Biology Letters最新文献

Temperate fishes often spawn in response to environmental cues, such as temperature, thereby facilitating larval emergence concurrent with suitable biotic and abiotic conditions, such as plankton blooms. Climatic changes may alter the reproductive phenology of spring- and autumn-spawning freshwater fish populations. Such effects may depend on the sensitivity of reproductive phenology to ambient temperatures. We applied a meta-analysis approach to test whether annual temperature and year affected fish reproductive phenology. Based on preliminary tests in walleye (Sander vitreus) and Lake Constance whitefish (Coregonus arenicolus), we hypothesized that increasing temperature would promote earlier spring-spawning and later autumn-spawning. We found spawning was significantly earlier in the spring and later in the autumn. We found that migration of autumn-spawning species occurred earlier with warmer temperatures, implying that with increasing temperatures, migrating autumn-spawning species will increase residence time in tributaries. We also found that spring-spawning fishes reproduced earlier in more recent years, while we observed no significant effect in autumn-spawners. Spring- and autumn-spawning fishes displayed interannual variation in spawning dates (mean range of 34.4 and 27.0 days over 33.9 years, respectively), with spring-spawning fishes displaying a significantly broader range in spawning dates.

Since the start of the twenty-first century, there has been a notable increase in annual publications focusing on dinosaur reproduction and ontogeny with researchers using these data to address a range of macroevolutionary questions about dinosaurs. Ontogeny, which is closely tied to osteological morphological variation, impacts several key research areas, such as taxonomic diversity, population dynamics, palaeoecology, macroevolution, as well as the physiological and reproductive factors driving ecological success. While these broad studies have significantly advanced our understanding of dinosaur evolution, they have also revealed important challenges and areas needing further investigation. In this review, we aim to outline some of these challenges in major research areas linked to dinosaur ontogeny, namely reproductive biology, osteohistological growth strategies, morphological osteological variation and the link between ontogeny and macroevolution. We also offer some recommendations for best practices and promising future research directions. These recommendations include increasing sample sizes through fieldwork and exhaustive use of pre-existing fossil collections, using micro-computed tomography (μCT) scanning methods to increase dataset sizes in a non-destructive manner, methodical collection and reposition of μCT scan data, assessing ontogenetic maturity, establishing consistency in terminology and methods and building comprehensive extant comparative datasets.

The concept of animal welfare is evolving due to progress in our scientific understanding of animal biology and changing societal expectations. Animal welfare science has been primarily concerned with minimizing suffering, but there is growing interest in also promoting positive experiences, grouped under the term positive animal welfare (PAW). However, there are discrepancies in the use of the term PAW. An interdisciplinary group arrived at a consensus that 'PAW can be defined as the animal flourishing through the experience of predominantly positive mental states and the development of competence and resilience. PAW goes beyond ensuring good physical health and the prevention and alleviation of suffering. It encompasses animals experiencing positive mental states resulting from rewarding experiences, including having choices and opportunities to actively pursue goals and achieve desired outcomes'. The definition also considers individual and species-specific differences. It provides a framework for researchers to investigate PAW and thereby generate innovative, informative and reproducible science. Studies of PAW can contribute to a richer picture of an animal's life and may elucidate the biological foundations of happiness. The definition creates opportunities to inspire scientific progress in animal biology and to align animal care practices, legislation and markets with societal expectations.

This paper is focused on the origins of the contemporary genetic code. A novel explanation is proposed for how the mapping of nucleotides in DNA to amino acids in proteins arose that derives from repeat nucleotide sequences able to form alternative nucleic acid structures (ANS), such as the unusual left-handed Z-DNA, triplex, G-quadruplex and I-motif conformations. The scheme identifies sequence-specific contacts that map ANS repeats to dipeptide polymers (DPS). The stereochemistry required naturally evolves into a non-overlapping, triplet code for mapping nucleotides to amino acids. The ANS/DPS complexes form a simple, genetically transmitted, self-templating, autonomously replicating collection of 'tinkers' for Nature to evolve. Tinkers have agency and promote their own synthesis by forming catalytic scaffolds with metals, further enhancing their capabilities. Initial support for the model is provided by computational models built with AlphaFold3. The predictions made are properly falsifiable with the currently available methodology.

The success of introduced species often relies on flexible traits, including immune system traits. While theories predict non-natives will have weak defences due to decreased parasite pressure, effective parasite surveillance remains crucial, as infection risk is rarely zero and the evolutionary novelty of infection is elevated in non-native areas. This study examines the relationship between parasite surveillance and cytokine responsiveness in native and non-native house sparrows, hypothesizing that non-natives maintain high pathogen surveillance while avoiding costly inflammation. We made this specific prediction, as this pattern could enable invaders to effectively mitigate pathogen risk in a manner commensurate with the life-history priorities of a colonizing organism (i.e. rapid maturation and high reproductive effort). To test this hypothesis, we measured TLR-2 and TLR-4 expression, markers of pathogen surveillance and cytokine responses (changes in IL-1β and IL-10), regulators of inflammation, to a simulated bacterial infection. In non-native sparrows, we found that as TLR-4 expression increased, IL-1β and IL-10 responses decreased, a relationship not observed in native sparrows. Additionally, higher body condition predicted larger IL-1β and IL-10 responses in all birds. These findings suggest that high TLR-4 surveillance may mitigate strong inflammatory responses in non-native sparrows, with pathological and resource-based costs driving immune variation among and within populations.

Dinosaur locomotor biomechanics are of major interest. Locomotion of an animal affects many, if not most, aspects of life reconstruction, including behaviour, performance, ecology and appearance. Yet locomotion is one aspect of non-avian dinosaurs that we cannot directly observe. To shed light on how dinosaurs moved, we must draw from multiple sources of evidence. Extant taxa provide the basic principles of locomotion, bracket soft-tissue reconstructions and provide validation data for methods and hypotheses applied to dinosaurs. The skeletal evidence itself can be used directly to reconstruct posture, range of motion and mass (segment and whole-body). Building on skeletal reconstructions, musculoskeletal models inform muscle function and form the basis of simulations to test hypotheses of locomotor performance. Finally, fossilized footprints are our only direct record of motion and can provide important snapshots of extinct animals, shedding light on speed, gait and posture. Building confident reconstructions of dinosaur locomotion requires evidence from all four sources of information. This review explores recent work in these areas, with a methodological focus.

Pollinators face declines and diversity loss associated with multiple stressors, particularly pesticides. Most pollination services are provided by annual bees that undergo winter diapause, and many common pesticides are highly soluble in water and move through soil and plants where bees hibernate and feed, yet the effects of pesticides on pollinators' diapause survival and performance are poorly understood. Pesticides may have complex effects in bees, and some were shown to induce hormetic effects on various traits characterized by high-dose inhibition coupled with low-dose stimulation. Here, we examined the occurrence of hormesis in the responses of bees to imidacloprid. We found that while longevity and reproduction were reduced following exposure to imidacloprid, the survival length of new queens (gynes) was greater. Diapause is a critical period in the life cycle of most bees with profound effects on their health. Exposure to sublethal doses of pesticides may increase bees' resistance to stress/cold during diapause but may also trade off with reduced reproductive performance later in life. Identifying these trade-offs is crucial to understanding how stressors affect pollinator health and should be accounted for when assessing pesticide risk, designing studies and facilitating conservation and management tools for supporting annual bees during diapause.

Reproductive senescence is common across taxa and females often show a predictable decline in fecundity after maturity. Attending to these age-dependent cues could help males make optimal mate choice decisions. Here, we examined reproductive senescence and male mate choice in the androdioecious mangrove rivulus (Kryptolebias marmoratus), where self-fertilizing hermaphrodites exist with rare males. Hermaphrodites showed a strong decline in fecundity as they aged and genetic lineages varied in their fecundity at both young and old ages. Surprisingly, when given a simultaneous choice between genetically identical old and young hermaphrodites, males did not simply prefer younger hermaphrodites. Instead, male preference for younger versus older partners depended on the genetic lineage of the partners, resulting in a strong genotype × age interaction. For some genetic lineages, hermaphrodites were more attractive to males when younger, but for other genetic lineages, hermaphrodites were more attractive when older. Our results suggest that the genetic identity of the partner is key to how males weigh age-dependent changes in fecundity and that males are able to assess genetic variation in attractiveness over a partner's reproductive lifespan. Exploring how gamete viability and outcrossing are affected by age across genetic lineages could help us further understand these male preferences.

Compared with their free-ranging counterparts, wild animals in captivity experience different conditions with lasting physiological and behavioural effects. Although shifts in gene expression are expected to occur upstream of these phenotypes, we found no previous gene expression comparisons of captive versus free-ranging mammals. We assessed gene expression profiles of three brain regions (cortex, olfactory bulb and hippocampus) of wild shrews (Sorex araneus) compared with shrews kept in captivity for two months and undertook sample dropout to examine robustness given limited sample sizes. Consistent with captivity effects, we found hundreds of differentially expressed genes in all three brain regions, 104 overlapping across all three, that enriched pathways associated with neurodegenerative disease, oxidative phosphorylation and genes encoding ribosomal proteins. In the shrew, transcriptomic changes detected under captivity resemble responses in several human pathologies, including major depressive disorder and neurodegeneration. While interpretations of individual genes are tempered by small sample sizes, we propose captivity influences brain gene expression and function and can confound analyses of natural processes in wild individuals under captive conditions.

The acute-phase response (APR) is an adaptive emergency life-history stage, wherein vertebrates exhibit fever and anorexia to survive an infection. However, induced immune responses are energetically costly, and sick animals may reduce physical activity to compensate. Tests of this predicted energetic trade-off in free-ranging animals are rare due to difficulties in measuring individual physiology and behaviour under immune challenge in natural settings. However, recent advances in biologging technology now make such studies possible. We surgically implanted heart rate/temperature loggers in free-ranging adult male Arctic ground squirrels, fitted the squirrels with collar-mounted accelerometers and light/temperature loggers, and injected animals with lipopolysaccharide (LPS) to simulate an immune challenge. LPS-injected squirrels exhibited approximately 1°C overnight fevers accompanied by slightly elevated (10 bpm) heart rates; LPS-injected squirrels also spent 19% less of their time aboveground the following day and reduced overall movement by 40% compared with saline-injected controls. Thus, we found support for an energetic trade-off between functional immune responses (fever and anorexia) and lethargic sickness behaviour within the APR of a free-ranging mammal. Moreover, our results suggest animal-borne devices can play an important role in future studies of vertebrate immunity and disease dynamics.