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Dopamine Signaling in the Suprachiasmatic Nucleus Enables Weight Gain Associated with Hedonic Feeding

Thu, 01/02/2020 - 00:00
Palatable diets rich in fat and sugar incentivize overeating, which leads to obesity. Grippo and Tang et al. discover a unique role for dopamine signaling in the central circadian clock that promotes overconsumption outside of mealtimes.

Single-Neuron Representations of Spatial Targets in Humans

Thu, 01/02/2020 - 00:00
Tsitsiklis et al. record single-unit activity from epilepsy patients during spatial navigation. They find that the firing rates of MTL neurons vary with the locations of spatial targets, heading direction, and serial position. This suggests that the human MTL represents multiple types of spatiotemporal information to support spatial cognition.

Galanin Signaling in the Brain Regulates Color Pattern Formation in Zebrafish

Thu, 01/02/2020 - 00:00
Eskova et al. show that the neuropeptide galanin functions in the zebrafish brain to regulate peripheral thyroid hormone levels. Mutations in either galanin or galr1A, one of its receptors, lead to elevated levels of T4 thyroid hormone resulting in an easily visible pigmentation phenotype due to impaired interactions between the pigment cells.

An Ancient and Eroded Social Supergene Is Widespread across Formica Ants

Thu, 01/02/2020 - 00:00
Brelsford et al. show that a supergene underlying social structure in the Alpine silver ant (Formica selysi) is polymorphic and associated with sociality in 14 other Formica species. Across species, small supergene regions harbor consistent genetic polymorphisms, suggesting an ancient origin with ongoing rare recombination.

Between-Group Competition Impacts Reproductive Success in Wild Chimpanzees

Thu, 01/02/2020 - 00:00
Lemoine et al. use long-term data on four neighboring groups of wild chimpanzees and show that between-group competition, expressed by a novel index of neighbor pressure and a group’s competitive ability, reduces female reproductive success. This suggests that between-group competition represents a relevant selective pressure in territorial species.

Extraocular Vision in a Brittle Star Is Mediated by Chromatophore Movement in Response to Ambient Light

Thu, 01/02/2020 - 00:00
Sumner-Rooney et al. report extraocular vision in a brittle star, Ophiocoma wendtii. Visual behavior is absent in O. pumila, despite its similar photoreceptor networks, as well as dark-adapted O. wendtii. The authors propose that chromatophores provide screening pigment in O. wendtii, conferring vision to a dispersed photoreceptor system.

Comparison of Independent Evolutionary Origins Reveals Both Convergence and Divergence in the Metabolic Mechanisms of Symbiosis

Thu, 01/02/2020 - 00:00
Sørensen et al. compare multiple independent evolutionary origins of Paramecium-Chlorella symbiosis to reveal the underpinning metabolic mechanisms. Although the independent origins use a convergent nutrient exchange, they have diverged in traits linked to photosynthesis, which could mediate host-symbiont specificity in nature.

Medicago-Sinorhizobium-Ralstonia Co-infection Reveals Legume Nodules as Pathogen Confined Infection Sites Developing Weak Defenses

Thu, 01/02/2020 - 00:00
Legume plants form root nodules, which host massive numbers of beneficial bacteria. Benezech et al. show that the symbiotic organs are vulnerable to infection by pathogen and that their defense ability is reduced. However, pathogens encounter confinement in the nodules, which prevents them spreading to non-symbiotic parts of the plant.

Patterns of Hybrid Seed Inviability in the Mimulus guttatus sp. Complex Reveal a Potential Role of Parental Conflict in Reproductive Isolation

Thu, 12/26/2019 - 00:00
Genomic conflict may play a central role in speciation. Coughlan et al. find that parental conflict may play a role in the evolution of hybrid seed inviability between Mimulus guttatus and a newly discovered species complex M. decorus. Differences in conflict between these lineages may stem from demographic or life history differences.

Cortical Interactions between Prosthetic and Natural Vision

Thu, 12/26/2019 - 00:00
Retinal prosthesis in AMD patients provides electrical stimulation to the central retina, whereas the peripheral healthy retina responds naturally to light. Arens-Arad et al. characterize the cortical interactions between prosthetic and natural vision and find many similarities to natural visual processesing.

Mid-Devonian Archaeopteris Roots Signal Revolutionary Change in Earliest Fossil Forests

Thu, 12/19/2019 - 00:00
Using data from a Middle Devonian fossil soil, Stein et al. report root systems from the earliest intact forest to date, including cladoxylopsids, possibly stigmarians and Archaeopteris. Striking seed plant-like features of the latter indicate a special role for this clade in the profound changes in Earth global systems that took place at that time.

Mice Reach Higher Visual Sensitivity at Night by Using a More Efficient Behavioral Strategy

Thu, 12/19/2019 - 00:00
Koskela et al. unravel the impact of diurnal rhythm on single-photon detection from retinal circuits to behavior. Surprisingly, mice reach higher sensitivity at night even if the relevant retinal ganglion cells do not show diurnal differences. Mice employ a better search strategy associated with more efficient higher-order processing at night.

Deconstructing Hunting Behavior Reveals a Tightly Coupled Stimulus-Response Loop

Thu, 12/19/2019 - 00:00
Behavioral sequences are shaped by an animal’s interaction with its environment. Mearns et al. find that, during hunting, zebrafish larvae adaptively interact with their prey through continuous integration of visual information. When prey reach a precise location in the binocular visual field, larvae perform a stereotyped strike maneuver.

Probabilistic Models of Larval Zebrafish Behavior Reveal Structure on Many Scales

Thu, 12/19/2019 - 00:00
Johnson et al. use a moving camera system to observe naturalistic larval zebrafish behavior and develop probabilistic models to predict and simulate behavioral sequences. Their simulations capture behavioral dynamics spanning multiple timescales, from reactions to prey to hunger-dependent changes in action selection across hunting and exploration.

Patterns of Genetic Variability in Genomic Regions with Low Rates of Recombination

Thu, 12/19/2019 - 00:00
Selection reduces genetic diversity and causes a characteristic allele frequency skew at linked, neutral sites. Becher et al. show how selection on partially recessive alleles under low recombination can produce a different pattern, preserving genetic diversity and reducing skew. This is seen in humans and Drosophila.

Transition from Background Selection to Associative Overdominance Promotes Diversity in Regions of Low Recombination

Thu, 12/19/2019 - 00:00
Gilbert, Pouyet et al. find that selection against recessive deleterious mutations in regions of low recombination can lead to elevated levels of diversity, counter to the actions of background selection (BGS), and mimic balancing selection. We derive the conditions for this to occur and identify potential exemplary regions in the human genome.

Motor Behavior Selectively Inhibits Hair Cells Activated by Forward Motion in the Lateral Line of Zebrafish

Thu, 12/19/2019 - 00:00
Pichler and Lagnado show that synaptic transmission from hair cells in the lateral line of zebrafish is suppressed by fictive swimming. Suppression is much stronger in hair cells activated during forward motion, so that “push-pull” signaling of stimulus direction is blocked while external stimuli can still be detected.

Salmon face uphill struggle

Mon, 12/16/2019 - 00:00
Atlantic and Pacific salmon are ecologically important both for the marine food web and for terrestrial ecosystems and are extremely sensitive to changes affecting their river runs. Demand for human consumption is partially covered by supplementation with hatchery fish or aquaculture, but these interventions are also problematic.

The enthusiastic observer — Haeckel as artist

Mon, 12/16/2019 - 00:00
Florian Maderspacher reflects on Ernst Haeckel as an artist.

Ernst Haeckel in the history of biology

Mon, 12/16/2019 - 00:00
Georgy Levit and Uwe Hossfeld reflect on Ernst Haeckels place in the history of biology on occasion of the 100th anniversary of his death.

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