Computational characterization of behavioral response of medaka (Oryzias latipes) treated with diazinon

Automated software for counting and measuring Hyalella genus using artificial intelligence

Amphipods belonging to the Hyalella genus are macroinvertebrates that inhabit aquatic environments. They are of particular interest in areas such as limnology and ecotoxicology, where data on the number of Hyalella individuals and their allometric measurements are used to assess the environmental dynamics of aquatic ecosystems. In this study, we introduce HyACS, a software tool that uses a model developed with the YOLOv3's architecture to detect individuals, and digital image processing techniques to extract morphological metrics of the Hyalella genus. The software detects body metrics of length, arc length, maximum width, eccentricity, perimeter, and area of Hyalella individuals, using basic imaging capture equipment. The performance metrics indicate that the model developed can achieve high prediction levels, with an accuracy above 90% for the correct identification of individuals. It can perform up to four times faster than traditional visual counting methods and provide precise morphological measurements of Hyalella individuals, which may improve further studies of the species populations and enhance their use as bioindicators of water quality.

Silver nanoparticles adversely affect the swimming behavior of European Whitefish (Coregonus lavaretus) larvae within the low µg/L range

The aim of this study was to determine the effects of silver nanoparticles (AgNPs; speciation: NM-300 K) in the lab on the behavior of larvae in European Whitefish (Coregonus lavaretus), a relevant model species for temperate aquatic environments during alternating light and darkness phases. The behavioral parameters measured included activity, turning rate, and distance moved. C. lavaretus were exposed to AgNP at nominal concentrations of 0, 5, 15, 45, 135, or 405 µg/L (n = 33, each) and behavior was recorded using a custom-built tracking system equipped with light sources that reliably simulate light and darkness. The observed behavior was analyzed using generalized linear mixed models, which enabled reliable detection of AgNP-related movement patterns at 10-fold higher sensitivity compared to recently reported standard toxicological studies. Exposure to 45 µg/L AgNPs significantly resulted in hyperactive response patterns for both activity and turning rates after an illumination change from light to darkness suggesting that exposure to this compound triggered escape mechanisms and disorientation-like behaviors in C. lavaretus fish larvae. Even at 5 µg/L AgNPs some behavioral effects were detected, but further tests are required to assess their ecological relevance. Further, the behavior of fish larvae exposed to 135 µg/L AgNPs was comparable to the control for all test parameters, suggesting a triphasic dose response pattern. Data demonstrated the potential of combining generalized linear mixed models with behavioral investigations to detect adverse effects on aquatic species that might be overlooked using standard toxicological tests.

Real-time determination of water status upon simultaneous zebrafish exposure to sublethal concentrations of CuSO4

Water pollution from commonly occurring contaminants (metals, xenobiotics, etc.) is a serious global problem. Copper is a commonly occurring water contaminant. A variety of physiological and biological methods have been developed to monitor water quality. The assessment of biological responses is an effective method for identifying the harmful effects of contaminants on ecosystems. Fish is a highly recommended animal model in water quality monitoring. Swimming consistency (firmness) and respiratory metabolism (oxygen consumption rate, carbon dioxide excretion rate and respiratory quotient) are essential for fish to maintain body homeostasis toward coping with environmental stress. We exposed zebrafish to different concentrations (Treatment I-0.1 mg/L and Treatment II-1.58 mg/L) of CuSO₄. We have continuously quantified the strength of behavior (swimming consistency) and physiological (respiratory rates) biomarkers for ten days using an online monitoring system of swimming behavior and external respiration. Swimming consistency and respiratory rates of zebrafish (p<0.05) decreased in the CuSO₄-treated groups compared to the control group. Avoidance behavior has led to an endpoint behavior at copperiedus. The time-delayed toxic effect has resulted in CuSO₄ treatment groups. We checked for swimming consistency aberration on the artificial neural array, Self-organizing map (SOM). Circadian rhythms were influenced by prolonged exposure to CuSO₄ toxicity. A concentration- and duration-dependent behavior anomaly was noted in this study. Swimming behavior and respiratory metabolism patterns are sensitive non-invasive stress biomarkers for water quality monitoring studies.

Quantifying finer-scale behaviours using self-organising maps (SOMs) to link accelerometery signatures with behavioural patterns in free-roaming terrestrial animals

Collecting quantitative information on animal behaviours is difficult, especially from cryptic species or species that alter natural behaviours under observation. Using harness-mounted tri-axial accelerometers free-roaming domestic cats (Felis Catus) we developed a methodology that can precisely classify finer-scale behaviours. We further tested the effect of a prey-protector device designed to reduce prey capture. We aligned accelerometer traces collected at 50 Hz with video files (60 fps) and labelled 12 individual behaviours, then trained a supervised machine-learning algorithm using Kohonen super self-organising maps (SOM). The SOM was able to predict individual behaviours with a ~ 99.6% overall accuracy, which was slightly better than for random forest estimates using the same dataset (98.9%). There was a significant effect of sample size, with precision and sensitivity decreasing rapidly below 2000 1-s observations. We were also able to detect a behaviour specific reduction in the predictability when cats were fitted with the prey-protector device indicating it altered biomechanical gait. Our results can be applied in movement ecology, zoology and conservation, where habitat specific movement performance between predators or prey may be critical to managing species of conservation significance, or in veterinary and agricultural fields, where early detection of movement pathologies can improve animal welfare.

Analyzing the Response Behavior of Lumbriculus variegatus (Oligochaeta: Lumbriculidae) to Different Concentrations of Copper Sulfate Based on Line Body Shape Detection and a Recurrent Self-Organizing Map

Point detection (e.g., the centroid of the body) of species has been conducted in numerous studies. However, line detection (i.e., the line body shape) of elongated species has rarely been investigated under stressful conditions. We analyzed the line movements of an Oligochaeta Lumbriculus variegatus in response to treatments with a toxic chemical, copper sulfate, at low concentrations (0.01 mg/L and 0.1 mg/L). The automatic line-tracking system was devised to identify the movement of body segments (body length) and the movements of segments (i.e., the speed and angles between segments) were recorded before and after treatment. Total body length was shortened from 31.22 (±5.18) mm to 20.91 (±4.65) mm after the 0.1 mg/L treatment. The Shannon entropy index decreased from 0.44 (±0.1) to 0.28 (±0.08) after treatment. On the other hand, the body and movement segments did not significantly change after the 0.01 mg/L treatment. Sequential movements of test organisms were further analyzed with a recurrent self-organizing map (RSOM) to determine the pattern of time-series line movements. The RSOM made it feasible to classify sequential behaviors of indicator organisms and identify various continuous body movements under stressful conditions.

The effects of combinations of limited ration and diazinon exposure on acetylcholinesterase activity, growth and reproduction in Oryzias latipes, the Japanese medaka

Environmental contamination can negatively impact fish populations. In addition to acute toxicity leading to death, toxicants can reduce fish growth and lower reproduction. The potential for adverse population level effects of environmental contaminants are estimated to conduct risk assessments from laboratory toxicity tests that most often measure apical endpoints related to growth, survival and reproduction. The relationships between these effect endpoints are being evaluated to predict shifts in fish population demography better after exposure to environmental toxicants. Environmental contaminants can also affect fish populations indirectly by reducing prey biomass. However, estimating the magnitude of the combined effects of prey reduction and direct toxicity is difficult and rarely attempted. Here we describe a toxicity test designed to estimate the effect on Japanese medaka of both reduced food and chronic exposure to diazinon, an acetylcholinesterase inhibiting organophosphate pesticide. Fish were reared with limited food ration and/or diazinon exposure through a full life cycle to assess possible interactions between the two stressors in their effects on growth and reproduction. Diazinon exposure (10 or 20 μg/L), reduced ration (50% and 25% of ad libitum), or combinations of both lowered growth rates and reproductive output of Japanese medaka. In addition, growth and reproduction alone were modeled, and then various relationships between the two stressors (diazinon and ration) and how they relate to growth and reproduction were modeled.

Toxic responses of zebrafish (Danio rerio) to thallium and deltamethrin characterized in the electrocardiogram

The electrocardiogram (ECG) has been widely used to objectively address the physical condition as an index of stress. Though a numerous accounts of investigations on aquatic organisms' ECGs have been made, differentiation of ECG parameters in responding to specific toxic chemicals has not been extensively studied. In this research, it is hypothesized that zebrafish (Danio rerio) ECG parameters would differently respond to different types of pollutants, a heavy metal, thallium (Tl, 0.10 and 13.00 μg/L) and an organic chemical, deltamethrin (DM, 0.52 and 2.00 μg/L). Based on the SOM training and statistical analyses, QRS complex could be specified as an indicator of Tl stress, while QT interval might be used to evaluate DM stress. Pearson correlation analysis indicated that QRS complex and QT interval were significantly associated with Tl stress (r = 0.854, p = 0.0002) and DM stress (r = 0.792, p = 0.001), respectively. QRS complex and QT interval had the highest R², the minimum of SSE and the lowest AIC value in Tl and DM treatments, respectively. Bases on the current experimental results and previous reports, QRS complex and QT interval could be considered as a specific indicator of Tl and DM disturbances in the environment, respectively.

Behavior responses of zebrafish (Danio rerio) to aquatic environmental stresses in the characteristic of circadian rhythms

As behavior shows a distinct circadian rhythm, it is hypothesized that circadian rhythms based on zebrafish (Danio rerio) behavior responses could be affected by contaminants in this study, and then the behavior strength of zebrafish exposed to 0.005 mg/L Cadmium chloride (CdCl₂), 0.01 mg/L Dibasic Sodium Phosphate (Na₂HPO₄), 0.002 mg/L deltamethrin, and 0.003 mg/L atrazine for 6 days is used to illustrate the possibility of behavior circadian rhythms as an indicator in the environmental stress assessment. Statistical analysis with p < 0.01 shows that a clear difference between average values of BS during dark period (AVD) and those during light period (AVL) could be observed, and 24 h circadian rhythms do exist in zebrafish behavior responses. Both BS values and circadian rhythms of zebrafish can be affected in the aspect of periodicity with clear time delay, which were 1 h delay in CdCl₂, 4 h delay in Na₂HPO₄, 4 h delay in deltamethrin, and 1 h delay in atrazine. Behavior circadian rhythms were disturbed according to the repetitive cycles after autocorrelation analysis, and the toxic effects of different chemicals could be reflected by the profiles of the Self-Organizing Map (SOM), which indicated the circadian rhythm disorder in different degrees. These results deduced from the statistical analysis, autocorrelation and SOM strongly supported that circadian rhythms based on zebrafish BS could be used as an indicator in the environmental stress assessment.

The effects of continuous diazinon exposure on growth and reproduction in Japanese medaka using a modified Medaka Extended One Generation Reproduction Test (MEOGRT)

The Medaka Extended One Generation Reproduction Test (MEOGRT) is a Tier 2 test within U.S. Environmental Protection Agency's (USEPA) Endocrine Disruptor Screening Program (EDSP), designed to characterize the potential adverse effects to fish of exposure to chemical that can cause disruption of the endocrine system. The MEOGRT focuses primarily on adverse effects to reproduction while collecting information regarding effects on growth, survival, and endocrine-related endpoints. However, the risk assessment process for fish, as mandated by legislation such as the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) or the Toxic Substances Control Act (TSCA), could benefit from a more detailed assessment of effects on growth. Typically, fish growth data in support of risk assessment are obtained from full life-cycle tests or early life stage tests using the fathead minnow. As an alternative to these tests, a modified MEOGRT was conducted to assess the effects of diazinon on the various parameters measured in the MEOGRT. Diazinon is an organophosphate insecticide that is detected in the environment, and whose efficacy is a result of inhibition of the acetylcholine esterase enzyme at neuromuscular junctions and synapses of the nervous system. Diazinon (2.9, 5.2, 10.3, 19.8, and 40.2 μg/L) was tested with the MEOGRT protocol, and the lowest observable effect concentrations of 2.9 μg/L for fecundity and 5.2 μg/L for growth were determined. Additional growth measurements were added to the MEOGRT protocol to more robustly define growth rates and to determine the impact size has on reproductive performance. Fish size starting at the first measurement day (i.e. 21 days post-fertilization), and continuing through the duration of the test was reduced with exposure to 5.2 μg/L and higher, and asymptotic size predicted from growth modeling was reduced at 10.3 μg/L and higher. By simply adding non-destructive growth measurements at two additional time points, the MEOGRT provided enough data for the parameterization of growth models, which could be used to characterize the reproductive implications of growth impairment.

Zinc Chloride Exposure Inhibits Brain Acetylcholine Levels, Produces Neurotoxic Signatures, and Diminishes Memory and Motor Activities in Adult Zebrafish

In this study, we evaluated the acute (24, 48, 72, and 96 h) and chronic (21 days) adverse effects induced by low doses (0.1, 0.5, 1, and 1.5 mg/L) of zinc chloride (ZnCl₂) exposure in adult zebrafish by using behavioral endpoints like three-dimensional (3D) locomotion, passive avoidance, aggression, circadian rhythm, and predator avoidance tests. Also, brain tissues were dissected and subjected to analysis of multiple parameters related to oxidative stress, antioxidant responses, superoxide dismutase (SOD), neurotoxicity, and neurotransmitters. The results showed that ZnCl₂-exposed fishes displayed decreased locomotor behavior and impaired short-term memory, which caused an Alzheimer’s Disease (AD)-like syndrome. In addition, low concentrations of ZnCl₂ induced amyloid beta (amyloid β) and phosphorylated Tau (p-Tau) protein levels in brains. In addition, significant induction in oxidative stress indices (reactive oxygen species (ROS) and malondialdehyde (MDA)), reduction in antioxidant defense system (glutathione (GSH), GSH peroxidase (GSH-Px) and SOD) and changes in neurotransmitters were observed at low concentrations of ZnCl₂. Neurotoxic effects of ZnCl₂ were observed with significant inhibition of acetylcholine (ACh) activity when the exposure dose was higher than 1 ppm. Furthermore, we found that zinc, metallothionein (MT), and cortisol levels in brain were elevated compared to the control group. A significantly negative correlation was observed between memory and acetylcholinesterase (AChE) activity. In summary, these findings revealed that exposure to ZnCl₂ affected the behavior profile of zebrafish, and induced neurotoxicity which may be associated with damaged brain areas related to memory. Moreover, our ZnCl₂-induced zebrafish model may have potential for AD-associated research in the future.

Escherichia coli's water load affects zebrafish (Danio rerio) behavior

Traditional physico-chemical sensors are becoming an obsolete tool for environmental quality assessment. Biomonitoring techniques, such as biological early warning systems present the advantage of being sensitivity, fast, non-invasive and ecologically relevant. In this work, we applied a video tracking system, developed with zebrafish (Danio rerio), to detect microbiological contamination in water. Using the fishs' behavior response, the system was able to detect the presence of a non-pathogenic environmental strain of Escherichia coli, at three different levels of contamination: 600, 1800 and 5000 CFU/100 mL (colony forming units/100 mL). Data was collected during 50 min of exposure and analyzed with the artificial neural networks Self-organizing Map and Multi-layer Perceptron. The behavior of exposed fish was more erratic, with pronounced and rapid changes on movement direction and with significant less exploratory activity. The accuracy, sensitivity and specificity values regarding the detection capability (distinction between presence or absence of contamination) ranged from 89 to 100%. Regarding the classification capability (distinction between experimental conditions), the values ranged from 67 to 89%. This research may be a valuable contribution to improve water monitoring and management strategies, by taking as reference the effects on biosensors, without a biased anthropocentric perspective.

Aquatic Toxic Analysis by Monitoring Fish Behavior Using Computer Vision: A Recent Progress

Video tracking based biological early warning system achieved a great progress with advanced computer vision and machine learning methods. Ability of video tracking of multiple biological organisms has been largely improved in recent years. Video based behavioral monitoring has become a common tool for acquiring quantified behavioral data for aquatic risk assessment. Investigation of behavioral responses under chemical and environmental stress has been boosted by rapidly developed machine learning and artificial intelligence. In this paper, we introduce the fundamental of video tracking and present the pioneer works in precise tracking of a group of individuals in 2D and 3D space. Technical and practical issues suffered in video tracking are explained. Subsequently, the toxic analysis based on fish behavioral data is summarized. Frequently used computational methods and machine learning are explained with their applications in aquatic toxicity detection and abnormal pattern analysis. Finally, advantages of recent developed deep learning approach in toxic prediction are presented.

Analysis of zebrafish (Danio rerio) behavior in response to bacterial infection using a self-organizing map

BACKGROUND

Animal behavioral responses have been recently established as a suitable tool for detecting contaminants in the environment for risk assessment in situ. In this study, we observed movement behavior of zebrafish (Danio rerio) before and after infection with Edwardsiella tarda CK41 for 3 days until death.

METHODS

Infection status of zebrafish was confirmed through PCR and colonization assay as time progressed and lesion development in the tails of zebrafish was also examined. Movement behaviors in response to bacterial infection were patterned by self-organizing map (SOM) based on movement parameters, including speed (mm/s), acceleration (mm/s (2) ), stop duration (t), stop number (n), locomotory rate (mm/s), turning rate (rad/s), and meander (rad/mm).

RESULTS

According to SOM result, clusters were identified firstly according to time and secondly according to infection. Two movement patterns were observed in the early period of infection: one group with minimum turning rate and meander (i.e., stiff movement) and the other group with maximum strop number. Late infection was characterized by long stop duration.

CONCLUSION

SOM was suitable for extracting complex behavioral data and thus can serve as a referencing system for diagnosing disease development in order to reveal the mechanism of the infection process.

Video-tracking of zebrafish (Danio rerio) as a biological early warning system using two distinct artificial neural networks: Probabilistic neural network (PNN) and self-organizing map (SOM)

Biological early warning systems (BEWS) are becoming very important tools in ecotoxicological studies because they can detect changes in the behavior of organisms exposed to toxic substances. In this work, a video tracking system was fully developed to detect the presence of commercial bleach (NaOCl) in water in three different concentrations (0.0005%; 0.0010% and 0.0020% (v/v)) during one hour of exposure. Zebrafish was selected as the test organism because it is widely used in many different areas and studies. Two distinct statistical models were developed, using probabilistic neural network (PNN) and correspondence analysis associated with self-organizing map (SOM-CA). The diagnosis was based only in the analysis of a few behavioral components of the fish, namely: mean angular velocity, mean linear velocity, spatial dispersion, mean value of the X coordinate and mean value of the Y coordinate. Both models showed good results in their diagnosis capabilities. However, the overall performance (accuracy) was always superior in the PNN model. The worst result was with the SOM-CA model, at the lowest concentration (0.0005% v/v), achieving only 65% of correct diagnosis. The best result was with the PNN model, at the highest concentration (0.0020% v/v), achieving 94% of correct diagnosis.

Biological early warning system based on the responses of aquatic organisms to disturbances: a review

Aquatic ecosystems are subject to a number of anthropogenic disturbances, including environmental toxicants. The efficient monitoring of water resources is fundamental for effective management of water quality and aquatic ecosystems. Spot sampling and continuous water quality monitoring based on physicochemical factors are conducted to assess water quality. However, not all contaminants or synergistic and antagonistic toxic effects can be determined by solely analyzing the physicochemical factors. Thus, various biotests have been developed using long-term and automatic observation studies based on the ability of the aquatic organisms to continuously sense a wide range of pollutants. In addition, a biological early warning system (BEWS) has been developed based on the response behaviors of organisms to continuously detect a wide range of pollutants for effective water quality monitoring and management. However, large amounts of data exhibiting non-linearity and individual behavioral variation are continuously accumulated over long-term and continuous behavioral monitoring studies. Thus, appropriate mathematical and computational data analyses are necessary to manage and interpret such large datasets. Here, we review the development and application of BEWS by using various groups of organisms and the computational methods used to process the behavioral monitoring data.

The stepwise behavioral responses: behavioral adjustment of the Chinese rare minnow (Gobiocypris rarus) in the exposure of carbamate pesticides

In order to illustrate the behavioral regulation in environmental stress, the behavioral responses of the Chinese rare minnow (Gobiocypris rarus) to arprocarb, carbofuran, and oxamyl were analyzed with an online monitoring system. The Self-Organizing Map (SOM) was used to define the patterns of the behavioral data obtained from treatments at concentrations of 0.1 toxic unit (TU), 1 TU, 2 TU, 5 TU, 10 TU, and 20 TU and a control. In certain cases, differences among the carbamate pesticides (CPs) tested were observed. The profiles of behavioral strength (BS) in SOM varied according to the concentration used. The time of the first significant decrease of the BS varied inversely with the CP concentrations. The results suggested that the behavioral regulation in the stepwise behavioral responses (SBR) was evident. The primary movement behaviors shown by the SBR model included no effect, stimulation, acclimation, adjustment (readjustment), and toxic effect, especially at the lower concentrations. However, higher stress (10 TU and 20 TU) might limit the function of the behavioral adjustment produced by the intrinsic response mechanisms. It was concluded that SBR, which were affected by both the concentration and the exposure time, could be used as a suitable indicator in the ecotoxicological risk assessment of CPs.

Alterations in social behavior of Japanese medaka (Oryzias latipes) in response to sublethal chlorpyrifos exposure

The behavioral and biochemical responses of Japanese medaka (Oryzias latipes) to acute and subacute (sublethal) levels of chlorpyrifos were studied. In the acute exposure test, medaka were exposed to 0.018, 0.055, 0.166, or 0.500 mg L(-1) chlorpyrifos for 4 d. As a result, fish showed hypoactivity compared to the control (at 0.018, 0.055, and 0.166 mg L(-1), swimming speeds were 55.6%, 39.0%, and 27.3% those of the control), Brain acetylcholinesterase activity and swimming speed were significantly correlated. In the subacute toxicity test, medaka were exposed to 0.012 mg L(-1) chlorpyrifos (10% of LC(50)) for 8 d. On day 4, there were no significant differences in behavioral and biochemical endpoints in exposed fish as compared to the control. On day 8, exposed fish became hyperactive, and the swimming speed of the social group increased to 2 times that of the control, whereas acetylcholinesterase activity was decreased to 68% that of the control. In addition, fish exhibited significant alterations in social behavior (schooling duration increased to 2.6 times and solitary duration decreased to 28% that of the control). Our findings clearly demonstrate a subacute effect of chlorpyrifos on the social behavior of medaka, which may pose a risk at population level because of the disturbance of social behavior. In addition, the recorded behavioral alterations may provide a useful tool for assessing the toxicity of organophosphorous pesticides to aquatic organisms.

Evidence for the Stepwise Behavioral Response Model (SBRM): the effects of Carbamate Pesticides on medaka (Oryzias latipes) in an online monitoring system

The Stepwise Behavioral Response Model (SBRM), which is a conceptual model, postulated that an organism displays a time-dependent sequence of compensatory Stepwise Behavioral Response (SBR) during exposure to pollutants above their respective thresholds of resistance. In order to prove the model, in this study, the behavioral responses (BRs) of medaka (Oryzias latipes) in the exposure of Arprocarb (A), Carbofuran (C) and Methomyl (M) were analyzed in an online monitoring system (OMS). The Self-Organizing Map (SOM) was utilized for patterning the obtained behavioral data in 0.1 TU (Toxic Unit), 1 TU, 2 TU, 5 TU, 10 TU and 20 TU treatments with control. Some differences among different Carbamate Pesticides (CPs) were observed in different concentrations and the profiles of behavior strength (BS) on SOM were variable depending upon levels of concentration. The time of the first significant decrease of BS (SD-BS) was in inverse ratio to the CP concentrations. Movement behavior showed by medaka mainly included No effect, Stimulation, Acclimation, Adjustment (Readjustment) and Toxic effect, which proved SBRM as a time-dependence model based on the time series BS data. Meanwhile, it was found that SBRM showed evident stress-dependence. Therefore, it was concluded that medaka SBR was both stress-dependent and time-dependent, which supported and developed SBRM, and data mining by SOM could be efficiently used to illustrate the behavioral processes and to monitor toxic chemicals in the environment.

Differences in spatio-temporal behavior of zebrafish in the open tank paradigm after a short-period confinement into dark and bright environments

The open tank paradigm, also known as novel tank diving test, is a protocol used to evaluate the zebrafish behavior. Several characteristics have been described for this species, including scototaxis, which is the natural preference for dark environments in detriment of bright ones. However, there is no evidence regarding the influence of “natural stimuli” in zebrafish subjected to novelty-based paradigms. In this report, we evaluated the spatio-temporal exploratory activity of the short-fin zebrafish phenotype in the open tank after a short-period confinement into dark/bright environments. A total of 44 animals were individually confined during a 10-min single session into one of three environments: black-painted, white-painted, and transparent cylinders (dark, bright, and transparent groups). Fish were further subjected to the novel tank test and their exploratory profile was recorded during a 15-min trial. The results demonstrated that zebrafish increased their vertical exploratory activity during the first 6-min, where the bright group spent more time and travelled a higher distance in the top area. Interestingly, all behavioral parameters measured for the dark group were similar to the transparent one. These data were confirmed by automated analysis of track and occupancy plots and also demonstrated that zebrafish display a classical homebase formation in the bottom area of the tank. A detailed spatio-temporal study of zebrafish exploratory behavior and the construction of representative ethograms showed that the experimental groups presented significant differences in the first 3-min vs. last 3-min of test. Although the main factors involved in these behavioral responses still remain ambiguous and require further investigation, the current report describes an alternative methodological approach for assessing the zebrafish behavior after a forced exposure to different environments. Additionally, the analysis of ethologically-relevant patterns across time could be a potential phenotyping tool to evaluate the zebrafish exploratory profile in the open tank task.

Three-dimensional neurophenotyping of adult zebrafish behavior

The use of adult zebrafish (Danio rerio) in neurobehavioral research is rapidly expanding. The present large-scale study applied the newest video-tracking and data-mining technologies to further examine zebrafish anxiety-like phenotypes. Here, we generated temporal and spatial three-dimensional (3D) reconstructions of zebrafish locomotion, globally assessed behavioral profiles evoked by several anxiogenic and anxiolytic manipulations, mapped individual endpoints to 3D reconstructions, and performed cluster analysis to reconfirm behavioral correlates of high- and low-anxiety states. The application of 3D swim path reconstructions consolidates behavioral data (while increasing data density) and provides a novel way to examine and represent zebrafish behavior. It also enables rapid optimization of video tracking settings to improve quantification of automated parameters, and suggests that spatiotemporal organization of zebrafish swimming activity can be affected by various experimental manipulations in a manner predicted by their anxiolytic or anxiogenic nature. Our approach markedly enhances the power of zebrafish behavioral analyses, providing innovative framework for high-throughput 3D phenotyping of adult zebrafish behavior.

Use of medaka in toxicity testing

Small aquarium fishes are increasingly used as animal models, and one of these, the Japanese Medaka (Oryzias latipes), is frequently utilized for toxicity testing. While these vertebrates have many similarities with their terrestrial counterparts, there are differences that must be considered if these organisms are to be used to their highest potential. Commonly, testing may employ either the developing embryo or adults; both are easy to use and work with. To illustrate the utility and breadth of toxicity testing possible using medaka fish, we present protocols for assessing neurotoxicity in developing embryos, evaluating toxicant effects on sexual phenotype after treatment with endocrine-disrupting chemicals by sexual genotyping, and measuring hepatotoxicity in adult fish after treatment with a model hepatotoxicant. The methods run the gamut from immunohistology through PCR to basic histological techniques.

What do artificial neural networks tell us about the genetic structure of populations? The example of European pig populations

General and genetic statistical methods are commonly used to deal with microsatellite data (highly variable neutral genetic markers). In this paper, the self-organizing map (SOM) that belongs to the unsupervised artificial neural networks (ANNs) was applied to analyse the structure of 58 European and two Chinese pig populations (Sus scrofa) including commercial lines, local breeds and cosmopolitan breeds. Results were compared with other unsupervised classification or ordination methods such as factorial correspondence analysis, hierarchical clustering from an allele sharing distance and the Bayesian genetic model and with principal components analysis and neighbour joining from allelic frequencies and genetic distances between populations. Like other methods, SOMs were able to classify individuals according to their breed origin and to visualize similarities between breeds. They provided additional information on the within- and between-population diversity, allowed differences between similar populations to be highlighted and helped differentiate different groups of populations.

The early warning of aquatic organophosphorus pesticide contamination by on-line monitoring behavioral changes of Daphnia magna

In this paper, the movement behavior of Daphnia magna was studied as a bio-indicator of organophosphorous pesticide (OP) contamination, using an on-line bio-monitoring method, the Multispecies Freshwater Biomonitor. A static test of acute toxicity test revealed the 24-h and 48-h LC(50) values (95% confidence limit) for Daphnia magna to be respectively 0.45 microg/l and 0.21 microg/l for dipterex 3.80 microg/l and 0.90 microg/l for malathion, and 1.25 microg/l and 0.38 microg/l for parathion. The behavior strength of Daphnia magna was a sensitive indicator of sublethal OP stress and resulted in significant concentration-response relationships for the three OPs. Increasing OP concentration will result in more intensive behavioral responses of Daphnia magna and shorter response time, which could be described by the Stepwise Stress Model (SSM). Therefore movement behavior can be effectively applied in early warning of environment quality by on-line bio-monitoring. The intensive changes in behavior strength of Daphnia magna over a short time follow the SSM concept and can be used as an indicator of early stress response to OP accidental contamination.