Biological Reviews最新文献

Metazoan multicellularity and eusociality — both outcomes of the fraternal major transitions — have numerous features in common such as uneven distribution of group-establishing potential. In addition to this framework, I argue herein that the group-forming principles of metazoan multicellularity and eusociality are analogous to hierarchical cancer in that the cancer stem cells generate other cancer cells deprived of tumorigenicity. As such, I introduce concepts of germinating reproducers and sterile workers widely applicable to those systems. In particular, exploitative replication is suggested as an efficient strategy for maintaining the cooperation of fraternal cooperative organisations accompanied by asymmetric replication/reproduction. From this point of view, the defectors that spontaneously appear in metazoan multicellular organisms, eusocial colonies, and cancer clusters are cancers, egg-laying workers, and hypertumours, respectively. In a way similar to the policing observed in eusociality and metazoan multicellularity, I propose the hypothesis that the lactate-producing Warburg effect of cancer cells could represent a policing mechanism against hypertumours. Specifically, the Warburg effect establishes an acidified microenvironment that can repress growth of defector hypertumours by restricting diffusion of cancer growth factors. Considering the altruistic nature of the Warburg effect and metabolic plasticity, the possibility of hypertumours performing oxidative phosphorylation is discussed. This structural analogy not only highlights the role of asymmetric replication/reproduction in highly cooperative systems, but also provides a novel perspective on the social interactions of cancer cells, potentially laying foundations for clinical strategies aimed at disrupting cancer cooperation.

The browning of freshwater ecosystems is increasingly evident in temperate and northern regions, with widespread ramifications for lake physics, chemistry, and biology. Contrasting results on how freshwater browning may impact fish have been reported, but there has been no comprehensive examination of how browning may cause cascading effects on individual- to population- to community-level traits of freshwater fishes. We addressed this knowledge gap by summarizing the existing literature and conducting a series of original analyses to: (i) explore the effects of a brown water gradient on populations of eight economically important species of fish across 871 lakes; and (ii) examine how a brown water gradient may influence community trait compositions across 303 lakes. From our literature synthesis, we found that fish growth is often negatively associated with browner waters, despite browning generally showing no effect on fish foraging. We also demonstrated that browner waters had greater abundances of northern pike (Esox lucius) and walleye (Sander vitreus), but lower numbers of lake trout (Salvelinus namaycush), yellow perch (Perca flavescens), largemouth bass (Micropterus salmoides), smallmouth bass (M. dolomieu), and lake whitefish (Coregonus clupeaformis). Moreover, we showed that fish communities were significantly more likely to contain species with larger eyes in browner lakes. Lastly, we examined relationships between various metrics of browning (i.e. dissolved organic carbon, Secchi transparency, water colour) and present a framework for how the effects of freshwater browning on fish may scale from individuals to populations to communities.

Globally, rivers receive a diverse range of chemicals, including metals, pesticides, persistent organic pollutants, petrochemicals, human and veterinary pharmaceuticals and personal care products. However, the extent to which these different chemical groups affect riverine invertebrate communities is not well defined. Here we set out to evaluate the available evidence for associations between British riverine invertebrate communities and different chemical groups (and individual members of these chemical groups). Our assessment comprised three elements, (i) an evaluation of whether environmental concentrations of these chemicals exceed the lowest effect concentrations (ECs) based on laboratory tests, (ii) an assessment of associations between chemical groups and changes in British riverine invertebrate communities using the existing published literature, and (iii) calculated potential risk of toxicity of the chemical groups to invertebrates based on measured exposures (Environmental Agency monitoring data) and laboratory-based measurements of the lethal concentration required to kill half of the tested population (LC₅₀). Our conclusions indicate that metal and pesticide pollutants (including the veterinary medicine fipronil) are of greatest concern for British riverine invertebrate communities. Petrochemicals were also of potential concern, however, risk calculations indicate this risk is lower than that for metals and pesticides. All other chemical groups assessed appeared to be of relatively low risk to British riverine invertebrates based on the available information. However, the concentrations of some pharmaceuticals and personal care products in British rivers exceeded the lowest ECs for some invertebrate species and require further investigation. Given the widespread concern regarding declines in freshwater invertebrates, studies on chemical impacts on invertebrate populations in British rivers are surprisingly limited and further targeted studies are warranted.

Intervertebral disc degeneration (IDD) can contribute to lower back and neck pain. In IDD, the most affected component of the intervertebral disc is the nucleus pulposus (NP). Derived from the notochord, where cells are organized into a tandem configuration, young NP cells cluster in three-dimensional (3D) networks embedded in a gelatinous matrix. Here, we review the current understanding of NP development, homeostasis, physiology, and degeneration with a focus on the roles of the cell adhesion molecule N-cadherin in these processes. Based on the literature, we hypothesize that N-cadherin contributes to the architectural transition from the notochord to the NP by mediating a switch in cellular organization from tandem to random orientational cell adhesions (OCAs). We further hypothesize that the 3D clustering of NP cells may facilitate N-cadherin to act as a mechanosensor to modulate NP gene expression under mechanical stresses. We hope these hypotheses promote future research on the etiology of human IDD and the development of measures to prevent and treat IDD. Some open questions on N-cadherin functions in the NP are also discussed.

Mass mortality events (MMEs) have been occurring since the dawn of time. However, in contrast to terrestrial events, most marine MMEs remain undetected, largely due to the inaccessibility of many marine environments. One of the most notorious and best-studied marine MMEs in modern times is that of the population collapse of the echinoid Diadema antillarum in the Caribbean Sea during the mid-1980s, which triggered a catastrophic phase shift in local benthic communities from which the region never fully recovered – illustrating the ecological significance of echinoids in maintaining marine habitat stability. In recent years echinoid MMEs have reached an unprecedented scale, affecting populations across multiple ocean basins, climatic regions, and taxonomic range. Most recently, pathogenic-driven mortalities spreading from the Caribbean to the Mediterranean and Red Sea and further expanding into the Indo-Pacific, pose a significant threat to ecological integrity across thousands of kilometres. The apparent intensification of global echinoid MMEs underscores the urgency of elucidating the mechanisms driving these events and their implications for marine conservation.

Here we present a comprehensive review of global echinoid MMEs, including scientific literature dating back to 1888. We identify and formulate the five main mechanisms driving echinoid MMEs: (i) pathogens (33%); (ii) catastrophic events (25%); (iii) harmful algal blooms (11%); (iv) extreme temperatures and tides (24%); and (v) human activities (7%). We then explore spatio-temporal trends and the underlying functional morphology traits that drive these events.

In social species, group functions often benefit from variation among individual group members. Many highly integrated social insect colonies rely on division of labour among colony members and emergent properties of their collective behaviour and physiology. Response threshold models are a prominent proximate explanation of division of labour, but how variation in response thresholds arise is largely unexplored. We propose the Weak Worker Hypothesis, a novel conceptual framework suggesting that response thresholds are determined by an individual's susceptibility to the stressor that underlies the task. Thus, specific tasks are preferentially performed, or at least initiated, by the individuals that are most susceptible to the corresponding stressor. Consequently, ‘weak’ workers that are susceptible to a particular stressor play a disproportionate role in the group's defence against this stressor. The response threshold manifests as an internal evaluation of a task-specific stimulus that is influenced by the severity of the physiological perturbation of the individual, which simultaneously determines the susceptibility of this individual to succumb to the external disturbance. As long as individual stress susceptibilities vary among different stressors, this model generates division of labour and thus group stability. The Weak Worker Hypothesis provides a functional explanation for individual-level responses to environmental deviations from optimal conditions. Such a deviation could be directly perceived as stimulus and simultaneously lead to physiological stress, or the physiological stress caused by the deviation could be the stimulus itself. In support of the Weak Worker Hypothesis, we present experimental evidence of a link between individual heat susceptibility and fanning behaviour in honey bees (Apis mellifera L.). We also discuss other possible cases and how to test our idea empirically in other contexts, keeping in mind the important distinction between cause and consequence. Finally, we conclude that the Weak Worker Hypothesis could provide a useful extension of response threshold models for understanding the division of labour in social groups, which might have repercussions for applied social insect science, selective breeding and eradication efforts.