Category: Science News

{A study has found asymmetry in the cranial bones of Mexican cavefish}

Imagine living in perpetual darkness in an alien world where you have to find food quickly by touch or starve for months at a time.

The limestone caverns of Mexico’s Sierra del Abra Tanchipa rainforest contain deep cisterns cloaked in utter blackness. This is where researchers at the University of Cincinnati traveled to find a little fish (Astyanax mexicanus) that has evolved to feast or endure famine entombed hundreds of feet below the ground.

“They have been able to invade this really extreme environment. They are exposed to darkness their entire life yet they’re able to survive and thrive,” said Amanda Powers, a UC graduate student and lead author of a study on blind cavefish published in May in the journal PLOS One.

“They’ve evolved changes to their metabolism and skull structure. They’ve enhanced their sensory systems. And they can survive in an environment where not many animals could,” she said.

Mexican cavefish are bizarre, not merely blind but born with eyes that regress until they are completely lost as adults. The bones of their once-round eye orbits have collapsed. In place of eyes, their empty sockets store fat deposits that are covered in the same silvery, nearly translucent scales as the rest of their pale, unpigmented bodies.

The UC study examined one biological adaptation that might help to explain how these fish navigate and find food without benefit of sight — asymmetry. Researchers examined juvenile and adult cavefish to understand how their skulls change during their lives.

Most fish are symmetrical — their left and right sides are virtually identical and streamlined to provide the most efficient locomotion in the water.

Cavefish are genetically similar to their symmetrical and keen-sighted cousins, Mexican tetras, found in nearby creeks and rivers on the surface. They’re so closely related that they easily interbreed and produce fertile young, even though the two species are believed to have diverged millions of years ago.

Cavefish start their lives with symmetrical features like other fish. But when they mature, their fragmented cranial bones harden in a visibly skewed direction, the study found.

UC’s researchers speculate that this adaptation helps the typically left-leaning cavefish navigate by using sensory organs called neuromasts to follow the contours of the cave as they swim in a perpetual counterclockwise pattern. This behavior was observed among captive cavefish, which keep moving around the edges of their tanks while surface fish tend to stay motionless in the shadows of their tank or swim in haphazard ways.

“That was a real big piece of the puzzle for us,” said Joshua Gross, a UC biology professor and co-author. “It’s a mystery how they’ve been able to adapt. The amazing thing is that they’re not just barely surviving — they thrive in total darkness.”

Gross has been studying cavefish for years at UC. They make an excellent model to examine regressive evolution, the process by which animals lose features over generations, he said.

“The traits they’ve lost are very conspicuous — their eyes, their pigmentation,” Gross said. “The beauty of studying cave animals is it’s a very robust model for understanding why features are lost, and it’s a simple, stable set of environmental pressures that cause those features to go away.”

Cave-dwelling animals as diverse as salamanders and crayfish have responded similarly by losing pigment and eyesight while gaining or augmenting other sensory structures.

“The fact that they’re all moving in the same evolutionary direction is not a coincidence. They’re all living in total darkness with a limited food supply,” he said.

Cavefish are especially valuable for evolutionary study, Gross said, because of their genetic relationship with readily abundant surface fish. Many antecedents of other cave-dwelling animals have been lost to extinction from natural selection or calamity.

The UC biology lab has dozens of aquariums and breeding tanks full of cave and surface fish, each smaller than a goldfish. Researchers use QR-code stickers to keep track of the family history of the resident fish swimming in slow circles.

The hardy fish are easy to keep because they are not picky eaters. They get a mix of foods including flakes, brine shrimp and blackworms. UC gets its study fish from natural populations maintained by colleagues and reputable breeders.

“Our lab really tries to avoid taking any animals from nature,” Gross said.

Mexican cavefish also are raised as a popular aquarium pet.

The skulls of all but a couple cavefish UC studied bend to the left. They seem to be right-finned, swimming in a lazy counterclockwise pattern around their aquariums in the biology lab.

“You could see how asymmetry might be an advantage in navigation,” Powers said.

“They tend to swim in a unidirectional, circular motion around their tanks to explore their surroundings,” she said. “Having asymmetry in their skull we think is attributed to handedness. If their skull is bent to the left, they could be ‘right-handed.’ They’re feeling the wall to the right with their sensory structures.”

This kind of asymmetry is uncommon in nature. Think of the fiddler crab with its outsized claw. Owls have asymmetrical ears — one canal placed higher on the skull than the other — perhaps to help the night predators target the faint rustling of a mouse in the dark.

In the biology lab, researchers breed surface fish with cavefish and study the resulting hybrids, co-author and recent UC graduate Shane Kaplan said. He and UC student Erin Davis also contributed to the study.

The interesting genetic combinations occur in the second generation or F2 population of hybridization, he said.

“You can capture the genetic diversity of the entire population,” Kaplan said. “Some fish look exactly like surface fish. Others look exactly like cavefish. Then you’ll have intermittent phenotypes. Some are pale but have eyes while others will have no eyes but are fully pigmented.”

The study was funded by grants from the National Institutes of Health and the National Science Foundation.

Powers traveled with Gross to Mexico in 2013, in 2015 and again this year to study wild cavefish. They wore dust masks to guard against fungal spores associated with the respiratory disease histoplasmosis, which can be found in bat guano. Getting to the fish pools required a little spelunking.

“The group ahead of us disturbed some bats. As we were coming in, bats were going out,” she said. “They have incredible echo-location. The bats knew where you were and would fly around you in the darkness, even though it was a very small chamber.”

The cave had several distinct pools, each farther from the entrance. The deeper they went, the fewer surface-dwelling fish they found until they found only blind cavefish.

“Whenever you would touch the surface of the water with your finger, a swarm of cavefish would come right up to it,” Powers said. “Not many fish would do that. These cavefish have zero predators so they’re not afraid. That was a really cool experience.”

Kaplan said it would be worthwhile to explore the cavefish’s DNA to find out what prompts the asymmetry in adult cavefish.

“We haven’t yet delved into why it’s happening. I’d love to get more into the genetics and developmental processes that lead to these bizarre phenotypes,” Kaplan said.

Gross said his biology lab will continue to pursue these and other questions about this fascinating fish that has mastered a dark, subterranean realm, indifferent to the bright, colorful and chaotic world above it.

Source:Science Daily

{Daily interactions with toddlers may be influenced by gender, research finds}

Fathers with toddler daughters are more attentive and responsive to those daughters’ needs than fathers with toddler sons are to the needs of those sons, according to brain scans and recordings of the parents’ daily interactions with their kids.

Fathers of toddlers also sang more often to their daughters and spoke more openly about emotions, including sadness, possibly because they are more accepting of girls’ feelings than boys’, according to the study, published in the American Psychological Association’s journal Behavioral Neuroscience. Fathers of sons engaged in more rough-and-tumble play and used more achievement-related language (e.g., words such as proud, win and top) when talking to their sons. Fathers of daughters used more analytical language (e.g., words such as all, below and much), which has been linked to future academic success.

“If the child cries out or asks for Dad, fathers of daughters responded to that more than did fathers of sons,” said lead researcher Jennifer Mascaro, PhD, of Emory University. “We should be aware of how unconscious notions of gender can play into the way we treat even very young children.”

The research examined whether the varying ways in which fathers treat sons or daughters may be influenced by different brain responses to male or female children. The study couldn’t determine if those different brain responses meant fathers are somehow hard wired through genetics or evolution to treat sons differently than they treat daughters or if the fathers were conforming to societal norms relating to gender.

Studies about parenting often are biased in the lab because participants give answers that they think are expected of them or are not aware of their own behavior. The researchers, from Emory University and the University of Arizona, avoided that problem by taking their study out of the lab and into the real world. The study used data from 52 fathers of toddlers (30 girls, 22 boys) in the Atlanta area who agreed to clip a small handheld computer onto their belts and wear it for one weekday and one weekend day. The device randomly turned on for 50 seconds every nine minutes to record any sound during the 48-hour period. Some of the fathers in the study had more than one child, but the study focused only on their interactions with one son or daughter.

“People act shockingly normal when they are wearing it,” Mascaro said. “They kind of forget they are wearing it or they say to themselves, what are the odds it’s on right now.”

The fathers also were told to leave the device charging in their child’s room at night so any nighttime interactions with their children could be recorded, said Mascaro, an assistant professor in Family and Preventative Medicine at the Emory School of Medicine.

Fathers also underwent functional MRI brain scans while viewing photos of an unknown adult, an unknown child, and their own child with happy, sad or neutral facial expressions. Fathers of daughters had greater responses to their daughters’ happy facial expressions in areas of the brain important for visual processing, reward, emotion regulation, and face processing than fathers of sons. In a finding that the researchers hadn’t predicted, the brains of the fathers of boys responded more robustly to their sons’ neutral facial expressions, possibly because fathers are responding to the more ambiguous emotional displays of their sons. There was no significant difference in the fathers’ brain responses to sad facial expressions from sons or daughters.

In daily interactions, fathers of daughters used more language referencing the child’s body (e.g., words such as belly, foot and tummy) relative to fathers of sons. Previous research has shown that pre-adolescent girls are more likely than boys to report body dissatisfaction and lower self-esteem relating to body image.

The study focused on fathers because there is less research about fathers’ roles in rearing young children than mothers, Mascaro said. The study couldn’t make any definitive long-term connections between the varying treatment of sons or daughters as toddlers and future outcomes for those children, but the research explored some possible links that may offer some recommendations for fathers. Since the research was conducted in the United States, the study also couldn’t draw any conclusions about fathers in other cultures with different societal norms for fathers.

If fathers are more present and attentive to daughters and open to expressing emotions, that may help girls develop more empathy than boys, so fathers of sons could take the same approach as fathers of daughters, Mascaro said. “The fact that fathers may actually be less attentive to the emotional needs of boys, perhaps despite their best intentions, is important to recognize,” she said.

Other research has found that restricted emotions in adult men is linked to depression, decreased social intimacy, marital dissatisfaction and a lower likelihood of seeking mental health treatment.

Previous research also has shown that rough-and-tumble play by parents can help young children better regulate their emotions. Fathers of daughters may want to engage in more rough-and-tumble play with girls, even though such play is more often associated with boys, Mascaro said.

“Most dads are trying to do the best they can and do all the things they can to help their kids succeed, but it’s important to understand how their interactions with their children might be subtly biased based on gender,” Mascaro said.

Source:Science Daily

{There are significant gaps in our knowledge on the evolution of sex, according to a research review on sex chromosomes from Lund University in Sweden. Even after more than a century of study, researchers do not know enough about the evolution of sex chromosomes to understand how males and females emerge.}

Greater focus on ecological aspects would increase this knowledge, according to evolutionary biologists at Lund University, who have reviewed a lot of the research conducted in this field in the last 100 years.

Female and male bodies work differently, even though they have the same genome. One example is reproduction.

“There is a form of genetic conflict between the sexes — a conflict in the genome itself — which we know little about,” says professor Bengt Hansson at Lund University.

Together with senior lecturer Jessica Abbott and doctoral student Anna Nordén, he has read more than 100 scientific articles and papers describing the evolution of sex chromosomes and the genome. Together, they have identified two tracks that have each dominated the research since the late 19th century: empirical studies and various theories.

The review shows that the significance of ecology has not been sufficiently noted. Therefore, the biologists in Lund call for more research on how the living environment of a population affects the development and evolution of sex chromosomes. This could include factors such as access to food, age variations within a population or the consequences for sex chromosomes when populations that have lived separately meet and mix.

“Additional approaches in research will probably lead to a much more detailed understanding of the development of sex chromosomes and, in turn, of how females and males evolve,” says Jessica Abbott.

The research can lead to concrete benefits. One example is releasing sterile males in populations of malaria mosquitoes, as an attempt to limit the number of mosquitoes in certain areas.

Drugs that target women or men specifically are another hot research field. According to the biologists at Lund University, this is also an area that requires more knowledge on the evolution of sex chromosomes.

Source:Science Daily

{A baby’s babbles start to sound like speech more quickly if they get frequent vocal feedback from adults. Princeton University researchers have found the same type of feedback speeds the vocal development of infant marmoset monkeys, in the first evidence of such learning in nonhuman primates, researchers report in Current Biology on May 25.}

“We wanted to find out whether the idea that monkeys don’t do any learning during their vocal development is actually true,” says the study’s senior co-author Asif Ghazanfar, a professor of psychology and the Princeton Neuroscience Institute. “So we picked a species that we know really relies on vocalizations as its primary social signals. What we found in marmoset vocal development very closely parallels pre-linguistic vocal development in humans.”

Although marmoset vocal calls do not approach the complexity of human language systems, vocal development in both species begins with infants making more or less random sounds.

“When an infant blurts out something and the parent responds, that’s a contingent response. And the more often a parent provides that contingent response, the faster the human infant will develop its vocalizations,” Ghazanfar says.

To find out whether the same principle held true for marmosets, Ghazanfar and his colleagues set up an experiment using pairs of fraternal twin marmosets, small, highly social monkeys from South America. Starting from the day after the marmosets were born, the researchers would separate the infants from the adult marmosets for 40 minutes each day. In the first 10 minutes, they recorded the noises that the infant marmosets made while sitting alone. Then, for the next half hour, the researchers gave the young marmosets contingent feedback in the form of audio playbacks of the parent’s calls.

One twin in each pair got consistent feedback, mirroring what a young marmoset would receive from an especially attentive parent; the other twin got less consistent feedback on their vocalizations. They repeated these experiments up until the infants were 2 months old, roughly the equivalent of 2 years old in marmoset years.

Even though these sessions lasted less than an hour each day, infant marmosets that received lots of contingent feedback developed adult-sounding calls more rapidly than their siblings.

“When they’re infants, this call is really noisy,” Ghazanfar says. “It sounds kind of coarse, and then gradually it becomes very clean and tonal like an adult call.”

Previous studies had found a correlation between the amount of feedback marmosets get from parents and the rate of vocal development, but the experimental design in this study more firmly establishes the causality between parental responses and vocal development, the researchers say.

“This system of vocal learning production may be linked to the idea that an infant that more quickly produces adult-sounding calls is more likely to get care from a caregiver in a cooperative breeding environment where multiple individuals could be that caregiver in addition to the parents,” Ghazanfar says. “So it’s not only this process of learning that’s similar to humans; the whole reproductive strategy is similar to humans.”

The researchers’ next steps will include collecting more detailed data on marmosets’ neural activity when they are chattering or calling to neighbors, he says.

Even though marmosets can’t “talk” in the same way humans do, understanding marmoset communication may help us understand the evolution and development of speech.

“Vocal production learning isn’t just about imitation,” Ghazanfar saus. “And you can no longer say that nonhuman primates shows no evidence of vocal learning.”

Source:Science Daily

{Reading is such a new ability in human evolutionary history that the existence of a ‘reading area’ could not be specified in our genes. A kind of recycling process has to take place in the brain while learning to read: Areas evolved for the recognition of complex objects, such as faces, become engaged in translating letters into language. Some regions of our visual system thereby turn into interfaces between the visual and language systems.}

“Until now it was assumed that these changes are limited to the outer layer of the brain, the cortex, which is known to adapt quickly to new challenges,” says project leader Falk Huettig from the Max Planck Institute for Psycholinguistics. The Max Planck researchers together with Indian scientists from the Centre of Bio-Medical Research (CBMR) Lucknow and the University of Hyderabad have now discovered what changes occur in the adult brain when completely illiterate people learn to read and write. In contrast to previous assumptions, the learning process leads to a reorganisation that extends to deep brain structures in the thalamus and the brainstem. The relatively young phenomenon of human writing therefore changes brain regions that are very old in evolutionary terms and already core parts of mice and other mammalian brains.

“We observed that the so-called colliculi superiores, a part of the brainstem, and the pulvinar, located in the thalamus, adapt the timing of their activity patterns to those of the visual cortex,” says Michael Skeide, scientific researcher at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) in Leipzig and first author of the study, which has just been published in the magazine Science Advances. “These deep structures in the thalamus and brainstem help our visual cortex to filter important information from the flood of visual input even before we consciously perceive it.” Interestingly, it seems that the more the signal timings between the two brain regions are aligned, the better the reading capabilities. “We, therefore, believe that these brain systems increasingly fine-tune their communication as learners become more and more proficient in reading,” the neuroscientist explains further. “This could explain why experienced readers navigate more efficiently through a text.”

{{Large-scale study with illiterates in India}}

The interdisciplinary research team obtained these findings in India, a country with an illiteracy rate of about 39 percent. Poverty still limits access to education in some parts of India especially for women. Therefore, in this study nearly all participants were women in their thirties. At the beginning of the training, the majority of them could not decipher a single written word of their mother tongue Hindi. Hindi, one of the official languages of India, is based on Devanagari, a scripture with complex characters describing whole syllables or words rather than single letters.

Participants reached a level comparable to a first-grader after only six months of reading training. “This growth of knowledge is remarkable,” says project leader Huettig. “While it is quite difficult for us to learn a new language, it appears to be much easier for us to learn to read. The adult brain proves to be astonishingly flexible.” In principle, this study could also have taken place in Europe. Yet illiteracy is regarded as such a taboo in the West that it would have been immensely difficult to find volunteers to take part. Nevertheless, even in India where the ability to read and write is strongly connected to social class, the project was a tremendous challenge. The scientists recruited volunteers from the same social class in two villages in Northern India to make sure that social factors could not influence the findings. Brain scans were performed in the city of Lucknow, a three hours taxi ride away from participants’ homes.

{{A new view on dyslexia}}

The impressive learning achievements of the volunteers do not only provide hope for adult illiterates, they also shed new light on the possible cause of reading disorders such as dyslexia. One possible cause for the basic deficits observed in people with dyslexia has previously been attributed to dysfunctions of the thalamus. “Since we found out that only a few months of reading training can modify the thalamus fundamentally, we have to scrutinise this hypothesis,” neuroscientist Skeide explains. It could also be that affected people show different brain activity in the thalamus just because their visual system is less well trained than that of experienced readers. This means that these abnormalities can only be considered an innate cause of dyslexia if they show up prior to schooling. “That’s why only studies that assess children before they start to learn to read and follow them up for several years can bring clarity about the origins of reading disorders,” Huettig adds.

Source:Science Daily

{The human brain is much better than previously thought at discovering and avoiding disease, a new study led by researchers at Karolinska Institutet in Sweden reports. Our sense of vision and smell alone are enough to make us aware that someone has a disease even before it breaks out. And not only aware — we also act upon the information and avoid sick people. The study is published in the scientific journal Proceedings of the National Academy of Sciences (PNAS).}

The human immune system is effective at combating disease, but since it entails a great deal of energy expenditure disease avoidance should be part of our survival instinct. A new study now shows that this is indeed the case: the human brain is better than previously thought at discovering early-stage disease in others. Moreover, we also have a tendency to act upon the signals by liking infected people less than healthy ones.

“The study shows us that the human brain is actually very good at discovering this and that this discovery motivates avoidance behaviour,” says principal investigator Professor Mats Olsson at Karolinska Institutet’s Department of Clinical Neuroscience.

By injecting harmless sections of bacteria, the researchers activated the immune response in participants, who developed the classic symptoms of disease — tiredness, pain and fever — for a few hours, during which time smell samples were taken from them and they were photographed and filmed. The injected substance then disappeared from their bodies and with it the symptoms.

Another group of participants were then exposed to these smells and images as well as those of healthy controls, and asked to rate how much they liked the people, while their brain activities were measured in an MR scanner.

They were then asked to state, just by looking at the photographs, which of the participants looked sick, which they considered attractive and which they might consider socialising with.

“Our study shows a significant difference in how people tend to prefer and be more willing to socialise with healthy people than those who are sick and whose immune system we artificially activated,” says Professor Olsson. “We can also see that the brain is good at adding weak signals from multiple senses relating to a person’s state of health.”

This he sees as biological confirmation of the argument that survival naturally entails avoiding infection.

“Common sense tells us that there should be a basic behavioural repertoire that assists the immune system. Avoidance, however, does not necessarily apply if you have a close relationship with the person who is ill,” says Professor Olsson. “For instance, there are few people other than your children who you’d kiss when they have a runny nose. In other words, a disease signal can enhance caring behaviour in close relationships. With this study, we demonstrate that the brain is more sensitive to those signals than we once thought.”

The research has been carried out in collaboration with several parties, especially with the Stress Research Institute at Stockholm University.

Source:Science Daily

{Listening to music from other cultures furthers one’s pro-diversity belief}

Jake Harwood turned his lifelong hobby as a musician into a scholarly question: Could the sharing of music help ease interpersonal relations between people from different backgrounds, such as Americans and Arabs?

To explore the issue, and building on his years of research on intergroup communication, Harwood began collaborating two to three years ago with his graduate students and other researchers on a number of studies, finding that music is not merely a universal language. It appears to produce a humanizing effect for members of groups experiencing social and political opposition.

“Music would not have developed in our civilizations if it did not do very important things to us,” said Harwood, a professor in the University of Arizona Department of Communication. “Music allows us to communicate common humanity to each other. It models the value of diversity in ways you don’t readily see in other parts of our lives.”

Harwood is presenting his team’s research during the International Communication Association’s 67th annual conference, to be held May 25-29 in San Diego.

In one study, Harwood worked with UA graduate researchers Farah Qadar and Chien-Yu Chen to record a mock news story featuring an Arab and an American actor playing music together. The researchers showed the video clip to U.S. participants who were not Arab. The team found that when viewing the two cultures collaborating on music, individuals in the study were prone to report more positive perceptions — less of a prejudiced view — of Arabs.

“The act of merging music is a metaphor for what we are trying to do: Merging two perspectives in music, you can see an emotional connection, and its effect is universal,” said Qadar, who graduated from the UA in 2016 with a master’s degree in communication.

The team published those findings in an article, “Harmonious Contact: Stories About Intergroup Musical Collaboration Improve Intergroup Attitudes.” The article appeared in a fall issue of the peer-reviewed Journal of Communication.

Another major finding: The benefits were notable, even when individuals did not play musical instruments themselves. Merely listening to music produced by outgroup members helped reduce negative feelings about outgroup members, Harwood said.

“It’s not just about playing Arab music. But if you see an Arab person playing music that merges the boundary between mainstream U.S. and Arab, then you start connecting the two groups,” Harwood said.

As part of his ongoing research in a different study, which he will present during the International Communication Association conference, Harwood and Stefania Paolini, a senior lecturer at the University of Newcastle’s School of Psychology, measured people’s appreciation for diversity, gauging how they felt about members of other groups. After doing so, the team asked people to listen to music from other cultures and then report how much they enjoyed the music and what they perceived of the people the music represented.

The team found that people who value diversity are more likely to enjoy listening to music from other cultures, and that act of listening furthers one’s pro-diversity beliefs.

“It has this sort of spiral effect. If you value diversity, you are going to listen to more music from other cultures,” Harwood said, noting that that research is continuing. “If all you are doing is listening to the same type of music all the time, there is homogeneity that is not doing a lot to help people to increase their value for diversity.”

For Harwood and his collaborators, these findings are affirming given the decades-old world music explosion and more recent examples of performers around the world who regularly sample and cross-reference outgroup musical traditions and elements.

Harwood pointed to Paul Simon’s “Graceland” album as an early and notable example. Released in 1986, the album drew influence from South African instrumentation and rhythms.

“It was the start of the world music phenomena,” Harwood said. “Suddenly, everyone wanted to listen to African music. Then Indonesian, then Algerian music. Then you see this modeling of new music with different musical cultures and different people collaborating with each other.”

Harwood also said artists such as Eminem and Rihanna are among those who are experimenting with music that crosses cultural boundaries. “This whole new type of music is emerging that would not exist if you did not have that kind of cross-collaboration.”

Harwood also said his team’s findings build on earlier research and emergent models of intergroup dialogue that encourage direct contact and conversation to help build cross-cultural understanding and cohesion.

“We must think about music as a human, social activity rather than a sort of beautiful, aesthetic hobby and appreciate how fundamental it is to us all,” he said. “We can then begin to see people from other groups as more human and begin to recategorize one another as members as the same group.”

Source:Science Daily

{Tomatoes have come a long way from their origins as pea-sized berries due to humans breeding tomato plants to produce bigger fruit. However, favorable mutations that went along with increased fruit size and other beneficial traits do not always play well together. A study published in Cell on May 18 found that natural mutations in two important tomato genes that were selected for different purposes in breeding can cause extreme branching and reduce fruit yield when they occur in the same plant. However, the researchers have found a way to use those genes to create an improved tomato plant that grows a larger number of tomatoes.}

One of the two genes is ancient, dating back to when Native Americans in South and Central America domesticated the tomato plant more than 8,000 years ago. That gene causes the green leafy “cap” on top of tomato fruits to grow larger, the researchers found. The other gene, called Jointless2, is a 20th-century mutant, which results in a smoother stem connected to the fruit and a firmer attachment to the plant. Jointless2 is particularly sought after because it makes tomatoes easier to harvest, but the presence of both mutations in one plant causes the branches that make the flowers (and later, fruit) — known botanically as “inflorescences” — to branch wildly into patterns that look “a bit like a broom.”

“On the surface, you would think that’s great because more branches on each infloresence means more flowers, which would mean more fruits; but in fact, more branches and flowers doesn’t always translate to more fruits,” says senior author Zachary Lippman, a plant geneticist at Cold Spring Harbor Laboratory. “In order to make those fruits, the plant has to pump a lot of resources into the young fruits as they start to grow. But plant can’t handle that imbalance of having too many fruits, so the fertility is quite low.” In other words, highly branched tomato plants end up producing fewer tomatoes.

However, Lippman and his colleagues thought that there might be advantages to having low levels of branching, such that the “weak branching” plant would have more flowers than a non-branching plant but not so many that the tomatoes fail to grow. They decided to investigate the genes behind flower-bearing branches and their growth patterns.

First, the team discovered genes that caused “strong branching” mutants. They found mutations in two closely related genes, both of which play a role in initiating flower growth by turning genes on and off in plant stem cells. One of the genes, Jointless2, was already well known in tomato genetics circles, but the second gene’s function was unknown. To find out what the gene did without Jointless2 around, the researchers used CRISPR “gene editing” to create a tomato with a mutation in the mystery gene. Those mutants grew larger sepals, the small leaves at the base of a flower that become a part of the little green cap on the fruits. It’s unclear what the benefit of larger sepals and a larger green cap would be, Lippman says, but the mutation is present in more than 85% of modern tomatoes, meaning that it’s hard to breed a jointless tomato without running the risk of extreme branching.

“In the 1970s, breeders wanted to use Jointless2 so much that they said, ‘We’re going to find a way to use the genetics to our advantage, and we’re going to find other genes to suppress the branching.’ So they knew they had this extreme branching, but they didn’t know which gene was mutated,” says Lippman. “Their goal was to suppress the branching, to bring it back to the unbranched state, which is what you see in the grocery store with tomatoes on the vine. And they achieved it. They achieved it in many cases, but not all. In so doing, we feel that they have missed an opportunity to achieve weak branching, to tune the architecture in such a way that you can get a benefit.”

With the newly identified branch-driving genes in hand, the researchers were able to use natural mutations and CRISPR to engineer several different tomato plants with varying degrees of inflorescence branching, including one with “weak branching” but high fruit yield. Lippman hopes that the results from this study can be useful not only for tomato breeders, but for other crops, as well. Tomatoes are in the same genus as potatoes and eggplants (as well as poisonous Nightshades). They are also in the same family as tobacco and bell peppers. Some of these genes may also be important for those crops, and the principles behind the experiment may be applicable to distantly related plants, too.

“The more we understand about basic plant biology, basic mechanisms of plant growth, and plant development, the more we have at our fingertips the knowledge and tools to rework the system or tune the system and exploit the system,” says Lippman. “Even when we find negative mutations, we can exploit that knowledge and turn them into a positive.”

Source:Science Daily

{Among the hundreds of species of damselfish, only a few protect and care for their young; a newly discovered species raises the number from three to four}

The vast majority of coral reef fish produce large numbers of young that disperse into the ocean as larvae, drifting with the currents before settling down on a reef. Giacomo Bernardi, a professor of ecology and evolutionary biology at UC Santa Cruz, studies reef fish that buck this trend and keep their broods on the reef, protecting the young until they are big enough to fend for themselves.

On a recent trip to the Philippines, Bernardi and his graduate students discovered a new species of damselfish that exhibits this unusual parental care behavior. Out of about 380 species of damselfish, only three brood-guarding species were known prior to this discovery. Bernardi’s team had gone to the Philippines to study two of them, both in the genus Altrichthys, that live in shallow water off the small island of Busuanga. On the last day of the trip, the researchers went snorkeling in a remote area on the other side of the island from their study site.

“Immediately, as soon as we went in the water, we saw that this was a different species,” Bernardi said. “It’s very unusual to see a coral reef fish guarding its babies, so it’s really cool when you see it.”

Genetic tests on the specimens they collected confirmed that it is a new species, which the researchers named Altrichthys alelia (Alelia’s damselfish, derived from the names of Bernardi’s children, Alessio and Amalia, who helped with his field research). A paper on the new species was published May 18 in the journal ZooKeys.

Parental care dramatically improves the chances of survival for the offspring. According to Bernardi, less than one percent of larvae that disperse into the ocean survive to settle back on a reef, whereas survival rates can be as high as 35 percent for the offspring of the Altrichthys species. Yet the parental care strategy remains rare among reef fish.

“It’s a huge fitness advantage, so why don’t they all do that? There must also be a huge disadvantage,” Bernardi said.

One big disadvantage is that the young are unable to colonize new sites far from the home reef of their parents. As a result, brood-guarding species (the technical term is “apelagic” species, because they don’t have a pelagic, ocean-going phase) tend to occur in highly restricted areas, which leaves them more vulnerable to extinction.

“I suspect that species evolve this strategy regularly, and they are successful until there is some change to the local habitat, and then the whole population gets wiped out,” Bernardi said. “These are very fragile species. The Banggai cardinalfish is one that was discovered just a few years ago in a small area in Indonesia, and it’s already on the endangered species list.”

Source:Science Daily

{New research presented at this year’s European Congress on Obesity suggests that being overweight, especially from a young age, may substantially increase the lifetime risk of major depression.}

The study by Deborah Gibson-Smith from VU University Medical Center in the Netherlands and colleagues found that being overweight at age 8 or 13 was associated with more than triple the risk of developing major depression at some point in their lives, whilst carrying excess weight over a lifetime (both as a child and as an adult) quadrupled the chance of developing depression compared to only being overweight as an adult.

More than one in three children in the USA are overweight and nearly one in five children aged between 2 and 19 years are obese, according to the Centers for Disease Control and Prevention. A similar picture emerges in England where one in three 10- and 11-year-olds in their last primary school year are now overweight or obese, according to the National Child Measurement Programme.

Previous studies have shown that people who are obese are more likely to become depressed, but few have looked at the influence of early-life obesity over the long term, or the age-related effect of obesity on depression risk.

In this new study, the researchers investigated the relationship between overweight during childhood and lifetime depression in 889 participants from the population-based AGES (Age, Gene/Environment Susceptibility)-Reykjavik study (2002-06) — a follow-up study of a longitudinal study examining people born between 1907-35 and living in Reykjavik, Iceland in 1967. They also examined whether the detrimental effect of obesity on mental health is due to life-long obesity or the result of being overweight in adulthood.

Between 2002 and 2006 a random sample of surviving participants from the Reykjavik study were invited to join the AGES study. Participants, whose average age was 75 years, were assessed to see whether they had current depressive symptoms or had ever had a major depressive disorder in the past. Information about height and weight at ages 8 to 13 were obtained retospectively from school records, and from mid-life (age around 50 years) was from the data collection previously done as part of the Reykjavik study (started in 1967).

A BMI of between 25 and 29.9 was considered overweight. During the study, 39 participants were diagnosed as ever having had major depression. The data were adjusted for sex and the age at which the BMI measurements were taken.

The analysis revealed that carrying excess weight in childhood is a stronger predictor of subsequent depression than being overweight in mid-life. The researchers estimate that being overweight or obese at age 8 or 13 years is associated with a more than 4-times increased risk of lifetime major depressive disorder compared with children who were normal weight as a child but went on to become overweight as adults (a statistically significant result).

This is an observational study so no conclusions can be drawn about cause and effect. But the findings confirm earlier studies which report an increased risk of depression in young people who are obese.

The authors conclude: “Our findings suggest that some of the underlying mechanisms linking overweight or obesity to depression stem from childhood. A shared genetic risk or low self-esteem, which is frequently associated with those who do not conform to the ideal body type, could be responsible. Given the rise in adolescents’ obesity and greater influence of social media on body image, understanding the associations between childhood obesity and depression is critical.”

Source:Science Daily