Average Swimming Speed Research Articles

UV-aged microplastics induces neurotoxicity by affecting the neurotransmission in larval zebrafish

Microplastics (MPs) are nearly ubiquitous in aquatic ecosystems and may affect aquatic organisms. In this study, virgin and aged polystyrene MPs (PS-MPs) of size 1 μm were selected to analyze their adverse effects on larvae zebrafish. Exposure to PS-MPs significantly reduced the average swimming speed of zebrafish, and the behavioral effects caused by aged PS-MPs on zebrafish were more pronounced. Fluorescence microscopy revealed that 10–100 μg/L of PS-MPs accumulated in tissues of zebrafish. As an endpoint of neurotransmitter concentration, exposure to aged PS-MPs at doses ranging from 0.1 to 100 μg/L significantly increased the dopamine (DA), 5-hydroxytryptamine (5-HT), γ-aminobutyric acid (GABA), and acetylcholine (ACh) levels in zebrafish. Similarly, exposure to aged PS-MPs significantly altered the expression of genes related to these neurotransmitters (e.g., dat, 5ht1aa, and gabral genes). According to Pearson correlation analyses, neurotransmissions was significantly correlated with neurotoxic effects of aged PS-MPs. Thus, aged PS-MPs cause neurotoxicity in zebrafish through their effects on DA, 5-HT, GABA, and ACh neurotransmissions. The results highlight the importance of the neurotoxicity of aged PS-MPs in zebrafish, which has important implications for the risk assessment of aged MPs and the conservation of aquatic ecosystems.

Among-individual variation in the swimming behaviour of the amphipod Gammarus pulex under dark and light conditions

In recent years, considerable computational advancements have been made allowing automated analysis of behavioural endpoints using video cameras. However, the results of such analyses are often confounded by a large variation among individuals, making it problematic to derive endpoints that allow distinguishing treatment effects in behavioural studies. In this study, we quantitatively analysed the effects of light conditions on the swimming behaviour of the freshwater amphipod Gammarus pulex by high-throughput tracking, and attempted to unravel among individual variation using size and sex. For this, we developed the R-package Kinematics, allowing for the rapid and reproducible analysis of the swimming behaviour (speed, acceleration, thigmotaxis, curvature and startle response) of G. pulex, as well as any other organism. Our results show a considerable amount of variation among individuals (standard deviation ranging between 5 and 115 % of the average swimming behaviour). The factors size and sex and the interaction between the two only explained a minor part of this found variation. Additionally, our study is the first to quantify the startle response in G. pulex after the light is switched on, and study the variability of this response between individuals. To analyse this startle response, we established two metrics: 1) startle response magnitude (the drop in swimming velocity directly after the light switches on), and 2) startle response duration (the time it takes to recover from the drop in swimming velocity to average swimming speed). Almost 80 % of the individuals showed a clear startle response and, therefore, these metrics demonstrate a great potential for usage in behavioural studies. The findings of this study are important for the development of appropriate experimental set-ups for behavioural experiments with G. pulex.

Cue rates and surfacing characteristics of sei whales (Balaenoptera borealis) in the Falkland Islands

The cue rate (CR: blows per whale per hour), surfacing characteristics and swim speeds of sei whales (Balaenoptera borealis) were quantified fromfocal follows carried out at Berkeley Sound (East Falkland) between January and May 2017 and off the west coast of West Falkland betweenFebruary and April 2018. In Berkeley Sound, focal follows were conducted from Cape Pembroke lighthouse and from a small boat. In West Falklandall focal follows were conducted from a yacht. Thirty-seven focal follows of sei whale individuals or groups (2–5 individuals) were analysed toproduce CRs ranging from 21.99 to 46.73, with a mean of 31.46 (SD = 5.12). There was no significant difference in the CRs observed from shorevs. boat platforms or between the two study areas. Maximum submergence times exceeding 13min were recorded from both individuals and groups.The durations of 51 whale surfacing events had a mean of 6.4s (SD = 1.7). The average swim speed during boat-based sei whale focal follows was5.7kmh−1. The inter-breath intervals (IBIs) recorded from 13 solitary individuals ranged from 77.2 to 180.1s, with an overall mean of 118.6s (SD= 137.6). A combined approach incorporating IBI parameters and sequence pattern was used to classify 270 IBIs into surface dives (mean = 37.2s),intermediate dives (mean = 113.7s) and true dives (mean = 332.6s). Individuals showed marked variation in dive pattern, with some exhibitingclear cycles of true dives interspersed with surface bouts while others routinely took intermediate-duration dives interspersed by single surfacings.Sei whales in Berkeley Sound exhibited a higher proportion of surface dives than whales in West Falkland, and those surface dives were of lowermean and median IBI. Individual sei whales had surface bouts comprising a mean of 3.8 blows and a mean IBI of 33.4s. These are the firstquantifiable data on surfacing-dive patterns and CRs for sei whales in the Falkland Islands and across the wider range of the species. The data haveconservation and management relevance, including addressing availability bias for line transect and cue count abundance estimates, incorporationinto vessel strike modelling, and understanding foraging behaviour.

Astrocyte-derived exosome-transported GJA1-20k attenuates traumatic brain injury in rats.

Astrocyte-derived exosome-transported GJA1-20k attenuates traumatic brain injury in rats.

Body shape and mode of propulsion do not constrain routine swimming in coral reef fishes

AbstractIt is widely believed that because of biomechanical trade‐offs, fish body shape and the mode of propulsion are strong predictors of swimming performance, with the best cruisers, maneuverers and accelerators having different body forms and emphasizing different propulsion mechanisms. This paradigm is regularly projected onto routine swimming behaviour and dominates the ecomorphological literature, despite the paucity of field measurements.In this study, we measured variation in swimming behaviour among 48 species of Indian Ocean coral reef fishes using recordings from a remote stereo video system. We measured average swimming speed, average swimming bout distance, frequency of turns and percent of time spent station‐holding and looked for the predicted trade‐offs between them.We find little evidence of the expected relationships between swimming behaviours across species, little evidence that body shape affects swimming and few differences between species that swim by undulating the body and those that emphasize the use of median and paired fins. Taxa widely thought of as archetypical maneuverers (Chaetodon) and cruisers (Caranx) were not outliers in any behaviours.Our results indicate that swimming behaviour is not easily predicted from simple measures of body shape and that alternative swimming modes can produce comparable behavioural profiles.Read the freePlain Language Summaryfor this article on the Journal blog.

Sharp turns and gyrotaxis modulate surface accumulation of microorganisms

The accumulation of swimming microorganisms at surfaces is an essential feature of various physical, chemical, and biological processes in confined spaces. To date, this accumulation is mainly assumed to depend on the change of swimming speed and angular velocity caused by cell-wall contact and hydrodynamic interaction. Here, we measured the swimming trajectories of Heterosigma akashiwo (a biflagellate marine alga) near vertical and horizontal rigid boundaries. We observed that the probability of sharp turns is greatly increased near a vertical wall, resulting in significant changes in the distributions of average swimming speed, angular velocity, and rotational diffusivity near the wall (a quantity that has not previously been investigated) as functions of both distance from the wall and swimming orientation. These cannot be satisfactorily explained by standard hydrodynamic models. Detailed examination of an individual cell trajectory shows that wall contact by the leading flagellum triggers complex changes in the behavior of both flagella that cannot be incorporated in a mechanistic model. Our individual-based model for predicting cell concentration using the measured distributions of swimming speed, angular velocity, and rotational diffusivity agrees well with the experiment. The experiments and model are repeated for a cell suspension in a vertical plane, bounded above by a horizontal wall. The cell accumulation beneath the wall, expected from gyrotaxis, is considerably amplified by cell-wall interaction. These findings may shed light on the prediction and control of cell distribution mediated by gyrotaxis and cell-wall contact.

Neurotoxicity of tetrabromobisphenol A and SiO2 nanoparticle co-exposure in zebrafish and barrier function of the embryonic chorion

Silicon dioxide nanoparticles (n-SiO2) absorb tetrabromobisphenol A (TBBPA) and modify its bioavailability and toxicity in the aquatic phase; embryonic chorion is an efficient barrier against nanoparticles (e.g., SiO2) and influences their toxicity. However, few studies have investigated developmental neurotoxicity in fish after co-exposure to TBBPA and n-SiO2, especially considering the barrier function of the chorion. In the present study, zebrafish embryos were exposed to TBBPA (50, 100, and 200 μg/L) alone or in combination with n-SiO2 (25 mg/L) until 24 or 120 h post fertilization (hpf), in the presence and absence of the chorion. The results confirmed that TBBPA exposure alone significantly downregulated the expression of neurodevelopment marker genes (mbp, alpha-tubulin, shha, and gfap), altered acetylcholinesterase activity and acetylcholine content, and affected locomotor behavior at different developmental stages. Moreover, the results indicated that n-SiO2 promoted TBBPA-induced neurotoxic effects in zebrafish larvae at 120 hpf, including further repression of the transcription of CNS-related genes, disruption of the cholinergic system, and decrease in the average swimming speed under dark/light stimulation. However, scanning electron microscopy/energy dispersive spectroscopy analysis revealed that at 24 hpf, the embryonic chorion efficiently blocked n-SiO2 and consequently decreased the bioaccumulation of TBBPA and TBBPA-induced neurotoxicity in dechorionated zebrafish embryos. Taken together, the results demonstrate that n-SiO2 affected the bioavailability and neurodevelopmental toxicity of TBBPA, and their combined toxicity to zebrafish embryos was mitigated by embryonic chorion, which will facilitate risk assessment on n-SiO2 and TBBPA and improve understanding the function of the fish embryonic chorion.

Metal contamination and heat stress impair swimming behavior and acetylcholinesterase activity in embryo-larval stages of the Mediterranean mussel, Mytilus galloprovincialis

Behavioral parameters are increasingly considered sensitive and early bioindicators of toxicity in aquatic organisms. A video-tracking tool was specifically developed to monitor the swimming behaviour of D-larvae of the Mediterranean mussel, Mytilus galloprovincialis, in controlled laboratory conditions. Both maximum and average swimming speeds and trajectories were recorded. We then investigated the impact of copper and silver with or without a moderate rise of temperature on swimming behavior and acetylcholinesterase (AChE) activity of mussel D-larvae and the possible mechanistic link between both biological responses. Our results showed that copper and/or silver exposure, as well as temperature increase, disrupts the swimming behavior of mussel larvae which could compromise their dispersal and survival. In addition, the combined effect of temperature and metals significantly (p < 0.05) increased AChE activity in mussel larvae. Pearson's correlation analysis was performed and results showed that the AChE activity is positively correlated with maximum speeds (r = 0.71, p < 0.01). This study demonstrates the value of behavioral analyzes of aquatic invertebrates as a sensitive and integrate marker of the effects of stressors.

New concept for measuring swimming speed of free-ranging fish using acoustic telemetry and Doppler analysis

A novel technique for measuring individual fish swimming speed based on conventional acoustic telemetry and Doppler analysis was tested with live tagged fish in a field experiment at a fish farm. The aim of the experiment was to evaluate the feasibility of using this method to measure instantaneous swimming speeds over time for individual fish under commercial farming conditions. Measurements were obtained from two acoustically tagged specimen of farmed Atlantic salmon and results showed realistic speed spectra and average swimming speeds (880 mm s−1 std. 590 mm s−1 and 1080 mm s−1 std. 560 mm s−1, corresponding to 1.4 and 1.6 body lengths per second, respectively). A reference tag moored in a stationary position in the same sea cage was simultaneously measured as having a mean speed of 110 mm s−1 (std. 80 mm s−1), confirming that the method was able to distinguish between moving and stationary tags. Moreover, the mean speed of the reference tag was 10% of the overall speed range, agreeing with the error ranges observed for the concept in previously reported model experiments, further corroborating that the Doppler measurements were genuinely linked with tag movement. Commercially available acoustic tags with only a simple modification were used to generate the signal for the Doppler speed computation algorithm, implying that the technique will conveniently integrate with existing acoustic fish telemetry systems with only minor modifications. The proposed method features the ability to augment conventional telemetry data with swimming speed measurements without additional costs in tag size or complexity, promoting richer and more diverse datasets. The technique could potentially become a useful in-situ research tool with applications within both general fish behavioural biology and the study of fish performance and welfare in marine farms.

The impact of overhead dumbbell squat towards swimming speed of Tirta Palm Swimming Club members

Swimming athletes compete by how fast they can swim at a certain distance. One of the most important things that affect the swimming speed was the muscle strength of the arms and legs. The swimming speed can be increased by doing the physical exercise that can affect the arms and legs muscles which was called overhead dumbbell squat (ODS) exercise. The purpose of this study was to find out if there was an effect of ODS on increased breaststroke swimming speed of Tirta Palm Swimming Club members. This study was an experimental study with one group pretest-posttest design that was implemented for a month about 16-20 years old that met the qualifications of inclusion and did the ODS exercise thrice a week for 4 weeks. The duration of each exercise was 10 repetitions, 6 sets, and breaks for a minute in each set. The result showed that the average pretest swimming speed was 67,84 seconds and the post-test was 59,07 seconds. The analysis result of paired sample t-test showed a value p0,001, so there was a significant difference between pretest and posttest. It could be concluded that overhead dumbbell squat exercises could enhance the swimming speed of Tirta Palm Swimming Club members.

Sprint Performance in Arms-Only Front Crawl Swimming Is Strongly Associated With the Power-To-Drag Ratio.

To date, optimal propulsion in swimming has been studied predominantly using physical or computational models of the arm and seldom during real-life swimming. In the present study we examined the contributions of selected power, technique and anthropometric measures on sprint performance during arms-only front crawl swimming. To this end, 25 male adult competitive swimmers, equipped with markers on their arms and hands, performed four 25-m sprint trials, which were recorded on video. For the fastest trial of each swimmer, we determined the average swim speed as well as two technique variables: the average stroke width and average horizontal acceleration. Each participant also swam 10–12 trials over a custom-made system for measuring active drag, the MAD system. Since the propelling efficiency is 100% while swimming over the MAD system, the power output of the swimmer is fully used to overcome the drag acting on the body. The resulting speed thus represents the ratio between power output and drag. We included this power-to-drag ratio, the power output and the drag coefficient of the fastest trial on the MAD system in the analysis. Finally, the body height and hand surface area of each swimmer were determined as anthropometric variables. A model selection procedure was conducted to predict the swim speed from the two technique variables, three power variables and the two anthropometric variables. The ratio between power output and the drag was the only significant predictor of the maximal swimming speed (v = 0.86·power/drag). The variations in this ratio explained 65% of the variance in swimming performance. This indicates that sprint performance in arms-only front crawl swimming is strongly associated with the power-to-drag ratio and not with the isolated power variables and the anthropometric and technique variables selected in the present study.

Acute Adverse Effects of Metallic Nanomaterials on Cardiac and Behavioral Changes in Daphnia magna

Nanomaterials are widely believed to induce toxic effects on organisms by evoking oxidative stress. We evaluated the toxic effects of nanomaterials on the cardiac and behavioral changes in Daphnia magna under varying exposure conditions. Titanium dioxide nanoparticles (TiO2 NPs), silver nanoparticles (AgNPs), and silver nitrate (AgNO3) were selected for the acute toxicity tests. The adverse effects of the substances on the neonates including heart rate, swimming speed, and oxidative stress were measured. The heart rate level decreased as the concentration of both NPs and silver ions (Ag+) increased. The average swimming speed was measured to be approximately 15 mm/min for the control group. The swimming speed generally increased with a longer exposure to both NPs although it reached a plateau at the lowest concentration of AgNPs. A similar but less clear trend was observed for Ag+. For all substances, the overall swimming speed exhibited no correlation or weak negative correlations with the exposure concentration. The oxidative stress levels increased after exposure compared with the control group. We conclude that aquatic nanotoxicity tests should consider multilevel physicochemical, physiological, and behavioral parameters for the official guidelines to quantify more robust adverse outcomes.

Diving behavior, foraging strategies, and energetics of female Steller sea lions during early lactation

Lactating Steller sea lions (SSL; Eumetopias jubatus) are income breeders, which balance the energetic cost of provisioning a pup with alternating periods of foraging at sea and nursing onshore during a 12–36 month dependency period. Foraging dives may be benthic or epipelagic, and the diverse diet varies seasonally and geographically. The objective of this study was to use animal-borne video and data recorders (VDRs) to record prey captures and characterize the three-dimensional movements, dive performance, and foraging strategies of female SSL while rearing a pup on Lovushki Island, located in the Kuril Island Archipelago in Far Eastern Russia. Female SSL made short foraging trips (8.7 h) and remained relatively close to the rookery (< 15 km) with an average swim speed of 1.5 m sec−1 and metabolic rate of 3.15 W kg−1, which was 1.8-fold greater than their estimated resting metabolic rate. We identified two types of dives representing shallow (Type 3) and deep (Type 4) benthic foraging, primarily on Atka mackerel (Pleurogrammus monopterygius) at night when they rest on the seafloor. The estimated Field Metabolic Rate (FMR; 2.31 W kg−1) for a mean 31.7 h foraging-nursing cycle was only 1.3-fold greater than their estimated resting metabolic rate, primarily because the females spent 73% of their time onshore nursing the pup. The short foraging trips near the rookery and low FMR indicated abundant prey. On average, female SSL captured 35.4 fish during a foraging trip, which represented an estimated 20.8 kg of prey. This was sufficient to remain in energy balance and provision a pup during early lactation. However, a 10–20% reduction in the size or abundance of prey would result in a 38–76% reduction in milk production, respectively, which would cause reduced growth or death of the pup. These calculations indicate the thin margin for energy balance in SSL during early lactation. Hence, any reduction in the size or abundance of prey could have serious consequences for reproductive success and fitness.

Evaluation of post-stocking dispersal and mortality of juvenile lake trout Salvelinus namaycush in Lake Ontario using acoustic telemetry

Wild reproduction by stocked lake trout Salvelinus namaycush in Lake Ontario has yet to produce a self-sustaining population, requiring a reliance on stocking. Once released, age-1 juvenile lake trout are not typically surveyed until age-2, creating a gap in knowledge of fine-scale post-release behaviors. A method to track fine-scale movements and estimate mortality of juvenile lake trout could complement standard survey methods and benefit management decisions regarding stocking locations. We used acoustic telemetry to estimate post-stocking mortality and observe fine-scale spatial and temporal movements of 38 hatchery-reared, age-1 lake trout from an offshore stocking site in the eastern basin of Lake Ontario from 2017 to 2018. Cumulative post-stocking mortality was estimated at 5.3%, 10.5%, and 26.3% after one week, one month and one year, respectively. The majority of lake trout (68.4%) emigrated from the stocking location within two months and entered deep water (∼50 m) once warm-water incursions at the stocking site exceeded lake trout thermal preferences (15 °C). Lake trout made large movements (i.e., median 1.9 km, maximum 12.4 km straight-line distance) within the first hour post-release and had an average swimming speed of 1.64 km‧hr−1over the first day. There was no statistically significant relationship between total distance traveled and time of day, although distance traveled tended to be greater during crepuscular and dark periods compared to daylight. Our results provide a conservative estimate of post-release mortality and reveal behaviors of hatchery-reared juvenile lake trout that may be helpful when selecting stocking locations beneficial to restoration program goals.

Antagonistic effects and mechanisms of carbendazim and chlorpyrifos on the neurobehavior of larval zebrafish

Residues from multiple pesticides are frequently detected on vegetables, which may produce combined toxicity not predicted by individual toxicity data. As these combined effects present additional dangers to food safety, we have compared individual to combined effects for a variety of pesticides. Carbendazim and chlorpyrifos are the two most commonly detected pesticides in vegetables, and previous studies reported that combined exposure results in synergistic developmental toxicity to zebrafish embryos. In this study, individual and combined effects on zebrafish motor activity were examined following individual and combined exposure to assess nervous system toxicity. Further, transcriptomics methods were used to identify potential molecular mechanisms for individual and combined toxicity. Carbendazim alone induced a disorganized swim pattern characterized by increased angular velocity, turn angle, meander, and acceleration during light-dark transition, while chlorpyrifos alone reduced average swim speed and light-dark acceleration. Combined treatment significantly reduced average swim velocity and total distance traveled. Combination indices indicated strong antagonism between compounds for average speed and light-dark acceleration. Transcriptomics (RNA-seq) showed that carbendazim significantly altered the expression of genes involved in antigen processing and presentation, apoptosis, autophagy, and metabolism, including ctslb, cyp7a1, hsp70l, and ugt1a1. Alternatively, chlorpyrifos significantly altered genes involved in various nervous system-related pathways, including glutamatergic, GABAergic, dopaminergic, and calcium signaling. Protein-protein interaction (PPI) network analysis suggested that chlorpyrifos significantly downregulated genes related to light transduction, resulting in decreased sensitivity to light-dark transitions, while antagonism mainly reflected divergent effects on phototransduction and retinol metabolism. Carbendazim had no significant effects on vision-related genes such as gnat1 and gngt1, while chlorpyrifos downregulated expression, an effect reversed by the combination. Comprehensive toxicity analyses must include joint effects of co-applied pesticides for enhanced food safety.

Black Sea Mnemiopsis leidyi (Ctenophora) adult locomotion and light-induced behavior in laboratory experiments

The capacity of Ctenophores to sense light is indicated by comparative morphology and genomics data, but the relevant behavioral responses of the animals to light stimulus have not been studied yet. We developed the design of a laboratory experiment to reveal the light-induced behavior of adult Mnemiopsis leidyi from the Black Sea and identified criteria for its evaluation. Average swimming speed up to ~6–7 mm s−1 can be considered specific for the M. leidyi adults under rest or active feeding. Ctenophore reacts to a sharp light rise as an external stimulus, briefly increasing the rate several times (up to 40 mm sec−1). Analysis of motion vectors revealed no directional movement from the light source or towards it. Maximum and average rates decrease significantly for two minutes after the light is turned on, and speeds return to the original values within an hour. Small animals are more active than large ones. The mean motion rates of small comb jellies (<60 mm) were 0.7 ± 0.84 mm s−1 and 0.18 ± 0.19 mm s−1 - for large animals (>80 mm) when averaging the data for the entire observation period (from February to June).

Lamotrigine effects on immune gene expression in larval zebrafish

PurposeDespite growing evidence that neuroinflammation and pro-inflammatory cytokines are involved in the pathogenesis of seizures and epilepsy, this knowledge has not been incorporated in the proposed mechanism of action of any of the current antiseizure medications (ASMs). Here, we tested the hypothesis by assessing inflammation markers in larval zebrafish (Danio rerio) exposed to lamotrigine (LTG). MethodsIn order to establish the most appropriate LTG concentrations for the transcriptome analysis (RNAseq), we initially assessed for teratogenic (spinal cord deformation, heart oedema, failed inflation of the swim bladder) and behavioural effects (distance moved, time spent active, and average swimming speed during a light/dark test) in zebrafish larvae exposed to 0, 50, 100, 300, 500, 750, and 1000 μM LTG continuously between 5 and 120 h post fertilisation. Subsequently, we repeated the experiment with 0, 50, 100, or 300 μM LTG for transcriptomic analyses. Two databases (Kyoto Encyclopedia of Genes and Genomes; Gene Ontology) were used to interpret changes in gene expression between groups. ResultsMajor teratogenic effects were observed at concentrations of ≥ 500 μM LTG, whereas behavioural changes were observed at ≥ 300 μM LTG. Transcriptome analysis revealed a non-linear response to LTG. From the suite of differentially expressed genes (DEG), 85% (n = 80 DEGs) were upregulated following exposure to 50 μM LTG, whereas 58% (n = 12 DEGs) and 91% (n = 210 DEGs) were downregulated in response to 100 and 300 μM LTG. The metabolic pathways affected following exposure to 50 and 300 μM LTG were associated with responses to inflammation and pathogens as well development and regulation of the immune system in both groups. Notable genes within the lists of DEGs included component complement 3 (C3.a), which was significantly upregulated in response to 50 μM LTG, whereas interleukin 1β (IL-1β) was significantly downregulated in the 300 μM LTG group. The lowest exposure of 50 μM LTG is regarded as clinically relevant to therapeutic exposure. ConclusionWe demonstrated that LTG had an impact on the immune system, with a non-monotonic response curve. This dose-dependent relation could indicate that LTG can affect inflammatory responses and also at clinically relevant concentration. Further studies are needed to establish this method as a tool for screening the effects of ASMs on the immune system.

Experimental demonstration of exclusively passive feeding in the sea-turtle barnacle Chelonibia testudinaria (Linnaeus, 1758) (Cirripedia: Coronulidae)

Abstract Barnacles are sessile suspension feeders whose feeding efficiency and behavior is largely determined by the movement of water through their environment. Barnacles expend energy to feed actively in environments with low flow velocity, whereas they may feed passively at higher flow velocities, which is more efficient than active feeding. Many intertidal barnacles have been shown to switch between active and passive feeding modes as water velocities change, but little is known about the behavior of epibiotic species attached to mobile hosts, which are exposed to more consistent feeding currents. To assess the response of epibiotic barnacles to flow, laboratory-reared sea-turtle barnacles, Chelonibia testudinaria (Linnaeus, 1758), were subjected to a wide range of water velocities in both the presence and absence of food particles. Their behaviors were video-recorded and categorized using an automated behavior recognition algorithm compiled in R. Individuals of C. testudinaria only displayed passive feeding behavior, but did not feed at lowest test velocities. This species fed most at flow velocities between 25 cm s–1 and 40 cm s–1 (linear mixed effects model, F = 19.30, P &amp;lt; 0.001), a range that correlates well with the average swimming speed of two common host species, the loggerhead and green sea turtles, on which C. testudinaria resides. Chelonibia testudinaria displayed longer average feeding durations when food particles were absent than when food was abundant (linear mixed effects model, F = 11.76, P = 0.001), a result that is in line with the expectations of optimal foraging theory for suspension-feeding invertebrates. Lack of active feeding in this species may have evolved following the establishment of its epibiotic nature and may make this obligate epibiotic species entirely reliant on its hosts’ movements to provide a feeding current. This is the only barnacle species known to not facultatively switch between active and passive feeding modes.

Numerical investigation of the hydrodynamics of stingray swimming under self-propulsion

Stingrays are different from many other aquatic animals; they have dorsoventrally flattened bodies, with enlarged pectoral ‘wings’ to generate thrust for swimming. In this study, aiming to discover the key features and dynamic response characteristics of stingray swimming, 3D incompressible viscous computational fluid dynamics (CFD) simulations were conducted for self-propelled stingrays. The body geometry was reconstructed based on 3D laser scanner data of a freshwater stingray. The locomotion of the stingray was considered based on the first Fourier mode, and was analyzed using experimental measurements of the 3D kinematics in live stingrays. The amplitude for the body point was obtained using a binary linear function. The swimming velocity, as calculated through the self-propelled simulations, was within 11.9% of the nominal experimental swimming speed. It was found that the Froude efficiency of stingray swimming at slow and fast speeds is approximately 59%, suggesting that the morphological and kinematic characteristics of the stingray allow it to maintain high efficiency during swimming. The wake structures and pressure fields on the dorsal and ventral sides of the stingray were visualized. Moreover, a vortex on the upper surface of the wing’s trough and one on the lower surface of the wing’s crest were newly discovered. Furthermore, two low-speed and two high-speed boundary frequency cases were numerically simulated. It was found that the average swimming speed during the quasi-steady state has a linear relationship with the frequency of the undulatory motion. The newly discovered vortex on the upper surface of the stingray transforms from scattered small balls into several large balls. This indicates that this vortex plays an important role in lubrication.

Estrogen receptor: A potential linker of estrogenic and dopaminergic pathways in zebrafish larvae following deltamethrin exposure

Deltamethrin (DM), a type II pyrethroid insecticide, is widely used to control agricultural pests. However, its excessive use exerts a detrimental effect on the ecological environment and human health, indicating the need to study its potential risks in detail. In the present study, zebrafish embryos were exposed to varying concentrations of DM (0.1, 1, 10, and 25 μg/L) for 96 h to assess the alterations in the transcript levels of proteins of the estrogenic and dopaminergic pathways. In addition, its effect on zebrafish locomotor activity was studied. The mRNA expression of cyp19a1b, erα, erβ2, fshr, gnrh2, gnrhr3, vtg3, dat, and dr1 significantly changed after exposing the embryos to DM. Deltamethrin at 10 and 25 μg/L significantly reduced the average swimming speed of zebrafish larvae. In addition, embryos injected with zebrafish estrogen receptor α (erα) and β (erβ) morpholinos and co-exposed to 25 μg/L DM for 96 h showed reduced expression of vtg3 mRNA compared to embryos exposed to 25 μg/L DM only. The locomotor activity of erα and erβ knockdown zebrafish following DM exposure was increased significantly when compared with that of larvae exposed to 25 μg/L DM only. Our results demonstrated that DM altered the locomotor activity of zebrafish larvae and the transcript levels of the components of estrogenic and dopaminergic pathways; erα and erβ knockdown weakened these effects.