This is tedious. We’ve been doing this for years now, with no progress. Two sides, shouting at each other, shouting past each other, resorting to caricatures, and making no/little attempt at mutual understanding. Let’s do better.
A typical starfish has five-sided symmetry. With no clear head, the starfish can move in any direction, led by any one of its five arms. If you were feeling particularly cruel, you could fold one up in five different ways, so each half fitted exactly on top of the other. We humans, like many other animals, have only two-sided symmetry. We’re ‘bilateral’ – our right half mirrors our left, and we have an obvious head.
These two body plans might look radically different, but looks can be deceiving. Chengcheng Ji and Liang Wu from the China Agricultural University have found that starfish have hidden bilateral tendencies, which reveal themselves under times of stress.
Most life on Earth exists as single cells. But the ones comprised of many cells, from the tiniest ant to the tallest tree, have had an undeniable impact on our planet. These ‘multicellular’ creatures evolved from single-celled ancestors at least 25 times throughout Earth’s history. These transitions are arguably some of the most significant in evolution, but we only have a vague understanding of how they happened.
It probably went a bit like this. A single cell split into two and rather than going their separate ways, they stayed together. This happened again and again. Eventually, the groups of individual cells became individuals of grouped cells, evolving as a unit. It’s the story of how I became we, and how we became I again.
In an elegant new experiment, William Ratcliff from the University of Minnesota has shown that this story could have been a surprisingly quick one. In his laboratory, he successfully nudged single-celled brewer’s yeast into multicellular clusters, within just a few months. The clumps of cells evolved as one. They even developed a primitive division of labour, with some of them deliberately dying so that the others could grow and reproduce.
I’ve written about this discovery for Nature News, so head over there to read the full take.
“God save thee, ocean sunfish
From the fiends that plague thee thus
Why look’st thou so? With thy large shoals,
Thou fed the albatross.”
– Samuel Taylor Coleridge, sort of.
Albatrosses are superb long-distance fliers that can scour vast tracts of ocean in search of food. But sometimes, food comes to them. In July 2010, Tazuko Abe from Hokkaido University found albatrosses cleaning a school of ocean sunfish, basking at the surface of the western Pacific Ocean.
The ocean sunfish is a truly bizarre animal. It looks like someone cut the head off a much bigger fish and strapped fins to it. It’s the largest of the bony fish*. The biggest one ever found was 2.7 metres in length and weighed 2.3 tonnes. The youngsters, of course, are much smaller. The ones that Abe saw on his research cruise were just 40 centimetres long. There were at least 57 of them, each turned on its side so its broad flank faced the water surface.
The basking shoals were attending a sort of sunfish spa. The fish were infested with parasites. Pennella, a long scarlet relative of shrimp and crabs, was embedded headfirst in the flesh beneath their fins, busily sucking their blood. But not for long – black-footed and Laysan albatrosses were attracted to the shoal and picked the Pennella off their bodies. In some cases, the sunfish seems to be courting the birds, following them around and swimming sideways next to them.
Ocean sunfish live throughout the oceans but they often spend time at the surface before diving to the depths. Some scientists think that they’re absorbing heat from the sun, but it’s possible that they could also be looking for a spot of personal hygiene.
These fish can play host to at least 50 species of parasites, and they often have considerable numbers on their large bodies. Many ocean animals rely on cleaner fish or cleaner shrimp to rid them of parasites. It’s possible that albatrosses might fulfil the same role for ocean sunfish.
Of course, the association might have been a one-off. However, there are other reports of seabirds such as shearwaters and albatrosses flocking around schools of basking sunfish. This instance stands out only because Abe has photographic evidence that they were actually parasites. As he rightly points out, such events would be difficult to spot among the vastness of the open ocean.
* Fish have skeletons that are either made of cartilage, as in sharks and rays, or bone, as in all the others.
Reference: Abe, Sekiguchi, Onishi, Muramatsu & Kamito. 2011. Observations on a school of ocean sunfish and evidence for a symbiotic cleaning association with albatrosses. Marine Biology http://dx.doi.org/10.1007/s00227-011-1873-6
In December of 2011, Fred Kraus from the Bishop Museum in Hawaii announced that he had discovered the world’s smallest frogs. The two coin-sized species were just 8.1 to 9.3 millimetres long. But these miniscule amphibians now share a different record – they were the world’s smallest frogs for the shortest amount of time.
Less than a month after Kraus’s announcement, Eric Rittmeyer and Christopher Austin from Louisiana University have found an even smaller frog, just 7 to 8 millimetres long. It’s dwarfed by a dime. It’s not just the world’s smallest frog, but the world’s smallest back-boned animal.
The new species, Paedophryne amauensis, is a close relative of the tiny pair from December – Paedophryne dekot and Paedophryne verrucosa). Extremely tiny frogs have evolved at least 11 times, but the Paedophryne group is unique in that all of its members are miniscule. They were first discovered in 2002, and six species have been discovered so far. All of them live in Papua New Guinea. Clearly, this corner of the world is a haven for the tinier side of life.
A bout of Salmonella food poisoning isn’t a pretty affair. Your digestive tract churns, you can’t keep your food down, and you feel exhausted. But you aren’t the only one affected. Your gut contains trillions of bacteria, which outnumber your own cells by ten to one. They are your partners in life, and they are also transformed by the presence of the invading Salmonella.
Minority members of this intestinal community start to bloom, greatly increasing in number as the guts around them become inflamed. And these gut bacteria start to trade genes with Salmonella.
These swaps are a regular part of bacterial life. In their version of sex, two cells become united by a physical bridge, through which they shunt rings of DNA called plasmids. These rings can act like mobile weapons packages. Some give otherwise harmless bacteria the ability to cause disease. Others confer resistance to antibiotics. It’s a network of shady arms trading, and in your inflamed bowels, it happens at an unprecedented level.
Philcoxia couldn’t look more unassuming. It’s a small herb that lives in Brazil’s Campos Rupestres region, a sparse plateau of rocky outcrops and white sands. All you’d see of it are a handful of twigs sticking out from the grains, topped with small purple flowers and even smaller leaves. You wouldn’t think that it’s the type of plant that can kill animals.
To find Philcoxia’s grisly secret, Caio Pereira had to look underground. The plant biologist from Unicamp, Brazil, found that the plant traps and digests tiny worms with sticky underground leaves.
The giant tortoises of the Galapagos Islands are large, conspicuous and slow-moving. Encased in their shells, they might seem like impregnable tanks, but they have no defences against machetes. It’s no surprise that their numbers plummeted at the hands of humans who landed on the islands – first pirates, then whales and fur-traders, then permanent settlers.
The lineage of giant tortoise from the island of Floreana was one of the first permanent casualties. It was extinct by 1835, just 15 years after a certain Charles Darwin visited the Galapagos.
Or was it? A team of scientists has found traces of the tortoises, which suggests that a lost population might still be alive on nearby Isabela Island, the largest of the Galapagos archipelago. The team found neither droppings, nor grainy photos, nor footprints. They found genetic footprints.