Biology subjects

Ruuskanen, S.

Publications and source records attributed to Ruuskanen, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Action-related brain dynamics during leader-follower coordination

Leader-follower dynamics are essential for social interaction, enabling smooth inter-personal coordination. Although neuroimaging studies have identified brain networks associated with leading and following, the dynamical brain signatures supporting these roles remain poorly characterized. Here, sixteen dyads performed a joint-improvisation mirror-game task with predefined leader-follower roles while magnetoencephalography (MEG) and hand kinematics (acceleration) were simultaneously recorded. We investigated role-specific modulations of source-space MEG activity in delta (0.54 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (13-30 Hz), and gamma (40-90 Hz) frequency bands, as well as coherence between cortical activity and movement kinematics. Compared with leaders, followers exhibited stronger theta-band activity in a cluster comprising frontal, cingulate, and sensorimotor regions, and stronger coherence between movement kinematics and occipital cortical activity, consistent with enhanced monitoring, adaptation, and reliance on visual kinematic information. In contrast, leaders showed reduced alpha-band power in sensorimotor and premotor regions, and stronger beta-band activity in occipital cortices, likely reflecting greater demands for action planning and predictive control. Our results identify complementary spectral and action-related brain signatures associated with leader-follower coordination during joint improvisation, providing new insights into the neural underpinnings of real-time interpersonal coordination.

neuroscience↗

bioRxiv2026

The effect of the consumption of toxic prey on avian predator physiology

Many insects sequester plant toxic metabolites as a chemical defence against predators. Predators are predicted to include chemically defended prey in their diet if the benefits of gaining nutrients outweigh the costs of ingesting toxins. However, the physiological costs associated with the consumption of prey toxins remain largely unknown, especially when using ecologically relevant predators and naturally occurring levels of toxins. Here, we investigated whether the consumption of chemically-defended wood tiger moths (Arctia plantaginis) influences the physiological state of an avian predator, the great tit (Parus major). We manipulated the moth toxicity by first rearing the larvae in two different diets that varied in pyrrolizidine alkaloid (PA) content, and then manually extracting part of the defensive secretions from half of the moths in both diet groups. This led to four treatments with different moth PA profiles, which were fed to great tits for six consecutive days. After the bird diet manipulation, we collected fecal and blood samples for various physiological analyses of stress and metabolism. We found no significant effects of PA consumption on corticosterone or serotonin concentrations, nor on oxidative stress biomarkers. However, birds exposed to higher PA doses used more of their mitochondrial maximal capacity, which might result from increased metabolic stress. Overall, our results suggest that incorporating some PA-defended insects in the diet does not incur high physiological costs to avian predators, but further studies are needed to explore the costs of consuming a higher number of defended prey and the interactive effects of different prey toxins.

ecology↗

bioRxiv2026

Interpretable Decoding of Frequency-Resolved Functional Connectivity

Whole-brain functional connectivity, estimated from magnetoencephalography (MEG) data, provides a compact representation of long-range neuronal communication, making it suitable for predictive biomarker discovery. In this work, we propose a deep learning framework (FC-CNN) for predicting brain states from frequency-resolved functional connectivity estimates derived from resting-state MEG recordings. We systematically compare the performance of FC-CNN to that of conventional regression methods using amplitude and phase-based functional connectivity in the well-studied age-prediction task on the Cam-CAN cohort (n=576). We show that FC-CNN outperforms conventional approaches, and that, compared to phase synchronization, amplitude envelope correlation consistently leads to higher prediction performance. Moreover, we present quantitative evidence that the weights of a trained deep learning model can enable neurophysiological interpretation of the activity patterns that inform successful predictions. Our work demonstrates that the proposed approach successfully decodes brain states from MEG functional connectivity and is promising for discovery of predictive biomarkers for brain disorders.

neuroscience↗

bioRxiv2026

The effect of parental provisioning on the development of prey preferences in great tit (Parus major)

To make adaptive foraging decisions, naive individuals need to gather information about the local prey community. Besides sampling prey personally, the young could gather information about prey profitability by observing the foraging behaviour of other individuals, and parental provisioning provides the first opportunity to acquire this social information. Still, previous research on vertical transmission of prey preferences from parents has provided mixed results that are often confounded with other information sources, such as siblings and peers. It is also not known whether information from parents can change potential innate biases against certain prey types, such as avoidance of warningly coloured insects. Here, we tested whether social information acquired by offspring during parental provisioning influences the development of prey preferences in a generalist predator, the Great Tit (Parus major). We brought 15 great tit broods and their parents into captivity at late nestling stage (14 days old) and divided them into three social information treatments where parents were provided with either brown, red or yellow palatable maggots to feed to their dependent young for 8 days. Once foraging independently from parents, we conducted a preference test where juveniles were offered the full array of coloured maggots. Regardless of palatable exposure to typical warning-coloured maggots (i.e. red and yellow), juveniles consistently preferred yellow over red, and preferred brown maggots the most (i.e. lacking warning coloration). This supports the existence of innate biases against typical warning colours, and that social information from parents is unlikely to override these, at least when alternative prey is easily available.

animal behavior and cognition↗

bioRxiv2025

Early-life adversity modulates growth trajectories and red blood cell mitochondrial metabolism in king penguin chicks

In many avian species, variation in breeding phenology is known to affect reproductive success. In king penguins, the breeding cycle lasts more than a year, and the start of egg-laying extends over 3 months, with early-breeders laying eggs around December and late-breeders around February. Consequently, late-born chicks have less time to grow and build up their energy reserves before the Austral winter. It is however not known whether late-born chicks display alternative physiological strategies to catch up before winter. Variation in metabolic rate is one important pathway driving differences in growth patterns, as it is directly involved both in energy allocation processes and fitness. The conversion of resources into energy occurs in mitochondria, and the efficiency of this conversion is likely to play a fundamental role in explaining individual heterogeneity in growth and survival. The purposes of this study were to investigate the differences in red blood cell mitochondrial metabolism between early- and late-born king penguin chicks and to assess whether morphometric phenotypes could be explained by differences in mitochondrial metabolism. Late-chicks expressed higher mitochondrial metabolism compared to early-chicks at 100 days post-hatching, probably linked to the stress related to winter environmental conditions and a decrease in parental feeding rates. We did not find a clear association between chick mitochondrial metabolism and growth patterns, suggesting that mostly environmental conditions contributed in explaining different metabolic phenotypes. As king penguin populations in Crozet may face changing breeding conditions (changes in feeding area and foraging trips duration) in relation to global changes, studying the physiological traits and adaptations underlying the chick growth and survival may help understanding the response of king penguins facing challenging conditions.

physiology↗

bioRxiv2025

Warm and cool temperatures decrease early-life telomere length in wild pied flycatchers

Climate change represents a major challenge for avian species. It is characterized by an increase in average ambient temperatures, but also in occurrence of extreme weather events, such as heat weaves and cold snaps. These abrupt temperature changes can modify the immediate and long-term survival prospects of nestling birds, when their thermoregulatory capacities are still not fully developed. While immediate nestling survival can easily be measured, long-term survival is more challenging to evaluate. Early-life telomere length has been suggested as a potential biomarker of future fitness prospects. To evaluate the potential impact of changes in early-life temperature, we thus experimentally increased (ca. +2.8{degrees}C) and decreased (ca. -1.7{degrees}C) average nestbox temperatures in wild pied flycatchers (Ficedula hypoleuca) during nestling postnatal growth, and measured nestling telomere length before fledging. Shorter telomeres were observed in individuals exposed both to an experimental heating or cooling during growth. Our results suggest that long-term survival prospects or long-term performances of individuals exposed to abrupt changes in early-life temperature may be decreased. O_FIG O_LINKSMALLFIG WIDTH=197 HEIGHT=200 SRC="FIGDIR/small/651824v2_ufig1.gif" ALT="Figure 1"> View larger version (118K): org.highwire.dtl.DTLVardef@2ec526org.highwire.dtl.DTLVardef@915e9borg.highwire.dtl.DTLVardef@1da157borg.highwire.dtl.DTLVardef@b857ce_HPS_FORMAT_FIGEXP M_FIG C_FIG

zoology↗

bioRxiv2025

Cortical functional connectivity across the adult lifespan and its relation to sensorimotor integration

The operation of the human brain relies on functional networks enabled by inter-areal oscillatory synchronization between neuronal populations. Although disruptions in this functional connectivity are associated with brain disorders, evidence on its healthy age-dependent variation and behavioral relevance remains limited. Utilizing magnetoencephalography (MEG) recordings from 576 adults aged 18-87 years, we investigated the evolution of resting-state functional connectivity (rs-FC) across the healthy adult lifespan. We observed age-related, frequency-specific changes in widespread cortical networks. Alpha-band (8-13 Hz) rs-FC decreased, while delta (1-4 Hz), theta (4-8 Hz), and gamma-band (40-90 Hz) rs-FC increased with age. Beta-band (13-30 Hz) rs-FC followed a non-linear trajectory, peaking in middle age. The global delta, theta, alpha, and beta-band patterns differed from concurrent changes in oscillatory power, underscoring their dissociable contributions. Notably, reduced beta-band rs-FC was associated with increased sensorimotor attenuation, indicating that changes in rs-FC are behaviorally relevant for sensorimotor function. These findings advance our understanding of healthy brain aging and highlight a link between resting-state brain activity and sensorimotor integration. Key pointsO_LIFunctional connectivity is altered across the healthy adult lifespan in a frequency-dependent manner C_LIO_LIChanges in source power do not explain global functional connectivity trajectories C_LIO_LIBeta-band connectivity at rest is associated with sensorimotor attenuation independent of age-related effects C_LI

neuroscience↗

bioRxiv2024

The effects of early-life ambient temperature on the gut microbiome of a wild bird? an experimental approach

Vertebrate gut microbiome has significant effects on host development, health, and fitness. Multiple external factors contribute to gut microbiome variation, and the role of ambient temperature has gained increasing attention. Yet, temperature effects are often tested in extremes and in captive systems. We experimentally studied the effect of subtle temperature decreases during post-natal development on gut microbiome diversity and composition in wild pied flycatchers (Ficedula hypoleuca). We also performed partial cross-fostering to study the relative contribution of genetic and rearing environment on microbiome. Nest-box cold treatment did not influence gut microbiome diversity or composition, which may be due to the small temperature change, ontogenetic stage, or other factors, such as diet, causing large variation in the data. Rearing environment explained more of the variation in gut microbiome than genetic background, but the variance explained was relatively small. Future studies need to further address the drivers of the large intraspecific variation in microbiome in natural populations.

ecology↗

bioRxiv2024

Gut microbiome diversity associates with estimated lifetime and annual reproductive success in male but not female collared flycatchers

The gut microbiome (hereafter, GM) varies across individuals of the same species and this pattern has been observed in multiple wild species. Evidence shows that the GM connects to individual health and survival especially in captive species, but more research is needed to understand how the GM connects to host fitness in wild species. We used long-term monitoring data to investigate whether the GM of collared flycatchers Ficedula albicollis associates with annual and lifetime reproductive success (LRS), and survival to the following breeding season. This is the first study that 1) characterized the collared flycatcher GM, and 2) investigated how variation in the GM related to LRS in wild birds. Our results showed that higher GM diversity was associated with a higher annual and lifetime reproductive success in especially male collared flycatchers. We also found that the compositional variation in collared flycatcher GMs was explained by sex, age, and breeding habitat, but not by annual or lifetime reproductive success. Individuals that died before the next breeding season had higher abundances of ASVs belonging to the pathogenic families Enterobacteriaceae and Parachlamydiaceae, and the genera Corynebacteria and Sphingomonas. Our results show that the GM associates with different aspects of host fitness in a wild bird population. More research is needed to evaluate if there is a causal relationship between the GM and individual fitness. These findings also contribute to our understanding of the GMs role in evolution by elucidating the connection between the GM (trait) and reproductive success.

ecology↗

bioRxiv2024

DNA methylation associates with sex-specific effects of experimentally increased yolk testosterone in wild nestlings

Maternal hormones can profoundly impact offspring physiology and behaviour in sex-dependent ways. Yet little is known on the molecular mechanisms linking these maternal effects to offspring phenotypes. DNA methylation, an epigenetic mechanism, is suggested to facilitate maternal androgens effects. To assess whether phenotypic changes induced by maternal androgens associate with DNA methylation changes, we experimentally manipulated yolk testosterone levels in wild great tit eggs (Parus major) and quantified phenotypic and DNA methylation changes in the hatched offspring. Increased yolk testosterone levels decreased the begging probability, emphasised sex-differences in fledging mass and affected methylation at 763 CpG sites, but always in a sex-specific way. These sites associated with genes involved in growth, oxidative stress and reproduction, suggesting sex-specific trade-offs to balance the costs and benefits of exposure to high yolk testosterone levels. Future studies should assess if these effects extend beyond the nestling stage and impact fitness.

molecular biology↗

bioRxiv2023

Seasonal and environmental factors contribute to the variation in the gut microbiome: a large-scale study of a small bird

Environmental variation can shape the gut microbiome, but majority of studies use captive-bred species, while data on large-scale variation in the gut microbiome and the associated environmental factors is lacking. Furthermore, previous studies have limited taxonomical coverage, and for example knowledge about avian gut microbiomes is still scarce. We investigated large-scale environmental variation in the gut microbiome of wild adult great tits across the species European distribution range. Our results show that gut microbiome diversity is higher during winter and that there are compositional differences between winter and summer gut microbiomes. During winter, individuals inhabiting mixed forest habitat show higher gut microbiome diversity, whereas there was no similar association during summer. Also, temperature was found to be a small contributor to compositional differences in the gut microbiome. We did not find significant differences in the gut microbiome among populations, nor any association between latitude, rainfall, and the gut microbiome. The results suggest that there is a seasonal change in wild avian gut microbiomes, but that there are still many unknown factors that shape the gut microbiome of wild bird populations.

ecology↗

bioRxiv2023

Permeabilization status affects the relationship between basal metabolic rate and mitochondrial respiration in great tit blood cells

Although mitochondrial respiration is believed to explain a substantial part of the variation in whole-animal basal (BMR) or resting metabolic rate (RMR), few studies have addressed the relationship between organismal and cellular metabolism and how this may vary in environments where individual demands for energy differ. We investigated the relationship between whole-individual metabolic rate, measured in temperatures ranging thermoneutrality to far below thermoneutrality, and mitochondrial respiration of intact or permeabilized blood cells in two separate studies on wild great tits (Parus major L.). Our results show that, in permeabilized cells, there are significant positive relationships between BMR or RMR and several mitochondrial traits, including phosphorylating respiration rate through both complexes I and II (i.e., OXPHOS respiration). However, surprisingly, the LEAK respiration (i.e., basal respiration that mainly counteract for proton leakage) was not related to BMR or RMR. When measurements were performed using intact blood cells, BMR was positively related to ROUTINE respiration (i.e., mitochondrial respiration on endogenous substrates) in one of the two studies, but no other mitochondrial traits could explain variation in BMR or RMR in any thermal environment. These studies seem to show that the level of activation of mitochondrial metabolism as well as the permeabilization status of blood cells play a primary role on the extent to which blood metabolism might explain variations in the whole-individual metabolic rate.

physiology↗

bioRxiv2023

Early-life environmental effects on mitochondrial aerobic metabolism: an experimental brood size manipulation in wild great tits

Parental care (including postnatal provisioning) is a major component of the offsprings early-life environment. In avian species, the number of chicks in the nest and subsequent sibling competition for food are known to affect chicks growth, leading in some cases to long-lasting effects for the offspring. Because of its central role in converting energy, variation in the offsprings mitochondrial metabolism could be an important pathway underlying variation in growth patterns. Here, we performed a brood size manipulation in great tits (Parus major) to unravel its impact on offsprings mitochondrial metabolism and reactive oxygen species (ROS) production in red blood cells. We investigated the effects of brood size on chicks growth and survival, and tested for long-lasting effects on juvenile mitochondrial metabolism and phenotype. As expected, chicks raised in reduced broods had a higher body mass compared to enlarged and control groups. However, mitochondrial metabolism and ROS production were not significantly affected by the treatment either at chick or juvenile stages. Chicks in very small broods were smaller in size and had higher mitochondrial metabolic rates. The nest of rearing has a significant effect on nestling mitochondrial metabolism, yet variation in mitochondrial metabolism at the early-life stages are not associated with survival chances. The contribution of the rearing environment in determining offspring mitochondrial metabolism emphasizes the plasticity of mitochondrial metabolism in changing environments. Further studies would be needed to closely investigate what are the major environmental cues affecting the offspring mitochondrial metabolism during the growth period.

physiology↗

bioRxiv2023

Can increased prenatal exposure to thyroid hormones alter physiology and behaviour in the long-term? Insights from an experimental study in Japanese quails.

Maternal thyroid hormones (triiodothyronine T3 and thyroxine T4) are important regulators of embryonic development and gene expression. While maternal thyroid disorders are known to cause developmental issues in humans, variation in maternal thyroid hormones in healthy mothers have also been found to correlate with infant and child phenotypes. This suggests a potential impact of maternal thyroid hormones on offspring phenotype in an eco-evolutionary context. In chickens, prenatal thyroid hormone treatment has been shown to influence embryonic gene expression and postnatal treatment to influence imprinting and learning. However, the potential long-term effects of maternal thyroid hormones on physiology and behaviour are unclear. This study aims to investigate the long-term effects of maternal thyroid hormones on behaviour, plasma thyroid hormone levels and brain gene expression using the Japanese quail (Coturnix japonica) as a model. Egg hormone levels were elevated by injecting unincubated eggs with either saline (control), T3, T4 or a mixture of T3 and T4. Social motivation, boldness and fearfulness to predators were tested shortly after hatching and as adults. Plasma thyroid hormone levels and pallial expression of thyroid hormone receptor A, type 2 deiodinase, and nuclear receptor coactivator 1 were measured in adulthood. We found no evidence that elevated thyroid hormone levels in eggs affected behaviour, plasma hormone levels, or gene expression. This is the first study examining the potential long-term effects of elevated maternal thyroid hormones within the natural range. Although we found no evidence of long-term effects, other traits may still be affected and remain to be studied.

physiology↗

bioRxiv2023

From maternal glucocorticoid and thyroid hormones to epigenetic regulation of gene expression: an experimental study in a wild bird species

Offspring phenotype at birth is determined by its genotype and the prenatal environment including exposure to maternal hormones. Variation in both maternal glucocorticoids and thyroid hormones can affect offspring phenotype. However, the underlying molecular mechanisms shaping the offspring phenotype, especially those contributing to long-lasting effects, remain unclear. Epigenetic changes (such as DNA methylation) have been postulated as mediators of long-lasting effects of early-life environment. In this study, we determined the effects of elevated prenatal glucocorticoid and thyroid hormones on handling stress response (breath rate), DNA methylation and gene expression of glucocorticoid receptor (GCR) and thyroid hormone receptor (THR) in great tit (Parus major). Eggs were injected before incubation onset with corticosterone (main avian glucocorticoid) and/or thyroid hormones (thyroxine and triiodothyronine) to simulate variation in maternal hormone deposition. Breath rate during handling and gene expression of GCR and THR were evaluated 14 days after hatching. Methylation status of GCR and THR genes were analyzed from the longitudinal blood samples taken 7 and 14 days after hatching, as well as in the following autumn. Elevated prenatal corticosterone level significantly increased the breath rate during handling, indicating enhanced stress response and/or metabolism. Prenatal corticosterone manipulation had CpG-site-specific effects on DNA methylation at the GCR putative promoter region, while it did not significantly affect GCR gene expression. GCR expression was negatively associated with earlier hatching date and chick size. THR methylation or expression did not exhibit any significant relationship with the hormonal treatments or the examined covariates, suggesting that TH signaling may be more robust due to its crucial role in development. This study supports the view that maternal corticosterone may influence offspring metabolism and stress response via epigenetic alterations, yet their possible adaptive role in optimizing offspring phenotype to the prevailing conditions, context-dependency, and the underlying molecular interplay needs further research.

evolutionary biology↗

bioRxiv2022

Population divergence in maternal investment and embryo energy use and allocation reveals adaptive responses to cool climates

The thermal sensitivity of early life stages can play a fundamental role in constraining species distribution. For egg-laying ectotherms, cool temperatures often extend development time and exacerbate developmental energy cost. Despite these costs, egg laying is still observed at high latitudes and altitudes. How embryos overcome the developmental constraints posed by cool climates is crucial knowledge for explaining the persistence of oviparous species in such environments and for understanding thermal adaptation more broadly. Here, we studied maternal investment, and embryo energy use and allocation in wall lizards spanning altitudinal regions, as potential mechanisms of local adaptation to development in cool climates. Specifically, we compared population-level differences in (1) investment from mothers (egg mass, embryo retention and thyroid yolk hormone concentration), (2) embryo energy expenditure during development, and (3) embryo energy allocation from yolk towards tissue. We found evidence that energy expenditure was greater under cool compared with warm incubation temperatures. Females from relatively cool regions did not compensate for this energetic cost of development by producing larger eggs or increasing thyroid hormone concentration in yolk. Instead, embryos from the high-altitude region used less energy to complete development, i.e., they developed faster without a concomitant increase in metabolic rate, compared with those from the low-altitude region. Embryos from high altitudes also allocated relatively more energy towards tissue production, hatching with lower residual yolk:tissue ratios than low-altitude region embryos. These results suggest that local adaptation to cool climate in wall lizards involves mechanisms that regulate embryonic utilisation of yolk reserves and its allocation towards tissue, rather than shifts in maternal investment of yolk content or composition.

evolutionary biology↗

bioRxiv2022

Associations between brood size, gut microbiome diversity and survival in great tit (Parus major) nestlings

BackgroundThe gut microbiome forms at an early stage, yet data on the environmental factors influencing the development of wild avian microbiomes is limited. As the gut microbiome is a vital part of organismal health, it is important to understand how it may connect to host performance. The early studies with wild gut microbiome have shown that the rearing environment may be of importance in gut microbiome formation, yet the results vary across taxa, and the effects of specific environmental factors have not been characterized. Here, wild great tit (Parus major) broods were manipulated to either reduce or enlarge the original brood soon after hatching. We investigated if brood size was associated with nestling bacterial gut microbiome, and whether gut microbiome diversity predicted survival. Fecal samples were collected at mid-nestling stage and sequenced with the 16S rRNA gene amplicon sequencing, and nestling growth and survival were measured. ResultsGut microbiome diversity showed high variation between individuals, but this variation was not significantly explained by brood size or body mass. Additionally, we did not find a significant effect of brood size on body mass or gut microbiome composition. We also demonstrated that early handling had no impact on nestling performance or gut microbiome. Furthermore, we found no significant association between gut microbiome diversity and short-term (survival to fledging) or mid-term (apparent juvenile) survival. ConclusionsWe found no clear association between early-life environment, offspring condition and gut microbiome. This suggests that brood size is not a significantly contributing factor to great tit nestling condition, and that other environmental and genetic factors may be more strongly linked to offspring condition and gut microbiome. Future studies should expand into other early-life environmental factors e.g., diet composition and quality, and parental influences.

ecology↗

bioRxiv2021

From climate warming to accelerated cellular ageing: an experimental study in wild birds

Climate change is increasing both the average ambient temperature and the frequency and severity of heat waves. While direct mortality induced by heat waves is increasingly reported, sub-lethal effects are also likely to impact wild populations. We hypothesized that accelerated ageing could be a cost of being exposed to higher ambient temperature, especially in early-life when thermoregulatory capacities are not fully developed. We tested this hypothesis in wild great tits (Parus major) by experimentally increasing nest box temperature by ca. 2{degrees}C during postnatal growth and measuring telomere length, a biomarker of cellular ageing predictive of survival prospects in many bird species. While increasing early-life temperature had no detectable effect on growth or survival to fledging, it accelerated telomere shortening, and although non-significantly, reduced medium-term survival from 34% to 19%. Heat-induced telomere shortening was not explained by oxidative stress, but more likely by an increase in energy demand (i.e. higher thyroid hormones levels, increased expression of glucocorticoid receptor, increased mitochondrial density) leading to a reduction in telomere maintenance mechanisms (i.e. non-significant decrease in the gene expression of telomerase and protective shelterin). Our results thus suggest that climate warming can affect rate of ageing in wild birds, with potential impact on population dynamics and persistence.

physiology↗