Czechia

To cope with environmental challenges due to global change, organisms must modulate their physiology to survive. Various environmental stressors like heat and pollution have been suggested to cause increased oxidative stress in animals. However, in many organisms with multiple life-stages, like the Calanoid copepods, how different life-stages respond to environmental stressors remains unclear. The planktonic marine copepod Calanus finmarchicus is a low trophic species, an important food source to several commercially important fish, and a keystone species in the ocean. Therefore, it is important to understand how they respond to stress. To investigate the physiological and life-history effects of critical life-stages of C. finmarchicus to heat stress and oxidative stress, we exposed fertilised eggs and adult males and females to graded doses of paraquat, an oxidative stress inducer, at different temperatures. We measured the eggs’ hatching rate, defined the 96 hours LC50 of paraquat, and examined antioxidant mechanisms by measuring the transcription level of biomarkers genes involved in oxidative damage such as superoxide dismutase in both eggs and adults in response to both heat stress and paraquat treatments. Preliminary results showed no additive nor synergistic effects of heat and oxidative stress on the metabolic response of adult females. We hypothesised that early life stages and adult males are more sensitive to oxidative stress and temperature change than adult females. A better understanding of how copepods respond to environmental changes and the physiological mechanisms underpinning these responses will help us predict marine ecosystem dynamics in relation to global change.

SEB Conference 2024

Effects of environmental challenges on physiological and life-history performance of a small marine copepod, Calanus finmarchicus.

calanus

heat

oxidative stress

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technical paper

Organisms exhibit reversible physiological adjustments as a response to rapidly changing environments. Yet such plasticity of the phenotype is gradual and may lag behind environmental fluctuations, thereby affecting long‐term average performance of the organisms. By supplying energy and essential compounds for optimal tissue building, food determines the range of possible phenotypic changes and potentially the rate at which they occur. Here, we assess how differences in the dietary supply of essential lipids modulate the phenotypic plasticity of an ectotherm facing thermal fluctuations. We use three phytoplankton strains to create a gradient of polyunsaturated fatty acid and sterol supply for Daphnia magna under constant and fluctuating temperatures. We used three different fluctuation periodicities to unravel the temporal dynamics of gradual plasticity and its long‐term consequences for D. magna performance measured as juvenile somatic growth rate. In agreement with gradual plasticity theory, we show that in D. magna, fluctuation periodicity determines the differential between observed growth rates and those expected from constant conditions. Most importantly, we show that diet modulates both the size and the direction of the growth rate differential. Overall, we demonstrate that the nutritional context is essential for predicting ectotherm consumers' performance in fluctuating thermal environments.

Food quality shapes ectotherm gradual phenotypic plasticity

Equids can be distinguished from every other extant mammal by their monodactyl feet. Classically, equid evolution is portrayed as a linear, gradual evolution from tetradactyly to monodactyly, culminating in the modern monodactyl genus Equus (including the domestic horse). Although the linearity of this locomotor transition has now been reassessed in favour of a more complex evolutionary history, the musculoskeletal and physiological similarity of modern equid limbs remains unexplored. Are domestic horse limbs representative for wild equids (e.g., zebras, onagers, etc.), or are there substantial differences in their muscle architecture or myological arrangement which might affect efforts to biomechanically model the musculoskeletal system of extinct species? Here, we explore this question by quantitatively describing the forelimb muscle architecture of all extant Equus species. Gross dissections were performed to record origin and insertions sites, and quantitative metrics recorded (muscle-tendon unit (MTU) length, MTU mass, muscle mass, pennation angle, and fascicle length). Muscle physiological cross-sectional area (PCSA) and ligament (and tendon) anatomical cross-sectional area (ACSA) were then calculated. Results confirm attachment sites of all muscles are homologous across all species, with little individual variation. When normalised for size, the forelimb muscles of caballines, zebras, and wild asses exhibit comparable muscular architecture and force-generating capacities. Although limited by sample size, these results indicate that scaled data for modern equids (domestic and wild) are very comparable, which will facilitate much smoother translation of experimental data from domestic horses into digital simulation of (at least the later stages of) the equid locomotor transition.

Could 'wild horses' drag you away? Comparing muscular architecture in the forelimbs of extant equids (Perissodactyla: Equidae).

Many water systems suffer from reduced or completely disrupted connectivity due to human activities, causing negative effects for species and ecosystems. Artificial transport past migration barriers, so called trap-and-transport, can be used as a management tool to mitigate fish population declines. The efficiency of trap-and-transport is, however, rarely evaluated, in particular for downstream transport of catadromous species such as the European eel. In this study we analysed seven years of trap and transport data (2016-2022), encompassing more than 65 000 transported eels, to evaluate stress and mortality during all steps of the trap and transport process. We found that average mortality rate was generally low but could be as high as 10%. Mortality during all steps of the trap and transport procedure was affected by temperature, with higher temperatures leading to higher mortality. We also found that when mortality in the fishing gear had been high, mortality during holding was also high. Mortality during transport was additionally affected by transport time, with longer transport time causing higher mortality. In addition to mortality rates, we also evaluated stress during trap and transport by surgically implanting biologgers measuring heart rate, which was used as a proxy for stress. Similar to mortality, stress was affected by temperature, with higher temperatures causing higher stress levels, in particular during transport. We conclude that although trap-and-transport, fishways, and other alternatives aiming at reducing negative impacts can reduce mortality, such measures require maintenance and human interference, wherefore removal of migration barriers should be the long-term goal.

Evaluating stress and mortality during trap and transport in the European eel

The project aimed to investigate the influence of geography,
evolutionary history, and host genetics on the skin microbiome diversity
of the moor frog (Rana arvalis), a widespread amphibian species. By
examining 12 populations from two geographical clusters, we explored
the association between bacterial diversity and composition and the
major histocompatibility complex class II exon 2 diversity. Results
revealed significant variations in MHC alleles/supertypes and genetic
diversity based on geography and evolutionary history. While bacterial
alpha diversity remained consistent across clusters, it correlated
positively with expected MHC heterozygosity and negatively with
MHC nucleotide diversity. Moreover, bacterial community composition
exhibited significant differences between clusters and specific MHC
alleles/supertypes. These findings underscore the impact of historical
demographic events on hologenomic variation and provide insights
into how immunogenetic host variability and microbial diversity may
collectively influence host fitness and disease susceptibility, ultimately
affecting population persistence.

Association between the skin microbiome and MHC class II diversity in an amphibian

The host gut microbiome functions in digestion and immune defense, but additionally influences cognitive behavior. Habitat and diet are strong influencers in shaping the gut microbiome. However, among closely related species, phylogenetic relatedness is a strong predictor of gut microbiome community composition. Although phylogeny is a strong predictor, the impact hybridization has on the gut microbiome is poorly known. To explore this, we sampled feces from nestlings across a hybrid zone transect for black-capped (Poecile atricapillus) and Carolina chickadees (Poecile carolinensis) during the 2021 and 2022 breeding seasons. These nestlings were brought back to the Lehigh University Animal Facility and raised to adulthood under common conditions for cognitive testing. Fecal samples were taken at multiple time points and used to characterize the gut microbiome community composition. To do this, we extracted microbial DNA and sequenced the V3-V4 region of the 16S rRNA gene. Using amplicon sequence variants (ASVs), we compared the abundance and diversity of bacterial taxa across ancestry groups and at different time points after experiencing common conditions. Being raised under common conditions led to a decreased alpha diversity for parental species, but not for hybrids. After standardizing environmental conditions, differences between ancestry groups in abundance of specific gut phyla and specific ASVs suggests that genetic variation also plays a significant role in gut microbial composition. Alpha diversity and abundance of individual ASVs seemed to correlate with cognitive performance as well. Assessing the factors that influence gut microbiome diversity in two closely related sister species and their hybrids helps us to better understand the various factors that shape host-microbiome communities.

Microbiome Diversity and Cognition in Hybridizing Chickadees

Differences in growth rate and metabolism between individuals can determine competitive social dynamics as well as survival during vulnerable life stages. While this inter-individual variability has received growing attention, variability within individuals can also be substantial but has rarely been studied. Here, we used the ecologically and culturally important estuarine fish Galaxias maculatus to understand inter- and intra-individual variability in metabolism and determine their relative contributions to growth.

Specifically, we collected repeated measurements of metabolic and growth performance across 6 months to gauge inter- and intra-individual variability in both metrics for a wild-caught population of 160 G. maculatus. Groups of fish were fed to satiation and housed in tanks where each fish had a unique colored subcutaneous elastomer tag. Fish were initially measured for active, routine, and standard metabolic rates at 18℃ before being randomly assigned to an acclimation group at either 18℃ (benign summer temperature) or 23℃ (challenging summer temperature). We tracked each individual’s growth and collected a further five metabolic measurements per fish (~1 per month). 

Our results showed negligible correlation between specific growth rate and both standard and routine metabolic rates. Inter- and intra-individual variability were similar for both standard and routine metabolic rates (mass-standardized), including between temperature treatments. These findings provide some of the strongest evidence that the metabolic phenotype of an individual can change across time, matching the extent of the variability within a population. 


Intra- and inter-individual variability in metabolism drives growth performance of a temperate estuarine fish

Variation in animal behaviour has recently gained traction in understanding variation within physiological traits. Integrating animal behaviour may be particularly important for measuring metabolism as oxygen demand is sensitive to the behavioural state of the individual. For example, a fish exposed to a novel environment may exhibit individual differences in metabolic oxygen demand as a consequence of behavioural responses, such as activity and exploration related to anxiety in an unfamiliar context. On this background, we sought to explore variation in routine metabolism (RMR) as a consequence of novelty to the testing chamber and substrate color – with black representing a low anxiety state and white a high anxiety state – using a repeated measures experimental design to track differences in individual traits across treatments. Finally, as shoaling is thought to reduce predation risk and therefore may influence stress-related responses, we tested a subset of individuals in a third iteration of respirometry with a size-matched conspecific. Contrary to our predictions, we found no difference in RMR with black vs. white substrate; whereas, RMR was significantly higher during the second iteration of respirometry, independent of substrate color. Interestingly, the total oxygen consumption in our paired fish tests was not significantly different from the mean RMR in the initial run, potentially indicating a mollifying social effect. Behavioural data suggests differences in activity/exploration that complement metabolic patterns. Our data indicates individual variation in behaviour, especially in response to novelty, and its impacts on the stability of metabolic measurements.

Patterns of individual variation in metabolism and behavioural responses in the sheepshead minnow (Cyprinodon variegatus)

AI provides a fast and efficient way to generate textual outputs, produce images, analyse core learning, and evaluate biological data. This is driving a transformation in education, with consideration needed around current assessment practices as tools such as ChatGPT become more prevalent. In this talk, we will explore some of the pedagogic approaches and assessment strategies that have been successfully developed that allow for the incorporation of AI into the assessment. When used correctly, and ethically, AI can be a valuable learning aid for students and an effective facilitative tool for educators.

Generative AI: the power and the peril in Biosciences education

Characterization of differences in N assimilation and deficiency responses in C3 and C4 Cleome species
The evolution of C4 photosynthesis led to increased carbon assimilation rates and plant growth. In contrast to C3 plants, which use Rubisco for primary CO2 fixation in all photosynthetic cell types, in C4 plants carbon is initially fixed in mesophyll cells (MCs) by PEP carboxylase (PEPC). Subsequent decarboxylation of the resulting C4 acid takes place in the bundle sheath cells (BSCs). This increases the local CO2 concentration around Rubisco, which minimizes its oxygenation reaction reducing photorespiration and thereby improving photosynthetic efficiency. Similarly, in most C4 plants the reduction of nitrate and nitrite is restricted to MCs, while the further assimilation of reduced nitrogen into the amino acids glutamate and glutamine mainly takes place in the BSCs. Changes in the expression pattern of glycine decarboxylase (GDC) lead to the restriction of photorespiration and therefore serine production to BSCs. Balancing of metabolic routes is therefore necessary to maintain homeostasis of not only carbon but also nitrogen (N) metabolism. These differences in N requirements of the two photosynthetic mechanisms pose the question of how N assimilation pathways differ between C3 and C4 species and whether these changes are a consequence or prerequisite of C4 evolution. Characterization of mineral nutrition traits revealed clear differences in the N metabolism of C3 and C4 Cleome species under N deficiency conditions, indicating a higher N deficiency tolerance in the C4 species. The addition of NH4+ was shown to offset the reduction of biomass and photosynthetic efficiency in the C3 but not the C4 Cleome species.


Characterization of differences in N assimilation and deficiency responses in C3 and C4Cleome species

Cowpea (Vigna unguiculata) is an essential crop providing a substantial source of protein and ensuring food security for Sub-Saharan Africa. However, with the unpredictable fluctuations of temperature caused by climate change, heat waves are becoming more frequent threatening cowpea yields. Rubisco, the central protein for carbon assimilation is thermostable, however its chaperone Rubisco activase (Rca) is temperature sensitive. Cowpea has four Rca isoforms: 1β, 8α, 10α and 10β. In this study we investigated the effect of a heat wave on Rca isoform levels in cowpea monitoring in parallel changes in growth traits and Rubisco activity. Cowpea plants cultivar IT97K-499-35 were grown at 28/18oC day/night for 14 days and then exposed to a 5-day heat wave at 38/28oC day/night. The heat wave caused changes in leaf shape, a decrease in Rubisco activity, changes in overall gene expression as well as in the relative levels of the different Rca isoforms. In vitro characterisation of the temperature response of the cowpea Rca isoforms showed differences in temperature optima for activity that could be exploited to enhance the thermal tolerance of cowpea.

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