Georg Staaks

Impact of the cyanobacteria toxin, microcystin-LR on behaviour of zebrafish, Danio rerio

Abstract Quantitative behaviour of zebrafish, Danio rerio, was recorded to assess and predict long-term sublethal effects of the cyanobacteria toxin microcystin-LR (MCYST-LR; nominal concentrations of 0.5, 5, 15 and 50 μg litre−1) by using the automated BehavioQuant®. The exposure to MCYST-LR caused dose–effect related changes in spontaneous locomotor activity. Whereas the two lower exposure concentrations (0.5 and 5 μg litre−1) caused an increase in daytime motility, elevated exposures led to significantly decreased motilities. The highest exposure (50 μg litre−1) also reduced the spawning activity and success. In contrast to daytime activities, night-time swimming activity was significantly greater at the higher MCYST-LR exposures. The chronobiological analysis indicated a phase shift of maximum swimming activities and a lowered reaction on trigger points like feeding, at dusk and dawn. Furthermore, the results indicate some adverse consequences in reproduction success and in the spatial and temporal fit of the fish into its habitat.

Swimming efficiency and the influence of morphology on swimming costs in fishes

Swimming performance is considered a main character determining survival in many aquatic animals. Body morphology highly influences the energetic costs and efficiency of swimming and sets general limits on a species capacity to use habitats and foods. For two cyprinid fishes with different morphological characteristics, carp (Cyprinus carpio L.) and roach (Rutilus rutilus (L.)), optimum swimming speeds (Umc) as well as total and net costs of transport (COT, NCOT) were determined to evaluate differences in their swimming efficiency. Costs of transport and optimum speeds proved to be allometric functions of fish mass. NCOT was higher but Umc was lower in carp, indicating a lower swimming efficiency compared to roach. The differences in swimming costs are attributed to the different ecological demands of the species and could partly be explained by their morphological characteristics. Body fineness ratios were used to quantify the influence of body shape on activity costs. This factor proved to be significantly different between the species, indicating a better streamlining in roach with values closer to the optimum body form for efficient swimming. Net swimming costs were directly related to fish morphology.

Temporal pattern in swimming activity of two fish species ( Danio rerio and Leucaspius delineatus ) under chemical stress conditions

Circadian periodicity of swimming activity was investigated in two fish species, the zebrafish (Danio rerio) and the sunbleak (Leucaspius delineatus) under sublethal long-term exposure to the cyanobacteria toxin microcystin-LR (nominal concentrations of 0.5 μg l − 1, 5 μg l − 1, 15 μg l − 1, 50 μg l − 1) in 15-litre tanks. Swimming activity of fish was monitored continuously by using an automated video-monitoring and object-tracing system over a period of 17 days. Influenced by long-term exposure to microcystin-LR, Leucaspius delineatus reversed their significant diurnal swimming activity and the fish became statistically significant nocturnal. Danio rerio remained diurnal active, but a significant phase shift was registered. In both Danio rerio and Leucaspius delineatus analysis of time series by cosinor regression revealed microcystin-LR induced dose-dependent alterations of the mean of oscillation, amplitude, acrophase and period length in a different extent. For Danio rerio the periodogram analysis revealed a significant circadian component of swimming activity for control as well as exposure groups, whereby the spectral amplitude clearly decreased at microcystin-LR concentrations of 15 and 50 μg l − 1. For Leucaspius delineatus the amplitude of circadian rhythm was decreased at all exposure concentrations of MC-LR. Furthermore the dominance of circadian rhythm was clearly reduced, whereas the rate of ultradian rhythms increased at elevated MC-LR concentrations of 5 μg l − 1, 15 μg l − 1 and 50 μg l − 1. The studied temporal aspects of behaviour clearly indicated stress symptoms in both fish species, therefore it proved to be a relevant method to characterise the impact of toxic substances in the environment and for biomonitoring.

Tank size alters mean behaviours and individual rank orders in personality traits of fish depending on their life stage

Animals adjust their behaviour over time and contexts to cope with ecological and environmental variation. However, the presence of consistent between-individual differences in behaviour (i.e. personality) suggests that individual behaviour may be less flexible than previously thought. Here, we tested whether the size of the experimental tank and the ontogenetic stage of individuals affect estimates of average and consistent individual variation in activity and risk-taking behaviours in the eastern mosquitofish, Gambusia holbrooki, a fish model widely utilized for behavioural research. We measured risk taking and activity in juvenile, subadult and adult mosquitofish in a standard open-field test, in which the size of test tank varied linearly. We found strong evidence that spatial constraints alter mosquitofish behaviour. In particular, we observed that average activity increased with tank size, while the willingness of fish to take risks was independent of tank size. Moreover, juvenile fish exhibited, on average, lower risk-taking behaviours than older individuals. We highlight that the use of differently sized tanks may result in unequal variation in the average behaviour between juvenile and older fish, with escaping abilities of juvenile fish being underestimated in small environments. Most interestingly, we observed that variation in tank size triggered changes in the individual rank order for both risk taking and activity in juvenile fish, thus altering their personality estimates. In contrast, adult fish maintained consistent individual rank orders across all tank sizes. This study supports the hypothesis that behavioural repeatability increases with age, suggesting that personality estimates on adult animals may be less vulnerable to variation in laboratory contexts than those on juvenile ones.

The Influence of Tributyltin Chloride and Polychlorinated Biphenyls on Swimming Behavior, Body Growth, Reproduction, and Activity of Biotransformation Enzymes in Daphnia magna

ABSTRACT Exposure to tributyltin chloride (TBT) at 7.1 μg L−1 or polychlorinated biphenyls (PCB) at 1.5 μg L−1 significantly affected Daphnia magna causing rapid decreases in mean swimming activity and a change in the preferred swimming depth. Lower exposure concentrations (0.1 μg L−1 TBT or 0.1 μg L−1 PCB) did not significantly alter swimming behavior. Exposure to medium and high TBT concentrations (0.1 μg L−1 and 7.1 μg L−1) caused a decrease in body growth and decreased the number of newborn daphnids. PCB exposure at 1.5 μg L−1 and 12 μg L−1 did not affect reproduction or body growth of the animals. The lowest exposure levels (0.1 μg L−1 PCB or 0.02 μg L−1 TBT) did not alter any behavioral or ecophysiological parameter of the daphnids. Exposure to PCB as high as 15 μg L−1 or TBT as high as 6.6 μg L−1 had no effect on daphnid glutathione-S-transferase and glutathione-peroxidase activity.

The eye fluke Tylodelphys clavata affects prey detection and intraspecific competition of European perch (Perca fluviatilis)

Parasites that occupy the eyes of fish have the potential to affect visual perception and consequently alter the host’s behaviour, as these organs provide information about their surroundings. In an experimental study, the feeding behaviour of European perch (Perca fluviatilis) infested with the eye fluke Tylodelphys clavata was examined. The results showed that an individual’s ability to identify and approach food items was negatively affected by the infestation intensity of T. clavata. Additionally, the foraging success of an individual was reduced in competition with another, less heavily infested conspecific, when the same food resource was exploited. These alterations in the ability to locate food may have important consequences on the feeding strategy of the fish. Furthermore, the impaired feeding capability caused by T. clavata may also increase the predation risk as heavily infested fish need to spend more time foraging to attain a rate of food intake equivalent to less infested conspecifics.

How to Use Fish Behavior Analysis to Sensitively Assess the Hazard Potentials of Environmental Chemicals

Duringl their phylogenesis, all species have adapted to their distinct habitats and to naturally occurring environmental changes. By means of specific long-term self-regulation processes, species are able to react to these environmental changes and therefore maintain their physiological and ecological balance. If these changes take place within biogenetically short periods, species can not develop new strategies of adaptation and the self-regulating mechanism will fail.