Belgium

Pelagic fishes have many adaptations to enable their active lifestyles. Arguably, the rockstars of the pelagic teleosts are the bluefin tunas, as they can attain extremely large body sizes (up to ~700 kg), they can swim at very high speeds, they have large areas of the body served by countercurrent heat exchangers, and they can roam into deep and high-latitude waters that are too cold for other tunas. As such, the cardiovascular and respiratory physiology of bluefin tunas has been assumed to be exceptional compared with other teleosts, although testing this assumption has proved difficult due to the substantial challenges of working with highly pelagic species that spend their lives in open water. This presentation will discuss what is known about the cardiorespiratory physiology of bluefin tunas, with an aim to understand just how awesome these species are in comparison with all the other loser teleosts.

SEB Conference 2025

How awesome is the cardiorespiratory system of the rockstars of pelagic teleosts, the bluefin tunas?

cardiovascular

fish

metabolism

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technical paper

Understanding how sharks respond to catch and release (C&R) recreational fisheries is a key challenge for both management and biologging research. Survival rates and recovery periods are highly species- and setting-dependent, yet no study has been conducted in European recreational fisheries, despite their popularity. We present the first example of electronic tagging to assess C&R effects on blue (Prionace glauca), porbeagle (Lamna nasus) and tope (Galeorhinus galeus) sharks in the UK, for which data are lacking.
Electronic tags (n=69) revealed high (94.7 – 96.2%) survival rates in all three species, with one case of mortality in each. Mortalities could not be definitively attributed to one aspect of the capture event, as animals appeared in good health upon release. However, two individuals (a porbeagle and a tope shark) were deeply hooked and released with hooks in place, which may have caused injuries invisible to observers. Depth time-series (10-minute resolution; n=16) were used to infer when sharks had recovered from angling through changepoint analysis of 4 movement metrics. Recovery time varied among species, but in most cases lasted less than a day. Pre-recovery, abnormal behaviour varied between- and within-species, though typically involved depth-holding either mid-water or near the sea floor and lower vertical velocities. 
The results suggest that when C&R fisheries are conducted within current best-practice guidelines, post release survival can be high. The recovery analysis further offers important insight into the short-term behaviour of electronically tagged animals, which needs to be better accounted for in telemetry studies of marine species.

Survival and post-release behaviour of pelagic sharks caught in recreational catch-and-release fisheries - insights from electronic tagging

Oxygen uptake across the gills has been proposed as a bottleneck in the oxygen transport cascade of pelagic fish with high aerobic requirements. However, most investigations of this topic have relied on intermittent blood sampling, which only provides a snapshot in time of blood oxygenation, so large knowledge gaps remain.
We present a novel method with exciting potential for the study of oxygen uptake limitation in fish. By implanting oxygen sensors into the dorsal aorta of the highly athletic rainbow trout (Oncorhynchus mykiss, n=25), arterial oxygen tension (PaO₂) immediately downstream of the gills could be monitored continuously. We combined this with whole animal respirometry at two distinct water flow regimes within the respirometers (10 and 20 l min⁻¹) and hypothesised that increased flow rates would enhance arterial oxygenation and maximum metabolic rate (MMR) following exhaustive exercise at 20°C. The Pao2  recordings were validated by assessments of dorsal aortic PaO2  and O2  content from intermittent blood samples collected from a separate group of fish.
Intriguingly, PaO₂ closely tracked the minor water oxygen deviations associated with flush and seal cycles during respirometry. Pilot tests exposing the fish to <20% water oxygen saturation confirmed that fish only loosely defend their PaO₂ via hyperventilation and other measures. High water flow did not significantly affect MMR or PaO₂ recovery times, suggesting gill oxygen uptake was not limited following exercise. We highlight research avenues that our new approach has uncovered and discuss how remaining knowledge gaps surrounding gill oxygen uptake dynamics of fish can be addressed.

On-line arterial oxygen tensions provide insight into gill oxygen uptake dynamics in rainbow trout

The global expansion of intensive aquaculture is exposing aquatic animals to increasing environmental pCO2 , but also alkalinity which is artificially elevated to at least partially restore seawater pH. While CO2 -driven ocean acidification research has revealed negative effects on marine invertebrate physiology and growth, the combined effects of high pCO2  and alkalinity are poorly understood. To address this, we exposed economically important king prawns to five aquaculture relevant pCO2  levels for 6 weeks (1,100-20,000 µatm) all pH adjusted to 7.5 by adding NaHCO3  to reflect common aquaculture practices. We fully characterised haemolymph acid-base parameters and ionic composition (inorganic cation/anions, protein and organic osmolytes) in combination with measures of protein homeostasis. These included hemocyanin oxygen affinity (P50 ) as a measure of protein function, and protein ubiquitination and 20S proteasomal activity, both indicators of protein degradation. Initial results show that rising CO2 /alkalinity causes up to 20 % reductions in haemolymph [Na+ ], [K+ ] and [Cl- ] which were associated with a slight linear decrease in hemocyanin P50.  Ongoing work also suggests that protein degradational activity, which is important for body growth and in maintaining a functional proteome, is impaired by high CO2 /alkalinity. Overall, we show that high CO2  and alkalinity in aquaculture severely alters extracellular ionic composition and modifies the function of a key respiratory protein and the regulation of whole-body protein turnover. These findings give insight into how high CO2  impacts protein homeostasis in marine organisms, highlighting a potential mechanism by which adverse environmental conditions impact physiological function and performance in marine organisms.

High CO2 and alkalinity in aquaculture severely impact haemolymph ionic composition and protein homeostasis in king prawns (Penaeus vannamei)

Sea lamprey are anadromous fishes native to the Atlantic coast of North America and Europe. They are considered invasive in the Laurentian Great Lakes, where landlocked populations have contributed to native fisheries' decline. Sea lamprey spend most of their life cycle as filter-feeding larvae before undergoing a complex metamorphosis into a parasitic blood-feeding juvenile, which migrates to sea or in landlocked populations to lakes where they feed on fish hosts (e.g. salmonids). As parasitic juveniles, sea lamprey can consume as much as 30% of their body mass per day in blood, requiring efficient mechanisms to deal with metabolic wastes (ammonia, urea, and acids) from the host blood and those produced through their catabolism of ingested protein. This study investigated the nitrogenous waste and acid-base regulatory capacity of juvenile sea lamprey after three weeks of parasitizing rainbow trout. Further, we focused on the cellular and molecular mechanisms of post-prandial nitrogenous waste handling and acid-base regulation at the gills and throughout the digestive tract. Our results revealed a partially uncompensated respiratory acidosis, increased nitrogenous waste, and base excretion in feeding lamprey. In the intestine, feeding led to acidification of the anterior and mid-intestinal regions and coincided with more pronounced apical/sub-apical H+ -ATPase staining in the enterocytes. These findings reveal key insights into the regulatory capacity that has allowed sea lamprey to contribute to declines in fish populations in the Great Lakes and provide insights into mechanisms utilized by sanguivores to deal with the challenges of blood-feeding.

Mechanisms of nitrogenous waste and acid-base regulation during parasitism by the juvenile sea lamprey, Petromyzon marinus 

Plants, due to their sessile nature, are equipped with intricate molecular mechanisms to respond to environmental stresses including the formation of stress granules (SGs) – membrane-less organelles that sequester translationally repressed mRNAs and proteins during stress. Assembly of SGs are through a phenomenon known as liquid-liquid phase separation (LLPS), mediated by multivalent protein and RNA interactions. Although the predominance of SGs as a survival mechanism has been established, understanding the general composition and its molecular drive remains poorly understood. Our research focuses on unraveling the molecular intricacies of plant SGs, with a particular emphasis on the Oligouridylate binding protein 1c (Ubp1c), a known SG-associated protein. Ubp1c, characterized by its tri-RNA-Recognition Motifs (RRMs), has previously been identified as a key player in SGs formation, yet its precise role and molecular characteristics remain elusive. Using a multi-faceted approach, we explore the contributions of Ubp1c RRM domains to SG dynamics and potential RNA regulation by the protein. Deletion constructs targeting Ubp1c’s RRMs revealed the indispensability for these domains for localization to SG. Our findings further highlight how Ubp1c’s modular domains mediate both RNA binding and LLPs, hypothesizing the facilitation of Ubp1c to recruit specific mRNAs to SGs, thereby influencing SG RNA composition and functionality. Ongoing work aims to characterize RNA and protein composition of SGs in Ubp1c mutants and explore how Ubp1c-mediated RNA sequestration influences mRNA stability and translational control during stress.

Deciphering Ubp1c Function: Phase Separation, RNA Binding, and Its Role in Plant Stress Responses

Abscisic acid (ABA) regulates seed germination and plant responses to abiotic stress, however, its molecular mechanisms of action are still not fully understood. We used an integrative approach, combining transcriptomic, metabolomic, and spatial transcriptomic analyses, to investigate ABA effects on germinating barley (Hordeum vulgare) embryos. Our results showed that ABA primarily acts as a transcriptional repressor, inhibiting carbohydrate metabolism, lignin biosynthesis, cell wall organization, and photosynthesis while activating stress responses and phytohormonal signaling. Metabolomic profiling revealed strong correlations between differentially expressed genes and metabolites related to ABA metabolism and phytohormone pathways, including gibberellins, jasmonates, brassinosteroids, salicylic acid, and auxins. A comparison of transcriptomic profiles between ABA-treated barley embryos and developing seeds revealed that, while ABA regulates a subset of processes common to both stages, most transcriptional changes are unique to the germination phase. This demonstrated that ABA induces a distinct molecular response finely tuned to the regulation of seed germination. Spatial transcriptomics overcame RNA-seq limitations by localizing ABA-regulated gene expression across embryo tissues, revealing significant tissue-specific differences. The results highlight the importance of local regulatory mechanisms during germination. Integration of obtained datasets uncovered a ‘molecular signature’ of ABA effects in germinating embryos, offering new insights into its role in barley seed germination. These findings have potential implications for breeding strategies to enhance germination efficiency and crop resilience under environmental stress.
This work was supported by the National Science Center, Poland project SONATA BIS10 ‘(QUEST) Quest for climate-smart barley–the multilayered genomic study of CBC function in ABA signaling’ (2020/38/E/NZ9/00346).

Unraveling ABA's Molecular Signature: Insights into Its Function in Barley Seed Germination

This poster outlines the design and implementation of Engineering Bacteriophage Laboratory, an inquiry-based lab course for freshmen and sophomores. The course aims to teach students to think like scientists and motivate STEM-oriented students by fostering hands-on, engaging learning experiences. Developed in collaboration with institutional partners, including a faculty research lab and the molecular visualization facility, the course integrates cutting-edge technologies such as VR protein structure visualization to enhance student engagement. This innovative approach connects students to real-world applications, supporting both their learning and success in the biochemistry field.

Inquiry-Based Introductory Biochemistry Laboratory Course

The model systemSilene vulgarisand its relatives from theBehenanthasection provide a unique opportunity to explore the relationship between gynodioecy and mitochondrial (mt) genome structure. Complete mt genome sequences from severalS. vulgarispopulations revealed the highest intraspecific mt genome diversity reported in any angiosperm, characterized by extensive intergenic regions, hundreds of repeats, and multiple subgenomes.
The taxonomic diversity withinBehenanthaoffers an ideal framework for studying the origins and evolution of this extraordinary mt genome variation. This section includes both gynodioecious and hermaphroditic species, such asSilene fabaria, which is closely related toS. vulgarisyet exhibits a profoundly different mitogenome. While similar in size,S. fabariamt genome forms a single circular molecule with only a few large repeats, in contrast to the multipartite structure ofS. vulgaris.
The high mt genome diversity and frequent intramolecular rearrangements also impact essential mt genes. Some genes display variable transcription start sites or lack stop codons in certainS. vulgarisgenotypes. Hundreds of nucleus-encoded proteins regulating organellar gene expression must adapt to this intraspecific mt genome variability in gynodioecious species. The recently publishedS. vulgarisnuclear genome now enables the analysis of neo/subfunctionalization in organellar RNA-binding proteins, particularly pentatricopeptide repeat (PPR) proteins, which are associated with extreme mt genome variation.

The Relationship Between the Reproductive System and Mitochondrial Genome Structure in the Gynodioecious SpeciesSilene vulgarisand Its Relatives

Spectral light quality can regulate both the physiology and development of stomata. The combination of red and blue light promotes stomatal development through phytochrome and cryptochrome responses. In dynamic light responses, red light indirectly regulates stomatal opening by stimulating chloroplasts, while blue light rapidly triggers stomatal opening via phototropin-mediated signal transduction. However, the net effects of these responses on stomatal dynamics, whether through stomatal physiological responses or leaf structural development, has not been well distinguished. In a controlled-environment growth chamber experiment, six treatments with different R:B ratios ranging from 0.45 to 2.06 were combined with a fixed photon flux to study the changes in stomata conductance and anatomical properties during flowering in tomato (Solanum lycopersicum). The results showed that as the R:B ratio increased, the time required to complete stomatal opening and closing both became shorter. Correspondingly, the maximum stomatal conductance decreased with increasing R:B ratio. When the R:B ratio was at the minimum of 0.45, stomatal conductance reach the largest value under saturating light. Anatomical results showed that lower R;B ratio makes stomatal conductance at steady state a larger proportion of the maximum determined by anatomy. The R:B ratio had a significant effect on the linear relationship between anatomical potential stomatal conductance and actual diffusive conductance. The experiment demonstrates that stomatal responses are modulated by adjusting the R:B ratio of light in controlled environments, with a larger proportion of blue light promoting wider stomatal opening via physiological mechanisms, and minimal contribution from anatomical changes.

Effects of red and blue light proportions on stomatal dynamics: distinguishing the roles of physiology and development

• The stomatal red light response changes stomatal conductance (gs) proportionally to photosynthesis, is partly driven by the chloroplast plastoquinone redox state (1-qL) and can be manipulated to change water-use-efficiency. It consists of leaf internal [CO2] (Ci) dependent and independent contributions. Ci-independent response in Arabidopsis thaliana is suggested to be larger than the Ci- dependent response for physiological Ci, but it is unclear to what extent environmental acclimation could change this ratio.   • We tested how Ci-independent responses changed under two different light acclimation states in Arabidopsis plants with intrinsically different levels of 1-qL by different content of Photosystem II Subunit S (PsbS) with red light response curves of gs.   • Acclimation to higher light intensity reduced 1-qL levels at the higher red light intensities for Col-0 but not for the mutants and the acclimation induced reduction of 1-qL did not affect the slope of 1-qL versus gs at the same Ci,. gs of Col-0 was however increased, indicating that the Ci- independent response remained the same and the Ci- dependent red light response increased with acclimation to higher light intensity.   • The ratio of the Ci dependent and Ci-independent responses to red light can acclimate to the needs of the plant through homeostasis.

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