Belgium

Parasites can impair host performance through various physiological processes, including alterations to host metabolism. Since mitochondria are responsible for cellular energy production, it is likely that disruptions in host cellular metabolism contribute to changes in metabolism at the organismal level. However, some studies investigating parasite-induced alteration in cellular metabolism have been limited by the presence of parasites in the target tissues. Before analyzing these key tissues, it is critical to confirm that the measured enzyme activities reflect those of the hosts rather than the parasites themselves. Here, we tested a parasite extraction protocol to evaluate the extent to which parasite contamination impacts estimates of cellular enzyme activities in hepatic tissues of wild pumpkinseed sunfish (Lepomis gibbosus) infected with bass tapeworm (Proteocephalus ambloplitis). We tested four treatments: uninfected livers, cleaned infected livers, infected livers (repopulated) and parasites alone. We then compared the activity of key metabolic enzymes among groups. PCR tests were used to assess parasitic contamination after applying the parasite extraction protocol on hepatic tissue. Enzyme activities of cleaned livers and contaminated livers were similar even if PCR tests revealed contamination. The intensity of cestode infection also did not influence enzyme activity, which suggests that parasite presence in the livers does not impact the accuracy of the enzyme activity estimates made. Through this protocol, we show that parasite contamination has no effect on metabolism measurements showing that the study of parasitized organs is possible. We also recommend the use of this protocol to avoid any biases in highly infected individuals.

SEB Conference 2025

Mitochondrial enzyme activity in fish livers is not impacted by parasite presence

host-parasite interactions

dna contamination

endoparasite

helminth infection

freshwater fish

cellular metabolism

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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.

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Climate change represents one major challenge for avian species. It is characterized by an increase in average ambient temperature, 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. Yet, early-life telomere length has been suggested as a potential biomarker of fitness prospects. To evaluate the potential impact of changes in early-life temperature, we thus experimentally increased (ca.+2°C) and decreased (ca.-1.5°C) 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 suggests that long-term survival prospects or long-term performance of individuals exposed to abrupt changes in early-life temperature may be decreased.

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

Early development is highly sensitive to environmental stressors, with temperature shaping phenotypic trajectories in ectotherms. This study examines thermal plasticity in craniofacial development of two desert vipers,Cerastes cerastes(horned viper) and Cerastes vipera(non-horned viper). Adapted to arid extremes, they offer a model to explore how temperature-driven disruptions may cause phenotype-environment mismatches under climate change.
Eggs were incubated at 22°C, 28°C, and 34°C (15 per species/treatment) to simulate desert temperatures. Growth was tracked via photogrammetry and linear morphometrics, including snout-vent and horn length. Skeletal development was assessed using Alizarin Red staining, while qPCR quantified osteogenic markers BMP2 and RUNX2.
C. cerastesshowed strong thermal plasticity: at 34°C, horn length increased 42% vs. 28°C, with accelerated ossification and 31% higher bone density. BMP2 and RUNX2 were upregulated 3.2- and 2.8-fold, linking thermal stress to osteogenesis.C. viperashowed no significant morphological or molecular changes, highlighting species-specific vulnerability.
These results show that thermal stress during embryogenesis shapes craniofacial traits via conserved osteogenic pathways. However, exaggerated horns at high temperatures may hinder burrowing or predator avoidance inC. cerastes, illustrating potential maladaptation in warming deserts. This study integrates experimental and evolutionary approaches to predict phenotype-environment mismatches and identify molecular targets, like BMP signalling, for resilience in thermally sensitive ectotherms.
Keywords: Experimental Developmental Biology, Thermal Plasticity, Osteogenic Pathways, Climate Resilience,Thermo-morphogenesis.

Desert Vipers of the GenusCerastesas a Model for Temperature-Dependent Craniofacial Development: A Morpho-Molecular Analysis

Semi-aquatic mammals have evolved adaptations for aquatic locomotion, an activity which differs greatly from terrestrial locomotion due to the denser and more viscous medium. Furthermore, semi-aquatic species cannot fully specialise since they need to balance their adaptations to fit their needs in both environments. Mustelids provide a valuable model for studying the evolution of such adaptations, as the group encompasses a wide range of aquatic specializations. Previous studies on their skeletal limb anatomy suggest a correlation between increased robustness and the higher biomechanical demands of swimming. To meet the elevated force requirements of swimming, we hypothesize that skeletal changes are accompanied by modifications in muscle architecture, specifically an increase in force-generating potential in distal limb muscles. To investigate this, we conducted manual dissections to measure muscle mass, fascicle length, pennation angle and to calculate the physiological cross-sectional area (PCSA). PCSA and fascicle length serve as indicators of specialization for either high force generation or increased contraction speed, providing a quantitative insight into muscle  performance potential. The next phase is to link these anatomical adaptations to specific functional demands of aquatic (and terrestrial) locomotion. Future steps involve gathering kinematic data of terrestrial and aquatic locomotion in live animals and modelling these locomotor patterns. By integrating anatomical and functional data across a gradient of aquatic specialization in mustelids (fully terrestrial ferrets < infrequently aquatic minks < habitually aquatic otters), this study aims to enhance our understanding of the evolution of aquatic locomotion in mustelids and, more broadly, in mammals.

Comparative muscle architecture in (semi-aquatic) mustelids and subsequent steps to identify musculoskeletal adaptations for aquatic locomotion

Birds rely on their beak as a versatile, multi-functional tool during various behaviours. Depending on a bird’s ecology, a beak may be specialised for producing high bite forces (e.g., to break down hard food items) or fast oscillation rates (e.g., to produce elaborate birdsong). Previous studies indicated that high bite force and fast beak movements oppose one-another, suggesting a force-velocity trade-off. However, the underlying mechanisms contributing to this trade-off in songbirds have not been studied in detail. We hypothesise that the contractile properties of the avian jaw muscles, specifically their normalised rates of force rise during contraction and force decay during relaxation, are a limiting factor for maximal beak oscillation rates. To test our hypothesis, we measured the tetanic, isometric half-contraction and half-relaxation times of beak opener and beak closer muscles in a weak biting (canary) and a hard biting (Java sparrow) songbird in vitro. We observed that, in the harder biting species, both muscle types are slower in contraction and relaxation. Furthermore, within both species, beak closer muscles were slower in contraction and relaxation compared to beak opener muscles. We conclude that muscles which are adapted to high force production need more time to contract and relax compared to muscles producing low maximal forces. These findings suggest that the contractile properties of avian jaw musculature may contribute to the observed force-velocity trade-off in songbird beak movements. Our results further suggest that the muscles involved in forceful biting may contain a greater proportion of slow, fatigue-resistant fibres.

Contractile properties of jaw muscles contribute to force-velocity trade-off in beak movements of songbirds

Mammals with a cursorial lifestyle exhibit elongated distal limb bones and generally more hinge-like joints in the limbs. Elongated limbs and other cursorial traits have been shown to reduce locomotion costs, but the role of hinge-like joints has not been examined independently. Hinge-like joints stabilize the limb against sideways excursion and restrict movement to a single (parasagittal) plane. Thus, it has been suggested that this enhances locomotor efficiency, due to a reduction of required muscular joint control. However, this assumption has not been explicitly tested in relation to hinge-like joints, independent of other cursorial adaptations.
Here, we first aim to assess the hinge-like nature of elbows in mammals of various locomotor types. We will quantify the restriction to a single axis of rotation in the humero-radial joint of cursorial species by measuring and comparing the osteological range of pronation and supination. Next, we evaluate locomotor efficiency during steady-state locomotion by comparing in vivo ground reaction forces (GRF) in the same species. We expect cursorial species to exhibit relatively lower medio-lateral forces. This will indicate how efficiently GRF are channeled unidirectionally in the fore-aft direction during steady-state locomotion. Additionally, to determine whether increased hinge-like morphology corresponds to more unidirectional stresses on elbow bones, we will analyze anisotropy in the trabecular structure of the humerus, ulna, and radius. We expect cursorial species to exhibit lower anisotropy. This study contributes to the understanding of the interface of form and function in mammalian cursorial locomotion.

Do hinge-like joints really aid in more efficient locomotion?
Ground reaction forces and bone microstructure in cursorial mammals

Small birds use a distinct pattern of intermittent flight known as ‘flap-bounding’, distinguished by alternating phases of rapid flapping and tucked-wing ballistic movement. Previous theoretical and experimental studies suggest that this behaviour reduces energetic costs or regulates horizontal velocity during long flights. However, we observed zebra finches using flap-bounding even during short perch-to-perch flights. Furthermore, individuals converged on a consistent flight path with training, initiating the bound at a specific point in their trajectory. To investigate what objectives are driving this learned behaviour, we developed an analytical model of flap-bounding and applied a gradient-free optimisation method to test multiple hypothesized objectives: minimising energy, minimising flight time, minimising or maximising bounding duration, minimising bounding velocity, and minimising landing deceleration. By comparing the optimised trajectories to experimental data, our results suggest that the learned trajectory is not dictated by a single objective but instead represents a compromise among competing performance goals. While future work will refine the analytical model with more complexity, these findings demonstrate that during short flights, zebra finches choose trajectories that balance multiple, potentially contradictory, goals.

The finch formula: decoding flap-bounding tactics during flight training 

Jumping performance is a key locomotor trait that is shaped by both evolutionary processes and allometric laws. It acts as predominant mode of locomotion in grasshoppers, locusts, crickets and katydids, thus playing a critical role in behaviors such as predator evasion, mate search, and navigation through complex environments. In this study, we aimed to explore how jumping performance scales allometrically and evolved across different Orthopteran lineages differing in their ecological niches. By comparing 12 Caelifera and 7 Ensifera species in a phylogenetic comparative framework, we investigated how jump kinematics vary with body size, jump actuation mechanisms, and ecological adaptation. Specifically, we assessed parameters such as maximum and mean take-off velocity, acceleration, jump height and distance, as well as jump-off force and power, while considering the influence of body mass. Preliminary results indicate that Caelifera exhibit higher jumping performance with lower body mass compared to Ensifera. We conclude that evolutionary pressures related to habitat and ecological function drives variations in jumping performance across species, with allometric scaling differing between taxa.
Keywords: Jumping performance, Allometry, Locomotor traits, Orthopteran taxa, Locomotion evolution

Evoution and Allometric Scaling of Jumping Peformance in Orthopterans

Artificial light at night (ALAN) is increasingly present in both terrestrial and aquatic systems and has been found to influence physiological and behavioural traits in wild animals in a range of habitats. In coral reef ecosystems, increasing human pressure often leads to more coastal infrastructure and boat traffic, resulting in an increase in ALAN exposure for reef organisms. Here, we aimed to investigate the effects of chronic ALAN exposure on social behaviour and risk-taking in a gregarious coral reef fish, Dascyllus trimaculatus. Wild fish were collected from sites containing both ALAN-exposed and control (ambient light levels) anemones around Moorea, French Polynesia. Fish underwent a three-chamber shoal choice test to assess diurnal sociability, followed by an emergence test to assess diurnal risk-taking behaviour. Activity levels were measured during both tests. No effect of ALAN exposure was found on daytime social behaviour or activity level. ALAN-exposed fish were, however, found to take less time to emerge from an anemone after a chase stimulus compared with control fish. The differences in risk-taking may be due to direct effects of ALAN exposure on risk-taking behaviour, or selective mortality of more risk-averse individuals, both potentially driven by increased nighttime activity levels during ALAN exposure. Increased nighttime activity may lead to increasing metabolic needs, driving increased risk-taking, or could lead to more risk-averse fish facing an increased risk of starvation or reduced growth. Our study adds to the existing literature and provides the first evidence that chronic ALAN exposure increases risk-taking behaviour in a marine fish.

Effects of artificial light-at-night on the diurnal risk-taking behaviour of a gregarious reef fish

A particularly concerning group of environmental contaminants are endocrine-disrupting chemicals (EDCs) that can interfere with the endocrine system by mimicking or blocking endogenous hormones. Disruption of hypothalamus-pituitary-axes (HP-axes) can lead to serious health problems, e.g., thyroid malfunctioning (HPT-axis), interference with reproduction (HPG-axis), impaired stress response (HPI-axis), as well as (neuro)behavioural changes. As a rule, organisms are continuously exposed to multiple EDCs simultaneously, since EDCs deriving from cosmetics, packaging, pesticides, food, and other everyday products, end up in the environment. This urges the need to assess the physiological impact of EDC mixtures and to understand the mechanisms and targets affected. The zebrafish (Danio rerio) is a particularly suitable preclinical model to assess these toxicological effects for several reasons. Firstly, their rapid development can be easily non-invasively monitored due to its transparent body. Secondly, the zebrafish is a vertebrate species with a surprisingly high degree of homology to humans with respect to organ systems, physiology, genomics, and behaviour. Indeed, the model can be used to understand molecular mechanisms and targets given its fully annotated genome, ease of genomic manipulation, as well as a wide array of already available transgenic reporter lines of hypothalamus-pituitary-axes biomarkers, and well-characterised behavioural assays. Together, these provide valuable insights into molecular mechanisms and natural behaviour, survival, and reproductive success, all of which are highly relevant for understanding the impact of EDCs. In this study, we assess the impact of various EDC mixtures on the HP-axes of zebrafish from a molecular, physiological, and behavioural point of view.

Zebrafish (Danio rerio): a quick and versatile preclinical model to screen effects of endocrine-disrupting chemicals (EDCs). 

Pollutants drive adaptive metabolic and evolutionary responses. However, this pollution-driven rapid evolution in invertebrates, particularly its effects on metabolism and mitochondrial oxidative phosphorylation (OXPHOS), remains overlooked. Using the European green crab Carcinus maenas, we investigated: (i) whether historic exposure to cadmium induces adaptive metabolic and mitochondrial responses; and (ii) if pre-exposure to cadmium confers protection from another source of pollution, copper. Crabs were captured from the wild from one site exposed to cadmium pollution but naïve to copper and a second reference site which had no cadmium or copper. After four months of depuration, animals were exposed to either 8.2 nM cadmium, or 20 nM copper-hydrate, or clean seawater. Mitochondrial respiration in heart homogenates was measured using high performance respirometry (Oroboros). Reactive oxygen species production (ROS) and antioxidant content was measured in hemolymph spectrofluorometrically (C-H2 DFFDA) and electrochemically (BRS system), respectively. While all crabs showed similar mitochondrial routine respiration values, the historically polluted crabs had higher OXPHOS respiration, higher electron transport system capacity, and enhanced capacity of complex II (CII), accompanied by increased ROS formation and higher antioxidant defences. Exposure to cadmium or copper did not affect any of the parameters considered in historically polluted crabs. In contrast, reference animals responded with a decreased complex I (CI) and increased CII contribution. This may reduce CI-associated ROS formation while enabling detoxification and (or) other defence mechanisms. Our findings suggest that long-term metal exposure induces mitochondrial adaptations that enhance resilience to pollution, potentially facilitating the invasion success of C. maenas in contaminated environments.

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