Swimming Ability Research Articles

Behavioral Variability of Hatchlings Modifies Dispersal Potential in Crown Conch (Melongena corona): Why Do Larvae Crawl Away but Sometimes Swim?

AbstractThe diversity and consequences of development in marine invertebrates have, for a long time, provided the opportunity to understand different evolutionary solutions to living in variable environments. However, discrete classifications of development can impede a full understanding of adaptation to variable environments when behavioral, morphological, or physiological flexibility and variation exist within traditionally defined modes of development. We report here novel behavioral variability in hatchlings of a marine gastropod, the Florida crown conch (Melongena corona), that has broad significance for understanding the correlated evolution of development, dispersal, and reproductive strategies in variable environments. All hatchlings crawl away from egg capsules after emergence as larval pediveligers. Some subsequently swim for a brief period (seconds to minutes) before crawling again. From detailed observations of 120 individuals over 30 days, we observed 28 (23.3%) hatchlings swimming at least once (8%-50% per maternal brood). The propensity to swim was unrelated to time spent encapsulated or size at hatching and lasted for 22 days. We manipulated hypothesized environmental cues and found that the proportion of hatchlings that swam was highest in the absence of cues related to habitat or juvenile food and lowest when only habitat cues were present. The relative growth rate of hatchlings was highest when habitats contained a putative juvenile food source. About 44% of hatchlings were competent to metamorphose at emergence but did not metamorphose at this time in the lab or the field. The rate of metamorphosis increased with age and depended on the presence of unknown cues in the field. Crawl-away larvae with prolonged swimming ability may be an adaptation to balance the unpredictable risks of exclusively benthic or pelagic development and to allow the option to disperse to higher-quality habitat.

Switching Propulsion Mechanisms of Tubular Catalytic Micromotors.

Different propulsion mechanisms have been suggested for describing the motion of a variety of chemical micromotors, which have attracted great attention in the last decades due to their high efficiency and thrust force, enabling several applications in the fields of environmental remediation and biomedicine. Bubble-recoil based motion, in particular, has been modeled by three different phenomena: capillary forces, bubble growth, and bubble expulsion. However, these models have been suggested independently based on a single influencing factor (i.e., viscosity), limiting the understanding of the overall micromotor performance. Therefore, the combined effect of medium viscosity, surface tension, and fuel concentration is analyzed on the micromotor swimming ability, and the dominant propulsion mechanisms that describe its motion more accurately are identified. Using statistically relevant experimental data, a holistic theoretical model is proposed for bubble-propelled tubular catalytic micromotors that includes all three above-mentioned phenomena and provides deeper insights into their propulsion physics toward optimized geometries and experimental conditions.

Human impacts alter the distribution of fish functional diversity in Neotropical stream system

AbstractEvaluation of traits and functional diversity make assessments more robust when determining the nature and strength of the relationship between species and ecosystem processes. We investigated how anthropic interference and physical and limnological characteristics of streams changed fish functional trait distribution and their functional diversity in Neotropical streams located in Southern Brazil, encompassing Paraná, Paranapanema, Ivaí, and Pirapó river basins. We tested the hypotheses (a) that streams with very low human pressure show higher values of functional diversity due to the great variety of habitats and food resources; (b) streams with higher human pressure and more deforested are more related to fish functional traits as body morphologies indicative of weaker swimming ability and scraping feed morphology. We found that current velocity and stream width were correlated with compression and depression indices of the ventral region of the animals. Faster‐flow environments favored higher values of relative height of the caudal peduncle, relative head width, and relative mouth height values. These functional traits relate to habitat use and the size of consumed food. Altogether, these findings indicate possible partitioning of resources that would enable the co‐occurrence of species. Our results showed that human impacts influenced functional diversity and functional trait distribution. Urban land use and high conductivity were correlated with detritivorous species and species with internal reproduction. Poecilia reticulata dominated urban streams. We argue that the conservation of fish diversity in Neotropical streams requires orderly land use and occupation to avoid reducing species and functional diversity, and hence ecosystem function.Abstract in Portuguese is available with online material.

A preliminary studies to assess public knowledge of beach safety in east coast Malaysia.

Rip currents are one of the coastal hazards that put Malaysian beachgoers in a risky position. Most of the drowning accidents that occur at beaches worldwide are closely associated with this phenomenon. Research on rip currents is needed to build an effective measuring tool to overcome these issues. However, to date, research on rip currents is mainly focused on its physical aspects, commonly concentrating on the processes that influence and relate to the rips’ generation. As an effort to minimize the negative consequences exerted by the rips, there is an urgent need to enhance the rip-related research in the social sciences field. Comprehensive research that includes all fields might produce more beneficial and reliable information. Therefore, this study intends to examine the level of public understanding of rip currents and beach safety knowledge of the Teluk Cempedak Beach. A questionnaire comprising 5 sections and 31 questions was developed as the primary tool in this study. A total of 60 beachgoers have been surveyed for this preliminary study through a questionnaire to investigate their demographic profile, frequency of visiting the beach, swimming ability, and their knowledge of rip currents and beach safety. The results show that the beachgoers have poor knowledge of rip currents. Conversely, they are observed to have higher beach safety knowledge. Also, the findings help in filling the research gaps of this study in terms of the instrument used for the data collection procedure. Above all, an extension of this study may contribute to the development of beneficial tools in assessing public knowledge on beach safety and rip currents throughout Malaysian beaches.Supplementary informationThe online version contains supplementary material available at (10.1007/s11069-021-04613-z).

Exploring the impact of a student-centred survival swimming programme for primary school students in Australia: the perceptions of parents, children and teachers

Teaching basic swimming, water safety and rescue skills is recommended by the World Health Organization for all school-aged children. However, there is a lack of evidence on effective pedagogies to develop swimming competency and the success of swimming lessons as a drowning prevention intervention. This study used a self-report questionnaire and practical testing procedures to examine the effectiveness of a 10-week student-centred aquatic programme designed for children aged 10–12 years. The study also determined whether the non-traditional swimming programme was accepted by swim teachers, school teachers and principals, and parents from a range of schools from different geographical regions in Victoria, Australia. A total of 204 students were enrolled in the programme. The pre-programme results indicated a good level of swimming, water safety and aquatic knowledge, but low swimming ability. Swimming ability significantly improved from pre-programme to post-programme, with no significant post-programme ability differences between male and female children or for participants from different programmes. Qualitative feedback collected through questionnaires, interviews and/or focus groups from students ( n = 73) and parents ( n = 69), school teachers and principals ( n = 14), swim teachers and swim school managers ( n = 21) indicated strong support from principals and swim teachers for the student-centred pedagogy, and all stakeholders valued the focus on survival swimming competencies. This research highlights the importance of including stakeholders when designing and implementing aquatics programmes. The study has resulted in a well-founded, effective programme with tailored resources and instructional materials that are available for swim centres and schools that would enable schools globally to adopt and implement this programme.

A Novel Body Plan Alters Diversification of Body Shape and Genitalia in Live-Bearing Fish

Major evolutionary innovations can greatly influence subsequent evolution. While many major transitions occurred in the deep past, male live-bearing fishes (family Poeciliidae) more recently evolved a novel body plan. This group possesses a three-region axial skeleton, with one region—the ano-urogenital region—representing a unique body region accommodating male genitalic structures (gonopodial complex). Here we evaluate several hypotheses for the evolution of diversity in this region and examine its role in the evolution of male body shape. Examining Gambusia fishes, we tested a priori predictions for (1) joint influence of gonopodial-complex traits on mating performance, (2) correlated evolution of gonopodial-complex traits at macro- and microevolutionary scales, and (3) predator-driven evolution of gonopodial-complex traits in a post-Pleistocene radiation of Bahamas mosquitofish. We found the length of the sperm-transfer organ (gonopodium) and its placement along the body (gonopodial anterior transposition) jointly influenced mating success, with correlational selection favoring particular trait combinations. Despite these two traits functionally interacting during mating, we found no evidence for their correlated evolution at macro- or microevolutionary scales. In contrast, we did uncover correlated evolution of modified vertebral hemal spines (part of the novel body region) and gonopodial anterior transposition at both evolutionary scales, matching predictions of developmental connections between these components. Developmental linkages in the ano-urogenital region apparently play key roles in evolutionary trajectories, but multiple selective agents likely act on gonopodium length and cause less predictable evolution. Within Bahamas mosquitofish, evolution of hemal-spine morphology, and gonopodial anterior transposition across predation regimes was quite predictable, with populations evolving under high predation risk showing more modified hemal spines with greater modifications and a more anteriorly positioned gonopodium. These changes in the ano-urogenital vertebral region have facilitated adaptive divergence in swimming abilities and body shape between predation regimes. Gonopodium surface area, but not length, evolved as predicted in Bahamas mosquitofish, consistent with a previously suggested tradeoff between natural and sexual selection on gonopodium size. These results provide insight into how restructured body plans offer novel evolutionary solutions. Here, a novel body region—originally evolved to aid sperm transfer—was apparently co-opted to alter whole-organism performance, facilitating phenotypic diversification.

Effects of feeding condition on the morphology, behaviour and nutritional status of

Early life stages of migratory fish in rivers rely on physical transport mechanisms to carry them from spawning sites to distant nursery areas where they find food and refuge conditions. Starvation after a prolonged downriver drift could severely affect the colonisation and predator evasion capabilities of the larvae. In this study we investigated differences in the external morphology, nutritional condition and swimming abilities of fed and unfed Prochilodus lineatus early larvae under experimental conditions. After yolk reabsorption on Day 6, larvae were either fed with nauplii of Artemia salina or left unfed for up to 10 days. Larvae from each feeding regime (i.e. fed and unfed) were sampled daily from three aquaria, and the morphometry and routine swimming activity were determined and analysed together with a previously published RNA/DNA ratio dataset. The results were in agreement with previous investigations that indicated that the larvae of this species have starvation endurance; however, prolonged food deprivation is associated with a smaller body, anal depth and head length, as well as lower RNA/DNA ratios and reduced swimming ability.

Development of a Low-Cost Bio-Inspired Swimming Robot (SRob) with IoT

Now-a-days, exploring underwater is a difficult activity to do and requires specialized equipment to explore it. Many studies so far have proven that bio-inspired robotic fish such as stingray robots have many advantages for use as underwater exploration. One of them is the manta ray which can show excellent swimming ability by flapping the pectoral fins with large amplitude. By studying the movement behavior of genus Mobula, the development of biomimetic robots has grown exponentially in recent years. But this technology requires expensive development costs, and the prototypes produced are heavy. Therefore, the development of low-cost bio-inspired Swimming Robot (SRob) using embedded controller with internet of things (IOT) is proposed and presented in this paper. SRob is designed with a small size and lightweight compared to other conventional swimming robots and is well equipped with 6 servo motors, ADXL335 accelerometer 3-axis, 2 Lipo batteries 7.4V, ESP01 Wi-Fi module and Arduino Mega. The RemoteXY app that works like a remote control will be connected to the Arduino Mega using the ESP01 Wi-Fi module to control servo motors and obtain readings of the sensors. Based on the experimental results, the servo motor used to produce flapping motion can be controlled precisely while producing a large amplitude of motion. In addition, the position control for the compact SRob can be realized and determined correctly while swimming in the water.

Investigation of the swimming ability of typical fish in the Red River(Yuanjiang) basin and its application to the design of fish passage facilities

Investigation of the swimming ability of typical fish in the Red River(Yuanjiang) basin and its application to the design of fish passage facilities

First report of successful recruitment by conjoined larvae in the brooding scleractinian coral Pocillopora acuta, southern Taiwan

We report the first observation of conjoined larvae (CL) in the scleractinian coral Pocillopora acuta. Colonies at an elevated temperature had a higher ratio of CL (29 °C; 1:200) than colonies at an ambient temperature (26 °C; 1:500). CL demonstrated normal swimming ability and capacity for settlement, metamorphosis, and asexual budding.

Outsourcing Swimming Education-Experiences and Challenges.

In Norway, swimming and lifesaving education (swimming education) is an obligatory part of physical education, with explicit learning aims after grade four. After recent reports of Norwegian pupils achieving low scores in swimming abilities, the Government has outlined strategies for improving swimming education. There is a notable trend toward using external providers in delivering swimming education. This article examines the outsourcing of swimming education in Norwegian primary schools. Eighteen semi-structured interviews were conducted with school leaders, physical education teachers and swimming instructors involved in outsourcing arrangements. The outsourcing was organized through private providers, municipalities, or local swimming clubs. Data were analyzed thematically and separated into highlighted areas of outsourcing practices. The results showed that outsourcing may be a solution for schools that lack staff with swimming experience and knowledge. It also indicates that teacher courses, professional development through collaboration, and strategies for measuring quality would improve swimming education.

Adult life strategy affects distribution patterns in abyssal isopods – implications for conservation in Pacific nodule areas

Abstract. With increasing pressure to extract minerals from the deep-sea bed, understanding the ecological and evolutionary processes that limit the spatial distribution of species is critical to assessing ecosystem resilience to mining impacts. The aim of our study is to gain a better knowledge about the abyssal isopod crustacean fauna of the central Pacific manganese nodule province (Clarion–Clipperton Fracture Zone, CCZ). In total, we examined 22 epibenthic sledge (EBS) samples taken at five abyssal areas located in the central northern Pacific including four contracting areas and one Area of Particular Environmental Interest (APEI3). Additional samples come from the DISturbance and reCOLonization experiment (DISCOL) area situated in the Peru Basin, southeastern Pacific. Using an integrative approach that combined morphological and genetic methods with species delimitation analyses (SDs) we assessed patterns of species range size, diversity, and community composition for four different isopod families (Munnopsidae Lilljeborg, 1864; Desmosomatidae Sars, 1897; Haploniscidae Hansen, 1916; and Macrostylidae Hansen, 1916) displaying different dispersal capacities as adults. Isopods are brooders, so their distribution and connectivity cannot be explained by larval dispersal but rather by adult locomotion. In particular, our objectives were to (1) identify potential differences in the distributional ranges of isopod families relative to their locomotory potential and to (2) evaluate the representativeness of the APEI for the preservation of regional biodiversity in the CCZ following mining disturbances. From 619 specimens, our SD analysis could distinguish 170 species, most of which were new to science (94.1 %). We found that increased locomotory ability correlated with higher species diversity with 9 species of Macrostylidae, 23 of Haploniscidae, 52 of Desmosomatidae, and 86 of Munnopsidae. This is supported by family-level rarefaction analyses. As expected, we found the largest species ranges in the families with swimming abilities, with a maximum recorded species range of 5245 and 4480 km in Munnopsidae and Desmosomatidae, respectively. The less motile Haploniscidae and Macrostylidae had maximal species ranges of 1391 and 1440 km, respectively. Overall, rarefaction analyses indicated that species richness did not vary much between areas, but the real number of species was still not sufficiently sampled. This is also indicated by the large proportion of singletons (40.5 %) found in this study. The investigated contractor areas in the CCZ were more similar in species composition and had a higher proportion of shared species between each other than the closely located APEI3 and the distantly located DISCOL area. In fact, the DISCOL area, located in the Peru Basin, had more species in common with the core CCZ areas than APEI3. In this regard, APEI3 does not appear to be representative as serving as a reservoir for the fauna of the investigated contractor areas, at least for isopods, as it has a different species composition. Certainly, more data from other APEIs, as well as preservation reference zones within contractor areas, are urgently needed in order to assess their potential as resources of recolonization of impacted seabed.

Phenylalanine Hydroxylase RNAi Knockdown Negatively Affects Larval Development, Molting and Swimming Performance of Salmon Lice

Phenylalanine hydroxylase (PAH) is a crucial enzyme involved in tyrosine biosynthesis, having roles in neurological and physiological processes. The purpose of PAH has received little attention in crustaceans despite extensive investigations in other arthropods. Here, we characterize the PAH gene for the first time in the parasite Lepeophtheirus salmonis, a copepod that is responsible for huge economic losses in salmonid fish farming. Phylogenetic and sequence analyses confirmed that LsPAH is closely related to the metazoan PAH with conserved ACT regulatory and catalytic domains. Temporal expression patterns revealed that LsPAH is expressed throughout all developmental stages peaking during the copepodite stages, suggesting an essential role in developmental physiology. We used RNAi to knockdown LsPAH expression in the nauplius I stage to study developmental function during the larval stages. PAH knockdown impaired larval development, molting and swimming ability with severe morphological defects. This study provides insight into the role of PAH in copepods and demonstrates the importance of this metabolic gene in salmon louse growth and development.

Multispecies Fish Passage Evaluation at a Rock‐Ramp Fishway in a Colorado Transition Zone Stream

AbstractStream habitat fragmentation caused by manmade structures is ubiquitous in Colorado, creating a need for passage solutions that accommodate multiple fish species. This study tested the effectiveness of a rock‐ramp fishway for passing nine fish species with a range of swimming abilities. The target species for the fishway design included Brassy MinnowHybognathus hankinsoni(weakest swimming), Longnose DaceRhinichthys cataractae, Longnose SuckerCatostomus catostomus, and Brown TroutSalmo trutta(strongest swimming). Testing included a 46‐h enclosure study and 3‐month extended study, during which fish passage was evaluated using PIT tags. All of the species exhibited successful passage through the fishway during the enclosure study, but movement probabilities varied by species. Five species were not detected at the fishway during the extended study, possibly due to issues with attraction flows, entrance conditions, or motivation. Hydraulic conditions within the fishway were also evaluated. Roughness elements maintained a benthic, low‐velocity zone across a range of flows, even when surface and depth‐averaged velocities surpassed the design criteria for the weakest swimming species. The methods from this study could be replicated at other locations to evaluate design criteria (e.g., slope, capacity, roughness, and configuration) and performance for a variety of fish species and fishway types.

Starvation of the Respiratory Metabolism and Locomotion of Aurelia aurita s.l. Ephyrae

Blooms of the scyphozoan jellyfish Aurelia aurita are greatly regulated by the survival rate of planktonic ephyrae. The ecophysiology of ephyrae is poorly studied compared with polyps and medusae. As extremely strong starvation resistance and recovery capability of A. aurita ephyrae may due to its low metabolic rate as well as starvation may reduce the swimming ability of ephyrae which may lead to the higher predation loss, the effects of temperature and starvation on their respiration and pulsation rates were examined. In this study, ephyrae under different starvation conditions were measured by a fluorescence-based DO meter after 72 h incubation. And the pulsation rates were measured at every 10-d interval in 1-liter plastic bottle by a hand-held counter. The results showed that the mean respiration rates of newly released ephyrae were 0.24, 0.24 and 0.19 μl O2 ephyra-1 d-1 at 15°C, 12°C and 9°C, respectively, and the rates tended to decrease with increasing starvation duration. Carbon weight-specific respiration rates did not change significantly with starvation duration. The dry weight-specific respiration rates of newly released A. aurita ephyrae (i.e., 11.7-14.6 μl O2 mg DW-1 d-1) were nearly one order of magnitude lower than the rates for planktonic larvae of other taxa (e.g., molluscs, crustaceans and fish). The maximum pulsation rate taken by A. aurita ephyrae was 49.2 beats min-1, which represents the maximum swimming velocity to be 8.87 cm·min-1. The pulsation rates were not affected by temperature over the range between 9°C and 15°C. However, they were influenced by starvation duration. Starvation-derived decrease in pulsation together with associated body shrinkage may lead to lower encounter rate of prey and lower escaping ability from predators, which may lead to higher predation loss in the field.

Efficient mate finding in planktonic copepods swimming in turbulence.

Zooplankton live in dynamic environments where turbulence may challenge their limited swimming abilities. How this interferes with fundamental behavioral processes remains elusive. We reconstruct simultaneously the trajectories of flow tracers and calanoid copepods and we quantify their ability to find mates when ambient flow imposes physical constrains on their motion and impairs their olfactory orientation. We show that copepods achieve high encounter rates in turbulence due to the contribution of advection and vigorous swimming. Males further convert encounters within the perception radius to contacts and then to mating via directed motion toward nearby organisms within the short time frame of the encounter. Inertial effects do not result in preferential concentration, reducing the geometric collision kernel to the clearance rate, which we model accurately by superposing turbulent velocity and organism motion. This behavioral and physical coupling mechanism may account for the ability of copepods to reproduce in turbulent environments.

Simple larvae sustain the world’s smallest marine vertebrates

Cryptobenthic reef fishes (small, camouflaged, benthic-dwelling fishes) face exceptionally high mortality rates, yet they are the most abundant fishes on coral reefs. To maintain local adult populations in the face of these mortality rates, larval cryptobenthics may have adaptations that limit dispersal. However, the basis for this larval retention is unknown. Here, we compared the body shapes of adult and larval cryptobenthics with those of adult and larval large reef fishes to explore how morphological adaptations may enable cryptobenthic larvae to stay near their natal reefs. We found that while adults and larvae of large reef fishes and adult cryptobenthics display different ‘average’ morphological characteristics (i.e. different locations of the morphospace centroid), they all display a similar range of body shapes (i.e. similar morphospace sizes around their centroids). Larval cryptobenthics, however, exhibit a greatly constrained range of morphologies (occupying less than 20% of the morphospace of any other category). Larval cryptobenthics appear to be limited to a simple body plan, with elongate bodies and small fins. This simple body shape is likely to result in relatively poor swimming abilities, which may limit the ability of cryptobenthic larvae to maintain their position against prevailing currents in the pelagic zone. As such, limited dispersal in cryptobenthic larvae is likely to depend upon behavioural adaptations, such as flow-refuging, to avoid being washed away from their natal reefs.

Allometric relationships in morphological traits associated with foraging, swimming ability, and predator defense reveal adaptations toward brackish and freshwater environments in the threespine stickleback.

Freshwater colonization by threespine stickleback has led to divergence in morphology between ancestral marine and derived freshwater populations, making them ideal for studying natural selection on phenotypes. In an open brackish–freshwater system, we previously discovered two genetically distinct stickleback populations that also differ in geometric shape: one mainly found in the brackish water lagoon and one throughout the freshwater system. As shape and size are not perfectly correlated, the aim of this study was to identify the morphological trait(s) that separated the populations in geometric shape. We measured 23 phenotypes likely to be important for foraging, swimming capacity, and defense against predation. The lateral plate morphs in freshwater displayed few significant changes in trait sizes, but the low plated expressed feeding traits more associated with benthic habitats. When comparing the completely plated genetically assigned populations, the freshwater, the hybrids, the migrants and the lagoon fish, many of the linear traits had different slopes and intercepts in trait‐size regressions, precluding our ability to directly compare all traits simultaneously, which most likely results from low variation in body length for the lagoon and migrant population. We found the lagoon stickleback population to be more specialized toward the littoral zone, displaying benthic traits such as large, deep bodies with smaller eyes compared to the freshwater completely plated morph. Further, the lagoon and migrant fish had an overall higher body coverage of lateral plates compared to freshwater fish, and the dorsal and pelvic spines were longer. Evolutionary constraints due to allometric scaling relationships could explain the observed, overall restricted, differences in morphology between the sticklebacks in this study, as most traits have diversified in common allometric trajectories. The observed differences in foraging and antipredation traits between the fish with a lagoon and freshwater genetic signature are likely a result of genetic or plastic adaptations toward brackish and freshwater environments.

Effects of obstacles and flow velocity on locomotory behavior in juvenile, silver carp, Hypophthalmichthys molitrix

AbstractWe currently have only a minimal understanding of energy‐saving strategies of fish in unsteady flows. In this study, we found that obstacle shape can affect swimming ability of fish: our results suggested that a half cylinder improved critical swimming speed of silver carp (Hypophthalmichthys molitrix) compared with swimming downstream of a full cylinder, square tube or for free‐flow conditions. We also discovered how silver carp alter their locomotory behavior in response to turbulent flow caused by varying flow velocities around obstacles. At a flow velocity of 1 BL/s (body length per second), the fish spent similar percentages of time between holding station and moving forward behind the half cylinder: their motions resembled freestream swimming behavior. The greatest percentage of time spent downstream of the half cylinder occurred at a flow velocity of 5 BL/s. Fish were unstable and displayed irregular body motions with large lateral displacement at 5 BL/s. However, the fish held station for a long time and moved forward steadily behind the half cylinder at 3 BL/s. In holding station behind the half cylinder, fish maintained constant tail‐beat frequency and tail‐ beat amplitude when flow velocity was increased from 1 to 3 BL/s. In moving forward behind the half cylinder, fish increased tail‐beat frequency and tail‐beat amplitude while maintaining constant ground swimming speed, swimming acceleration and ground stride when flow velocity was increased from 3 to 5 BL/s. Moreover, fish positioned their snouts in a small area approximately 1–3 BL downstream from the half cylinder at 3 BL/s. These behaviors support the hypothesis that turbulence behind a half cylinder was a suitable location for fish to conserve energy at 3 BL/s. Our results indicate that the combined effect of obstacles and flow velocity influence fish locomotory behavior, and some combinations may be beneficial to fish energy expenditure swimming in unsteady flow.

Nucleoside Diphosphate Kinases (ndk) reveals a key role in adhesion and virulence of Aeromonas veronii

Aeromous veronii is a severe pathogen that can infect aquatic organisms and mammals also causes irreparable damage to fish aquaculture. Analysis of the results of epidemiological investigations have revealed that its tolerance to drugs and the virulence of A. veronii have increased in recent years. Most of the researches on A. veronii focuse on the strain isolation, identification, and drug susceptibility. However, we do not know so much about the molecular mechanism of the pathogenesis on A. veronii. Here we identified and obtained the highly expressed TH0426 Nucleoside Diphosphate Kinases (NDK) of A. veronii. We first constructed a mutant strain (△-ndk) by generating an in-frame deletion of the ndk gene, to investigate the functional role in A. veronii TH0426. The ability in the adhesion and invasion of EPC cells and biofilm formation significantly reduced of the △-ndk strain. The motility test showed that the ndk gene affected on the swimming ability, while did not affect the swarming motility. Compared with the wild-type strain TH0426, the pathogenicity of △-ndk strain to zebrafish reduced severely. Besides, the ndk gene has affected the apoptosis rate of A. veronii TH0426. These results would help to demonstrate the function of ndk further and realize the pathogenesis on A. veronii.