Belgium

Climate change is predicted to cause rapid increases in temperature which will drive losses in freshwater biodiversity. Organisms will have to adapt to warming water conditions. Predicting the outcomes of climate change adaptation is important for species conservation but is challenging as most natural populations have yet to experience these anticipated conditions. However, come contemporary natural populations can experience warming through geothermal activity and provide direct insights into adaptation to warmed environments. We leveraged Icelandic threespine stickleback (Gasterosteus aculeatus) from populations undergoing adaptive divergence along a geothermal-ambient habitat axis. We aim to uncover the genomic and developmental underpinnings of adaptation to natural geothermal habitats. This research will further our understanding of the evolutionary processes promoting adaptation to warming conditions.

SEB Conference 2025

Metabolic adaptation in Icelandic threespine stickleback

phenotypic variation

evolution

plasticity

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Insights into the general nature of motor skill could fundamentally change how we develop movement abilities, with implications for musculoskeletal well-being and injury. Here, we sought to identify indicators of general motor skill–those shared by experts across disciplines (e.g., squash, ballet, volleyball) during non-specialized movements (e.g., reaching for water). Identifying such general indicators of motor skill has remained elusive. Using ultrasound imaging with deep learning and optical flow analysis, we tracked elastic tissues (muscles and associated connective tissues) during a simple reaching task performed similarly by world-class athletes and regional-level athletes drawn from diverse disciplines, as well as untrained non-experts. We analyzed previously unexamined inefficiencies: transverse elastic tissue motions orthogonal to muscle fiber direction and physiological tremors, which are oscillations that do not contribute to the net work done by muscles. We discovered that world-class experts minimize both these inefficient motions compared to regional level athletes and non-experts. While regional-level athletes surprisingly showed similar inefficiencies to non-experts, they used elastic tissues more effectively, achieving equivalent movements with smaller actuation-related tissue motions. We establish elastic tissue motion as a key indicator of general motor skill, expanding our understanding of elastic mechanisms and their role in general aspects of motor skill.

Efficient elastic tissue motions indicate general motor skill

Animals care about multiple objectives, yet are stuck with one set of musculoskeletal parameters at a time. So, the question naturally arises, what values should they pick and what tradeoffs may they face? We cannot answer the first question as it is subjective, however we can attempt to answer the second. Here we focus on Achilles tendon stiffness – whose value in humans has been shown to maximize efficiency in walking and running. We ask how does changing Achilles tendon stiffness (1) affect efficiency, stability and economy of movement in a cyclic bouncy gait (e.g. hopping) and (2) how do they tradeoff. To answer that question, we built a mathematical model of human hopping which consists of a mass in gravity actuated by a muscle-tendon unit across a lever arm (representing the foot). The muscle is cyclically stimulated at 2.5Hz (preferred hopping frequency) to generate hopping and efficiency (ratio of mechanical work and metabolic cost), stability (average ratio of energy dissipated and energy injected by a change in ground height), and agility (maximum and minimum work possible by changing stimulation timing) were calculated. We find (1) Nominal achilles tendon stiffness (180000 N/m) had maximum efficiency, medium stability, and low agility ( positive work) and high agility (negative work). Additionally, increasing stiffness had no benefit except agility (positive work). However, decreasing stiffness trades off lower efficiency to gain higher agility (negative work) and higher stability – potentially explaining why older adults have lower tendon stiffness values despite the energetic burden.

Trading off stability, agility and efficiency of movement across a broad range of muscle tendon morphologies

Muscle inertia should affect the mechanical output of muscle, with its effects being greatest at larger sizes, and greater accelerations. Muscle inertia is known to affect the mechanical output of isolated muscle preparations; however, its influence during natural, whole-body movement remains unclear. In this study, forces were compared between a traditional one-dimensional massless muscle model , and a muscle model in which muscle mass was distributed along its length. Kinematic and electromyographic data were collected from twenty participants performing walking, running, hopping and sit-to-stand tasks, and muscle was geometrically scaled using factors of 0.1, 1 and 10. The results showed that muscles modelled at a scale factor of 10 exhibited significantly higher root-mean-squared errors (RMSE) in normalised time-varying forces, reaching up to 7.23% of maximum force for the vastus lateralis during running compared to a maximum RMSE of 0.31% for scales 0.1 and 1. Furthermore, tasks involving higher muscle accelerations, such as running and hopping, resulted in greater mass effects than lower-cadence activities. These mass effects were smaller than those we have previously predicted from 3D muscle models. These findings underscore the importance of accounting for muscle mass in larger muscles during rapid movements, and the need to account for complete 3D muscle deformations and dynamics when understanding muscle force and function.

Muscle Mass affects the scaling of Force Predictions from 1D Hill-Type Models During Human Movement

Rapid global warming poses a serious threat to aquatic ectotherms. Evolutionary adaptation is a key mechanism that may enable populations to maintain performance under rising temperatures, yet it is rarely experimentally examined in vertebrates. Previous research in our laboratory demonstrated that zebrafish (Danio rerio) can evolve higher acute thermal tolerance, but this process is slow. Here, we present a large artificial selection experiment on zebrafish assessing the potential for adaptation of thermal growth performance. We selected zebrafish for improved juvenile growth across six generations under chronic thermal stress (N>10,800). Using a genetically diverse ancestral population (offspring of wild-caught zebrafish), we established selected lines (2 replicates, 300 fish/replicate) at cold (20°C), control (28°C) and warm (34°C) temperatures, and selected the 33% fastest-growing individuals for breeding. The results reveal a sustained, positive response to selection in all lines. Notably, the log growth rate of the warm-adapted line gradually increased from 0.008 to 0.013 mm/day in the F0  to F4  generation (total increase of 65%), reaching growth rates close that of the control line prior to selection, which suggests high evolvability. Ongoing analysis of the F5  generation will provide further insights into the evolution of thermal performance, including overall rates of adaptation, heritability, and shifts in optima. These results contribute to our understanding of how vertebrates may adapt to climate change and underscore the role of selection in shaping thermal resilience in aquatic species.

Artificial selection and the adaptive potential of thermal performance in zebrafish

It is widely appreciated that early developmental stages are highly sensitive to environmental stressors, resulting both in immediate impacts (including death) and more pervasive, long-term effects through to adulthood. The extent to which such heightened plasticity reflects adaptive responses or unavoidable vulnerability due to the nature of developmental processes is highly debated and depends on several aspects, including the organism’s life history, type of stressor and patterns of environmental change. Here, I give an overview of our work on maternal responses to stressors in pregnancy (heat, nutrition and infection) from an evolutionary perspective, including developing theoretical models; comparative studies across taxa, and experiments on insect models of viviparity, the tsetse fly (Glossina species) and Pacific beetle mimic cockroach (Diploptera punctata). Our work highlights the insights to be gained from considering stressors across different stages of gestation, whether maternal responses are always in the best interest of current offspring, and the challenges in establishing vulnerability versus adaptation.

Pregnancy as a critical window for understanding vulnerability and adaptation to stress: from models to maggots

Mothers sometimes exhibit aggression towards their dependent offspring, a behaviour often linked to the weaning conflict, where such maternal behaviour could promote offspring independence. However, maternal aggression may also arise from genetic abnormalities or be induced by certain environmental factors. Yet, the biological mechanisms underlying maternal aggression and the interplay between genetic and environmental components remain poorly understood. Despite evidence suggesting that exposure to aggression may have stronger effects on genetically predisposed individuals.
To investigate possible biological mechanisms, we conducted an experiment in domestic canaries (Serinus canaria), a species in which mothers may exhibit maternal aggression (MA) towards their chicks. Full clutches were cross-fostered within and between MA mothers and no-MA mothers, creating four experimental groups to identify genetic and environmental influences. Juveniles were exposed to a series of behavioural tests, and we hypothesised that early MA exposure would increase impulsivity, reduce neophobia in a feeding context, and enhance aggression, potentially leading to higher dominance ranks. These effects should be amplified in individuals genetically predisposed to aggression.
We found that the relative importance of genes and environment varied across behavioural traits. Aggression-related traits and response inhibition were primarily driven by genetic factors, possibly reflecting a genetic component of MA. Dominance rank or food motivation were predominantly shaped by the early life environment influences, with poorer conditions in broods of MA mothers. In contrast to our expectations a gene-by-environment interactions was only found for neophobia, but it remains speculative how and why the results differ from the other behavioural traits.

Born to aggressive mothers - are certain chicks more susceptible to early life exposure to aggression

The defining innovation of the vertebrate stomach is acid-peptic digestion. The acidic stomach pH is produced by the gastric proton pump (H+ /K+ -ATPase) and proteolysis by the aspartic peptidase, pepsin. This provides advantages in protein digestibility and other key functions. Although highly conserved, secondary loss or regression has paradoxically occurred independently in multiple lineages primarily in the fishes. To better understand the role of gastric acidification and the consequences of loss, we developed the first non-mammalian knockout (KO) of the gastric proton pump by targeting the catalytic a-subunit (Atp4a) using CRISPR-Cas9 gene editing in the model teleost fish Astyanax mexicanus. We have set out to elucidate the impact of acid in digestion and nutrient assimilation, and on the molecular mechanisms involved in the gastric chloride and potassium movement. In the KO animals, gastric acidification was abolished with no adverse effects on specific growth rates and appetite although body protein, Ca, Mg and P were lower, and lipid was higher compared to wild-type. We also found a striking new role for the stomach in lipid uptake. RNAseq analysis was also performed and identified 2064 differentially expressed genes (DEGs) in stomach and 160 DEGs in anterior intestine of atp4a-/-  fish. The differentially regulated gastric and intestinal pathways in atp4a-/-  animals elucidate the impact of stomach acid in oxidative stress, and lipid and iron metabolism. Taken together, our results shed light on the role of the stomach in the processes of nutrient assimilation, opening the door to further analyses using this novel genetic line.

Will you miss me when I am gone? Gastric proton pump knock out and the importance of gastric acid in digestion, metabolism and growth in fish. 

As part of the Nature4Nature project “Inspired to Integrate: Filtering Nature's Diversity for Nature-friendly Implementations“, this study explores filter-feeding morphology in dabbling ducks for bioinspiration. Dabbling ducks, comprising approximately 70 species, exhibit diverse feeding morphologies and ecological adaptations. However, the relationship between their distinct filtering structures and dietary preferences remains poorly understood, particularly regarding the morphology of soft tissues and keratinized structures. These structures, including the lamellae on the upper and lower beak and the lingual papillae, are integral to filter-feeding on the water’s surface. This project aims to establish clear links between filtration behaviour, diet, and filtering apparatus morphology in dabbling ducks. Using CT-scans of 25 phylogenetically diverse duck specimens and macro photography of 13 dissected tongues, we conducted morphometric analyses to quantify filtering structure variations. Online databases such as Avonet were used to supplement ecological information, including dietary compositions and foraging behaviour. Comparative studies correlated the morphological variations with the ecological data, shedding light on how different filtering structures adapt to various dietary preferences and ecological niches. Our data suggest convergent evolution of tongue morphology for filter-feeding. This research will provide novel insights into dabbling duck filter-feeding mechanisms and the ecological drivers of their morphological diversity. This knowledge will provide new perspectives for the subsequent abstraction of the filter morphology and mechanism for the development of a bioinspired design performing a filter function.

The Art of Filter Feeding: Insights into the Feeding Morphology and Ecology of Dabbling Ducks 

Large-scale kinetic models of photosynthesis offer precise, time-resolved predictions of photosynthesis, gas exchange, and metabolic processes. Thereby, they provide the means to determine factors limiting photosynthesis under different environmental conditions. However, their use is currently limited by the lack of efficient approaches to estimate the hundreds of kinetic parameters that may differ between genotypes. Here, we present an artificial neural network, which can efficiently predict parameters of a large-scale photosynthesis model from A/CO2  and A/light curves. The model was trained on a diverse artificial dataset comprising parameter samples and associated curve simulations from a dynamic C4  photosynthesis model. Model training was guided by considering both the predicted parameters and resulting curve simulations. To increase the efficiency of curve simulations during the training process, we trained a surrogate neural network to predict A/CO2  and A/light curves directly from the model parameters and environmental inputs. Despite the high sensitivity of the ODE model to changes in parameter values, over 99% of the predicted parameter vectors could be used directly by the kinetic model. Therefore, the developed framework presents a fast and precise approach for parameter estimation in large-scale photosynthesis models, based on minimal datasets. Further, the flexible structure of the model allows for an easy adjustment in the number of relevant parameters as well as the environmental inputs.

Efficient parameter estimation for a large-scale C4 photosynthesis model using neural networks

Inverse modelling allows estimation of stomatal conductance (by inverting the Penman Monteith equation), providing result well related to gas exchange indoor and in the field. Plant architecture, which determines radiation interception efficiency, can also be estimated both in the field and indoor, with good genetic correlations. Both have good heritabilities, present a large genetic variability in maize and can be predicted from genomic information. Furthermore, and unexpectedly, they were found to be well-related to yield measured in a multi-site field experiment: high stomatal conductance increased yield in favourable environmental scenarios only, whereas plant architecture increased yield in all scenarios. The consequences of these findings were analysed for 50 years of maize breeding in a multi site field experiment and in indoor platforms. While selecting for yield, breeders indirectly improved architectural traits and allelic frequencies at QTLs related to architecture changed with generations of selection. Conversely, stomatal conductance was similar in varieties released in 1950 and 2010, and allelic frequencies did not change. This is probably because selection for yield only favours traits that positively affect yield in nearly all experiments. Genomic selection for traits may be an alternative avenue. Stomatal conductance and plant architecture could be inferred in different fields, based on genotypic values obtained indoor and on environmental conditions in each considered field. Genomic prediction resulted in adequate ranking of genotypes for the tested traits, thereby opening the way for genomic selection.

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