Nov 05, 2018

Magazine

Feature

Counting carbon costs
• Michael Gross
Ahead of the 24^th annual global summit on climate change, science provides ever more detailed and reliable scenarios of the catastrophic damage that the ongoing man-made climate change is going to cause in the years to come. However, people with power to do something about it still don’t take much notice, and denialists even win elections.

Book reviews

Profound rumblings from the bowels of the lobster
• John C. Tuthill
In his essay ‘Consider the Lobster’, David Foster Wallace summed up the tepid state of human–lobster relations: “for practical purposes, everyone knows what a lobster is. As usual, though, there’s much more to know than most of us care about — it’s all a matter of what your interests are.”

Life’s chemical weapons
• Edmund D. Brodie III
Intellectual curiosity rises to a whole new level when the subject becomes personal. Many of us have direct experience with some kind of venom (e.g., the stings of ants and wasps, the bites of spiders, and the chemicals injected by ectoparasites such as ticks and chiggers while feeding), and this familiarity makes venoms all the more compelling as a subject. A smaller number of unfortunate victims have first-hand knowledge of the exceptionally powerful venoms of various snakes, jellyfish, and marine snails.

Essay

A changing climate for seagrass conservation?
• Richard K.F. Unsworth,
• Len J. McKenzie,
• Lina M. Nordlund,
• Leanne C. Cullen-Unsworth
Unsworth et al. discuss how a changing climate is increasing the importance of seagrass meadows necessitating a rethink of marine conservation priorities.

Q & A

Andrew J. Roger
• Andrew J. Roger
Interview with Andrew Roger, who studies the early evolutionary history of eukaryotes at Dalhousie University.

Quick guide

Sex reversal
• Ceri Weber,
• Blanche Capel
Weber and Capel discuss various aspects of sex reversal, including how it happens, why it happens in some species but not others, and whether it is adaptive.

Primer

Amphibians
• David B. Wake,
• Michelle S. Koo
Wake and Koo introduce the biology and diversity of amphibians.

Correspondence

Orangutan populations are certainly not increasing in the wild
• Erik Meijaard,
• Julie Sherman,
• Marc Ancrenaz,
• Serge A. Wich,
• Truly Santika,
• Maria Voigt
Meijaard et al. critique a 2018 report by the Indonesian government stating that orangutan populations have increased by >10%. The report contradicts recent scientific publications indicating sharp declines in all orangutan species. Collaboration between scientists and government in development and implementation of monitoring methods is advised.

Dispatches

Memory: Theta Rhythm Couples Periodic Reactivation during Memory Retrieval
• Lluís Fuentemilla
Memory retrieval involves the reactivation of memory traces distributed throughout the brain. New research suggests that these memory reactivations have an oscillatory nature and that they are coupled to preferential stages of the hippocampal theta cycle.

Cell Biology: Functional Conservation, Structural Divergence, and Surprising Convergence in the MICOS Complex of Trypanosomes
• Jeremy G. Wideman,
• Sergio A. Muñoz-Gómez
The MICOS complex is conserved across eukaryotes, but little is known about it outside the group that comprises animals and fungi. A new study finds that mitochondria of trypanosomatid parasites bear a divergent MICOS with both ancestral and derived subunits, but with conserved functions in crista development and membrane contact site formation.
Neuroscience: Memory Encoding in the Absence of Cell Firing
• Jonathon D. Crystal
New research suggests that rats can learn new spatial information in the absence of cell-firing. A small enhancement of GABAergic inhibition with a low dose of muscimol blocked cell firing but left long-term potentiation induction intact, while behaviorally it blocked memory retrieval but left memory encoding intact.

Cell Division: The Unattached Kinetochore Wears an Expansive RZZ Coat
• Aussie Suzuki,
• Dileep Varma
The Rod–Zw10–Zwilch complex localizes to kinetochores during mitosis. New studies reveal that this complex plays a critical role in driving the expansion of the outer domain of unattached kinetochores, in addition to its known role in the control of the spindle assembly checkpoint.
Charles Bonnet Syndrome: Cortical Hyperexcitability and Visual Hallucination
• Max Coltheart
Loss of foveal vision with sparing of peripheral vision, as in macular degeneration, is often associated with visual hallucinations: it has been suggested that these occur because deafferentation of neurons in regions of visual cortex results in local neuronal hyperexcitability, and new evidence supports this hypothesis.

Palaeontology: Many Babies or Bigger Brains?
• Hans-Dieter Sues
A cynodont from the Early Jurassic reveals unexpectedly large litters in these early mammal relatives, supporting the hypothesis that an increase in brain size was connected to smaller litters during the early evolution of mammals.
Cognitive Neuroscience: Functional Specialization in Human Cerebellum
• Michael A. Silver
A new brain imaging study reveals that the human cerebellum contains a region that represents visual space that is dissociable from a region displaying visual memory-related activity, with both regions exhibiting precise functional coupling with corresponding cerebral cortical areas.

Neuroenergetics: Astrocytes Have a Sweet Spot for Glucose
• Luc Pellerin
Astrocytes are polarized cells that are known to take up glucose while delivering lactate, not glucose, for neuronal use. A new study suggests how astrocytes could facilitate glucose uptake, storage and funneling at energy-requiring sites through a privileged intracellular route.

Plant Development: Adding HAM to Stem Cell Control
• Sascha Biedermann,
• Thomas Laux
The stem cell niche of the shoot meristem is stably maintained despite a rapidly changing cellular context. Recent papers reveal a mechanism controlling the spatial patterning of the stem cell niche that prevents its self-termination.

Symbiosis: High-Carb Diet of Reef Corals as Seen from Space
• Jörg Wiedenmann,
• Cecilia D’Angelo
High levels of phytoplankton visible in satellite imagery are correlated with an increased uptake of carbon compounds by corals. This suggests that corals rely less on carbon production by photosynthetic symbionts when other resources are plentiful, and that the changes in the acquisition mode of carbon can be inferred by remote-sensing techniques.

Review

Towards a Unified Model of SMC Complex Function
• Markus Hassler,
• Indra A. Shaltiel,
• Christian H. Haering
SMC proteins organize the structure of chromatin fibers and play an important function in gene expression and chromosome segregation, among other processes. Hassler et al., in this review, attempt to construct a model explaining the mechanism of action of these proteins.

Articles

Gradients in Primary Production Predict Trophic Strategies of Mixotrophic Corals across Spatial Scales
• Michael D. Fox,
• Gareth J. Williams,
• Maggie D. Johnson,
• Veronica Z. Radice,
• Brian J. Zgliczynski,
• Emily L.A. Kelly,
• Forest L. Rohwer,
• Stuart A. Sandin,
• Jennifer E. Smith
How mixotrophic corals balance autotrophic and heterotrophic nutrition in relation to food availability is unknown. Fox et al. demonstrate that satellite estimates of nearshore primary production predict the trophic ecology of reef-building corals at regional and global scales. In more productive regions, some corals are consistently more heterotrophic.

Topographic Cortico-cerebellar Networks Revealed by Visual Attention and Working Memory
• James A. Brissenden,
• Sean M. Tobyne,
• David E. Osher,
• Emily J. Levin,
• Mark A. Halko,
• David C. Somers
Brissenden et al. demonstrate precise cerebellar contributions to visual cognitive processing and establish the existence of two cortico-cerebellar subnetworks that support different aspects of visuospatial cognition. This topographic specificity suggests that fine-grained cortico-cerebellar loops play a prominent role in cognitive processing.

The Roles of Introgression and Climate Change in the Rise to Dominance of Acropora Corals
• Yafei Mao,
• Evan P. Economo,
• Noriyuki Satoh
Mao et al. show that a major introgression event as well as recurrent gene flow across Acropora coral species and Acropora lineages profited from climate-driven mass extinctions in the Plio-Pleistocene, indicating that introgression and ecological opportunity (from climate-driven mass extinction) play important roles in the adaptive radiation of Acropora.

An Optimal Oscillatory Phase for Pattern Reactivation during Memory Retrieval
• Casper Kerrén,
• Juan Linde-Domingo,
• Simon Hanslmayr,
• Maria Wimber
Kerrén et al. show that memory reinstatement, as detected by a time-resolved pattern classifier, fluctuates at a low frequency and is modulated by theta phase. The results provide strong evidence for theta phase encoding-retrieval models in the human brain and thus bridge an important gap between computational, rodent, and human work.

The Diverged Trypanosome MICOS Complex as a Hub for Mitochondrial Cristae Shaping and Protein Import
• Iosif Kaurov,
• Marie Vancová,
• Bernd Schimanski,
• Lawrence Rudy Cadena,
• Jiří Heller,
• Tomáš Bílý,
• David Potěšil,
• Claudia Eichenberger,
• Hannah Bruce,
• Silke Oeljeklaus,
• Bettina Warscheid,
• Zbyněk Zdráhal,
• André Schneider,
• Julius Lukeš,
• Hassan Hashimi
The mitochondrial contact site and cristae organizing system (MICOS) is a conserved feature of mitochondria. Kaurov et al. identify and characterize MICOS proteins outside of opisthokonts in the kinetoplastid parasite Trypanosoma brucei. TbMICOS plays a conserved role in mitochondrial cristae shaping and harbors several unique features as well.

Self-Assembly of the RZZ Complex into Filaments Drives Kinetochore Expansion in the Absence of Microtubule Attachment
• Cláudia Pereira,
• Rita M. Reis,
• José B. Gama,
• Ricardo Celestino,
• Dhanya K. Cheerambathur,
• Ana X. Carvalho,
• Reto Gassmann
Unattached kinetochores are known to expand their outermost layer to accelerate spindle assembly. Pereira, Reis, et al. present evidence suggesting that self-assembly of the Rod-Zw10-Zwilch complex into filaments, driven by the Rod subunit that is structurally related to membrane coat proteins, underlies the adaptive change in kinetochore size.

Reports

Distinct Roles of RZZ and Bub1-KNL1 in Mitotic Checkpoint Signaling and Kinetochore Expansion
• Jose-Antonio Rodriguez-Rodriguez,
• Clare Lewis,
• Kara L. McKinley,
• Vitali Sikirzhytski,
• Jennifer Corona,
• John Maciejowski,
• Alexey Khodjakov,
• Iain M. Cheeseman,
• Prasad V. Jallepalli
Rodriguez-Rodriguez et al. identify distinct roles for Bub1, KNL1, and RZZ in SAC signaling and fibrous corona formation. They also show that BUB1-disrupted clones re-express Bub1 and regain SAC function via nonsense-associated alternative splicing, an often-overlooked transcriptional response that can limit penetrance in genome editing experiments

A New Multiple Object Awareness Paradigm Shows that Imperfect Knowledge of Object Location Is Still Knowledge
• Chia-Chien Wu,
• Jeremy M. Wolfe
Multiple object awareness (MOA) is a version of a multiple object tracking task. Wu and Wolfe show that MOA capacity is much larger than classic object tracking because it includes partial knowledge of location (“the cow is somewhere over there”). Partial knowledge that degrades over time is still useful knowledge and can guide search for a target.

Laminar Organization of Working Memory Signals in Human Visual Cortex
• Samuel J.D. Lawrence,
• Tim van Mourik,
• Peter Kok,
• Peter J. Koopmans,
• David G. Norris,
• Floris P. de Lange
Using high-field MRI, Lawrence et al. show that holding a visual item in working memory leads to top-down activation of the primary visual cortex. This activity is strongest in the agranular layers. These results provide new insights into how bottom-up and top-down signals are deployed in visual cortex.

Interspecific Gene Flow Shaped the Evolution of the Genus Canis
• Shyam Gopalakrishnan,
• Mikkel-Holger S. Sinding,
• Jazmín Ramos-Madrigal,
• Jonas Niemann,
• Jose A. Samaniego Castruita,
• Filipe G. Vieira,
• Christian Carøe,
• Marc de Manuel Montero,
• Lukas Kuderna,
• Aitor Serres,
• Víctor Manuel González-Basallote,
• Yan-Hu Liu,
• Guo-Dong Wang,
• Tomas Marques-Bonet,
• Siavash Mirarab,
• Carlos Fernandes,
• Philippe Gaubert,
• Klaus-Peter Koepfli,
• Jane Budd,
• Eli Knispel Rueness,
• Claudio Sillero,
• Mads Peter Heide-Jørgensen,
• Bent Petersen,
• Thomas Sicheritz-Ponten,
• Lutz Bachmann,
• Øystein Wiig,
• Anders J. Hansen,
• M. Thomas P. Gilbert
Gopalakrishnan et al. present evidence of pervasive gene flow among species of the genus Canis. In addition to previously known admixture events, they find evidence of gene flow from a “ghost” canid, related to the dhole, into the ancestor of the gray wolf and coyote. Further, they suggest that the African golden wolf is a species of hybrid origin.

Correlated Evolution of Two Copulatory Organs via a Single cis-Regulatory Nucleotide Change
• Olga Nagy,
• Isabelle Nuez,
• Rosina Savisaar,
• Alexandre E. Peluffo,
• Amir Yassin,
• Michael Lang,
• David L. Stern,
• Daniel R. Matute,
• Jean R. David,
• Virginie Courtier-Orgogozo
Nagy et al. identify between Drosophila species one nucleotide substitution that lies in a gene-regulatory region and that contributes to evolutionary change of two distinct copulatory organs.

Genetic Interactions between the Aurora Kinases Reveal New Requirements for AURKB and AURKC during Oocyte Meiosis
• Alexandra L. Nguyen,
• David Drutovic,
• Berta N. Vazquez,
• Warif El Yakoubi,
• Amanda S. Gentilello,
• Marcos Malumbres,
• Petr Solc,
• Karen Schindler
Nguyen et al. describe oocyte-specific functions for the three Aurora protein kinases during meiosis. The authors show, for the first time, negative inter-kinase regulation between the family members to control the localized activity of one another and that these interactions are critical for spindle integrity and gamete euploidy.

Aristaless Controls Butterfly Wing Color Variation Used in Mimicry and Mate Choice
• Erica L. Westerman,
• Nicholas W. VanKuren,
• Darli Massardo,
• Ayşe Tenger-Trolander,
• Wei Zhang,
• Ryan I. Hill,
• Michael Perry,
• Erick Bayala,
• Kenneth Barr,
• Nicola Chamberlain,
• Tracy E. Douglas,
• Nathan Buerkle,
• Stephanie E. Palmer,
• Marcus R. Kronforst
Westerman, VanKuren et al. show that butterfly wing color maps to a putative cis-regulatory element adjacent to two aristaless genes. The genes are differentially expressed between white and yellow wings and CRISPR knockout of aristaless1 causes white wings to develop yellow. Both colors have been shared among species via hybridization.

Stimulus-Driven Cortical Hyperexcitability in Individuals with Charles Bonnet Hallucinations
• David R. Painter,
• Michael F. Dwyer,
• Marc R. Kamke,
• Jason B. Mattingley
Visual hallucinations often result from age-related degeneration of the retina. Painter et al. show that these hallucinations are associated with stimulus-driven hyperexcitability within early visual cortex, providing the first evidence for an influential but untested hypothesis.

Effective Glucose Uptake by Human Astrocytes Requires Its Sequestration in the Endoplasmic Reticulum by Glucose-6-Phosphatase-β
• Margit S. Müller,
• Maxime Fouyssac,
• Colin W. Taylor
Müller et al. use targeted glucose sensors to show that glucose-6-phosphate uptake by the endoplasmic reticulum of human astrocytes and its dephosphorylation in the ER by glucose-6-phosphatase-β deliver glucose to the ER lumen and sustain cellular glucose uptake. The ER lumen may provide an intracellular protected highway for glucose transport.

Purging of Strongly Deleterious Mutations Explains Long-Term Persistence and Absence of Inbreeding Depression in Island Foxes
• Jacqueline A. Robinson,
• Caitlin Brown,
• Bernard Y. Kim,
• Kirk E. Lohmueller,
• Robert K. Wayne
Robinson et al. analyze genomic, morphological, and simulated data to understand why island foxes do not suffer from inbreeding depression and rapidly rebounded from recent bottlenecks, despite having low genomic diversity and an elevated number of deleterious alleles. They suggest purging of recessive deleterious alleles as a possible mechanism.

High Cell Diversity and Complex Peptidergic Signaling Underlie Placozoan Behavior
• Frédérique Varoqueaux,
• Elizabeth A. Williams,
• Susie Grandemange,
• Luca Truscello,
• Kai Kamm,
• Bernd Schierwater,
• Gáspár Jékely,
• Dirk Fasshauer
Placozoans are simple flat animals that lack a nervous system and muscles. Varoqueaux et al. find that the behavior of the placozoan Trichoplax is influenced by complex chemical signaling. Neuropeptides, secreted molecules produced by neurons in other animals, induce striking changes in the behavior of these neuron-less animals.

Flight in Ground Effect Dramatically Reduces Aerodynamic Costs in Bats
• L. Christoffer Johansson,
• Lasse Jakobsen,
• Anders Hedenström
Animals flying close to a surface may save energy, but measurements have been lacking. Johansson et al. find that energy savings for Daubenton’s bats during flapping flight in ground effect are twice the model predictions. The bats may also vary the wing stroke to modulate savings, challenging our understanding of how animals use ground effect.

Silent Learning
• Janine I. Rossato,
• Andrea Moreno,
• Lisa Genzel,
• Miwako Yamasaki,
• Tomonori Takeuchi,
• Santiago Canals,
• Richard G.M. Morris
It is widely believed that induction of long-term potentiation (LTP) and associated cell-firing is required for new memory formation. Rossato et al. show that memory formation can still occur provided LTP induction is intact even though cell-firing has been prevented using modest GABAergic activation. We refer to this as “silent learning.”

A Piranha-like Pycnodontiform Fish from the Late Jurassic
• Martina Kölbl-Ebert,
• Martin Ebert,
• David R. Bellwood,
• Christian Schulbert
Kölbl-Ebert et al. describe a new pycnodontiform fish, Piranhamesodon pinnatomus, from the Jurassic. It has specialized morphological features for cutting flesh, including piranha-like teeth. As a marine fish contemporary with dinosaurs, it is the oldest known flesh-eating ray-finned fish, exhibiting remarkable convergent evolution with piranhas.