Biological Reviews最新文献

In 2004, researchers found a population of mitotically active germ stem cells in adult mice capable of differentiating into oocyte-like cells, which, by contradicting the long-existing dogma on the non-existence of postnatal oogenesis, caused a shift in fertility research. Further studies conducted in mice, human and other species have continuously confirmed the existence of these female germline stem cells. Given that these cells represent an extremely small portion of the total ovarian cell population, their isolation has been exceptionally challenging, with some studies being unable to identify these cells. Moreover, studies that identified these stem cells have observed a variety of sizes, morphologies and expression profiles. Thus, there is a lack of consensus on the characteristics of female germline stem cells, including their terminology, as different researchers have called them 'female germline stem cells', 'oogonial stem cells', 'egg precursor cells', 'very small embryonic-like stem cells' or other terms. This review summarises the findings on these stem cells from the ovaries of a range of species, with the aim of proposing a standardised terminology based on their intrinsic characteristics. We hope that this terminology will be unanimously used in future fertility studies.

Ecotoxicologists are using metabolomics increasingly to gain insight into toxicological mechanisms and sublethal effects of chemical exposures. Metabolomics offers a sensitive multi-parameter approach that can detect biochemical responses not obvious using apical and behavioural endpoints. This includes the responses to very low-dose toxicant exposures, variations in the physico-chemical state of experimental media, and even the progression of circadian rhythms. Consequently, repeatability and comparability of metabolomics experiments relies on the control and reporting of these features. In this systematic quantitative literature review, we examine recent ecotoxicology research to determine the rate and quality of reporting of circadian timing and other variables that influence circadian rhythms and the associated metabolome. We found that most circadian variables are underreported and call for further research into the influence of their manipulation on the metabolome.

Skeletal muscle architectural design strongly affects force-generating capacity and excursion range, and its functional importance to animal and human movement is well founded. Traditionally, this 'structure-function relation' has been inferred from architecture measurements with muscles at rest (from anatomical dissections or medical imaging techniques such as ultrasonography or magnetic resonance imaging) and muscle function tested under quasi-steady force conditions (e.g. isometric). A contemporary view recognises that, during active, dynamic contractions, muscles undergo load- and velocity-dependent changes in architecture and three-dimensional shape while remaining near-constant volume. Consequently, whole-muscle length change and velocity can become decoupled from fascicle length change and velocity, such that the whole muscle cannot be treated as a simple linear velocity transmission system but instead as a geared system where the input fascicle length change and velocity differ from the output whole muscle length change and velocity. This phenomenon is described by the concept of 'muscle gearing' and can be quantified as the ratio of the velocities or displacement of the muscle to the fascicle. Gear ratios are not fixed; instead, gear shifts with force and velocity, allowing the whole-muscle output to better match the mechanical demands of the task. Variable gearing is thought to emerge from load-dependent changes in fascicle angle and three-dimensional muscle deformations under volume-preserving and tissue constraints. Variable gearing has important functional implications, as it influences fascicle operating length and shortening velocity for a given task and thereby shifts where fascicles operate along their intrinsic force-length and force-velocity relationships. Through these effects, along with changes in the projection of fascicle force onto the muscle line of action as pennation varies, variable gearing can broaden whole-muscle force and power output across movement conditions. Accordingly, muscle gearing should be considered an integral component of a comprehensive framework for understanding dynamic muscle function in both normal and pathological states. Here, we synthesise evidence from animal and human studies to characterise variation in gearing across muscles, species and contraction conditions, and the factors that may underlie it. We use a previously validated three-dimensional finite-element muscle model to interrogate mechanisms that are difficult to isolate experimentally and, for the first time, demonstrate an effect of muscle activation on gearing. We also consider how ageing, injury and exercise training may alter gearing. Overall, muscle gearing has important functional implications, and our modelling demonstrates that it is an emergent property of the physics of muscle contraction.

Omphalosauridae are an under-appreciated part of the biotic recovery from the end-Permian Mass Extinction. This clade, including the genera Omphalosaurus, Sclerocormus and Cartorhynchus, is an enigmatic radiation of secondarily marine reptiles related to ichthyosaurs (Ichthyopterygia). Found across the Northern Hemisphere, omphalosaurid fossils invariably originate from open marine rocks of Olenekian (Early Triassic, 250-247 Ma) to earliest Ladinian (Middle Triassic, 237 Ma) age. The most distinctive feature (and the most common kind of fossil) of Omphalosauridae is its peculiar maxillary and dentary tooth batteries, presumably adapted for grinding up shelled cephalopods (ammonoids). Here, we report the first three-dimensionally preserved omphalosaurid skull and associated neck. The fossil originates from the Olenekian Vikinghøgda Formation of the Arctic archipelago of Svalbard and is assigned to a new genus and species, Ammonitritor scientiacivium. Phylogenetic analysis recovers a well-supported Omphalosauridae as the sister group to a clade comprising the Chinese Chaohusaurus and Ichthyopterygia. The most basal member of the clade is Cartorhynchus, followed by Ammonitritor. The clade Nasorostra, previously proposed for the Chinese omphalosaurids Cartorhynchus and Sclerocormus, was not recovered. Olenekian omphalosaurids likely attained maximum body lengths exceeding 6 m, while Middle Triassic forms reached well over 10 m. Thus, some of the oldest marine reptiles from Panthalassa were already large-bodied at their first appearance, approximately 2 million years after the end-Permian extinction. Together with other Ichthyosauriformes, omphalosaurids represent the only marine reptile clade generally present in Panthalassa during the Early and Middle Triassic.

Agriculture must ensure food production without further compromising the ecosystem functions upon which it depends. Agricultural practices should therefore avoid harming farmland biodiversity, especially of taxa that supply the key ecosystem services (e.g. pollination, pest control and nutrient uptake) that ultimately support crop production. Orchards are among the largest permanent plantations worldwide and are increasingly characterised by the spread of plastic nets used to protect fruits/nuts from either abiotic (anti-hail, anti-rain, shade nets) or biotic (exclusion nets) hazards. Despite having received little attention to date, these nets may impact natural communities, acting both as physical barriers and as drivers of habitat changes to which biota must respond. Species-level responses to netting depend on the organism's ability to enter the netted environment and successfully exploit available resources. Net-mediated ecological filtering and plastic behavioural responses may alter species interactions, leading to cascading ecological impacts that may create species-poorer 'netted communities' with simplified ecological networks. Such changes may erode biological control potential, other ecosystem functions, and overall system stability. We conducted a systematic review on the effects of protection nets on biota, and reported novel empirical evidence on anti-hail nets' impacts on communities of orchard-dwelling birds, flower-visiting insects, and rodents. In total, we identified 48 studies from the literature, however this literature was strongly biased towards apple orchards, western countries, and pest taxa. Net deployment was highly effective in deterring target pest species, in some cases regardless of their original function, as even weather-protection nets limited pest populations. Side effects on non-target taxa were also often reported, such as decreases in pollinators and natural enemies, and/or increases in secondary pests or microbial diseases. However, most assessments largely disregarded non-pest taxa and the broader ecological consequences of netting. The few studies that addressed the effects of nets at the guild/community level, including our empirical study, confirmed that orchard netting resulted in species-poor assemblages, with possible ecosystem-level consequences. We propose that future assessments should pay more attention to the indirect effects of netting on non-target taxa, and on the supply of crop-supporting ecosystem services mediated by wild species occurring in agroecosystems. Due to the trade-offs between these services and net-mediated crop protection, integrated alternatives should be tested to improve the environmental sustainability of food production and biodiversity conservation in farmed landscapes.

As anthropogenic activities continue to expand globally, large-scale livestock encroachment into wildlife habitats increasingly threatens ecological balance, particularly by altering species interactions. Millions of wild ungulates now share plant resources with domestic grazers, facing dual pressures from interference competition and nutritional stress due to declining forage quality. Although extensive research has documented potential competition between sympatric wild and domestic ungulates, a comprehensive quantitative synthesis of the magnitude and drivers of these interactions remains lacking. In this study, we conducted a meta-analysis of 57 peer-reviewed studies (329 cases) to evaluate global patterns of dietary niche overlap between wild ungulates and livestock. Our results revealed that both wild ungulate traits and livestock type significantly influenced the effect sizes. Moreover, climate zones, annual precipitation, and interactions with anthropogenic pressures modulated livestock-wildlife dietary niche overlap. Polar regions and large-bodied species exhibited heightened sensitivity to human activities, while areas with higher annual precipitation showed reduced variation in dietary niche overlap intensity. These findings suggest that wildlife-livestock dietary niche overlap is shaped by multiple factors. While additional factors beyond dietary niche overlap should be considered in conservation assessments, our results suggest several potential management strategies including reducing anthropogenic disturbance in polar regions, integrating grazing management with efforts to reduce human disturbance in large ungulate habitats, and adjusting livestock composition and supplementary feeding in moisture-deficient and tropical regions. Future conservation assessments should integrate dietary overlap shifts with other conservation risks for a more comprehensive evaluation.

Nestling begging is a key model for understanding animal communication and parent-offspring conflict. Dynamic begging displays are often interpreted as costly, honest signals of need, with honesty maintained by viability costs, as proposed in Godfray's influential signalling model. However, this framework has faced increasing theoretical criticism and mixed empirical support. Here, we reassess three core predictions of the honest-signalling framework. First, experimental evidence strongly supports begging as a signal of short-term hunger, but evidence that it reliably reflects long-term need or intrinsic quality is limited. Begging is also highly plastic, varying with prior experience, nestmate and parental behaviour, body temperature, brood size and other contextual factors. This raises questions about the precision and information content of the display. Second, although parents often increase provisioning in response to collective begging, food allocation within broods is frequently influenced by non-begging cues such as size, position and colouration, and intense begging is not invariably rewarded. Sibling responses are also more diverse than predicted by purely competitive models, encompassing escalation, de-escalation, negotiation and potentially prosocial coordination. Third, empirical support for direct costs of begging, particularly predation and physiological costs, remains weak or inconsistent, whereas indirect inclusive-fitness trade-offs appear more plausible. Together, these findings challenge assumptions of fully informative signals, invariant parental responsiveness and necessary direct signalling costs. We argue that future work should move beyond traditional signalling and scramble-competition models by incorporating parental flexibility, receiver inattention, learning, signal and response plasticity, and family-level rather than dyadic parent-offspring interactions. We also outline conceptual and empirical avenues that may facilitate progress, highlighting a field that remains rich in unresolved questions and opportunities for future research.

Understanding migration ecology is essential for effective conservation of migratory species. To achieve a comprehensive understanding of the ecology of migrating species, it is necessary to study how species react to the complex interplay of intrinsic and extrinsic conditions when optimizing their migratory journey in terms of survival, energy and time. Nocturnal migratory songbirds, which often migrate alone and alternate migratory endurance flights with stopovers, provide an excellent group for studying such individual decisions. Specifically, the decision to interrupt the migratory flight and land and the decision to depart from a stopover are critical for the success of migration. We screened 1490 studies, of which 286 studies were eligible, using a systematic literature review, to identify five significant knowledge gaps in the migration ecology of songbirds: (i) exploring when and where bird mortality occurs during migration; (ii) inferring stopover functions from landing decisions; (iii) assessing the consequences of migration distance on migratory decisions; (iv) measuring how predation danger affects bird decisions; and (v) studying the consequences of habitat quality on the migratory decisions. To address these knowledge gaps, we propose novel frameworks that integrate methods applied at different spatial and temporal scales to study songbird decisions in flight and at stopovers. We also discuss testable hypotheses and future directions to stimulate research for enhancing the understanding of migration ecology and advancing the conservation of threatened migratory songbird species.