Diving behaviour of a reptile (Crocodylus johnstoni) in the wild: Interactions with heart rate and body temperature

The differences in physical properties of air and water pose unique behavioural and physiological demands on semiaquatic animals. The aim of this study was to describe the diving behaviour of the freshwater crocodile Crocodylus johnstoni in the wild and to assess the relationships between diving, body temperature, and heart rate. Time-depth recorders, temperature-sensitive radio transmitters, and heart rate transmitters were deployed on each of six C. johnstoni (4.0-26.5 kg), and data were obtained from five animals. Crocodiles showed the greatest diving activity in the morning (0600-1200 hours) and were least active at night, remaining at the water surface. Surprisingly, activity pattern was asynchronous with thermoregulation, and activity was correlated to light rather than to body temperature. Nonetheless, crocodiles thermoregulated and showed a typical heart rate hysteresis pattern (heart rate during heating greater than heart rate during cooling) in response to heating and cooling. Additionally, dive length decreased with increasing body temperature. Maximum diving length was 119.6 min, but the greatest proportion of diving time was spent on relatively short

Social labs as good practice for transdisciplinary engagement processes in research and innovation

This article discusses a ‘Social Lab process’ applied in the field of research and innovation as good practice for transdisciplinary processes, and elaborates upon the structure and dynamics of these processes. It sheds light on how engagement processes could be set up for a more inclusive and participant-friendly atmosphere, allowing for meaningful and sustainable outcomes. Supported by data from a qualitative analysis of 19 Social Lab experiences according to the thematic programmes of the European Commission Horizon 2020 research framework programme, this article outlines requirements that need to be taken into account when implementing a transdisciplinary process in a Social Lab. Based on the concept of transdisciplinary research and the experience of this one-and-a-half-year process, the elements of participatory approaches required for successful implementation of a Social Lab, starting with inviting participants to develop small implementation projects (pilot activities) are described. The qualitative analysis of the process documentations highlights the importance of a clear definition of the framework and purpose of the process. Concrete assignments of the lab teams and roles, and the implementation of pilot activities, further proved crucial for successful and sustainable results. On this basis, recommendations for a fruitful participatory process are formulated

The effect of heat transfer mode on heart rate responses and hysteresis during heating and cooling in the estuarine crocodile Crocodylus porosus

The effect of heating and cooling on heart rate in the estuarine crocodile Crocodylus porosus was studied in response to different heat transfer mechanisms and heat loads. Three heating treatments were investigated. C. porosus were: (1) exposed to a radiant heat source under dry conditions; (2) heated via radiant energy while half-submerged in flowing water at 23degreesC and (3) heated via convective transfer by increasing water temperature from 23degreesC to 35degreesC. Cooling was achieved in all treatments by removing the heat source and with C. porosus half-submerged in flowing water at 23degreesC. In all treatments, the heart rate of C. porosus increased markedly in response to heating and decreased rapidly with the removal of the heat source. Heart rate during heating was significantly faster than during cooling at any given body temperature, i.e. there was a significant heart rate hysteresis. There were two identifiable responses to heating and cooling. During the initial stages of applying or removing the heat source, there was a dramatic increase or decrease in heart rate ('rapid response'), respectively, indicating a possible cardiac reflex. This rapid change in heart rate with only a small change or no change in body temperature

Control of heart rate during thermoregulation in the heliothermic lizard Pogona barbata: importance of cholinergic and adrenergic mechanisms

During thermo regulation in the bearded dragon Pogona barbata, heart rate when heating is significantly faster than when cooling at any given body temperature (heart rate hysteresis), resulting in faster rates of heating than cooling. However, the mechanisms that control heart rate during heating and cooling are unknown. The aim of this study was to test the hypothesis that changes in cholinergic and adrenergic tone on the heart are responsible for the heart rate hysteresis during heating and cooling in P. barbata. Heating and cooling trials were conducted before and after the administration of atropine, a muscarinic antagonist, and sotalol, a beta-adrenergic antagonist. Cholinergic and beta-adrenergic blockade did not abolish the heart rate hysteresis, as the heart rate during heating was significantly faster than during cooling in all cases. Adrenergic tone was extremely high (92.3%) at the commencement of heating, and decreased to 30.7% at the end of the cooling period. Moreover, in four lizards there was an instantaneous drop in heart rate (up to 15 beats min(-1)) as the heat source was switched off, and this drop in heart rate coincided with either a drop in beta-adrenergic tone or an increase in cholinergic tone. Rates of heating were significantly faster during the cholinergic blockade, and least with a combined cholinergic and beta-adrenergic blockade. The results showed that cholinergic and beta-adrenergic systems are not the only control mechanisms acting on the heart during heating and cooling, but they do have a significant effect on heart rate and on rates of heating and cooling

Benzyl- and dibenzyl tetrahydropyridinylidene ammonium salts with antiplasmodial and antitrypanosomal activity

Several 1-benzyl and 1,3-dibenzyl derivatives of tetrahydropyridinylidene salts with differing electron withdrawing substituents at the aromatic residues have been prepared. In addition, the amine moiety in position 4 was varied. The new compounds were investigated for their antiplasmodial and antitrypanosomal activities as well as for their cytotoxicity. They were characterized using FT-IR, HRMS and NMR spectroscopy. Structure-activity relationships including reported compounds are discussed. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s)

Antarctic fish can compensate for rising temperatures: Thermal acclimation of cardiac performance in Pagothenia borchgrevinki

Antarctic fish Pagothenia borchgrevinki in McMurdo Sound, Antarctica, inhabit one of the coldest and most thermally stable of all environments. Sea temperatures under the sea ice in this region remain a fairly constant -1.86 degrees C year round. This study examined the thermal plasticity of cardiac function in P. borchgrevinki to determine whether specialisation to stable low temperatures has led to the loss of the ability to acclimate physiological function. Fish were acclimated to - 1 degrees C and 4 degrees C for 4 - 5 weeks and cardiac output was measured at rest and after exhaustive exercise in fish acutely transferred from their acclimation temperature to - 1, 2, 4, 6 and 8 degrees C. In the - 1 degrees C acclimated fish, the factorial scope for cardiac output was greatest at - 1 degrees C and decreased with increasing temperature. Increases in cardiac output with exercise in the - 1 degrees C acclimated fish was achieved by increases in both heart rate and stroke volume. With acclimation to 4 degrees C, resting cardiac output was thermally independent across the test temperatures; furthermore, factorial scope for cardiac output was maintained at 4, 6 and 8 degrees C, demonstrating thermal compensation of cardiac function at the higher temperatures. This was at the expense of cardiac function at - 1 degrees C, where there was a significant decrease in factorial scope for cardiac output in the 4 degrees C acclimated fish. Increases in cardiac output with exercise in the 4 degrees C acclimated fish at the higher temperatures was achieved by changes in heart rate alone, with stroke volume not varying between rest and exercise. The thermal compensation of cardiac function in P. borchgrevinki at higher temperatures was the result of a change in pumping strategy from a mixed inotropic/chronotropic modulated heart in - 1 degrees C acclimated fish at low temperatures to a purely chronotropic modulated heart in the 4 degrees C acclimated fish at higher temperatures. In spite of living in a highly stenothermal cold environment, P. borchgrevinki demonstrated the capacity to thermally acclimate cardiac function to elevated temperatures, thereby allowing the maintenance of factorial scope and the support of aerobic swimming at higher temperatures

Living in flowing water increases resistance to ultraviolet B radiation

Ultraviolet B radiation (UV-B) is an important environmental driver that can affect locomotor performance negatively by inducing production of reactive oxygen species (ROS). Prolonged regular exercise increases antioxidant activities, which may alleviate the negative effects of UV-B-induced ROS. Animals naturally performing exercise, such as humans performing regular exercise or fish living in flowing water, may therefore be more resilient to the negative effects of UV-B. We tested this hypothesis in a fully factorial experiment, where we exposed mosquitofish (Gambusia holbrooki) to UV-B and control (no UV-B) conditions in flowing and still water. We show that fish exposed to UV-B and kept in flowing water had increased sustained swimming performance (U-crit), increased antioxidant defences (catalase activity and glutathione concentrations) and reduced cellular damage (lipid peroxidation and protein carbonyl concentrations) compared with fish in still water. There was no effect of UV-B or water flow on resting or maximal rates of oxygen consumption. Our results show that environmental water flow can alleviate the negative effects of UV-Binduced ROS by increasing defence mechanisms. The resultant reduction in ROS-induced damage may contribute to maintain locomotor performance. Hence, the benefits of regular exercise are `transferred' to improve resilience to the negative impacts of UV-B. Ecologically, the mechanistic link between responses to different habitat characteristics can determine the success of animals. These dynamics have important ecological connotations when river or stream flow changes as a result of weather patterns, climate or human modifications

New derivatives of the multi-stage active Malaria Box compound MMV030666 and their antiplasmodial potencies

MMV's Malaria Box compound MMV030666 shows multi-stage activity against various strains of Plasmodium falciparum and lacks resistance development. To evaluate the importance of its diarylether partial structure, diarylthioethers and diphenylamines with varying substitution patterns were prepared. A number of evident structure-activity relationships were revealed. Physicochemical and pharmacokinetic parameters were determined experimentally (passive permeability) or calculated. Compared to the lead compound a diarylthioether was more active and less cytotoxic resulting in an excellent selectivity index of 850. In addition, pharmacokinetic and physicochemical parameters were improved

Transient Receptor Potential Ion Channels Control Thermoregulatory Behaviour in Reptiles

Biological functions are governed by thermodynamics, and animals regulate their body temperature to optimise cellular performance and to avoid harmful extremes. The capacity to sense environmental and internal temperatures is a prerequisite for the evolution of thermoregulation. However, the mechanisms that enable ectothermic vertebrates to sense heat remain unknown. The recently discovered thermal characteristics of transient receptor potential ion channels (TRP) render these proteins suitable to act as temperature sensors. Here we test the hypothesis that TRPs are present in reptiles and function to control thermoregulatory behaviour. We show that the hot-sensing TRPV1 is expressed in a crocodile (Crocodylus porosus), an agamid (Amphibolurus muricatus) and a scincid (Pseudemoia entrecasteauxii) lizard, as well as in the quail and zebrafinch (Coturnix chinensis and Poephila guttata). The TRPV1 genes from all reptiles form a unique clade that is delineated from the mammalian and the ancestral Xenopus sequences by an insertion of two amino acids. TRPV1 and the cool-sensing TRPM8 are expressed in liver, muscle (transversospinalis complex), and heart tissues of the crocodile, and have the potential to act as internal thermometer and as external temperatures sensors. Inhibition of TRPV1 and TRPM8 in C. porosus abolishes the typically reptilian shuttling behaviour between cooling and heating environments, and leads to significantly altered body temperature patterns. Our results provide the proximate mechanism of thermal selection in terrestrial ectotherms, which heralds a fundamental change in interpretation, because TRPs provide the mechanism for a tissue-specific input into the animals' thermoregulatory response