Comparative vulnerability of Indosylvirana temporalis and Clinotarsus curtipes (Anura: Ranidae) tadpoles to water scorpions: importance of refugia and swimming speed in predator avoidance

The comparative vulnerability of two co-existing tadpole species (Indosylvirana temporalis and Clinotarsus curtipes) to their common predator, water scorpions (Laccotrephes sp.; Hemiptera: Nepidae), and the importance of refugia in predator avoidance were studied in the laboratory. In a total of 60 experimental trials, 10 tadpoles each of I. temporalis and C. curtipes of comparable body sizes were exposed to water scorpions (starved for 48 h). Thirty trials included refugia while 30 did not. The results of this study showed that in both the absence and the presence of refugia C. curtipes tadpoles fell prey to water scorpions more frequently than I. temporalis tadpoles. A main difference between the two species is the speed of swimming; Vmax of C. curtipes (24.73 cm/s) tadpoles is lower than that of I. temporalis (30.78 cm/s) tadpoles. This is likely to be the reason why more C. curtipes tadpoles were preyed upon than were I. temporalis tadpoles. Predation risk of tadpoles of both species was affected significantly by the presence of refuge sites. The vulnerability of both tadpole species was lower where refuge sites were available. The present study clearly shows that I. temporalis tadpoles avoid predation by water scorpions more effectively than do C. curtipes tadpoles.

Active tail flexion in concert with passive hydrodynamic forces improves swimming speed and efficiency

Fish typically swim by periodic bending of their bodies. Bending seems to follow a universal rule; it occurs at about one-third from the posterior end of the fish body with a maximum bending angle of about $30^{\circ }$ . However, the hydrodynamic mechanisms that shaped this convergent design and its potential benefit to fish in terms of swimming speed and efficiency are not well understood. It is also unclear to what extent this bending is active or follows passively from the interaction of a flexible posterior with the fluid environment. Here, we use a self-propelled two-link model, with fluid–structure interactions described in the context of the vortex sheet method, to analyse the effects of both active and passive body bending on the swimming performance. We find that passive bending is more efficient but could reduce swimming speed compared with rigid flapping, but the addition of active bending could enhance both speed and efficiency. Importantly, we find that the phase difference between the posterior and anterior sections of the body is an important kinematic factor that influences performance, and that active antiphase flexion, consistent with the passive flexion phase, can simultaneously enhance speed and efficiency in a region of the design space that overlaps with biological observations. Our results are consistent with the hypothesis that fish that actively bend their bodies in a fashion that exploits passive hydrodynamics can at once improve speed and efficiency.

Experimental sound exposure modifies swimming activities and increases food handling error in zebrafish (Danio rerio)

Anthropogenic sound is currently recognized as a source of environmental pollution in terrestrial and aquatic habitats. Elevated sound levels may cause a broad range of impacts on aquatic organisms among taxa. Sound is an important sensory stimulus for aquatic organisms and it may cause fluctuations in stress-related physiological indices and in a broader extent induce behavioural effects such as driving as a distracting stimulus, masking important relevant acoustic signals and cues in a range of marine and freshwater species. However, sound exposure may also induce changes in swimming activities, feed efficiency and productivity of available food sources in fish. Here, we experimentally tested sound effects on swimming activities and foraging performance in thirty adult Zebrafish (Danio rerio) individually in captivity. We used adult zebrafish and water flea (Daphnia magna) as model predator prey, respectively. We also used four sound treatments with different temporal patterns (all in the same frequency range and moderate exposure level). Our results constitute strong evidence for clear sound-related effects on zebrafish behaviour. All sound treatments induced a significant increase in the number of startle response, brief and prolonged swimming speed for zebrafish (P<0.05). Zebrafish reached to the baseline swimming speed after 60 seconds in all treatments. We found partially brief and prolonged sound effects on spatial distribution of zebrafish; Although we did not find any significant sound-related behavioural changes for horizontal spatial displacement in all treatments (P>0.05), zebrafish swam significantly more in the lower layer of the fish tank except irregular intermittent 1:1-7 in brief sound exposure (P<0.05). The results of foraging performance showed that food discrimination error was low for the zebrafish and unaffected by sound treatments (P>0.05). However, food handling error was affected by sound treatments; all treatments caused a rise in handling error (P<0.001). This study highlights the impact of sound on zebrafish swimming activities, and that more attacks are needed to consume the same number of prey items under noisy conditions.

Influence of Geomagnetic Disturbances at Different Times of Day on Locomotor Activity in Zebrafish (Danio Rerio)

The influence of magnetic fields and natural geomagnetic storms on biological circadian rhythms are actively studied. This study reveals an impact of local natural perturbations in the geomagnetic field that occurred at different times of the day on circadian patterns of locomotor activity of zebrafish. A decrease in zebrafish swimming speed was observed during the geomagnetic disturbances before or after the fluctuations of diurnal geomagnetic variation. However, if the geomagnetic perturbations coincided with the fluctuations of diurnal geomagnetic variation, the decrease in zebrafish swimming speed was insignificant. This result suggests that the biological effects of geomagnetic disturbances may depend on synchronization with the diurnal geomagnetic variation. It implies that the previously published correlations between geomagnetic activity and medical or biological parameters could result from a disruption in circadian biorhythms.

A comparison of two methods for estimating critical swimming speed (UCRIT) in larval fathead minnows: the laminar flow assay and the spinning task assay

Critical swimming performance (UCRIT) is considered a good predictor of swimming capabilities in fish. To estimate UCRIT, a fish is exposed to an incrementally-increasing laminar flow of water until it cannot maintain its position against the current. The spinning task assay has been proposed as an alternative method to traditional laminar flow methods; however, these methods have not been directly compared. Thus, the goal of this study was to determine whether the spinning task assay is a suitable alternative to traditional laminar flow assays. To that end, the performance of fathead minnows in each assay was compared at three time points (14, 19 and 24 days post fertilization, dpf). In 14 dpf fish, UCRIT estimates were similar regardless of the assay used. However, at 19 and 24 dpf, UCRIT estimates derived from the two assay types were significantly different. This indicates that the assays are not equivalent to one another and that the spinning task assay is not a suitable alternative to the laminar flow assay for the determination of UCRIT.

PENGARUH FAST INTERVAL TRAINING (FIT) TERHADAP HASIL KECEPATAN RENANG GAYA BEBAS 100 METER PADA ATLET K.U II LUMBA-LUMBA SWIMMING CLUB BINJAI TAHUN 2021

This research was carried out at the Swimming Club Binjai Dolphins at the Tirta Raerim Mencharm swimming pool in the Peacock Meadows, North Sumatra. held on November 10 to January 28, 2021 for 8 weeks with a frequency of 2 times a week.This study aims to determine the effect of fast interval training (FIT) on the results of the 100 meter freestyle swimming speed for the K.U II Dolphin Swimming Club Binjai. The research method used in this study is an experimental method with a sample of 8 people with a purposive sampling research design. Then the sample did an initial test (pre-test), namely with a 100-meter swimming test, then the sample was given Fast Interval Training (FIT) training then after 8 weeks of programmed exercise the sample did a final test (post-test).The results of the analysis of the hypothesis, that there is a significant effect of fast interval training (FIT) training on the results of the 100 meter freestyle swimming speed for the K.U II Dolphin Swimming Club Binjai athletes. 2021 year. The results of the t-test obtained tcount = 0.3096 and t-table = 0.258. At the real level = 0.05 then t-count > t-table. Based on the hypothesis testing criteria, HO is rejected and Ha is accepted. Thus it can be concluded that there is a significant effect of Fast Interval Training (FIT) on the results of the 100 meter freestyle swimming speed for the KU II Lumba-lumba Swimming Club Binjai athletes 2021.

A speed measurement method for underwater robots using an artificial lateral line sensor

Underwater robot technology has made considerable progress in recent years. However, due to the harsh environment and noise in the flow field near the underwater robots, it is difficult to measure some basic parameters, including swimming speed. The traditional speed measurement methods for underwater robots have the disadvantages of being limited by the environment and bulky. In order to overcome these shortcomings, an artificial lateral line sensor based on cantilever structure was developed in this paper. According to the deformation of cantilever beam under water impact, the swimming speed of underwater robots can be measured. In addition, an "end-to-end" calibration algorithm was proposed to calibrate the artificial lateral line sensor in the noisy environment, avoiding the complicated noise modeling and filter design process. To reduce the risk of overfitting, a hybrid loss function based on physical model was adopted. Compared with the classical calibration method, our method can reduce the error by 47.8%. Our sensor achieved an average absolute error of 0.07897 m/s, and can measure water speed up to 3 m/s.

The relationship of arm muscle strength, limb muscle explosive and movement coordination with swimming speed bracelet on students of physical education, health and recreation

This study aims to determined the relationship arm muscle strength, limb muscle explosive and movement coordination with coordination with swimming speed bracelet on students PENJASKESREK at Serambi Mekkah University. The population in this studied were all student PENJASKESREK at Serambi Mekkah University. Based on the purposive sampling technique, the samples totaling 30 students who had passed the T.P. Basic Swimming and T.P. Advanced Swimming. Based on the results of data analysis, it was found that arm muscle strength gave a relationship of 0.52 to the speed of breaststroke swimming in students, limb muscle explosive gave a relationship of 0.44 to the speed of breaststroke swimming to students, movement coordination gave a relationship of 0,42 with the speed of breaststroke swimming to students. The concluded that arm muscle strength, limb muscle explosive and movement coordination were related by 0.79 with the breaststroke swimming speed on Students at Serambi Mekkah University. So the hypothesis that the author proposed was accepted as true.