Czechia

This work examined the role of central venous pressure (CVP), an understudied component of cardiac regulation in fishes, in tilapia faced with a number of environmental challenges. First, we measured the heart rate (fH), cardiac output (Q), stroke volume (SV) and CVP of 30℃-acclimated fish, and those acutely exposed to 24℃, following titrations of zatebradine hydrocholoride (i.e., a pharmacological agent that decreases intrinsic fH). As predicted, fH and Q were ~40% lower in the acutely cooled fish (Q10 ~ 2.3) and both groups had very comparable (i.e., within 10%) values for SV (i.e., SV was temperature insensitive). Interestingly, the CVP of fish at 24℃ was higher than that in 30℃-acclimated fish across all concentrations of zatebradine (i.e., CVP increased from 0.04–0.11 kPa vs. -0.09–0.07 kPa, respectively, as fH was reduced), and this was reflected in a right-shifted relationship between CVP and SV for the 24℃ fish. These data suggest that the acutely cooled tilapia required a higher CVP to attain a similar SV as compared to 30℃ conspecifics. Ongoing experiments are now being performed on 25℃-acclimated tilapia to measure the same cardiovascular parameters (with the addition of oxygen consumption and tissue-oxygen extraction) when: i) exposed to critical thermal maximum (CTMax) and minimum (CTMin) tests at normoxia (100% air sat.); and ii) when exposed to acute/severe hypoxia (30% air sat.) followed by a CTMax test. These data will also be presented at the SEB 2024 conference in Prague.

SEB Conference Prague 2024

What Role Does Central Venous Pressure Play in Supporting Cardiac Function in Nile Tilapia (Oreochromis niloticus) Exposed to Environmental Challenges?

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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.

Thrombosis and thromboembolic complications are the dominant pathology in the general structure of mortality and mortality in the adult population. For this reason, the development of new potential drugs with antithrombotic effects with a low risk of side effects is one of the promising areas of modern science.

Preclinical evaluation of the effectiveness of antithrombotic drugs

In a 10-month experimental study, we assessed the combined impact of warming and acidification on critical life stages of small-spotted catshark (Scyliorhinus canicula). Using recently developed frameworks, we disentangled individual and group responses to two climate scenarios projected for 2100 (SSP2-4.5: Middle of the road and SSP5-8.5: Fossil-fueled Development). Seasonal temperature fluctuations revealed the acute vulnerability of embryos to summer temperatures, with hatching success ranging from 82% for the control and SSP2-4.5 treatments to only 11% for the SSP5-8.5 treatment. The death of embryos was preceded by distinct individual growth trajectories between the treatments, and also revealed inter-individual variations within treatments. Embryos with the lowest hatching success had lower yolk consumption rates, and growth rates associated with a lower energy assimilation, and almost all of them failed to transition to internal gills. Within 6 months after hatching, no additional mortality was observed due to cooler temperatures.

Shark critical life stage vulnerability to monthly temperature variations under climate change

Climate change is pushing temperatures towards intolerable limits for many fishes. It is therefore crucial that we understand the capacity of animals to withstand warming to inform conservation actions. Yet, we currently lack evidence of how intraspecific factors, such as body size or population, affect the capacity of individuals to tolerate warming. Using black bream (Acanthopagrus butcheri) as a focal species, we tested two hypotheses: first, that population-level differences exist in thermal tolerance, with northern populations being more tolerant of warming; and second, that upper thermal limits increase with increasing body size. Black bream grow upwards of 2 kg in size and form genetically distinct populations among estuaries along the West Australian coastline, offering a natural experiment of how intraspecific factors affect temperature tolerance. The first hypothesis was tested by measuring the critical thermal maximum (CTmax) of fish from four distinct populations along an eight-degree latitudinal gradient. The influence of body mass on CTmax was tested across a 6- to 8-fold body mass range. These data provide critical insight into the capacity of black bream to cope with environmental warming. We will highlight the importance of intraspecific factors when assessing a species' vulnerability to climate change.

Are all fish the same? Importance of considering how intraspecific factors shape thermal limits

The global application of Transeius montdorensis (Acari: Phytoseiidae) mites as biological control agents across various protected crops has proven effective against small insects like thrips and whiteflies, as well as spider mites, broad mites, and russet mites. This research evaluated the development and reproduction of T. montdorensis when fed on diverse diets: cattail pollen (Typha latifolia L.), living dried fruit mite (Carpoglyphus lactis), frozen C. lactis eggs, and a combination of frozen C. lactis eggs and T. latifolia pollen. The results indicated that females consuming the mixture of frozen eggs of C. lactis and T. latifolia pollen exhibited superior total fecundity and daily oviposition rates. Moreover, the intrinsic rate of increase (rm) and net productive rate (R0) of T. montdorensis females fed on the mixed diet were highest among all diets tested. In contrast, the immature period was significantly longer for mites on a diet of living C. lactis compared to those on three other alternative diets. Importantly, utilizing frozen C. lactis eggs (and T. latifolia pollen) mitigates the risk of infestation and contamination from the dried fruit mites which is important for laboratories and field settings when releasing the predator colonies. Consequently, we present a safer strategy for multiplying T. montdorensis in laboratory conditions. Finally, our findings suggest that the application of frozen C. lactis eggs and T. latifolia pollen, potentially applicable to other predatory mite species, offers significant time and cost savings for scientists and companies.

Optimization of rearing Transeius montdorensis in laboratory conditions

Carnivorous plants have fascinated researchers for their unique adaptations to nutrient-poor environments, particularly their ability to capture and digest prey. However, it is still unclear whether pollutants accumulated in prey can be transferred to carnivorous plants. Black soldier flies (Hermetia illucens) have garnered attention for their remarkable potential in various environmental applications, including waste management and nutrient recycling. Furthermore, their capacity to bioaccumulate contaminants presents an intriguing avenue for bioremediation research.
We aim to explore the extent to which black soldier fly larvae take up cadmium and PFAS (Per- and Polyfluoroalkyl Substances) from the substrate, how these contaminants are passed along the different life stages of the insect, and finally to what extent carnivorous plants (Venus Fly Traps; Dionaea muscipula) accumulate these substances after consuming contaminated prey.
The study consists of a series of controlled exposure experiments where Venus flytraps are exposed to PFAS or cadmium through: 1) soil, 2) larvae and flies exposed to polluted substrate during their larval stages, or 3) the combination of both. After solvent extraction and solid phase extraction, Cadmium and PFAS in the organisms is quantified using ICP-MS and UPLC-MS/MS respectively.
Results from this study, for the first time, will reveal bioaccumulation patterns of cadmium and PFAS in larvae and highlight potential trophic transfer of pollutants in Venus fly traps.
Overall, this research will help to understand pollutant transfer dynamics and to develop innovative bioremediation approaches that harness the natural capabilities of carnivorous plants and Black soldier flies.

Tracing the contamination's footprint: does cadmium and PFAS accumulate in Venus Fly trap when fed with contaminated Black Soldier Flies?

Estuaries face heightened vulnerability due to global changes, including frequent intensified flooding from high-intensity rainfall events, which induce sudden changes in environmental parameters. While estuarine organisms thrive in fluctuating conditions, their responses to intense and prolonged stressors may vary. Furthermore, the combined effects of stressors (e.g., decreased salinity and pH, increased turbidity) encountered during floods have rarely been studied on invertebrates under controlled conditions. Consequently, we evaluated the sensitivity of three dominant mollusk species (Littorina saxatilis, Macoma balthica, Mytilus spp.) to spring floods conditions. During 5 weeks, we exposed specimens to a 12-level gradient of exposure to periodic freshwater injections ranging from 0 to 9 days, under both control (salinity 0, pH 8.1, suspended sediment 0 mg L-1) and spring flood conditions (salinity 0, pH 5.7, suspended sediment 325 mg L-1). Mortality, growth and shell wear were measured after 2.5 and 5 weeks. For each species and sampling period, we used mixed linear models with two fixed factors: treatment (two levels, "control" or "spring floods") and hypoosmotic stress period (12 levels). Breakpoint analyses were used to identify sudden changes in each significant regression. Spring flood conditions amplified the negative impact of freshwater exposure on the mortality and induced greater shell wear of all species. Additionally, species-specific vulnerability levels were detected. Extreme events could therefore be key factors determining species distribution and functioning of estuarine ecosystems. Our study underscores the need to consider ecologically relevant combinations of environmental factors representing the complexity of natural conditions.

Surviving the deluge: Examining the vulnerability of an estuarine mollusk assemblage to water changes associated to flooding conditions

During heat exposure, birds face a trade-off between
hyperthermia and dehydration. Numerous studies have
attempted to predict cooling costs for birds, which are expected
to increase with global warming. Although modelling dehydration
risk is important, it does have its limitations, and do not replace
direct measurement of hydration status. In fact, studies
assessing the effects of temperature on the hydration status of
wild birds are surprisingly rare. In this article, we discuss the
experimental evidence for the hyperthermia–dehydration
tradeoff, and the limitations of modelling avian dehydration risk
through set thermal limits. In addition, we present a systematic review of physiological
markers of dehydration for avian species. We find that plasma
osmolarity and plasma concentrations of sodium and chloride
are the most reliable markers of dehydration, and seem to scale
with dehydration severity. Hematocrit appears to predict
dehydration but multiple concerns impede its suitability. Plasma
concentrations of uric acid, urea and creatinine may represent
adequate markers of dehydration. Alternatively, characteristics
of the excreta may represent less-invasive means to assess
hydration status.

Physiological markers of avian dehydration and perspectives in ecophysiology: assessing the hyperthermia-dehydration tradeoff

Changed seasonality and increasing temperatures are hallmarks of the ongoing climate change and challenge the viability of individuals, populations, species, and ecosystems. Recent research suggests that aquatic ectotherms such as fish, especially early life-stages are vulnerable to increasing temperatures. To understand, predict, and possibly mitigate the consequences of climate change, it is thus crucial to investigate the causes of variation in early life-stage thermal performance of ectotherms. Egg size has received considerable attention in this context, but previous studies have been limited to species and population comparisons, neglecting the role of egg size variation structuring variation in thermal performance among individuals within populations. This constrains our mechanistic understanding of egg size as a modulator of thermal performance and how organisms may respond to climate change. To test how intraspecific variation in egg size influences thermal performance, we conducted a split-brood experiment where eggs from 64 female pike (Esox lucius) from the same population were fertilized and incubated at four temperatures until hatching. Results showed that larger eggs had higher hatching performance in low temperatures whereas smaller eggs were more successful in higher temperatures. This suggests that fitness advantages associated with larger eggs may change in the future climate.

Smaller pike eggs outperform bigger eggs in a global warming scenario

Wild organisms are usually infected with a whole range of parasites, however, the infection status of organisms is not usually taken into consideration in ecological and food web studies. The impact that parasites can have on their host organisms, affecting their food intake and internal resource use, might drive to differences in the isotopic composition or niche between infected and uninfected organisms, and thus to erroneous conclusions in stable isotope ecology studies. 
This is the first time that controlled diet-switch experiments and stable isotope analyses (whole tissue, bulk SIA, 13C and 15N) have been performed on a host-parasite system comparing infected and uninfected individuals. Our results highlight the importance of accounting for infection status when conducting ecological studies based on stable isotopes, also contributing to fill the gap of parasite contribution to food webs. 


Importance of accounting for the infection status of an organism in isotope ecology studies: Using feeding experiments as an example

Exploration provides information of the environment and its associated points of interest such as food, threats or mates. However, in experimental biology, exploration is vastly described as distance or area covered by the animals (typically rodents). Usually, experimental tests commonly used in laboratories tend to prioritise the minimisation of variables over the complexity of natural environments. While these setups have provided valuable insights, the technological advent of new analysis and 3D printing technologies, allows us to go beyond overly simplistic environments, in order to better understand animal behaviour in contexts that more closely mimic their natural habitats.
We designed an Enriched Open Field (EOF) by including modular plastic structures in a classic squared open field (OF) arena for mice in order to increase the number of environmentally relevant landmarks in the arena, so as the quantity of regions with exploratory salience. We tested CD-1 and C57/BL6 female mice roaming freely in the EOF and OF arenas for 10 minutes. 
As expected, we observed differences between strains, with greater exploration measures in the CD-1 strain. Animals tested in the EOF showed more consistent exploratory patterns, even if they were previously habituated to the modular pieces in the context of a home cage. The average speed of EOF tested animals was greater and the movement more continuous.
Our study suggests that the presence of structures may mimic more naturalistic environments, thereby promoting exploratory behaviours that are closer to those exhibited in the animals' natural habitat when foraging or looking for social cues. 


What Role Does Central Venous Pressure Play in Supporting Cardiac Function in Nile Tilapia (Oreochromis niloticus) Exposed to Environmental Challenges?

Next from SEB Conference Prague 2024

Preclinical evaluation of the effectiveness of antithrombotic drugs

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