Belgium

It has been proposed that larger individuals within fish species may be more sensitive to global warming, as a result of limitations in their capacity to provide oxygen for aerobic metabolic activities. This could affect size distributions of populations in a warmer world but requires investigation. We studied four groups of individuals over a ~10-fold range in mass (20 – 800 g overall), two farmed species, Nile tilapia (Oreochromis niloticus) and European seabass (Dicentrarchus labrax), and two species captured in the wild, European seabass and gilthead seabream (Sparus aurata). In all groups, capacity to provide oxygen for aerobic activities (Absolute Aerobic Scope) was independent of mass at their acclimation temperature. Tolerance of acute warming, however, declined significantly with mass in all groups, when evaluated as the critical temperature for fatigue from aerobic swimming (CTSmax ). The CTSmax  protocol challenges a fish to meet the oxygen demands of constant aerobic exercise while their metabolic demands are accelerated by incremental warming, until fatigue. The maximum rates achieved prior to fatigue declined very significantly with mass. Mass-related variation in CTSmax  and maximum oxygen uptake rates were positively related in all groups, which may indicate a causal relationship. When fish populations are faced with acute thermal stress, larger individuals may become constrained in their ability to perform aerobic activities at lower temperatures than smaller conspecifics. This could affect survival and fitness of larger fish in a future world with more frequent and extreme heatwaves, with consequences for population productivity.

SEB Conference 2025

Evidence that tolerance of acute warming declines with increasing body mass in fishes

thermal tolerance ; ctsmax ; swimming respirometry

technical paper

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Ocean warming is a major threat to shallow water marine communities, particularly their invertebrate species, whose biological rates are temperature dependent. Accurately predicting their fate in the face of ongoing warming will require to account for biological variation, particularly between males and females, of which we currently have little understanding. We experimentally evaluated the physiological and metabolomic responses, as well as reproductive output, of the marine amphipod Gammarus locusta exposed to a temperature gradient. Females and males were collected from a coastal lagoon subjected to four acclimation temperatures (16, 21, 26 and 31 ºC) for 21 days. Specimens were individually sampled for metabolomics profiling. Additionally, Critical Thermal Maximum (CTMax), thermal safety margins and acclimation response ratio were assessed in different specimens at day 21. Higher exposure temperatures led to higher CTMax, confirming thatG. locustais capable to adjust its CTMax via physiological plasticity. A positive thermal safety margin was found, and females displayed higher CTMax than males, suggesting that thermal tolerance is sex dependent. Additionally, offsprings number was significantly reduced at higher temperatures, suggesting negative impacts of OW on fecundity. Further metabolomics analysis will be performed to assess test the hypothesis that warming causes females to enhance energy production via TCA cycle and amino acid metabolism more than males to support heat stress and reproductive costs. We conclude that G. locusta is physiologically plastic, females being more plastic than males, but that population viability may still be at risk due to reduced reproductive output under OW.

The Battle of the Sexes: Male and Female Amphipods Differences in Thermal Tolerance and Metabolomic Profiles in a Warming Ocean

Reproduction, particularly lactation, is one of the costliest energetic processes for mammals. During this period, females must allocate energy to offspring growth and development while also sustaining their own metabolic requirements. In an income breeder like roe deer (Capreolus capreolus), particularly during the early hider phase, energy requirements of the mother, and hence foraging and ranging behaviour, increase substantially to support fawn growth. Using biologging data from 90 GPS-collared reproductive female roe deer over a 17-year period, we investigated activity patterns linked to foraging during three key phases of reproduction (late gestation, early lactation, late lactation until weaning) to determine how the energy- and time- budgets were related to reproductive outcomes (number of fawns at weaning). We found that activity peaked during the first month post-parturition with a predicted increase in daily time spent active from 48% pre-parturition to 56% during peak lactation. The number of fawns at weaning explained some of the variation in both timing and intensity of activity: females with one or two fawns were more active overall, particularly during mid-day, compared to those with no fawns at weaning. Females with two fawns had higher activity levels, although not doubled, than those with just one. Our preliminary results therefore suggest that females with two fawns either acquire energy more efficiently, or face a trade-off between maintenance and allocation to fawn growth. Further investigations will elucidate these potential trade-offs, allowing us to better map the relationship between energetic constraints and reproductive outcome in this income breeder.

Linking activity patterns and reproductive outcome in an income breeder

The concept of the "island syndrome" phenomenon has been recognised since the era of Darwin, and it is characterised by the presence of distinct behavioural and morphological traits within island populations that differ from those of the mainland. While most studies have investigated changes that have already occurred, questions regarding the mechanisms and causes of these changes remain unanswered. In this study, we have focused on the founding generation of wild house mice relocated to "islands," a situation analogous to being introduced to novel environments by human transportation. The "islands" utilised in this study are seminatural and comprise distinct dietary regimens. These diets differed in consistency but were comparable in caloric content and mimicked the natural diet of the mice. We then compared mice's behaviour and morphological traits from these "islands" with those of a control population maintained on an artificial pellet diet after seven months. The behavioural stress-coping strategies and foraging behaviours of the subjects were examined, as these are critical for survival during and after environmental change. The analysis revealed no statistically significant differences in stress-coping, however, there were some differences in foraging behaviour. The examination of morphological traits, including body length, tail length, and masticatory muscle strength, revealed a trend suggesting that these traits were beginning to diverge from those of the control population. This outcome is particularly noteworthy given that these were the founder generations that underwent relocations during their early life stages.

The effect of relocation and dietary change on the founder generation of wild house mice

Most non-human primates commonly exhibit exceptional jumping performance, particularly optimized for arboreal leaping. In contrast, humans appear more grounded, and arboreal leaping would represent an extremely risky behavior for them. This contrast raises two key questions: why do non-human primates possess such remarkable jumping abilities, and why did human primates lose this adaptation? In this presentation, we will review the leaping capabilities of primates, including their vertical jumping performance, drawing on various studies, notably those conducted by Prof. Peter Aerts. Using insights from functional morphology, we will explore the anatomical and biomechanical factors underlying the exceptional jumping performance of non-human primates, such as morphotype, lever arms, muscle properties, and muscle power. Finally, we will discuss when and why these capacities may have been reduced or lost in the human lineage, that is, how natural selection ceased to maintain this trait.

Vertical jumping performance in human and non-human primates: an example of relaxed selection?

During reproduction of the Mozambique tilapia (Oreochromis mossambicus), chemical communication mainly relies on urinary steroidal glucuronides (sex pheromones) that dominant males release to prime the final ovulation in pre-ovulatory females and increase reproductive readiness. However, the role of steroids in chemical communication in females has received less attention. Here, we aimed to determine whether 17β-estradiol 3-glucuronate released by pre-ovulatory females functions as a reproductive signal towards males. We investigated the preference of focal males to visual, chemical (female conditioned water), and a combination of both stimuli from pre-ovulatory or post-spawning females, and 10−9  M 17β-estradiol 3-glucuronate. Compared to the control zone, where no stimuli were present, males were more responsive (time spent near the stimuli, digging behaviour, and urination frequency) in the visual and visual + chemical zones than in the chemical-only zone. Males preferred pre-ovulatory to post-spawning female-conditioned water. Interestingly, the time spent by focal males near the source of 17β-estradiol 3-glucuronate was similar to pre-ovulatory conditioned water. However, there was no significant difference in digging and urine pulses in response to 17β-estradiol 3-glucuronate compared to the control group. We suggest that male tilapia recognise the ovulation status of females using visual and chemical cues, and 17β-estradiol 3-glucuronate is part of the pheromone released by pre-ovulatory females to communicate their reproductive status.
This study received Portuguese national funds from FCT - Foundation for Science and Technology through projects UIDB/04326/2020, UIDP/04326/2020 and LA/P/0101/2020.

Behavioural responses to visual and chemical cues in Mozambique tilapia (Oreochromis mossambicus): A putative pheromonal role for 17β-estradiol 3-glucuronate

Ross seals (Ommatophoca rossii) spend most of their year foraging pelagically and only haul out in dense consolidated sea ice for a brief period. The Ross seal is one of the least studied of the Antarctic ice-dependent pinnipeds. Here, we aimed to find out what information we can get from steroid hormones (progesterone, testosterone, and cortisol) measured in hair (males=7, females=14) and serum (males=7, females=13) samples intermittently collected from Ross seals in die Lazarev Sea, Antarctica, between 2016 and 2023. Sex of the animal can be correlated with 85% accuracy using progesterone to testosterone hormone concentrations ratios measured in serum. Sex correlation accuracy in hair samples was lower at 70% using the same progesterone to testosterone hormone concentrations ratios. Thereafter, Ross seal sex could be predicted from samples for two unknown individuals, which turned out to be males. The testosterone and progesterone concentrations in serum and hair were not significantly linked to body length in males and females respectively. Thus, the hormones cannot be used to estimate age of assumed mature Ross seals. Finally, the results suggest that hair likely cannot be used as a historical marker of stress, and reproduction as there was no significant difference in hair glucocorticoid, progesterone, and testosterone hormone concentrations between new and old hair sampled during moult. These are the first ever measurements of steroid hormone, testosterone and progesterone concentrations for one of the rarest Antarctic seal species and aim to serve as a baseline for future research to build on.

What steroid hormones can tell us about Ross seals (Ommatophoca rossii)

Carbon dioxide (CO2 ) is fundamental to biological processes throughout the biosphere. While much is known about the impact of CO2  on the overall physiology of an organism, much less is known about how its interaction with specific biomolecules may affect their function. Identifying proteins that bind CO2  is imperative to understanding these broader CO2 -regulated molecular processes. Carbamylation is a non-enzymatic reversible post-translational modification where CO2  binds to a lysine ε-amino group. A chemical proteomics tool using a triethyloxonium (TEO) ion to trap carbamates allows identification through mass spectrometry. Using this method and 13 C-NMR, ubiquitin has been shown to bind CO2  through the N-terminus and the ε-amino group on lysines 6, 33, 48 and 63. CO2  binding to lysine 48 was demonstrated to reduce ubiquitin conjugation and subsequent activation of the NF-κB pathway. This mechanism is proposed as one method by which elevated CO2  reduces inflammation. Three lysines (11, 27, 29) within ubiquitin do not form observable carbamates. Through computational molecular dynamics simulations, we aim to understand why lysines have different prevalences for carbamate formation and investigate the change in properties and structural impacts of this modification. Understanding how select lysines in ubiquitin do or do not interact with CO2  can influence our broader understanding of protein-CO2  interactions.

Carbamylation impinging on ubiquitination in the NF-κB pathway. 

Empowering students to assist in curriculum co-design fosters ownership and development of employability skills. At a time where student numbers are increasing, and the job market is becoming increasingly competitive, it is crucial that student education places emphasis on the development of skills increasing employability, such as critical thinking, self advocacy, and resilience. Furthermore, rising student numbers and saturated lectures and practical laboratory classes means less resources per student, and risks students becoming disengaged and falling behind in their own development and learning journey. Empowering students to assist in co-curriculum design addresses both of these challenges. Providing the students’ with autonomy and the support required to assist in designing their own honours projects encourages critical thinking and gives students a sense of ownership over their own work and studies, while also developing key skills. Here I will discuss my experiences as a student co-creator on the University of Glasgow project and my perspectives on the curriculum design project

Empowering Students in Curriculum Design: Fostering Ownership, Skill Development, and Career Readiness in the Life Sciences

Stomatal pores on leaves determine water loss of plants and carbon assimilation in photosynthesis. These key physiological processes affect biomass production, stress sensitivity and water use efficiency of plants and are also addressed in breeding. ABA signaling network described for Arabidopsis is conserved in land plants; the module of ABA-activated kinase OST1 leading to anion channel activation and stomatal closure developed during evolution of early land plants. Climate change associated rise in atmospheric vapour pressure deficit (VPD) results in OST1-mediated stomatal closure in Arabidopsis. Here, we measured stomatal VPD- and ABA-sensitivity of barley double mutants defective in two barley genes homologous to Arabidopsis OST1. Double mutants showed higher stomatal conductance and reduced VPD- and ABA-sensitivity compared with wildtype Golden Promise (GP) in gas exchange experiments. Net assimilation rate and stomatal density were only mildly affected in double mutants compared with GP. These results show that as in Arabidopsis, OST1 is involved in determining stomatal openness and sensitivity to ABA and abiotic environmental factors. The effect of alleviating ABA signalling pathaway on stress tolerance and yield is discussed regarding breeding plants for different water availability conditions.

Barley double mutant in Arabidopsis OST1 homologs is impaired in stomatal regulation

An ability to engineer the total chloroplast complement of cells could be transformational, in relation to attempts to engineer photosynthesis, including its alternative metabolic versions.
Detailed analyses of chloroplast biogenesis during leaf development have revealed stages of plastid proliferation, biogenic machinery assembly and eventually greening (synthesis of photosynthetic components). Those analyses have also demonstrated our very limited knowledge of the drivers of chloroplast biogenesis, with currently known ones involved primarily in the greening phase. Particularly well understood are the GOLDEN-LIKE 1 and 2 (GLK1 and GLK2) transcription factors. The total chloroplast content of photosynthetic leaf cells, their chloroplast compartment, is remarkably constant even in plants which carry mutations in chloroplast division genes. glk1,2 double mutants in Arabidopsis are pale, with chloroplasts in similar numbers (to those in the wild type) but smaller, with less developed internal photosynthetic membranes, and creating a smaller chloroplast compartment within the cells harbouring them.
In order to search for novel genetic factors involved early in chloroplast biogenesis, we have carried out genetic screens for loss- and gain-of-function suppressor mutants of the Arabidopsis glk1,2 double mutant.  In at least two of those cases, identification of the responsible gene and isolation of mutants carrying that specific mutation alone has produced plants with an increased degree of greening and an enlarged chloroplast compartment of cells.
These newly-identified genes may open the door to uses in crop plants.

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