Swimming Speed Research Articles

Three-dimensional shape of natural riblets in the white shark: relationship between the denticle morphology and swimming speed of sharks.

The ridges of the dermal denticles of migratory sharks have inspired riblets to reduce the frictional drag of a fluid. In particular, the dermal denticles of white sharks (Carcharodon carcharias) are characterized by a high middle ridge and low side ridges. The detailed morphology of their denticles and their variation along the body, however, have never been investigated. Moreover, the hydrodynamic function of high-low combinations of ridges is unknown. In this article, the ridge spacings and heights of the white shark denticles were three-dimensionally quantified using microfocus X-ray computed tomography. Then, the swimming speed at which the ridges would reduce drag was hydrodynamically calculated with a flat plate body model and previous riblet data. High ridges with a large spacing were found to effectively reduce drag at a migration speed of 2.3 m s-1, while adjacent high and low ridges with a small spacing reduced drag at a burst hunting speed of 5.1 m s-1. Moreover, the above hydrodynamic calculation method was also applied to the shortfin mako shark and an extinct giant shark (called megalodon) with known ridge spacings, resulting in the estimated hunting speeds of 10.5 m s-1and 5.9 m s-1, respectively.

Does habitat modification impact morphology, performance, and inflammatory responses in an amphibian with limited dispersal capacity (Lisssotriton helveticus)?

The environment of an organism exerts selective pressures that affect mobility, feeding, reproduction as well as predator-prey and conspecific interactions. Land use changes induced by human activities modify these selective pressures and may result in the adaptation of organisms. Amphibians are ectotherms that typically show a biphasic life cycle with an aquatic and terrestrial phase, which makes them particularly sensitive to environmental change. We studied the impact of habitat modifications on palmate newt populations in the Ile de France region across four types of habitats: urban, mixed, agricultural, and natural with at least two replicates for each habitat type. We measured the morphology of newts using callipers, quantified maximal running and swimming speed and acceleration using high-speed video recordings, and quantified the swelling of the hind limb linked to an inflammatory reaction. Our results show that in urban habitats, newts are larger and heavier and have a better body condition. Females, moreover, have a larger head in natural habitats, possibly due to diet specialisation of females during the breeding season. In mixed and agricultural habitats, newts have longer limbs and show a tendency to run faster, possibly associated with the selective pressures on movement in mixed habitats. Differences in inflammatory responses were observed between sexes but not habitat types. Overall, our results show differences in morphology and trends for differences in performance in newts living in different habitats suggesting that animals are adapting to human-induced changes in their environment.

Potential effects of host competence and schooling behavior on parasite transmission in a host-pathogen system: a test of the dilution effect

High species diversity in a community may reduce the risk of infectious disease, termed the dilution effect. However, the generality of the dilution effect in different disease systems remains controversial as both host competence and behaviors of hosts may play roles in dilution or amplification of disease. Using the goldfish (Carassius auratus)-monogenean ectoparasite (Gyrodactylus kobayashii) system, effects of host competence and schooling behavior on parasite transmission were investigated while holding focal host density constant. Following competency tests of 12 fish species as potential hosts for the parasite, infection by G. kobayashii was determined on fins of goldfish mixed with each of three different species based on their level of host competence, including Prussian carp, Carassius gibelio (low competence), grass carp, Ctenopharyngodon idellus (non-competent), swordtail, Xiphophorus helleri (non-competent), and the four species combined. Compared with mean abundance (85.8 ± 25.1) on goldfish in the control group, the mean abundance on goldfish decreased significantly when paired with 10 Prussian carp (30.0 ± 16.5), but did not differ significantly when paired with 10 swordtail (70.0 ± 22.2), 10 grass carp (116.1 ± 33.2), or the multi-species of three Prussian carp, four grass carp and three swordtail (75.9 ± 30.8) during the 11-day experiment. The parasite was also found on the Prussian carp in the Prussian carp group and the multi-species group at a mean abundance of 7.1 and 10.9, respectively. Video recording showed that the school of goldfish mixed well with the Prussian carp, while they maintained separation from the grass carp and swordtail when mixed together. The distance between goldfish increased, and swimming speed and contact time decreased with the additional of other fish species for all groups. The results suggested that the presence of a low-competence host in sufficient numbers was a necessary condition for a dilution effect due to encounter reduction, and the dilution effect may also be enhanced by changes in schooling behavior of goldfish in the presence of low competence hosts. However, the presence of non-competent hosts did not result in any dilution effect owing to the specialist nature of the parasites and the lack of mixing with schools of goldfish.

Effects of fish body thickness on hydrodynamic performance for self-propulsion carangiform swimmer

The efficient swimming of fish is closely linked to their unique body morphology. This study seeks to explore the impact of body morphology on hydrodynamic performance through numerical analysis. Initially, the investigation focuses on carangiform swimmers with varying thicknesses, denoted by the thickness coefficient ψ. Key performance indicators such as vortices, velocity, pressure, thrust, and energy consumption are analyzed. The findings reveal a notable phenomenon of vortex deflection in self-propelled studies, which is affected by the interplay between initial vortices and flow conditions. Specifically, the carangiform swimmer with ψ = 1.4 exhibits the highest thrust but also the greatest energy consumption. In contrast, the swimmer with ψ = 0.8 demonstrates the best acceleration and steady swimming speeds with moderate energy usage. This paper provides new insights into how body morphology influences self-propulsion in aquatic environments.

In vitro study of ATP1A3 p.Ala275Pro mutant causing alternating hemiplegia of childhood and rapid-onset dystonia-parkinsonism.

We previously reported that ATP1A3 c.823G>C (p.Ala275Pro) mutant causes varying phenotypes of alternative hemiplegia of childhood and rapid-onset dystonia-parkinsonism in the same family. This study aims to investigate the function of ATP1A3 c.823G>C (p.Ala275Pro) mutant at the cellular and zebrafish models. ATP1A3 wild-type and mutant Hela cell lines were constructed, and ATP1A3 mRNA expression, ATP1A3 protein expression and localization, and Na+-K+-ATPase activity in each group of cells were detected. Additionally, we also constructed zebrafish models with ATP1A3 wild-type overexpression (WT) and p.Ala275Pro mutant overexpression (MUT). Subsequently, we detected the mRNA expression of dopamine signaling pathway-associated genes, Parkinson's disease-associated genes, and apoptosisassociated genes in each group of zebrafish, and observed the growth, development, and movement behavior of zebrafish. Cells carrying the p.Ala275Pro mutation exhibited lower levels of ATP1A3 mRNA, reduced ATP1A3 protein expression, and decreased Na+-K+-ATPase activity compared to wild-type cells. Immunofluorescence analysis revealed that ATP1A3 was primarily localized in the cytoplasm, but there was no significant difference in ATP1A3 protein localization before and after the mutation. In the zebrafish model, both WT and MUT groups showed lower brain and body length, dopamine neuron fluorescence intensity, escape ability, swimming distance, and average swimming speed compared to the control group. Moreover, overexpression of both wild-type and mutant ATP1A3 led to abnormal mRNA expression of genes associated with the dopamine signaling pathway and Parkinson's disease in zebrafish, and significantly upregulated transcription levels of bad and caspase-3 in the apoptosis signaling pathway, while reducing the transcriptional level of bcl-2 and the bcl-2/bax ratio. This study reveals that the p.Ala275Pro mutant decreases ATP1A3 protein expression and Na+/K+-ATPase activity. Abnormal expression of either wild-type or mutant ATP1A3 genes impairs growth, development, and movement behavior in zebrafish.

Contribution of Ladder Drill and Dryland Circuit Training to 50-meter Freestyle Swimming Speed in 13-to-14 Male Swimmers Aquatic Swimming Club

The objective of this study was to assess the impact of ladder drill and dryland circuit exercises on the pace of 50-meter freestyle swimming in male swimmers aged 13-14 years at the Aquatic Swimming Club in Medan. The researchers employed an experimental approach utilising a pre-experimental design consisting of a single group with pretest and posttest measurements. The sample comprised 8 adolescent male swimmers, aged 13-14 years, who were actively involved in the club. They were recruited via purposive sampling. The study was carried out for a duration of 6 weeks, consisting of 18 training sessions, conducted 3 times a week. Measurements were obtained using 40-meter sprint tests, medicine ball throw tests, and 50-meter freestyle swimming speed tests conducted both before and after the training treatments. The data underwent analysis through normality tests, homogeneity tests, correlation tests, and regression tests. The findings demonstrated that ladder drill training made a noteworthy contribution of 59.29% to enhancing 50-meter freestyle swimming speed. Similarly, dryland circuit training had a substantial impact, accounting for 77.44% of the improvement. Furthermore, when both training methods were combined, they together contributed 62% to the enhancement of swimming speed. The study found that both ladder drill and dryland circuit training have a substantial impact on improving the 50-meter freestyle swimming speed of male swimmers aged 13-14 at the Aquatic Swimming Club in Medan. Additionally, the dryland circuit training was found to have a greater effect than the ladder drill.

Jellyfish-Inspired Soft Robot Driven by Pneumatic Bistable Actuators.

Soft actuators offer numerous potential applications; however, challenges persist in achieving a high driving force and fast response speed. In this work, we present the design, fabrication, and analysis of a soft pneumatic bistable actuator (PBA) mimicking jellyfish subumbrellar muscle motion for waterjet propulsion. Drawing inspiration from the jellyfish jet propulsion and the characteristics of bistable structure, we develop an elastic band stretch prebending PBA with a simple structure, low inflation cost, exceptional driving performance, and stable driving force output. Through a bionic analysis of jellyfish body structure and motion, we integrate the PBA into a jellyfish-like prototype, enabling it to achieve jet propulsion. To enhance the swimming performance, we introduce a skin-like structure for connecting the soft actuator to the jellyfish-like soft robot prototype. This skin-like structure optimizes the fluid dynamics during jet propulsion, resulting in improved efficiency and maneuverability. Our study further analyzes the swimming performance of the jellyfish-like prototype, demonstrating a swimming speed of 3.8 cm/s (0.32 body length/s, BL/s) for the tethered prototype and 4.7 cm/s (0.38 BL/s) for the untethered prototype. Moreover, we showcase the jellyfish-like prototype's notable load-bearing capacity and fast-forward swimming performance compared to other driving methods for underwater biomimetic robots. This work provides valuable insights for the development of highly agile and fast responsive soft robots that imitate the subumbrellar muscle of jellyfish for efficient water-jet propulsion, utilizing skin-like structures to enhance swimming performance.

Insights on the Selection of the Coefficient of Variation to Assess Speed Fluctuation in Swimming.

The aim of this study was to compare swimming speed and speed fluctuations in front crawl between swimmers of different performance levels using discrete variables against statistical parametric mapping (SPM). The sample was composed of 34 male swimmers divided into three groups: (i) group #1-recreational swimmers; (ii) group #2-competitive swimmers aged 12 to 14 years; (iii) group #3-competitive swimmers aged 15 to 17 years. Swimming speed and speed fluctuations (calculated based on four different conditions) were used as discrete variables. Using these discrete variables, ANOVA one-way was used to verify differences between groups, and Bonferroni post-hoc correction for pairwise comparison whenever suitable. SPM (with similar statistical tests) was used to analyze the swimming speed and fluctuation as a continuous variable. Overall, both statistical approaches revealed significant differences (p < 0.001) in swimming speed and speed fluctuations. However, as discrete variables (in four different conditions), the speed fluctuation was not able to detect significant differences between groups #2 and #3. Conversely, SPM was more sensitive and did yield significant differences between these two groups. Therefore, researchers and coaches should be aware that the speed fluctuation as a discrete variable may not identify differences in swimming speed fluctuations when the average value between groups is marginal. On the other hand, SPM was more sensitive in analyzing all groups.

Swimming Performance in Elite Triathletes: Comparison Between Open Water and Pool Conditions.

This study aimed to compare performance, kinematic, and physiological variables between open water and pool swimming conditions in elite triathletes and to examine the associations between conditions on these variables. Fourteen elite triathletes (10 males and 4 females [23.4 ± 3.8 years]) performed two 1500-m swimming tests in open water and in a 25-m pool. Swimming speed, stroke rate (SR), length (SL) and index (SI), heart rate (HR), blood lactate concentrations [La-], and end-exercise oxygen uptake (EEV̇O2) were assessed in both conditions. Lower SL and SI and higher SR were obtained in open water compared with pool swimming (p < 0.05). Moreover, kinematic variables changed as a function of distance in both conditions (p < 0.05). No differences were found in the main physiological variables (HR, [La-], and EEV̇O2) between conditions. Respiratory exchange ratio presented lower values in open water than in pool conditions (p < 0.05), while time constant was higher in open water (p = 0.032). The fastest triathletes in open water obtained the best performance in the pool (r = 0.958; p < 0.001). All kinematic variables, HR and peak [La-] presented positive associations between conditions (r > 0.6; p < 0.05). Despite physiological invariance, triathletes and coaches should monitor specific open water training to adapt their swimming technique to the competitive environment.

The effect of mixed honeybee drone semen on sperm quality characteristics: A preliminary study

Following copulation, sperm of multiple honeybee (Apis mellifera (A.m.) Linnaeus (Apidae)) drones are mixed inside the spermatheca of a queen, and sperm behaviour in this environment is of importance for sperm survival and successful fertilization. The polyandrous mating system of honeybees further may allow for cryptic female choice and sperm competition to select for specific sperm traits to enable successful reproduction. This preliminary study therefore examined multiple sperm quality parameters in mixed drone semen. Thirty-one drone ejaculates were collected and split to be mixed with one and two other drones’ semen. A computerised sperm analysis system was used for analysing sperm functionality parameters, at baseline and 60 minutes. Morphology measurements included head, tail, and total sperm length. Sperm concentration was significantly higher in three-drone samples compared to other groups (p &lt; 0.001), while comparisons of sperm functional and morphometric parameters did not reveal differences. However, after 60 minutes, mixed semen samples displayed changes in terms of sperm functionality. The motility percentage significantly decreased in two-drone samples (p = 0.004). In contrast, three-drone samples had consistently lower motility and kinematic parameters at baseline, but following an hour it was the only group to show improvement in sperm progressive motility, swimming speed and kinematics. Sperm concentration correlated with the majority of functionality parameters, while, morphological measurements did not. Sperm functionality changes observed in this study, can be attributed to a combination of factors, including, mixing of drone semen, sperm concentration, and time allowing for potential sperm interaction.

Hydraulic conditions created by a ‘large’ diameter Cylindrical Bristle Cluster fish pass

Cylindrical Bristle Clusters (CBCs) provide a multi-species fish passage solution at sloped weirs. Configurations trialled to date (min. diagonal spacing between CBCs up to 0.17 m) were designed to facilitate passage of relatively small (e.g. < 30 cm) potamodromous species and may hamper the movements of larger bodied (e.g. > 40 cm) fishes, such as adult anadromous salmonids. Therefore, in this study, the hydraulic conditions created by an array of large diameter (0.13 m) CBCs positioned farther apart than in previous studies (min. diagonal spacing 0.29 m) was assessed to determine whether conditions would be suitable for facilitating the passage of small-bodied fish while also providing sufficient space for larger individuals to manoeuvre. Two experiments were conducted in an open channel flume. Experiment 1 quantified the hydraulic conditions created by a model Crump weir when unmodified and with CBCs installed in supercritical flow (Fr 1.23–3.01) on the 1:5 downstream sloping face under a low (0.08 m3 s−1) and high (0.23 m3 s−1) discharge. Patches of low water velocity were created in the wake of the CBCs, and the median (time and space averaged) velocity was reduced under both low (30.1%) and high (22.3%) discharge. Based on estimated burst swimming speeds of two common European species, the roach (Rutilus rutilus) and brown trout (Salmo trutta) (0.16 m long, swimming at 15.1 °C), this reduction in velocity would facilitate upstream passage. Experiment 2 documented the vertical velocity profile and shear stress characteristics (a measure of turbulence) within the CBC array. Unlike in Experiment 1, the CBCs were installed on the flat base of the flume and under subcritical flow (Fr = 0.31) to generate sufficient water depth. The velocity was reduced (up to 22.5%) at depths that did not exceed (> 2 cm above) the height of the bristles. Above these depths, velocity was (up to 14.6%) higher compared to open channel conditions upstream of the CBC array and a vertical shear layer was evident. As the main hydraulic benefits of CBCs occur at depths that do not exceed the bristles, their height should be tailored to site specific conditions (e.g. size of target fish species and/or depth of water at infrastructure). Field-based research is needed to determine velocity reduction at longer weirs and under a wider range of flows than can be tested under flume conditions. How the hydraulic characteristics of submerged CBCs differ from those described here with those that occur in the field when installed on a steep sloping weir under supercritical flow should be further investigated.

The Effects of Water Flow Speed on Swimming Capacity and Energy Metabolism in Adult Amur Grayling (Thymallus grubii)

The present study aimed to explore whether water flow velocity could affect the swimming ability and overall energy metabolism of wild Amur grayling (Thymallus grubii). Swimming performance was assessed by measuring critical swimming speed (Ucrit), burst speed (Uburst), and oxygen consumption rate (MO2) based on the stepped velocity test method. Our results showed that the absolute values of Ucrit and Uburst tended to increase with body length. In contrast, the relative values of Ucrit and Uburst tended to decrease and increase, respectively. MO2 in Amur grayling was elevated with increasing velocity, suggesting relatively high swimming efficiency. We also measured the biochemical indices related to energy metabolism. Lactate dehydrogenase, hexokinase, and pyruvate kinase activities significantly increased (p &lt; 0.05). Hepatic glycogen, glucose, and muscle glycogen contents decreased with the increasing trend of velocity (p &lt; 0.05), the lactic acid contents of the blood and muscles increased significantly with the increase in velocities (p &lt; 0.05), and changes in creatine phosphate content showed no significant difference (p &gt; 0.05). The results not only denote the relationship between body size and swimming speed but also show the effects of water flow velocity on energy metabolism in Amur grayling. The results provide basic data for the construction of fish passage.

Correlation between bioluminescent blinks and swimming behavior in the splitfin flashlight fish Anomalops katoptron

BackgroundThe light organs of the splitfin flashlight fish Anomalops katoptron are necessary for schooling behavior, to determine nearest neighbor distance, and to feed on zooplankton under dim light conditions. Each behavior is coupled to context-dependent blink frequencies and can be regulated via mechanical occlusion of light organs. During shoaling in the laboratory individuals show moderate blink frequencies around 100 blinks per minute. In this study, we correlated bioluminescent blinks with the spatio-temporal dynamics of swimming profiles in three dimensions, using a stereoscopic, infrared camera system.ResultsGroups of flashlight fish showed intermediate levels of polarization and distances to the group centroid. Individuals showed higher swimming speeds and curved swimming profiles during light organ occlusion. The largest changes in swimming direction occurred when darkening the light organs. Before A. katoptron exposed light organs again, they adapted a nearly straight movement direction.ConclusionsWe conclude that a change in movement direction coupled to light organ occlusion in A. katoptron is an important behavioral trait in shoaling of flashlight fish.

Incorporating vertical movement of fishes in habitat use models.

Fish telemetry studies now routinely collect positional and depth data, yet analytical approaches that integrate three-dimensional data are limited. Here we apply the potential path volume (PPV) model, a method previously developed to estimate habitat volume based on rates of avian movement, to free-swimming fish. Using a telemetry dataset of white sucker (Catastomus commersonii) from Turkey Lake (Ontario, Canada), we evaluated the effects of the number of spatial positions and different methods of selecting swim speed (vswim), a key parameter for PPV models, on habitat volume estimates. We subsequently compared habitat volume estimates and habitat overlap among white sucker pairs from the PPV models to those calculated using kernel utilization distribution-based approaches. The number of spatial positions in the PPV model had a significant effect on habitat volume estimates, whereas the magnitude of the vswim parameter or its specificity (constant value vs. fish-season specific parameter values) did not affect habitat volume estimates. The PPV method resulted in larger habitat volume estimates and greater habitat overlap estimates among fish pairs relative to those obtained from a three-dimensional kernel utilization distribution method. The PPV model is a useful analytical tool that, by incorporating potential animal movement into habitat use evaluations, can help answer key ecological questions and provide insight into fish space use in a wide range of conservation and management applications.

3D Printed Swordfish‐Like Wireless Millirobot

Inspired by the efficient swimming capabilities of swordfish, a novel wireless soft swordfish‐like robot with programmable magnetization has been developed, integrating direct‐ink‐writing (DIW) 3D printing and assembly technology. This 20 mm long robot features a streamlined form and magnetically programmable movements, enabling biomimetic locomotion patterns such as straight‐line swimming and turning swimming. The robot includes a silicone‐based torso (body, abdomen, and pectoral fin) and a crescent‐shaped tail fin made from a magnetically programmable polymer embedded with neodymium‐iron‐boron (NdFeB) particles. The tail fin, fabricated by multi‐material alternating printing to achieve a gradient magnetism distribution, is controlled by an external magnetic field to mimic the rapid oscillation of a swordfish's tail, achieving a swimming speed of 0.51 BL/ s. The tail fin's asymmetric oscillation amplitudes, adjusted by magnetic field control, allow the robot to transition seamlessly from high‐speed straight swimming to agile turning. The robot can perform tracking swimming along specific planned paths, such as “C” and “Z” shaped trajectories. Potential applications include environmental monitoring and targeted drug release. The multi‐material 3D printing technology enhances the robot's efficiency and sensitivity in simulating natural biological movements, extending to the design and development of various flexible devices and soft robots.

A longitudinal behavioral analysis of aquarium whale sharks (Rhincodon typus): insights into anticipatory cues, individual variation, and social interaction

Rhincodon typus, or the whale shark, is the largest extant fish in the world and is classified as endangered on the IUCN’s Red List. Due to their enormous size and conservation status, whale sharks are rarely housed in aquaria. Here we present a behavioral analysis culminating from a large effort by 89 observers from 2008–2012 to study four R. typus (ID codes: AL, TA, TR, YU) longitudinally in an aquarium setting. We found that relatively simple behavioral metrics such as swim speed, depth occupation, swimming direction, and lead-follow interactions demonstrated R. typus individual variation and responses to habitat changes. All sharks displayed increased swim speeds 30-minutes before regimented feed times, when there was scent of food being fed to other animals in the habitat. Consistently in the habitat, one male shark (YU) was recorded swimming more at depth, faster, almost exclusively clockwise, and engaged in fewer close proximity interactions with others than expected by chance. In contrast, a larger female shark (AL) was observed swimming the slowest, at the surface more than others, led other sharks more than she followed, and had strong lead-follow interactions with another shark of the opposite sex (TA). TA and TR did not differ from each other in depth profiles or speed, but did differ in their proclivity to lead or follow. Depth preferences and lead-follow interactions suggest some partitioning of the habitat and the possibility of social hierarchy in this species. These results represent the first longitudinal behavioral analysis of aquarium R. typus, offering meaningful similarities and contrasts to field observations.

Variations in vertical distribution of developing snow crab Chionoecetes opilio and red snow crab Chionoecetes japonicus (Crustacea, Decapoda, Majoidea) larvae in experimental temperature gradients

ABSTRACT In the Sea of Japan, field studies have found snow crab and red snow crab larvae occur between the surface and depths of up to 550 m and 1100 m, respectively. In this region, snow crab larvae hatch at depths of 240–260 m and red snow crab larvae hatch at 1000–1500 m. To understand their vertical distribution during the larval period, we investigated the upward swimming speed of newly hatched larvae (first-stage zoea) and the behaviour of all larval stages (first and second zoeal and megalopal stages) in a temperature gradient under laboratory conditions. Our results showed that the larvae have the potential to reach the surface within a few days of hatching. As the larvae developed, they preferred greater depth and lower temperatures; although they temporarily rose to higher levels immediately after each moult. The zoeae and megalopae of both species did not occur beyond the 16 and 6°C temperature layers, respectively. The preferred position of the larvae in the gradient temperature did not differ between the two species. The present study suggests that Chionoecetes larvae transported to unsuitable temperatures may not die, but could escape from low temperatures by upward swimming and from high temperatures by sinking.

Interspecific differences in swimming performance, behavior and survival between native Italian gudgeon (Gobio benacensis Pollini, 1816) and non-native European gudgeon (Gobio gobio Linnaeus, 1758)

Introduction of non-native species is an important cause of biodiversity decline in rivers. Separated by mountains and salt water, the freshwater fish fauna in Italy has experienced a natural isolation from fish in continental Europe. As a consequence, several Italian fish species have diverged from their European sister species, likely with unique adaptations to the local environment. Relatedly, the region is also susceptible to the invasion of non-native fish, and today almost half the fish species present are of non-native origin. Several of these non-native species have Italian congeners susceptible to competition and hybridizations, and, in the long run, displacements and extinctions. One such example is the Italian gudgeon (Gobio benacensis) and its European congener European gudgeon (Gobio gobio). During the last few decades the European gudgeon was introduced in Italian waters and has since spread rapidly, causing progressive declines in the Italian species. As for several other similar species pairs, little is known about potential differences in ecology and behavior. Here we study differences between Italian and European gudgeons in a controlled laboratory environment, using a combined open field and provoked escape response test, as well as tracking their sympatric survival over time in the hatchery. The smaller Italian gudgeon displayed a lower maximum swimming speed compared to the larger European gudgeon. The Italian gudgeon also experienced substantially higher sympatric mortality, resulting in only European gudgeon surviving to the end of the experiment. Contrary to expectations, no difference was seen in boldness and the Italian gudgeon displayed a higher movement activity, moving a larger distance in an open field test, compared to its European sister species. The reported differences could play a role in the replacement process, and may also have impacts on the surrounding ecosystem, and the prey and predators that have coevolved with the Italian species.

Using heart rate and acceleration biologgers to estimate winter activity costs in free-swimming largemouth bass

Winter is a critical period for largemouth bass (Micropterus nigricans) with winter severity and duration limiting their population growth at northern latitudes. Unfortunately, we have an incomplete understanding of their winter behaviour and energy use in the wild. More winter-focused research is needed to better understand their annual energy budget, improve bioenergetics models, and establish baselines to assess the impacts of climate warming; however, winter research is challenging due to ice cover. Implantable tags show promise for winter-focused research as they can be deployed prior to ice formation. Here, using swim tunnel respirometry, we calibrated heart rate and acceleration biologgers to enable estimations of metabolic rate (ṀO2) and swimming speed in free-swimming largemouth bass across a range of winter-relevant temperatures. In addition, we assessed their aerobic and swim performance. Calculated group thermal sensitivities of most performance metrics indicated the passive physicochemical effects of temperature, suggesting little compensation in the cold; however, resting metabolic rate and critical swimming speed showed partial compensation. We found strong relationships between acceleration and swimming speed, as well as between ṀO2 and heart rate, acceleration, or swimming speed. Jackknife validations indicated that these modeled relationships accurately estimate swimming speed and ṀO2 from biologger recordings. However, there were relatively few reliable heart rate recordings to model the ṀO2 relationship. Recordings of heart rate were high-quality during holding but dropped during experimentation, potentially due to interference from aerobic muscles during swimming. The models informed by acceleration or swimming speed appear to be best suited for field applications.

Influence of microplastic pollution on the toxicity of potamodromous fish grass carp (Ctenopharyngodon idellus) and its swimming capacity

Microplastics (MPs), as a ubiquitous environmental contaminant in marine and freshwater systems, produced a significant influence on the physiological characteristics of aquatic organisms, and inevitably posed unknown effects on their swimming capacity. Herein, we evaluated the MPs accumulation in potamodromous fish, Ctenopharyngodon idellus, and their potential effects on oxidative stress, neurotoxicity, gut microbial diversity, and swimming capability through a toxic-control experiment. Juvenile fish were exposed to 5 µm polystyrene-MPs (PS-MPs) for 6 days at concentrations of 0.1, 1, and 10 mg/L. Exposure to PS-MPs resulted in significant inhibition of acetylcholinesterase (AChE) in the brain of fish, with significant increases in superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels at 1 and 10 mg/L exposures. Meanwhile, MPs altered grass carp gut microbiota and reduced the Shannon diversity index. In addition, MPs significantly increased induced swimming speed by observing the flow rate at which grass carp happened to produce a reverse current behavioral response. The 1 and 10 mg/L of MPs treatments can significantly reduce the critical swimming speed of grass carp, meaning that the completion of the life history of grass carp may be delayed. Furthermore, there were significant correlations between biomarkers and indicators of swimming capacity. Therefore, the present study suggests that MPs produced a negative effect on the physiological properties of fish, reducing the swimming capacity of migratory fish.