Swimming Ability Research Articles

Swimming ability and flagellar motility of sperm packets of the volvocine green alga Pleodorina starrii.

Eukaryotic flagella collectively form metachronal waves that facilitate the ability to cause flow or swim. Among such flagellated and planktonic swimmers, large volvocine genera such as Eudorina, Pleodorina and Volvox form bundles of small male gametes (sperm) called "sperm packets" for sexual reproduction. Although these sperm packets reportedly have flagella and the ability to swim, previous studies on volvocine motility have focused on asexual forms and the swimming characteristics of sperm packets remain unknown. However, it is important to quantify the motility of sperm packets and sperm in order to gain insights into the significance of motility in the sexual reproduction of planktonic algae. In this study, we quantitatively described the behavior of three flagellated forms of a male strain of Pleodorina starrii-asexual colonies, sperm packets, and single dissociated sperm-with emphasis on comparison of the two multicellular forms. Despite being smaller, sperm packets swam approximately 1.4 times faster than the asexual colonies of the same male strain. Body length was approximately 0.5 times smaller in the sperm packets than in asexual colonies. The flagella from sperm packets and asexual colonies showed asymmetric waveforms, whereas those from dissociated single sperm showed symmetric waveforms, suggesting the presence of a switching mechanism between sperm packets and dissociated sperm. Flagella from sperm packets were approximately 0.5 times shorter and had a beat period approximately twice as long as those from asexual colonies. The flagella of sperm packets were densely distributed over the anterior part of the body, whereas the flagella of asexual colonies were sparse and evenly distributed. The distribution of flagella, but not the number of flagella, appear to illustrate a significant difference in the speeds of sperm packets and asexual colonies. Our findings reveal novel aspects of the regulation of eukaryotic flagella and shed light on the role of flagellar motility in sexual reproduction of planktonic algae.

Scaphitid ammonites from the lower Maastrichtian of Nahoryany (western Ukraine) and discussion on the origin of Hoploscaphites constrictus

Abstract The lower Maastrichtian (Upper Cretaceous) section at Nahoryany, south of Lviv (western Ukraine), has been known as a rich source of fossils since 1843. However, the section is not available since a long time ago and fossils collected from it can only be studied in museum collections. In the present paper, ammonites of the scaphitid genus Hoploscaphites are studied based on Nahoryany material, comprising Hoploscaphites pumilus, H. constrictus and H. sp. Specimens from Nahoryany in museum collections lack data on their provenance level within the section so it cannot be determined whether or not they occurred together or formed a succession; data on inoceramid bivalves indicate the presence of two successive zones at Nahoryany. Some specimens from Nahoryany here referred to as H. pumilus are similar to the controversial H. constrictus anterior from the lower Maastrichtian of Poland. This morphology suggests an ancestor–descendant relationship between H. pumilus and H. constrictus, a common species once considered as an informal index for the Boreal Maastrichtian in Europe. The inferred evolutionary transition from H. pumilus to H. constrictus was towards a less robust, recoiled shell, which would have enhanced the horizontal swimming ability and manoeuvrability of these cephalopods. Recoiling trends occurred in several lineages of Late Cretaceous scaphitids.

Morphology, Phylogeny, and Evolution of the Rarely Known Genus Admetella McIntosh, 1885 (Annelida, Polynoidae) with Recognition of Four New Species from Western Pacific Seamounts

The polynoid genus Admetella constitutes a deep‐sea assemblage of polychaetes, notable for their large bodies adorned with antennal scales positioned dorsally to the bases of lateral antennae. Furthermore, the genus exhibits swimming proficiencies facilitated by elongated parapodia and flattened chaetae. Despite the frequent encounters with Admetella members during various deep‐sea explorations, a substantial gap in our comprehension of their diversity, phylogeny, and evolutionary trajectories still exists. Our thorough morphological and phylogenetic investigations of specimens obtained from three seamounts located in the tropical western Pacific have unveiled six species belonging to the genus Admetella, four of these being newly identified as Admetella multiseta sp. nov., A. levensteini sp. nov., A. nanhaiensis sp. nov., and A. undulata sp. nov. The other two species of Admetella remain unidentifiable at the species level due to the loss of crucial details. Our phylogenetic analysis, grounded on 13 mitochondrial protein‐coding genes and the inclusion of 12S, 16S, 18S, 28S rRNA, and ITS1–ITS2 genes, substantiates the monophyly of Admetella. Admetella is positioned at an intermediate node within the phylogenetic tree, situated between representative shallow‐water and deep‐sea subfamilies. The independent evolution of antennal scales within Admetella among polynoids constitutes a synapomorphy for this genus. Ancestral state reconstruction (ASR) analyses suggest that deep‐sea polynoids evolved from shallow‐water ancestors that possessed lateral antennae, which were subsequently lost in members inhabiting extreme marine environments, such as deep‐sea hydrothermal vents and anchialine caves. The analysis further implicates that swimming ability independently evolved at least four times within the Polynoidae family.

Consumption of Policosanol (Raydel®) Improves Hepatic, Renal, and Reproductive Functions in Zebrafish: In Vivo Comparison Study among Cuban, Chinese, and American Policosanol.

The current study compared three policosanols from Cuba (sugarcane, Raydel®, policosanol (1), China (rice bran, Shaanxi, policosanol (2), and the USA (sugarcane, Lesstanol®, policosanol (3) in the treatment of dyslipidemia and protection of the liver, ovary, and testis in hypercholesterolemic zebrafish. After twelve weeks of supplementation of each policosanol (PCO, final 0.1% in diet, w/w) with a high cholesterol diet (HCD, final 4%, w/w), the Raydel policosanol (PCO1) group showed the highest survivability, approximately 89%. In contrast, Shaanxi policosanol (PCO2) and Lesstanol policosanol (PCO3) produced 73% and 87% survivability, respectively, while the HCD alone group showed 75% survivability. In the 12th week, the PCO1 group demonstrated the most modest increase in body weight along with significantly lower levels of total cholesterol (TC) and triglycerides (TG) in comparison to the HCD control group. Additionally, the PCO1 group exhibited the highest proportion of high-density lipoprotein (HDL)-cholesterol within TC. Notably, the PCO1 group displayed the lowest level of aspartate aminotransferase and alanine aminotransferase, minimal infiltration of inflammatory cells, reduced interleukin (IL)-6 production in the liver, a notable decline in reactive oxygen species (ROS) generation and mitigated fatty liver changes. HCD supplementation induced impairment of kidney morphology with the greatest extent of ROS production and apoptosis. On the other hand, the PCO 1 group showed a remarkably improved morphology with the least ROS generation and apoptosis. Within the ovarian context, the PCO1 group exhibited the most substantial presence of mature vitellogenic oocytes, accompanied by minimal levels of ROS and apoptosis. Similarly, in the testicular domain, the PCO1 group showcased optimal morphology for spermatogenesis, characterized by the least interstitial area and diminished production of ROS in testicular cells. At week 8, the PCO1 group showed the highest egg-laying ability, with around 244 eggs produced per mating. In contrast, the HCD alone, PCO2, and PCO3 groups showed significantly lower egg-laying ability (49, 59, and 86 eggs, respectively). The embryos from the PCO1 group exhibited the highest survivability with the fastest swimming ability and developmental speed. These results suggest that PCO1 consumption significantly enhanced the reproduction system, egg-laying ability, and embryo survivability. In conclusion, among the three policosanols, Cuban (Raydel®) policosanol had the strongest effect on survivability, improving dyslipidemia, liver protection, kidney, ovary, and testis with a restoration of the cell morphology, and the least ROS production and apoptosis-induced by HCD supplementation.

The role and molecular mechanism of flgK gene in biological properties, pathogenicity and virulence genes expression of Aeromonas hydrophila

Aeromonas hydrophila is a highly pathogenic aquatic resident bacterium that can cause co-morbidity in aquatic animals, waterfowl, poultry, and humans. Flagellum is the motility organ of bacteria important for bacterium tissue colonization and invasion. The flgK gene encodes a flagellar hook protein essential for normal flagellar formation. In order to explore the role of flgK in A. hydrophila, a flgK gene mutant strain of A. hydrophila (∆flgK-AH) was constructed using an efficient suicide plasmid-mediated homologous recombination method, and gene sequencing confirmed successful mutation of the flgK gene. The biological properties, pathogenicity and virulence genes expression were compared. The results showed that there was no significant difference in the growth, hemolytic, and swarming abilities, but the swimming and biofilm formation abilities of ∆flgK-AH were significantly reduced and the transmission electron microscope (TEM) results showed that the ∆flgK-AH strain did not have a flagellar structure. The median lethal dose (LD50) value of the ∆flgK-AH in Carassius auratus was 1.47-fold higher than that of the wild-type strain (WT-AH). The quantitative real-time PCR results showed that only the expression level of the lapA gene was up-regulated by 1.47 times compared with the WT-AH, while the expression levels of other genes were significantly down-regulated. In conclusion, flgK gene mutant led to a decline in the pathogenicity possibly by reducing swimming and biofilm formation abilities, these biological properties might result from the down-regulated expression of flagellate and pilus-related genes.

Aggregation of zooplankton in a Stommel Retention Zone in a laboratory model of Langmuir circulation

AbstractLangmuir circulation is a common form of surface turbulence comprising a series of counterrotating horizontal vortex pairs. Upwellings and downwellings in Langmuir circulation may suspend and trap passive particles or active swimmers like zooplankton in regions known as Stommel Retention Zones. For zooplankton, Stommel Retention Zone formation depends on flow speed and animal swimming speed and direction. Here we explore this biophysical interaction using Daphnia magna in a laboratory model of Langmuir Circulation. The phototactic daphniids were induced to perform different levels of upwards swimming (mimicking diel vertical migration) via constant or intermittent illumination. Some daphniids were additionally exposed to chemically dispersed crude oil, which impaired swimming. We characterized the swimming speed and direction, trajectories, and spatial distribution of daphniids in still water and in response to Langmuir circulation‐like flows of various strengths. In still water, constantly illuminated and oil‐exposed daphniids swam upwards more often than intermittently illuminated animals. Greater levels of upwards swimming in still water corresponded to stronger daphniid aggregations in the downwelling when a Langmuir Circulation‐like flow was present. However, at flow speeds exceeding their swimming abilities, daphniids were generally advected with the flow and uniformly distributed, an effect particularly evident for the weakly‐swimming oil‐exposed daphniids. An individual‐based model was also used to investigate the effects of active swimming vs. passive behavior and of swimming direction on Langmuir circulation‐associated aggregations. Our study of zooplankton Stommel Retention Zones generated in a laboratory facility offers insight into how and when Langmuir circulation‐associated plankton aggregations may occur in the field.

Modelling assessment of how small-scale vertical movements of infectious sea lice larvae can affect their large-scale distribution in fjordic systems

Sea lice are ectoparasites that can be found in high numbers in and around salmon farms, where they are a threat to fish health and can induce high aquacultural costs. Large numbers of suitable hosts facilitate the infection and subsequent release of their planktonic larvae in the surrounding environment where they can potentially infect wild salmonids, including migrating juvenile fish (smolts). Investigating sea lice spatial distribution is generally done using coupled hydrodynamic and particle tracking models. The quality of these numerical tools is critical to identify areas of higher infection risk to valuable wild salmon populations and thus support sustainable salmon aquaculture. While the transport of salmon lice is mainly affected by physical processes, biological behaviours such as vertical swimming can also play an important role. However, a review of previous sea lice studies shows no clear consensus on their swimming abilities and the parameters implemented in sea lice dispersion modelling. Here, we focus on the Diel Vertical Migration (DVM) behaviour, a vertical migration that sea lice perform within a daily cycle. Our sensitivity study of the infectious copepodid phase of sea lice highlights how their retention potential and spatial distribution within a water body are affected by their vertical swimming velocity and maximum swimming depth. In a fjordic system (Loch Linnhe on the West Coast of Scotland), the vertical position of sea lice can affect their horizontal trajectory due to the two-layer exchange flow of the estuarine circulation. At the surface, transport is mainly due to the wind driven circulation, and the residual seaward current. Lower in the water column, the saltier shelf water is drawn into the sea loch. This can potentially increase the retention of sea lice if they dive deep enough to reach those opposing subtidal currents. Therefore, lack of confidence in sea lice DVM parameterisation may introduce inaccuracy in modelled sea lice distribution. Effective sea lice management in aquaculture would benefit from more observational data like farm sea lice count, sea lice swimming laboratory observations, field observation of sea lice vertical distribution and accurate sea lice quantification in the field. This would help to reduce uncertainties derived from sea lice vertical swimming behaviour parameterisation in lice dispersal models.

Co-exposure of nanoplastics and arsenic causes neurotoxicity in zebrafish (Danio rerio) through disrupting homeostasis of microbiota–intestine–brain axis

Nanoplastics (NPs) and arsenic (As) are toxic pollutants prevalent on the earth and have gained considerable attention in recent decades. Although numerous studies reported NPs and As can cause neurotoxicity there are still significant knowledge gaps in illustrating their combined toxicity and its mechanism. In this study, the co-exposure of environmentally relevant concentrations of NPs and As caused neurobehavioral toxicity in zebrafish, as evidenced by reduced swimming ability, anxiety and impaired short-term learning memory. Potentially, its toxicity mechanism is through disrupting the homeostasis of microbiota-intestine-brain axis in zebrafish. Specifically, the co-exposure reduced the 5-hydroxytryptamine (5-HT) production in intestine, which led to lower levels of 5-HT transported by the blood circulation to the brain. Ultimately, neurobehavior was adversely affected by the reduced binding of 5-HT to its receptors. Intestine, the primary source of 5-HT, its impaired health (aggravation in oxidative stress, mitochondrial damage and histopathological alterations) induced the dysregulation in the 5-HT system, which may be induced by the increased accumulation of As in the intestine by the co-exposure. Besides, the reduced 5-HT levels were correlated with decreased Firmicutes and Protecbacteria and increased Actinobacteriota and Chloroflexi in intestines. Potentially, intestinal microbiota adversely regulates the intestine-brain axis by reducing SCFAs levels. Thus, the alteration of intestinal microbiota structure may be the other reason for the dysregulation of intestine-brain axis. In summary, co-exposure of NPs and As induced neurobehavior toxicity probably through disrupting the homeostasis of microbiota-intestine-brain axis. This study provides insights into assessing the environmental health risks of the pollution of NPs and As to aquatic organisms.

30 Does size matter? Effect of sperm morphometric characteristics on the motility and swimming ability in stallion sperm samples

30 Does size matter? Effect of sperm morphometric characteristics on the motility and swimming ability in stallion sperm samples

Interactive effects of total dissolved gas supersaturation and suspended sediment on the swimming abilities of two fish species

AbstractDischarged floods containing a large amount of suspended sediment (SS) can lead to total dissolved gas (TDG) supersaturation downstream of dams. The swimming ability of fish may be affected by TDG supersaturation and excessive SS. However, previous studies focused only on the separate effects of TDG and SS, ignoring their combined effects. In this study, juvenile rock carp and grass carp were selected to assess the interactive effects of TDG and SS on fish swimming ability. A totally crossed two‐factorial design (six TDG levels: 100%, 115%, 120%, 125%, 130% and 135%; four SS concentrations: 0, 50, 100 and 150 mg/L) was set, and the critical swimming speed (Ucrit) and the burst swimming speed (Uburst) were measured. The findings indicated that the swimming abilities (Ucrit and Uburst) of both fish species decreased with increasing TDG levels and SS concentrations. Separate exposure to TDG significantly decreased the swimming abilities of the two fish species, whereas separate exposure to SS decreased only the swimming abilities of juvenile grass carp. Juvenile rock carp exhibited weaker swimming abilities than juvenile grass carp in TDG‐supersaturated water. Additionally, the interaction between TDG and SS reduced the swimming abilities of juvenile rock carp and grass carp compared with a separate effect, but this reduction was significant only for the Ucrit of juvenile grass carp. This study demonstrates that TDG‐supersaturated water containing SS during flooding may result in fish failure through fishways.

The behavior of the Bacillus probiotic species under conditions of co-cultivation

Combining probiotic bacteria is a promising strategy to increase the effectiveness and avoid side effects of probiotic therapy. Bacteria that find themselves in a common environment are able to both change their properties and show new ones under the influence of each other. The change of colonization and antagonistic properties, which provide bacteria with competitive advantages in the development of new spaces, deserves special attention.
 The aim of this research was to study the features of the mutual influence of probiotic bacilli: B. clausii, B. coagulans and B. subtilis on growth, swimming and swarming motility when co-cultivated on agar media of different solidity.
 Materials and methods. The study used commercial strains of bacilli from three probiotic preparations: Enterogermina, Lactovit forte and Subalin. The ability of the studied species of bacilli to influence each other’s growth was investigated by the agar block method (using 1.5 % nutrient agar) and the spot-on-lawn assay (using 0.7 % nutrient agar). The study of the mutual influence on swimming and swarming activity was carried out when bacilli were cultivated on 0.25 % and 0.70 % tryptone agar, respectively. The diameters of swimming halos and migration swarms formed by monoand mixed cultures were measured, and the areas covered by them were compared. The phenotypes of the meeting of swarms formed by cultures spotted on the swarm plates at different locations were also investigated.
 Results. The studied probiotic species of the bacilli did not show a strong ability to inhibit each other’s growth. The B. clausii culture had no inhibitory effect, and the B. coagulans culture demonstrated a moderate inhibitory influence on the growth of the other two species of bacilli when using both diffusion methods. The B. subtilis culture showed moderate or weak inhibitory activity against the B. clausii culture and weak or no inhibitory activity against the B. coagulans culture using the agar block method or spot-on-lawn assay, respectively. The B. coagulans + B. subtilis, B. clausii + B. coagulans and B. clausii + B. subtilis mixed cultures showed moderate, weak and no inhibitory activity against third cultures, respectively. The studied species of bacilli showed different swimming ability and swarming potential as well as the ability to influence each other’s motility. Swimming halos formed by the B. clausii + B. subtilis and B. clausii + B. сoagulans + B. subtilis mixed cultures covered significantly larger plate areas than the swimming halos formed by each culture separately during the same cultivation time. The highest swarming potential was observed in B. coagulans culture and B. cla usii + B. coagulans + B. subtilis mixed culture. The studied bacilli did not show the ability to merge swarms, but, on the contrary, their swarms at the point of contact formed visible “boundary” or “intermediate” lines, demonstrating the ability to identify nonself.
 Conclusions. The obtained results indicate the ability of the probiotic species of bacilli: B. clausii, B. coagulans and B. subtilis to mutually influence growth, swimming and swarm motility. The highest indicators of swimming and swarming of the triple mixed culture indicate an increase in the colonization potential of the studied bacilli when they are combined. The hypothesis of mutual induction of inhibitory compounds production by bacilli, which may increase the overall antagonistic potential of the triple mixed culture, is subject to further confirmation.

Five years on the road

We have reached our fifth edition, marking five years of disseminating information about the mammals of Ecuador. The cover of this edition portrays the long-tailed weasel (Neogale frenata), one of the smallest carnivores of the continent and a little-known species in Ecuador. The cover symbolizes our central theme, as we include three publications related to this species in this edition. The first is the report of a confirmed record in the southern region of the province of Esmeraldas, which opens the debate on whether this species, which is typically Andean in this country, may naturally inhabit the humid forests of the Chocó. This hypothesis had been mentioned previously (Parker III & Carr, 1992) but had not been confirmed. To complement this topic, we add two scientific notes that contribute to our knowledge of the natural history of Neogale frenata. One deals with its swimming ability, a behavior that had only been documented in the northern part of its distribution, in North America (Sheffield & Thomas, 1997); the other provides details of an attack on a poultry farm, a behavior previously attributed to this species but poorly documented in the scientific literature. This edition also brings two contributions to the little-known natural history of the country's bats. One is the first catalog of ectoparasites (Diptera: Streblidae and Nycteribiidae) found on 22 bat species in coastal Ecuador. The other is a note on the capture of a sucker bat (Thyroptera tricolor) in a web of Eriophora sp. (Araneae: Araneidae) in Yasuní National Park, in the Ecuadorian Amazon. We also include an article on research trips designed for listening to humpback whales (Megaptera novaeangliae) in the southeastern Pacific region and two articles that contribute to the knowledge of the species richness of two little-studied areas: the Cordillera Chongón Colonche, in the central-coastal region of the country, and the Reserva Biológica Tapichalaca, in the province of Zamora Chinchipe, in southeastern Ecuador. This fifth issue of Mammalia aequatorialis is the most extensive that we have published since the birth of the journal, motivating us to continue with the belief that we will be able to publish two issues per year in a short time. Thank you very much for joining us during these first five years. Diego G. Tirira Editor-in-chief

Effects of hazards and sensation-seeking on intermediate swimming college students' hazard perceptions.

According to the Global Report on Drowning: Preventing a Leading Killer and Preventing Drowning: An Implementation Guide, two documents released by the World Health Organization in 2014 and 2017, respectively, 372,000 people drown each year globally (approximately 42 per hour), half of whom are below 25 years old. Chinese adolescents aged 18-24 years are the main victim group. Intermediate swimming college students are more susceptible to risk-taking behavior and drowning while swimming. In particular, college students with high-sensation-seeking levels have greater confidence in their swimming ability. Consequently, they tend to overestimate their skills and pursue exciting experiences while underestimating or ignoring the risk factors in the situation. The scores of college students in sensation-seeking show a significant positive correlation with highly risky swimming behavior. However, the correlation with the reaction time to hazards is unclear. In this study, using previous theories, the sensation-seeking scale, and the measurement of the reaction time to hazards, we clearly explain why "college students with higher levels of sensation-seeking have a higher risk of drowning." We examined the reaction time to hazards and eye movement data of intermediate swimming college students with different sensation-seeking levels, while controlling the obviousness of hazards in the videos for the experiment. We utilized 16 videos of students swimming as experimental stimuli and employed a mixed experimental design of 2 (sensation-seeking: high, low)×2 (hazard type: obvious hazard, hidden hazard). Sensation-seeking, the between-subjects variable, was categorized into two levels (high and low). The hazard type, the within-subjects variable, was also divided into two categories (obvious and hidden). We analyzed the disparities in reaction time to hazards and eye-movement data between intermediate swimming college students with high (N=28) or low (N=28) levels of sensation-seeking. Intermediate swimming college students with high levels of sensation-seeking exhibited significantly longer reaction times to both obvious (F=6.251, p=.000<.001) and hidden (F=49.438, p=.000<.001) hazards compared to their low-sensation-seeking counterparts. The first fixation duration of intermediate swimming college students on obvious hazards was shorter than that on hidden hazards (F=13.596, p=.000<.001), and the average fixation duration of intermediate swimming college students with high levels of sensation-seeking on hidden hazards proved to be significantly shorter (F=5.498, p=.000<.001). High-sensation-seeking intermediate swimming college students exhibited longer reaction times to hidden hazards compared to their low-sensation-seeking peers. These findings indicate that a high-sensation-seeking tendency can result in delayed reaction times and a disregard for response measures among intermediate swimming college students.

Macroinvertebrates beta diversity and responses of functional traits to water environmental factors in the Qingyijiang River, China

AbstractThe diversity of functional traits of macroinvertebrates in freshwater ecosystems is one of the current research hotspots in the field of biodiversity. Understanding the functional trait composition of macroinvertebrates and their factors can make the study of watershed beta diversity and river ecological security patterns more effective. Based on two field surveys conducted in September 2020 and July 2021 in the Qingyijiang (QYJ) River, the longest tributary on the south bank of the lower Yangtze River in China, we explored the functional trait compositions of macroinvertebrates and relationships between functional traits and water environment factors using functional diversity indices, beta diversity decomposition, R‐mode linked to Q‐mode, and fourth‐corner analysis methods. Our results showed that water environmental factors affected the distribution of macroinvertebrates traits, and the degree of effect was reflected by the correlation between water environmental factors and the abundance of species traits. Physical factors like flow velocity and water depth were significantly correlated with biological traits of species such as body size and swimming ability. In counterparts, some nutrient indicators significantly affected species ecological traits, such as total phosphorus, ammonia nitrogen, and chemical oxygen demand, which affected species habits and functional feeding group traits. At the same time, we also found a high turnover rate between communities in the river, reflecting the strong dispersal ability of the species. This will be an important guide for the conservation of macroinvertebrates diversity in the river. Local governments can take measures such as conducting quarterly monitoring of macroinvertebrates species; restoring riparian vegetation; limiting hardening of riverbanks and dredging of rivers; controlling wastewater discharges from residential areas on both sides of the river; controlling the use of pesticides in agricultural lands, and so on. These will become the key directions for the conservation of macroinvertebrates diversity.

A wave-resolving modeling study of rip current variability, rip hazard, and swimmer escape strategies on an embayed beach

Abstract. Drownings due to rip currents are a major threat to beach safety. In this study a high-resolution Boussinesq model with a modified wave-resolving Lagrangian tracking module has been applied to a 2 km long embayed beach, Dadonghai of Sanya, Hainan Island, with the purpose of studying rip current variability, real-time rip hazard identification, and the optimal swimmer escape strategies. The beach stage evolves periodically at the study site and plays an important role in the long-term modulation of the occurrence and strength of rip currents according to the modeling. A series of tests are designed and confirm that rip current strength is closely related to wave properties and tidal levels. Spectral analysis of output time series at specific points shows that the modeled rip currents fluctuate on the orders of 1 and 10 min, which suggests the effects of wave-group-forced infragravity (IG) and very-low-frequency (VLF) motions. Rip hazard levels are defined by combining rip strength and its duration. An attempt to use the GPU-accelerated FUNWAVE-TVD (Total Variation Diminishing version of the Fully Nonlinear Boussinesq Wave Model) embedded with the spectral wave model WAM6-GPU (GPU version of the third-generation spectral wave model WAM Cycle 6) exhibits its capability to evaluate rip hazard levels in real time. One of the differences of the present study from previous works is that the random, wave-resolving tracking of virtual swimmers is performed with 1 m resolution to study beach safety strategies. The results demonstrate that multiple factors contribute to the survival of swimmers caught in the rip currents, including surf-zone bathymetry, rip strength, fine-scale flow patterns, the bather's position, and swimming ability. For weak-to-moderate rip currents and longshore currents, swim onshore consistently seems to be the most successful strategy across all the scenarios in this study. Higher surf-zone exit rates along Dadonghai beach are not favorable for stay afloat action, which puts swimmers at a higher risk of being expelled to deeper water. The effects of wave randomness of incoming wave trains and assignment of wave-following coefficients on Lagrangian tracking are also discussed.

Size-assortative mating of Buergeria buergeri (Anura: Rhacophoridae): breeding strategies for balancing fertilisation rate and swimming ability

Abstract Buergeria buergeri is a stream-breeding rhacophorid frog. The sexual dimorphism in body size is significant in this species, which might be advantageous for its movement within the stream in an amplected state. However, the fertilisation rate of egg masses decreases as the body size difference between both sexes in the amplectant pair increases because the distance between the cloacae increases. In this study, we examined the mating pattern of B. buergeri and the relationship between female/male SVL ratio in the amplectant pair and fertilisation rate, and the swimming ability within the stream. As a result, when the female/male SVL ratio was less than 1.45, the fertilisation rate reached a plateau (nearly 100%). However, the fertilisation rate decreased as the female/male SVL ratio increased when this ratio was greater than 1.45. Moreover, a significant positive correlation was observed between the female/male SVL ratio and swimming ability. These results suggest that there was a trade-off between fertilisation rate and swimming ability via the female/male SVL ratio. In the field, we observed a significant positive correlation between male and female SVLs in 16 amplectant pairs, with a mean female/male SVL ratio of 1.44. Our experimental results suggest that when the female/male SVL ratio is 1.44, the fertilisation rate is close to 100%, and the swimming ability can be maintained at an intermediate level. Therefore, B. buergeri adopts a size-assortative mating and maintains the female/male SVL ratio of approximately 1.44 to balance both fertilisation rate and swimming ability, thereby increasing reproductive success.

Construction of an Engineered Escherichia coli with Efficient Chemotactic and Metabolizing Ability toward Tetrathionate.

The emergence of genetically engineered bacteria has provided a new means for the diagnosis and treatment of diseases. However, in vivo applications of these engineered bacteria are hindered by their inefficient accumulation in areas of inflammation. In this study, we constructed an engineered Escherichia coli (E. coli) for directional migration toward tetrathionate (a biomarker of gut inflammation), which is regulated by the TtrSR two-component system (TCS) from Shewanella baltica OS195 (S. baltica). Specifically, we removed endogenous cheZ to control the motility of E. coli. Moreover, we introduced the reductase gene cluster (ttrBCA) from Salmonella enterica serotype typhimurium (S. typhimurium), a major pathogen causing gut inflammation, into E. coli to metabolize tetrathionate. The resulting strain was tested for its motility along the gradients of tetrathionate; the engineered strain exhibits tropism to tetrathionate compared with the original strain. Furthermore, the engineered E. coli could only restore its smooth swimming ability when tetrathionate existed. With these modifications enabling tetrathionate-mediated chemotactic and metabolizing activity, this strategy with therapeutic elements will provide a great potential opportunity for target treatment of various diseases by swapping the corresponding genetic circuits.

The Influence of The Learning-to-Swim Method Using Fins and Swimming Boards on The Butterfly-Style Swimming Ability of SeaRIA Aquatic Athletes

This study examines how SeaRIA Aquatic athletes' butterfly-style swimming proficiency is affected by using fins and swimming boards during the learning phase. Using a quasi-experimental methodology, the study concentrates on 55 SeaRIA Aquatic athletes. Twenty male athletes were chosen using purposive selection, and groups were created using matching strategies. A pretest, a 14-session therapy phase, and a posttest are all included in the study. The butterfly swimming ability test is used as the assessment instrument. The normality test (Liliefors) and the t-test with a significance level of α=0.05 are used in data analysis. The results show a strong relationship between the fin-and-swimming board learning approach and the improvement of butterfly swimming skills in SeaRIA Aquatic athletes. The estimated t-value of 15.37 is more than the essential t-table value of 1.81, indicating that the observed influence is significant. These findings highlight how well fins and swimming boards can be incorporated into swim training regimens for SeaRIA Aquatic athletes, especially when mastering the difficult butterfly-style technique. The consequences of this study go beyond its local setting, providing insightful information to aquatic sports organisations, coaches, and trainers looking for evidence-based methods to improve their participants' swimming skills. This study adds to the current conversation about novel and efficient ways to maximise training plans and lays the groundwork for further research on water sports education and performance improvement.

Phylogenetic Analysis and Characterization of Diguanylate Cyclase and Phosphodiesterase in Planktonic Filamentous Cyanobacterium Arthrospira sp.

Cyclic di-GMP (c-di-GMP) is a second messenger of intracellular communication in bacterial species, which widely modulates diverse cellular processes. However, little is known about the c-di-GMP network in filamentous multicellular cyanobacteria. In this study, we preliminarily investigated the c-di-GMP turnover proteins in Arthrospira based on published protein data. Bioinformatics results indicate the presence of at least 149 potential turnover proteins in five Arthrospira subspecies. Some proteins are highly conserved in all tested Arthrospira, whereas others are specifically found only in certain subspecies. To further validate the protein catalytic activity, we constructed a riboswitch-based c-di-GMP expression assay system in Escherichia coli and confirmed that a GGDEF domain protein, Adc11, exhibits potential diguanylate cyclase activity. Moreover, we also evaluated a protein with a conserved HD-GYP domain, Ahd1, the expression of which significantly improved the swimming ability of E. coli. Enzyme-linked immunosorbent assay also showed that overexpression of Ahd1 reduced the intracellular concentration of c-di-GMP, which is presumed to exhibit phosphodiesterase activity. Notably, meta-analyses of transcriptomes suggest that Adc11 and Ahd1 are invariable. Overall, this work confirms the possible existence of a functional c-di-GMP network in Arthrospira, which will provide support for the revelation of the biological function of the c-di-GMP system in Arthrospira.

How Do Swimming Students' Anthropometric Characteristics Affect Short-Course Swimming Performance

It has been found that anthropometric swimming performance factors may be related to and affect swimming performance. In light of this, the study's objective was to examine the association between certain motoric and anthropometric traits and 25-meter freestyle swimming performance results. A total of 16 male swimming students from Yozgat Bozok University's Faculty of Sport Sciences (age: 21.75±1.23 years; weight: 78.29±13.04 kg; height: 177±5.44 cm; body fat percentage: 17±7.5 %) took part in the study as volunteers. Height, body mass, skinfold thickness, circumference measurements (biceps in flexion, calf), diameter measurements (humerus epicondyle, femur epicondyle), static flexibility measurements (shoulder flexion, trunk-neck extension, ankle extension), and strength measurements (leg strength, back strength) were carried out to assess the anthropometric measurements of swimming students. In a semi-Olympic swimming pool, short-course freestyle scores of swimming students were recorded. The data appeared to have a normal distribution after the skewness and kurtosis tests, so the Pearson Correlation test was used to look at the correlation between 25-meter freestyle swimming levels and other characteristics. It was discovered that there was no statistically significant correlation between static flexibility and strength tests and 25-meter freestyle swimming performance results, but there was a negative and statistically significant correlation between swimming performance results of swimming students and mesomorph variables (r=-0.529, p=0.035). It is believed that identifying swimmers' somatotype structures may be crucial for talent selection and serve as an indicator of swimming ability.