Comment on Curr Biol. 2022 Feb 7;32(3):631-644.e6.

Comment on Curr Biol. 2022 Feb 7;32(3):671-676.e5.

Comment on Curr Biol. 2022 Jan 10;32(1):97-110.e4.

Comment on Curr Biol. 2022 Feb 7;32(3):570-585.e3.

The functional evolution of ancient proteins has recently been reconstructed using molecular phylogeny, and the activity of the deduced molecules can be tested. Unfortunately, the world of small molecules escapes such 'resurrection' studies, which rely on ancestral sequence reconstruction. These studies implicitly assume that only the proteins evolve, whereas the small molecules are presumed to be identical now and in the past. Recent evolutionary analysis of biochemical pathways, however, as well as the impressive surge of metabolomics are changing this situation, and it is becoming possible to reconstruct ancient biochemical pathways. We can now begin to infer the chemical structures of key molecules that were present in the past, synthesize those molecules, and test their ability to interact with their cognate (ancient) protein partners. In this essay, we discuss the possibilities offered by these new methodological developments and provide key examples. We also highlight four principles that are important to consider when studying the evolution of small molecules: catalytic promiscuity, metabolic reconfiguration, coevolution and bidirectional interactions. These new developments call for an alliance between organic chemists and evolutionary scientists to investigate the diversity of the chemical building blocks of life, and the evolution of their biosynthetic pathways.

Coordination of bilateral movements is essential for a large variety of animal behaviors. The olivocerebellar system is critical for the control of movement, but its role in bilateral coordination has yet to be elucidated. Here, we examined whether Purkinje cells encode and influence synchronicity of left-right whisker movements. We found that complex spike activity is correlated with a prominent left-right symmetry of spontaneous whisker movements within parts, but not all, of Crus1 and Crus2. Optogenetic stimulation of climbing fibers in the areas with high and low correlations resulted in symmetric and asymmetric whisker movements, respectively. Moreover, when simple spike frequency prior to the complex spike was higher, the complex spike-related symmetric whisker protractions were larger. This finding alludes to a role for rebound activity in the cerebellar nuclei, which indeed turned out to be enhanced during symmetric protractions. Tracer injections suggest that regions associated with symmetric whisker movements are anatomically connected to the contralateral cerebellar hemisphere. Together, these data point toward the existence of modules on both sides of the cerebellar cortex that can differentially promote or reduce the symmetry of left and right movements in a context-dependent fashion.

Comment in Curr Biol. 2022 Feb 7;32(3):693-700.e5. Nature. 2022 May;605(7908):186.

Social groups often need to overcome differences in individual interests and knowledge to reach consensus decisions. Here, we combine experiments and modeling to study conflict resolution in emigrating ant colonies during binary nest selection. We find that cohesive emigration, without fragmentation, is achieved only by intermediate-sized colonies. We then impose a conflict regarding the desired emigration target between colony subgroups. This is achieved using an automated selective gate system that manipulates the information accessible to each ant. Under this conflict, we find that individuals concede their potential benefit to promote social consensus. In particular, colonies resolve the conflict imposed by a persistent minority through "majority concession," wherein a majority of ants that hold first-hand knowledge regarding the superior quality nest choose to reside in the inferior one. This outcome is unlikely in social groups of selfish individuals and emphasizes the importance of group cohesion in eusocial societies. VIDEO ABSTRACT.

Comment in Curr Biol. 2022 Feb 7;32(3):R123-R125.

Regulating how fast to learn is critical for flexible behavior. Learning about the consequences of actions should be slow in stable environments, but accelerate when that environment changes. Recognizing stability and detecting change are difficult in environments with noisy relationships between actions and outcomes. Under these conditions, theories propose that uncertainty can be used to modulate learning rates ("meta-learning"). We show that mice behaving in a dynamic foraging task exhibit choice behavior that varied as a function of two forms of uncertainty estimated from a meta-learning model. The activity of dorsal raphe serotonin neurons tracked both types of uncertainty in the foraging task as well as in a dynamic Pavlovian task. Reversible inhibition of serotonin neurons in the foraging task reproduced changes in learning predicted by a simulated lesion of meta-learning in the model. We thus provide a quantitative link between serotonin neuron activity, learning, and decision making.

Humans are remarkably proficient at finding objects within complex visual scenes. According to current theories of attention,1-3 visual processing of an object of interest is favored through the preparatory activation of object-specific representations in visual cortex.4-15 One key problem that is inherent to real-world visual search but is not accounted for by current theories is that a given object will produce a dramatically different retinal image depending on its location, which is unknown in advance. For instance, the color of the retinal image depends on the illumination on the object, its shape depends on the viewpoint, and (most critically) its size can vary by several orders of magnitude, depending on the distance to the observer. In order to benefit search, preparatory activity thus needs to incorporate contextual expectations. In the current study, we measured fMRI blood-oxygen-level-dependent (BOLD) activity in human observers while they prepared to search for objects at different distances in indoor-scene photographs. First, we established that observers instantiated preparatory object representations: activity patterns in object-selective cortex evoked during search preparation (while no objects were presented) resembled activity patterns evoked by viewing those objects in isolation. Second, we demonstrated that these preparatory object representations were systematically modulated by expectations derived from scene context: activity patterns reflected the predicted retinal image of the object at each distance (i.e., distant search evoking smaller object representations and nearby search evoking larger object representations). These findings reconcile current theories of attentional selection with the challenges of real-world vision.

Comment in Curr Biol. 2022 Feb 7;32(3):R118-R120.

Comment in Curr Biol. 2022 Feb 7;32(3):R129-R131.

During growth and morphogenesis, plant cells respond to mechanical stresses resulting from spatiotemporal changes in the cell wall that bear high internal turgor pressure. Microtubule (MT) arrays are reorganized to align in the direction of maximal tensile stress, presumably reinforcing the local cell wall by guiding the synthesis of cellulose. However, how mechanical forces regulate MT reorganization remains largely unknown. Here, we demonstrate that mechanical signaling that is based on the Catharanthus roseus RLK1-like kinase (CrRLK1L) subfamily receptor kinase FERONIA (FER) regulates the reorganization of cortical MT in cotyledon epidermal pavement cells (PCs) in Arabidopsis. Recessive mutations in FER compromised MT responses to mechanical perturbations, such as single-cell ablation, compression, and isoxaben treatment, in these PCs. These perturbations promoted the activation of ROP6 guanosine triphosphatase (GTPase) that acts directly downstream of FER. Furthermore, defects in the ROP6 signaling pathway negated the reorganization of cortical MTs induced by these stresses. Finally, reduction in highly demethylesterified pectin, which binds the extracellular malectin domains of FER and is required for FER-mediated ROP6 activation, also impacted mechanical induction of cortical MT reorganization. Taken together, our results suggest that the FER-pectin complex senses and/or transduces mechanical forces to regulate MT organization through activating the ROP6 signaling pathway in Arabidopsis.

Comment on Curr Biol. 2022 Feb 7;32(3):614-630.e5.

Comment on Curr Biol. 2022 Feb 7;32(3):559-569.e5.

Comment on Curr Biol. 2022 Feb 7;32(3):532-544.e7. Curr Biol. 2022 Feb 7;32(3):518-531.e6.

Colour is an important visual modality for many animals including insects. The flower-foraging swallowtail butterfly Papilio xuthus has spectrally acute chromatic vision using UV-, blue-, green- and red-sensitive photoreceptors1. The spectral organization of Papilio's retina is well understood but, as for other insects, how chromatic information is processed in higher order brain regions remains unclear. To identify neurons underlying color perception in Papilio, we have investigated the spectral properties of the visual inputs to the mushroom body (MB), a brain region implicated in learning and memory. By recording intracellular responses to a series of monochromatic lights, combined with dye injection, we have revealed a wide variety of spectral responses in three morphologically distinct neuron types. These heterogeneous responses are characterized by colour opponency and sharp tuning to particular wavelengths, which do not in general align with the sensitivities of the retinal photoreceptors, and presumably contribute to Papilio's acute wavelength discrimination. This finding provides new insights into the processing underlying insect colour vision.

Self-medication refers to the process by which a host suppresses or prevents the deleterious effects of parasitism and other causes of illness via behavioural means1. It has been observed across multiple animal taxa (e.g. bears, elephants, moths, starlings)2, with many case studies in great apes1,3. Although the majority of studies on self-medication in non-human primates concern the ingestion of plant parts or non-nutritional substances to combat or control intestinal parasites4, more recent examples also report topical applications of leaves or other materials (including arthropods) to skin integuments3. Thus far, however, the application of insects or insect parts to an individual's own wound or the wound of a conspecific has never been reported. Here, we report the first observations of chimpanzees applying insects to their own wounds (n = 19) and to the wounds of conspecifics (n = 3).

Interview with Joseph Heitman, who studies model and pathogenic fungi at Duke University Medical Center.

Comment in Curr Biol. 2022 Feb 7;32(3):R116-R118.

Theropod dinosaurs underwent some of the most remarkable dietary changes in vertebrate evolutionary history, shifting from ancestral carnivory1-3 to hypercarnivory4,5 and omnivory/herbivory,6-9 with some taxa eventually reverting to carnivory.10-12 The mandible is an important tool for food acquisition in vertebrates and reflects adaptations to feeding modes and diets.13,14 The morphofunctional modifications accompanying the dietary changes in theropod dinosaurs are not well understood because most of the previous studies focused solely on the cranium and/or were phylogenetically limited in scope,12,15-21 while studies that include multiple clades are usually based on linear measurements and/or discrete osteological characters.8,22 Given the potential relationship between macroevolutionary change and ontogenetic pattern,23 we explore whether functional morphological patterns observed in theropod mandibular evolution show similarities to the ontogenetic trajectory. Here, we use finite element analysis to study the mandibles of non-avialan coelurosaurian theropods and demonstrate how feeding mechanics vary between dietary groups and major clades. We reveal an overall reduction in feeding-induced stresses along all theropod lineages through time. This is facilitated by a post-dentary expansion and the development of a downturned dentary in herbivores and an upturned dentary in carnivores likely via the "curved bone effect." We also observed the same reduction in feeding-induced stress in an ontogenetic series of jaws of the tyrannosaurids Tarbosaurus and Tyrannosaurus, which is best attributed to bone functional adaptation. This suggests that this common tendency for structural strengthening of the theropod mandible through time, irrespective of diet, is linked to "functional peramorphosis" of bone functional adaptations acquired during ontogeny.

Sensing and signaling of cell wall status and dynamics regulate many processes in plants, such as cell growth and morphogenesis, but the underpinning mechanisms remain largely unknown. Here, we demonstrate that the CrRLK1L receptor kinase FERONIA (FER) binds the cell wall pectin, directly leading to the activation of the ROP6 guanosine triphosphatase (GTPase) signaling pathway that regulates the formation of the puzzle piece shape of pavement cells in Arabidopsis. The extracellular malectin domain of FER binds demethylesterified pectin in vivo and in vitro. Both loss-of-FER mutations and defects in pectin demethylesterification caused similar changes in pavement cell shape and ROP6 GTPase signaling. FER is required for the activation of ROP6 by demethylesterified pectin and physically and genetically interacts with the ROP6 activator, RopGEF14. Thus, our findings elucidate a signaling pathway that directly connects the cell wall pectin to cellular morphogenesis via the cell surface receptor FER.

Comment on Curr Biol. 2022 Feb 7;32(3):708-714.e4.

In this Quick guide, Derek Lovley introduces microbial nanowires-conductive extracellular appendages made by some bacteria and archaea.

Comment in Curr Biol. 2022 Feb 7;32(3):R126-R128.

Comment in Curr Biol. 2022 Feb 7;32(3):R138-R140.

Of all frontocortical subregions, the anterior cingulate cortex (ACC) has perhaps the most overlapping theories of function.1-3 Recording studies in rats, humans, and other primates have reported diverse neural responses that support many theories,4-12 yet nearly all these studies have in common tasks in which one event reliably predicts another. This leaves open the possibility that ACC represents associative pairing of events, independent of their overt biological significance. Sensory preconditioning13 provides an opportunity to test this. In the first phase, preconditioning, value-neutral sensory stimuli are paired (A→B). To test whether this was learned, subjects are given standard conditioning during which one of the previously neutral sensory cues is paired with a biologically meaningful outcome (B→outcome). During the final probe test, the neutral cue which was never paired with a biologically meaningful outcome is presented alone (A→) and will elicit a conditional response, suggesting that subjects had learned the associative structure during preconditioning and use that knowledge to infer presentation of the biologically relevant outcome (A→B→outcome). Inference-based responding demonstrates a fundamental property of model-based reasoning14,15 and requires learning of the associations between neutral stimuli before rewards are introduced.16-19 ACC neurons developed firing patterns that reflected the learning of sensory associations during preconditioning, even though no rewards were present. The strength of these correlates predicted rats' ability to later mobilize and use that associative information during the probe test. These results demonstrate that clear biological significance is not necessary to produce correlates of learning in ACC.

Comment on Curr Biol. 2022 Feb 7;32(3):545-558.e5.

Comment in Curr Biol. 2022 Feb 7;32(3):R116-R118.

Patients with Parkinson's disease (PD) suffer from severe sleep disorders. Pathophysiology of the basal ganglia (BG) underlies PD, and the dorsal striatum represents the major input pathway of the BG. However, the roles and mechanisms of the dorsal striatum in controlling sleep-wake cycles remain unknown. To demonstrate the contribution of dopamine D1 receptor (D1R)-positive neurons within the dorsal striatum in promoting wakefulness, we combined optogenetic manipulations and fiber photometry with electroencephalography/electromyography recording in D1R-Cre mice. As a result, optogenetic activation of striatal D1R neurons induced immediate transitions from non-rapid eye movement (NREM) sleep to wakefulness, whereas inhibition of striatal D1R neurons attenuated wakefulness by chemogenetics. Multi-channel fiber photometry recordings revealed that the activity of striatal D1R neurons synchronized with that of BG upstreams, namely the prefrontal cortex and mediodorsal thalamus, in terms of immediate increase in activity during NREM-to-wake transitions and rapid decease during wake-to-NREM transitions. Further optogenetic manipulations revealed a prominent contribution of striatal D1R neurons in control of wakefulness by upstream, corticostriatal, thalamostriatal, and nigrostriatal projections and via downstream, striato-entopeduncular, or striatonigral pathways. Taken together, our findings revealed a circuit regulating wakefulness through striatal D1R neurons. Striatal D1R neurons play an important role in controlling wakefulness by integrating the corticostriatal, thalamostriatal, and nigrostriatal projections and innervation of striato-entopeduncular or striatonigral pathways.

Comment on Curr Biol. 2022 Feb 7;32(3):701-707.e5.

Comment in Curr Biol. 2022 Feb 28;32(4):R158-R160.

Comment in Curr Biol. 2022 Feb 7;32(3):R120-R123.

Comment in Curr Biol. 2022 Feb 7;32(3):R135-R137.

Comment on Curr Biol. 2022 Feb 28;32(4):878-888.e8.

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Comment on Curr Biol. 2022 Feb 7;32(3):715-724.e4.

Comment in Nature. 2022 Feb;602(7895):18.

Comment in Curr Biol. 2022 Feb 28;32(4):R165-R167.

Legumes have evolved photosynthesis and symbiotic nitrogen fixation for the acquisition of energy and nitrogen nutrients. During the transition from heterotrophic to autotrophic growth, blue light primarily triggers photosynthesis and low soil nitrogen induces symbiotic nodulation. Whether and how darkness and blue light influence root symbiotic nodulation during this transition is unknown. Here, we show that short-term darkness promotes nodulation and that blue light inhibits nodulation through two soybean TGACG-motif-binding factors (STF1 and STF2), which are Papilionoideae-specific transcription factors and divergent orthologs of Arabidopsis ELONGATED HYPOCOTYL 5 (HY5). STF1 and STF2 negatively regulate soybean nodulation by repressing the transcription of nodule inception a (GmNINa), which is a central regulator of nodulation, in response to darkness and blue light. STF1 and STF2 are not capable of moving from the shoots to roots, and they act both locally and systemically to mediate darkness- and blue-light-regulated nodulation. We further show that cryptochromes GmCRY1s are required for nodulation in the dark and partially contribute to the blue light inhibition of nodulation. In addition, root GmCRY1s mediate blue-light-induced transcription of STF1 and STF2, and intriguingly, GmCRY1b can interact with STF1 and STF2 to stabilize the protein stability of STF1 and STF2. Our results establish that the blue light receptor GmCRY1s-STF1/2 module plays a pivotal role in integrating darkness/blue light and nodulation signals. Furthermore, our findings reveal a molecular basis by which photosensory pathways modulate nodulation and autotrophic growth through an intricate interplay facilitating seedling establishment in response to low nitrogen and light signals.

Comment in Curr Biol. 2022 Feb 28;32(4):R160-R162.

Hippocampal place cells fire at specific locations in the environment. They form a cognitive map that encodes spatial relations in the environment, including reward locations.1 As part of this encoding, dorsal CA1 (dCA1) place cells accumulate at reward.2-5 The encoding of learned reward location could vary between the dorsal and intermediate hippocampus, which differ in gene expression and cortical and subcortical connectivity.6 While the dorsal hippocampus is critical for spatial navigation, the involvement of intermediate CA1 (iCA1) in spatial navigation might depend on task complexity7 and learning phase.8-10 The intermediate-to-ventral hippocampus regulates reward-seeking,11-15 but little is known about the involvement in reward-directed navigation. Here, we compared the encoding of learned reward locations in dCA1 and iCA1 during spatial navigation. We used calcium imaging with a head-mounted microscope to track the activity of CA1 cells over multiple days during which mice learned different reward locations. In dCA1, the fraction of active place cells increased in anticipation of reward, but the pool of active cells changed with the reward location. In iCA1, the same cells anticipated multiple reward locations. Our results support a model in which the dCA1 cognitive map incorporates a changing population of cells that encodes reward proximity through increased population activity, while iCA1 provides a reward-predictive code through a dedicated subpopulation. Both of these location-invariant codes persisted over time, and together they provide a dual hippocampal reward location code, assisting goal-directed navigation.16,17.

Comment in Curr Biol. 2022 Feb 28;32(4):R168-R170. Trends Plant Sci. 2022 Sep;27(9):840-842.

Comment in Curr Biol. 2022 Feb 28;32(4):R170-R173.

Comment in Lab Anim (NY). 2022 Apr;51(4):99.

Comment on Curr Biol. 2022 Feb 28;32(4):775-782.e4.

Comment on Curr Biol. 2022 Feb 28;32(4):927-933.e5.

Many marine animals migrate between foraging areas and reproductive sites, often timing the return migration with extreme precision. In theory, the decision to return should reflect energy acquisition at foraging areas, energetic costs associated with transit, and timing arrival for successful reproduction. For long-distance migrations to be successful, animals must integrate 'map' information to assess where they are relative to their reproductive site as well as 'calendar' information to know when to initiate the return migration given their distance from home1. Elephant seals, Mirounga angustirostris, migrate thousands of kilometers from reproductive sites to open ocean foraging areas (Figure 1A), yet return within a narrow window of time to specific beaches2. Each year, pregnant female elephant seals undertake a ∼240-day, 10,000 km foraging migration across the Northeast Pacific Ocean before returning to their breeding beaches, where they give birth 5 days after arriving2. We found that the seals' abilities to adjust the timing of their return migration is based on the perception of space and time, which further elucidates the mechanisms behind their astonishing navigational feats3.

Viruses infect virtually all forms of cellular life, and fungi are no exception. Knowledge regarding the diverse fungal viruses, or mycoviruses, including their genome structures, host ranges, and phenotypic effects, is growing at a fast pace. Mycovirus research has been stimulated by the idea that they could be an effective tool for biocontrol of fungal pathogens. In many cases, mycoviruses are known to reduce the growth rate of their host and/or reduce their virulence. This observation, however, creates a paradox as most mycoviruses are predominately transmitted vertically, which, according to theoretical predictions, should select for more mutualistic interactions. It is possible, therefore, that widespread mutualism between mycoviruses and their hosts has been overlooked. To properly weaponize mycoviruses as biocontrol agents, a better understanding of their basic biology, including transmission modes and molecular mechanisms of parasitism, is needed. In this primer we highlight what is known about the types of viruses that have been detected in fungi and their phenotypic effects. We pay special attention to three well-studied models - the hypovirulence-causing viruses (hypoviruses or Hypoviridae) of the chestnut blight fungus, the Sclerotinia sclerotiorum ssDNA virus SsHADV-1, and the killer viruses of Saccharomyces cerevisiae - and highlight avenues for further exploration.

Interview with Toby Kiers, who studies plant-fungus networks and the evolution of cheating in nature at Vrije Universiteit Amsterdam.

Comment in Trends Parasitol. 2022 May;38(5):347-348.

A breeding colony of notothenioid icefish (Neopagetopsis ionah, Nybelin 1947) of globally unprecedented extent has been discovered in the southern Weddell Sea, Antarctica. The colony was estimated to cover at least ∼240 km2 of the eastern flank of the Filchner Trough, comprised of fish nests at a density of 0.26 nests per square meter, representing an estimated total of ∼60 million active nests and associated fish biomass of >60,000 tonnes. The majority of nests were each occupied by 1 adult fish guarding 1,735 eggs (±433 SD). Bottom water temperatures measured across the nesting colony were up to 2°C warmer than the surrounding bottom waters, indicating a spatial correlation between the modified Warm Deep Water (mWDW) upflow onto the Weddell Shelf and the active nesting area. Historical and concurrently collected seal movement data indicate that this concentrated fish biomass may be utilized by predators such as Weddell seals (Leptonychotes weddellii, Lesson 1826). Numerous degraded fish carcasses within and near the nesting colony suggest that, in death as well as life, these fish provide input for local food webs and influence local biogeochemical processing. To our knowledge, the area surveyed harbors the most spatially expansive continuous fish breeding colony discovered to date globally at any depth, as well as an exceptionally high Antarctic seafloor biomass. This discovery provides support for the establishment of a regional marine protected area in the Southern Ocean under the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) umbrella. VIDEO ABSTRACT.

Growth and division are central to cell size. Bacteria achieve size homeostasis by dividing when growth has added a constant size since birth, termed the adder principle, by unknown mechanisms.1,2 Growth is well known to be regulated by guanosine tetraphosphate (ppGpp), which controls diverse processes from ribosome production to metabolic enzyme activity and replication initiation and whose absence or excess can induce stress, filamentation, and small growth-arrested cells.3-6 These observations raise unresolved questions about the relation between ppGpp and size homeostasis mechanisms during normal exponential growth. Here, to untangle effects of ppGpp and nutrients, we gained control of cellular ppGpp by inducing the synthesis and hydrolysis enzymes RelA and Mesh1. We found that ppGpp not only exerts control over the growth rate but also over cell division and thus the steady state cell size. In response to changes in ppGpp level, the added size already establishes its new constant value while the growth rate still adjusts, aided by accelerated or delayed divisions. Moreover, the magnitude of the added size and resulting steady-state birth size correlate consistently with the ppGpp level, rather than with the growth rate, which results in cells of different size that grow equally fast. Our findings suggest that ppGpp serves as a key regulator that coordinates cell size and growth control.

Comment in Nat Rev Microbiol. 2022 Mar;20(3):126. Curr Biol. 2022 Feb 28;32(4):R178-R180.

Two major environmental challenges of our time are responding to climate change and reversing biodiversity decline. Interventions that simultaneously tackle both challenges are highly desirable. To date, most studies aiming to find synergistic interventions for these two challenges have focused on protecting or restoring vegetation and soils but overlooked how conservation or restoration of large wild animals might influence the climate mitigation and adaptation potential of ecosystems. However, interactions between large animal conservation and climate change goals may not always be positive. Here, we review wildlife conservation and climate change mitigation in terrestrial and marine ecosystems. We elucidate general principles about the biome types where, and mechanisms by which, positive synergies and negative trade-offs between wildlife conservation and climate change mitigation are likely. We find that large animals have the greatest potential to facilitate climate change mitigation at a global scale via three mechanisms: changes in fire regime, especially in previously low-flammability biomes with a new or intensifying fire regime, such as mesic grasslands or warm temperate woodlands; changes in terrestrial albedo, particularly where there is potential to shift from closed canopy to open canopy systems at higher latitudes; and increases in vegetation and soil carbon stocks, especially through a shift towards below-ground carbon pools in temperate, tropical and sub-tropical grassland ecosystems. Large animals also contribute to ecosystem adaptation to climate change by promoting complexity of trophic webs, increasing habitat heterogeneity, enhancing plant dispersal, increasing resistance to abrupt ecosystem change and through microclimate modification.

Eve Marder and Shimon Marom argue that, while we celebrate the remarkable new technologies and their ability to generate new knowledge, we mourn a concurrent loss of knowledge and expertise.

Separation of respiratory and digestive tracts in the mammalian pharynx is critical for survival. Food must be kept out of the respiratory tract, and air must be directed into the respiratory tract when breathing.1 Cetaceans have the additional problem of feeding while underwater. Lunge-feeding baleen whales (rorquals) open the mouth while swimming at high speeds to engulf a volume of prey-laden water as large as their own body2 and experience tremendous forces as water floods the mouth. How the respiratory tract is protected in the pharynx during engulfment and while swallowing a massive slurry of tiny living prey remains unknown, despite its importance to survival. By dissecting adult and fetal fin whales, we determined that a large musculo-fatty structure passively seals the oropharyngeal channel. This "oral plug" is not observed in other animals, and its position indicates it must be shifted to allow swallowing; it is a part of the soft palate and can only shift posteriorly and dorsally. Elevation of the oral plug allows food transfer to the pharynx and protects the upper airways from food entry. The laryngeal inlet in the floor of the pharynx is sealed by laryngeal cartilages, and the muscular laryngeal sac moves upward into the laryngeal cavity, completely occluding the airway. The pharynx is dedicated to the digestive tract during swallowing, with no connection between upper and lower airways. These adaptations to facilitate swallowing were a critical development in the evolution of large body size in these, the largest animals on earth.

Comment in Curr Biol. 2022 Feb 28;32(4):R173-R176.

Comment on Curr Biol. 2022 Feb 28;32(4):904-910.e3.

Comment on Curr Biol. 2022 Feb 28;32(4):796-805.e4.

Andersen and Stougaard introduce the model legume Lotus japonicus.

Comment in Curr Biol. 2022 Feb 28;32(4):R176-R178.

Small-scale fisheries are vital for food security, nutrition, and livelihoods in coastal areas throughout the world's oceans.1-9 As intricately linked social-ecological systems, small-scale fisheries require management approaches that help ensure both ecological and socioeconomic sustainability.7,10-14 Given their ease of use and lucrative nature, coastal gillnet fisheries are globally ubiquitous.10,15 However, these fisheries often result in high discarded capture of non-target organisms (bycatch) that can lead to significant cascading effects throughout trophic chains16-18 and costly fisheries restrictions that result in important revenue losses in coastal communities with scarce economic alternatives.19,20 Despite these challenges, few solutions have been developed and broadly adopted to decrease bycatch in coastal gillnet fisheries, particularly in developing nations.5,21 Here we used controlled experiments along Mexico's Baja California peninsula to show that illuminating gillnets with green LED lights-an emerging technology originally developed to mitigate sea turtle bycatch-significantly reduced mean rates of total discarded bycatch biomass by 63%, which included significant decreases in elasmobranch (95%), Humboldt squid (81%), and unwanted finfish (48%). Moreover, illuminated nets significantly reduced the mean time required to retrieve and disentangle nets by 57%. In contrast, there were no significant differences in target fish catch or value. These findings advance our understanding of how artificial illumination affects operational efficiency and changes in catch rates in coastal gillnet fisheries, while illustrating the value of assessing broad-scale ecological and socioeconomic effects of species-specific conservation strategies.

Although rodents are arguably the easiest animals to use for studying brain function, relying on them as model species for translational research comes with its own set of limitations. Here, we propose sheep as a practical large animal species to use for in vivo brain function studies performed in naturalistic settings. We conducted proof-of-principle deep brain electrophysiological recording experiments using unrestrained sheep during behavioral testing. Recordings were made from cortex and hippocampus, both while sheep performed goal-directed behaviors (two-choice discrimination tasks) and across states of vigilance, including sleep. Hippocampal and cortical oscillatory rhythms were consistent with those seen in rodents and non-human primates, and included cortical alpha oscillations and hippocampal sharp wave ripple oscillations (∼150 Hz) during immobility and hippocampal theta oscillations (5-6 Hz) during locomotion. Recordings were conducted over a period of many months during which time the animals participated willingly in the experiments. Over 3,000 putative neurons were identified, including examples whose activity was modulated by task, speed of locomotion, spatial position, reward and vigilance states, and one whose firing rate was potentially modulated by the sight of the investigator. Together, these experiments demonstrate that sheep are excellent experimental animals to use for longitudinal studies requiring a large-brained mammal and/or large-scale recordings across distributed neuronal networks. Sheep could be used safely for studying not only neural encoding of decision-making and spatial-mapping in naturalistic environments outside the confines of the traditional laboratory but also the neural basis of both intra- and inter-species social interactions.

Comment in Curr Biol. 2022 Feb 28;32(4):R162-R165.

Traditionally, paleontologists have relied on the morphological features of bones and teeth to reconstruct the evolutionary relationships of extinct animals.1 In recent decades, the analysis of ancient DNA recovered from macrofossils has provided a powerful means to evaluate these hypotheses and develop novel phylogenetic models.2 Although a great deal of life history data can be extracted from bones, their scarcity and associated biases limit their information potential. The paleontological record of Beringia3-the unglaciated areas and former land bridge between northeast Eurasia and northwest North America-is relatively robust thanks to its perennially frozen ground favoring fossil preservation.4,5 However, even here, the macrofossil record is significantly lacking in small-bodied fauna (e.g., rodents and birds), whereas questions related to migration and extirpation, even among well-studied taxa, remain crudely resolved. The growing sophistication of ancient environmental DNA (eDNA) methods have allowed for the identification of species within terrestrial/aquatic ecosystems,6-12 in paleodietary reconstructions,13-19 and facilitated genomic reconstructions from cave contexts.8,20-22 Murchie et al.6,23 used a capture enrichment approach to sequence a diverse range of faunal and floral DNA from permafrost silts deposited during the Pleistocene-Holocene transition.24 Here, we expand on their work with the mitogenomic assembly and phylogenetic placement of Equus caballus (caballine horse), Bison priscus (steppe bison), Mammuthus primigenius (woolly mammoth), and Lagopus lagopus (willow ptarmigan) eDNA from multiple permafrost cores spanning the last 40,000 years. We identify a diverse metagenomic spectra of Pleistocene fauna and identify the eDNA co-occurrence of distinct Eurasian and American mitogenomic lineages.

In nature, plant-insect interactions occur in complex settings involving multiple trophic levels, often with multiple species at each level.1 Herbivore attack of a host plant typically dramatically alters the plant's odor emission in terms of concentration and composition.2,3 Therefore, a well-adapted herbivore should be able to predict whether a plant is still suitable as a host by judging these changes in the emitted bouquet. Although studies have demonstrated that oviposition preferences of successive insects were affected by previous infestations,4,5 the underlying molecular and olfactory mechanisms remain unknown. Here, we report that tobacco hawkmoths (Manduca sexta) preferentially oviposit on Jimson weed (Datura wrightii) that is already infested by a specialist, the three-lined potato beetle (Lema daturaphila). Interestingly, the moths' offspring do not benefit directly, as larvae develop more slowly when feeding together with Lema beetles. However, one of M. sexta's main enemies, the parasitoid wasp Cotesia congregata, prefers the headspace of M. sexta-infested plants to that of plants infested by both herbivores. Hence, we conclude that female M. sexta ignore the interspecific competition with beetles and oviposit deliberately on beetle-infested plants to provide their offspring with an enemy-reduced space, thus providing a trade-off that generates a net benefit to the survival and fitness of the subsequent generation. We identify that α-copaene, emitted by beetle-infested Datura, plays a role in this preference. By performing heterologous expression and single-sensillum recordings, we show that odorant receptor (Or35) is involved in α-copaene detection.

Comment on Curr Biol. 2022 Feb 28;32(4):735-748.e10.