The first insects were not yet able to smell well: Odorant receptors evolved long after insects migrated from water to land

An insect’s sense of smell is vital to its survival. Only if it can trace even tiny amounts of odor molecules is it is able to find food sources, communicate with conspecifics, or avoid enemies. According to scientists at the Max Planck Institute for Chemical Ecology, many proteins involved in the highly sensitive odor perception of insects emerged rather late in the evolutionary process. The very complex olfactory system of modern insects is therefore not an adaptation to a terrestrial environment when ancient insects migrated from water to land, but rather an adaptation that appeared when insects developed the ability to fly. The results were published in the Open Access Journal eLIFE.Many insect species employ three families of receptor proteins in order to perceive thousands of different environmental odors. Among them are the olfactory receptors. They form a functional complex with another protein, the so-called olfactory receptor co-receptor, which enables insects to smell the tiniest amounts of odor molecules in their environment very rapidly.Crustaceans and insects share a common ancestor. Since crustaceans do not have olfactory receptors, previously scientists assumed that these receptors evolved as an adaptation of prehistoric insects to a terrestrial life. This hypothesis is also based on the assumption that for the ancestors of recent insects, the ability to detect odor molecules in the air rather than dissolved in water was of vital importance.Early research on insect olfactory receptors focused entirely on insects with wings. Ewald Groe-Wilde and Bill S. …

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Mother chimps crucial for offspring’s social skills

Sep. 6, 2013 — Orphaned chimpanzees are less socially competent than chimpanzees who were reared by their mother. Researchers from the Max Planck Institute for Psycholinguistics in Nijmegen, The Netherlands, observed that orphaned chimpanzees frequently engaged in social play, but their play bouts were much shorter and resulted in aggression more often. Apparently, chimpanzee mothers endow their offspring with important social skills.It may not come as a surprise, but mother chimpanzees seem to be important for the development of social skills in young chimpanzees. “Orphaned chimpanzees had more difficulties to successfully coordinate their social play interactions,” says Edwin van Leeuwen from the Comparative Cognitive Anthropology Research Group at the Max Planck Institute for Psycholinguistics. “Since social play comprises a complex context in which signals about intentions need to be communicated, it seems that orphaned chimpanzees have missed out on valuable lessons from their mothers.”Van Leeuwen and his co-authors Innocent Mulenga and Diana Lisensky compared the play behaviour of 8 orphaned and 9 mother-reared juvenile chimpanzees at the Chimfunshi Wildlife Orphanage Trust in Zambia. In this institution the orphan chimpanzees are initially cared for by humans. As soon as they are strong enough — usually with one or two years of age — they grow up in an orphan chimp group. “The chimps in the study were between four and nine years old, so they have kind of been raising each other,” explains van Leeuwen. The orphaned and mother-reared chimpanzees matched in age and sex.Based on previous research, the scientists expected the orphaned juveniles to play less frequently and smoothly than the mother-reared chimpanzees: After all, the orphans had missed their most important caretaker throughout a sensitive socialisation period, and continued to lack a safe and facilitating social environment provided by their mothers.Contrary to their expectations, the orphaned chimpanzees engaged in social play more frequently than the mother-reared juveniles, although for shorter amounts of time. …

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Making connections in the eye: Wiring diagram of retinal neurons is first step toward mapping the human brain

Aug. 7, 2013 — The human brain has 100 billion neurons, connected to each other in networks that allow us to interpret the world around us, plan for the future, and control our actions and movements. MIT neuroscientist Sebastian Seung wants to map those networks, creating a wiring diagram of the brain that could help scientists learn how we each become our unique selves.In a paper appearing in the Aug. 7 online edition of Nature, Seung and collaborators at MIT and the Max Planck Institute for Medical Research in Germany have reported their first step toward this goal: Using a combination of human and artificial intelligence, they have mapped all the wiring among 950 neurons within a tiny patch of the mouse retina.Composed of neurons that process visual information, the retina is technically part of the brain and is a more approachable starting point, Seung says. By mapping all of the neurons in this 117-micrometer-by-80-micrometer patch of tissue, the researchers were able to classify most of the neurons they found, based on their patterns of wiring. They also identified a new type of retinal cell that had not been seen before.”It’s the complete reconstruction of all the neurons inside this patch. No one’s ever done that before in the mammalian nervous system,” says Seung, a professor of computational neuroscience at MIT.Other MIT authors of the paper are former postdoc Srinivas Turaga and former graduate student Viren Jain. The Max Planck team was led by Winfried Denk, a physicist and the Max Planck Institute’s director. Moritz Helmstaedter, a research group leader at the Max Planck Institute, is the lead author of the paper, and Kevin Briggman, a former postdoc at Max Planck, is also an author.Tracing connectionsNeurons in the retina are classified into five classes: photoreceptors, horizontal cells, bipolar cells, amacrine cells and ganglion cells. Within each class are many types, classified by shape and by the connections they make with other neurons.”Neurons come in many types, and the retina is estimated to contain 50 to 100 types, but they’ve never been exhaustively characterized. …

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Cells make costume changes for cardiac regeneration

July 11, 2013 — If the heart following a heart attack is not sufficiently supplied with blood, heart tissue dies. In adult humans, the ability to heal itself is hardly developed. Scientists from the Max Planck Institute for Heart and Lung Research in Bad Nauheim, together with U.S. colleagues, have now observed in the embryo of the zebrafish that muscle cells migrate from the undamaged atrium into the ventricle and thus significantly contribute to regeneration. This could serve as the basis for novel therapeutic approaches.If clinicians fail to reopen occluded coronary arteries after a heart attack within an appropriate time frame, the heart muscle is permanently damaged because of the long-term interrupted oxygen supply. The result is, among other things, a lifelong restriction of cardiac function, or even heart failure.For many years, scientists worldwide have been searching for ways to stimulate the regeneration of damaged heart tissue. The working group of Didier Stainier from the Max Planck Institute for Heart and Lung Research has now, together with scientists from the University of San Diego, identified in zebrafish a novel mechanism, at which muscle cells from the atrium actively migrate into damaged parts of the heart muscle in the ventricle, thus forming new ventricular tissue.For their study, the Max Planck researchers used genetically modified fish larvae, in which the targeted muscle cells of the heart chamber were destroyed by the administration of a substance. This was done at a point in time, at which the heart was already functional and active. The damage of the muscle was followed by a reduction in heart function and ventricular size.To monitor the behaviour of the different cell types, the heart muscle cells were furthermore altered by genetic engineering in such a way that cells from the atrium and the ventricle lit up differently. “In this way we were able to track, the behaviour of the individual cell types continuously in a confocal microscope,” explains Didier Stainier, the director of the department “Developmental Genetics” at the MPI.”A few hours after ablation only few red cells were remaining in the ventricle. …

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The power of imitation: Already in infancy, imitation promotes a general pro-social orientation toward others

June 27, 2013 — Being mimicked increases pro-social behaviour in adults, yet little is known about its social effect on children. Researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have now investigated whether the fact of being imitated had an influence on infants’ pro-social behaviour and on young children’s trust in another person.In one study, eighteen-month-old infants were either mimicked or not by an experimenter. Later, when this experimenter or a different adult needed help, infants who had been imitated were more likely to help spontaneously. In a second study, five- to six-year-olds interacted with one experimenter who mimicked their choices and another experimenter who made independent choices. The researchers found that the children were more likely to trust the preferences and factual claims of the experimenter who had mimicked them before. These results demonstrate that already in infancy mimicry promotes a general pro-social orientation toward others and that in young children imitation is a powerful means of social influence in development.Imitation is not only a means by which we learn from others. As adults, we routinely and automatically copy each other’s movements, postures, and facial expressions, and this has a variety of positive social consequences. After being mimicked, we behave more helpfully and generously toward others, from picking up others’ dropped belongings to giving more money to charity. Much less is known, however, about the social effects of imitation on infants and young children.Focusing on the social side of imitation, the researchers tested in a first study whether being mimicked increased pro-social behaviour in infants, as it does in adults. To this end, 48 eighteen-month-old infants were either mimicked or not by an experimenter: In the mimic condition, the experimenter immediately copied everything she saw or heard infants do. …

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Female moths use olfactory signals to choose the best egg-laying sites

June 3, 2013 — Functional calcium imaging in the antennal lobes of a female Manduca sexta moth: Different activation patterns (red spots) can be observed depending on whether the moths respond to (Z)-3-hexenyl acetate or (E)-2-hexenyl acetate. The odor of a (Z)-3-isomer or a (Z)-3 / (E)-2 ratio in favor of a (Z)-3-isomer − according to the odor bouquet of an unattacked plant − guides ovipositing Manduca females to plants that have yet been spared by herbivorous caterpillars. Copyright: Anna Späthe, MPI Chem. Ecol.Researchers at the Max Planck Institute for Chemical Ecology, Jena, Germany, discovered that the ability of Manduca sexta moths to recognize changes in the profile of volatile compounds released by plants being attacked by Manduca caterpillars allows them to lay their eggs on plants that are less likely to be attacked by insects and other predators, and to avoid competing against other caterpillars of the same species for resources. The results of field experiments and neurobiological studies were now published in the open access online journal eLIFE. (eLIFE, May 14, 2013, DOI: 10.7554/elife.00421)”Green” leaf odorsPlants have developed many different strategies to defend themselves against herbivorous animals, particularly insects. In addition to mechanical defenses such as thorns and spines, plants also produce compounds that keep insects and other herbivores at bay by acting as repellents or toxins. Some of these metabolites are produced on a continuous basis by plants, whereas others — notably compounds called green-leaf volatiles — are mainly produced once the plant has been wounded or attacked. Green-leaf volatiles — which are also responsible for the smell of freshly cut grass — have been observed to provide plants with both direct protection, by inhibiting or repelling herbivores, and indirect protection, by attracting predators of the herbivores themselves.Attracting the enemies of the herbivoresThe hawkmoth Manduca sexta lays its eggs on various plants, including tobacco and Sacred Datura plants (Datura wrightii). Once the eggs have hatched into caterpillars, they start eating the leaves of their host plant, and if present in large numbers, these caterpillars can quickly defoliate and destroy the plant. …

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