Belgium

Extreme heat events are predicted to be more frequent and intense over the next few decades. Ectotherm early stages are particularly sensitive to such events due to their reliance on the external environment to perform their daily activities and maintain body temperature. Exposure to higher temperatures during fish development can increase mortality, growth rates, and may impact adult phenotypes. Yet very little is known about the early-life responses, interactions and developmental plasticity to thermal stress in aquatic species. In this study, we measured the photomotor response (PMR) of 1 day post fertilization zebrafish embryos at different rearing densities (10, 20, and 40 eggs), with and without regular social and heat-induced chemical cues. We found that embryos exposed to stress metabolites showed significant changes in PMR magnitude and recovery time, indicating they may detect and respond to stress-related chemical cues. Higher rearing densities were associated with lower activity, and the combined effects of thermal stress and stress metabolites resulted in a unique behavioral phenotype, suggesting interactions that may amplify the stress responses. Thus, we showed that zebrafish embryo activity is significantly affected by early life exposure to higher temperatures and that social cues may create a buffer when not directly exposed to thermal stress. Since the photomotor response can be a proxy for how well sensory information and motor actions are coordinated, rearing density and social cues emerge as important factors for understanding the response of developing fish to environmental stressors.

SEB Conference 2025

Sensing stress: Chemical communication in thermally stressed zebrafish embryos 

thermal stress

embryos

behavior

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SEB Conference 2024

SEB’s Annual Conference is celebrated for creating the perfect composition of research, new discoveries and collaborative connections. Be creative and innovative by exchanging ideas and knowledge with masters of biology from all over the world.

technical paper

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Kangaroo hopping is uniquely energetically efficient at slow speeds and small sizes, however, it is unknown how the locomotor performance of large or fast moving kangaroos compares to other animals. Hopping in giant kangaroos (>150 kg) may even be impossible or severely incumbered by tendon morphology. We built a musculoskeletal model of an average (27 kg) kangaroo and geometrically scaled it to various sizes between 10-650 kg. We implemented the models in a predictive simulation framework to generate hopping up to the maximum speed for each model. Contrary to expectations, tendon stress was not the predominant limit for either the maximum size or speed. Rather, maximum speed was limited by available muscle strength. Maximum speed declined with model mass as larger models were unable to support the increase in ground forces required to sustain higher speeds. Larger models also progressively lost the energetic advantage that small kangaroos appear to have over other mammals. The simulations predict that hopping consumes oxygen at a similar rate at slow and fast speeds, and –crucially– at the same mass-specific rate regardless of size. Other terrestrial species tend to decrease oxygen consumption with mass, leaving giant kangaroos at a competitive disadvantage. At larger sizes, hopping only becomes more energetically efficient than alternative gaits at progressively faster speeds. Together, these results suggest that poor energetic and speed performance may have contributed to the extinction of giant kangaroos.

Developing and utilising musculoskeletal models to predict the locomotor and energetic performance of hopping macropods

Biologging tags are used to understand wild animal movements for research, conservation and management. However, interpreting biologging data can be challenging owing to potential responses to capture and tagging (e.g. discomfort from invasive tag attachment), which may bias results. Fish possess sensory receptors that respond to painful stimuli, and local anaesthetics such as lidocaine have been shown to block nociception in fish, improving welfare and potentially reducing behavioural bias. Here, we explore the practicalities and effects of lidocaine use in wild Atlantic bluefin tuna (ABT), tagged with acoustic and/or pop-up satellite archival tags using intramuscular darts. Lidocaine was used on twenty-six ABT, a further fifty ABT did not receive lidocaine and were used as control individuals. Doses were administered at 0.1 ml/kg (2% lidocaine). ABT were either single (lidocaine n=11, control n=42) or double tagged (lidocaine n=15, control=8). Administration of lidocaine did not increase handling time on deck for single tagged ABT, but for double tagged fish, requiring two doses of lidocaine (one for each tag), handling time increased by 35% (mean = 3 minutes 47 seconds ± 34 seconds) compared to controls (mean = 2 minutes 39 seconds ± 28 seconds). Time required to conduct drug delivery also reduced with increasing researcher experience. The behaviour of fish receiving lidocaine remains under investigation, but preliminary results suggest by 30 days post-release, there are no differences in movement between groups. This cautiously suggests that lidocaine delivery can be used to improve welfare, without impacting tagging operations.

Lidocaine use in large pelagic fish research

Tuna associated with Fish Aggregating Devices (FADs) often exhibit higher proportions of empty stomachs and lower condition factors. However, it remains unclear whether this lower condition is a cause or a consequence of FAD association and whether the FAD-associated tuna condition is good or bad, due to the lack of fundamental knowledge on tuna physiology. This study aimed to quantify the physiological condition of tuna during food deprivation. 25 captive tuna individuals (FL: 31-71 cm) were initially fed ad libitum for 2 weeks and then subject to a controlled fasting period of 36 days. During fasting, 3 to 7 individuals were sampled at regular intervals (every 3-6 days) to assess various condition factors, including biometric parameters (e.g., Le Cren condition factor (Kₙ), hepatosomatic index (HSI), and girth length index (GL)), bioelectrical impedance analysis (BIA), body composition, and blood parameters. The results indicate that tuna initially mobilized the energy stored in the liver and then in the muscles. Three distinct phases of fasting were identified: Phase 1 (high HSI and Kₙ during ad libitum feeding and the early fasting days), Phase 2 (low HSI and high Kₙ, from days 4 to 14), and Phase 3 (low HSI and low Kₙ after 14 days of fasting). When comparing these results with condition factors measured on wild tuna associated with drifting FADs, it appears that all FAD-associated tuna fall within Phases 1 and 2. These results suggest that FAD-associated tuna do not attain the low Kn values observed during extended periods of fasting.

PHYSIOLOGICAL CONDITION OF YELLOWFIN TUNA CHARACTERIZED THROUGH A FASTING EXPERIMENT

Marine fish must overcome challenges associated with environmental stress by altering their physiology and behavior. This is of particular concern for larval fishes, which face exorbitant rates of predation and whose antipredation tactics may be reduced with available energy under warming. Increases in energy demand must be facilitated through simultaneously enhanced uptake of resources, which may result in increased risk-taking (e.g., boldness). In the adult sheepshead minnow, we have previously shown that warming reduces preference for dark substrate (scototaxis)—a behavior strongly present in the adult phenotype that aids in crypsis.  With this background, our objective was to assess changes in scototaxis behavior (light/dark preference) in larval sheepshead minnows reared at 25°C and 32°C at weekly intervals throughout development. Our larval data conforms with patterns seen in zebrafish where larvae across temperatures prefer the white substrate until 17 dph in opposition to the highly scototaxis adult phenotype, and these patterns may reflect changes in melanophores across development. Interestingly, larvae reared at 32°C at 10 dph demonstrated significantly greater white preference compared to larvae at 25°C and all other time points. We next sought to explore physiological drivers of individual variation at 10 dph using routine metabolic rate as a proxy for energetic demand, and cortisol as a measure of stress reactivity. Our data highlight that temperature impacts how highly vulnerable larval fish interact with their environment which may impact populations under intense predation.

Physiological drivers of scototaxis development in larval sheepshead minnows across two temperatures

When selective pressures for different functions act simultaneously on a structure, morphological diversification can be shaped by adaptation toward distinct functional optima. Systems may evolve along a performance gradient, optimizing different aspects of function in response to ecological demands.
We investigated two scorpion species representing the morphological extremes of chela (pincer) shape. Scorpion chelae exhibit remarkable morphological diversity associated with ecological roles, and their performance varies along a force-velocity continuum. To explore how structural and muscular adaptations shape performance, we developed a biomechanical model integrating synchrotron microtomography, muscle architecture, and performance data.
Our findings reveal that these species exhibit distinct structural and muscular arrangements, each optimized for a different performance outcome. The short-fingered species maximize closing force through increased mechanical advantage and longer sarcomeres, enhancing muscle contraction efficiency. In contrast, the slender-chela species optimizes closing velocity through muscle orientations that favor rapid acceleration. While additional functional demands likely influence these designs, one morphology appears specialized for quickly capturing prey, while the other seems to be adapted for prey crushing. These divergent performance optima may have played a key role in shaping the trophic ecology of scorpions and influencing the evolution of their venom.

Crushers and graspers: diversification of a musculoskeletal system toward two opposite functional optim

Global interest in studying the effects of endocrine disrupting compounds (EDCs) on neurodevelopment, causing developmental neurotoxicity, has grown. Research in mammals has identified EDC-induced impaired neurodevelopment as an adverse outcome (AO) targeting cochlear function, cognition, learning and memory. Research on fish however typically focuses on other adverse effects (e.g. swim bladder inflation, eye development). The present study therefore aims to determine the impact of EDCs on zebrafish early life stages by analyzing the mammalian AOs, cochlear function and learning and memory. Cochlear function was assessed via the lateral line (LL) system, a neurosensory system that senses water motion and pressure gradients. The functional units of the LL are neuromasts and contain hair cells (HCs), which are similar to HCs in the cochlea. Zebrafish embryos were exposed to EDCs for 5 days, after which the number of HCs and total neuromasts were counted. Targeted exposure windows and gene transcript levels were used to gain more detailed mechanistic understanding of observed effects. Learning and memory is studied via a forced turn larval T-maze behavioral assay. Zebrafish larvae exhibit spontaneous alternation behavior (SAB, i.e. the animal’s tendency to alternate turn direction in consecutive turns). By closing one arm of the T-maze, the animal should choose to explore the other arm on the next trial. This requires proper memory. Zebrafish embryos were exposed to a positive control and EDCs, after which SAB was assessed. Overall, this work aids in determining to which extent EDCs can affect neurodevelopment in zebrafish.

The effect of endocrine disrupting compounds on neurodevelopment in zebrafish early life stages

The mineral pattern in the skull forms intricate, dynamic, lace-like designs as osteoblasts spread across the head. These patterns emerge from fine-scale dynamics, but uncovering the underlying mechanisms is challenging without tools to quantify such complexity. To address this, we developed multifractal methods to measure self-similarity in these patterns. Using these tools, we constructed toy models suggesting that a collagen gradient alone is sufficient to generate the multifractal patterns of developing bone. Through live imaging, physical perturbations, and additional mathematical modeling, we confirmed that this collagen gradient arises from a self-propagating differentiation wave. More broadly, our mathematical framework for pattern quantification provides a generalizable approach for studying cross-scale interactions that drive spatial pattern formation, offering new ways to explore the fundamental mechanisms underlying spatiotemporal dynamics in living systems.

Ossification across scales guides emergent multifractal biomineral pattern in the skull

The Higher Education (HE) sector is undergoing a period of significant and rapid change as we grapple to respond to the post-pandemic landscape, political and economic uncertainty and significant technological developments. HE staff are facing increasing pressure to do more with less; to innovate and be exceptional and meet the needs of a rapidly changing student cohort. Teaching practices that may have been effective as little as 5 or 6 years ago, no longer necessarily reflect best practice. Finding the time and headspace to reflect on our practice, to innovate, adapt and evolve our pedagogical ideas is a sector-wide challenge. And the constant pursuit of teaching excellence is impacting the experiences of both staff and students. We are living to the words of Alice in Wonderland’s Red Queen “It takes all the running you can do to keep in the same place”
In this session, I will share examples of some of the strategies that I have developed within my own practice to enhance the student experience. The strategies are all grounded in relational pedagogy and include evaluating practical skills competency at the start of a course as well as changes to assessments and multiple ‘quick wins’ embedded within teaching that also serve to support student wellbeing. The strategies that I will share can be used by anyone teaching within HE across any level of study.

Quick wins to enhance the student experience

Stomata regulate plant water balance, carbon exchange, and defense mechanisms, while also affecting bioactive compound production. Their density and behavior impact crop resilience, productivity, and adaptation to climate change, making stomatal analysis essential in plant breeding, agroindustry, pharmacology, and forestry. However, conventional imaging methods remain labor-intensive and time-consuming.
We offer real-time, high-throughput solutions for automated stomatal analysis, from density assessments to morphological and open/closed status evaluations. Designed for greenhouses, growth chambers, and field applications, our two complementary technologies redefine stomatal imaging:
STOMmini– A smartphone-based tool capable of analyzing up to 1,000 stomata per image, depending on species and magnification. It provides automated measurements of density, size, shape, and clustering index, offering instant insights into stomatal organization.
PHENOM– A portable, modular microscope for real-time stomatal imaging. It delivers high-resolution imaging and can be seamlessly deployed across diverse environments.
Both solutions are non-destructive and integrate AI-driven automation, transforming stomatal analysis from a tedious manual task into a scalable, high-throughput process. Validated across multiple crops, our approach empowers researchers and breeders with unprecedented precision, from whole-leaf assessments to single-stoma resolution.

Cutting-Edge Solutions for Real-Time, High-Throughput Stomatal Imaging and Analysis

Improving the efficiency of converting light energy into organic biomass has been identified as a key factor required to increase crop yield. Classical kinetic models of photosynthesis have helped identify rate limiting steps of photosynthesis and have helped engineering efforts on this front. However, kinetic models are computationally expensive and depend on detailed information about kinetic laws, metabolite, and enzyme concentrations, which limits their scope. In contrast, constraint-based models of leaf metabolism are less data-reliant and can account for the entire leaf metabolism, making them a promising alternative for studying steady-state leaf metabolism. In my talk I will describe how constraint-based modeling works and how such models can be used to study metabolism in C3 and CAM leaves. I will also discuss our recent efforts in using this modeling approach to search for potential strategies to increase efficiency of tomato leaf metabolism. Our analysis revealed that a switch in the activity of glutamine synthetase (GS) from the chloroplast to the mitochondria could help a leaf achieve higher productivity. To further explore this prediction, transgenic tomato plants over-expressing GS in leaf mitochondria were generated. These plants exhibited faster growth rate and increased fruit yield. Leaf metabolomic profiling and enzyme activity analysis also showed GS activity in mitochondria played a role in enhancing the synthesis and export of sugar from the leaves. These findings increase our confidence in the use of constraint-based modeling as a viable approach for designing engineering strategies aimed at improving crop productivity.

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