A certain species of dung beetle has been crowned the world’s strongest insect. A male Onthophagus taurus can pull 1,141 times its own body weight — the equivalent of a 70-kilogramme (154-pound) person being able to lift 80 tonnes, the weight of six double-decker buses [AFP]. That power comes in handy not just to roll up a few extra dung-balls, but also to protect mates and stave off potential rivals.

Chronicling the insect’s amazing strength in the journal Proceedings of the Royal Society B, scientists Rob Knell and Leigh Simmons explain that the beetle’s amazing strength is connected to his sex life. These female dung beetles dig tunnels beneath choice pieces of dung in which to lay their eggs. If another male enters a tunnel already occupied by a rival, then the dung beetles duke it out, each male using his immense strength in an attempt to push the other out. Usually, the male that guards the tunnel repeatedly mates with the female inside.

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In leafcutter ants and honeybees, it’s survival of the fittest sperm. Biologist Boris Baer, for a study out this week in Science, investigated these two species because of their peculiar sexual practices: In one day, the queen acquires all the sperm she’ll need to fertilize her eggs over the course of her lifetime. But in the race to be the top genetics-spreader, the males have evolved a dirty trick. Their seminal fluids actually do battle within the female’s reproductive tract.

To test out the idea, Baer and colleagues exposed the sperm of the bee and ant males to their own seminal fluid, and also to that of other males of the same species. The seminal fluid killed more than 50 per cent of the rival sperm within 15 minutes. “The males seemed to use the seminal fluid to harm the sperm,” says Baer [New Scientist]. When the team studied other organisms whose lifestyle didn’t depend on this kind of polyandry, they didn’t see the same effect.

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You are what you eat, and perhaps in some ways, what your mother ate. Back in 2003, Cheryl Rosenfeld’s team found that the diet they fed to pregnant mice caused a “striking variation” in the sex ratios of the offspring: High fat favored males, low fat favored females. Now Rosenfeld has a new study in the Proceedings of the National Academy of Sciences that says the mother’s diet can also affect the very way genes are expressed in the placenta.

To figure this out, Rosenfeld’s team studied the placentas attached to fetal mice 12 and a half days after conception, when the mice were midway through gestation but had yet to produce sex hormones like estrogen or testosterone (those can also alter gene expression, which would have confounded the study). They found that gene activity in the placentas differed significantly depending on whether the mom was fed a high- or low-fat diet. The biggest differences were found when comparing the high- and low-fat placentas linked to female fetal mice, suggesting that placentas nourishing females do a better job of responding to diet—and potentially protecting the fetus from harmful ingredients—than do those connected to males [ScienceNOW]. Specifically, of the 700 genes that they saw behave differently between the sexes, 651 were expressed more in females than males. In all, their study saw changes in the expression of nearly 2,000 genes.

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Sure, creatures that reproduce asexually get to avoid some of the hangups that come with sex, but the strategy brings its own problems. First and foremost, how do you prevent genetic deterioration without the fresh infusion of new genes that results from the mixing of male and female DNA? For the all-female whiptail lizard, the solution is to hedge its bets.

In a study forthcoming in Nature, researcher Peter Baumann found that each whiptail lizard egg cells contains twice the number of chromosomes you’d expect. In the fertilized egg cell of a sexually reproducing lizard species, you’d expect to see much what you see in humans—23 chromosomes from the father and 23 from the mother combining into 46. (Most human cells contain 46 chromosomes, but egg and sperm cells contain only 23, so that they can combine to give an offspring a compete, but genetically new, set of chromosomes.)

But the whiptail eggs instead begin with two identical copies of each of their mother’s chromosomes, for a total of 92. Those chromosomes then pair with their identical duplicates, and after two cell divisions, a mature egg with 46 chromosomes is produced. Since crossing-over during the cell divisions occurs only between pairs of identical chromosomes, the lizard that develops from the unfertilized egg is identical to its mother [The New York Times].

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When it comes to a sperm fertilizing an egg, it all comes down to speed and timing. If the sperm starts swimming at top speed too soon, it will die before it reaches the egg. But if it swims too slowly then it won’t get to its destination in time. Now, scientists have discovered a system in the sperm that acts like a gas pedal, causing the sperm to swim faster as it gets closer to the egg. The findings were published in the February issue of Cell.

Researchers already knew that the speed of a sperm depends on its pH, or its internal acidity levels. The less acidic and more alkline it is, the faster it swims. They also knew that a sperm doesn’t sprint at top speed for its entire trip through a woman’s reproductive tract. It travels relatively slowly for the first part of its journey, and then gets lodged in the sticky folds of the fallopian tubes, resting until another, still unknown signal raises their pH again. This initiates their final race to the egg. “It’s a tough job for a sperm — when it’s deposited it has to travel a long distance to the egg sites,” [said Dejian Ren, who was not involved in the new study]. “This process has been known for many decades, but how it actually happens remained a mystery” [The Scientist].

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There’s been lots of gloating, arguing, and tossing around of cliches like “game-changing” in the wake of a new study on abstinence education and its potential to reduce sexual activity in teens. But the study isn’t exactly what the political forces trumpeting its arrival would like you to believe.

The study appears in the journal Archives of Pediatrics & Adolescent Medicine. In its introduction, study leader John B. Jemmott III concludes that “Theory-based abstinence-only interventions may have an important role in preventing adolescent sexual involvement.”

So what’s actually in the study? Between 2001 and 2004, Jemmott’s team studied 662 African-American middle schoolers in the northeastern United States, who were each paid $20 a session to attend sex-education classes. The kids were randomly assigned to one of several different programs: One program emphasized only abstinence, one both safe sex and abstinence, one just safe sex, and the last was a control group that simply taught healthy living—eating well, exercise, and the like.

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Biologists are a step closer to figuring out the bizarre animals known as bdelloid rotifers, thanks to a new study in Science.

This group of near-microscopic aquatic organisms has lived for tens of millions of years without sex, can withstand blasts of gamma radiation, and if their habitat dries up they can survive for years in a dessicated state. Two years ago, DISCOVER covered the findings that determined how these all-female invertebrates manage to diversify their genes without sex: Their genome breaks apart when they dry up, and as they reassemble when water returns, they pull in new DNA from a host of other beings. Now, the new study says, drying up is also the key to how rotifers avoid parasites that would normally take advantage of their asexual ways.

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As if soccer, wars of incredible length, and the relative worth of wine vs. beer didn’t account for enough disagreements between Britain and France, add another spat to the pile: whether or not the G-spot really exists.

A few weeks ago, a team of scientists from King’s College London joined the ongoing scientific fray by publishing a new study on the much-debated female erogenous zone. It was the biggest to date, involving 1,800 women – all of whom were pairs of identical or non-identical twins. If the G-spot did exist, it said, then genetically identical twins would have been expected to both report having one. However, no such pattern emerged [The Telegraph]. As a result of the study, coauthor Tim Spector said, the study “shows fairly conclusively that the idea of a G-spot is subjective.”

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Researchers from the Imperial College London have a new strategy to combat malaria. The species of mosquito responsible for the spread of malaria in Africa, Anopheles gambiae, only mates once during its life. Putting a stop to their one shot at reproduction should slow down malaria transmission. Anopheles males deploy a glob of proteins and fluids known as a “mating plug” that is essential for ensuring sperm is correctly retained in the female’s sperm storage organ, from where she can fertilise eggs over the course of her lifetime [BBC News]. Without a mating plug, the sperm is not stored and the mosquitoes can’t reproduce. Simply put, the researchers want to prevent male mosquitoes from plugging in the wild.

Anopheles gambiae is the only known species of mosquito to use a mating plug. (However, mating plugs are found in other animals where they prevent multiple males from reproducing with a female. Plug checking mice in research laboratories is a right of passage for many graduate students.) In their research, written up in the journal PLoS Biology, scientists were able to alter the mosquitoes’ genes so that they could no longer form a plug, and thus were unable to reproduce. If this process could be developed for use in the field, perhaps in a spray form like an insecticide, it could “effectively induce sterility in female mosquitoes in the wild,” [study author Flaminia] Catteruccia wrote, offering potential as “one more weapon in the arsenal against malaria” [Reuters]. The WHO is optimistic that their increased funding efforts will produce more technologies similar to this one and that, hopefully, one of them will prove effective.

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Convicted sex offenders living in New York can say goodbye to their social-networking privileges. The state has just booted 3,533 convicted sex offenders off MySpace and Facebook in an attempt to fight online sexual predators.

The purge was the first sweep of registered sex offenders under the Electronic Security and Targeting of Online Predators Act (e-STOP), a 2008 law Attorney General Andrew Cuomo aggressively pushed [New York Daily News]. Those removed from Facebook and MySpace will be referred to their parole officers to determine if anyone violated the terms of their release by being on a social networking site. The e-STOP law bans those sex offenders whose victims were minors from joining social networking sites.

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Scientists have argued before that controlling the earth’s burgeoning population would be one of the most effective ways to slow global warming, since keeping millions of little consumers from being born would reduce the amount of fossil fuel that would have to be burned to keep them warm and fed and happy. Now, an advocacy group that focuses on overpopulation is taking the argument the next step, suggesting that people or companies looking to offset their carbon dioxide emissions should buy contraception that would be distributed in poor countries.

Optimum Population Trust (Opt) stresses that birth control will be provided only to those who have no access to it, and only unwanted births would be avoided. Opt estimates that 80 million pregnancies each year are unwanted. The cost-benefit analysis commissioned by the trust claims that family planning is the cheapest way to reduce carbon emissions [The Guardian].

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Researchers have long sought an answer to burning question of why women live longer on average then men (you know, other than the fact that, as Harry Belafonte puts it, “man smart, woman smarter“). Now a new study in Human Reproduction by Japanese researchers reinforces the argument that the fault lies in men’s genes, a conclusion they reached by taking males completely out of the picture.

They studied mice created with genetic material from two mothers, but no father. This was achieved by manipulating DNA in mouse eggs so the genes behaved like those in sperm [BBC News]. The scientists then implanted those sperm-behaving eggs into female mice, creating 13 “bimaternal” mice. On average, these fatherless mice lived a third longer than those conceived in the usual manner, according to study leader Tomohiro Kono.

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A chemical commonly found in plastics that has recently fallen under intense scrutiny by public health officials has now been linked to impotence. During a five year study, scientists followed 634 male Chinese factory workers who were exposed to high levels of the chemical bisphenol A (BPA) on the job and compared their sexual health with that of similar Chinese factory workers not exposed to BPA. The men handling BPA were four times as likely to suffer from erectile dysfunction and seven times as likely to have difficulty with ejaculation [Washington Post]. The study (PDF), published in the journal Human Reproduction, marks the first time sexual dysfunction has been linked to BPA exposure.

To be fair, the workers were exposed to BPA levels that are 50 times greater than the average U.S. man faces, so scientists can’t say how smaller amounts of the chemical will affect sexual health. However, the chemical resembles the hormone estrogen and that’s fueled worries that even very small amounts of BPA can cause harm [NPR News]. The feds are determined to get to the bottom of the issue and have pledged $30 million to researchers over the next two years in an effort to finally settle the question of whether BPA is safe.

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Our long national nightmare is over: At last, scientists can make rabbit penis spare parts.

In the Proceedings of the National Academy of Sciences, researchers led by Anthony Atala published the results of their successful attempt to engineer new corpora cavernosas, the column of tissue that engorges with blood during male arousal, for male rabbits. Other procedures can partially restore function to a damaged phallus, and Atala’s team has previously shown they could replace a small portion of the tissue (they had up to a 50 percent success rate in rabbits) [Scientific American]. This, however, was the first time they totally replaced corpora cavernosas.

Atala is best known for developing a technique in which cells are taken from an organ and sprayed onto a frame made of collagen, the primary structural protein in animal tissue. The structure is then bathed with growth-stimulating compounds and kept in an oven that duplicates the body’s temperature and chemical composition. Given these starting conditions, natural biology does the rest [Wired.com].

In this experiment, the team surgically removed the corpora cavernosas of 12 rabbits, and replaced them with new “scaffolds” built through this technique. The tissue took hold, and copulation ensued at stereotypical rabbit pace. Every one of the revitalized dozen attempted to mate within a minute of being introduced to females; four became fathers.

The Wake Forest research contains the standard caveat: No, the technique isn’t ready for humans yet. But when it is, look out. Such methods could potentially aid men who just want to enhance their normal penises, rather than repairing any damage. “Our intent and the goal of our work is to provide a solution for men who need penile erectile tissue for medical reasons…. Of course, you cannot control how the technology is used in terms of what patients want” [LiveScience], says Atala.

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Image: flickr/Gidzy

Before one species of jumping spider, known as Evarcha culicivora, goes trolling for a mate, it firsts look to feast on blood-fattened mosquitoes. What happens next seems like something out of a bad video game: The delicacy gives the spider a special power–a sweet smell that the opposite sex finds irresistible.

In a new study, which will be published in the Proceedings of the National Academy of Sciences, researchers exposed E. culicivora specimens to the odors of others raised on blood-fed female mosquitoes and on three other diets: sugar-fed females, males and lake flies…. [The] tested spiders of both sexes were most strongly attracted to the odor of spiders reared on blood-fed female mosquitoes. But the attraction was only for spiders of the opposite sex [The New York Times].  Spiders would hang around blood-fattened spiders of the opposite sex four times longer than they would linger around those fed on another diet. The blood perfume effect might only be triggered by a gender specific hormone, the researchers suggest.

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