Belgium

Invasive species are organisms that spread, often human-mediated, from their native range into novel environments where they become established and often cause ecological (and economic) damage, including competition with native species for space, food, and survival. One of these species is the round goby (Neogobius melanostomus), a fish introduced into both fresh and brackish waters around the world. To understand how round goby will perform in the ocean, if they continue to spread into this higher-salinity environment, we investigated how individuals differ in their physiological and behavioural (co)sensitivity to changes in salinity. We measured the physiology (metabolic rates, growth) and behaviour (activity, dispersal, exploration) of 77 individual round goby after acclimation to each of five salinities (0, 10, 19, 24, 28 ppt) in the laboratory and quantified trait variation and sensitivity to salinity as their reaction norm intercepts (at 10 ppt) and slopes. We find that the fastest-growing individuals at 10 ppt—the salinity the fish were caught at—are also the most behaviourally active and explorative at this salinity, and thus more likely to spread to new locations and dominate. However, at salinities higher than 15 ppt, these individuals lose their growth advantage and are faced with the most severe reductions in aerobic metabolic scope relative to conspecifics. This cross-over at 15 ppt for which phenotypes have the performance advantage is likely to determine the trait composition of round goby populations, the selective pressures acting on these (combinations of) traits, and thus the continued invasion success of the species.

SEB Conference 2025

Individuals of the invasive round goby face physiological and behavioural trade-offs in their sensitivity to salinity

metabolic rate and behaviour

fish ecophysiology

invasive species

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technical paper

Biologging physiological variables in free-living animals is crucial for conservation but presents practical and technological challenges. Implanted biologgers enable long-term data collection but require surgical or post-mortem retrieval. Wireless data transmission enables periodic data collection without explantation. In this study we tested a wireless temperature biologger. Wireless biologgers (mass 10g) were inserted into the rumens of three sheep, where they remained for two weeks. Attempts to download data were made every five days at 1m intervals, from 0 to 5m from the sheep. To compare performance with a validated non-wireless model (mass 2g), a wireless and non-wireless biologger combined in one unit was inserted into the rumen of two sheep and implanted retroperitoneally in two African buffalo. Biologgers were recovered post-slaughter (sheep) or after predation (buffalo). The wireless biologgers in the rumen of sheep downloaded successfully, with 1440 data points downloaded within 10s from up to 2m away. The wireless biologgers were accurate and precise (bias -0.004°C to -0.002°C; SD 0.048°C to 0.090°C), with 99% of paired recordings differing by ≤0.05°C. The limits of agreement between temperature measurement methods ranged from -0.18°C to 0.17°C and were influenced by sudden decreases in temperature associated with drinking, with the larger wireless biologger exhibiting greater thermal inertia and responding more slowly. Both biologgers from predated buffalo were found in the field (using received signal strength indication) despite no carcass recovery, with wireless signals detected up to 45m away. Our study demonstrates the reliability and applicability of wireless biologgers for remote body temperature monitoring.

No strings attached: Wireless temperature biologgers to improve remote physiological data collection

Maintenance metabolism, or standard metabolic rate (SMR), is an important metric for understanding the baseline metabolic requirements of animals and is measured on fasted, resting individuals. Ongoing debate surrounds some of the practicalities and interpretations of measuring SMR in juvenile animals, especially fish, as it can be argued that even fasted juvenile animals will maintain some level of metabolic activity associated with “background” growth. Equally, there is little consensus around the role of reproductive maturation in influencing the measurement and interpretation of SMR.
Here, we take three large datasets on Galaxias maculatus, a diadromous fish species with a pelagic oceanic larval phase, to assess differences in SMR in differentially growing individuals as they transition from juveniles to reproductive adults across four acclimation temperature treatments (15, 18, 20, and 23 °C). We predict that if growth and/or the level of reproductive maturation are significant drivers of variability in SMR, there will be positive relationships between mass-standardised SMR and individual growth phenotypes and/or gonadal volume.
Linear regression analyses showed that individual growth phenotypes had negligible influence on the magnitude or variability in SMR, suggesting that SMR measurements of fasted juvenile fish are not detectably impacted by growth. We also found no clear evidence of a positive relationship between SMR and level of reproductive maturation, raising questions around the energetic burden of reproduction on fish. It has been suggested that metabolism, growth and reproductive investment are co-evolved to maximize lifetime fitness, and we encourage further research into the complicated nature of this relationship.

Life History Attributes Influencing Metabolic Variation in an Estuarine Fish

Stressors such as artificial light-at-night (ALAN) affect both terrestrial and aquatic systems and are often associated with increased infrastructure and development. Coral reefs, which are often close to areas of rapid coastal development, are therefore prone to significant exposure to these stressors, however, the metabolic and behavioural effects of ALAN on coral reef fish are somewhat understudied. In this study, we used virtual reality (VR) to visually simulate exposure to various cues in two reef fish, Amphiprion chrysopterus and Dascyllus trimaculatus. Behavioural data was collected during and after exposure to a sandy environment (baseline) and simulated stimuli (conspecific, heterospecific, and predator) in fish previously exposed either to ALAN or to ambient light levels (control). In addition, for A. chrysopterus, metabolic and activity data were collected during and after exposure to a simulated predator. In behavioural trials, ALAN-exposed fish tended to be less risk averse, showing greater tendency to approach heterospecifics and predators. In behavioural trials in A. chrysopterus, ALAN-exposed fish were more active when exposed to a baseline stimulus but did not show an activity increase in response to stimuli, while control fish increased activity level. In respirometry trials, activity level was significantly reduced in both control and ALAN-exposed A. chrysopterus when exposed to a predator cue. Metabolic rate, however, was reduced significantly more in control compared with ALAN-exposed fish, during and after exposure. ALAN-exposed fish overall appear to be less responsive to predator cues, possibly due to higher metabolic demand associated with increased nocturnal activity leading to greater risk-taking.

Effects of artificial light-at-night on metabolic and behavioural response to simulated stimuli in reef fish 

Biomineralization is an evolutionary ancient process found in many marine organisms including the sea urchin larva that form a delicate calcium carbonate skeleton. Calcium and carbonate ions are taken up into vesicles via endocytosis of seawater by the calcifying Primary Mesenchyme Cells (PMCs). Here the amorphous precursor is formed and ultimately exocytosed. However, calcium and carbonate ions only make up about 4.70 % and 0.23 % of the seawater ion composition respectively. To promote calcification, the substrates must be concentrated and seawater and its redundant ions e.g. sodium and chloride removed. However, the underlying mechanisms remain unknown.
Using the sea urchin larva, we investigated the role of the Na-K-Cl (NKCC) cotransporter in promoting salt transport in PMCs. Single cell transcriptomic analyses demonstrated this ion transporter to be mainly expressed within these calcifying cells. Using in vivo confocal microscopy in combination with the specific NKCC inhibitor azosemide we investigated its role in the process of spicule formation during early development. Larvae treated with azosemide showed impaired spicule formation and developed strikingly shorter spicules compared to control conditions. Tracking of calcium incorporation using the calcium-binding dye calcein confirmed reduced mineral deposition rates in the presence of azosemide. Gene expression analyses of this transporter revealed an upregulation during recalcification of the larval skeleton.
These findings suggest that the NKCC cotransporter plays a crucial role for calcification and shed light onto novel vesicular mechanisms of mineralization in echinoderms that are important ecosystem engineers in marine habitats.

Vesicular salt transport mechanisms are crucial for calcification in sea urchin larvae

Background
The increasing demand for local food production is fueling high interest in the development of controlled environment agriculture. In particular, LED technology brings energy-saving advantages together with the possibility to manipulate plant phenotypes through light quality control. However, optimizing light quality is required for each cultivated plant and specific purpose. 
Findings
In this work, it is shown that the combination of LED gradient setups with imaging-based, non-destructive plant phenotyping constitutes an interesting screening tool with the potential to improve speed, logistics, and information output. To validate this concept, an experiment was performed to evaluate the effects of Red:Blue ratio on seven plant species: Arabidopsis thaliana, Brachypodium distachyon, Euphorbia peplus, Ocimum basilicum, Oryza sativa, Solanum lycopersicum, and Setaria viridis. Plants were exposed during thirty days to the light gradient and showed significant, but species-dependent, responses in terms of dimension, shape, and color. A time series analysis of phenotypic descriptors highlighted growth changes but also transient responses of plant shapes to the Red:Blue ratio. A workflow for generating simple intuitive graphical representation of complex phenotypic data is proposed.
Conclusion
This approach, which generated a large reusable dataset, can be adapted for addressing specific needs in crop production or fundamental questions in photobiology.

Phenotyping plant responses to light quality with color gradients

Mungbean (Vigna radiataL.), a valuable sub-tropical grain legume, typically exhibits an extended, asynchronous flowering window, complicating harvest and increasing vulnerability to abiotic stress. To facilitate breeding efforts, we conducted multi-environment trials across four field experiments in Queensland, Australia (2022-2023), evaluating days to flowering (DTF) and the novel trait flowering duration (FD). Extensive phenotypic variation was observed for DTF (35-70 days after sowing) and FD (20-60 days after sowing), with genotype-by-environment interactions influencing both traits, particularly FD. No relationship was evident between DTF and FD across environments. Genome-wide association studies identified eight quantitative trait loci (QTL) for DTF and one for FD, with no overlapping QTL, further demonstrating that these traits are genetically independent. The accumulation of early or late alleles at DTF QTL explained variations in flowering time, providing actionable insights for breeding programs.
To further dissect flowering mechanisms, controlled environment studies under varying photoperiods (short, neutral, and long) assessed how photoperiod influences flowering initiation, duration, and overall behaviour across a diverse panel of breeding germplasm and genebank accessions. These experiments, combined with shoot tip dissection examined shifts in flowering characteristics underpinning resilience and adaptability and the transition from vegetative to reproductive stages in mungbean.
Our integrated field and controlled-environment approach offers novel pathways to improve mungbean for enhanced food security, environmental sustainability, and climate resilience. This foundational understanding of mungbean flowering traits provides a mechanistic basis for developing varieties with synchronised and optimised flowering patterns, crucial for improving adaptation to diverse agricultural environments under climate change.

Time to flowering and flowering duration in mungbean are unrelated physiological traits with independent genetic controls

Plant Factories with Artificial Lighting (PFAL) are a sustainable alternative to conventional agriculture for producing plants used in food, cosmetics, pharmaceuticals, and nutraceuticals. Standard PFALs rely on horizontal cultivation layers, requiring a high number of lamps to ensure uniform lighting, leading to high light-related energy consumption. To reduce energy consumption, an innovative rotational cultivation system has emerged. The rotation is slow, and plant physiology in the context of growing in a continuous slow rotation has not been studied before. The present work aims to provide insights into physiology, metabolism, morphology and agronomical performance of lettuce or basil plants grown in a rotational cultivation system. The position of statoliths in basil grown in the rotational cultivation system consistently aligned with the gravity vector, suggesting the plants' ability to perceive changes in gravity orientation. This was consistent with the observed changes in plant morphology. Photosynthesis of lettuce was affected by changes in stomatal conductance and photosystem II efficiency. The profile of primary and secondary metabolites differed from those of control lettuces grown in a horizontal cultivation layer, notably in terms of polyphenol content. Despite these physiological and metabolic modifications, yield remained unchanged, and similar values of Water and Light Use Efficiencies (WUE and LUE) were found between lettuces grown in the rotational and horizontal cultivation systems. This study provides new insights into plant physiology and agronomic performance under slow rotational cultivation in PFALs, with implications for understanding plant responses to altered gravity perception, such as in microgravity environments.

Cultivating plants in rotational systems: insights into the interaction between gravity perception, metabolism and agronomic performance in PFALs

Global warming is predicted to cause an increased incidence in both, summer droughts, and excessive rainfall and flooding events in winter and early spring months. Existing plants can be adapted to survive and produce high yields in these future climates, through the enhancement of existing characteristics responsible for combating drought and excess water presence. This project investigates the genes responsible for regulating key perennial ryegrass (PRG) root architecture traits such as root length, while identifying the genetic loci responsible. A diverse set of PRG genotypes were compared from an initial screen of 200, which possessed varied root phenotypes. Rhizoboxes and RNA sequencing were used to analyse phenotypic and transcriptomic data. Phenotyping methods including 3D structural analysis using CT scanning and photographic analysis using a range of 2D imaging software are being employed. Near-isogenic-lines (NILs) are being developed to select for the activations or suppression of key identified genes, to analyse their effects on PRG root architecture. Future work will identify the presence of single nucleotide polymorphisms (SNPs) through whole genome sequencing. This will be used in combination with transcriptomic data to correlate SNPs presence in certain genes to variations in their transcription levels across different PRG genotypes. Correlated SNPs presence and variations in RNA-sequencing data will then be jointly correlated to alterations in PRG root architecture across NILs. Understanding the underpinning gene networks responsible for variations in both abiotic resistance and root architecture will allow for the identification of genetic markers which can be targeted to inform future breeding strategies.

Linking Genome Diversity to Root Architecture and Growth Dynamics in Perennial Ryegrass

It is challenging to isolate the causative effects of single sources of selection in nature, because environments are often complex with different selective pressures covarying along environmental gradients. For instance, sulfidic springs are characterized by high levels of toxic hydrogen sulfide (H2 S) and low levels of oxygen in comparison to nearby non-sulfidic sites, which are normoxic. However, previous studies on fish in these systems have focused primarily on the effect of H2 S on gene expression, while hypoxia is also known to strongly shape gene expression in aquatic organisms. Members of the Poecilia mexicana species complex have repeatedly colonized sulfidic springs in Costa Rica and Mexico. We compared hypoxia tolerance and gene expression after exposure to acute hypoxia in three sulfidic populations and three non-sulfidic populations. We found that fish from sulfidic environments were generally more tolerant of hypoxia. We also found evidence for shared gene expression responses to acute hypoxia across sulfidic and nonsulfidic populations, despite contrasting habitat types and large geographic distances between populations. Our research suggests that acute hypoxia tolerance in both non-sulfidic and sulfidic populations is facilitated by upregulation of genes associated with oxygen sensing, oxygen delivery, and cardiac function. Our studies sheds light on the ancestral responses to hypoxia in this species complex and sets the stage for future studies that consider the simultaneous effects of H2 S and hypoxia on gene expression.

Effects of Acute Hypoxia Exposure on Gene Expression in an Extremophile Fish

The use ofex situconservation to establish assurance colonies is on the rise as global biodiversity decline. However, assurance colonies need to maintain a high biomass to preserve genetic diversity in captive breeding programs. With technological advancements, gamete cryopreservation can be used to preserve genetic diversity while minimizing maintenance of captive live animals. However, it is still unclear whether gamete cryopreservation impacts fish fitness. Using the established Live Gene Bank for endangered Inner Bay of Fundy Atlantic Salmon (Salmo salar), we assess whether sperm cryopreservation impacts fertilization success, survival, and offspring phenotype over two years. Egg clutches from each female were split in half and fertilized with either fresh or cryopreserved sperm from the same male to reduce parental effects. Cryopreserved sperm significantly reduced fertilization success, as well as embryo and alevin survival. Cryo-derived individuals at 50% hatch were shorter and had smaller yolk-sac area. However, at this timepoint, there was no impact of cryopreservation on global DNA methylation. At first feeding, cryo-derived individuals were significantly larger nevertheless there was no differences in length, mass, or condition factor at later life-stages. This study demonstrates that despite differences in cryo-derived morphometrics at early-life stages, cryopreservation appears to have minimal impact on morphometrics at later life stages, implying individuals could have similar post-release survivorship and reproductive output. Our findings suggest that cryopreservation of sperm can be a useful technique for Inner Bay of Fundy Atlantic Salmon, although further research is needed to assess other fitness metrics and generational impacts.

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No strings attached: Wireless temperature biologgers to improve remote physiological data collection

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Investigating the phenotypic drivers of the invasion dynamic in round goby