I’m excited to announce that my Friday Weird Science guest post for Neurotic Physiology was chosen for publication in The Open Lab 2011! For those unfamiliar with The Open Lab series, it is an annual anthology of the best writing on science blogs.

A note from Sci: The authors took the opportunity in the manuscript to thank their hardworking, and probably long suffering, medical illustrator. Yes, Matthew Timberlake, our hats are off. How we do thank YOU. You are, in your own way, a Real Man of Genius (TM)

Men, let’s talk about that space between your testicles and your anus (taint anus, taint balls – Sci). The length of your member doesn’t really have a whole lot to do with your reproductive fitness, but the length of your taint does. It’s time to put away the rulers and whip out the digital calipers!

A new study came out in PLoS ONE earlier this week, claiming to be the first assessment of anogenital distance in adult men, as well as the first examination of the relationship between anogenital distance and a man’s fertility. I hate to break it to the researchers from Baylor College of Medicine and Stanford University School of Medicine, but you are not the first. A VERY similar study came out two months ago in Environmental Health Perspectives, which Sci so awesomely blogged. As Sci mentioned, anogenital distance is used to sex animals– shorter for females, longer for males. Anogenital distance has also been studied in human infants, mirroring what we know to be true in the animal world (which makes sense, because we are animals)…but no one had studied this in adults up until recently, which leads us back to the sudden interest in measuring men’s taints.

Eisenberg ML, Hsieh MH, Walters RC, Krasnow R, Lipshultz LI, 2011 The Relationship between Anogenital Distance, Fatherhood, and Fertility in Adult Men. PLoS ONE 6(5): e18973.

Why do we care how long a man’s taint is, anyway? Well, because in the past half century there has been a reported decline in semen quality and male births with an increased rate in male genital abnormalities and testicular cancer….and no one likes cancer, or malformed genitals, or weak semen. Previous studies have shown that in addition to reduced anogenital distance, rodents exposed to certain phthalates (these are special chemicals added to plastics to increase flexibility and durability – Sci) had altered testicular size and Sertoli cell function, cells which nurture the developing sperm cells. Not only that, rodents exposed to endocrine disruptors during critical gestational windows for genital development saw irreparable alterations to penis length, anogenital distance, and testicular weight.

As I mentioned earlier, this study was fairly similar to the study that Sci blogged–the methodology was slightly different, and since there was some question regarding methodology in the comments on that post, I figure we’d go into the methodology a bit here. In this study, eligible patients were recruited from a urology clinic specializing in reproductive medicine. Patients evaluated for infertility that were over the age of 18 were eligible for the study, and a fertile control group was put together with a group of men that had a prior history of paternity. In order to measure their genitals, the men had to get into a frog-legged position. Oh yes, there are pictures:

(Note to self: Do not read papers on anogenital distance and male fertility while sitting in a busy airport such as Logan. You will unknowingly stumble upon said diagram while surrounded by people.)

How does one get ready for measurement anyway? Well first you lay on your back, and then touch the soles of your feet together, making sure to keep your feet 12 to 18 inches away from your butt. Oh, and you may want to get a Brazilian wax first. Someone is going to have to get all up in your business, and I’m sure they’d appreciate a clean work surface. Once ready for measuring, someone will take a pair of digital calipers to you, and measure from the back of the balls to the anus, which these researchers thought to be a more comfortable, reliable and reproducible measurement than measuring from the base of the penis (Though they don’t say what it’s MORE reliable than…A ruler? Bending over and spreading? – Sci). Penis length was taken as well, and testicular volume was estimated by one examiner (lucky man) who had the room at a balmy 78 to 80 degrees Farenheit, because…well….we all know what happens to the boys when its cold out.

(I use this photo every time I possibly get the chance-Sci)

All patients also had two semen analyses performed, and semen analyses were performed manually within an hour of collection. I’m going to assume that the semen samples were also OBTAINED manually, and not with a hands-free, semen-collecting robot (though they are becoming more popular! Coming soon to an artificial insemination clinic near you! – Sci).

The volume, density (millions of little swimmers per milliliter), and motility were recorded and multiplied to determine the total motile sperm count. Hormone assays were also processed for testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) (all of these are hormones which influence fertility in both men and women- Sci). Finally, statistical analyses were performed, including adjustments for age, race, FSH and BMI.

Most of the men in the study were white males (64%), but even when the the results were broken down by race, the length o’ taint differences between fathers and infertile men remained stable, with infertile, childless men having a significantly shorter anogenital distance when compared to fathers. Infertile men also had shorter stretched penis lengths and total testicular volumes than fertile men. All genital measurements seem to be correlated to each other, but those in the know can’t stress enough: CORRELATION DOES NOT EQUAL CAUSATION. Semen volume was similar in both fertile and infertile men, but the sperm density, motility and total mobile sperm count were significantly lower for infertile men. In both the unadjusted and adjusted models, anogenital distance and testicular volume were significantly correlated with total motile sperm count and sperm density, and sperm destiny and total motile sperm count increased with an increase in anogenital distance. For every 1 cm increase in taint, add another 4.3 million little swimmers per milliliter and the total motile sperm count increases by 6 million. There wasn’t any significant correlation seen between penis length and sperm count, which goes back to my opening statement — PUT AWAY YOUR RULERS! Women will not judge your marriage and fatherhood potential on the length of your penis…instead, they will base it upon your intelligence, your wit, your dashing good looks….and the length of your taint.

Eisenberg, M., Hsieh, M., Walters, R., Krasnow, R., & Lipshultz, L. (2011). The Relationship between Anogenital Distance, Fatherhood, and Fertility in Adult Men PLoS ONE, 6 (5) DOI: 10.1371/journal.pone.0018973

Zombies.  You’ve seen them in the movies– creatures devoid of consciousness and self-awareness, but able to move and respond to to the environment around them.  No longer in control of theirown bodies or minds, the undead are merely a vehicle for a vicious brain infection that wants one thing, and one thing alone—-BRAIIIIIIINS!  Or in the case of zombie ants, a death grip on leaf veins in the rainforest understory.

Zombie ants may look like ants, but what they really represent is a fungal genome expressing fungal behavior through the body of an ant.  This is pretty much the case with any manipulating parasites- they change or manipulate the behavior of their hosts, eliciting behaviors that ensure the life cycle of the parasite continues.  For instance, salt marsh killifish serve as a second intermediate host to Euhaplorchis californiensis, which ultimately want to find their way into their final host, egrets.  E. californiensis encysts on the brain of the killifish, and cause it to exhibit conspicuous swimming behaviors, making the fish surface, jerk, shimmer and contort to maximize the chance that the egret notices and eats the infected killifish.  Voila!  Parasite is now where it is supposed to be, inside the bird.  The same sort of thing happens with Toxoplasma gondii. Ultimately the parasitic protozoan wants to be inside a cat, so what does it do?  It takes over the brain of rats and mice, and makes them drawn to, rather than fearful of the scent of cats.  That’s right…the little buggers run straight towards the cats, ensuring that they become a tasty snack for kitty.  I digress…back to the zombie ants!!!

The ants in question are Camponotus leonardi, a tropical canopy-dwelling carpenter ant from Thailand.  They live pretty routine lives, rarely descending to the canopy floor, and only traveling along well-defined paths on those rare occasions.  When infected by the parasitic fungus Ophiocordyceps unilateralis, all of that changes– random wanderings like a drunk unable to find their way home, and repeated convulsions that make the ants fall to the canopy floor, ensuring that they remain in the understory and  attach themselves to leaves low to the ground.

At solar noon, the fungus synchronizes ant behavior, forcing the zombie ants to bite the main vein on the underside of the leaf.  At that final moment,  when the ant is under fungal control and biting into the leaf vein, its head is filled with fungal cells, and its mandibular muscles are atrophied.  The multiplying fungal cells in  the ant’s head cause fibers within the muscles that open and close the ant’s mandibles to become detached, resulting in lock-jaw, which ensures that the ant will remain attached to the leaf after death.

The death grip of the zombie ants seem to have no purpose other than to facilitate fungal reproduction, which is only possible after the growth of a large stalk from the back of the ant’s head, followed by the release of spores which can then be picked up by another worker ant.  The location of death in the humid understory is adaptive for the fungus, because it provides optimal conditions reproduction to occur.  Inevitably the ant dies from the fungus, and it is necessary that this happens outside of the colony because ants quickly remove dead nest-mates, and that would not allow enough time for stalk growth and the release of spores.

The synchronization of the death grip suggests either a direct solar cue or an indirect via correlated temperature or humidity, and warrants further study  to determine the neurobiological and molecular mechanisms behind such adaptations.  Fungi are well known to have clock genes useful in synchronizing activity.

Perhaps these poor ants didn’t remember the rules.  They didn’t do their cardio.  They didn’t limber up.  They forgot the double tap.  But most of all, they forgot to get in the good graces of Ed Yong, who is someone you want to have on your side in the event of a zombie invasion.

David P Hughes, Sandra Andersen, Nigel L Hywel-Jones, Winanda Himaman, Johan Billen, & Jacobus J Boomsma (2011). Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection BMC Ecology, 11 (13) : doi:10.1186/1472-6785-11-13

Images are from Wikimedia Commons.

The spread and current range of the cane toad in Australia.

The cane toad (Bufo marinus) was introduced to Australia in what was another failed attempt at biological control.  The Bureau of Sugar Experiment Stations brought over the first cane toads from Hawaii in June of 1935 in an effort to control the cane beetle, which was destroying the sugar cane crops of northern Queensland.  About  100 cane toads were released in August of that year in northern Queensland, but the little buggers multiplied like crazy and today they number over 200 million and have spread as far as New South Wales and the Northern Territory.  One reason they have been able to multiply so successfully is that they are highly toxic, and are toxic at all life stages.  As a result, cane toads have few predators in Australia. Their rapidly spreading invasion has done serious ecological damage — a preliminary risk assessment of cane toads in Kakadu National Park stated that the predation of the cane toad by native wildlife is the greatest risk to biodiversity.

Notice I said few predators.  Although many snakes in Australia are unable to survive the cane toad’s toxins, one native species- the keelback snake (Tropidonophis mairii), is relatively resistant to the deadly toad toxins and remains common in toad-infested areas.  The toad’s toxins have minimal effects on the keelback snake, but the snake still prefers eating native frogs to the invasive cane toad.  Is the keelback’s ability to coexist with toads a result of its ancestral Asian origins, or the result of rapid evolution since the toads’ arrival– and is it’s preference for frogs vs toads an innate or learned behavior?  That’s what a few Australian scientists were hoping to find out.

Image from jcu.edu.au

In order to assess whether or not the keelback’s feeding preference was innate, the scientists looked at two populations of snakes– one in Townsville, where keelbacks and cane toads have lived together for over 60 years, and the other in Darwin, where the snakes and toads have lived together less than four years.  In one experiment, naive snakes were offered a choice of frog or toad for dinner, and the results were recorded.  In the second feeding behavior experiment, the snakes that co-habitated with toads for a long time were tested as to whether or not feeding behavior was learned by being split into two groups- toad-naive and toad-experienced.  The snakes were fed four meals of experimental treatments, followed by a fifth meal to see how prior exposure to toads influenced the snake’s feeding response.  The toad-naive snakes were offered native frogs for their first four meals, and the toad-experienced snakes were offered frogs and cane toads in an alternating sequence.  For the fifth meal, all of the snakes were offered a cane toad.  The final experiment tested toad-naive and toad-experienced snakes for the physiological tolerance to toad toxins by giving the snakes a dose of toad toxin and seeing how it affected the snakes’ performance as they small around a small pool.

The researchers found that being toad-experienced did not affect the keelback’s tolerance to toxins and that prior experience with toads did not significantly affect the tendency of a young keelback snake to consume a toad, showing that  learning plays little or no role in the keelback’s aversion to toads.  The answer as to why keelback snakes are better able to deal with cane toads than the counterparts lies in the species’ biogeographic origin.  In Asia, keelbacks would have encountered Asian toads, something that Australian snakes would not have experienced, since Australia has no native toads.  These previous encounters between snakes and toads during the Pleistoscene and Miocene would have allowed the keelback to evolve their physiological tolerance to toad toxin, which enabled the current-day keelbacks to be better suited to tolerate the toxins of American toads, since the toxins are similar to those of Asian toads.  The snakes’ aversion to cane toads as prey, and their physiological tolerance to the cane toad’s toxins are pre-existing adaptations from the keelback’s ancestral Asian origins, rather than the result of the rapid evolution of adaptations since the toad’s arrival to Australia.

Llewelyn, J., Phillips, B., Brown, G., Schwarzkopf, L., Alford, R., & Shine, R. (2010). Adaptation or preadaptation: why are keelback snakes (Tropidonophis mairii) less vulnerable to invasive cane toads (Bufo marinus) than are other Australian snakes? Evolutionary Ecology DOI: 10.1007/s10682-010-9369-2

This post is a submission in a contest held by NESCent, in which two winners will receive a travel stipend to attend ScienceOnline2011.

Just who exactly benefits from copulatory plugs, anyway?  Mating plugs have been documented in a broad range of animal groups, including insects, arachnids, reptiles and rodents and range from a gelatinous substance in bees and nematodes, to a more solid, coagulated protein mixture in primates, or even the whole appendage breaking off in the vagina.  These plugs all act like a cork in a wine bottle, keeping the contents inside- in this case, sperm- and prevent the female from being able to mate with any other suitors.  The one thing that binds all the various compositions of copulatory plugs is the belief that copulatory plugs are exclusively beneficial to the male.

A new study on nematode worms by researchers at the University of Teubingen, Germany is shaking that assumption, indicating that copulatory plugs may be beneficial for the female as well.  The study, published in the journal Frontiers in Zoology, found that in the nematode worm Caenorhabditis remanei, the plug acts as a form of ‘gift’ as opposed to preventing the females from mating again as previously thought.  And what female doesn’t like a gift after sex?

The copulatory plug probably evolved under sperm competition conditions, as a way to limit males’ competition with one another- blocking their competitor’s sperm and ensuring their fertilization of the egg, allowing them to pass on their genetic material.  The plug may not be as effective at this function, as the presence of a mating plug did not hinder how many times the female mated, or how attractive she was to males. However, it did have a positive effect on egg production and number of offspring, with plugged females producing an average of 29 percent more eggs and offspring than their unplugged counterparts in the study.  Nadine Timmermeyer, lead author of the study, said, “We found that plugging has a significant positive effect on egg production, suggesting that plugs may represent a beneficial act of a male towards its female partner rather than a competitive act between males.”

Discussing possible ways that such a seal may benefit both males and females, Timmermeyer said, “A plug may act as a seal, keeping sperm inside the female and preventing the entry of harmful pathogens. It may also contain substances that stimulate the female, or that have nutritious or antimicrobial properties.”  These worms have one thing right- if you’re going to have sex, shouldn’t it be beneficial for both?

Timmermeyer, N., Gerlach, T., Guempel, C., Knoche, J., Pfann, J., Schliessmann, D., & Michiels, N. (2010). The function of copulatory plugs in Caenorhabditis remanei: hints for female benefits Frontiers in Zoology, 7 (1) DOI: 10.1186/1742-9994-7-28

For many, marriage is the ultimate sign of commitment.  Yet many Americans are still not able to marry.  A new study by researchers at North Carolina State University finds that gay and lesbian couples are forming long-term, committed relationships, even in the absence of marriage rights.

The study, published in the Journal of Family Issues, found that the institution of marriage is both more and less important to gay couples than previously believed.  More important in terms of legal rights- such as retirement and healthcare benefits; less important as a sign of commitment.

Forty gays and lesbians in 20 long-term cohabitating couples were interviewed on three research questions:

1. How do long-term same-sex couples retrospectively explain their transition to a committed relationship?
2. For couples who have had a commitment ceremony, what role do marriage and ceremonies play in commitment processes?
3. For couples who have not had a commitment ceremony, how do they view marriage and ceremonies in relation to their union?

For many gay couples, commitment is ambiguous in the absences of major markers such as marriage–it makes it difficult to pinpoint when things first got serious.  Forty percent of the couples surveyed had participated in a commitment or marriage ceremony, but these ceremonies were not commitment-making moments in the relationship.  Rather, the ceremony served as a celebration of a preexisting commitment.

Just last week on my trip to Florida, I was involved in a discussion with some friends on the topic of marriage.  Over and over again, commitment and legal rights kept coming up, and good points for and against marriage kept popping up.  In truth, marriage really is stupid in terms of a sign of commitment.

Don’t get me wrong–I’m not saying I don’t want my big day with the white dress and the flowers, because I do.  What I’m saying is, commitment should be in the eyes of those in the relationship, and not in the eyes of the government.  If it wasn’t for the importance of those legal rights such as shared benefits, then I would say to hell with it, a piece of seagrass around my finger and the promise to love me forever would suffice.  But the sad truth is that legal rights are important, and they ensure the care of your loved ones- both your significant other and your children.  And those rights shouldn’t ever be denied to anyone.

Reczek, C., Elliott, S., & Umberson, D. (2009). Commitment Without Marriage: Union Formation Among Long-Term Same-Sex Couples Journal of Family Issues, 30 (6), 738-756 DOI: 10.1177/0192513X09331574

In the mid 1800s, a rare syndrome appeared for the first time in medical literature.  The case was that of Julia Pastrana, the world’s most famous bearded lady.  A new study, being published in today’s issue of the American Journal of Human Genetics, reveals molecular cues about the origin and development of this rare condition.

Congenital generalized hypertrichosis (CGH) covers a group of conditions characterized by excessive hair growth all over the body, regardless of age, gender or race. Congenital generalized hypertrichosis terminalis (CGHT) with gingival hypertrophy is a subgroup of CGH associated with an excess of dark hair, enlarged gums and distorted facial features, as was the case with Julia Pastrana.

The study, performed by scientists from the Chinese Academy of Medical Sciences, discovered the underlying cause for CGHT, with or without gingival hyperplasia.  High resolution genetic analyses were conducted on several members of three Chinese families with CGHT, and an individual with sporadic CGHT with gingival hyperplasia.  The researchers mapped the location of the gene on a chromosome, and found that genetic defects on chromosome 17q24.2-q24.3 were responsible for CGHT, regardless of whether or not the patient also exhibited gingival hyperplasia.

The three families with CGHT that were studied showed different DNA deletions on the identified chromosome region.  In the individual with a sporadic case of CGHT, the identified chromosome region had a DNA duplication.  These mutations affected four to eight genes in the identified region, establishing CGHT as a genomic disorder.

Sun et al. (2009). Report: Copy-Number Mutations on Chromosome 17q24.2-q24.3 in Congenital
Generalized Hypertrichosis Terminalis with or without Gingival Hyperplasia American Journal of Human Genetics, 84 (6)