92 posts tagged nature
Giant clams use ‘gems’ to harvest sunlight
University of California, Santa Barbara, University of Pennsylvania Original Study
Scientists say they’ve uncovered the utility of the amazing iridescent structures on giant clams. The structures, known as iridocytes, filter sunlight. That sunlight feeds the symbiotic algae that grow inside clams. “Many mollusks, like squid, octopuses, snails, and cuttlefish have iridescent structures, but almost all use them for camouflage or for signaling to mates. We knew giant clams weren’t doing either of those things, so we wanted to know what they were using them for,” says Alison Sweeney, an assistant professor in the physics and astronomy department at the University of Pennsylvania. These algae convert the abundant sunlight of the clams’ equatorial home into a source of nutrition but are not particularly efficient in the intense sunlight found on tropical reefs; sunlight at the latitude where these clams live is so intense that it can disrupt the algae’s photosynthesis, paradoxically reducing their ability to generate energy. (via Giant clams use ‘gems’ to harvest sunlight - Futurity)
This Bizarre Organism Builds Itself a New Genome Every Time It Has Sex
Oxytricha trifallax lives in ponds all over the world. Under an electron microscope it looks like a football adorned with tassels. The tiny fringes are the cilia it uses to move around and gobble up algae. What makes Oxytricha unusual, however, is the crazy things it does with its DNA. Unlike humans and most other organisms on Earth, Oxytricha doesn’t have sex to increase its numbers. It has sex to reinvent itself. When its food is plentiful, Oxytricha reproduces by making imperfect clones of itself, much like a new plant can grow from a cutting. “If they’re well fed, they won’t mate,” said Laura Landweber, a molecular biologist at Princeton University and lead author of a recent study on Oxytricha genetics. But when Oxytricha gets hungry or stressed, it goes looking for sex. When two cells come together (as in the image above), the ultimate result is: two cells. “They’ve perfected the art of sex without reproduction,” Landweber said. The exterior of the two cells remains, but each cell swaps half of its genome with the other. “They’re entering into this pact where each one is going to be 50 percent transformed,” Landweber said. “They emerge with a rejuvenated genome.” In size, Oxytricha’s genome is roughly comparable to ours. It has about 18,500 genes, compared to 20,000 or so for humans. But that’s one of the few things we have in common with this pond-dwelling protist. Unlike the cells of plants and animals (fungi too, for that matter), an Oxytricha cell has at least two nuclei. “You can see them under the microscope if you stain for DNA,” Landweber said. One nucleus contains a working copy of the genome—all the DNA it uses to make the RNA and proteins essential for everyday life. Last year, Landweber’s team discovered that the DNA in Oxytricha’s working nucleus is partitioned into approximately 16,000 “nanochromosomes,” most containing just a single gene. It’s a staggering number—most common plants and animals have somewhere between a dozen and a hundred chromosomes (we humans have 23 pairs). (via This Bizarre Organism Builds Itself a New Genome Every Time It Has Sex | WIRED)
First ban on shark and manta ray trade comes into force
All trade in five named species of sharks is to be regulated from now on, in a significant step forward for conservation.
Without a permit confirming that these sharks have been harvested legally and sustainably, the sale of their meat or fins will be banned. The regulation was agreed last year at a meeting of the Convention on International Trade in Endangered Species (Cites) in Thailand. The rules also apply to manta rays. Shark numbers have been under severe pressure in recent years as the numbers killed for their fins soared. Scientific estimates put the number at about 100m a year, with demand driven by the fin soup trade in Hong Kong and China. Campaigners have been seeking to stop the unregulated trade in sharks since the 1990s but it was only at the Cites meeting in Bangkok last year that they finally managed to achieve sufficient votes to drive through the ban. From Sunday, the oceanic whitetip, the porbeagle and three varieties of hammerhead will be elevated to Appendix II of the Cites code, which means that traders must have permits and certificates. Manta rays, valued for their gills which are used in Chinese medicine, will also be protected. The survival of all these species has been threatened by over fishing. (via BBC News - First ban on shark and manta ray trade comes into force)
Evolution’s Random Paths Lead to One Place
A massive statistical study suggests that the final evolutionary outcome — fitness — is predictable.
In his fourth-floor lab at Harvard University, Michael Desai has created hundreds of identical worlds in order to watch evolution at work. Each of his meticulously controlled environments is home to a separate strain of baker’s yeast. Every 12 hours, Desai’s robot assistants pluck out the fastest-growing yeast in each world — selecting the fittest to live on — and discard the rest. Desai then monitors the strains as they evolve over the course of 500 generations. His experiment, which other scientists say is unprecedented in scale, seeks to gain insight into a question that has long bedeviled biologists: If we could start the world over again, would life evolve the same way? Many biologists argue that it would not, that chance mutations early in the evolutionary journey of a species will profoundly influence its fate. “If you replay the tape of life, you might have one initial mutation that takes you in a totally different direction,” Desai said, paraphrasing an idea first put forth by the biologist Stephen Jay Gould in the 1980s. Desai’s yeast cells call this belief into question. According to results published in Science in June, all of Desai’s yeast varieties arrived at roughly the same evolutionary endpoint (as measured by their ability to grow under specific lab conditions) regardless of which precise genetic path each strain took. It’s as if 100 New York City taxis agreed to take separate highways in a race to the Pacific Ocean, and 50 hours later they all converged at the Santa Monica pier. The findings also suggest a disconnect between evolution at the genetic level and at the level of the whole organism. Genetic mutations occur mostly at random, yet the sum of these aimless changes somehow creates a predictable pattern. The distinction could prove valuable, as much genetics research has focused on the impact of mutations in individual genes. For example, researchers often ask how a single mutation might affect a microbe’s tolerance for toxins, or a human’s risk for a disease. But if Desai’s findings hold true in other organisms, they could suggest that it’s equally important to examine how large numbers of individual genetic changes work in concert over time. “There’s a kind of tension in evolutionary biology between thinking about individual genes and the potential for evolution to change the whole organism,” said Michael Travisano, a biologist at the University of Minnesota. “All of biology has been focused on the importance of individual genes for the last 30 years, but the big take-home message of this study is that’s not necessarily important.” (via Yeast Study Suggests Genetics Are Random but Evolution Is Not | Simons Foundation)
Clever Trout Match Chimps in a Cognitive Challenge
Certain forms of collaboration are supposed to be so sophisticated that only the smartest creatures—namely humans and perhaps a few close relatives—are capable of them. Yet this exclusive club has a new and unexpected member: a species of fish, a class of animals seldom associated with high-level intelligence. As demonstrated in a series of experiments published today in Current Biology, coral trout not only solicit the help of moray eels when they hunt, but also pick their hunting partners wisely. They know when they need help, and quickly learn which eels best provide it. It’s a seemingly simple yet surprisingly sophisticated cognitive trick. “Prior to our study, chimpanzees and humans were the only species known to possess both of these abilities,” said zoologist Alex Vail of England’s University of Cambridge. “I think the evidence is mounting that fish have more going on in their heads in terms of cognition than they have been given credit for.” In earlier research, Vail and colleagues observed that coral groupers and coral trout—two closely-related species of large, reef-dwelling predatory fish found in the Indian and western Pacific oceans—used their bodies to point moray eels at prey hiding in otherwise inaccessible seabed holes. The eels followed directions, flushing prey from the holes and giving groupers an easy meal. In the cognitive argot, this appeared to be evidence of referential communication: groupers didn’t merely express an emotional state or some straightforward want, as with a mating display. Rather, their gestures referred to an external object, and seemed to display conscious intent. It was not the behavior of a stimulus-response machine. (via Clever Trout Match Chimps in a Cognitive Challenge | Science | WIRED)
Researchers analyzing human, fly, and worm genomes have found that these species have a number of key genomic processes in common, reflecting their shared ancestry. The findings, appearing Aug. 28, 2014, in the journal Nature, offer insights into embryonic development, gene regulation and other biological processes vital to understanding human biology and disease. The studies highlight the data generated by the modENCODE Project and the ENCODE Project, both supported by the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health. Integrating data from the three species, the model organism ENCyclopedia Of DNA Elements (modENCODE) Consortium studied how gene expression patterns and regulatory proteins that help determine cell fate often share common features. Investigators also detailed the similar ways in which the three species use protein packaging to compact DNA into the cell nucleus and to regulate genome function by controlling access to DNA. Launched in 2007, the goal of modENCODE is to create a comprehensive catalog of functional elements in the fruit fly and roundworm genomes for use by the research community. Such elements include genes that code for proteins, non-protein-coding genes and regulatory elements that control gene expression. The current work builds on initial catalogs published in 2010. The modENCODE projects complement the work being done by the ENCyclopedia Of DNA Elements (ENCODE) Project, which is building a comprehensive catalog of functional elements in the human and mouse genomes. “The modENCODE investigators have provided a valuable resource for researchers worldwide,” said NHGRI Director Eric Green, M.D., Ph.D. “The insights gained about the workings of model organisms’ genomes greatly help to inform our understanding of human biology.”
World next door
Nine theories of the multiverse promise everything and more. But if reality is so vast and varied, where do we fit in?
Our understanding of the fundamental nature of reality is changing faster than ever before. Gigantic observatories such as the Hubble Space Telescope and the Very Large Telescope on the Paranal Mountain in Chile are probing the furthest reaches of the cosmos. Meanwhile, with their feet firmly on the ground, leviathan atom-smashers such as the Large Hadron Collider (LHC) under the Franco-Swiss border are busy untangling the riddles of the tiny quantum world. Myriad discoveries are flowing from these magnificent machines. You may have seen Hubble’s extraordinary pictures. You will probably have heard of the ‘exoplanets’, worlds orbiting alien suns, and you will almost certainly have heard about the Higgs Boson, the particle that imbues all others with mass, which the LHC found this year. But you probably won’t know that (if their findings are taken to their logical conclusion) these machines have also detected hints that Elvis lives, or that out there, among the flaming stars and planets, are unicorns, actual unicorns with horns on their noses. There’s even weirder stuff, too: devils and demons; gods and nymphs; places where Hitler won the Second World War, or where there was no war at all. Places where the most outlandish fantasies come true. A weirdiverse, if you will. Most bizarre of all, scientists are now seriously discussing the possibility that our universe is a fake, a thing of smoke and mirrors. All this, and more, is the stuff of the multiverse, the great roller-coaster rewriting of reality that has overturned conventional cosmology in the last decade or two. The multiverse hypothesis is the idea that what we see in the night sky is just an infinitesimally tiny sliver of a much, much grander reality, hitherto invisible. The idea has become so mainstream that it is now quite hard to find a cosmologist who thinks there’s nothing in it. This isn’t the world of the mystics, the pointy-hat brigade who see the Age of Aquarius in every Hubble image. On the contrary, the multiverse is the creature of Astronomers Royal and tenured professors at Cambridge and Cornell. (via Michael Hanlon – On multiverses)
read of the day: War in the womb
A ferocious biological struggle between mother and baby belies any sentimental ideas we might have about pregnancy
What sight could be more moving than a mother nursing her baby? What better icon could one find for love, intimacy and boundless giving? There’s a reason why the Madonna and Child became one of the world’s great religious symbols. To see this spirit of maternal generosity carried to its logical extreme, consider Diaea ergandros, a species of Australian spider. All summer long, the mother fattens herself on insects so that when winter comes her little ones may suckle the blood from her leg joints. As they drink, she weakens, until the babies swarm over her, inject her with venom and devour her like any other prey. You might suppose such ruthlessness to be unheard-of among mammalian children. You would be wrong. It isn’t that our babies are less ruthless than Diaea ergandros, but that our mothers are less generous. The mammal mother works hard to stop her children from taking more than she is willing to give. The children fight back with manipulation, blackmail and violence. Their ferocity is nowhere more evident than in the womb. This fact sits uncomfortably with some enduring cultural ideas about motherhood. Even today, it is common to hear doctors talking about the uterine lining as the ‘optimal environment’ for nurturing the embryo. But physiology has long cast doubt on this romantic view. The cells of the human endometrium are tightly aligned, creating a fortress-like wall around the inside of the uterus. That barrier is packed with lethal immune cells. As far back as 1903, researchers observed embryos ‘invading’ and ‘digesting’ their way into the uterine lining. In 1914, R W Johnstone described the implantation zone as ‘the ﬁghting line where the conﬂict between the maternal cells and the invading trophoderm takes place’. It was a battlefield ‘strewn with… the dead on both sides’. When scientists tried to gestate mice outside the womb, they expected the embryos to wither, deprived of the surface that had evolved to nurture them. To their shock they found instead that – implanted in the brain, testis or eye of a mouse – the embryo went wild. Placental cells rampaged through surrounding tissues, slaughtering everything in their path as they hunted for arteries to sate their thirst for nutrients. It’s no accident that many of the same genes active in embryonic development have been implicated in cancer. Pregnancy is a lot more like war than we might care to admit.
keep on reading:
(via Pregnancy is a war between mother and child – Suzanne Sadedin – Aeon)
The striking transformation of a caterpillar into a colourful, winged butterfly is one that has captivated scientists for years. The metamorphosis involves the breakdown of most of the caterpillar’s tissues before reassembling to form a butterfly. It therefore seems unlikely that butterflies or moths would remember experiences from their caterpillar days. However, scientists have now established that not only can a moth retain memories formed while it was a caterpillar, but that experiences gained during these early stages can have drastic impacts on adult life.
Memories live long
Moths and butterflies undergo drastic changes throughout their life-cycle, not just in their outward appearance, but also in their diet and overall lifestyle. Metamorphosis occurs within the pupal case. During this period, the larval brain stimulates the release of enzymes which dissolve most of its tissues into their constituent proteins through a process called histolysis. Then a group of specialised cells called histoblasts proceed to reconstruct the broken-down caterpillar body into that of a butterfly or a moth.
A few years ago, Martha Weiss and her group at Georgetown University discovered that aversive memories formed in the tobacco hornworm caterpillar (Manduca sexta) persisted throughout metamorphosis and were retained in adult moths.
Weiss trained caterpillars to avoid the odour of ethyl acetate, a chemical commonly used in nail polish removers. Caterpillars and moths are usually indifferent to the smell of ethyl acetate, but by pairing exposure to the odour with mild electric shocks, the scientists successfully taught these caterpillars to avoid the odour.
When given a choice of air or ethyl acetate, 78% of the caterpillars carefully avoided the odour in favour of air. Then, when adult moths developed from the pupae of trained caterpillars a month later, they continued to show a strong aversion to the smell, with 77% of the moths choosing air over ethyl acetate. Notably, the majority of moths choosing air as adults had also made the same choice as caterpillars, suggesting that individual preferences survived metamorphosis.
Broody octopus keeps record-breaking four-year vigil
For four years and five months, she clung to the rock and guarded her eggs. In a feat that surely made good use of all eight arms, an octopus revealed a new secret of deep sea life when ecologists observed her record-breaking behaviour from a robotic submarine. This doubles the longest brooding time ever seen in the animal kingdom, giving embryos time to develop in the cold. The discovery, published in the journal PLOS One, was made in a canyon 1.4km beneath the Pacific, off California. Dr Bruce Robison led the research at the Monterey Bay Aquarium Research Institute (MBARI). He told BBC News his team had stumbled upon the plucky mother in the days before she settled down and glued her eggs to the rock face. She was heading, slowly, for a known brooding site. By looking at characteristic scars in one of her eight armpits, the team identified the same octopus on the next dive, one month later. (via BBC News - Broody octopus keeps record-breaking four-year vigil)