Posts Tagged ‘sex’

By Michael Le Page

For many fish, changing sex is a normal part of life. For the first time, we have found out exactly how one of these species – a small cleaner fish called the bluehead wrasse – does it.

Erica Todd at the University of Otago in New Zealand and her colleagues removed some male bluehead wrasse from a few sites on reefs off Key Largo in Florida. This triggers females to change sex. They then caught changing females at regular intervals and looked at what was happening in their bodies down to the level of which genes were turning on or off.

They found that the loss of males makes some females stressed. They become more aggressive and start performing male courtship behaviours.

In individuals that become dominant in a social group, the genes associated with female hormones shut down in a day or two, and their colours begin to change – females of the species are yellow and brown (see above), while the males are green and blue.

At the same time, the egg-producing tissues in their ovaries start to shrink and begin to be replaced by sperm-producing tissues. In just 8 to 10 days, the mature ovaries are transformed into testes, and the fish can mate with females and sire offspring.

Read more: Zoologger: Shrimp plays chicken with its sex change
After around 20 days, the fish have the full male colours and the process is complete. “The bluehead is certainly remarkable for its speed,” says Todd. “Other species do take much longer.”

However, as the fish only live around two or three years, those 20 days are a fair chunk of their lifespan, equivalent to 2 years of a human lifetime.

Around 500 species of fish can change sex, a fact long known to biologists but which got wider attention recently when the Blue Planet II documentary narrated by David Attenborough showed Asian sheepshead wrasse changing sex. It is most common for female fish to turn into males but in some species including clownfish the males turn into females.

In at least one species, the hawkfish found around southern Japan, the females can not only turn into males but also turn back into females again if circumstances require it. For one species of shrimp, there is no need to change back. It starts out male but becomes an hermaphrodite – a phenomenon known as protandric simultaneous hermaphroditism.

Journal reference: Science Advances, DOI: 10.1126/sciadv.aaw7006

https://www.newscientist.com/article/2209254-bluehead-wrasse-fish-switch-from-female-to-male-in-just-20-days/

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Any ad executive will tell you that sex sells. But why? Do sexy images stimulate our biological urges, somehow motivating us to buy products? Or do marketers merely exploit and perpetuate our cultural obsession with sexual imagery? Do people want the beauty, wealth and power celebrities have, and use the products they endorse in the hope of achieving these same qualities?

These explanations are plausible, but my colleagues and I have a new one, based on decades of work comparing the behavior and neurobiology of decision-making in monkeys and people: Our brains have been fine-tuned by evolution to prioritize social information, and this laser focus on others profoundly shapes our decisions.

As early as the 1870s, companies like Pearl Tobacco and later, W. Duke & Sons, employed social advertising, showcasing nude or partially exposed women on posters and trading cards. Although the images had no direct link to the products, sales increased. A century and a half later, it seems impossible to escape sexual imagery in advertising. The same is true for celebrities in marketing campaigns—actors, musicians, athletes, even politicians and business leaders. These celebrities often don’t even use the products they advertise, yet the method still seems to work.

Our brains have circuits specialized for identifying, remembering and inferring the mental states of others so we can predict their behavior and make good decisions. In other words, we’re built to deal with people. But we’re not alone in this connection. Many species of monkeys and apes—our closest living relatives—also live in large, complex, dynamic societies. Behavioral studies show that, like us, these primates identify others, track prior encounters, empathize with friends and relatives, and make inferences about individuals’ mental states.

For people and monkeys alike, it’s important to find a good mate, make powerful allies and avoid potential threats. Paying close attention to social cues can improve these choices. In fact, both men and male monkeys are exquisitely sensitive to indications of female fertility. Men rate ovulating women as more attractive, and tip more for lap dances by fertile women. Similarly, male rhesus macaques prefer images of females with artificially reddened faces and hindquarters, coloration that predicts ovulation and sexual receptivity.

Women and female monkeys are also sensitive to clues about male quality, although what we know about that is based on fewer studies. A woman’s preference shifts toward more masculine faces—broader jaw, wider-set but smaller eyes—during ovulation. Female macaques, when ovulating, tend to mate with higher-ranking males and prefer those with reddened faces caused by a testosterone surge. Other studies found that both people and monkeys pay more attention to high-status individuals and are more likely to follow their gaze.

According to economics, we can quantify how much someone values something—coffee, a magazine—by how much he or she will pay for it. In our latest work, we developed an assessment, dubbed the “pay-per-view” test, to measure subconscious value of visual images. In the experiment, monkeys had the option to forego juice or food for a glimpse at a picture of another monkey. People could choose whether to accept a smaller cash reward to peek at a picture of another individual.

Our findings were striking. Male college students paid slightly more money to view an attractive woman than an unattractive one, losing several dollars during the experiment. Female students were much less motivated to see attractive men. Monkeys of both genders valued sex and status, accepting less food or juice to see images of monkey genitalia and faces of high-status males. In contrast, they required extra food or juice to look at faces of low-status males.

Based on these findings, it’s clear that monkeys and humans value information about sex and status so much that it can replace rewards like food, juice and money. Strong parallels between the two suggest shared brain mechanisms at work.

To test this idea, we used fMRI to scan the brains of male students in two circumstances: one, while they viewed female faces of varying attractiveness, the other while money was either deposited or withdrawn from their study stipend. The sight of attractive faces strongly activated a network of brain areas previously implicated in processing rewards—including the orbitofrontal cortex, ventromedial prefrontal cortex, and medial and ventral striatum—and neural activity increased with increasing attractiveness. The same happened with monetary rewards and losses. We believe this network computes economic “utility,” a person’s internal desire for or satisfaction with a good or service, thought to underlie decisions.

To determine the physiological basis of these signals, we measured individual brain cell activity in monkeys. Some fired strongly when male monkeys chose to see female genitalia, a high-status male face, or a large juice reward, but fired less when they chose low-status faces or small juice rewards. Specific brain cells reacted to images of faces and genitals but not juice, indicating the brain’s reward system possesses dedicated hardware for identifying and prioritizing key social information.

Can these discoveries help explain the power of sex and status in advertising? In theory, ads that associate sex or status with specific brands or products activate the brain mechanisms that prioritize social information, and turning on this switch may bias us toward the product.

To test this idea, we exposed male rhesus macaques to logos of household brands like Nike and Pizza Hut paired with a social image (e.g., female genitalia, high-status male face) or the same image with pixels rearranged to make it unrecognizable but retain the same brightness, contrast, and color, salient cues that could draw attention to a stimulus. Monkeys received a sweet treat for touching the screen after the ad, then had the choice between brands paired with a social image or its scrambled version.

Our advertising campaign was remarkably effective. Monkeys developed preferences for brands linked with sex and status. Both males and females preferred logos paired with sexual cues and the faces of high-status monkeys. And the more often male monkeys saw sexual advertisements, the more they preferred the brands. Sound familiar? Even monkeys, it seems, can be persuaded to choose a brand through social advertising.

Given the nearly identical specializations of brain reward circuits to prioritize social information in monkeys and people, is it any wonder that sex and status sell?

https://blogs.scientificamerican.com/observations/what-monkeys-can-teach-us-about-advertising/


An Amazon molly, Poecilia formosa, an asexual fish species native to Texas that is entirely female.

By Shana Hutchin

Highlights

The Amazon molly has flourished by defying nature’s odds to reproduce asexually, cloning themselves by duping the male fish of another species to waste their germplasm

Females steal the entire genome of their host males, keep it for one generation and then throw it out again

The existence of Amazon mollies back anywhere from 100,000 to 200,000 years ago to a sexual reproduction event involving two different species of fish

Faculty Fellow Dr. Manfred Schartl led the international team that recently sequenced the first Amazon molly fish genome

No species is immune from the suffering of unrequited love, but scientists expect to learn volumes about the biological basis of sex from the newly sequenced genome of an all-female, asexual Texas native – the Amazon molly fish – that has thrived as a master of male manipulation over millennia.

The fresh waters along the Texas-Mexico border serve as home to this evolutionary anomaly – a fish that has flourished by defying nature’s odds to reproduce asexually through a natural form known as parthenogenesis in which growth and development of embryos occurs without fertilization, resulting only in daughters that are true clones of their mothers.

Texas A&M University Hagler Institute for Advanced Study (HIAS) Faculty Fellow Dr. Manfred Schartl led the international team that recently sequenced the first Amazon molly genome and the genomes of the original parental species that created this unique fish in an effort to better understand how its reproduction deviates from the male-female sexual norm and why the Amazon molly as a species has fared so well in the process.

The evolution of sex

The findings from their National Institutes of Health-funded research are published online today (Feb. 12) in the Nature research journal Nature Ecology & Evolution.

“The existence of two sexes, male and female, is one of the oldest and most widespread phenomena in biology,” says Schartl, a world leader in cellular and molecular biology of Xiphophorus model systems including platyfish and swordtails. “Studies on the exceptional case of asexuality helps us to better understand the biological meaning and evolution of sex.”

Animals that reproduce asexually are rare, compared to the overwhelming majority of species that exist as males and females and reproduce sexually. Because it was long thought that vertebrates would not be able to exist in such a way, Schartl says it was a sensation when the Amazon molly was the first asexual vertebrate discovered in 1932.

But even the most independent females occasionally need a male – in the Amazon molly’s case, to kick-start the parthenogenensis process. They seduce males from related sexual species for this service, which Schartl notes lacks the regular benefit for these males, which do not contribute their genes to the next generation.


An Amazon molly (right), caught in action while seducing a male Sailfin molly to steal sperm.

Thriving by cloning

“In essence, mollies repeatedly clone themselves by duping the male fish of another species to waste their germplasm,” Schartl says. “This reminds one of the tribe of female warriors in the Greek mythology, from which their name is derived.”

The team’s research traces the existence of Amazon mollies back anywhere from 100,000 to 200,000 years ago to a sexual reproduction event involving two different species of fish, an Atlantic molly and a Sailfin molly.

“That’s about 500,000 generations if you calculate it out to the present day, which makes them genetically older than humans,” Schartl says. “This is unexpected because asexuals are expected to be at disadvantage compared to their sexual counterparts.”

Schartl notes that one of the theories as to why asexual reproduction is incompatible with a species’ sustainability is the idea that if no new DNA is introduced during reproduction, then harmful gene mutations can accumulate over successive generations, leading to eventual extinction. Another hypothesis states that asexual reproduction is not like sexual reproduction, where the different genomes of the two parents are newly combined and create new genomes with every offspring. Because the absence of recombination in asexuals limits genetic diversity within a species, he says it gets more and more difficult to adapt to changes in the environment.

“Unexpectedly, we did not find the signs of genomic decay as predicted,” Schartl adds. “Our findings suggest that the molly’s thriving existence can be explained by the fact that the fish has a hardy genetic makeup that is often rare in nature and gives the animals some survival benefits.”

Schartl says the hybridization of the Atlantic and Sailfin mollies’ two different species genomes into a new one created a situation well known in the animal and plant breeding world — an artificial hybrid that is bigger, more colorful and capable of generating more and better products than the purebred parents, a phenomenon known as hybrid vigor.

https://today.tamu.edu/2018/02/12/texas-am-biologist-leads-international-team-that-sequences-first-amazon-molly-fish-genome/

By Christopher Ingraham

As acceptance of and usage of marijuana have become more widespread, a whole lot of interesting questions for public health researchers have been raised: How will legal marijuana affect our children? Our jobs? Our relationships?

Or how about our sex lives?

That latter question inspired a research project by Joseph Palamar and his colleagues at New York University. “Since the landscape is changing, and marijuana continues to increase in popularity, research is needed to continue to examine if and how marijuana use may influence risk for unsafe sexual behavior,” they write in the July issue of the journal Archives of Sexual Behavior.

To that end, Mr. Palamar and his colleagues recruited 24 heterosexual adults to take part in a series of in-depth interviews about prior sexual experiences that happened under the influence of either alcohol or marijuana. This was not meant to be a national sample. Rather, the purpose was to obtain a rigorous qualitative assessment of the different effects of alcohol and marijuana on people’s sexual behaviors and to use this as a jumping-off point for future quantitative research.

Here are a few of the observations the researchers drew from the interviews.

1. Beer goggles are real.

Respondents “overwhelmingly reported that alcohol use was more likely to [negatively] affect the partners they chose,” the study found. Both men and women were fairly likely to say that alcohol had the effect of lowering their standards for whom they slept with, in terms of character and appearance. With marijuana, this seemed to be much less of an issue.

“With weed I know who I’m waking up with. With drinking, you don’t know. Once you start drinking, everybody looks good,” a 34-year-old female said.

Marijuana use also was more associated with sex with people the respondents already knew — girlfriends and boyfriends, for instance. But alcohol “was commonly discussed in terms of having sex with strangers [or someone new],” the study found.

2. Drunk sex often leads to regret. Stoned sex typically doesn’t.

“The most commonly reported feeling after sex on alcohol was regret,” the study found. “Both males and females commonly reported that regret, shame, and embarrassment were associated with alcohol use, but this was rarely reported for marijuana.”

“I want to cook the person something to eat [after sex] when I’m high,” one male respondent said. “When I’m drunk, it’s like, ‘I’m out of here.’ Or get away from me.”

These negative emotions are seen as at least partly due to drunk sex being associated more with strangers.

3. Drunk sex can make you sick. Stoned sex can make you distracted.

“Nausea, dizziness, feeling sick [and vomiting], and blacking out were commonly reported to be associated with alcohol use,” the study found. One male said he accidentally fell asleep during sex while drunk. Another told of multiple instances where sex had to be interrupted because “I’ve had to stop and go hurl.”

There were fewer adverse effects reported with marijuana, and these tended to be more mental. One respondent said that marijuana use lessened his motivation to have sex. Another reported that being high distracted her from the experience.

“You’re so high [on marijuana] … you start thinking sex is weird. ‘What is sex?’ ” a female respondent reported.

4. The pleasure is usually better on marijuana.

The study found that “alcohol tended to numb sensations and marijuana tended to enhance sensations.”

“Alcohol tends to be a lot more numb,” a male respondent said. “Everything is sort of blunted and muted, whereas with marijuana it’s intensified.”

This “numbness” was associated with a longer duration of sex while drunk. But that wasn’t necessarily a good thing.

It “sometimes lasts too long,” one female respondent said. “Compared to when you’re high — it feels so great and it might be a little shorter.”

The study found that both men and women reported longer and more intense orgasms on marijuana, with one woman reporting hers were “magnified at least by five times.”

Also, marijuana led to “more tender, slow, and compassionate sexual acts, and to involve more sensation and sensuality than alcohol,” the report found.

5. Drunk sex is riskier overall.

“With regard to sexual risk behavior, the majority of participants felt that alcohol was riskier, sexually, than marijuana,” Mr. Palamar and his colleagues found. People typically said they exercised poorer judgment when drunk than when stoned, and were more likely to black out and forget whom they were with, what they were doing or whether they used protection.

Participants generally didn’t note this type of behavior with marijuana and said that while under its effects, they felt more in control overall. “One participant interestingly pointed out that marijuana use decreased his likelihood of engaging in risk behavior because while high he was too paranoid to give in,” the study found.

There were some take-homes viewed as useful from a public health perspective. First, the findings confirm one thing that numerous other studies have shown: Alcohol use seems to be closely associated with high-risk sexual behavior.

Aside from the link with unprotected sex and the corresponding risk of unexpected pregnancy or sexually transmitted diseases, studies have also drawn disturbing parallels between alcohol use and sexual assault. That link appeared even in the very small sample in Mr. Palamar’s study: One out of the 12 women interviewed reported an instance of sexual assault while under the effects of alcohol.

These negative consequences appear to be less pronounced with marijuana. Research found significantly lower incidences of domestic violence among couples who smoke marijuana, for instance.

http://www.post-gazette.com/news/health/2016/08/08/Serious-researchers-studied-how-sex-is-different-when-you-re-high-vs-when-you-re-drunk/stories/201608080044

Thanks to Michael Moore for bringing this to the It’s Interesting community.

According to a new study, the male brain contains two extra cells that can cause men to seek out sex as a priority, even over food. Female brains do not contain these cells.

The research, conducted by scientists at University College London, may have been carried out on tiny transparent worms, but co-author Professor Scott Emmons has insisted the findings offer an insight into human sex habits.

“Though the work is carried out in a small worm, it nevertheless gives us a perspective that helps us appreciate and possibly understand the variety of human sexuality, sexual orientation, and gender identification,” he said, according to The Telegraph.

“Although we have not looked in humans, it is plausible that the male human brain has types of neurons that the female brain doesn’t, and vice versa. This may change how the two sexes perceive the world and their behavioural priorities.”

The researchers studied the brains and behaviours of Caenorhabditis elegans – small soil-dwelling worms that grow to 1mm long – to draw their conclusions.

The worm species is made up of two sexes: males and hermaphrodites. Scientists consider the latter “modified females” that do not need to have sex in order to reproduce.

Caenorhabditis elegans are often used in studies relevant to human biology and disease as they contain many of the same genes that humans do.

After recently discovering that the male worms contained two extra brain cells, the researchers wanted to find out what impact this could have on their behaviour.

They conditioned the worms in a controlled environment so that they would associate the appearance of salt with starvation.

Over the course of the experiment, the worms began to move away from the salt.

However, when salt was present at the same time as a potential mate, the male worms risked getting close to the salt in order to advance sexually.

In contrast the hermaphrodite worms continued to move away from the salt.

The study, published in the online journal Nature, concludes that male brains may be genetically wired to prioritise sex over food.

This isn’t the first study to suggest men and women’s brains may be wired differently.

In 2013, a study from the University of Pennsylvania found that men generally have more connections within each hemisphere of the brain, while in women the two halves of the brain are much more interlinked.

The scientists concluded that male brains are mainly configured to co-ordinate perception and action, while women’s are more geared up to integrate “heart and mind” thought processes, linking analytical and intuitive reasoning.

http://www.huffingtonpost.co.uk/2015/10/15/male-brain-prioritise-sex-over-food_n_8300240.html

by Peter Mellgard

Back in the 80s there was a student at the Massachusetts Institute of Technology who confessed to a professor that he hadn’t quite figured out “this sex thing,” and preferred to spend time on his computer rather than with girls. For “Anthony,” computers were safer and made more sense; romantic relationships, he said, usually led to him “getting burned in some way.”

Years later, Anthony’s story made a big impression on David Levy, an expert in artificial intelligence, who was amazed that someone as educated as Anthony was developing an emotional attachment to his computer so long ago. Levy decided he wanted to give guys like Anthony a social and sexual alternative to real girls. The answer, he thinks, is sexbots. And he’s not talking about some blow-up doll that doesn’t talk.

Levy predicts that a lot of us, mostly but not exclusively shy guys like Anthony, will be having sex with robots sometime around the 2040s. By then, he says, robots will be so hot, human-like and mind-blowing under the sheets that a lot of people will find them sexually enjoyable. What’s more, Levy believes they will be able to engage and communicate with people in a meaningful, emotional way, so that guys like Anthony won’t need to worry about real girls if they don’t want to.

To give a robot the ability to communicate and provide the kind of emotional satisfaction someone would normally get from a human partner, Levy is improving an award-winning chat program called Do-Much-More that he built a few years ago. His aim is for it to become “a girlfriend or boyfriend chatbot that will be able to conduct amorous conversations with a user,” he told The WorldPost. “I’m trying to simulate the kind of conversation that two lovers might have.”

Levy admits that “this won’t come about instantly.” Eventually he wants his advanced conversation software embedded in a sexbot so that it becomes more than just a sexual plaything — a companion, perhaps. But it won’t be for everyone. “I don’t believe that human-robot relationships are going to replace human-human relationships,” he said.

There will be people, however, Levy said, people like Anthony maybe, for whom a sexbot holds a strong appeal. “I’m hoping to help people,” he said, then elaborated:

People ask me the question, ‘Why is a relationship with a robot better than a relationship with a human?’ And I don’t think that’s the point at all. For millions of people in the world, they can’t make a good relationship with other humans. For them the question is not, ‘Why is a relationship with a robot better?’ For them the question is, would it be better to have a relationship with a robot or no relationship at all?

The future looks bright if you’re into relationships with robots and computers.

Neil McArthur, a professor of philosophy and ethics at the University of Manitoba in Canada, imagines that in 10 to 15 years, “we will have something for which there is great consumer demand and that people are willing to say is a very good and enjoyable sexbot.”

For now, the closest thing we have to a genuine sexbot is the RealDoll. A RealDoll is the most advanced sex doll in the world — a sculpted “work of art,” in the words of Matt McMullen, the founder of the company, Abyss Creations, that makes them. For a few thousand dollars a pop, customers can customize the doll’s hair color, skin tone, eyes, clothing and genitalia (removable, exchangeable, flaccid, hard) — and then wait patiently for a coffin-sized box to arrive in the mail. For some people, that box contains a sexual plaything and an emotional companion that is preferable to a human partner.

“The goal, the fantasy, is to bring her to life,” McMullen told Vanity Fair.

Others already prefer virtual “people” to living humans as emotional partners. Love Plus is a hugely popular game in Japan that is played on a smartphone or Nintendo. Players take imaginary girls on dates, “kiss” them, buy them birthday cakes.

“Well, you know, all I want is someone to say good morning to in the morning and someone to say goodnight to at night,” said one gamer who has been dating one of the imaginary girls for years, according to TIME Magazine.

And there’s Invisible Girlfriend and Invisible Boyfriend, apps that connects you with a real, paid human who will text you so that you can prove you have a girlfriend or boyfriend to nosy relatives or disbelieving buddies. At least one user, a culture critic for the Washington Post, confessed she might actually being in love with the person on the other side who, remember, is being paid to satisfy customers’ desires. They’d never even met.

McArthur and others suspect that there might be people for whom a sexbot is no mere toy but a way to access something — sex — that for one reason or another was previously unattainable.

When it comes to the disabled, McArthur explained, there are two barriers to sexual activity: an external — “they’re not seen as valuable sexual partners” — and an internal anxiety. “Sexbots can give them access to partners. And they are sort of a gateway as well: disabled people could use a sexbot to build confidence and to build a sense of sexuality.”

“When it comes to sex,” he concluded, “more is better.”

It’s a new and emerging technology, but let’s nip in the bud,” Kathleen Richardson, a senior research fellow in the ethics of robotics at De Montfort University in England, told the Washington Post. Richardson released a paper this month titled “The Asymmetrical ‘Relationship’: Parallels Between Prostitution and the Development of Sex Robots.”

“I propose that extending relations of prostitution into machines is neither ethical, nor is it safe,” the paper reads.

And the ethical questions extend beyond machine “prostitution.” RealDoll, the sex doll company, refuses to make child-like dolls or animals. But what if another company does?

“It’s really a legal, moral, societal debate that we need to have about these systems,” said Matthias Scheutz, the director of the human-robot interaction laboratory at Tufts University. “We as a society need to discuss these questions before these products are out there. Because right now, we aren’t.”

If, in the privacy of your own home, you want to have sex with a doll or robot that looks like a 10-year-old boy or virtual children in porn apps, is that wrong? In most though not all countries in the world, it’s illegal to possess child pornography, including when it portrays a virtual person that is “indistinguishable” from a real minor. But some artistic representations of naked children are legal even in the U.S. Is a sexbot art? Is what a person does to a sexbot, no matter what it looks like, a legal question?

Furthermore, the link between viewing child pornography and child abuse crimes is unclear. Studies have been done on people incarcerated for those crimes that found that child pornography fueled the desire to abuse a real child. But another study on self-identified “boy-attracted pedosexual males” found that viewing child pornography acted as a substitute for sexual molestation.

“I think the jury is out on that,” said McArthur. “It depends on an empirical question: Do you think that giving people access to satisfaction of that kind is going to stimulate them to move on to actual contact crimes, or do you think it will provide a release valve?”

Scheutz explained: “People will build all sorts of things. Some people have made arguments that for people who otherwise would be sex offenders, maybe a child-like robot would be a therapeutic thing. Or it could have exactly the opposite effect.”
McArthur is most worried about how sexbots will impact perceptions about gender, body image and human sexual behavior. Sexbots will “promote unattainable body ideals,” he said. Furthermore, “you just aren’t going to make a robot that has a complicated personality and isn’t always in the mood. That’s going to promote a sense that, well, women should be more like an idealized robot personality that is a pliant, sexualized being.”

As sexbots become more popular and better at what they’re built to do, these questions will become more and more important. We, as a society and a species, are opening a door to a new world of sex. Social taboos will be challenged; legal questions will be raised.

And there might be more people — maybe people like Anthony — who realize they don’t need to suffer through a relationship with a human if they don’t want to because a robot provides for their emotional and sexual needs without thinking, contradicting, saying no or asking for much in return.

http://www.huffingtonpost.com/entry/robot-sex_55f979f2e4b0b48f670164e9

Thanks to Dr. Lutter for bringing this to the attention of the It’s Interesting community.

The antechinus is a small, shrewlike marsupial indigenous to Australia and New Guinea. These animals are best known for their odd practice of having sex until it kills them, but what else does their mating behavior entail?

There are currently 15 known species of antechinus (animals in the Antechinus genus) living in the forests and woodlands of Australia and New Guinea, five of which were discovered since 2012, said Andrew Baker, a mammal ecologist at the Queensland University of Technology in Australia and leader of the group that made the discoveries.

Generally speaking, antechinus are loners that stick to themselves until the breeding season nears.

Antechinus breed during the Australian winter, when their food — small vertebrates and invertebrates — is scarce. This timing ensures their babies will be born in the spring, when food is bountiful.

Interestingly, males stop producing sperm before the mating season begins.

It’s not clear how sexually mature males and females find mates, but Baker suspects scent, and pheromones, are involved. And as with many other species, males likely roam longer and wider in search of sex, he said.

Baker also suspects that male-male fighting is probably common among antechinuses. “They have surging testosterone levels that tend to make them very aggressive,” Baker said.

Antechinus don’t bother wasting time with wooing mates or engaging in courtship rituals. Instead, they prefer to get down to business immediately.

In fact, a male has no issue with resorting to ambush mating, during which he will catch hold of a female from behind and mate with her while grabbing the scruff of her neck with his forepaws and biting her neck.

It’s not uncommon to find females with tufts of fur around the neck area missing, Baker said, adding that females are fine with the rough ambush as long as they have an opportunity to mate with other males afterward.

Both male and female antechinus are promiscuous, and will try to mate with numerous partners throughout the breeding period. However, to increase their chances of fathering offspring, males will mate with females for as long as possible.

Scientists have documented antechinus copulation events lasting for 10, 12 and even 14 hours. “That’s intermittent thrusting between just one male and one female,” Baker said. When not thrusting, the male will guard the female, keeping her from getting away (and looking for other mates) and other males from getting to her.

Anetchinus will mate continuously for the entire breeding period, which lasts, on average, about two weeks. This activity takes a toll on the male’s body.

The sustained high levels of testosterone stop the production of cortisol from being turned off, allowing males to burn more sugar, Baker said. “It frees them from the need to feed as often, but the downside is that cortisol in sustained levels is poisonous,” he said.

Over time, the males will start to behave erratically, bleed internally, lose fur, develop sores and ulcers that don’t heal, become blind, and develop high parasite loads as their immune system shuts down. “They are like a blank slate for every parasite and disease going around,” Baker said.

It’s rare for a male to survive the breeding period.

Females, on the other hand, may die of exhaustion after weaning their litter, which have multiple paternities. Less than 50 percent of females make it to their second breeding season, and only a very small percentage make it to their third, Baker said.

http://www.livescience.com/51371-animal-sex-antechinus.html