Czechia

Climate change is causing rapid warming of Arctic regions threatening the ecosystem and their species such as the polar cod (Boreogadus saida). Polar cod is considered the most abundant forage fish species linking lower and higher trophic levels in the Arctic food web. In particular, the thermal tolerance of sensitive life stages, such as reproducing adults, is important for an assessment of biodiversity changes in the context of global warming. Here, a non-invasive experimental approach using magnetic resonance imaging (MRI) is presented to investigate the physiological performance of reproducing male, female and non-reproducing polar cod during acute warming. Inside the MRI scanner, 0°C pre-acclimated polar cod were exposed to a temperature ramp from 0°C to 8.5°C at a rate of 1.5 °C every two hours. A set of physiological performance parameters of the cardio-vascular system and energy status were continuously determined during the temperature ramp. In particular, flow-weighted MRI techniques were used to quantify blood flow in the head and in the abdomen, respectively, and the ventilation rate was assessed using CINE MRI. The energy status was determined by in vivo 31P-NMR spectroscopy. A preliminary data analysis showed a similar blood flow at the control temperature of 0°C for all three animal groups, whereas blood flow increased remarkably in the head of reproducing males during warming, which was more pronounced in comparison to non-reproducing individuals. These initial results could indicate a higher energy requirement of the reproducing males, leading to a higher sensitivity to future warming conditions.

SEB Conference Prague 2024

Physiological response to acute warming of reproducing male and female polar cod (Boreogadus saida) using MRI

non-invasive

magnetic resonance imaging (mri)

polar cod

cardiovascular system

technical paper

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Crucian carp (Carassius carassius) overwinter in ice-covered lakes and can survive anoxia for several months at low temperatures. The physiological adaptations allowing this survival are well understood at the whole-organism level, but we know less about the molecular machinery coordinating this adaptation to anoxia and reoxygenation and the possible involvement of epigenetic mechanisms. Due to the profound impact of DNA methylation on regulating gene expression, by directly influencing the accessibility of transcription factors and other regulatory proteins to the DNA, it acts as a switch mechanism and makes investigating it particularly interesting. Past RNA sequencing experiments to analyze the whole brain transcriptome have revealed that many genes are expressed differently in response to anoxia. We suspect that some of these changes in gene transcription during anoxia may be influenced by DNA methylation. Utilizing the next-generation Whole Genome Bisulfite Sequencing (WGBS) method combined with RNA sequencing, we investigated the altered gene activity-environment interaction, providing comprehensive, high-resolution, and quantitative methylation data. Our goal was to determine if genes that are differentially regulated during anoxic conditions are under epigenetic regulation by identifying a correlation between the DNA methylation loci on cytosines and differential RNA expression on the transcriptional level during and after anoxia exposure in the brain. The obtained data elucidates the role of DNA methylation in regulating the response to anoxia and guides us toward uncovering potentially novel molecular players in anoxia tolerance.

DNA methylation alterations during anoxia and re-oxygenation in crucian carp brain

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.

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

The ability of marine species to rapidly adapt to multiple environmental changes is considered to be a fundamental mechanism in enabling them to survive global changes. Therefore, considerable efforts have been undertaken to test the evolutionary potential of multiple species when exposed to global change stressors. However, they mostly focused on single stressors exposure. As stressors can interact in non-linear manners, it is essential to better understand the mechanisms and the molecular signature of this adaptation in a multistressor context. Whilst genetic advances have greatly contributed to pinpointing some of the genetic mechanisms involved, a functional disconnect between genes and fitness remains: little is known about the actual changes occurring at the cellular level outside the nucleus following rapid adaptation. Therefore, building on the previous multigenerational selection experiment that looked at the fitness-related traits and genomic responses to ocean warming (OW) and ocean acidification (OA) in the marine copepod Acartia tonsa, we compared the metabolomics and lipidomics profiles of the F>100 lineages following their respective adaptation to OW and OA in isolation and in combination (OWA). Four pools of 200 individuals per lineage were flash frozen and metabolites and lipids were extracted and injected into a high-performance LC-MS/MS to obtain the concentration of 65 target metabolites involved in the energy pathways and whole lipidome profiles. Capacity and limitation for multiomics rewiring of A. tonsa are discussed within an adaptive context and in light of fitness-related life-history trait responses and genomic evidence.

 Does rapid adaptation to ocean warming and acidification leave behind a cellular metabolomic and lipidomic signature in a marine copepod? 

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

The vent crab (Xenograpsus testudinatus), a dominant species in shallow water hydrothermal vents of Kueishan Island (Taiwan) and the Northwest Pacific fire ring, exhibits no significant genetic differentiation among populations. The underlying physiological traits and behavioral adaptations facilitating its survival in these environments are yet to be elucidated. This study collected X. testudinatus from two physicochemically contrasting sites: Kueishan Island and Shōwa Iōjima (Japan), the latter characterized by higher CO2 levels but lacking sulfides. Hemolymph analysis revealed comparable glucose levels between populations, but higher lactate in Shōwa Iōjima crabs, suggesting elevated CO2 contributes to anaerobic metabolism. In Kueishan Island, hemolymphic lactate positively correlated with sulfide presence and negatively with alkalinity, indicating a significant association between sulfide concentrations, alkaline components, and the regulation of anaerobic metabolic processes in the organism. Re-acclimatization experiments demonstrated a rapid lactate increase upon sulfide reintroduction, suggesting the importance of anaerobic respiration in adaptation. Moreover, vent crabs exhibited no positive sulfide chemotaxis, with Kueishan Island crabs displaying negative chemotaxis, potentially avoiding highly toxic areas. This study reveals diverse metabolic traits and behavioral responses employed by X. testudinatus to thrive in distinct hydrothermal habitats, underscoring the importance of phenotypic plasticity in their success.

Metabolic traits, chemotaxis, and environmental interactions of hydrothermal vent crab Xenograpsus testudinatus

While the compliant skin of dolphin has long been believed to play a crucial role in reducing skin friction drag owing to its flexibility and sensitivity, most conventional studies have been focused on the static skin microstructure and the hydrodynamic pressured-excited passive deformation, which could not provide a convinced solution to the mystery of Gray’s paradox. In this study, inspired by microvibrations measured on dolphin skin, we hypothesize that a dynamically undulating skin surface actuated by the microvibrations enables effectively altering the turbulent boundary layer adjacent to the skin, resulting in decreasing the velocity fluctuations, thus in reducing skin-friction drag. We constructed an idealized model of open channel with a portion of the bottom wall undergoing the microvibrations and carried out a series of numerical simulations to investigate the characteristics of the boundary layer flow in terms of traveling and standing waves. We found that the microvibrations-excited skin/wall surface can create a reversed flow against or enhance the streamwise flow in the viscous sublayer of the boundary layer, substantially leading to a negative friction drag or a negative total drag, hence greatly reducing or even eliminating the drag to generate a thrust. The results reveal that a novel drag reduction mechanism can be achieved by means of the dolphin-inspired microvibrations, which thus may provide a highly plausible explanation for the long-standing mystery of the excellent hydrodynamic performance in dolphin swimming.

Can compliant skin vibration provide a novel drag reduction strategy in dolphin swimming?

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

Predator-prey relationships are an important factor shaping ecological communities. Functional response (FR) describes the relationship between the food resource density and amount of food consumed by a single predator and is commonly used to study the role of predator-prey interactions in population dynamics. Elevated temperature related to global change is likely to modify consumer-resource interactions. Another important factor is predator density, as hunting individuals can be positively or negatively influenced by nearby conspecifics. Higher energy expenditure in elevated temperature requires greater foraging activity (enhancing foraging efficiency), which in turn may increase the competitive pressure between multiple predators and lead to predator interference (reducing foraging efficiency). This underlies the need to include predator density as a factor affecting foraging efficiency when studying effects of rising temperatures. Here, we performed a laboratory experiment using three densities of a fish predator (pumpkinseed, Lepomis gibbosus) (1, 2 and 4 specimens), two temperatures (25 and 28 oC) and 6 prey densities. Using FR approach, we showed the effect of temperature on foraging efficiency of single and 2 predators, but not on foraging of a group of 4 predators. Moreover, increased conspecific presence strongly reduced predator efficiency at a lower temperature, whereas, at a higher temperature, conspecific effect was totally absent (2 individuals) or lower (4 individuals). Our study indicates that predator density is an important factor that should be considered in experiments on the effects of environmental change on foraging efficiency. This research was supported by National Science Centre, Poland (Grant No. 2020/39/D/NZ8/01226)

Interactive effects of density and elevated temperature on foraging efficiency of aquatic predator

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

Tropical rainforest research was long the preserve of rich white men and the resulting literature was the same. This early bias in tropical research and publication may still be reflected in reading lists and recommended sources in higher education. We report on a study analysing the authorship of papers in the final year undergraduate option “Tropical Ecology” in SBOHVM University of Glasgow. The methodology utilised was that proposed by Bird and Pitman (2019) identifying gender, geography, and ethnicity of the authors. Nearly 79% of authors were male; 93.8% of authors whose ethnicity was identified were from non-BAME backgrounds; 80% of the authors were affiliated to institutes or universities in the global north. These results were reported to staff on the course with two outputs so far: reconsideration of the reading list and replacement of sources where possible; tutorial and discussion sessions with students taking the course to address the issues.


Physiological response to acute warming of reproducing male and female polar cod (Boreogadus saida) using MRI

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DNA methylation alterations during anoxia and re-oxygenation in crucian carp brain

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Physiological response to acute warming of reproducing male and female polar cod (Boreogadus saida) using MRI

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Next from SEB Conference Prague 2024

DNA methylation alterations during anoxia and re-oxygenation in crucian carp brain

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PRESENTATIONS

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COMPANY

RESOURCES

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