Research on stress coping style, i.e., the response of an organism to adverse conditions, which is constant over time and context, gained momentum in recent years, to better understand behavioural... Show moreResearch on stress coping style, i.e., the response of an organism to adverse conditions, which is constant over time and context, gained momentum in recent years, to better understand behavioural patterns in animal welfare. However, knowledge about the ontogeny of stress coping style is still limited. Here, we performed a detailed analysis of the light dark challenge behavioural assay in zebrafish larvae, where after acclimation in ambient light sudden alternating dark and light phases elicit an anxiety-like response. A principal component analysis on parameters related to locomotion (distance moved, swimming velocity, acceleration, mobility) and directionality (angular velocity, meandering of swimming path) revealed independence between the parameters determined in the light and the dark phases of the assay, indicating unrelated generalised behaviours per phase. However, high collinearity was observed between behavioural parameters within the same phase, indicating a robust response to the stimulus within behavioural phenotypes. Subsequently, this assay was used to determine the correlation between individual hatching time and the behavioural phenotype. The results show that fish that had hatched during daytime have a stronger behavioural response to the dark phase at 5 days post-fertilisation in locomotion related parameters and a weaker response in directionality related parameters, than fish that had hatched during nighttime. These results show that behavioural responses to the light dark challenge assay are robust and can be generalised for the light and the dark phase, and that diel hatching time may determine the behavioural phenotype of an individual. Show less
In Gaucher disease (GD), the deficiency of glucocerebrosidase causes lysosomal accumulation of glucosylceramide (GlcCer), which is partly converted by acid ceramidase to glucosylsphingosine (GlcSph... Show moreIn Gaucher disease (GD), the deficiency of glucocerebrosidase causes lysosomal accumulation of glucosylceramide (GlcCer), which is partly converted by acid ceramidase to glucosylsphingosine (GlcSph) in the lysosome. Chronically elevated blood and tissue GlcSph is thought to contribute to symptoms in GD patients as well as to increased risk for Parkinson's disease. On the other hand, formation of GlcSph may be beneficial since the water soluble sphingoid base is excreted via urine and bile. To study the role of excessive GlcSph formation during glucocerebrosidase deficiency, we studied zebrafish that have two orthologs of acid ceramidase, Asah1a and Asah1b. Only the latter is involved in the formation of GlcSph in glucocerebrosidase-deficient zebrafish as revealed by knockouts of Asah1a or Asah1b with glucocerebrosidase deficiency (either pharmacologically induced or genetic). Comparison of zebrafish with excessive GlcSph (gba1-/- fish) and without GlcSph (gba1-/-:asah1b-/- fish) allowed us to study the consequences of chronic high levels of GlcSph. Prevention of excessive GlcSph in gba1-/-:asah1b-/- fish did not restrict storage cells, GlcCer accumulation, or neuroinflammation. However, GD fish lacking excessive GlcSph show an ameliorated course of disease reflected by significantly increased lifespan, delayed locomotor abnormality, and delayed development of an abnormal curved back posture. The loss of tyrosine hydroxylase 1 (th1) mRNA, a marker of dopaminergic neurons, is slowed down in brain of GD fish lacking excessive GlcSph. In conclusion, in the zebrafish GD model, excess GlcSph has little impact on (neuro)inflammation or the presence of GlcCer-laden macrophages but rather seems harmful to th1-positive dopaminergic neurons. Show less
Standardization and reduction of variation is key to behavioural screening of animal models in toxicological and pharmacological studies. However, individual variation in behavioural and... Show moreStandardization and reduction of variation is key to behavioural screening of animal models in toxicological and pharmacological studies. However, individual variation in behavioural and physiological phenotypes remains in each laboratory population and can undermine the understanding of toxicological and pharmaceutical effects and their underlying mechanisms. Here, we used zebrafish (ABTL-strain) larvae to explore individual consistency in activity level and emergence time, across subsequent days of early development (6-8 dpf). We also explored the correlation between these two behavioural parameters. We found inter-individual consistency over time in activity level and emergence time, but we did not find a consistent correlation between these parameters. Subsequently, we investigated the impact of variation in activity level on the effect of a 1% ethanol treatment, suitable for our proof-of-concept case study about whether impact from pharmacological treatments might be affected by inter-individual variation in basal locomotion. The inter-individual consistency over time in activity level did not persist in this test. This was due to the velocity change from before to after exposure, which turned out to be a dynamic individual trait related to basal activity level: low-activity individuals raised their swimming velocity, while high-activity individuals slowed down, yielding diametrically opposite response patterns to ethanol exposure. We therefore argue that inter-individual consistency in basal activity level, already from 6 dpf, is an important factor to take into account and provides a practical measure to improve the power of statistical analyses and the scope for data interpretation from behavioural screening studies. Show less
Plastic nanoparticles originating from weathering plastic waste are emerging contaminants in aquatic environments, with unknown modes of action in aquatic organisms. Recent studies suggest that... Show morePlastic nanoparticles originating from weathering plastic waste are emerging contaminants in aquatic environments, with unknown modes of action in aquatic organisms. Recent studies suggest that internalised nanoplastics may disrupt processes related to energy metabolism. Such disruption can be crucial for organisms during development and may ultimately lead to changes in behaviour. Here, we investigated the link between polystyrene nanoplastic (PSNP)-induced signalling events and behavioural changes. Larval zebrafish exhibited PSNP accumulation in the pancreas, which coincided with a decreased glucose level. By using hyperglycemic and glucocorticoid receptor (Gr) mutant larvae, we demonstrate that the PSNP-induced disruption in glucose homoeostasis coincided with increased cortisol secretion and hyperactivity in challenge phases. Our work sheds new light on a potential mechanism underlying nanoplastics toxicity in fish, suggesting that the adverse effect of PSNPs are at least in part mediated by Gr activation in response to disrupted glucose homeostasis, ultimately leading to aberrant locomotor activity. Show less
Brun, N.R.; Hage, P. van; Hunting, E.R.; Haramis, A.-P.G.; Vink, S.C.; Vijver, M.G.; ... ; Tudorache, C. 2019
Plastic nanoparticles originating from weathering plastic waste are emerging contaminants in aquatic environments, with unknown modes of action in aquatic organisms. Recent studies suggest that... Show morePlastic nanoparticles originating from weathering plastic waste are emerging contaminants in aquatic environments, with unknown modes of action in aquatic organisms. Recent studies suggest that internalised nanoplastics may disrupt processes related to energy metabolism. Such disruption can be crucial for organisms during development and may ultimately lead to changes in behaviour. Here, we investigated the link between polystyrene nanoplastic (PSNP)-induced signalling events and behavioural changes. Larval zebrafish exhibited PSNP accumulation in the pancreas, which coincided with a decreased glucose level. By using hyperglycemic and glucocorticoid receptor (Gr) mutant larvae, we demonstrate that the PSNP-induced disruption in glucose homoeostasis coincided with increased cortisol secretion and hyperactivity in challenge phases. Our work sheds new light on a potential mechanism underlying nanoplastics toxicity in fish, suggesting that the adverse effect of PSNPs are at least in part mediated by Gr activation in response to disrupted glucose homeostasis, ultimately leading to aberrant locomotor activity. Show less
Metabolic rate is a critical factor in animal biology and ecology, providing an objective measure that can be used in attributing a cost to different activities and to assessing what animals do... Show moreMetabolic rate is a critical factor in animal biology and ecology, providing an objective measure that can be used in attributing a cost to different activities and to assessing what animals do against some optimal behaviour. Ideally, metabolic rate would be estimated directly by measuring heat output but, until recently, this has not been easily tractable with shes so instead metabolic rate is usually esti- mated using indirect methods. In the laboratory, oxygen consumption rate is the indirect method most frequently used for estimating metabolic rate, but technical requirements preclude the measurement of either heat output or oxygen consumption rate in free-ranging shes. There are other eld methods for estimating metabolic rate that can be used with mammals and birds but, again, these cannot be used with shes. Here, the use of electronic devices that record body acceleration in three dimensions (accelerometry) is considered. Accelerometry is a comparatively new telemetric method for assessing energy metabolism in animals. Correlations between dynamic body acceleration (DBA) and oxygen consumption rate demonstrate that this will be a useful proxy for estimating activity-speci c energy expenditure from shes in mesocosm or eld studies over extended periods where other methods (e.g. oxygen consumption rate) are not feasible. DBA therefore has potential as a valuable tool for attribut- ing cost to different activities. This could help in gaining a full picture of how shes make energy-based trade-offs between different levels of activity when faced with con icting or competing demands aris- ing from increased and combined environmental stressors. Show less
Tudorache, C.; Burgerhout, E.; Brittijn, S.; Thillart, G. van den 2015
