Czechia

Until recently, the role of mitochondria in migration physiology and energetics has been mostly unstudied. The migratory phenotype consists of whole-organism to subcellular adaptations although a paucity of information exists on how organelles within the cell may play a critical role. Our research has focused on two-study comparisons of closely related migrants and non-migrants, in the family Mimidae and genus Zonotrichia. Here, we discuss our mitochondrial respiratory performance results between our study groups by measuring mitochondrial respiration using High-resolution respirometry. Additionally, we discuss other important variables and measurements that were collected that allow us to examine oxygen carrying capacity, fuel usage, and whole-organism performance. Our initial study on migratory and non-migratory, White-crowned Sparrows (Zonotrichia leucophyrs), demonstrated evidence of seasonal upregulation of mitochondrial performance related to migration. However, our Mimidae results did not. We discuss potential explanations for these patterns and how we are currently working to understand the mechanisms underlying our results. Lastly, we discuss our current work on expanding to other Zonotrichia groups to control for relatedness in our study.

SEB Conference Prague 2024

Measuring mitochondrial respiratory performance in closely related migrant and non-migrant avian species

flexibility

bioenergetics

mitochondria

migration

technical paper

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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.

Biotic interaction with complex communities of microbiota inhabiting every mucosal surface of teleost fish strongly influence the host metabolism, growth and health. The gill mucosal surface constitutes a special habitat for host-associated microbes due to its unique functions in waste excretion, gas exchange and local immune activity. The gill associated lymphoid tissue (GIALT) enables fish to discriminate between beneficial and pathogenic bacteria keeping microbiome homeostasis. Changes in the environment however, including water conditions, seasonal changes and physiological stress can lead to compositional disturbances that turn commensals into pathogens. This sensitivity to environmental parameters provides the opportunity to use the microbiome composition of the external mucus as a biomarker for the health of the fish. 
Here we compare the microbial gill mucus communities of the two teleost species Osmerus eperlanus and Gymnocephalus cernua from different life-history guilds and the bacterioplankton in the Elbe estuary. Over the course of one year, we collected 220 fish along the main channel of the estuary and generated matching 16S rRNA metabarcoding and host transcriptome libraries. The aim is to characterize the physiological response along spatio-temporal gradients, extract bacterial indicator species and determine driving factors for fish health.


Wild fish holobiont response to abiotic gradients in the Elbe estuary

The frequency of hypoxic events (i.e. decrease of dissolved oxygen level in water) is increasing at an unprecedented rate due to anthropogenic pollution and climate change. As species might not be able to adapt fast enough to this rapid change, they would need to rely on faster phenotypic responses such as plasticity. If the stressor becomes persistent, some transgenerational plasticity could occur. Physiologically the low oxygen environment can impact the organism's metabolism, potentially affecting their fitness. Therefore, more studies are needed to decipher fish metabolisms plasticity to hypoxia within and across generations. To investigate this, we did a multigenerational experiment with a wild population of Gasterosteus aculeatus. The first generation (F1) was either exposed to normoxia (100% dissolved oxygen, DO), or daily fluctuating hypoxia (30% DO at night and 100% DO during the day) mimicking the oxygen fluctuation happening in the wild. Their offspring (F2) were reared either matching their parental condition or not, resulting in four different groups reflecting within- or trans-generational plasticity. We assessed their aerobic metabolism (aerobic scope) and oxygen transport capacity (maximal heart rate frequency, blood hematocrit, and hemoglobin content) as well as the anaerobic metabolism (hypoxia tolerance and Pcrit). The results only showed within plasticity to fluctuating hypoxia with an increased hypoxia tolerance of the fish and decreased Pcrit, while the aerobic metabolism and oxygen transport capacity did not change. This study shows that fish might cope with this level of hypoxia through within-generation plasticity while transgenerational plasticity is not yet observed in measured traits.

Gasping for oxygen: The  cross-generational plasticity of  metabolism in Gasterosteus aculeatus exposed to fluctuating hypoxia

While hypoxia (i.e. low dissolved oxygen level in water) events occur naturally, global change and human activities have exacerbated their strength and temporal fluctuations. As populations may not be able to escape the hypoxic conditions, it is crucial to understand how organisms can adjust and adapt to these fluctuating environments across generations. When directly exposed, individuals may be able to adjust their phenotypes through plasticity to maintain their fitness. With continued exposure to hypoxia over generations, adaptive transgenerational plasticity can take place to help the offspring to survive the new conditions. Even longer exposure could also lead to the evolution of the population. However, so far, little is known on how plastic response to hypoxia could actually pave the way for future evolution. Using two populations of three-spined sticklebacks (Gasterosteus aculeatus) collected from streams already experiencing and potentially adapted to strong hypoxic events or not, we exposed the offspring to experimental hypoxia (30% air saturation during the night and 100% during the day) over three generations, resulting in several groups reflecting within-, inter-, and trans-generational plasticity, as well as adaptation. We then measured their growth, metabolism, and behaviour and highlighted that the plastic responses observed were not necessarily in line to the potential adaptation. While the directions of the responses were different, we cannot exclude that the fish plasticity might still be a strategy to cope with the environment until genetic adaptation occur.

Fish cross-generational response to hypoxia: can plasticity pave the way to evolution?

This study aims to bridge the gap between the physiological response of Polar cod, Boreogadus saida, to ocean acidification and global warming, and the underlying molecular mechanisms. In this comprehensive project, a variety of physiological parameters (e.g.: growth and exercise) were investigated in response to ocean warming and acidification. The fish were long-term acclimated to three different CO2 concentrations: 390 ppm, a moderate increase (780 ppm), and high PCO2 levels corresponding to the business-as-usual greenhouse gas emission scenario (RCP8.5, 1170 ppm). Each CO2 treatment was combined with four temperatures, 0, 3, 6, 8°C to simulate different warming scenarios. In this study, we focused on the transcriptomic profiles from liver of these incubated and physiologically tested fish to identify critical molecular mechanisms underlying the previous reported physiological responses. Generally, we did not detect signs of a classical stress response, even at the highest temperature after four months of exposure. Consistent with previous observations, the molecular responses to ocean acidification were minor compared to temperature, but an interaction between both factors existed at least for some metabolic processes. Gene ontology analysis revealed a strong response in lipid-, carbohydrate- and protein metabolism. With increasing temperature, we observed a shift away from lipid metabolism, while carbohydrate metabolic pathways remained stable. Although we found Polar cod to be highly resilient to ocean acidification, temperature will remain a critical parameter for this valuable Arctic keystone species and the question remains whether adaptation mechanisms can be implemented in its natural habitat, especially when food supply is limited.

Transcriptomic response of Polar cod, Boreogadus saida, to ocean acidification and warming

Understanding predator-prey interactions is crucial in ecological research, with timing and kinematics of escape responses greatly affecting animal survival to predator attacks. However, little is known about the escape responses of elasmobranchs, or chondrichthyans. In this study, we investigated the escape responses in the spotted ratfish (Hydrolagus colliei), a smaller chondrichthyan predator found in the Puget Sound, to compare its ability to perform fast-start escape behaviour against other chondrichthyan species that inhabit the same region.  Previous work has found that adult ratfish possess Mauthner cells (M-cells), a key neural element associated with fast reactions in the escape responses of teleost fish and larval amphibians, though not known to be present in other adult chondrichthyans. Escape responses were elicited using mechanical stimuli for nine individuals, and videos were analysed to quantify response latencies, and turning angles and rates. Results indicated that ratfish do perform fast-start escape responses, with variations in response characteristics across individuals. The ratfish had a shorter minimum latency (36ms) when compared to the spiny dogfish (Squalus suckleyi) (66.7ms), an elasmobranch found in the Puget Sound that does not have M-cells. These findings contribute to our understanding of predator-prey dynamics in chondrichthyan species.

Escape response timing and kinematics in a deep-water chondrichthyan, the spotted ratfish, Hydrolagus colliei

Chill sensitive insects risk neuromuscular dysfunction in cold environments due to a mismatch between active and passive membrane ion transport. This is particularly critical for muscle cells function where hypothermic loss of Na+/K+-ATPase activity may cause depolarization due to loss of ion balance and decreased electrogenic polarization. To investigate this further we examined 10 Drosophila species with varying cold tolerances to quantify if chill-tolerant species defend membrane polarization better at low temperature through enhanced Na+-K+-ATPase activity. Muscle membrane potential measurements was measured in all species at 21°C and 0°C, with and without ouabain (a Na^+-K^+-ATPase blocker) . At benign temperature all species had similar muscle membrane potential of ~ -55 mV and in accordance with our hypothesis cold sensitive species exhibited a larger hypothermic depolarization. Further, measurements of membrane potential with ouabain showed that the cold induced depolarization in sensitive species was predominantly caused by a loss a Na+/K+ mediated electrogenic polarization. Subsequent measurements of whole animal standard metabolic rate at high and low temperature showed that the improved preservation of membrane in cold tolerant species came at a low cost as the more cold tolerant species were characterized by a lower mass specific metabolic rate despite the potential costs of maintained ion pumping in these cod adapted species.

Keep on pumping: Cold tolerant Drosophila resist hypothermic depolarization of muscle membrane potential

Repeated hypoxic events are reported in various brain pathologies. Mammal brain is highly vulnerable to hypoxia, because brain functions require high oxygen and energy demands. Marine mammals, such as pinnipeds, were naturally selected to cope with daily repeated hypoxic events during foraging dives, when human brain can only cope with minor repeated hypoxia. How do pinnipeds cope with repeated severe hypoxic events at the blood-brain interface? We performed a comparative physiological approach using for model the Southern Elephant Seal (SES), which is the most extreme diver of all seals and being exposed to severe peripheral hypoxia.
Immunolabelling of various blood-brain interface markers (endothelium, astrocytes, neurons) were performed on brain cortical slices from freshly dead post-weaning pups (n=4) and reproductive adults (n=5) collected at Kerguelen Island. Immunolabelling were visualised using confocal microscope and images were analysed using ImageJ. 
Cerebral vascularisation exhibits significant differences between pups and adults: 1) in the grey matter, the vascular volume fraction was around 62% higher in adults than in pups; 2) the vessels were significantly more ramified and tortuous in adults (e.g. 6% more tortuous in the white matter); 3) some large blood vessels exhibited abnormalities in adults suggesting blood-brain interface dysfunctions. Interestingly, adult SES vessels share similar phenotypes to pathological cerebral-blood vessels described in human neurodegenerative diseases. Then, abnormal vessel-morphologies raise the question of the potential pathological situation for adult SES. To study blood-flow velocity in brain-vessels and premature aging in SES, biomechanical fluid modelling, additional staining for neurodegenerative landmarks and blood-biomarkers are currently performed.

Does cerebral blood vessel phenotype represent and adaptative response to repeated hypoxia in the southern elephant seal?

Excellent research requires excellent leadership, but the goalposts for leadership excellence in life sciences are moving. Everyone regardless of seniority has leadership responsibility, and creating an accessible, inclusive, and responsive biology research environment that accurately reflects member's needs is vital for success across the sector. Despite this, it can be challenging to ensure everyone receives appropriate accommodations based on their needs. This co-created project uncovers the core tenets of inclusive leadership in biology, underlines the importance of intersectionality, and encourages participants to look beyond their own experiences and expectations of leadership. This talk explores the Inclusive Leadership Resource, shares pilot data from our self-scoring system, and highlights the importance of co-creation processes when modelling culture change in research environments. Ultimately, talk aims to equip participants with confidence, creativity, and deeper understanding when approaching intersectionality and accommodations in biological research environments.

Integrating Intersectionality: A New Lens on Leadership in Experimental Biology

The consequences of climate change, such as soil salinization and droughts, are some of the main threats to agricultural production, environmental health, and economic welfare. Plant growth-promoting bacteria (PGPB) represent one nature-based solution to favour plant yield and growth in a changing environment. In our study, we explore the potentiality of Technosols to provide PGPBs with peculiar properties, including the capability to recover salt-affected soils and test the potentiality of Technosol-isolated PGPBs to enhance plant growth under saline conditions. For this purpose, selected Technosol-isolated PGPBs were mixed to produce two consortia, one of which was combined with an allochthonous halotolerant bacterium. Lettuce seeds were primed utilizing the two consortia and the saline bacterium alone. The experimental setup consisted of two steps. In the first one, seeds were primed with PGPBs and incubated on water agar media at different NaCl concentrations; in the second, seeds were incubated in not- and sterilized Technosol at different NaCl concentrations. Germination tests and biochemical analyses were performed to assess the potential benefits of PGPB symbiosis on plant growth performance. The water agar salinity test indicated an inhibitory effect of PGPBs on germination, while the use of saline-bacterium showed a positive response on seeds. Our study suggests that urban Technosols may provide PGPBs, whose features may be modified by allochthonous bacteria addition opening new perspectives in urban greening replacement, recovery of degraded environments, and urban soil microbiome ecology understanding.

Testing the potentiality of Technosol-isolated PGPB to enhance plant growth under saline conditions

Strigolactones (SLs) are a plant hormone known for inhibiting branching/tillering. Moreover, Plants release SLs into the soil to attract symbiotic mycorrhizal fungi. However, released SLs are also perceived as germination signal by seeds of root parasitic plants, such as Striga hermonthica. Structurally, natural SLs are diverse and divided into canonical and non-canonical SLs. One of the most intriguing questions in SL biology is whether all SLs fulfill the same functions as hormones in planta and simultaneously as rhizospheric signals. To address this question, we generated rice mutants lacking canonical SLs and showed that they do not exhibit the phenotypes characteristic for SL-deficient mutants, i.e. high-tillering and dwarfism. However, these mutants release exudates with a significantly reduced Striga seed-germinating activity, indicating a particular function of canonical SLs as rhizospheric signals. Furthermore, generating of rice mutants that accumulates 4-deoxyorobanchol revealed a particular function of this canonical SL as a negative regulator of shoot and panicle growth and a promoter of root growth. Taken together, our work inarguably identifies particular functions of different SL classes, opening up the possibility of targeted design of plant architecture and modulating rhizospheric communications.

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Wild fish holobiont response to abiotic gradients in the Elbe estuary

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