A novel machine learning approach for assessing water quality using Daphnia swimming behavior

Simple SummaryNew types of pesticides are increasingly found in surface waters around the world. Little is known about how they interact in mixtures, and how these mixtures might then affect aquatic organisms at risk of exposure. We looked at how two new pesticides, chlorantraniliprole (CHL) and imidacloprid (IMI), affected a sensitive aquatic organism, Daphnia magna. We exposed Daphnia to surface waters known to be contaminated by agricultural runoff at two time points: during an extended dry period and after the first seasonal storm event. In surface waters, the concentrations of CHL, IMI, and other pesticides of concern increased after the storm event. Exposure to these waters caused Daphnia to be hypoactive, and their response to light varied with the concentration of surface water. We then exposed Daphnia to each chemical individually and then to mixtures of the two chemicals, at concentrations that occur in polluted waterways. Daphnia exposed to CHL and IMI mixtures were more active in response to light stimuli than the control group. Daphnia swimming behavior is a sensitive way to measure the biological effects of CHL, IMI, and surface waters. Pesticides with novel modes of action including neonicotinoids and anthranilic diamides are increasingly detected in global surface waters. Little is known about how these pesticides of concern interact in mixtures at environmentally relevant concentrations, a common exposure scenario in waterways impacted by pesticide pollution. We examined effects of chlorantraniliprole (CHL) and imidacloprid (IMI) on the sensitive invertebrate, Daphnia magna. Exposures were first performed using surface waters known to be contaminated by agricultural runoff. To evaluate the seasonal variation in chemical concentration and composition of surface waters, we tested surface water samples taken at two time points: during an extended dry period and after a first flush storm event. In surface waters, the concentrations of CHL, IMI, and other pesticides of concern increased after first flush, resulting in hypoactivity and dose-dependent photomotor responses. We then examined mortality and behavior following single and binary chemical mixtures of CHL and IMI. We detected inverse photomotor responses and some evidence of synergistic effects in binary mixture exposures. Taken together, this research demonstrates that CHL, IMI, and contaminated surface waters all cause abnormal swimming behavior in D. magna. Invertebrate swimming behavior is a sensitive endpoint for measuring the biological effects of environmental pesticides of concern.

Polystyrene microplastics weaken the predator-induced defenses of Daphnia magna: Evidences from the changes in morphology and behavior

Titanium dioxide nanoparticles (TiO2 NPs) have attracted considerable concerns due to the increasing production and widespread applications, while their influences on other co-existing pollutants in real environment are not well studied. In this paper, the colloidal stability of TiO2 NPs in the exposure medium was first evaluated, and then, the medium was modified so that TiO2 NP suspension remained stable over the exposure period. Finally, using the optimized exposure medium, the effects of cadmium (Cd) and lead (Pb) on Daphnia magna both in the absence and presence of TiO2 NPs were investigated. Results showed that 2 mg L−1 of TiO2 NPs was well dispersed in 1:20 diluted Elendt M7 medium without EDTA, and no immobility was observed. The presence of the nanoparticles increased the bioaccumulation and toxicity of Cd to the daphnias. On the contrary, while Pb bioaccumulation was enhanced by three to four times, toxicity of Pb was reduced in the presence of TiO2 NPs. The decreased toxicity of Pb was more likely attributed to the decreased bioavailability of free Pb ion due to adsorption and speciation change of Pb in the presence of TiO2 NPs. Additionally, surface-attached TiO2 NPs combined with adsorbed heavy metals caused adverse effects on daphnia swimming and molting behavior, which is supposed to lead to chronic toxicity.

We have been investigating how to use behavior controlled Daphnia as a living micromachine The Daphnia's control was done by applying their phototaxes. In this study, we developed underwater operation tool for Daphnia. We installed an operational tool called 'Y-Wing custom' to the Daphnia's back and investigated the vertical object transportation performance of the tool installed Daphnia. In the beginning of the development, the attached tool disturbed Daphnia's swimming, and the object transportation performance of the Daphnia with operational tool was not improved comparing to the Daphnia without any tool. After the improvement of the tool shape, we succeeded to move and drop a nylon ball on the shelf from the designated end point of the shelf by manually controlled Daphnia in the vertical plane pool.

Exposure to D2-like dopamine receptor agonists inhibits swimming in Daphnia magna

Daphnia swimming behaviour is controlled by a variety of external factors, including light, presence of food and predators. Temperature represents a key driver in the dynamics of Daphnia populations, as well as on their motion. In this study, we have investigated the behavioural adaptations of adult Daphnia pulicaria to two different temperatures, representative of the mean winter (3°C) and summer (22°C) temperatures to which these organisms are exposed to in the real environment. Video observations were conducted both in the presence and in the absence of light to investigate possible day/night modifications in the motion strategy. Analyses of mean speed, velocity power spectral density and trajectory fractal dimension point out specific adaptations that allow D. pulicaria to successfully adjust to the changing conditions of the environment. Independently of the light conditions, in cold waters D. pulicaria swim almost vertically with defined motional frequencies, likely to increase the encounter with food items diluted in the fluid. A similar behaviour is displayed by the animals at summertime temperatures in the presence of light; however, in this case the vertical swimming is coupled with the absence of peaks in the power spectra and might be exploited to avoid predators. In contrast, at 22°C in dark conditions D. pulicaria move horizontally with lateral motions to take advantage of possible patches of phytoplankton. This information sheds new light into the complex and dynamic adaptations of D. pulicaria in response to external stimuli.

Continuous monitoring of volatile organic compounds (VOC) in raw water is highly desirable for taste and odour management, but in most treatment plants this capacity is lacking. We used a bbe Daphnia toximeter installed in the Zurich water treatment plant to determine if Daphnia magna could be used to monitor odour compounds in source-water. Trace levels of two widely distributed biogenic VOCs in freshwater: P-cyclocitral and 2(E),4(E),7(Z)-decatrienal were added to the raw water inflow to chambers containing test animals and their behaviour was recorded using a high resolution camera. We observed that each compound elicited a marked short-term increase in Daphnia swimming velocity, but the effect was brief and an acclimation to the compounds was observed after a time period or with repeated additions. The results demonstrate that the toximeter has considerable potential as a tool to monitor certain VOCs in water, and that Daphnia perceive and react to 2(E),4(E),7(Z)-decatrienal and P-cyclocitral at concentrations between 2.5 and 25 microM.

Swimming in response to light change is considered the proximate mechanism underlying diel vertical migration. This behavioural mechanism is supposed to be tuned to the adaptive needs under natural conditions by the modifying influence of environmental variables, such as predator kairomones. We investigated to what extent fish kairomone level affects downward swimming in response to a continuous relative light intensity increase. At the higher kairomone levels Daphnia had significant higher displacement velocities. Thus, kairomone was perceived quantitatively and behaviour was altered correspondingly. Because the absolute difference in displacement velocity between treatments was small, we assumed that kairomone concentration could not explain much of the seasonal variability in diel vertical migration patterns in Lake Maarsseveen. Therefore, we hypothesised that besides swimming in response to relative changes in light intensity, other aspects of phototaxis were important also. The natural light intensity increase at early morning consists of a continuous increase in the rate of the relative light intensity change, which reach a maximum about 30–45 min before sunrise. After this maximum, the rates of the relative light intensity increase decrease again. Thus far, it was assumed that successive changes in light intensity acted independent on the swimming reaction of the daphnids. In this paper, we present results of experiments with Daphnia swimming in response to a combination of a continuous and an instantaneous increase in light intensity. A continuous relative light increase preceding an instantaneous increase in light intensity (step) enlarged the downward displacement velocity of Daphnia markedly. Hence, successive light stimuli did not act independently. With growing relative light increase rates preceding the step, the displacement velocity increased also. Moreover, the presence of fish kairomone further increased the velocity in response to the light change. Therefore, the rate of the relative change in light intensity is an incomplete description of the stimulus for diel vertical migration behaviour.

Abstract An analysis of digitized three-dimensional video records of free-swimming Daphnia pulex identified six measurements of swimming behavior that can be used to quantify individual behavioral responses to pesticides or natural chemical signals. Protocols are given for measuring the parameters that showed statistically significant changes in pesticide treatments. The most efficient experimental design would involve observing as many animals as possible, with one observation per animal. Parameters most likely to be useful in future studies are velocity, turning angle, upward and downward angles during hops, variance in vertical position, and hopping frequency. The parameters varied in usefulness, defined as the ratio of within-treatment to among-treatment variance (F ratios). Velocity was the most useful (i.e., had the highest F ratio); hopping frequency was the least useful. Daphnia exhibited three kinds of swimming behavior, as defined by eight parameters: (a) “spinning” (extreme and continuous escape response) to acutely toxic levels of Carbaryl (40 ppb); (b) “irritation” (an increase in escape-like behavior) to low levels of Carbaryl (1 ppb); and (c) “null” behavioral responses to Chaoborus-conditioned water, in which there was no detectable change in any measurement of swimming behavior. In predation trials, bluegill sunfish preferentially selected individuals showing “spinning” behavior. Results from this and other studies of Daphnia swimming behavior suggest a conservative-swimming hypothesis for understanding constraints on Daphnia swimming behavior.

Body length affects several aspects of the behavior of quietly swimming Daphnia pulex Swimming and sinking rates were measured at 0.033 s intervals during the 'hops' characteristic of Daphnia swimming behavior Larger animals swim faster, cover more distance, and produce more powerful swimming strokes. Larger Daphnia also sink faster, but the sinking rate scales as length to the 0 58 power, far lower than the power of 2 00 predicted by Stokes Law considerations. The number of hops s1 was independent of body size, although a theoretical analysis predicts hopping rate (antennal beat frequency) should increase as body length squared. Turning behavior, measured as the ratio of displacement to total distance, during 5 s, is also independent of body size Independence of several parameters of body motion and body size implies that factors other than simple mechanics affect Daphnia swimming behavior

Estimations of invertebrate predation parameters usually rely on behavioral observations and on feeding rates in single, arbitrary prey densities. In this study, predation parameters were estimated directly from functional response data. This type of analysis relies on many prey densities and therefore should lead to more widely applicable parameter values. Functional response curves of third—and fourth—instar Chaoborus americanus preying on five size—classes of Daphnia pulex in the laboratory were examined. Data for each size—class were fitted to Rogers' random predator equation, a modification of Holling's type II functional response equation. The data fit the model well. The parameters a' (instantaneous attack rate) and Th (handling time) were calculated for each prey size from these curves. Attack rate reached a maximum, indicating highest vulnerability, at an intermediate size. Deduced handling times were greater than simple observation would suggest and were highly correlated with prey dry mass, suggesting digestion as the primary component. Results of mixed—size—class experiments were compared to predictions based on the parameters from single—size—class experiments. The ratio of predation—caused mortality rates for prey size—classes was consistent with the predictions, suggesting that no active behavioral selection was occurring. Feeding rates in mixed—sized—class experiments were underestimated when experiments were run a month later than the single—size—class experiments during the 1st yr of this study. However, when single— and mixed—size—class experiments were run simultaneously during the 2nd yr, predictions were very close to observed feeding rates. This indicates the possibility that predator age and seasonal physiological changes affect functional response parameters. Attack rate increased with temperature, probably due to increased encounter rates as Daphnia swimming speed increased. Handling time decreased with increased temperature, probably due to increased digestive rate. The biological significance of Holling's parameters and those of other more behaviorally based models is discussed.