Average Swimming Speed Research Articles

Feeding Behavior and Bait Selection Characteristics for the Portunidae Crabs Portunus sanguinolentus and Charybdis natator

Understanding the feeding behavior of Portunidae crabs with different baits can improve bait selection and is crucial for improving the effectiveness of crab fishing gear. This study, conducted in indoor experimental tanks, used trajectory tracking software and two types of natural baits (mackerel (Scomber australasicus) and squid (Uroteuthis chinensis)) to understand the behavior of Portunus sanguinolentus and Charybdis natator. Spatial distribution results showed that P. sanguinolentus was frequently present in the starting area (S1) and bait area (S3) in the control and treatment groups. However, C. natator was frequently present and concentrated in the S1 area compared to the middle areas S2 and S3, and only in the mackerel treatments were they observed to move to the S3 areas. The spatial distribution results indicate that P. sanguinolentus shows a stronger willingness to explore its surroundings, while C. natator is generally in a stationary, wait-and-see state. The swimming speeds of P. sanguinolentus and C. natator showed different trends. P. sanguinolentus showed continuous movement with no fixed speed when no bait was present in the control groups. However, when treated with mackerel and squid, the average swimming speed of P. sanguinolentus was faster (>5 cm/s) in the first 10 min and showed a more stable movement speed when searching for the baits. C. natator showed a stationary or low movement speed when no bait was present in the control groups. However, when C. natator perceived the presence of the baits in the treatment groups, their movement speed increased in the first 10 min. In addition, there was no significant difference between male and female crabs of P. sanguinolentus and C. natator in movement speed in the control and treatment groups. Compared to C. natator, P. sanguinolentus might be more sensitive to natural baits, as shown by its movement from S1 to S3. The results indicate that the species of Portunidae crabs show different bait selections. Natural baits (mackerel and squid) are recommended for catching P. sanguinolentus in crab fisheries.

Numerical simulation on the interaction of median fins for enhancing vortex dynamics and propulsion performance in fish self-propelled swimming

Studies have shown that fish can enhance propulsion performance by utilizing the interaction between median fins (dorsal, anal, and caudal fins), compared to fish with only caudal fin. However, most of the current studies are based on the fish oscillating in-place, and the analysis of median fins interaction to improve swimming propulsion performance is still insufficient, and the mechanism needs further study. This study applied three-dimensional numerical simulation methods to solve the process of grass carp accelerating from a stationary state to cruising state under different body and median fins combination, as well as different motion parameter models. A comparative quantitative analysis of different models was conducted to assess the impact of median fins interactions on enhancing swimming performance, with a detailed analysis of the hydrodynamic mechanisms and their relationship with vortex dynamics. The results indicated that interactions between median fins could generate significant hydrodynamic benefits, with the fish's average swimming speed increasing up to 4.6 times, thrust up to 33.47%, and swimming efficiency up to 25.48%. This study found that the enhancement of propulsion performance was due to the formation of high-intensity and persistent posterior body vortices by the movements of the dorsal and anal fins, which were captured by the leading-edge of the caudal fin, greatly enhancing the strength of the leading-edge vortex. This study elucidates the hydrodynamic mechanisms of the interaction between median fins and could provide new insights into the efficient swimming mechanism of fish in nature.

LUO-V2 and MSPerception: A multi-fin co-drive robotic fish and its multi-sensor-based experimental system

Experimental systems for analyzing robotic fish swimming play a crucial role in optimizing robotic fish, which prompted us to design an experimental system that combines information from multiple sensors to address the shortcomings of current experimental systems with a single measurement. Furthermore, we are interested in a multi-fin co-drive robotic fish. This paper presents the design of a robotic fish, LUO-V2, and an experimental system, MSPerception. The LUO-V2 represents a novel solution for developing multi-fin co-drive robotic fish. It also provides a controller for LUO-V2, which can synchronously control the multi-fin of the robotic fish. Furthermore, the MSPerception system has been designed based on the fusion of multi-sensor information, which can sense the average thrust, swimming speed, and flow field, which provides an effective tool for studying robotic fish swimming. MSPerception was employed to investigate the factors influencing the swimming performance of LUO-V2 and to compare it with the flow field around the caudal fin of a real fish. The experimental results demonstrated that the multi-fin co-drive significantly enhanced the robotic fish’s performance. This research can provide a theoretical foundation for developing multi-fin co-drive robotic fish and experimental systems.

The impacts of microplastics on zebrafish behavior depend on initial personality state

Microplastic pollution is associated with inflammation, gut dysbiosis and behavioral changes in fish. Fish have distinct personality traits but the role of personality in behavioral toxicology is rarely considered. We classified zebrafish on four behavioral axes: boldness, anxiety, sociability and exploration tendency then exposed them to low- or high- concentrations of two types of polyethylene microplastics (low- and high-density) for 28 days. Behaviors, antioxidant enzymes (catalase and superoxide dismutase), and gut microbiome were then measured. There were direct effects of microplastics on boldness, anxiety and sociability. However, fish retained their initial behavioral tendencies. Exposure to all microplastic treatments reduced average swimming speed and decreased the time spent motionless. Microplastic exposure did not affect antioxidant enzymes but did cause significant changes in the composition of the gut microbiome. This study demonstrates that environmentally realistic concentrations of microplastics can alter fish behavior, but much of the variance in response can be explained by personality.

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.

Numerical simulation of optimizing the swing curve of a 3DOF biomimetic pectoral fin in drag mode

In response to the optimization problem of the motion law of the pectoral fins of biomimetic robotic fish, this paper uses computational fluid dynamics (CFD) methods to achieve the CFD optimization of two types of rigid biomimetic pectoral fins with three degrees of freedom (DOF): elliptical and 8-shaped swing curves. By analyzing the hydrodynamic characteristic curve of the pectoral fins, pressure distribution upstream and downstream of the fin surface, velocity vector of the surrounding flow field during pectoral fin swing, and three-dimensional vortex structure, it is found that when the pectoral fins are pushed forward in an elliptical swing curve, the resistance peak value decreases after two optimizations. However, at the same time, a certain amount of thrust is lost. When the pectoral fin advances in an 8-shaped swinging curve, after two optimizations, the pectoral fins resistance decreases while maintaining an enormous thrust, comprehensively improving the propulsive effect of the pectoral fin on the robotic fish. By substituting the optimized 8-shaped pattern into the robotic fish model, it is found that the flapping angle of 35° has better drag reduction performance, and the average swimming speed of the robotic fish is the fastest at this angle.

Swimming ability of Schizothoracinae fishes in Yarlung Zangbo River of China.

The Yarlung Zangbo River is a river with abundant hydropower resources but fragile biodiversity in China. As an important benchmark for both research and ecological management, there is still a lack of knowledge about the swimming ability of fishes in the Yarlung Zangbo River. The induced flow velocity (Uind), critical swimming speed (Ucrit), and burst swimming speed (Uburst) of five Schizothoracinae species were tested in this study. Relative swimming ability related to body length and body shape was calculated. The results indicated that the average absolute swimming speeds (Uind-a, Ucrit-a, and Uburst-a) of all the experimental fish were 10.20 ± 0.01, 57.58 ± 3.28, and 69.54 ± 2.94 cm/s, respectively, and the corresponding relative Uind, Ucrit, and Uburst related to body length (Uind-l, Ucrit-l, Uburst-l) were 1.15 ± 0.07, 5.04 ± 0.26, and 7.23 ± 0.28 BL/s, respectively. Moreover, relative Uind, Ucrit, and Uburst related to body shape (Uind-s, Ucrit-s, and Uburst-s) were 0.80 ± 0.13, 2.49 ± 0.51, and 4.32 ± 0.57 cm-2/s, respectively. No significantly differences in relative swimming speeds existed among five species. Only Oxygymnocypris stewartii was significantly weaker in Uburst-s than Schizothorax o'connori. The body shape showed a stronger relationship with swimming speed than the body length did. Schizothoracinae fish in the Yarlung Zangbo River basin are less sensitive to the water flow and performed weaker Ucrit and Uburst compared to those in the Yangtze River basin, indicating that Schizothoracinae fish in the Yarlung Zangbo River may be more susceptible to threats from environmental changes. The paper enriched the research on the swimming ability of Schizothoracinae fishes and provided efficient data for the fish conservation in the Yarlung Zangbo River.

Numerical study of collective motion of microswimmers in Giesekus viscoelastic fluids

Few simulations currently explore the dynamics of microswimmers swimming through viscoelastic environments. In this study, we employ a direct-forcing fictitious domain method to investigate the collective behavior of spherical squirmers within viscoelastic fluids at low Reynolds numbers. Our findings reveal clear differences between pusher and puller swimmers: puller swimmers exhibit a tendency to aggregate into clusters, particularly noticeable in suspensions with high concentrations, which increases the average speed of the swimmers. Through an analysis of the cluster-size distribution function, we observe the larger-scale clusters of puller swimmers with increasing concentration. Moreover, the presence of fluid elasticity significantly reduces both the average swimming speed of squirmers and the fluid’s kinetic energy.

Static magnetic fields reduce swimming activity of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) larvae

Abstract Static magnetic fields (B-fields) are introduced in marine ecosystems by anthropogenic sources such as subsea power cables. Larvae of the gadoids Atlantic haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua) disperse over the continental shelf and may encounter B-fields, which could alter their behavior. We tested the behavior of 184 gadoid larvae while they were being exposed to a B-field (22–156 μT), which is in the intensity range of that produced by a high-voltage direct current cable, for a duration of 10 min in a raceway tank. We present a reanalysis of published data on 92 haddock larvae combined with newly collected data on 92 cod larvae tested under the same settings. Exposure did not affect the spatial distribution of the larvae. Both species displayed the same proportion of nonexploratory (78%) and exploratory (22%) individuals. Exposure significantly reduced the average swimming speed of the nonexploratory larvae by 32% and the average acceleration by 30%. Exploratory larvae were not affected. These results indicate that the swimming behavior of a high proportion of gadoid larvae would be reduced by weak static B-fields. Consequences of exposure on dispersal and survival at the population scale awaits further work using biophysical-coupled models.

Multiflagellarity leads to the size-independent swimming speed of peritrichous bacteria.

To swim through a viscous fluid, a flagellated bacterium must overcome the fluid drag on its body by rotating a flagellum or a bundle of multiple flagella. Because the drag increases with the size of bacteria, it is expected theoretically that the swimming speed of a bacterium inversely correlates with its body length. Nevertheless, despite extensive research, the fundamental size-speed relation of flagellated bacteria remains unclear with different experiments reporting conflicting results. Here, by critically reviewing the existing evidence and synergizing our own experiments of large sample sizes, hydrodynamic modeling, and simulations, we demonstrate that the average swimming speed of Escherichia coli, a premier model of peritrichous bacteria, is independent of their body length. Our quantitative analysis shows that such a counterintuitive relation is the consequence of the collective flagellar dynamics dictated by the linear correlation between the body length and the number of flagella of bacteria. Notably, our study reveals how bacteria utilize the increasing number of flagella to regulate the flagellar motor load. The collective load sharing among multiple flagella results in a lower load on each flagellar motor and therefore faster flagellar rotation, which compensates for the higher fluid drag on the longer bodies of bacteria. Without this balancing mechanism, the swimming speed of monotrichous bacteria generically decreases with increasing body length, a feature limiting the size variation of the bacteria. Altogether, our study resolves a long-standing controversy over the size-speed relation of flagellated bacteria and provides insights into the functional benefit of multiflagellarity in bacteria.

Employing Robotics for the Biomechanical Validation of a Prosthetic Flipper for Sea Turtles as a Substitute for Animal Clinical Trials

Sea turtles are a keystone species for the ocean’s ecosystem, with all species currently being listed as endangered. Such a threat is mainly due to human factors such as fishing net entanglement. This entanglement often comes at the expense of turtles losing a pectoral flipper. The reduction in a sea turtle’s survival odds upon losing a flipper is a significant concern. This issue extends beyond individual animals, as the potential extinction of sea turtles could have detrimental effects on ocean health and subsequently disrupt our lifestyles. In this work, with the help of robotics, we tested the suitability of a prosthetic flipper for sea turtles that have lost a flipper. Testing with our sea-turtle-inspired robot helped to demonstrate the prosthetic flipper’s performance without clinical trials in live animals. The robot showed that the prosthetic could closely mimic the sea turtle’s downstroke and upstroke, allowing the animal to regain control in roll, pitch, and yaw, despite the absence of anatomical joints and related muscles. Additionally, swim speed tests provided an average swim speed of 0.487 m/s while dragging 6 m of cable to give a calculated maximum swim speed of 0.618 m/s, coming close to the average swim speed of wild sea turtles of 0.6 m/s. Our aspiration is that the findings from this study will pave the way for an open-source implant design, empowering veterinary professionals globally to aid injured turtles. Furthermore, this research promises to inspire additional animal-based robotic designs, advancing technologies geared towards assisting other animals in distress.

Muscle power production during intermittent swimming in bluegill sunfish.

Locomotion is essential for the survival and fitness of animals. Fishes have evolved a variety of mechanisms to minimize the cost of transport. For instance, bluegill sunfish have recently been shown to employ intermittent swimming in nature and in laboratory conditions. We focused on the functional properties of the power-producing muscles that generate propulsive forces in bluegill to understand the implications of intermittent activity. We used in vivo aerobic or red muscle activity parameters (e.g., oscillation frequency and onset time and duration of activation) in muscle physiology experiments to examine muscle power output during intermittent versus steady swimming in these fish. Intermittent propulsion involves swimming at relatively slow speeds with short propulsive bursts alternating with gliding episodes. The propulsive bursts are at higher oscillation frequencies than would be predicted for a given average swimming speed with constant propulsion. The work-loop muscle physiology experiments with red muscle demonstrated that intermittent activity allows muscle to produce sufficient power for swimming compared with imposed steady swimming conditions. Further, the intermittent muscle activity in vitro reduces fatigue relative to steady or continuous activity. This work supports the fixed-gear hypothesis that suggests that there are preferred oscillation frequencies that optimize efficiency in muscle use and minimize cost of transport.

Insight into the mechanisms of neuroendocrine toxicity induced by 6:2FTCA via thyroid hormone disruption

6:2 fluorotonic carboxylic acid (6:2 FTCA), a novel substitute for perfluorooctanoic acid (PFOA), is being used gradually in industrial production such as coatings or processing aids, and its detection rate in the aqueous environment is increasing year by year, posing a potential safety risk to aquatic systems and public health. However, limited information is available on the effects and mechanism of 6:2 FTCA. Therefore, this study was conducted to understand better the neuroendocrine effects of early exposure to 6:2 FTCA and the underlying mechanisms on zebrafish. In this study, zebrafish embryos were treated to varied doses of 6:2 FTCA (0, 0.08 μg/mL, 0.8 μg/mL and 8 μg/mL) at 4 h post-fertilization (hpf) for a duration of six days, which exhibited a pronounced inhibition of early growth and induced a disorganized swim pattern characterized by reduced total swim distance and average swim speed. Simultaneously, the thyroid development of zebrafish larvae was partially hindered, accompanied by decreased T3 levels, altered genes associated with the expression of thyroid hormone synthesis, transformation and transportation and neurotransmitters associated with tryptophan and tyrosine metabolic pathways. Molecular docking results showed that 6:2 FTCA has a robust binding energy with the thyroid hormone receptor (TRβ). Moreover, exogenous T3 supplementation can partially restore the adverse outcomes. Our findings indicated that 6:2 FTCA acts as a thyroid endocrine disruptor and can induce neuroendocrine toxic effects. Furthermore, our results show that targeting TRβ may be a potentially therapeutic strategy for 6:2 FTCA-induced neuroendocrine disrupting effects.

Integrated Microfluidic-Electromagnetic System to Probe Single-Cell Magnetotaxis in Microconfinement.

Magnetotactic bacteria have great potential for use in biomedical and environmental applications due to the ability to direct their navigation with a magnetic field. Applying and accurately controlling a magnetic field within a microscopic region during bacterial magnetotaxis studies at the single-cell level is challenging due to bulky microscope components and the inherent curvilinear field lines produced by commonly used bar magnets. In this paper, a system that integrates microfluidics and electromagnetic coils is presented for generating a linear magnetic field within a microenvironment compatible with microfluidics, enabling magnetotaxis analysis of groups or single microorganisms on-chip. The platform, designed and optimised via finite element analysis, is integrated into an inverted fluorescent microscope, enabling visualisation of bacteria at the single-cell level in microfluidic devices. The electromagnetic coils produce a linear magnetic field throughout a central volume where the microfluidic device containing the magnetotactic bacteria is located. The magnetic field, at this central position, can be accurately controlled from 1 to 10 mT, which is suitable for directing the navigation of magnetotactic bacteria. Potential heating of the microfluidic device from the operating coils was evaluated up to 2.5 A, corresponding to a magnetic field of 7.8 mT, for 10 min. The maximum measured heating was 8.4 °C, which enables analysis without altering the magnetotaxis behaviour or the average swimming speed of the bacteria. Altogether, this work provides a design, characterisation and experimental test of an integrated platform that enables the study of individual bacteria confined in microfluidics, under linear and predictable magnetic fields that can be easily and accurately applied and controlled.

Swimming behavior and energy metabolism of the calanoid copepod invader Sinodiaptomus sarsi

The appearance of invasive species threatens the integrity of aquatic ecosystems. Much is known about dispersal and introduction mechanisms while little is known on the biological properties of invasive species, such as behavior and energy efficiency, allowing them to successfully colonize new environments and compete with native species. This study examines the functional features of the Asian invasive copepod Sinodiaptomus sarsi (Rylov, 1923) that has invaded Europe since 2016. We focused on the energy metabolism and kinematic parameters of the main swimming types (i.e., gliding, hovering, small relocation jumps, and the escape reaction) of females and males of S. sarsi. Based on the above parameters, the mechanical energy for swimming and the respiration energy needed for movement were calculated. Females and males spend up to 95% of time hovering and slowly gliding at a speed of up to 0.5 cm s−1. During the remaining time, the average swimming speed was 8 cm s−1 by small jumps. In contrast, the average speed was 42 cm s−1 during escape swimming. Non-ovigerous females moved faster than ovigerous females during all relocation swimming types except for upward gliding. While performing small jumps with a frequency of 0.79 Hz, the respiration rate of active non-ovigerous females (0.32 ± 0.03 µg O2 ind−1 h−1) was 2.1 times higher than that of anesthetized individuals. The respiration energy associated with movement was 2.6 * 10−3 J h−1, while the total mechanical energy was only 4.2% of this value. The low energy cost of feeding along with the high speed of locomotion may explain the success of this Asian invader in European waters.

Mitochondrial Dysfunction Was Involved in Decabromodiphenyl Ethane-Induced Glucolipid Metabolism Disorders and Neurotoxicity in Zebrafish Larvae.

Decabromodiphenyl ethane (DBDPE), a novel brominated flame retardant, is becoming increasingly prevalent in environmental and biota samples. While DBDPE has been shown to cause various biological adverse effects, the molecular mechanism behind these effects is still unclear. In this research, zebrafish embryos were exposed to DBDPE (50-400 μg/L) until 120 h post fertilization (hpf). The results confirmed the neurotoxicity by increased average swimming speed, interfered neurotransmitter contents, and transcription of neurodevelopment-related genes in zebrafish larvae. Metabolomics analysis revealed changes of metabolites primarily involved in glycolipid metabolism, oxidative phosphorylation, and oxidative stress, which were validated through the alterations of multiple biomarkers at various levels. We further evaluated the mitochondrial performance upon DBDPE exposure and found inhibited mitochondrial oxidative respiration accompanied by decreased mitochondrial respiratory chain complex activities, mitochondrial membrane potential, and ATP contents. However, addition of nicotinamide riboside could effectively restore DBDPE-induced mitochondrial impairments and resultant neurotoxicity, oxidative stress as well as glycolipid metabolism in zebrafish larvae. Taken together, our data suggest that mitochondrial dysfunction was involved in DBDPE-induced toxicity, providing novel insight into the toxic mechanisms of DBDPE as well as other emerging pollutants.

Design, fabrication, and realisation of a robotic fish actuated by dielectric elastomer with a passive fin

AbstractRobotic fish actuated by smart materials has attracted extensive attention and has been widely used in many applications. In this study, a robotic fish actuated by dielectric elastomer (DE) films is proposed. The tensile behaviours of DE film VHB4905 are studied, and the Ogden constitutive equation is employed to describe the stress‐strain behaviour of the DE film. The fabrication processes of the robotic fish, including pre‐stretching treatment of the DE films, electrode coating with carbon paste, and waterproof treatment, are illustrated in detail. The dynamic response of the fabricated DE actuators under different excitation voltages is tested based on the experimental setup. Experimental results show that the first‐order natural frequencies of the obtained DE actuator in air is 4.05 Hz. Finally, the swimming performances of the proposed robotic fish at different driving levels are demonstrated, and it achieves an average swimming speed of 20.38 mm/s, with a driving voltage of 5kV at 0.8 Hz.

Isopropyl 3-(3,4-dihydroxyphenyl)-2-hydroxypropanoate plays an anti-hypoxic role through regulating neuroactive ligand-receptor interaction signaling pathway in larval zebrafish

Isopropyl 3-(3,4-dihydroxyphenyl)-2-hydroxypropanoate (IDHP) is the core active substance of salvia miltiorrhiza in disease treatment. The significance of our work lies in evaluating the ameliorating effects of IDHP on hypoxia-induced injury and investigating its mechanisms. We examined the morphology, dopamine neurons (DANs), cerebral vessels, and behavior of zebrafish larvae administrated by IDHP/VHC after hypoxia-induction. We next sought to explore its anti-hypoxic mechanisms via transcriptome analysis and qPCR experiments. The results indicated that hypoxia-induced injuries, including decreased length of DANs, number of cereal vessels, total swimming distance, and average swimming speed, were all alleviated by IDHP. Furthermore, transcriptome analysis provided a sign that IDHP most likely played the anti-hypoxic role through the neuroactive ligand-receptor interaction (NLRI) signaling pathway. Consistently, expression of related genes, such as f2rl1.1, p2ry10, npy1r, ptger2b, ptger2b, pth2rb, and nmur1a, was downregulated by hypoxia induction and recovered after IDHP administration. Therefore, we speculated that, via regulating NLRI, IDHP reduced inflammation, promoted angiogenesis, modulated blood pressure and flow, and inhibited cell apoptosis, and eventually played an anti-hypoxic role.

The impact of ocean acidification on the eye, cuttlebone and behaviors of juvenile cuttlefish (Sepiella inermis)

The cuttlefish (Sepiella inermis) is an economically important species in the coastal seas of China. The impacts of ocean acidification on the ability of juvenile cuttlefish to select a suitable habitat, its hunting and swimming behavior, remains unknown. We examined behavior-related responses and the eye and cuttlebone structure of juvenile cuttlefish following short-term exposure to CO2-enriched seawater. The predation success rate decreased with the elevation in CO2 concentration. In the CO2 treatment groups, cuttlefish spent more time in the dark zone and the average swimming speed and total swimming distance significantly decreased. The structure of the retina and cuttlebone was affected by seawater acidification. Moreover, apoptotic cells were significantly increased in the eyes. In the wild, the impairment of the eye and cuttlebone may decrease the predation ability of juvenile cuttlefish and negatively affect their ability to select a suitable habitat, which would be detrimental to its population.

Passive acoustic localization and tracking of Rice’s whales (Balaenoptera ricei) in the northeastern Gulf of Mexico

The endangered Rice’s whale (Balaenoptera ricei) is endemic to the Gulf of Mexico and is also the Gulf’s only resident baleen whale. Limited knowledge of this species’ ecology combined with the high industrialization of this region raises serious conservation concerns. As part of an ongoing project to study the Rice’s whale in its core habitat, an array of moored passive acoustic monitoring sites has been near-continuously deployed in the northeastern Gulf of Mexico since May 2021. While detecting Rice’s whale calls in these data provides valuable insight into the species’ spatiotemporal distribution, further analyses to localize and track individual whales would allow better characterization of their acoustic behavior and movement patterns, possibly allowing for density estimation. Here, we present a method for automated passive acoustic localization and tracking of calling Rice’s whales. The two key components of this approach are (1) the use of opportunistic sound sources to time-synchronize recordings across sites given clock-drift between acoustic recorders and (2) the implementation of automatic multi-target tracking techniques based on the Gaussian mixture probability hypothesis density filter. Analyses of the first four months of data show potential for measuring basic behavioral parameters such as calling rate, source level, and average swim speed.