For tiny spores, there’s no defeating gravity—unless they work together.
The pathogenic fungus Sclerotinia sclerotiorum travels from place to place by shooting its spores up in the air to be carried away, the same way many plants and fungi spread. A single spore, however, can barely get airborne before it falls back to the surface. A species isn’t going to spread far with that kind of flight time, but luckily, this fungus has a solution. It blasts its spores en masse, creating a wind current that helps them all drift away to new homes.
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From Ed Yong:
Right from its entrance, Disneyland is designed to cast an illusion upon its visitors. The first area – Main Street – seems to stretch for miles towards the towering castle in the distance. All of this relies on visual trickery. The castle’s upper bricks and the upper levels of Main Street’s buildings are much smaller than their ground-level counterparts, making everything seem taller. The buildings are also angled towards the castle, which makes Main Street seem longer, building the anticipation of guests.
These techniques are examples of forced perspective, a trick of the eye that makes objects seem bigger or smaller, further or closer than they actually are. These illusions were used by classical architects to make their buildings seem grander, by filmmakers to make humans look like hobbits, and by photographers to create amusing shots. But humans aren’t the only animals to use forced perspective. In the forests of Australia, the male great bowerbird uses the same illusions to woo his mate.
Read the rest of this post at Not Exactly Rocket Science.
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Image: Current Biology / John Endler
From Ed Yong:
Most human men would be appalled at the idea of their mothers helping them to get laid. But then again, we’re hardly as sexually carefree as bonobos. While these apes live in female-led societies, the males also have a strict pecking order. For those at the bottom, mum’s assistance may be the only thing that allows them to father the next generation.
Martin Surbeck from the Max Planck Institute for Evolutionary Anthropology found that bonobo mothers will help to usher their sons into the best spots for meeting females, and they’ll sometimes help their sons in conflicts with other males. Thanks to their help, their sons get more shots at sex than they would otherwise.
Read the rest of this post at Not Exactly Rocket Science.
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Image: iStockphoto
Bird cheaters beware: They’re watching you. Two recently published studies, one in Science and one in Nature, have asked what bird benefits come from remaining faithful–or cheating on the down-low.
Don’t Cheat
Analyzing the breeding habits of 267 bird species, two researchers have found that it may pay for some birds to stay true to their partners.
Cooperative breeders–birds that help raise each others’ young–appear to be more monogamous. Researchers looked at the number of broods with a half brother or sister, the products of a mother bird’s free-loving ways. Cooperative birds’ cheating rate averaged around 12 percent, while noncooperative birds around 23 percent. Also, the most promiscuous cooperative birds appeared to receive less help from other birds in the nest.
These findings support the theories of evolutionary biologist Jacobus Boomsma (who wasn’t involved in this study), who has tried to explain the puzzle of cooperative behavior that doesn’t directly benefit the helpful individual. Boomsma believes that social animals cooperate to raise their relatives’ offspring as a roundabout way to pass on the family genes, but argues that monogomy is a necessary condition for this to work.
[With monogamous pairings] all siblings are equally related to each other and to each parent. Promiscuity, on the other hand, leads to many half-siblings and lowers the relatedness of individuals in a group. [ScienceNOW]
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Girls around the country are starting puberty ever younger, says a new study out in Pediatrics.
Researchers led by Frank Biro studied more than a thousand girls between six and eight years old from New York, Cincinnati, and San Francisco. Their findings: By the age of 7, about 23 percent of black girls, 15 percent of Hispanic girls, and 11 percent of white girls showed enough breast development to be considered pubescent. Those numbers are even more extreme than the findings of a similar 1997 study that seemed to show the age entering puberty was dropping fast.
Says Biro:
“In 1997, people said, ‘That can’t be right; there must be something wrong with the study’. But the average age is going down even further” [Los Angeles Times].
The starkness of Biro’s statistics has drawn plenty of attention. But just what it means is a difficult question, because there’s no “ideal” age for entering puberty.
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Let’s say you’re a peat moss plant. Since you’re stuck in one place, and it’s low to the ground where there’s little wind or air turbulence, you have to find a way to shoot your spores way up into the air where they can be dispersed.
In reality, mosses have conquered this problem by shooting their spores into the sky at speeds of greater than 30 meters (nearly 100 feet) per second. Their spherical capsules containing the spores deform inward until the pressure forces a ferocious explosion to propel spores at that velocity. But even this is not enough—air would slow the spores before they reached a high enough height to get carried away.
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There was a big step forward this week in the struggle to contain the spread of HIV and AIDS in sub-Saharan Africa. Reporting on a three-year study in the journal Science, scientists at the Centre for the Aids Programme of Research in South Africa (CAPRISA) say that a microbicidal gel reduced HIV infection rates in women who used it by 39 percent over the course of the study. It would be the first time such a gel has proven so effective.
The researchers gathered nearly 900 women for the study who were HIV-free but demographically at risk for infection. Half received the gel, half a similar-looking but inactive substance. Among those given the gel, a vaginally-administered substance that contained an antiretroviral medication called tenofovir, infection rate fell by half after a year, and were reduced by 39 percent over two and a half years.
“This is very encouraging,” said Dr. Michel Sidibe, executive director of Unaids, the United Nations AIDS-fighting agency. “It can be controlled by women, and put in 12 hours earlier, and that is empowering. They do not have to ask the man for permission to use it. And the cost of the gel is not high” [The New York Times].
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Dear male reader: Just so you know, your sperm isn’t that different from a sea anemone’s.
Sperm is so vital, a new study in PLoS Genetics found, that one of the genes responsible for it hasn’t changed in 600 million years. Insects, humans, marine invertebrates, other mammals, even fish—the males of all these creatures share a common sperm gene that dates back to before all those animals diverged all those millions of years ago, according to the team led by Eugene Xu.
From an evolutionary point of view, that longevity is simply stunning.
“It’s really surprising because sperm production gets pounded by natural selection,” Xu said. “It tends to change due to strong selective pressures for sperm-specific genes to evolve. There is extra pressure to be a super male to improve reproductive success. This is the one sex-specific element that didn’t change across species. This must be so important that it can’t change” [MSNBC].
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Geneticists have found a way to alter the sexual preference of lab mice. When they bred mice that had one gene deleted, the females declined male companions and preferred instead to court other females, according to a study published yesterday in BMC Genetics. But whether these results have any implications for humans is still far from clear.
Chankyu Park and his team at the Korea Advanced Institute of Science and Technology deleted the female’s fucose mutarotase gene and, as a result, changed the brain’s exposure to enzymes that control brain development.
The gene, fucose mutarotase (FucM), is responsible for the release of an enzyme by the same name, and seems to cause developmental changes in brain regions that control reproductive behaviors. The mice without the enzyme would refuse to let males mount them, and instead tried to copulate with other females. [AOL News]
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Teamwork: That’s what it takes to get lucky (if you’re a certain kind of firefly).
Suppose you’re a single male firefly, fluttering about on a muggy night. You flash your bioluminescent signal to try to catch a lady’s attention, but how is she going to pick out your blip from all the other points of light ablaze when various species of firefly zoom around? About 1 percent of firefly species have figured out how to beat the noise: They team up and flash their lights in an unmissable, synchronous signal. And in a study in this week’s Science, researchers unlocked the inner workings of this sexual back-and-forth.
Biologists had long known about the synchronous flashing, but had not tested the idea that each species has its own rhythm—its own signal to complete the optical call-and-response between male and female.
To do this, Andrew Moiseff of the University of Connecticut in Storrs and Jonathan Copeland at the State University of New York at Stony Brook turned to LEDs. They put female synchronous fireflies (Photinus carolinus) in a Petri dish surrounded by green LEDs, and flashed the lights in the same pattern used by male fireflies. The females responded with their signature pattern 82 per cent of the time – but only if the LEDs were synchronised. When the lights did not flash in unison, female response dropped to 10 per cent or less [New Scientist].
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Twelve years have passed since Pfizer’s little blue pill for erectile dysfunction, Viagra, hit the market. The pill became so popular and ubiquitous that subsequent attempts by drug companies to make a libido-booster for women invariably drew the moniker “female Viagra.” Those attempts have failed, but today the Food and Drug Administration is considering approval for a new contender—a drug that has stirred up plenty of controversy.
The drug is called flibanserin, and the company is a German one, Boehringer Ingelheim. The first problem with evaluating the daily oral pill is figuring out whether it really has an effect that appears in trials.
The flibanserin data involved about 2,400 women treated with either flibanserin or a placebo for about six months. The agency said the two groups showed an increase in their number of sexually “satisfying” events but didn’t show a boost in a sexual-desire score. The “overall response rate… is not particularly compelling,” the FDA said, even though many of the differences in response rates between the two groups were statistically significant [Wall Street Journal].
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“There are lions and cheetahs and leopards out there, my dear. You’d be better off staying here with me.”
This is how male topi antelope lie for sex.
The area of Kenya where they live, Masai Mara National Reserve, is indeed filled with large predators that find antelopes to be just delicious, and so the topi have developed warning calls that they sound when it’s time to scurry away or else be eaten. But, according to an American Naturalist study, the devious topi males have figured out how to use their calls to fake the threat of immediate danger and keep females around, according to research leader Jakob Bro-Jørgensen.
From February to March, male topi hold small territories through which receptive females pass to assess each male’s mating potential. The authors noticed that, while a female in estrus was on a male’s territory, the male would sometimes emit alarm calls, even in the complete absence of a predator. These false alarms are acoustically indistinguishable from true alarm snorts [Ars Technica].
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Charles Darwin may have been right in worrying that the ill health that plagued his family were a result of inbreeding. Darwin didn’t only marry his first cousin, Emma Wedgwood–in fact, the Darwins and the Wedgwoods made a habit of intermarrying (Darwin’s maternal grandparents were also third cousins). Now a new study, which crunched the numbers on first-cousin marriages over four generations of the two dynasties, suggests that his children had an elevated risk of health problems.
The degree of inbreeding among Darwin’s children, while not excessive, was enough to increase the risk of recessive diseases — ones that occur if a harmful version of a gene is inherited from both parents. Three of his 10 children died before age 10 — 2 of bacterial diseases. Childhood mortality from bacterial infections is associated with inbreeding. So, too, is infertility, and three of Darwin’s children who had long marriages left no children [The New York Times].
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The good news: By combining the DNA of parents with genetic material from a third person, scientists might have developed a way for women with rare genetic disorders to have healthy children. The bad news: The ethical complications involved are so messy that it might be a long time coming.
The researchers outline their work in a study in this week’s Nature. On the surface, the idea is fairly simple. They took the nuclei out of the father’s sperm and the mother’s egg, and transplanted them into a donor’s egg cell that had its nucleus removed, but whose mitochondria remained in the cell’s cytoplasm. What you get is the genetics of both parents, plus the mitochondrial DNA of the host. This technique was pioneered in monkeys last summer, but researchers have now done a proof-of-principle study with human cells.
Mitochondria are often called cellular power plants, because they provide most of the cell’s energy. They also contain their own batch of so-called mitochondrial DNA that can, when mutated, give rise to disease. “What we’ve done is like changing the battery on a laptop,” said lead author Professor Doug Turnbull. “The energy supply now works properly, but none of the information on the hard drive has been changed. A child born using this method would have correctly functioning mitochondria, but in every other respect would get all their genetic information from their father and mother” [BBC News].
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Life: Ain’t it grand?
That seems to have been the starting point for the new nature documentary series LIFE, which spotlights some of the planet’s most gloriously unusual critters. The series, which airs on Sunday evenings on the Discovery Channel, presents animals that belong in the evolution hall of fame. Many have developed remarkable tricks to survive in inhospitable environments, while others have developed fascinating mating rituals that ensure that the fittest individuals pass on their genes, generation after generation.
Click through the gallery for some of our favorite hall-of-famers from the show.
A Restless Trail-Runner
Size does matter, especially for the tiny rufous sengi, an “elephant shrew” whose small size and constant movement makes it hungry—all the time! But movement in a forest full of predators is dangerous, so the sengi devised a clever method to forage for food.
The tiny mammal constructs a series of neatly cleared trails between its regular feeding spots and memorizes their details. Then it launches itself on a trail patrol at breakneck speed, stopping only to check for tasty insects and to clear the trail of any debris. A single twig can be fatal, so the sengi spends up to 40 percent of its time running the trails and clearing away obstacles.
