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.
Forty years ago, the elkhorn coral was one of the most common species in the Caribbean. Five years ago, it was listed as critically endangered. The coral’s woes are many but, aside from the warming temperatures, predators and storms that affect all corals, the elkhorn is also plagued by a highly contagious malady called white pox disease. White lesions erupt all over the coral’s branches, representing areas where its animal tissue has wasted away to leave the white skeleton.
Now, Kathryn Patterson Sutherland from Rollins College in Florida has discovered the cause of white pox disease, and it’s an unexpected one – us. We have literally landed the elkhorn in s**t.
The cleaner fish Laborides dimidiatus is cross between a janitor and a medic. It runs special “cleaning stations”, which other fish and ocean animals visit for a regular scrub. The cleaners remove parasites from their clients, even swimming into the open jaws of predators like moray eels and groupers. They’re like living toothbrushes and scrubs. And they work hard – every day, a single cleaner inspects over two thousand clients, and some clients visit the stations more than a hundred times a day.
The cleaners, and their relationships with their clients, make a classic case study for biologists studying the evolution of cooperation. The tiny fish clearly get benefits in the form of a meal, and they enjoy a sort of diplomatic immunity from otherwise hungry hunters. On the face of it, the clients also benefit by getting scrubbed of harmful parasites. Now, Peter Waldie from the University of Queensland has shown how important this hygiene is.
This monstrous fish is a tambaqui, a close relative of the piranha. Fortunately, it doesn’t share its cousin’s flesh-eating lifestyle. Instead, the 30-kilogram tambaqui (or pacu) is a vegetarian. It swims through the flooded forests of the Amazon, eating fruits that drop from the overhanging trees. In doing so, it acts as an vehicle for the Amazon’s seeds, carrying them to distant parts of the jungle within its gut.
This is a role that we normally associate with birds or monkeys, but Jill Anderson from Cornell University has found that the tambaqui is a champion seed carrier. It can spread seeds over several kilometres, further than almost any other fruit-eating animal on record.
In June 1935, the cane toad began its invasion of Australia. Sailors brought the animal over from Hawaii in an attempt to control the cane beetle that was ravaging Australia’s sugar cane crops. It was a mistake that the continent’s wildlife would pay for. The toad did nothing to stop the beetles. Instead, it launched its own invasion, spreading across the continent from its north-eastern point of entry. As it marched, it left plummeting populations of native species in its wake.
The toads are born conquerors. Females can lay 35,000 eggs many times a year, and each can develop into a new frog in less than 10 weeks. They’re unfussy eaters and they’ll munch away on bird eggs, smaller native frogs and more. And they have large glands behind their heads, which secrete a milky poison. Local predators (or domestic pets) that try to eat them tend to die.
Now, Daniel Florance from the University of Sydney has found a clever way of corralling the cane toad invasion. He realised that humans have continued to give the toad a hand, long after we first brought them to Australia. By creating dams and troughs, we provided the toad with watery staging grounds that allowed it to spread across otherwise impassably dry land.
Around $263 billion US dollars, if a new paper is to be believed.
I’ve wrote about the paper for Nature today and the story appears on their The Great Beyond blog. Head over there to read the full thing. Here’s an excerpt:
Based on a survey of 44 Brazilian taxonomists (representing 9% of the country’s total), the duo calculated the average cost of training, funding and equipping people in the field. This might seem like an unrepresentative sample, but Brazil contains 10% of the world’s animal species and the country’s taxonomists are among the world’s most prolific. Their salaries also come close to the global average for professors.
Carbayo and Marques found that the average researcher described 25 species in their career. With around 1.4 million known animals, and an estimated 5.4 million species to discover, the duo calculated that it would take US$263 billion to cover them all. Their figures are published in an open-access letter in Trends in Ecology and Evolution.
Not all species are equal. It costs three times as much to describe a new vertebrate than an insect, although there are almost 300 times more of the latter left to identify. “You can effectively consider the warm-blooded things as done,” says Alistair Dove, who studies fish parasites.
In the rest of the piece, Chris Laly from London’s Natural History Museum comments on how online tools could drive th costs down, and Al Dove (@para_sight) says that not all taxonomists are equal. You should also read Craig McClain’s excellent WIRED article on how the scientists who study life’s richness are themselves an endangered species.
Image by Retro traveler
In the wild, you may occasionally see a penguin wearing a metal band around the base of one of its flippers. These bands aren’t the latest in penguin bling – they’re tools used by scientists to track the lives and movements of individuals. The bands are controversial – some say that they are innocuous, while others argue that they slow and hurt the very birds that scientist are trying to conserve. Now, Claire Saraux from the University of Strasbourg has evidence that might swing the debate – a ten-year study showing that banded birds die sooner and raise fewer chicks.
“I heard a rustling in a tree near, and, looking up, saw a large red-haired animal moving slowly along, hanging from the branches by its arms. It passed on from tree to tree until it was lost in the jungle, which was so swampy that I could not follow it.”
These are the words of the great naturalist Alfred Russell Wallace, describing how he caught sight of his very first orangutan. Around two weeks later, Wallace found his second individual and, as you would expect for a 19th century British explorer, he shot it dead.
During his fifteen-month stay in Borneo, Wallace ‘collected’ a further 28 orangutans and his tales of slaughter and science are vividly described in his famous tome, The Malay Archipelago (immortalised here by Google).
Wallace wasn’t the only explorer to shoot his way through Borneo’s orangutan population. Odoardo Beccari shot or saw at least 26 individuals in just over 5 weeks, while Emil Selenka collected around four hundred specimens over four years. All of these records attest to the fact that orangutans were relatively common in the late 19th century, such that zealous Europeans had no problems in finding them.
The same can’t be said now. Field scientists working in Borneo rarely see a wild orangutan and when they do, they’re usually alone or in very small groups. You can travel down the very rivers where naturalists once described seeing orangutans many times in the same day, and find only nests.
Today, we might raise an eyebrow at the trigger-happy antics of Wallace and his contemporaries but, at the very least, they carefully documented what they did. And those tales, together with museum collections, have allowed Erik Meijaard from The Nature Conservancy in Indonesia to reconstruct the history of the Bornean orangutan since the 19th century.
Not Exactly Pocket Science is a set of shorter write-ups on new stories with links to more detailed takes. It is meant to complement the usual fare of detailed pieces that are typical for this blog.
Spongebob’s genome reveals the secrets of building an animal
Sponges are animals but, outside of children’s cartoons, they’re about as different from humans as you can imagine. These immobile creatures lie on the very earliest branch on the animal family tree. They have no tissues or organs – their bodies are made of just two layers of cells, twisted and folded into simple shapes. But despite this simplicity, the first complete sponge genome tells us a lot about what it takes to build an animal.
The genome was sequenced from an Australian species called Amphimedon queenslandica by a large team of scientists led by Mansi Strivastava from the University of California, Berkeley. It tells us that sponges share a ‘genetic toolkit’ with humans and all other animals. This includes 4,670 families of genes that are universal to all animals, 1,286 of which separate us from our closest single-celled relatives, the choanoflagellates. Within these families lie the keys to a multicellular existence.
This shared toolkit controls all the fundamental processes that allow individual cells to cooperate as part of a single creature, including how to divide, die, grow together, stick to one another, send signals to one another, take up different functions, and tell the difference between each other and outsiders. They also include many genes that are implicated in cancer, a disease where individual cells go rogue and multiply out of control at the expense of the collective. The presence of cancer-related genes in the sponge genome tells us that as long as cells have been cooperating within a single body, they have needed to guard against the threat of cancer.
Srivastava estimates that the foundations of multicellular life were laid between 600 and 800 million years ago. More than a quarter of the big genetic changes that separate humans from the single-celled choanoflagellates took place during this window, before sponges split off from the ancestors of all other animals. The last common ancestor of all animals emerged during this period and it was a creature of remarkable complexity – a multicellular species that could sense, react to and exploit its environment.
Holy extinction, Batman! One of America’s most common bats could be wiped out in 16 years by new disease
The little brown bat is one of the most common bats in North America but in 16 years, people on the East Coast will be lucky to see any. The bat is being massacred and the culprit is a new disease known as white-nose syndrome caused by the ominously named fungus Geomyces destructans. The fungus grows on the wings, ears and muzzles of hibernating bats, rousing them too early from their deep sleep, sapping their fat reserves and causing strange behaviour.
White-nose syndrome was first identified in a New York cave in February 2006, but it spreads fast. In the last four years, it has covered over 1200 km and contaminated wintering roosts throughout the north-eastern US and its neighbouring Canadian provinces. In infected areas, the fungus is slaughtering bats at a rate of around 45% a year. Cave floors are littered with carcasses.
Five years ago, the little brown bat was thriving, thanks to the installation of bat boxes, conservation efforts and a reduction in pesticide use. The eastern seaboard alone was home to 6.5 million of them. But all of that good is being undone by a single disease. Using a mathematical model, Winifred Frick from Boston University calculated a 99% chance that the species will become locally extinct within 16 years. Even if the current death rate slows to just 5% a year – a highly optimistic target– the population will still collapse to around 65,000 individuals. These last survivors would be just 1% of the previous total, with a 60% chance of dying off by the end of the century. At this stage, the question isn’t if the little brown bat will go locally extinct, but when.
This is just the tip of the iceberg. White-nose syndrome is spreading across North American and at least six other bat species are affected. These animals eat such a large volume of insects that their disappearance would have severe economic and ecological consequences. There’s a desperate need for more research to understand the disease, to keep a track of it, to find ways of fighting it, and to ensure that something like it doesn’t happen again. Frick thinks that white-nose syndrome spread so quickly with such devastating results that it must have been introduced from another part of the world, hitting species whose immune systems were totally unprepared for it. This problem of “pathogen pollution” is a neglected issue in conservation – perhaps the demise of the little brown bat will provide the impetus to take it seriously.
Reference: Science http://dx.doi.org/10.1126/science.1188594
The Earth’s oceans are mysterious and largely unexplored. Many of their inhabitants are familiar to us but their whereabouts and numbers are far less clear. This is starting to change. In two new studies, Boris Worm from Dalhousie University has revealed an unprecedentedly detailed portrait of the planet’s marine life, from tiny plankton to mighty whales. And with that knowledge comes concern, for neither study paints an optimistic picture about the fate of tomorrow’s seas, as changing climate slowly raises their temperature.
Graduate student Daniel Boyce focused on some of oceans’ smallest but most important denizens – the phytoplankton. These tiny creatures are the basis of marine food webs, the foundations upon which these watery ecosystems are built. They produce around half of the Earth’s organic matter and much of its oxygen. And they are disappearing. With a set of data that stretches back 100 years, Boyce found that phytoplankton numbers have fallen by around 1% per year over the last century as the oceans have become warmer, and if anything, their decline is getting faster. Our blue planet is becoming less green with every year.
Meanwhile, post-doc Derek Tittensor has taken a broader view, looking at the worldwide distributions of over 11,500 seagoing species in 13 groups, from mangroves and seagrasses, to sharks, squids, and corals. His super-census reveals three general trends – coastal species are concentrated around the western Pacific, while ocean-going ones are mostly found at temperate latitudes, in two wide bands on either side of the equator. And the only thing that affected the distribution of all of these groups was temperature.