Study on the mud swimming motion of Paramisgurnus dabryanus

In the context of the rapid development of bionic technology, inspired by the swimming behavior of fish, a variety of robotic fish have been designed and applied to different underwater works and even military applications. However, in some operations, such as detection and salvage, vehicles need to travel under mud, a medium that is different from fluids. This complicating factor put higher requirements on robotic fish design. In this study, Paramisgurnus dabryanus, a fish species adept at swimming into the mud, was taken as a research object to investigate its profile and mud swimming behavior. First, a three-dimensional (3D) image scanner is used for profile scanning to acquire the point cloud data of the profile features of the loach. After modification, data coordinate points are extracted and used to fit the profile curve of loach and build geometric and mathematical models by means of Fourier function fitting. The next step includes the analysis of the motion of loach, determination of main parameters of the wave equation, and establishment of the fish body wave curve of a loach in the swimming using MATLAB software. Saturated mud having a water content of 37% is adopted as an environmental medium to numerically simulate the swimming behavior in mud, identifying the distribution of vortex path, and velocity field of loach’s motion. The rationality of simulation results is verified by the loach mud swimming test, and the simulating results agree well with the experimental data. This study lays a preliminary foundation for the outer contour design of the robotic fish operating under mud and aims to carry out the drag reduction and accelerating design of the robotic fish. The robotic loach may be applied in fishery breeding, shipwreck salvage operations, and so on.

Lateral Line Ablation by Toxins Results in Distinct Rheotaxis Profiles in Fish

Zebrafish lateral line is an established model for hair cell organ damage, yet few studies link mechanistic disruptions to changes in biologically relevant behavior. We used larval zebrafish to determine how damage via ototoxic chemicals impact rheotaxis. Larvae were treated with CuSO4 or neomycin to disrupt lateral line function then exposed to water flow stimuli. Their swimming behavior was recorded, and DeepLabCut and SimBA software were used to track movements and classify rheotaxis behavior. Lateral line-disrupted fish performed rheotaxis, but they swam greater distances, for shorter durations, and with greater angular variance than controls. Further, spectral decomposition analyses demonstrated that lesioned fish exhibited toxin-specific behavioral profiles with distinct fluctuations in the magnitude, timing, and cross-correlation between changes in linear and angular movements. Our observations support that lateral-line input is needed for fish to perform rheotaxis efficiently in flow and reveals commonly used lesion methods have unique effects on behavior.

Signals from predators, injured conspecifics, and pesticide modify the swimming behavior of the gregarious tadpole Rhinella dorbignyi (Anura: Bufonidae)

Tadpoles detect chemical signals released from predators and conspecifics, and those present in the environment, and adjust their behavioral responses. This study evaluated the swimming activity of Rhinella dorbignyi (Duméril and Bibron, 1941) tadpoles exposed to chemical signals, including cues from a predator fish Synbranchus marmoratus Bloch, 1975 and an injured conspecific; sublethal concentration of insecticide cypermethrin; and their combination. Swimming behavior (total distance moved, average speed, global activity, number of contacts between tadpoles) was evaluated in an individual (1) and groups of different size (3, 5, 7 and 10 tadpoles) using a video-tracking software tool. Predator exposure modified behavioral parameters, reducing encounters with predators and, therefore, mortality. Total distance moved and average speed increased in trials involving 1 tadpole and 3 interacting tadpoles exposed to injured conspecifics, whereas global activity increased in all group sizes, showing that gregarious tadpoles may be affected by alarm cues and their behavior may be disrupted. The insecticide treatments (alone and combined) increased parameters in all group sizes, causing hyperactivity due to its neurotoxic effect. The different responses observed after exposure to alarm cues and environmental signals in the different group sizes modified the normal behavior and the ecological dynamics of gregarious tadpoles.

Three-dimensional tracking of the ciliate Tetrahymena reveals the mechanism of ciliary stroke-driven helical swimming

Helical swimming in free-space is a common behavior among microorganisms, such as ciliates that are covered with thousands hair-like motile cilia, and is thought to be essential for cells to orient directly to an external stimulus. However, a direct quantification of their three-dimensional (3D) helical trajectories has not been reported, in part due to difficulty in tracking 3D swimming behavior of ciliates, especially Tetrahymena with a small, transparent cell body. Here, we conducted 3D tracking of fluorescent microbeads within a cell to directly visualize the helical swimming exhibited by Tetrahymena. Our technique showed that Tetrahymena swims along a right-handed helical path with right-handed rolling of its cell body. Using the Tetrahymena cell permeabilized with detergent treatment, we also observed that influx of Ca2+ into cilia changed the 3D-trajectory patterns of Tetrahymena swimming, indicating that the beating pattern of cilia is the determining factor in its swimming behavior.

Development and Evaluation of a Chinook Salmon Smolt Swimming Behavior Model

Hydrologic currents and swimming behavior influence routing and survival of emigrating Chinook salmon in branched migratory corridors. Behavioral particle-tracking models (PTM) of Chinook salmon can estimate migration paths of salmon using the combination of hydrodynamic velocity and swimming behavior. To test our hypotheses of the importance of management, models can simulate historical conditions and alternative management scenarios such as flow manipulation and modification of channel geometry. Swimming behaviors in these models are often specified to match aggregated observed properties such as transit time estimated from acoustic telemetry data. In our study, we estimate swimming behaviors at 5 s intervals directly from acoustic telemetry data and concurrent high-resolution three-dimensional hydrodynamic model results at the junction of the San Joaquin River and Old River in the Sacramento-San Joaquin Delta, California. We use the swimming speed dataset to specify a stochastic swimming behavior consistent with observations of instantaneous swimming. We then evaluate the effect of individual components of the swimming formulation on predicted route selection and the consistency with observed route selection. The PTM predicted route selection fractions are similar among passive and active swimming behaviors for most tags, but the observed route selection for some tags would be unlikely under passive behavior leading to the conclusion that active swimming behavior influenced the route selection of several tagged smolts.

Fluoxetine can make marine organisms unhappy: a study on the sub-lethal effects on marine invertebrates

The environmental effects caused by selective serotonin reuptake inhibitor drugs have been investigated for marine organisms and coastal ecosystems but are scarce in neotropical organisms. This investigation aimed to evaluate the sublethal effects of fluoxetine on the embryonic development of the sea urchin Echinometra lucunter and the survival and swimming behavior of the brine shrimp Artemia sp. The organisms were exposed to four different concentrations of fluoxetine (30, 300, 3000 and 30000 ng L-1) and to a negative control (filtered seawater), following the respective standard testing protocols. We verified a significant reduction of the embryos development to pluteus larvae, starting from 3000 ng L-1 (54.0±10.9% normal larvae), in comparison with the controls (83.5±3.1%). The non-observed effect concentration (NOEC) was estimated at 300 ng L-1, and the lowest observed effect concentration (LOEC) was 3000 ng L-1. In the behavior tests with Artemia sp, no significant adverse effects were reported for mobility, swimming speed and inactivity time. These results show that Fluoxetine can interfere on the development of species like the sea urchin E. lucunter, but short term exposure did not affected the swimming behavior of the brine shrimp Artemia sp. Fluoxetine presents thus a potential to affect marine biota and disrupt the equilibrium of the coastal ecosystems.

Research on Whipping and Jetting Combined Swimming Behavior of Solen strictus Gould

Solen strictus Gould are mainly cave dwellers, using their axe feet to dig caves. The Solen strictus Gould also exhibit escape-swimming behavior when food, environment, and so on changes. In this paper, Solen strictus Gould were captured on a high-speed camera as they escaped, and it was found that the Solen strictus Gould whipped while the water spout between the axe foot and the mantle sprayed water outwards. The combined propulsion of these two methods allows the Solen strictus Gould to advance rapidly in a short time. It is calculated that the swimming speed of razor clams is positively correlated with their size and that the adult Solen strictus Gould can travel up to 12 times their body length per second. This study enriches the data on the behavioral characteristics of Solen strictus Gould and is of interest regarding Solen strictus Gould in artificial farming, marine fishing, offshore ecological restoration, and underwater bionic robot development.