Czechia

Amphibians are resilient species that have adapted during their long evolutionary history to rather diverse environmental conditions. Current climate change, however, is pushing many species tolerance limits, especially as it is translating into not only increased temperature but also, increased drought and shortened pond duration. Some species have evolved the ability to adaptively alter their phenotype in response to some of these factors, but the combination of hazards and the rate at which they are taking place, may exceed the ability of amphibians to cope. Reduced pond duration may trigger developmental acceleration in amphibian larvae, allowing them to reach metamorphosis sooner, but at the cost of doing so smaller and with depleted fat reserves. Moreover, if they metamorphose onto a harsher environment, the odds of survival during the juvenile stage may be severely reduced. We are studying the plastic responses of tadpoles of the spadefoot toad, Pelobates cultripes, to risk of pond drying, which is a complex combination of reduced water level, increased temperature, increased larval density and reduced food availability. We then also studied the carry-over effects of the developmental alterations experienced by larvae onto the juvenile stage, especially when they then face drier and warmer environments, monitoring juvenile survival, growth, activity pattern, hormonal levels and thermal tolerance.

SEB Conference 2024

Plastic responses of amphibians to shortened pond duration and increased drought and temperature

developmental plasticity

carry-over effects

climate change

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technical paper

Insects use the adhesive force working on the soles of the legs for walking on the walls and ceilings. Particularly, fruit flies achieve stable wall walking due to the scale effect. However, the ground reaction force (GRF) during wall walking has not been measured because of lightness of their body. In this study, we use a force plate whose tilt angle can be adjusted to measure the total GRF of all legs in the shear and vertical directions when a fruit fly walks on a wall. The force plate has measuring section with an area of 10 mm^2 and spring structures that move in the shear and vertical directions, and it measures forces in two axes using Hooke's law. The resolution in both directions is 0.36 µN and 0.31 µN, which represents about 1/30 of its weight. It could be fabricated through a simple process by using thin film glass as the force plate material and processing the spring structure with a UV laser marker. It could adjust the inclination angle of the force plate via θ-axis stage, thereby the wall would be prepared. The GRF in two axis is measured when a fruit fly walks on the plate. When the force plate was placed horizontally, we confirmed that the fruit fly walked with almost no vibration in the shear and vertical directions.

Measurement of the ground reaction force of fruit fly using a tilted biaxial force plate

The equid locomotor transition is one of the most iconic morphofunctional shifts in terrestrial mammals. Throughout their evolution, equids reduced their side-digits, with different phylogenetic clades exhibiting greater or lesser degrees of digit reduction. One hypothesised driver behind the reduction (and loss in equinin equids) of side-digits is their potential lack of functionality during locomotion. However, hipparionin equids retain side-digits until their extinction during the middle-Pleistocene, despite coexisting with monodactyl equids for over 7 Ma. In this study, we aim to shed light on the functionality of the side-digits of extinct equids using an extant morphological bracket, comparing toe-ground interception across ecologically diverse ungulates which exhibit side-digits. Modern and extinct ungulate proximal phalanges were measured and compared across a broad range of taxa using a toe-reduction index (a morphometric measure of central-to-side-toe length). Using high-resolution 3D scans, joint range-of-motion was estimated from osteological material; we then built and analysed a series of ungulate distal limb skeletons, rotating the third proximal phalange parasagittally at biologically realistic, regularly spaced intervals. Toe-to-ground interception for the side-digits was scored for the varying degrees of central digit extension, and under hypothetically increasing substrate compliances (mimicking different underfoot conditions, e.g. mud). Our results from toe-reduction indices align with 3D virtual ROM experiments, which themselves demonstrate widespread functionality in the side digits of transitional and hipparionin equids (e.g. Nannippus). This preliminary study refutes the notion of functional redundancy in equid side-digits, paving the way for more advanced investigations in the future.

Using modern ungulate analogues to explore equid side-toe function through an iconic evolutionary transition

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).

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.

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

Telomeres are non-coding ‘caps’ on the end of chromosomes that change in length in response to growth, oxidative stress and various stressors. Due to this relationship, they have been proposed to link to organismal and cellular self-maintenance, and may be used as a biomarker of past stressors such as heat stress. Understanding how environmental temperature can impact telomere length and cellular maintenance is crucial for understanding the vast ways in which organisms' cellular and life-history processes may respond to predicted environmental warming. To further aid in validating telomeric biomarkers, we subjected two populations of Australian Painted Dragon lizards from differing ends of a temperature-aridity gradient to a three-month hot or cool thermal treatment. At the end of the experiment, we assessed the correlations of blood telomere length to four tissues (heart, liver, muscle and testes). We will discuss these results in terms of the uses and pitfalls of using telomere length as a biomarker and how the natal thermal environment and thermal treatments interact and influence telomere length.

Thermal effects on tissue telomere length in a colour polymorphic ectotherm, the role of thermal geographic variation.

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

I am an integrative evolutionary biologist studying the phenotypic and biogeographic impact of duplication. From single genes to entire genomes, duplications are often associated with adaptive radiations, evolutionary novelties, and decreased extinction during periods of environmental change. Most studied in plants, there are nevertheless thousands of these major duplication events across animals and fungi, with more being discovered each year. I investigated comparative biogeography of polyploid and diploid frogs in South America. I discovered a remarkable and novel trend of spatial clustering within polyploid lineages. In all five genera of South American frogs with variable ploidy, virtually all polyploid occurrences were found in the southeast, largely to the exclusion of diploids. In fact, polyploid species occur more closely with intergeneric polyploids than they do with congeneric diploids, suggesting an environment which selects for genome duplication. Polyploid occurrences were subject to greater levels of seasonal temperature fluctuation and agricultural impacts, either of which may contribute to the formation and fitness of polyploid lineages. Later, I expanded this framework into a global study encompassing amphibians, ray-finned fishes, and insects. On this scale, differences were even more pronounced between cytotypes. In each of the three clades, polypoid occurrences became more frequent with distance from the equator. I attributed this trend in large part to glaciation cycles, which were the most important model variable in all three clades

Macroecological consequences of whole-genome duplication: a latitudinal polyploid gradient in three vertebrate clades

Gut microbiomes are integral to animal eco-physiology and are hypothesized to shape the adaptive evolution of animal life. However, directly estimating the extent to which gut microbiomes are under selection within free-living animal populations is challenging. The inheritance mechanisms that allow for the intergenerational transmission of microbiome variation within animal populations are also unclear. However, joint characterization of the inheritance and fitness consequences of microbiome variation are critical for understanding the role of microbiota in animal adaptation. To address these knowledge gaps in parallel, I quantified relationships between gut microbiomes and host survival in the wild, by using shallow shotgun metagenomic sequencing to characterize microbiota communities in archived fecal samples collected across seven years of a long-term individual-based study of Sable Island feral horses (2820 samples from 905 individuals). Using quantitative genetic animal models, I then estimated the narrow-sense heritability and social transmissibility of survival-associated microbiota. Analysis of these data indicate that horse survival may be strongly connected to methane production in the hindgut. Furthermore, quantitative genetic analyses suggest the involvement of both host genetics and social effects in structuring the microbiome, and that these effects may be strongest for the microbiota most closely connected to horse survival. By dovetailing estimates of natural selection and inheritance, these results provide a fuller understanding of how host-microbiome relationships evolve in nature.

Straight from the horse's mouth: lessons of gut microbiome selection and inheritance from Sable Island

Assessment IS learning. The power of assessment to do more than just test knowledge and understanding is substantial. Making our assessments meaningful to our students’ future lives, and authentic to the skills they will need is a major priority in the evolving Higher Education sector. Ensuring that our assessments are also student-centred, and develop their skills both as bioscientists and as independent, self-regulated learners, is also an important necessity. This talk will focus on ways in which we can enhance our assessments to ensure they are focused on supporting student learning and preparing them for their future employment needs, and will highlight the challenges associated with this.

Meaningful and student-centred assessment in Biosciences education

Warmer temperatures can cause various physiological and phenotypic changes in plants, many of which with detrimental consequences, and theses processes are regulated by a diverse set of molecular mechanisms. Temperature is also a major parameter for RNA structure formation and stability, and the plant cell’s environment, with its constant shifts in temperature, might have created ideal conditions for RNA structures to be selected and genetically transmitted as an adaptive mechanism to warmer temperatures. In this talk, I will present our work on post-transcriptional regulation in plant perception and acclimation to warmer temperatures, with a focus on the role of RNA structures.

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Measurement of the ground reaction force of fruit fly using a tilted biaxial force plate

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Measurement of the ground reaction force of fruit fly using a tilted biaxial force plate

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How vulnerable are amphibians to global warming?

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