Average Swimming Speed Research Articles

Proteomic study on the damage of learning and memory ability of rat offspring caused by chronic stress during pregnancy

Objective: To study the differential protein and signal pathway related to the impairment of learning and memory ability of offspring caused by chronic stress during pregnancy and explore the possible mechanism. Methods: From July to October 2019, sixteen SPF free female SD rats aged 80-90 days, weighing (200±20) g. Twelve SPF grade male SD rats aged 90-100 days, weighing (220±20) g. After a week of adaptive feeding, the female rats were randomly divided into control group and model group (8 rats in each group) , male rats were divided into control mating group (n=8) and model mating group (n=4) . Chronic unpredictable mild stress (CUMS) model was established and stimulated continuously for 21 days. One day before stress, the first, seventh, fourteenth and 21th day after stress, the blood was collected from the inner canthus vein of the female rats, and the content of corticosterone was determined. Morris water maze test was used to detect the spatial learning and memory ability of offspring rats. The morphological changes of hippocampus were observed by HE and Nissl staining. The proteomic correlation analysis of offspring rats' hippocampus was performed by isobaric tags for relative and absolute quantification (iTRAQ) technique. Results: Compared with the control group, the content of plasma corticosterone in the model group was significantly higher (F=7.717, P<0.05) , and the model was successfully established. In Morris water maze test, compared with the control offspring group, the escape latency was longer, the average swimming speed was lower, the number of crossing platform was less, and the target quadrant run was shorter in the model offspring group (P<0.05) . The pathological results showed that the morphology of cells in the hippocampal tissue of the model offspring group was irregular, the number of neurons was small, Nissl body was unevenly distributed, the volume was small and the number was small. Mass spectrometry analysis showed that a total of 5065 proteins were screened out in the two offspring groups, and 26 proteins were differentially expressed (P<0.05) , of which 19 proteins were up-regulated and 7 proteins were down regulated. The differential proteins were mainly involved in 23 biological processes, 14 cellular components and 9 molecular functions. Kyoto Encyclopedia of genes and genomes (KEGG) enrichment analysis showed that 57 pathways were enriched, of which 8 signaling pathways were significantly enriched (P<0.05) . There were 5 signaling pathways that might be involved in the impairment of learning and memory ability of offspring, including neuroactive ligand receptor interaction, cGMP-PKG signaling pathway, adhesion and connection, adhesion and connection FoxO signaling pathway and Notch signaling pathway, mainly including tyrosine protein kinase receptor, tyrosine kinase receptor and Notch signaling pathway, and α2A adrenergic receptor, cGMP dependent protein kinase and other differential proteins may be involved in the injury process. Conclusion: The damage of learning and memory ability of offspring may be caused by chronic stress during pregnancy rats. The enriched signal pathway and key differential proteins of proteomics may play an important role in the process of damage.

Investigation of Environmentally Dependent Movement of Bottlenose Dolphins (Tursiops truncatus)

How environmental features (e.g., people, enrichment, or other animals) affect movement is an important element for the study of animal behavior, biomechanics, and welfare. Here we present a stationary overhead camera-based persistent monitoring framework for the investigation of bottlenose dolphin (Tursiops truncatus) response to environmental stimuli. Mask R-CNN, a convolutional neural network architecture, was trained to automatically detect 3 object types in the environment: dolphins, people, and enrichment floats that were introduced to stimulate and engage the animals. Detected objects within each video frame were linked together to create track segments across frames. The animals’ tracks were used to parameterize their response to the presence of environmental stimuli. We collected and analyzed data from 24 sessions from bottlenose dolphins in a managed lagoon environment. The seasons had an average duration of 1 h and around half of them had enrichment (42%) while the rest (58%) did not. People were visible in the environment for 18.8% of the total time (∼4.5 h), more often when enrichment was present (∼3 h) than without (∼1.5 h). When neither enrichment nor people were present, the animals swam at an average speed of 1.2 m/s. When enrichment was added to the lagoon, average swimming speed decreased to 1.0 m/s and the animals spent more time moving at slow speeds around the enrichment. Animals’ engagement with the enrichment also decreased over time. These results indicate that the presence of enrichment and people in, or around, the environment attracts the animals, influencing habitat use and movement patterns as a result. This work demonstrates the ability of the proposed framework for the quantification and persistent monitoring of bottlenose dolphins’ movement, and will enable new studies to investigate individual and group animal locomotion and behavior.

Coral mucus rapidly induces chemokinesis and genome-wide transcriptional shifts toward early pathogenesis in a bacterial coral pathogen

Elevated seawater temperatures have contributed to the rise of coral disease mediated by bacterial pathogens, such as the globally distributed Vibrio coralliilyticus, which utilizes coral mucus as a chemical cue to locate stressed corals. However, the physiological events in the pathogens that follow their entry into the coral host environment remain unknown. Here, we present simultaneous measurements of the behavioral and transcriptional responses of V. coralliilyticus BAA-450 incubated in coral mucus. Video microscopy revealed a strong and rapid chemokinetic behavioral response by the pathogen, characterized by a two-fold increase in average swimming speed within 6 min of coral mucus exposure. RNA sequencing showed that this bacterial behavior was accompanied by an equally rapid differential expression of 53% of the genes in the V. coralliilyticus genome. Specifically, transcript abundance 10 min after mucus exposure showed upregulation of genes involved in quorum sensing, biofilm formation, and nutrient metabolism, and downregulation of flagella synthesis and chemotaxis genes. After 60 min, we observed upregulation of genes associated with virulence, including zinc metalloproteases responsible for causing coral tissue damage and algal symbiont photoinactivation, and secretion systems that may export toxins. Together, our results suggest that V. coralliilyticus employs a suite of behavioral and transcriptional responses to rapidly shift into a distinct infection mode within minutes of exposure to the coral microenvironment.

Quantitative Tools for Phenotype‐Based Drug Discovery in Zebrafish Models of Neurological Disease

Objective Transgenic zebrafish expressing human Tau protein in neurons develop rapid-onset motor phenotypes; the aim of the present work was to optimize quantitative analysis of complex datasets from high-throughput neurobehavioral assays, to facilitate identification of small molecules that rescue Tau-dependent neurological phenotypes in unbiased chemical screens. Hypothesis Analysis of multifactorial neurobehavioral data using principal component analysis (PCA) will enhance detection of phenotypic rescue and thereby increase the throughput and reliability of a chemical modifier assay. Methods Motor assays were carried out in 96-well plates, one zebrafish per well. Swimming movements evoked by changes in ambient illumination were measured using our published MATLAB program LSRtrack. The resulting dataset includes x, y coordinates of the zebrafish centroid in each frame of the video. A phenotypic profile for each zebrafish was generated, consisting of: mean swimming speed in the dark; mean swimming speed in the light; difference between light and dark swimming speed; acceleration in the dark; acceleration in the light; change in speed at dark-light and light-dark transitions; % time motile; and average contiguous rest and active periods. Since individual zebrafish responses are too variable to be useful as a screening tool, data from the control and Tau groups were separated and then averaged in randomly allocated groups of predetermined size. Each characteristic was analyzed statistically for separation between control and Tau zebrafish over a range of group sizes. Variables with the highest Z-factor were selected to create a PCA. Utility of the PCA for future screens was further analyzed using Z-factor analysis. Results At 8 zebrafish per group, there were statistically significant differences between control and Tau zebrafish for all measured characteristics except for mean active duration. Average swimming speed in the dark and % time motile were the parameters that allowed most reliable separation of control and Tau zebrafish, with individual Z-factors of 0.14 ± 0.01 and 0.12 ± 0.01, respectively. Combining these two parameters in a PCA produced a resultant Z-factor greater than the individual components at 0.18 ± 0.01, with a group size of 8 (with 1,000 iterations of random grouping). Conclusions The phenotypic profile describes the neurobehavioral changes in Tau transgenic zebrafish more completely than single-parameter measurements. In addition, compiling components of the phenotype into a PCA improved the assays metrics. The best single-parameter assay for this transgenic line requires a group size of 12 to achieve a useful Z-factor for screening, allowing 6 compounds plus controls to be evaluated on each 96-well plate. With the new PCA approach, screening is carried out in groups of 8 zebrafish, thereby expanding the assay throughout to 10 compounds per plate, a gain of 67%.

Acute and chronic behavioral effects of kelp gull micropredation on southern right whale mother-calf pairs off Península Valdés, Argentina

Kelp gullsLarus dominicanus(KG) feed on the skin and blubber of living southern right whalesEubalaena australis(SRWs) off Península Valdés (PV), Argentina. The whales respond strongly to KG micropredation by changing their immediate (acute) behavior during attacks and their overall (chronic) surfacing pattern and body posture to minimize gull exposure. The energetic and large-scale behavioral consequences of these attacks are unknown. To address this knowledge gap, we quantified the effect size of both acute (during attacks) and chronic (not during attacks) responses by comparing the respiration rates, swim speed, and nursing behavior of PV SRWs to undisturbed (control) SRW mother-calf pairs in Head of Bight, Australia, using unmanned aerial vehicle focal follows. Even when gulls were not attacking, PV SRW mothers and calves demonstrated ~50 and ~25% higher respiration rates, respectively, than whales in Australia. During attacks, PV calf respiration rates increased by an additional 10%. PV SRW mothers also frequently (&gt;76% of respirations) exhibited irregular breathing postures, causing the whales to potentially expend extra energy by working against their natural buoyancy. Despite no significant increase in average maternal swim speed, 76 and 90% of gull attacks elicited strong behavioral reactions from mothers and calves, respectively. Overall, PV calves spent less time nursing during individual bouts compared to those in Australia but entered suckling position more frequently. Furthermore, kelp gulls seemed to show a preference for attacking previously wounded calves and at a higher rate. These chronic and acute behavioral effects may carry energetic costs, which could have long-term consequences for SRW survival and reproduction.

Effect of Long-time Postnatal Exposure to Sevoflurane on Causing Attention-deficit/Hyperactivity Disorder in Rats

To investigate whether long-term exposure to inhaled sevoflurane, a volatile anesthetic, causes abnormal activities and memory impairment related to attention-deficit/hyperactivity disorder (ADHD) in neonatal rats. On postnatal day 5 (P5), Sprague-Dawley rats were randomly assigned to two sevoflurane subgroups and two control subgroups and underwent experimental intervention. The two sevoflurane (SEVO) subgroups were exposed to 3% sevoflurane for 2 h and 4 h respectively, while the two control subgroups were given pure oxygen for the same amount and duration. Behavioral tests, including open-field test (OFT), five-choice serial reaction time task (5-CSRTT), fear-conditioning (FC) and Morris water maze (MWM), were applied to evaluate changes in cognition, memory, anxiety and ADHD-related behavioral changes in the rats in adolescence (-P25) and in adulthood (-P65). In OFT, the SEVO 2 h and SEVO 4 h subgroups displayed activity level and exploratory behaviors similar to those of the control subgroups on P21 and P61, with no statistically significant difference identified in the data. 5-CSRTT results on P25 and P65 indicated no statistically significant difference between the SEVO subgroups and the control subgroups in regard to ADHD-related abnormal behaviors, including number of immature reaction, rate of correct response and omission rate. In the FC experiment, SEVO 4 h group had a shorter freezing period and longer period of freezing latency ( P=0.029) in comparison to the control groups. The results of the MWM test showed that the escape latency period of rats in the SEVO 4 h group was significantly prolonged on the second day and the third day, compared to the control groups ( P<0.05). The average swimming speed of SEVO groups did no exhibit any statistically significant difference on P69 or P76. The time the SEVO 4 h group spent in the target quadrant was significantly shorter than that of the control group ( P=0.039) and percentage of distance traveled in the target quadrant was significantly reduced compared to that the control group ( P=0.048). The findings suggest that four hours of inhaled sevoflurane exposure in neonate rats may cause memory impairment, but does no increase risks for ADHD-related abnormal activities.

Pacing and Hazard Score of Elite Open Water Swimmers During a 5-km Indoor Pool Race.

The sensation of fatigue experienced at a certain point of the race is an important factor in the regulation of pacing. The rating of perceived exertion (RPE) is considered one of the main mediators utilized by athletes to modify pacing. The aim was to analyze the relationship between pacing and RPE of elite open water swimmers during national indoor pool championships. A total of 17 elite open water swimmers (males, n = 9; females, n = 8) agreed to provide RPE every 500m during the finals of the national championships 5-km indoor pool race. Time splits, stroke rate, and RPE were collected every 500m. The Hazard score was calculated by multiplying the momentary RPE by the remaining fraction of the race. Athletes were placed in one of two categories: medalists or nonmedalists. For all variables, separate mixed analysis of variances (P ≤ .05) with repeated measures were used considering the splits (ie,every 500m) as within-subjects factor and the groups (ie,medalists and nonmedalists) as between-subjects factor. Average swimming speed showed a significant main effect for split for both males and females (P < .001). A significant interaction was observed between average swimming speed and groups for females (P = .032). RPE increased in both groups (P < .001) with no difference observed between groups. However, the female nonmedalists showed a disproportionate nonlinear increase in RPE (5.20 [2.31]) halfway through the event that corresponded to the point where they started significantly decreasing speed. The results of the present study show different pacing strategies adopted by medalists and nonmedalists despite a similar RPE.

Flagellar arrangements in elongated peritrichous bacteria: bundle formation and swimming properties

The surface distribution of flagella in peritrichous bacterial cells has been traditionally assumed to be random. Recently, the presence of a regular grid-like pattern of basal bodies has been suggested. Experimentally, the manipulation of the anchoring points of flagella in the cell membrane is difficult, and thus, elucidation of the consequences of a particular pattern on bacterial locomotion is challenging. We analyze the bundle formation process and swimming properties of Bacillus subtilis-like cells considering random, helical, and ring-like arrangements of flagella by means of mesoscale hydrodynamics simulations. Helical and ring patterns preferentially yield configurations with a single bundle, whereas configurations with no clear bundles are most likely for random anchoring. For any type of pattern, there is an almost equally low probability to form V-shaped bundle configurations with at least two bundles. Variation of the flagellum length yields a clear preference for a single major bundle in helical and ring patterns as soon as the flagellum length exceeds the body length. The average swimming speed of cells with a single or two bundles is rather similar, and approximately 50% larger than that of cells of other types of flagellar organization. Considering the various anchoring patterns, rings yield the smallest average swimming speed independent of the type of bundle, followed by helical arrangements, and largest speeds are observed for random anchoring. Hence, a regular pattern provides no advantage in terms of swimming speed compared to random anchoring of flagella, but yields more likely single-bundle configurations.Graphic abstract

Stochastic microswimming model of ribosome motion on the polysome.

In this work we assume that the ribosome propels itself during the translocation step of the translation process of protein synthesis by running a cycle of stochastically generated conformational changes involving its two subunits. This cycle includes only two experimentally found ribosome shape changes. The main result is an analytic expression for ribosome's average swimming speed on a polysome, where the ribosome is in the presence of other ribosomes. Relevant geometric parameters of ribosome deformations are calculated first by solving a deterministic problem where the ribosome runs a cycle of prescribed conformational changes. The method of reflections and pairwise additivity are used to obtain the stresses and forces needed to apply the multiparticle reciprocal theorem. Ribosome's average velocity when it runs the corresponding stochastic cycle of deformations is calculated assuming independence among the conformational cycles of different ribosomes on the polysome. The results obtained show that swimming in tandem on the polysome allows the ribosome to reach any typical subcellular speed with deformations whose amplitude is of a smaller size than when it swims alone in the fluid. Also, the flow organized by its swimming stroke becomes more determinant for its motion than random diffusion, compared to the solitary ribosome.

入侵性红耳滑龟与土著乌龟幼体游泳、翻身及心率表现的差异

为检验入侵性龟类是否在某些功能表现上较土著龟类具显著优势，将相同孵化环境中孵出的红耳滑龟和乌龟幼体在不同测试温度下测定其运动（游泳和翻身）和心率表现。结果显示：所检测的两种龟幼体功能指标均随测试温度的变化而变化；红耳滑龟幼体比乌龟幼体具有较快的游泳速度和心率，但较慢的翻身速度。此外，通过比较来自不同养殖群体的两种龟幼体发现：低纬度的海口养殖群个体比高纬度的海宁养殖群个体具有较快的心率、较好的运动表现。结合已发表的临界高低温数据对不同指标构建热功能曲线发现：红耳滑龟幼体游泳速度的热表现宽度大于乌龟幼体，翻身反应的热表现宽度反而较小；海宁养殖群的游泳速度和翻身反应的热表现宽度大于海口养殖群个体。表明：较强游泳能力及能在较宽的热范围内实现较好的游泳表现、较高代谢水平可能有助于入侵性红耳滑龟在新环境中快速扩散、与其它物种竞争取胜并实现其成功入侵。红耳滑龟未表现出较快的翻身速度可能与因其相对较扁平的体型而导致的翻身较难有关。;The invasive species are believed to perform better than native species in many aspects of physiology and behavior. Thermal physiological performance, one of the most crucial traits potentially determining the invasion success of alien species, has only been investigated experimentally in a few comparative studies of invasive and native species.In order to assess the superiority of some functional performances in invasive turtles over native ones, we incubated 160 eggs of Trachemys scripta elegans and Mauremys reevesii from two different cultured cohorts (Haikou-a low-latitude site and Haining-a high-latitude site, 40 eggs from each cultured cohort of both species) under an identical laboratory condition[(29±1)℃, -220 kPa substrate water potential], and randomly selected 80 hatchlings (20 individuals from each cultured cohort of both species) to measure their locomotor performances (swimming speed and righting time) and heart rate at seven different test temperatures (16, 20, 24, 28, 32, 36 and 40℃). A laterally positioned digital video camera was used to record the swimming performance of each turtle in a racetrack with 10 cm water depth in the swimming tests, while a perpendicularly positioned camera was used to record the righting performance of each turtle in an open box in the righting tests. Videoclips were examined later for the average swimming speed over 30 cm, and righting time. An infrared heart rate monitor was used to measure the heart rate (beat per minute) of each turtle. Test temperature significantly affected swimming speed, righting time, and heart rate in hatchlings of both turtle species. T. scripta elegans hatchlings appeared to have a greater swimming speed and heart rate, but needed more time to right themselves than M. reevesii hatchlings. Individuals from the Haikou cohort had a greater swimming speed, heart rate, and shorter righting time than those from the Haining cohort. We used the curve-fitting procedure of TableCurve 2D to construct thermal performance curves (TPCs) based on the exponentially modified Gaussian model for each locomotor and physiological variable, and then extracted two parameters[the maximal performance (P_m) and thermal performance breadth at 80% level of maximal performance (B₈₀)] from each constructed TPC. Similarly, T. scripta elegans hatchlings had a higher P_m for swimming speed and heart rate, but lower P_m for the reciprocal of righting time than M. reevesii hatchlings; individuals from the Haikou cohort had a higher P_m for swimming speed, heart rate and reciprocal of righting time than those from the Haining cohort. T. scripta elegans hatchlings had a wider B₈₀ for swimming speed than M. reevesii hatchlings, but not for heart rate and reciprocal of righting time;individuals from the Haikou cohort had narrower B80 for swimming speed and reciprocal of righting time than those from the Haining cohort. These results probably indicated that T. scripta elegans had better locomotor and physiological performances (e.g., faster swimming speed and greater thermal plasticity) than M. reevesii, which might contribute to its invasive success in a novel environment. Compared with M. reevesii hatchlings, T. scripta elegans hatchlings righted themselves more slowly, probably due to their more flattened body shape.

Time-, dose- and transgenerational effects of fluoxetine on the behavioural responses of zebrafish to a conspecific alarm substance.

Despite publication of numerous of papers, the effects of fluoxetine on fish behaviour remains mired in controversy and contradiction. One reason for this controversy is that fluoxetine displays distinct and opposing acute and chronic effects. A second reason is that most studies have been limited to two or at the most three concentrations. To address these deficiencies we exposed adult zebrafish, both single females and shoals consisting of one male and two females, to seven fluoxetine concentrations, ranging from 5ng/L to 5μg/L and measured their swimming behaviour, and response to a conspecific alarm substance (CAS) at seven, 14 and 28 days. We also measured the light startle response of unexposed F1 larvae at days seven and 28 post-hatch and the response to CAS at day 28. On day 7 fluoxetine decreased swimming speed at concentrations ≥500ng/L. After addition of CAS fish exposed to 5, 500 and 1000 ng/L decreased swimming, while fish exposed to 10, 500 and 1000ng/L significantly increased time motionless. On day 14 only fish exposed to 50 ng/L were significantly slower than controls before addition of CAS, but afterwards fish exposed to 5, 50, 1000 and 5000 ng/L showed significant differences from controls. On day 28 fish exposed to 50 and 5000ng/L had slower average swimming speeds than controls before addition of CAS. After addition all fish except controls and those exposed to 500ng/L showed decreased average speed. At seven days post-hatch, F1 larvae whose parents were exposed to 100ng/L showed significantly higher activity than controls and those exposed to 500ng/L fluoxetine showed lower activity in the light startle response. This study shows that the effects of fluoxetine vary with time and also in a non-monotonic manner. We suggest that the complex nature of the serotonergic system with multilateral effects at the genomic, biochemical and physiological levels interacting with environmental stimuli result in non-linear dose-response behavioural patterns.

Environmental and Biological Factors Influencing Dispersal of Neonate Leatherback Turtles (Dermochelys coriacea) From an Endangered Costa Rican Nesting Population

Quantifying early life movements is essential to understanding migratory pathways and habitat use that can impact individuals’ success later in life. To gauge how neonatal movements set the stage for later habitat use, we tracked neonate leatherback turtles (n=94) with acoustic tags from Pacuare, Costa Rica, in 2016 and 2018. We analyzed movements using a first passage time analysis and random walk models, the results of which indicated neonates followed a fixed compass direction as they traveled away from shore and that strong currents in these areas resulted in advection. We combined the tracking data with concurrent environmental variables in a generalized additive mixed model framework. Our results showed the south-east current flow in this area has spatial and temporal structure that was not driven by the tidal current or local wind speed. Accounting for advection by the currents, in-water neonate swimming speed was significantly related to current speed, first passage time, and the year. Neonates had three main response strategies to currents above 0.5 m s-1, with most increasing their swimming speed and the rest maintaining either a constant or decreased swimming speed. Neonates were significantly larger in 2018 than in 2016 but their average swimming speed was not significantly related to body size, indicating that environmental factors were more important contributors to their dispersal. We conclude that abiotic factors, including the strength and direction of the currents, significantly affect the swimming and dispersal strategy of neonate leatherback turtles and these results can help to inform strategies for releases of neonate turtles from hatcheries, future tracking studies, and conservation efforts.

Nearshore neonate dispersal of Atlantic leatherback turtles (Dermochelys coriacea) from a non-recovering subpopulation

The cryptic ‘lost years’ of sea turtles challenge conservation efforts due to unknown movements and habitat utilisation of young life stages. Behavioural information strengthens dispersal and habitat utilisation models estimating unidentified movements. In this study, leatherback hatchlings were actively tracked with miniature acoustic tags off the east coast of Costa Rica for 83.15 min (± 9.12 SD) to determine their movements and swimming behaviour. Drifters were deployed throughout the tracking process to obtain surface current data. Hatchling (n = 42) over-ground and in-water swimming speed and bearing were calculated. Mean over-ground distance travelled was 2.03 km (± 0.71 km SD) with an over-ground average swim speed of 0.41 m/s (± 0.15 m/s SD). Mean bearing was 108.08° (± 20.19° SD) compared to the 137.56° (± 44.00° SD) bearing of nearshore ocean currents during tracking. Hatchling mean in-water swimming speed was 0.25 m/s (± 0.09 m/s SD). The lower in-water speed suggests hatchlings were advected by the currents, with overall movement strongly influenced by the current direction. This information can be assimilated into broader spatiotemporal distribution models to interpret the influence of directional swimming on ecosystem utilisation and help to achieve informed management decisions across all life stages of the population.

Comparison of imidacloprid, propiconazole, and nanopropiconazole effects on the development, behavior, and gene expression biomarkers of the Pacific oyster (Magallana gigas)

Coastal areas are final recipients of various contaminants including pesticides. The effects of pesticides on non-target organisms are often unclear, especially at environmentally relevant concentrations. This study investigated the impacts of insecticide imidacloprid (IMI) and fungicide propiconazole (PRO), some of the most detected pesticides in the Arcachon Bay in France. This work also included the research of propiconazole nanoformulation (nanoPRO). The effects were assessed studying the development of the early life stages of the Pacific oyster (Magallana gigas). Oyster embryos were exposed for 24, 30, and 42 h (depending on the endpoint) at 24 °C to environmentally relevant concentrations of the two pesticides as well as to nanoPRO. The research focused on sublethal endpoints such as the presence of developmental malformations, alterations of locomotion patterns, or changes in the gene expression levels. No developmental abnormalities were observed after exposure to environmental concentrations detected in the Arcachon Bay in recent years (maximal detected concentration of IMI and PRO were 174 ng/L and 29 ng/L, respectively). EC50 of PRO and nanoPRO were comparable, 2.93 ± 1.35 and 2.26 ± 1.36 mg/L, while EC50 of IMI exceeded 200 mg/L. IMI did not affect larval behavior. PRO affected larval movement trajectory and decreased average larvae swimming speed (2 μg/L), while nanoPRO increased the maximal larvae swimming speed (0.02 μg/L). PRO upregulated especially genes linked to reactive oxygen species (ROS) production and detoxification. NanoPRO effects on gene expression were less pronounced - half of the genes were altered in comparison with PRO. IMI induced a strong dose-response impact on the genes linked to the detoxification, ROS production, cell cycle, and apoptosis regulation. In conclusion, our results suggest that current pesticide concentrations detected in the Arcachon Bay are safe for the Pacific oyster early development, but they might have a small direct effect via altered gene expressions, whose longer-term impacts cannot be ruled out.

A comprehensive system for detection of behavioral change of D. magna exposed to various chemicals

The purpose of the present study was to develop a sensitive and comprehensive method, based on D. magna swimming behavior, for toxicity assessment of environmental chemicals. Firstly, D. magna swimming in several chambers with different diameters were compared to determine the most suitable container, and then baseline behaviors during light/dark periods as well as reactions to light/dark switching and vibration stimulation were determined. Secondly, after exposure to sub-lethal concentrations of the selected 42 typical chemicals, which were classified into heavy metals, pesticides, fungicides and flame retardants, the alterations in the swimming parameters were evaluated. Our results indicated the 48-well plate was the most suitable chamber for behavioral monitoring of D. magna, and specific responsive patterns of D. magna neonates to light/dark switching and vibration stimulation were observed. The results of the behavioral assays of chemicals suggested that D. magna was the most sensitive to methylmercury-chloride and then to abamectin and chlorpyrifos. The three chemicals at several to dozens of ng/L significantly changed swimming behaviors of D. magna. Furthermore, the alteration in the behavioral parameters (average swimming speed, etc.) induced by the selected chemicals could be ascribed to various modes of actions, confirming the reliability and practicability of the monitoring method.

Behaviour and ability of a cyprinid (Schizopygopsis younghusbandi) to cope with accelerating flows when migrating downstream

AbstractThe migration corridors in regulated rivers lead downstream fish migrants, particularly juveniles to pass through water infrastructure. Accelerating flow, experienced by fish, might trigger avoidance behaviour and then influence the downstream migration efficacy. It is essential to understand the causes of avoidance behaviour exhibited by downstream migratory fish in accelerating flow. In this study, the effect of three different accelerating flows on the downstream migration behaviour of Schizopygopsis younghusbandi (S.Y) was investigated using a constriction wedge in a circulating flume. The results showed that some fish (30%, 23%, and 39% under low, medium, and high flow conditions, respectively) repeatedly attempted to burst upstream with positive rheotaxis prior to successful passage downstream. Under the low‐, medium‐, and high‐accelerating levels, the average fish swimming speeds were 89.19, 91.28, and 111.94 cm/s, respectively; these values were close to the critical swimming speed (110.42 cm/s) of the target fish. The water velocities at the fish avoidance points were centrally distributed at approximately 73.03 cm/s. Regarding turbulence, the results exhibited that the S.Y generally responded to a discrete range of &lt;50 cm2/s2 of turbulent kinetic energy and &lt; 2 N/m2 of the horizontal component of the Reynolds shear stress (RSSxy). Also, the fish that exhibited avoidance behaviour were not centrally distributed in the lateral and longitudinal velocity locations, where there was an abrupt change in the gradient. This study highlighted the impact of accelerating flow on the downstream fish migration behaviour of a cyprinid. Furthermore, this study quantified the hydraulic factors that triggered this avoidance. Thus, it provided experimental support for optimizing the design of the hydraulic factors for downstream fishways.

5 km front crawl in pool and open water swimming: breath-by-breath energy expenditure and kinematic analysis

Breath-by-breath energy expenditure during open water swimming has not yet been explored in an ecological environment. This study aimed to investigate and compare energetics and kinematics of 5km swimming, in both swimming pool and open water conditions. Through four independent studies, oxygen uptake ([Formula: see text]2) kinetics, heart rate (HR), blood lactate concentration ([La-]) and glucose level (BGL), metabolic power ([Formula: see text]), energy cost (C) and kinematics were assessed during 5km front crawl trials in a swimming pool and open water conditions. A total of 38 competitive open water swimmers aged 16-27years volunteered for this four part investigation: Study A (pool, ten females, 11 males), Study B (pool, four females, six males), Study C (pool case study, one female) and Study D (open water, three females, four males). In the swimming pool, swimmers started with an above average swimming speed (v), losing efficiency along the 5km, despite apparent homeostasis for [La-], BGL, [Formula: see text]2, [Formula: see text] and C. In open water, swimmers started the 5km with a below average v, increasing the stroke rate (SR) in the last 1000m. In open water, [Formula: see text]2 kinetics parameters, HR, [La-], BGL, respiratory exchange ratio and C were affected by the v and SR fluctuations along the 5km. Small fluctuations were observed for energetic variables in both conditions, but changes in C were lower in swimming pool than in open water. Coaches should adjust the training plan accordingly to the specificity of open water swimming.

Fibrous Flagellar Hairs of Chlamydomonas reinhardtii Do Not Enhance Swimming

The flagella of Chlamydomonas reinhardtii possess fibrous ultrastructures of a nanometer-scale thickness known as mastigonemes. These structures have been widely hypothesized to enhance flagellar thrust; however, detailed hydrodynamic analysis supporting this claim is lacking. In this study, we present a comprehensive investigation into the hydrodynamic effects of mastigonemes using a genetically modified mutant lacking the fibrous structures. Through high-speed observations of freely swimming cells, we found the average and maximum swimming speeds to be unaffected by the presence of mastigonemes. In addition to swimming speeds, no significant difference was found for flagellar gait kinematics. After our observations of swimming kinematics, we present direct measurements of the hydrodynamic forces generated by flagella with and without mastigonemes. These measurements were conducted using optical tweezers, which enabled high temporal and spatial resolution of hydrodynamic forces. Through our measurements, we found no significant difference in propulsive flows due to the presence of mastigonemes. Direct comparison between measurements and fluid mechanical modeling revealed that swimming hydrodynamics were accurately captured without including mastigonemes on the modeled swimmer’s flagella. Therefore, mastigonemes do not appear to increase the flagella’s effective area while swimming, as previously thought. Our results refute the longstanding claim that mastigonemes enhance flagellar thrust in C. reinhardtii, and so, their function still remains enigmatic.

Modeling and simulation of the intermittent swimming gait with the muscle-contraction model of pre-strains

The muscle-contraction model of pre-strains is employed to study the intermittent swimming gait of a 2D freely swimming fish. The fluid-structure interaction problem of fish swimming is solved with the finite elements method. Benefits of the intermittent swimming and the effects of the duty cycle and the tail swing number in a burst phase are emphasized. The results show that, compared to the steady swimming, a huge energy saving for swimming can be achieved by sacrificing a little speed during the intermittent swimming. Moreover, the fish swimming can be gradually transited from an intermittent mode to the continuous mode by increasing the duty cycle. With a smaller duty cycle, the fish can save more energy to obtain the same swimming velocity. A smaller tail swing number in a burst phase is more helpful to improve the energy utilization rate under the condition of Rduty = 0.5. In addition, the intermittent swimming will have more benefits at the lower and the higher average swimming speeds, and it is very important to have a proper proportion of the velocity bounds for the performance improvement of the intermittent swimming. These conclusions may have direct meanings for the development of biomimetic autonomous underwater vehicles.

Neuromodulatory Selection of Motor Neuron Recruitment Patterns in a Visuomotor Behavior Increases Speed.

Animals generate locomotion at different speeds to suit their behavioral needs. Spinal circuits generate locomotion at these varying speeds by sequential activation of different spinal interneurons and motor neurons. Larval zebrafish can generate slow swims for prey capture and exploration by activation of secondary motor neurons and much faster and vigorous swims during escape and struggle via additional activation of primary motor neurons. Neuromodulators are known to alter the motor output of spinal circuits, but their precise role in speed regulation is not wellunderstood. Here, in the context of optomotor response (OMR), an innate evoked locomotor behavior, we show that dopamine (DA) provides an additional layer to regulation of swim speed in larval zebrafish. Activation of D1-like receptors increases swim speed during OMR in free-swimming larvae. By analyzing tail bend kinematics in head-restrained larvae, we show that the increase in speed is actuated by larger tail bends. Whole-cell patch-clamp recordings from motor neurons reveal that, during OMR, typically only secondary motor neurons are active, whereas primary motor neurons are quiescent. Activation of D1-like receptors increases intrinsic excitability and excitatory synaptic drive in primary and secondary motor neurons. These actions result in greater recruitment of motor neurons during OMR. Our findings provide an example of neuromodulatory reconfiguration of spinal motor neuron speed modules where members are selectively recruited and motor drive is increased to effect changes in locomotor speed. VIDEO ABSTRACT.