Current Biology最新文献

Brood care relies on interactions between parents and offspring. Emergence of nestlings from their nest has been hypothesized to rely on the readout by the parent of the maturational state of the young. Theoretical considerations predict a conflict: parents should push for early emergence, if possible, to reduce care demands and maximize the number of reproductive cycles, whereas offspring should delay leaving to maximize resource allocation and protection by the parents. We tested this prediction in Lamprologus ocellatus, a shell-dwelling cichlid from Lake Tanganyika. We developed a laboratory paradigm to investigate the factors influencing emergence from the shell and found that mothers ensure their young stay inside the nest until 9 days after egg laying. Emergence coincides with an inversion of larval phototactic tendency from dark-seeking to light-seeking behavior on day 9. When we experimentally created a timing conflict by introducing older larvae to a foster mother, the mother resisted the (subjectively) premature emergence of her adopted fry. Removing the mother did not alter the larval intrinsic schedule, provided fresh water was supplied inside the shell. These findings suggest that, in L. ocellatus brood care, maternal and offspring behavior is normally synchronized by independent timing mechanisms. Our findings highlight the intricate coordination of parental and offspring behavior, offering insights into the evolutionary pressures shaping brood care in cichlids and challenging the traditional view of parent-offspring conflict over emergence timing.

Microtubules (MTs) are intrinsically dynamic polymers. In neurons, staggered individual microtubules form stable, polarized acentrosomal MT arrays spanning the axon and dendrite to support long-distance intracellular transport. How the stability and polarity of these arrays are maintained when individual MTs remain highly dynamic is still an open question. Here, we visualize MT arrays in vivo in C. elegans neurons with single MT resolution. We find that the CRMP family homolog UNC-33 is essential for the stability and polarity of MT arrays in neurites. In unc-33 mutants, MTs exhibit dramatically reduced rescue after catastrophe, develop gaps in coverage, and lose their polarity, leading to trafficking defects. UNC-33 is stably anchored on the cortical cytoskeleton and forms patch-like structures along the dendritic shaft. These discrete and stable UNC-33 patches concentrate free tubulins and correlate with MT rescue sites. In vitro, purified UNC-33 preferentially associates with MT tips and increases MT rescue frequency. Together, we propose that UNC-33 functions as a microtubule-associated protein (MAP) to promote individual MT rescue locally. Through this activity, UNC-33 prevents the loss of individual MTs, thereby maintaining the coverage and polarity of MT arrays throughout the lifetime of neurons.

An emerging frontier in ecology explores how organisms integrate social information into movement behavior and the extent to which information exchange occurs across species boundaries.^1,2,3 Most migratory landbirds are thought to undertake nocturnal migratory flights independently, guided by endogenous programs and individual experience.^4,5 Little research has addressed the potential for social information exchange aloft during nocturnal migration, but social influences that aid navigation, orientation, or survival could be valuable during high-risk migration periods.^1,2,6,7,8 We captured audio of >18,000 h of nocturnal bird migration and used deep learning to extract >175,000 in-flight vocalizations of 27 species of North American landbirds.^9,10,11,12 We used vocalizations to test whether migrating birds distribute non-randomly relative to other species in flight, accounting for migration phenology, geography, and other non-social factors. We found that migrants engaged in distinct associations with an average of 2.7 ± 1.9 SD other species. Social associations were stronger among species with similar wing morphologies and vocalizations. These results suggest that vocal signals maintain in-flight associations that are structured by flight speed and behavior.^11,13,14 For small-bodied and short-lived bird species, transient social associations could play an important role in migratory decision-making by supplementing endogenous or experiential information sources.^15,16,17 This research provides the first quantitative evidence of interspecific social associations during nocturnal bird migration, supporting recent calls to rethink songbird migration with a social lens.² Substantial recent declines in bird populations^18,19 may diminish the frequency and strength of social associations during migration, with currently unknown consequences for populations.

Ochrophyta is a vast and morphologically diverse group of algae with complex plastids, including familiar taxa with fundamental ecological importance (diatoms or kelp) and a wealth of lesser-known and obscure organisms. The sheer diversity of ochrophytes poses a challenge for reconstructing their phylogeny, with major gaps in sampling and an unsettled placement of particular taxa yet to be tackled. We sequenced transcriptomes from 25 strategically selected representatives and used these data to build the most taxonomically comprehensive ochrophyte-centered phylogenomic supermatrix to date. We employed a combination of approaches to reconstruct and critically evaluate the relationships among ochrophytes. While generally congruent with previous analyses, the updated ochrophyte phylogenomic tree resolved the position of several taxa with previously uncertain placement and supported a redefinition of the classes Picophagea and Synchromophyceae. Our results indicated that the heterotrophic, plastid-lacking heliozoan Actinophrys sol is not a sister lineage of ochrophytes, as proposed recently, but rather phylogenetically nested among them, implying that it lacks a plastid due to loss. In addition, we found the heterotrophic ochrophyte Picophagus flagellatus to lack all hallmark plastid genes yet to exhibit mitochondrial proteins that seem to be genetic footprints of a lost plastid organelle. We thus document, for the first time, plastid loss in two separate ochrophyte lineages. Furthermore, by exploring eDNA data, we enrich the ochrophyte phylogenetic tree by identifying five novel uncultured class-level lineages. Altogether, our study provides a new framework for reconstructing trait evolution in ochrophytes and demonstrates that plastid loss is more common than previously thought.

In human adults, visual perception varies throughout the visual field. Performance decreases with eccentricity^1,2 and varies around polar angle. At isoeccentric locations, performance is typically higher along the horizontal than vertical meridian (horizontal-vertical asymmetry [HVA]) and along the lower than the upper vertical meridian (vertical meridian asymmetry [VMA]).^{3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23} It is unknown whether the macaque visual system, the leading animal model for understanding human vision,^24,25 also exhibits these performance asymmetries. Here, we investigated whether and how visual field asymmetries differ between these two groups. Human adults and adult macaque monkeys (Macaca nemestrina) performed a two-alternative forced choice (2AFC) motion direction discrimination task for a target presented among distractors at isoeccentric locations. Both groups showed heterogeneous visual sensitivity around the visual field, but there were striking differences between them. Human observers showed a large VMA-their sensitivity was poorest at the upper vertical meridian-a weak horizontal-vertical asymmetry, and lower sensitivity at intercardinal locations. Macaque performance revealed an inverted VMA-their sensitivity was poorest in the lower vertical meridian. The opposite pattern of VMA in macaques and humans revealed in this study may reflect adaptive behavior by increasing discriminability at locations with greater relevance for visuomotor integration. This study reveals that performance also varies as a function of polar angle for monkeys, but in a different manner than in humans, and highlights the need to investigate species-specific similarities and differences in brain and behavior to constrain models of vision and brain function.

Understanding the movements of highly mobile animals is challenging because of the many factors they must consider in their decision-making. Many seabirds, for example, are adapted to use winds to travel long distances at low energetic cost^1,2,3 but also potentially benefit from targeting specific foraging hotspots.^4,5,6 To investigate how an animal makes foraging decisions, given the inevitable trade-off between these factors, we tracked over 600 foraging trips of breeding Manx shearwaters (Puffinus puffinus; N = 218 individuals) using GPS accelerometers. By first uncovering the relationships between wind and the flapping effort put into flight, we show that shearwaters, while generally wind selective, adjust their wind selectivity, apparently balancing flight costs against the benefits of travel toward known targets. This is supported by a number of scenarios that alter the balance between maximizing flight efficiency and goal-oriented flight. First, shearwaters exhibit lower wind selectivity during homing movement when constrained to target-driven navigation toward the colony. Second, when wind speeds are low, flight costs vary little with travel direction, which shearwaters respond to by reducing wind selectivity in their outbound commutes, again favoring target-driven movement toward presumably memorized foraging areas. Finally, birds are also less wind selective during longer continuous periods of flight, presumably also associated with target-oriented movement. Our findings reveal how an animal's foraging strategy can dynamically optimize the complex trade-off between efficient travel and accessing known foraging areas, implying the incorporation of prior knowledge of the cost-benefit landscape well beyond the range of what can be detected directly.

Enhancing drought resistance through the manipulation of root system architecture (RSA) in crops represents a crucial strategy for addressing food insecurity challenges. Abscisic acid (ABA) plays important roles in drought tolerance; yet, its molecular mechanisms in regulating RSA, especially in cereal crops, remain unclear. In this study, we report a new mechanism whereby ABA mediates local auxin biosynthesis to regulate root gravitropic response, thereby controlling the alteration of RSA in response to drought in cereal crops. Under drought conditions, wild-type (WT) plants displayed a steep root angle compared with normal conditions, while ABA biosynthetic mutants (mhz4, mhz5, osaba1, and osaba2) showed a significantly shallower crown root angle. Gravitropic assays revealed that ABA biosynthetic mutants have reduced gravitropic responses compared with WT plants. Hormone profiling analysis indicated that the mhz5 mutant has reduced auxin levels in root tips, and exogenous auxin (naphthaleneacetic acid [NAA]) application restored its root gravitropic defects. Consistently, auxin reporter analysis in mhz5 showed a reduced auxin gradient formation in root epidermis during gravitropic bending response compared with WT plants. Furthermore, NAA, rather than ABA, was able to rescue the compromised gravitropic response in the auxin biosynthetic mutant mhz10-1/tryptophan amino transferase2 (ostar2). Additionally, the maize ABA biosynthetic mutant viviparous5 (vp5) also showed gravitropic defects and a shallower seminal root angle than WT plants, which were restored by external auxin treatment. Collectively, we suggest that ABA-induced auxin synthesis governs the root gravitropic machinery, thereby influencing root angle in rice, maize, and possibly other cereal crops.

"Saber teeth"-elongate, blade-like canines-are a classic example of convergence, having evolved repeatedly throughout mammalian history. Within canine teeth, there is a trade-off between the aspects of shape that improve food fracture and those that increase tooth strength. Optimal morphologies strike a balance between these antagonistic functional criteria. The extreme saber-tooth morphology is thought to confer functional advantage for more specialized predatory adaptations and optimization; however, the adaptive bases underpinning their evolution remain unclear. To determine whether saber-tooth shape reflects selection for functionally optimal morphologies, we generated a morphospace of the 3D shape of 70 non-saber and 25 saber-tooth species, a subset of which were used to quantify functional metrics of puncture performance and breakage resistance. These data were combined using a Pareto rank-ratio algorithm to evaluate optimality. We demonstrate that extreme saber-tooth morphologies are functionally optimal, occupying a localized peak in our optimality landscape. Unlike other optimal canine morphologies, extreme saber teeth optimize puncture performance at the expense of breakage resistance. This identifies functional optimality as a key driver underpinning the repeated evolution of this iconic tooth.

Activity in the early visual cortex is thought to tightly couple with conscious experience, including feedback-driven mental imagery. However, in aphantasia (a complete lack of visual imagery), the state of mental imagery, what takes its place, or how any activity relates to qualia remains unknown. This study analyzed univariate (amplitude) and multivariate (decoding) blood-oxygen-level-dependent (BOLD) signals in primary visual cortex during imagery attempts. "Imagery" content could be decoded equally well in both groups; however, unlike in those with imagery, neural signatures in those with validated aphantasia were ipsilateral and could not be cross-decoded with perceptual representations. Further, the perception-induced BOLD response was lower in those with aphantasia compared with controls. Together, these data suggest that an imagery-related representation, but with less or transformed sensory information, exists in the primary visual cortex of those with aphantasia. Our data challenge the classic view that activity in primary visual cortex should result in sensory qualia.