How does a sperm swim? While microscopes have captured the images of plenty of sperm before, it’s tough to track the motion of these wriggling cells in three dimensions. So scientists devised a new imaging method. They hit a sample of about 1,500 sperm with two different colored light sources oriented at a 45-degree angle. The different colors cast different shadows when they hit the cells, which allowed the researchers to reconstruct each sperm’s motion.
Ever since last month’s China International Medical Equipment Fair in Shenzhen, China, a curious video (above) has been spreading across the blogosphere. The gadget in question is apparently an automatic sperm collector, an all-in-one machine into which men can donate sperm (hands-free). The video treats the entire subject in a rather ridiculous manner, raising two questions: How does this gadget actually work? And does anyone actually use them?
Today, there are in fact several companies selling automatic sperm collectors on the internet (here, here, and here, for example). Your average sperm-collecting gadget consists of a kiosk with a monitor that provides stimulating visuals (!), complimented by sounds (!!). A little lower is a “semen-collection sheath,” which purportedly simulates the feel and movement of a vagina. Read More
Flashy tits equals stronger sperm–at least in the bird world.
A recent study of the birds known as great tits, by evolutionary ecologist Fabrice Helfenstein at the University of Bern, Switzerland, found that the more colorful and bright a male tit’s plumage, the stronger the bird’s sperm is.
The study, published in Ecology Letters, explains that the plumage of some birds contains carotenoids–important antioxidants that can help the bird combat cellular damage caused by stress from predators or feeding babies. A higher amount of carotenoids also results in intensely colored plumage in males, signaling the bird’s increased capacity to ward off stress and preserve its sperm from damage.
As you’ve probably heard, a man’s testicles hang down because sperm are hyper-sensitive to temperature and need to be a little cooler than the inside of the body. But isn’t there more to it than that?
Oh, definitely yes, says research psychologist Jesse Bering, writing for Scientific American. Bering goes on at great length in his analysis of testicular location. Sure, he argues, the temperature part makes sense. But why would natural selection, which so rewards passing on your genes, put a man’s means of passing on those genes in such a terribly exposed place on his body?
Bering’s lengthy account of gonad geography, and the studies trying to explain it, includes some real gems:
One of the more fanciful accounts–and one ultimately discarded by the authors–is that scrotal testicles evolved in the same spirit as peacock feathers. That is to say, given the enormous disadvantage of having your entire genetic potential contained in a thin satchel of unprotected, delicate flesh and swinging several millimeters away from the rest of your body, perhaps scrotal testicles evolved as a sort of ornamental display communicating the genetic quality of the male.
Oh, and this, on how a man’s cremasteric muscle works to keep his sperm at an optimal temperature by contracting and drawing the testicles up on a cold day and relaxing when it’s hot:
[That's] why it’s generally inadvisable for men to wear tight-fitting jeans or especially snug “tighty whities”–under these restrictive conditions the testicles are shoved up against the body and artificially warmed so that the cremasteric muscle cannot do its job properly. Another reason not to wear these things is that it’s no longer 1988.
In all seriousness, there’s nothing Discoblog values more than analysis of the silly… other than over-analysis of the silly. If you haven’t had your fill of scrotal hypotheses, check out the rest of Bering’s post.
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Strangely enough, it makes sense: A study of red junglefowl, a close relative of chickens, found that males can “adjust the speed and effectiveness of their sperm by allocating more or less seminal fluid to copulations.” The determining factor in this remarkable change of speed is how attractive the male finds the female. According to Discovery News (not to be confused with DISCOVER):
The study…adds to the growing body of evidence that males throughout many promiscuous species in the animal kingdom, including humans, can mate with many females, but chances of fertilization are greater when the female is deemed to be attractive.
Desirable female red junglefowl are easy to identify.
“Female attractiveness is determined by the expression of a sexual ornament — the comb — which is phenotypically and genetically correlated to the number and mass of eggs females lay,” according to study co-authors Charlie Cornwallis of the University of Oxford and the Royal Veterinary College’s Emily O’Connor.
To collect their data, the researchers collected natural ejaculates from dominate and subordinate red junglefowl that had just mated with either an “attractive” or “unattractive” female. What the dedicated won’t do for science.
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It’s hard enough for us humans to fight for a mate. But for the now-extinct mussel-like creatures known as ostracods, which lived on Earth about 100 million years ago, “getting in” was only part of the battle.
That’s where giant sperm comes in: Females copulated with multiple males, so it was up for the sperm themselves to duke it out inside of the female’s body. New research based on microfossils of these ancient creatures, led by Dr. Renate Matzke-Karasz in Munich, shows that a male’s sperm may have been even larger than the animal itself. And ostracods aren’t the only animals to produce mega-sperm, according to Reuters:
Giant sperm are still around today. A human sperm, for example, would have to be 40 meters long to measure up against a fruit fly’s. The insect is only a few millimeters in size but can produce 6 cm-long (2.5 inch) coiled sperm.
Now that’s impressive.
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Image: flickr / notsogoodphotography
To play, you tap, shake, and tease the phone to guide an individual sperm down a “fallopian tube” in the race to fertilize an egg. The Mobigem game, now available for $0.99 on iTunes, is designed to demonstrate the stiff competition a sperm faces when it is released into the race for fertilization.
Strange, perhaps—though the title of most promiscuous iPhone app should probably be saved for its use as a personalized sex toy.
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When female fruit flies mate, their immune system responds to the sperm the same way it does to germs. University of California, Santa Barbara evolutionary biologist Andrew Stewart sees the immune system as a battleground, a place where the sexes can compete—a female’s immune system will rev up so it can fight off the proteins in the ejaculate, so she can live longer and have more babies.
But the exact reason for this immune response is still up in the air. It’s possible the male knows that the female has mated with other male flies, and uses the pathogens in his sperm to beat the other males in fertilizing eggs. Regardless, females still pay a heavy price: Most females mate with several partners, even though if they mate just once, their life span is shortened significantly.
But the beetles have it worse, because their mating is so brutal: When a female decides to mate, she repeatedly gets jabbed by the male’s sexual organ, which looks more like a medieval weapon than pleasure tool. But the females put up with the roughness, apparently because they are so thirsty.
Male monarch butterflies have a sixth sense about where their female mates have been. As New Scientist explains, “[s]ensors on the male monarch butterfly’s penis may detect the volume of sperm directly, like the dipstick in a car’s oil tank.” That is, the male butterflies decide how much of their own sperm to deposit based on the female’s mating history.
If the male senses that the “oil tank” is nearly empty, it will inject a concoction of fertile sperm along with a good amount of fake sperm (sperm look-alikes with no nuclei) to discourage future male suitors. If the tank is already full, the male injects a more potent mixture, with a higher concentration of fertile sperm, in order to compete with the the sperm already in the female.
Not too long from now, men will scurry out to the car on the first chilly morning of autumn, jump inside, and enjoy the warm embrace of heated leather seats. But that warm feeling might have an unpleasant side effect—lowering one’s sperm count.
German scientists studied 30 men (subscription required), measuring their scrotal temperature after they had sat in a car seat for 90 minutes. Those who sat in heated seats measured an average of about 99.1 degrees Fahrenheit, up from about 98 degrees for men in plain old unheated seats. The scrotum is located outside the body because sperm production requires a lower temperature, and even a slight raise like the one in this study could interfere with that, the researchers say.