Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases

Follow us on Facebook or subscribe to our mailing list, to receive news updates. Learn more.

Links 1 - 20 of 2626

Hannah Devlin Science correspondent The brain circuit that causes the sound of a newborn crying to trigger the release of breast milk in mothers has been uncovered by scientists. The study, in mice, gives fresh insights into sophisticated changes that occur in the brain during pregnancy and parenthood. It found that 30 seconds of continuous crying by mouse pups triggered the release of oxytocin, the brain chemical that controls the breast-milk release response in mothers. “Our findings uncover how a crying infant primes its mother’s brain to ready her body for nursing,” said Habon Issa, a graduate student at NYU Langone Health and co-author of the study. “Without such preparation, there can be a delay of several minutes between suckling and milk flow, potentially leading to a frustrated baby and stressed parent.” The study showed that once prompted, the surge of hormones continued for roughly five minutes before tapering off, enabling mouse mothers to feed their young until they were sated or began crying again. The observation that a mother’s breasts can leak milk when they hear a crying baby is not new. But the latest research is the first to identify the brain mechanisms behind what the scientists described as the “wail-to-milk pipeline”, and could pave the way for a better understanding of the challenges of breastfeeding for many women. The findings, published in Nature, showed that when a mouse pup starts crying, sound information travels to an area of its mother’s brain called the posterior intralaminar nucleus of the thalamus (PIL). This sensory hub then sends signals to oxytocin-releasing brain cells (neurons) in another region called the hypothalamus. Most of the time these hypothalamus neurons are “locked down” to prevent false alarms and wasted milk. However, after 30 seconds of continuous crying, signals from the PIL built up and overpowered the in-built inhibitory mechanism, setting off oxytocin release. © 2023 Guardian News & Media Limited

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 28919 - Posted: 09.21.2023

By Sarah Lyall The author Cat Bohannon was a preteen in Atlanta in the 1980s when she saw the film “2001: A Space Odyssey” for the first time. As she took in its famous opening scene, in which a bunch of apes picks up a bunch of bones and quickly begins using them to hit each other, Bohannon was struck by the sheer maleness of the moment. “I thought, ‘Where are the females in this story?’” Bohannon said recently, imagining what those absent females might have been up to at that particular time. “It’s like, ‘Oh, sorry, I see you’re doing something really important with a rock. I’m just going to go over there behind that hill and quietly build the future of the species in my womb.” That realization was just one of what Bohannon, 44, calls “a constellation of moments” that led her to write her new book, “Eve: How the Female Body Drove 200 Million Years of Human Evolution.” A page-turning whistle-stop tour of mammalian development that begins in the Jurassic Era, “Eve” recasts the traditional story of evolutionary biology by placing women at its center. The idea is that by examining how women evolved differently from men, Bohannon argues, we can “provide the latest answers to women’s most basic questions about their bodies.” These include, she says: Why do women menstruate? Why do they live longer? And what is the point of menopause? These are timely questions. Thanks to regulations established in the 1970s, clinical trials in the United States have typically used mostly male subjects, from mice to humans. (This is known as “the male norm.”) Though that changed somewhat in 1994, when the National Institutes of Health updated its rules, even the new protocols are replete with loopholes. For example: “From 1996 to 2006, more than 79 percent of animal studies published in the scientific journal Pain included only male subjects,” she writes. © 2023 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 28907 - Posted: 09.13.2023

By Veronique Greenwood Floating languorously through forests and jungles of the Americas, longwing butterflies have many secrets. The 30-odd species in this group include many mimics. The wing markings on some distantly related species of longwings are so similar they inspired one Victorian naturalist to theorize that harmless species could mimic deadly ones to avoid predators. In the age of genomic sequencing, biologists have found other oddities in longwings. In a paper published last week in the Proceedings of the National Academy of Sciences, researchers report that female zebra longwings can see colors that males cannot, thanks to a gene on their sex chromosome. Understanding how it got there might shed light on how differences between sexes can evolve. Like primates, butterflies have a handful of proteins that are sensitive to certain wavelengths of light that, working together, produce the ability to distinguish colors. Curious about the zebra longwing’s vision, Adriana Briscoe, a professor at the University of California, Irvine, and an author of the new paper, asked a student to check the species’ genome for a well-known color vision gene. The gene, known as UVRh1, codes for a protein that is sensitive to ultraviolet light. To her surprise, it was nowhere to be found. Digging deeper, and drawing on genomic data from additional zebra longwings, Dr. Briscoe and her colleagues discovered that UVRh1 was there, but only in females. With lab experiments, they confirmed that females could see markings males couldn’t. They eventually pinpointed the gene in an unexpected place: the butterfly’s tiny sex chromosome. Sex chromosomes in butterflies are unstable, often shedding genes that are picked up by other chromosomes, or lost entirely, Dr. Briscoe said. That makes them a somewhat unusual place to keep something as important as a gene for color vision. © 2023 The New York Times Company

Keyword: Sexual Behavior; Vision
Link ID: 28872 - Posted: 08.19.2023

By Pam Belluck The Food and Drug Administration on Friday approved the first pill for postpartum depression, a milestone considered likely to increase recognition and treatment of a debilitating condition that afflicts about a half-million women in the United States every year. Clinical trial data show the pill works quickly, beginning to ease depression in as little as three days, significantly faster than general antidepressants, which can take two weeks or longer to have an effect. That — along with the fact that it is taken for just two weeks, not for months — may encourage more patients to accept treatment, maternal mental health experts said. The most significant aspect of the approval may not be the features of the drug, but that it is explicitly designated for postpartum depression. Several doctors and other experts said that while there were other antidepressants that are effective in treating the condition, the availability of one specifically shown to address it could help reduce the stigma of postpartum depression by underscoring that it has biological underpinnings and is not something women should blame themselves for. The hope is that it will encourage more women to seek help and prompt more obstetricians and family doctors to screen for symptoms and suggest counseling or treatment. “This is a patient population that just so often falls through the cracks,” said Dr. Ruta Nunacs, a psychiatrist with the Center for Women’s Mental Health at Massachusetts General Hospital. “When women are told, ‘You have postpartum depression,’ it’s embarrassing, it is demeaning, it makes them feel like a bad mom.” She added, “There’s also a lot of stigma about taking antidepressant medication, so that might make this treatment more appealing because it’s really a treatment specific for postpartum depression.” © 2023 The New York Times Company

Keyword: Depression; Sexual Behavior
Link ID: 28867 - Posted: 08.05.2023

By Alejandra Manjarrez Rafael Jiménez Medina learned how to hunt elusive Iberian moles in the fields of southern Spain in the 1980s, when he was a young PhD student in genetics at the University of Granada. A local hunter of the moles (Talpa occidentalis) taught him how to capture these solitary, aggressive and territorial animals. The moles dig subterranean galleries and labyrinths in the meadows of the Iberian Peninsula, especially those with soft soils rich in earthworms, their favorite food. Such activity can benefit the soil — by aerating or mixing it — but the moles’ presence and constant movement in cultivated land raise the ire of farmers, who pay hunters to get rid of them. Jiménez Medina had a different motivation for hunting these subterranean mammals. His doctoral project was to visualize and analyze their chromosomes, which meant collecting, preparing and examining samples from the testes of males. His lab analyses led to a curious finding: Some of the moles he had identified as males were in fact genetically females — that is, their sex chromosomes were XX (female) and not XY (male). The confusion, we now know, stems from the unusual composition of the reproductive organs of female moles. In contrast to most female mammals, which have only ovaries, female Iberian moles also have testicular tissue. This tissue anatomically resembles male testicles but differs in that it produces testosterone but no sperm. The female mole’s organs are composed of both an ovarian and a testicular portion and are known as ovotestes. In addition, female moles have a clitoris covered with a foreskin and with an elongated appearance that resembles a penis; they urinate through this structure. Another unique anatomical feature is that during these females’ juvenile stage, the vaginal orifice remains closed. © 2023 Annual Reviews

Keyword: Sexual Behavior; Evolution
Link ID: 28849 - Posted: 07.19.2023

By Darren Incorvaia When Ambika Kamath was a graduate student in evolutionary biology at Harvard University, she knew one thing for sure: She wasn’t going to research anoles, the lizards that her adviser, Jonathan Losos, specialized in. “I started out as one of those rebellious renegades,” Kamath says, determined to pursue her own research subject. So she went to India for a couple of years to study the poorly understood fan-throated lizards. But when she tried to map out their territories, she found chaos. “All of the lizards were moving everywhere,” she says. Losos encouraged her to work with anoles after all, because it was well established that males hold individual territories that they protect from other males, and females only mate with the male whose territory they reside in. That would make it more straightforward for Kamath to study how anole territoriality differed across habitat types, like forests and parks. So Kamath went to Florida, where she identified individual anoles and tracked their movements day in, day out. Kamath studied the anoles “in a larger area, in a longer period of time than anyone else had ever done,” says Losos, who is now at Washington University in St. Louis. But instead of revealing territorial differences, this massive dataset showed that the anoles weren’t actually territorial in the first place. Kamath looked into the historical record to see where the idea of anole territoriality originated. It started with a 1933 paper that described frequent sexual behavior between male lizards in the lab. The authors had concluded that this lab behavior must be “prevented by something” in the wild, Kamath says, which they inferred was the males protecting territories. “The very first conclusion,” she says, “was based on a homophobic response to observing male-male copulation.” That shaky conclusion caught on, and later researchers assumed it to be true. Introducing a feminist perspective © Society for Science & the Public 2000–2023.

Keyword: Sexual Behavior; Attention
Link ID: 28842 - Posted: 07.06.2023

By Sujata Gupta Teenagers in the United States are in crisis. That news got hammered home earlier this year following the release of a nationally representative survey showing that over half of high school girls reported persistent feelings of “sadness or hopelessness” — common words used to screen for depression. Almost a third of teenage boys reported those same feelings. “No one is doing well,” says psychologist Kathleen Ethier. She heads the U.S. Centers for Disease Control and Prevention’s Division of Adolescent and School Health, which has overseen this biennial Youth Risk Behavior Survey since 1991. During the latest round of data collection, in fall 2021, over 17,000 students from 31 states responded to roughly 100 questions related to mental health, suicidal thoughts and behaviors, sexual behavior, substance use and experiences of violence. One chart in particular garnered considerable media attention. From 2011 to 2021, persistent sadness or hopelessness in boys went up 8 percentage points, from 21 to 29 percent. In girls, it rose a whopping 21 percentage points, from 36 to 57 percent. Some of that disparity may arise from the fact that girls in the United States face unique stressors, researchers say. Compared with boys, girls seem more prone to experiencing mental distress from social media use, are more likely to experience sexual violence and are dealing with a political climate that is often hostile to women’s rights (SN: 7/16/22 & 7/30/22, p. 6). But the gap between boys and girls might not be as wide as the numbers indicate. Depression manifests differently in boys and men than in girls and women, mounting evidence suggests. Girls are more likely to internalize feelings, while boys are more likely to externalize them. Rather than crying when feeling down, for instance, boys may act irritated or lash out. Or they may engage in risky, impulsive or even violent acts. Inward-directed terms like “sadness” and “hopelessness” miss those more typically male tendencies. And masculine norms that equate sadness with weakness may make males who are experiencing those emotions less willing to admit it, even on an anonymous survey. © Society for Science & the Public 2000–2023

Keyword: Depression; Development of the Brain
Link ID: 28841 - Posted: 07.01.2023

Heidi Ledford When Naomi Rance first started studying menopause and the brain, she pretty much had the field to herself. And what she was discovering surprised her. In studies of post-mortem brains, she had found neurons in a region called the hypothalamus that roughly doubled in size in women after menopause1. “This was changing so much in postmenopausal women,” says Rance, a neuropathologist at the University of Arizona in Tucson. “It had to be important.” This was the 1990s, and few other researchers were interested. Rance forged ahead on her own, painstakingly unravelling what the neurons were doing and finessing a way to study menopause symptoms in rats by tracking tiny temperature changes in their tails as a measure of hot flushes, a common symptom of menopause that is thought to be triggered in the hypothalamus. Thirty years later, a drug called fezolinetant, based on Rance’s discoveries, is being evaluated by the US Food and Drug Administration, with an approval decision expected in the first half of this year. If approved, fezolinetant could be a landmark: the first non-hormonal therapy to treat the source of hot flushes, a symptom that has become nearly synonymous with menopause and one that is experienced by about 80% of women going through the transition. (This article uses ‘women’ to describe people who experience menopause, while recognizing that not all people who identify as women go through menopause, and not all people who go through menopause identify as women.) Rance and others in the field, fezolinetant’s progress to this point is a sign that research into the causes and effects of menopausal symptoms is finally being taken seriously. In the next few years, the global number of postmenopausal women is expected to surpass one billion. But many women still struggle to access care related to menopause, and research into how best to manage such symptoms has lagged behind. That is slowly changing. Armed with improved animal models and a growing literature on the effects of existing treatments, more researchers are coming into the field to fill that gap. © 2023 Springer Nature Limited

Keyword: Hormones & Behavior; Learning & Memory
Link ID: 28778 - Posted: 05.10.2023

By Erin Blakemore Newly published research suggests that the sons of women with polycystic ovary syndrome (PCOS) are up to twice as likely to develop obesity as their peers. The study in Cell Reports Medicine used data from cohort research following 467,275 male infants born in Sweden between July 2006 and December 2015. Of those, 9,828 were born to a mother with PCOS — and 147 of those boys were eventually diagnosed with obesity. About 2 in 100 Swedish boys who were born to mothers with PCOS became obese during childhood, compared with about 1 in 100 for boys whose mothers did not have PCOS. The risk was higher among the sons of women who had PCOS and a body mass index (BMI) greater than 25 and highest among the sons of women who both had PCOS and did not take metformin during pregnancy. Researchers followed up the analysis with an RNA sequencing study that found higher cholesterol in sons of Chilean women with PCOS than controls. In another analysis, researchers fed a group of mice a fatty, sugary diet and exposed them to high levels of dihydrotestosterone, a hormone that mimics that of pregnant women with PCOS. Their sons were born with metabolic problems that persisted into adulthood, even when they ate a healthy diet throughout their lives. “We could see that these male mice had more fat tissue, larger fat cells, and a disordered basal metabolism, despite eating a healthy diet,” says Elisabet Stener-Victorin, a reproductive endocrinology and metabolism investigator at the Karolinska Institute in Sweden and the study’s lead author, in a news release.

Keyword: Obesity; Hormones & Behavior
Link ID: 28776 - Posted: 05.10.2023

By Freda Kreier Pregnancy can do weird things to the body. For some bats, it can hamper their ability to “see” the world around them. Kuhl’s pipistrelle bats (Pipistrellus kuhlii) echolocate less frequently while pregnant, researchers report March 28 in BMC Biology. The change may make it harder for the tiny bats to detect prey and potential obstacles in the environment. The study is among the first to show that pregnancy can shape how nonhuman mammals sense their surroundings, says Yossi Yovel, a neuroecologist at Tel Aviv University in Israel. Nocturnal bats like Kuhl’s pipistrelles famously use sound to navigate and hunt prey in the dark (SN: 9/20/17). Their calls bounce off whatever is nearby and bats use the echoes to reconstruct what’s around them, a process aptly named echolocation. The faster a bat makes calls, the better it can make out its surroundings. But rapid-fire calling requires breathing deeply, which is something that pregnancy can get in the way of. “Although I’ve never been pregnant, I know that when I eat a lot, it’s more difficult to breathe,” Yovel says. So pregnancy — which can add a full gram to a 7-gram Kuhl’s pipistrelle and may push up on the lungs — might hamper echolocation. Yovel and colleagues tested their hypothesis by capturing 10 Kuhl’s pipistrelles, five of whom were pregnant, and training the bats to find and land on a platform. Recordings of the animals’ calls revealed that bats that weren’t pregnant made around 130 calls on average while searching for the platform. But bats that were pregnant made only around 110 calls, or 15 percent fewer. © Society for Science & the Public 2000–2023.

Keyword: Hearing; Hormones & Behavior
Link ID: 28774 - Posted: 05.10.2023

Jon Hamilton Boys born to mothers who got COVID-19 while pregnant appear nearly twice as likely as other boys to be diagnosed with subtle delays in brain development. That's the conclusion of a study of more than 18,000 children born at eight hospitals in Eastern Massachusetts. Nearly 900 of the children were born to mothers who had COVID during their pregnancy. In the study, boys, but not girls, were more likely to be diagnosed with a range of developmental disorders in the first 18 months of life. These included delays in speech and language, psychological development and motor function, as well as intellectual disabilities. In older children, these differences are often associated with autism spectrum disorder, says Dr. Roy Perlis, a co-author of the study and a psychiatrist at Massachusetts General Hospital. But for the young children in this study, "it's way too soon to reliably diagnose autism," Perlis says. "All we can hope to detect at this point are more subtle sorts of things like delays in language and speech, and delays in motor milestones." The study, which relied on an analysis of electronic health records, was published in March in the journal JAMA Network Open. The finding is just the latest to suggest that a range of maternal infections can alter fetal brain development, especially in male offspring. For example, studies have found links between infections like influenza and cytomegalovirus, and disorders like autism and schizophrenia. "Male fetuses are known to be more vulnerable to maternal infectious exposures during pregnancy," says Dr. Andrea Edlow, the study's lead author and a maternal-fetal medicine specialist at Massachusetts General Hospital. © 2023 npr

Keyword: Development of the Brain; Sexual Behavior
Link ID: 28743 - Posted: 04.18.2023

By Azeen Ghorayshi Morénike Giwa Onaiwu was shocked when day care providers flagged some concerning behaviors in her daughter, Legacy. The toddler was not responding to her name. She avoided eye contact, didn’t talk much and liked playing on her own. But none of this seemed unusual to Dr. Onaiwu, a consultant and writer in Houston. “I didn’t recognize anything was amiss,” she said. “My daughter was just like me.” Legacy was diagnosed with autism in 2011, just before she turned 3. Months later, at the age of 31, Dr. Onaiwu was diagnosed as well. Autism, a neurodevelopmental disorder characterized by social and communication difficulties as well as repetitive behaviors, has long been associated with boys. But over the past decade, as more doctors, teachers and parents have been on the lookout for early signs of the condition, the proportion of girls diagnosed with it has grown. In 2012, the Centers for Disease Control and Prevention estimated that boys were 4.7 times as likely as girls to receive an autism diagnosis. By 2018, the ratio had dipped to 4.2 to 1. And in data released by the agency last month, the figure was 3.8 to 1. In that new analysis, based on the health and education records of more than 226,000 8-year-olds across the country, the autism rate in girls surpassed 1 percent, the highest ever recorded. More adult women like Dr. Onaiwu are being diagnosed as well, raising questions about how many young girls continue to be missed or misdiagnosed. “I think we just are getting more aware that autism can occur in girls and more aware of the differences,” said Catherine Lord, a psychologist and autism researcher at the University of California, Los Angeles. © 2023 The New York Times Company

Keyword: Autism; Sexual Behavior
Link ID: 28737 - Posted: 04.12.2023

By Bethany Brookshire Cockroaches are changing up their sex lives, and it’s all our fault. Faced with sweet poisoned bait, roaches first ended up with a mutation that made them hate sweets, hindering their mating strategies. Now, more roach mutations are emerging, showing you can’t keep a good pest down. Like many animals, cockroaches have a sweet tooth, and that preference for sugar plays a central role in their reproductive activities. When a male roach targets a female roach, he will back up to her, secreting a solution called a nuptial gift from the tergal gland under his wings. The solution is full of proteins, fats and sugars, what some researchers call the chocolate of roach food. The female cockroach will crawl up on his back to take a sample, and while she is occupied, the male will whip out a hooked penis to latch onto her reproductive tract. They will then turn back to back and do the deed for about 90 minutes. Humans have aimed to exploit this love of sweet stuff to push cockroaches — particularly the German cockroaches that turn up in American homes — out of our spaces. For decades, people used poisoned roach baits baited with solutions containing glucose. Cockroaches took the bait. But some time in the late 20th century, a new mutation arose — glucose aversion. No one knows how many roaches now hate the sweet stuff, but Coby Schal, an evolutionary biologist at North Carolina State University, suspects the mutation is very common. “There are more and more papers being published on the fact that a whole suite of baits don’t work so well,” he said. This lack of a sweet tooth saved cockroaches from death, but it hurt their sex lives. The gift that normal males secrete contains maltose, a sugar that cockroach saliva transforms into glucose. But if females had the glucose averse mutation, they did not find the male secretions sexy and turned away before the male could hook on. © 2023 The New York Times Company

Keyword: Chemical Senses (Smell & Taste); Evolution
Link ID: 28722 - Posted: 03.29.2023

By Azeen Ghorayshi For decades, male mice have been the default in scientific experiments that test new drugs or examine the connections of the brain. The reason? Female mice, which experience a four- to five-day cycle of fluctuating ovarian hormones, were thought to be too complicated. Accounting for the hormonal changes was viewed as too cumbersome and too expensive. But the estrous cycle has little to do with how female mice behave, according to a new study that used machine-learning software to track the second-to-second behavior of animals exploring an open space. Male mice actually exhibited more erratic behavior than females did. The study, published in the journal Current Biology on Tuesday, challenges century-old stereotypes that kept female animals out of laboratory research — and, until the 1990s, barred women from clinical trials. The new research is “tipping all of these assumptions about sex differences and the influence of hormones on their head,” said Rebecca Shansky, a behavioral neuroscientist at Northeastern University and a co-author of the new study. The cost of excluding females — whether human or animal — from scientific research is high. Women are almost twice as likely as men to experience severe side effects from drugs, most of which have dosages based on the initial testing done in men. Women also may not derive the same benefits from the drugs. Women “capable of becoming pregnant,” as the federal government put it, were largely excluded from clinical trials of drugs until 1993, when a new law required researchers funded by the National Institutes of Health to include women and minority groups. In the decades since, women have made up close to half of clinical research participants, though they still lag behind in studies of certain drugs, like those used to treat cardiovascular disease and psychiatric disorders. But a large sex gap persisted in basic science research using lab animals, studies that pave the way to medical breakthroughs. In neuroscience, according to a review published in 2010, studies of male lab animals outnumbered female ones by a factor of five. © 2023 The New York Times Company

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 28694 - Posted: 03.08.2023

Heidi Ledford Under the right circumstances, even moderately hungry mice prefer to socialize with the opposite sex than to eat, researchers have found1. In research published on 23 February in Cell Metabolism, scientists treated male mice with a technique that mimics the effects of leptin, a hormone that acts on the brain to suppress appetite. Treated mice were more likely to approach female mice than their food bowls — even if the test rodents had been deprived of food for almost an entire day. The findings reveal a surprising role for leptin in social behaviour. They are also a step towards understanding how animals prioritize different behavioural options in response to ongoing needs — an enduring question in neuroscience, says Gina Leinninger, who studies the neural regulation of feeding at Michigan State University in East Lansing. The paper “addresses a huge gap in the field”, she says. “When you no longer need to eat urgently, it should free you up to do other things.” The new work, Leinninger says, illuminates how the brain juggles these various demands. Food versus friends Neuroscientists Anne Petzold and Tatiana Korotkova at the University of Cologne in Germany, and their colleagues, sought to understand how such decision-making is affected by leptin, which activates a subset of cells in the brain and promotes a feeling of fullness. The researchers injected male mice with leptin and saw that it suppressed feeding, as expected — but also promoted interactions with female mice. The team examined neurons in the brain’s ‘hunger center’, the lateral hypothalamus, that are activated by leptin. The authors’ experiments showed that neurons that can sense leptin were activated when mice interacted with members of the opposite sex. Artificially activating those neurons using a technique called optogenetics raised the likelihood that a mouse would approach a member of the opposite sex. Both results suggest that leptin plays a part in promoting social behaviour. © 2023 Springer Nature Limited

Keyword: Obesity; Sexual Behavior
Link ID: 28682 - Posted: 02.25.2023

By Virat Markandeya It’s evening at the northern tip of the Red Sea, in the Gulf of Aqaba, and Tom Shlesinger readies to take a dive. During the day, the seafloor is full of life and color; at night it looks much more alien. Shlesinger is waiting for a phenomenon that occurs once a year for a plethora of coral species, often several nights after the full moon. Guided by a flashlight, he spots it: coral releasing a colorful bundle of eggs and sperm, tightly packed together. “You’re looking at it and it starts to flow to the surface,” Shlesinger says. “Then you raise your head, and you turn around, and you realize: All the colonies from the same species are doing it just now.” Some coral species release bundles of a pinkish- purplish color, others release ones that are yellow, green, white or various other hues. “It’s quite a nice, aesthetic sensation,” says Shlesinger, a marine ecologist at Tel Aviv University and the Interuniversity Institute for Marine Sciences in Eilat, Israel, who has witnessed the show during many years of diving. Corals usually spawn in the evening and night within a tight time window of 10 minutes to half an hour. “The timing is so precise, you can set your clock by the time it happens,” Shlesinger says. Moon-controlled rhythms in marine critters have been observed for centuries. There is calculated guesswork, for example, that in 1492 Christopher Columbus encountered a kind of glowing marine worm engaged in a lunar-timed mating dance, like the “flame of a small candle alternately raised and lowered.” Diverse animals such as sea mussels, corals, polychaete worms and certain fishes are thought to synchronize their reproductive behavior by the moon. The crucial reason is that such animals — for example, over a hundred coral species at the Great Barrier Reef — release their eggs before fertilization takes place, and synchronization maximizes the probability of an encounter between eggs and sperm. © 2023 Annual Reviews

Keyword: Biological Rhythms; Sexual Behavior
Link ID: 28681 - Posted: 02.25.2023

By Erin Garcia de Jesús A female giraffe has a great Valentine’s Day gift for potential mates: urine. Distinctive anatomy helps male giraffes get a taste for whether a female is ready to mate, animal behaviorists Lynette and Benjamin Hart report January 19 in Animals. A pheromone-detecting organ in giraffes has a stronger connection to the mouth than the nose, the researchers found. That’s why males scope out which females to mate with by sticking their tongues in a urine stream. Animals such as male gazelles will lick fresh urine on the ground to track if females are ready to mate. But giraffes’ long necks and heavy heads make bending over to investigate urine on the ground an unstable and vulnerable position, says Lynette Hart, of the University of California, Davis. The researchers observed giraffes (Giraffa giraffa angolensis) in Etosha National Park in Namibia in 1994, 2002 and 2004. Bull giraffes nudged or kicked the female to ask her to pee. If she was a willing participant, she urinated for a few seconds, while the male took a sip. Then the male curled his lip and inhaled with his mouth, a behavior called a flehmen response, to pull the female’s scent into two openings on the roof of the mouth. From the mouth, the scent travels to the vomeronasal organ, or VNO, which detects pheromones. The Harts say they never saw a giraffe investigate urine on the ground. Unlike many other mammals, giraffes have a stronger oral connection — via a duct — to the VNO, than a nasal one, examinations of preserved giraffe specimens showed. One possible explanation for the difference could be that a VNO-nose link helps animals that breed at specific times of the year detect seasonal plants, says Benjamin Hart, a veterinarian also at the University of California, Davis. But giraffes can mate any time of year, so the nasal connection may not matter as much. © Society for Science & the Public 2000–2023.

Keyword: Chemical Senses (Smell & Taste); Sexual Behavior
Link ID: 28664 - Posted: 02.15.2023

By Elizabeth Preston A fully grown male orca is one of the planet’s fiercest hunters. He’s a wily, streamlined torpedo who can weigh as much as 11 tons. No other animal preys on him. Yet in at least one population, these apex predators struggle to survive without their moms, who catch their food and even cut it up for them. Scientists have previously seen that some killer whale mothers share food with their grown sons. In a study published Wednesday in Current Biology, researchers found that this prolonged feeding carries a huge reproductive cost for mothers. Killer whales, actually the largest members of the dolphin family, swim throughout the world’s oceans. Yet they live in discrete populations with their own territories, dialects and hunting customs. A group that spends much of the year off the coast of British Columbia, Washington and Oregon is known as the southern residents. They eat mainly Chinook salmon, which have been increasingly hard to find. “Killer whales worldwide are doing fine,” said Michael Weiss, research director at the Center for Whale Research in Friday Harbor, Wash. But the southern residents, with a population of just 73, are considered endangered. These whales stay with their birth family for their whole lives. The families are led by matriarchs who can live 80 to 90 years. Yet the females stop reproducing in midlife: Orcas and a few other whale species are the only mammals, besides humans, known to undergo menopause. To try to explain menopause, scientists have looked for ways that matriarchs encourage the survival of their children and grandchildren. A 2012 study of southern resident killer whales, along with their neighbors, the northern residents, showed that the presence of older moms helped adult offspring stay alive — especially sons. Males over age 30 were eight times more likely to die in the year following their own mothers’ deaths. © 2023 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 28662 - Posted: 02.11.2023

By Susan Dominus For the past two or three years, many of my friends, women mostly in their early 50s, have found themselves in an unexpected state of suffering. The cause of their suffering was something they had in common, but that did not make it easier for them to figure out what to do about it, even though they knew it was coming: It was menopause. The symptoms they experienced were varied and intrusive. Some lost hours of sleep every night, disruptions that chipped away at their mood, their energy, the vast resources of good will that it takes to parent and to partner. One friend endured weeklong stretches of menstrual bleeding so heavy that she had to miss work. Another friend was plagued by as many as 10 hot flashes a day; a third was so troubled by her flights of anger, their intensity new to her, that she sat her 12-year-old son down to explain that she was not feeling right — that there was this thing called menopause and that she was going through it. Another felt a pervasive dryness in her skin, her nails, her throat, even her eyes — as if she were slowly calcifying. Then last year, I reached the same state of transition. Technically, it is known as perimenopause, the biologically chaotic phase leading up to a woman’s last period, when her reproductive cycle makes its final, faltering runs. The shift, which lasts, on average, four years, typically starts when women reach their late 40s, the point at which the egg-producing sacs of the ovaries start to plummet in number. In response, some hormones — among them estrogen and progesterone — spike and dip erratically, their usual signaling systems failing. During this time, a woman’s period may be much heavier or lighter than usual. As levels of estrogen, a crucial chemical messenger, trend downward, women are at higher risk for severe depressive symptoms. Bone loss accelerates. In women who have a genetic risk for Alzheimer’s disease, the first plaques are thought to form in the brain during this period. Women often gain weight quickly, or see it shift to their middles, as the body fights to hold onto the estrogen that abdominal fat cells produce. The body is in a temporary state of adjustment, even reinvention, like a machine that once ran on gas trying to adjust to solar power, challenged to find workarounds. © 2023 The New York Times Company

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 28658 - Posted: 02.08.2023

By McKenzie Prillaman A newfound species of frog doesn’t ribbit. In fact, it doesn’t make any sound at all. Many frogs have unusual characteristics, from turning translucent to being clumsy jumpers (SN: 12/22/22; 6/15/22). The recently discovered amphibian lacks a voice. It joins a group of seven other voiceless frog species called spiny-throated reed frogs that reside in East Africa. Instead of croaking, the spines on male frogs’ throats might help their female counterparts recognize potential mates via touch, sort of like braille, says conservation biologist Lucinda Lawson of the University of Cincinnati. Lawson and colleagues spotted the little frog, only about 25 millimeters long, in 2019 while surveying wildlife in Tanzania’s Ukaguru Mountains. The team immediately recognized the animal, now named Hyperolius ukaguruensis, as a spiny-throated reed frog. But something seemed off. “It [was] the wrong color,” Lawson says. Most frogs from this group are green and silver, but this one was gold and brown. Some quick measurements to check if the peculiar frog simply had trivial color variations or if it could be a new species revealed that its eyes were smaller than other spiny-throated reed frogs. The researchers agreed: “Let’s do some genetics,” Lawson says. They ran DNA tests on two frogs that looked like they belonged to the suspected new species, as well as 10 individuals belonging to known spiny-throated species. Comparing the golden frogs’ genetic makeup with that of the others revealed the oddballs were genetically distinct, Lawson and colleagues report February 2 in PLOS ONE. © Society for Science & the Public 2000–2023.

Keyword: Animal Communication; Sexual Behavior
Link ID: 28655 - Posted: 02.04.2023