Current Biology最新文献

Predation is an important driver of species-level change in modern and fossil ecosystems, often through selection for defensive phenotypes in prey responding to predation pressures over time.^{1,2,3,4,5,6,7,8} Records of changes in shell morphology and injury patterns in biomineralized taxa are ideal for demonstrating such adaptive responses.^9,10,11 The rapid increase in diversity and abundance of biomineralizing organisms during the early Cambrian is often attributed to predation and an evolutionary arms race.^{12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27} A Cambrian arms race is typically discussed on a macroevolutionary scale, particularly in the context of escalation.^12,27,28,29 Despite abundant fossils demonstrating early Cambrian predation, empirical evidence of adaptive responses to predations is lacking. To explore the Cambrian arms race hypothesis, we assessed a large sample of organophosphatic sclerites of the tommotiid Lapworthella fasciculata from a lower Cambrian carbonate succession in South Australia,^30,31,32 >200 of which show holes made by a perforating predator.^33,34 Critically, the frequency of perforated sclerites increases over time, with a combination of time-series analyses and generalized linear models suggesting a positive correlation with sclerite thickness. These observations reflect a population-level adaptive response in L. fasciculata and the oldest known microevolutionary arms race between predator and prey. Propagation of such interactions across early Cambrian ecosystems likely resulted in the proliferation of biomineralizing taxa with enhanced defenses, illustrating the importance of predation as a major ecological driver of early animal evolution.^12,14,20,35.

Metazoan parasites have played a major role in shaping innate immunity in animals. Insect hosts and parasitoid wasps are excellent models for illuminating how animal innate immune systems have evolved to neutralize these enemies. One such strategy relies on symbioses between insects and intracellular bacteria that express phage-encoded toxins. In some cases, the genes that encode these toxins have been horizontally transferred to the genomes of the insects. Here, we used genome editing in Drosophila melanogaster to recapitulate the evolution of two toxin genes-cytolethal distending toxin B (cdtB) and apoptosis inducing protein of 56kDa (aip56)-that were horizontally transferred likely from phages of endosymbiotic bacteria to insects millions of years ago. We found that a cdtB::aip56 fusion gene (fusionB), which is conserved in D. ananassae subgroup species, dramatically promoted fly survival and suppressed parasitoid wasp development when heterologously expressed in D. melanogaster immune tissues. We found that FusionB was a functional nuclease and was secreted into the host hemolymph where it targeted the parasitoid embryo's serosal tissue. Although the mechanism of toxicity remains unknown, when expressed ubiquitously, fusionB resulted in delayed development of late-stage fly larvae and eventually killed pupating flies. These results point to the salience of regulatory constraint in mitigating autoimmunity during the domestication process following horizontal transfer. Our findings demonstrate how horizontal gene transfer can instantly provide new, potent innate immune modules in animals.

In the open ocean, achieving camouflage is complicated by the fact that the downwelling light is generally much brighter than the upwelling light, which means that any object, even if its ventral surface is white due to countershading, will appear as a dark silhouette when viewed from below.^1,2,3 To overcome this, many marine species employ counterillumination, whereby light is emitted from photophores on their ventral surface to replace the downwelling light blocked by their body.^4,5,6 However, only a single behavioral study has tested the efficacy of counterillumination as an anti-predation strategy.⁷ Counterillumination is predicted to be particularly useful against predators that have poor visual acuity and lack color vision,⁸ like the Great White shark (Carcharodon carcharias), the species responsible for most human shark-bite fatalities globally.⁹ Here, we take inspiration from nature to show that counterillumination can prevent Great White sharks from attacking artificial seal decoys. Using seal decoys fitted with LED lights and towed behind a boat, we explored the efficiency of different light configurations on the deterrence effect, showing that visual shape and motion cues are critical for prey recognition by Great White sharks. Counterillumination that is brighter than the background is most effective in deterring sharks, implying that, in this context, counterillumination works through disruptive camouflage rather than background matching. Our results reveal the importance of a dark silhouette against a lighter background in predatory behavior in Great White sharks and that altering the silhouette may form the basis of new non-invasive shark deterrent technology to protect human life. VIDEO ABSTRACT.

Adult social play is a universal human trait, promoting the tolerance, bonding, cooperation, and collective action that sustain our large and complex societies.^1,2 Play serves as a conduit for transmitting positive emotions, thereby stimulating psychological resilience to stressors and facilitating the positive intent and trust^3,4,5,6 essential for cooperation emergence. In contrast, non-human adult social play is considered rare, and its role in cooperation remains unknown. We address this gap by studying the play behavior of 57 adult chimpanzees (Pan troglodytes) in Taï National Park, Côte d'Ivoire, where adult social play and collective action regularly occur. We show that adult female and male chimpanzees play more during times of increased mate competition (with males mainly playing with immatures) and with adult partners they had recent disputes with, highlighting the role of play in regulating social tension that can undermine cooperation. Chimpanzees also preferred playing with adult partners with whom they share strong affiliative bonds, aligning with the idea that play is associated with social familiarity and trust. Finally, adult chimpanzees were more likely to play before collectively defending their territory against outsiders and hunting monkeys. Those who played together were subsequently more likely to collaborate, reinforcing the notion that the positive feedback signaled via play can facilitate cooperation.⁵ Our findings demonstrate the sustained significance of adult social play throughout the chimpanzee lifespan, providing valuable insights into the evolution of adult social play and its societal functions, from diffusing tension to supporting social bonds and collective action.

Mammalian visual functions rely on distributed processing across interconnected cortical and subcortical regions. In higher-order visual areas (HVAs), visual features are processed in specialized streams that integrate feedforward and higher-order inputs from intracortical and thalamocortical pathways. However, the precise circuit organization responsible for HVA specialization remains unclear. We investigated the cellular architecture of primary visual cortex (V1) and higher-order visual pathways in the mouse, focusing on their roles in shaping visual representations. Using in vivo functional imaging and neural circuit tracing, we found that HVAs preferentially receive inputs from both V1 and higher-order pathways tuned to similar spatiotemporal properties, with the strongest selectivity seen in layer 2/3 neurons. These neurons exhibit target-specific tuning and sublaminar specificity in their projections, reflecting cell-type-specific visual information flow. In contrast, HVA layer 5 pathways nonspecifically broadcast visual signals across cortical areas, suggesting a role in distributing HVA outputs. Additionally, thalamocortical pathways from the lateral posterior thalamic nucleus (LP) provide highly specific, nearly non-overlapping visual inputs to HVAs, complementing intracortical inputs and contributing to input functional diversity. Our findings suggest that the convergence of laminar and cell-type-specific pathways V1 and higher-order intracortical and thalamocortical pathways plays a key role in shaping the functional specialization and diversity of HVAs.

Maintenance of lysosomal integrity is essential for cell viability. Upon injury, lysosomes may be targeted for degradation via a selective form of autophagy known as lysophagy. The engulfment of a damaged lysosome by an autophagosome is mediated by the recruitment of adaptor proteins, including SQSTM1/p62. p62 promotes lysophagy via the formation of phase-separated condensates in a mechanism that is regulated by the heat shock protein HSP27. Here, we demonstrate a direct interaction between HSP27 and p62. We used structural modeling to predict the binding interface between HSP27 and p62 and identify several disease-associated mutations that map to this interface. We used proteomics to identify post-translational modifications of HSP27 that regulate HSP27 recruitment to stressed lysosomes, finding robust phosphorylation at several serine residues. Next, we characterized the upstream signaling mechanism leading to HSP27 phosphorylation and found that p38 mitogen-activated protein kinase (MAPK) and its effector kinase MAP kinase-activated protein kinase 2 (MK2) are activated upon lysosomal damage by the kinase mTOR and the production of intracellular reactive oxygen species (ROS). Increased ROS activates p38 MAPK, which in turn allows MK2-dependent phosphorylation of HSP27. Depletion of HSP27 or the inhibition of HSP27 phosphorylation alters the dynamics of p62 condensates on stressed lysosomes, significantly inhibiting p62-dependent lysophagy. Thus, we define a novel lysosomal quality control mechanism in which lysosomal injury triggers a p38 MAPK/MK2 signaling cascade promoting p62-dependent lysophagy. Further, this signaling cascade is activated by many cellular stressors, including oxidative and heat stress, suggesting that other forms of selective autophagy may be regulated by p38 MAPK/MK2/HSP27.

Cortical populations often exhibit changes in activity even when behavior is stable. How behavioral stability is maintained in the face of such "representational drift" remains unclear. One possibility is that some neurons are more stable than others. We examined whisker touch responses in layers 2-4 of the primary vibrissal somatosensory cortex (vS1) over several weeks in mice stably performing an object detection task with two whiskers. Although the number of touch neurons remained constant, individual neurons changed with time. Touch-responsive neurons with broad receptive fields were more stable than narrowly tuned neurons. Transitions between functional types were non-random: before becoming broadly tuned, unresponsive neurons first passed through a period of narrower tuning. Broadly tuned neurons in layers 2 and 3 with higher pairwise correlations to other touch neurons were more stable than neurons with lower correlations. Thus, a small population of broadly tuned and synchronously active touch neurons exhibits elevated stability and may be particularly important for behavior.

Visual simulation-i.e., using internal reconstructions of the world to experience potential future versions of events that are not currently happening-is among the most sophisticated capacities of the human mind. But is this ability in fact uniquely human? To answer this question, we tested monkeys on a series of experiments involving the "Planko" game, which we have previously used to evoke visual simulation in human participants. We found that monkeys were able to successfully play the game using a simulation strategy, predicting the trajectory of a ball through a field of planks while demonstrating a level of accuracy and behavioral signatures comparable with those of humans. Computational analyses further revealed that the monkeys' strategy while playing Planko aligned with a recurrent neural network (RNN) that approached the task using a spontaneously learned simulation strategy. Finally, we carried out awake functional magnetic resonance imaging while monkeys played Planko. We found activity in motion-sensitive regions of the monkey brain during hypothesized simulation periods, even without any perceived visual motion cues. This neural result closely mirrors previous findings from human research, suggesting a shared mechanism of visual simulation across species. Taken together, these findings challenge traditional views of animal cognition, proposing that nonhuman primates possess a complex cognitive landscape, capable of invoking imaginative and predictive mental experiences to solve complex everyday problems.

A new study demonstrates that honey bee nests and their contents possess front-to-back symmetry, a design characteristic arising from a proximate thermal cue with an ultimate evolutionary benefit.

Some animal lineages, such as mammals or trilobites, show particularly high rates of evolution - that is, of species origination and extinction. What makes such lineages special is not clear. A new study shows that, in fossil ammonoid cephalopods, more complex shell ornaments are associated with higher evolutionary rates.