Biology Letters最新文献

A major threat to the declining European hedgehog (Erinaceus europaeus) is road traffic. Devising methods to reduce the number of collisions would increase hedgehog welfare in an urbanized world and serve to protect this flagship species, and this goal might be advanced by an understanding of their hearing. This study investigates the auditory capabilities and anatomy of the ear of the European hedgehog. Using auditory brainstem response testing on 20 live hedgehogs from Danish wildlife rescue centres, we measured hearing thresholds across 4-85 kHz and found a peak sensitivity around 40 kHz, revealing that European hedgehogs can hear sound frequencies of at least 4-85 kHz. Complementary postmortem micro-CT scans enabled a detailed three-dimensional reconstruction of the inner ear, revealing small middle ear bones with a cochlear spiral of approximately 1.7 turns. Results show that hedgehogs can perceive a broad ultrasonic range, which provides important cues for directional hearing and may additionally function in prey detection and communication. These findings provide critical insights into hedgehog sensory biology and inform the potential development of ultrasonic repellents to mitigate traffic collisions and habitat disturbances, contributing to conservation strategies for this declining species.

The Ediacaran Weng'an Biota of South China yields embryo-like microfossils preserved with sub-cellular fidelity, previously interpreted as the oldest evidence of animals. Megasphaera dominates the assemblage and preserves the earliest stages of binary reductive division. It is assumed to develop into Megaclonophycus, which is composed of hundreds to thousands of cells; however, this developmental link has not been tested. We used synchrotron and computed tomography to characterize hundreds of specimens of Megaclonophycus and determine cell division patterns. Specimen cell counts range from 14 to 10 201, with counts clustering around 2048 and 4096, consistent with binary reductive cell division. However, the specimens have asynchronous binary cell division with cell sizes within a specimen varying by two- to threefold. The volume of Megaclonophycus is variable during development, showing no evidence of gastrulation, characteristic of metazoan development. Megaclonophycus and Megasphaera exhibit a similar sequence of development, size and taphonomy indicating a developmental sequence of early to later stages of the same organism. These findings are incompatible with the crown group metazoan affinity suggested for this taxon, and so molecular clock estimates for the origin of animals must rely on fossil calibration from sources other than Megaclonophycus.

Recognizing whether other species pose a threat is critical to survival. Learning from others avoids the need for dangerous encounters, so it can be particularly valuable, especially for young, vulnerable animals. Here, we tested whether young birds can learn socially about potential dangers even while still in the nest. Using playbacks, we presented wild jackdaw nestlings with calls from an unfamiliar predatory species (Eurasian goshawk) and an unfamiliar non-predator (American golden plover) in association with either conspecific alarm calls, implying danger, or contact calls, a neutral stimulus. When predator calls were paired with jackdaw alarm calls, nestlings learned to increase their vigilance rates. By contrast, vigilance rates were unchanged after predator calls were paired with jackdaw contact calls. Responses to the non-predator were not affected by pairing with either alarm or contact calls. This indicates that jackdaw nestlings can socially learn about unfamiliar calls and raises the possibility that they may show a predisposition (or 'preparedness') towards learning fear-relevant stimuli. Understanding the interplay between preparedness and social learning in the development of anti-predator responses is increasingly important as anthropogenic influences are altering predator compositions.

The tempo of evolutionary change varies widely across the tree of life, with some lineages undergoing extensive morphological diversification while others remain remarkably static. Notostraca, or tadpole shrimps, exemplify the latter, displaying minimal morphological change for hundreds of millions of years. To investigate the molecular basis of this exceptional stasis, we generated high-quality genome assemblies for Triops granarius and Triops simplex. These genomes, combined with data from 18 additional branchiopod species representing Notostraca and Onychocaudata, were employed for phylogenetic reconstruction and time estimation and support the emergence of Notostraca and their general morphology in the Devonian (approx. 390 Ma). We identified genes with significantly reduced rates of protein evolution in Notostraca compared to their more morphologically diverse sister group, Onychocaudata. Functional annotation linked these genes to morphogenesis and development, but we also detected genes with accelerated protein evolution associated with similar developmental processes. Notably, genes undergoing a decelerated evolution in their protein-coding sequences lack signatures of evolutionary constraints in their non-coding regions. In addition, sequence evolution and gene family expansion/contraction dynamics appear decoupled from the rate of protein evolution, suggesting that genes can undergo reduced evolutionary change in one aspect, but not in others. Our findings reveal a complex interplay between genomic and phenotypic evolution and suggest that morphological stasis is maintained by multiple molecular processes rather than by a single, overarching mechanism.

Understanding stable coexistence of competing species despite the competitive exclusion principle has been a central topic in ecology. Previous studies revealed that rapid contemporary evolution can promote species coexistence, but the mechanisms behind coexistence are not fully understood. A recent study showed that predator evolution can promote fluctuation-dependent species coexistence. Here, I propose a new mechanism where prey rapid evolution due to high genetic variance can also promote fluctuation-dependent coexistence of competing predator species. Previous experimental and theoretical studies demonstrated that rapid evolution of a prey defence trait can cause predator-prey population cycles. Although those studies focused on a system with a single predator species, I show that the population fluctuations driven by prey rapid evolution can promote coexistence of two competing predator species via a gleaner-opportunist trade-off. By expanding the framework of modern coexistence theory, I further show how prey rapid evolution can increase the niche difference of competing predators and simultaneously affect the competitive ability difference via population cycles. Given the propensity for oscillatory dynamics and prey rapid evolution (due to large population sizes and genetic variance) in nature, I argue that this expansion of coexistence theory provides an important solution to the coexistence paradox.

Paternal lifestyle factors are increasingly recognized as determinants of offspring health, yet the effects of physical inactivity on reproduction remain unclear. Here, we demonstrated that paternal physical inactivity caused a bias in offspring sex ratio and reduced fertility across generations in rats. Male rats subjected to eight weeks of restricted activity produced offspring with a female-biased sex ratio (female : male = 39 : 16; p = 0.011; odds ratio = 2.84) compared with controls (24 : 28). Sperm motility was markedly reduced in inactive fathers (p < 0.001 versus control) but was fully restored by voluntary wheel running (p < 0.05 versus inactive), indicating reversibility of this functional impairment. Cross-mating of first-filial-generation (F1) rats of inactive paternal origin revealed that females derived from inactive fathers exhibited lower pregnancy rates and smaller litter size, whereas F1 males displayed normal fertility. Remarkably, intercrosses between F1 males and females of inactive paternal origin produced no viable offspring surviving to weaning age. Although the sample size was limited, this outcome suggests a heritable impairment in reproductive success. These findings identify paternal physical inactivity as an environmental factor influencing offspring sex ratio and reproductive success across generations; however, studies with larger mating cohorts are needed to confirm this transgenerational phenotype.

Brown macroalgae like Fucus serratus are key ecosystem engineers in intertidal environments and are increasingly threatened by anthropogenic pollution and global change. This study examined how the combined effects of conventional and biosourced microplastic (MP) pellets and thermal stress affect the night-time respiration of F. serratus. Respiration rates were assessed after algae were exposed to a combination of aerial temperature treatments (6 h at 25°C as control or 35°C as a heat stress) and five immersed MP treatments (6 h exposure to control seawater, polypropylene, polypropylene with a biological matrix, polylactic acid or biopolyester solutions; n = 5 per treatment) in darkness. Our results showed a significant increase in respiration following heat stress, independent of MP exposure, suggesting a sustained metabolic stress-repair response and may indicate a cost to carbon balance and long-term tolerance. However, no significant effect of MP or interaction between stressors was detected. These findings suggest short-term resilience of F. serratus to MP exposure under the tested conditions. In an era of global change, further research on the combined and long-term effects of multiple stressors, including MP, on key physiological processes across seasons and species is needed to clarify their ecological consequences for intertidal macroalgal communities.

Geroscience has the goal of extending lifespan through geroprotective interventions. These interventions are typically imparted on groups of individuals, with their efficacy judged by increases in the average age-at-death. A more equitable outcome, which looks beyond the average, is to attain a long life for all individuals, such that the average age-at-death is high while variability (e.g. standard deviation in age-at-death) is low. This goal of increasing the mean while reducing variation is sometimes referred to as 'squaring the survival curve'. A recent meta-analysis of vertebrate data found that dietary restriction (DR) and the DR-mimetic, rapamycin, generally increase the average age-at-death, while metformin (also considered a DR-mimetic) is less effective. We have re-analysed this recently published data to study the effects of lifespan-extending treatments on variation in the age-at-death. On average, all three treatments increase the variance in the age-at-death, but not the coefficient of variation (i.e. standard deviation relative to the mean). This suggests that lifespan-extending treatments do not reduce variance and 'square the survival curve'. Rather, any gains in mean age-at-death are matched by corresponding increases in variation. Interestingly, this result is consistent with the treatments proportionally reducing both the age-dependent and age-independent parameters in a Gompertz model of mortality.

Frugivorous animals routinely ingest fruit sugars and the associated products of microbial fermentation. Yeast-derived ethanol within fruit is a recently described chronic feature (approx. 14 g d-1) of the chimpanzee diet, but physiological evidence of exposure has not yet been demonstrated. We assayed urine collected from 19 wild chimpanzees for the presence of ethyl glucuronide (EtG), a direct metabolite of ethanol. Urine samples were obtained from study individuals feeding almost exclusively in the canopy of mast-fruiting Gambeya albida (=Chrysophyllum albidum), freshly fallen fruits of which averaged a pulp-ethanol content of 0.09% (±0.01 s.e.; range 0.01-0.40%) across multiple ripe crops. Of 20 individual urine samples (nine from females and 11 from males, aged 10-46 years), 17 tested positive for EtG at an analytical threshold of 300 ng ml-1; out of a subset of 11 of these positive samples, 10 samples further tested positive at a threshold of 500 ng ml-1. These values are high relative to calibrations of the test method for modern humans and are consistent with substantial rates of ethanol consumption via frugivory in the wild.