The world’s smallest known vertebrate is a frog the size of a housefly, a new study says.

At an average of 7.7 millimeters long, the newfound Paedophryne amauensis is a hair smaller than the previous record holder, the Southeast Asian fishspecies Paedocypris progenetica, whose females measure about 7.9 millimeters…

It’s obvious “they’re adapting to fill a niche that nothing else is filling,” he said.

Indeed, the frogs likely evolved their tiny sizes to eat tiny invertebrates, such as mites, that are ignored by bigger predators, said study co-author Christopher Austin, a biologist at Louisiana State University in Baton Rouge…

Scientists locate the teensy animals by listening for their calls and trying to zero in on the sources of the sounds—no mean feat, since the high pitch of the calls make their sources especially hard for human hearing to locate.

Austin and graduate student Eric Rittmeyer tried four times to find the frogs before exasperatedly grabbing a big handful of leaf litter and putting it in a plastic bag.

The scientists then combed through the contents until “eventually we saw this tiny thing hop off one of the leaves,” Austin said.

The frogs are so small it’s hard to see their earth-colored skin patterns with the naked eye, so Austin took pictures and then zoomed in, using a digital camera like a microscope.

But photographing the amphibians was just as challenging as finding them. When Austin brought the camera to his eye, the subject would often already be gone.

The new frogs are “incredibly good jumpers—they can jump 30 times [longer] than their body size,” said Austin, whose study was published January 11 in the journal PLoS ONE.

That’s pretty incredible; there are some organisms that seem to straddle the boundaries between different worlds, and this is one of them. I want a report back from this frog on what life in the insect world is like. 

Photograph by Christopher Austin, via National Geographic

New Species Discovered Near Antarctic Seafloor

A plethora of new species have been discovered around hydrothermal vents near Antarctica. As always, the ocean has many surprises for us.

From ScienceDaily:

‘Hydrothermal vents are home to animals found nowhere else on the planet that get their energy not from the Sun but from breaking down chemicals, such as hydrogen sulphide,’ said Professor Alex Rogers of Oxford University’s Department of Zoology, who led the research. ‘The first survey of these particular vents, in the Southern Ocean near Antarctica, has revealed a hot, dark, ‘lost world’ in which whole communities of previously unknown marine organisms thrive.’

Highlights from the ROV [Remotely Operated Vehicle] dives include images showing huge colonies of the new species of yeti crab, thought to dominate the Antarctic vent ecosystem, clustered around vent chimneys.

We heard about yeti crabs earlier, when we learned that one species of them off the coast off Costa Rica may farm bacteria on its claws by waving them over methane-seeping fissures to feed them, then chowing down. Obviously cold fissures by Costa Rica are very different from hydrothermal vents by Antarctica, but it would be awesome if we found that a species had the same strategy there.

Elsewhere the ROV spotted numbers of an undescribed predatory seastar with seven arms crawling across fields of stalked barnacles and found an unidentified pale octopus nearly 2,400 metres down on the seafloor.

A seastar is a starfish, something I did not know. A predatory seven-armed starfish sounds like a thing of nightmares – if you’re a tiny sea animal anyway.

‘What we didn’t find is almost as surprising as what we did,’ said Professor Rogers. ‘Many animals such as tubeworms, vent mussels, vent crabs, and vent shrimps, found in hydrothermal vents in the Pacific, Atlantic, and Indian Oceans, simply weren’t there.’

The team believe that the differences between the groups of animals found around the Antarctic vents and those found around vents elsewhere suggest that the Southern Ocean may act as a barrier to some vent animals. The unique species of the East Scotia Ridge also suggest that, globally, vent ecosystems may be much more diverse, and their interactions more complex, than previously thought…

‘These findings are yet more evidence of the precious diversity to be found throughout the world’s oceans,’ said Professor Rogers. ‘Everywhere we look, whether it is in the sunlit coral reefs of tropical waters or these Antarctic vents shrouded in eternal darkness, we find unique ecosystems that we need to understand and protect.’

Very cool, as always. Scientists who look for new ocean species must laugh at their terrestrial counterparts; it’s like exploring space versus exploring your backyard. But now the real question: how do these new species taste?

“Ocean Bacteria Glow to Turn Themselves Into Bait”

Aaaand we’re back! I hope you had a lovely break, and that one of your new year’s resolutions was to read even more science! I’ve been off in the non-virtual world for the past week, but it is time to get back to business. And remember that for more science goodness you can follow Science Picks on Twitter at @SciencePicks, or if you’re Twitter-averse you can see the extra links I tweet on the sidebar to the right. 

Not Exactly Rocket Science has an interesting article on glowing ocean bacteria and why they do what they do, with a bit of an introduction here:

On 25 January 1995, the British merchant vessel SS Lima was sailing through the Indian Ocean when its crew noticed something odd. In the ship’s log, the captain wrote, “A whitish glow was observed on the horizon and, after 15 minutes of steaming, the ship was completely surrounded by a sea of milky-white color.” The eerie glow appeared to “cover the entire sea area, from horizon to horizon . . . and it appeared as though the ship was sailing over a field of snow or gliding over the clouds”. The ship took six hours to sail through it.

These glowing seas have featured in sailor stories for centuries. The crew of the Nautilius encountered the phenomenon in Jules Verne’s Twenty Thousand Leagues Under the Sea. And in 2006,  Steven Miller actually managed to recover satellite images of the very same patch seen by the crew of the SS Lima – it stretched over 15,000 square kilometres, the size of Connecticut or Yorkshire.

The glowing waters are the work of bioluminescent bacteria – microbes that can produce their own light. They are found throughout the oceans, although usually in smaller numbers than the giant bloom responsible for the SS Lima’s sighting. In many cases, they form partnerships with animals like fish and squid, taking up residence inside their hosts and paying their rent by providing light for navigation or defence.

But many glowing bacteria live freely in the open ocean, and they glow nonetheless. Creating light takes energy, and it’s not something that’s done needlessly. So why do the bacteria shine? One of the most common answers – and one that Miller proposed to explain his satellite images – is that the bacteria are screaming “Eat me!” at passing fish. A fish’s guts are full of nutrients, and it can carry bacteria across large distances. The bacteria, by turning themselves into glowing bait, get a lift and a meal.

The article goes on to explain a study that showed this in action: basically, zooplankton – a classification for small organisms that drift around in bodies of water – were given a choice of eating glowing or non-glowing bacteria, and they tended to choose the glowing bacteria. Presumably this is because the bacteria only glow when they’re grouped together, which happens when they find a tasty piece of detritus to hang onto. Glowing bacteria means there’s food around, so they’re a nice target.

As a side effect, organisms that eat glowing bacteria will sometimes end up glowing themselves, making them big targets for fish. A deadly circle of life, all so that some bacteria can hitch a ride. 

Small Spiders’ Brains Fill Up Most of Their Body Cavity

If spiders weren’t creepy enough… It turns out that the smaller a spider is, the larger its brain is in proportion to its body size. This is how a tiny spider and a huge spider can have equally complex behaviour. What this means anatomically is that in some spiders, the central nervous system takes up as much as 80% of the body cavity, with their brains literally spilling into their legs. 

More from National Geographic:

Taking up so much body space for a brain would seem to be a problem for a spider’s other organs, Eberhard said. “But [that aspect] hasn’t really been studied.”

Just by the way the spiders look, though, it would make sense that the arachnids are trading something for their big brains.

For instance, in the jumping spider Phidippus clarus, which the researchers examined in a separate study, the adult’s digestive system is in the spider’s cephalothorax—its head and body cavity.

But “in the young one, all that stuff is filled up with brain,” and the baby spider has a less developed digestive system. It’s still unclear, though, what impact this has on the developing spiders…

Presumably, large brains are necessary to spin webs, a behavior thought to be more complex that, say, “a larval beetle that simply eats its way through the fungus where it lives,” Eberhard wrote in an article describing the research…

It’s a weird concept, having so much of a body filled up with the central nervous system (brain and spinal cord). I wonder how or if it relates to spiders’ reaction times, if their sensory organs (including skin) are so very close to their central nervous system. Is there a difference in reflexes between small and large spiders, or young and adult, attributable to relative brain size? Maybe we’ll find out in the future!

Ants Release Airborne Poison to Paralyze Termites

Ants just got scarier. A certain type of African ant surrounds termites and sprays them with a toxin that eventually paralyzes them.

From Not Exactly Rocket Science:

C.striatula is a specialised termite-hunter. When it finds a termite, it raises its sting into the air, releasing chemicals that summon nearby nestmates. If the termite is a soldier, armed with powerful jaws, up to 15 ants can gather round. All of them stay a centimetre away from the termite, aiming their stings at it like fencers with swords outstretched. They close in, but they still never actually touch.

Termites don’t retreat – they defend their nests no matter the danger. That is a fatal mistake. After ten minutes of stand-off, the termite starts to shake. It rolls onto its back, with its legs batting the air in helpless convulsions. Within moments, it’s paralysed, and the ants finally move in and grab it.

C.striatula behaves in the same way when it finds other ants in its territory. These intruders have the good sense to flee, even if they’re much larger than C.striatula and even if they have the weight of numbers on their side.

It’s clear that the chemicals released from C.striatula’s sting do three things: they rally other workers; they repel other ants; and they paralyse termites…

Many animals have projectile weapons: some ants can spray formic acid; the  bombardier beetles squirt enemies with noxious burning chemicals; the spitting cobras spit venom; and both velvet worms and spitting spiders can spew immobilising glue.

In all these cases, there is an obvious and noticeable stream of liquid. By contrast, C.striatula’s long-range chemical weapon seems all the more sinister for its invisible nature. Only one other animal has something similar – another ant called Platythyrea conradti . It also raids termite nests. When it encounters a defending soldier, it drops into a crouch and opens its jaws. It never bites, and it doesn’t need to. Glands in its mouth release an airborne poison that paralyses the termites, in the same way that C.striatula does with its sting.

I’d love to see a video of this chemical warfare in action, but in lieu of that here’s a video from National Geographic showing an ant attack on a termite nest:

There’s a complex and fascinating world going on underneath us.

Bacteria-Farming Crab

Researchers have discovered that a certain species of crab apparently actively grows bacteria on its arms and eats them as its main source of food. From National Geographic

In 2006 scientists uncovered another species of yeti crab, K. puravida, living in cold, methane-seeping fissures about 3,300 feet (1,000 meters) deep near Costa Rica.

K. puravida regularly waved its claws slowly and rhythmically, puzzling scientists…

One early explanation for the behavior was that the crabs were trying to keep others at a distance.

But chemical analysis of K. puravida‘s tissues and the bacteria dwelling on its silky arms revealed the crustaceans dine mostly on these bacteria.

Video taken by submarine then revealed that the crabs harvest their crops using highly specialized hairy mouth appendages, which scrape the bacteria off their arms…

Researchers now suggest the claw-swaying helps wash nutrients over the bacteria, essentially fertilizing them…

It remains uncertain whether the yeti crab’s hairy appendages might help detect currents in the water. If so, the appendages may help crabs identify the sources of the nutrients that sustain their microbe “farms.” …

Deep-sea shrimp and other animals had been found with bacteria growing on them before, but this is the first clear evidence of a deep-sea animal farming its bacteria, said Thurber, whose study appeared November 30 in the journal PLoS ONE.

“This shows us how little we know about the deep sea, and how much more we might find and have to protect, as exploration for resources expands into these areas.”

That’s pretty fascinating behaviour; I wonder if this crab’s intelligence is unexpectedly high, or if this behaviour arose very accidentally and is now ingrained? It also reminds me of ants that farm aphids, an even more incredible behaviour in its resemblance to humans. These ants protect aphids and store aphid eggs, even taking aphid eggs with them when they start new colonies. They apparently stroke the aphids to “milk” honeydew out of them, which they then consume. And you thought we were the only farmers…

Anyway, as the last quoted paragraph states, this just reaffirms how much we have to learn about the deep sea and the natural world in general. It’s an exciting world out there!

“Ten Weirdest Life-Forms of 2011”

National Geographic has a cool slideshow of the ten weirdest new life-forms seen in 2011, including a cyclops shark, tadpoles with fangs and the deepest-living animal found to date. And an ant with mind-controlling fungus growing out of its head, but I’m trying to block that one out.

We still have many, many species to discover out there – we only know a small fraction of them. Below is a table of the catalogued and predicted species on Earth and specifically in the ocean. The totals come out to 1/7th of Earth’s species having been catalogued so far, and less than 1/11th of ocean species, although those numbers are obviously subject to a lot of error.

Mora C, Tittensor DP, Adl S, Simpson AGB, Worm B, 2011 How Many Species Are There on Earth and in the Ocean? PLoS Biol 9(8): e1001127. doi:10.1371/journal.pbio.1001127, via Life Lines

We may have the cultural perception that the days of exploration are over, but they’re definitely not. There’s a lot more to discover out there, and there probably will be for generations. 

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