Artykuły w czasopismach na temat „Swimming – Physiological aspects”

In recent years, the interest of female dominance in long-distance swimming has grown where several newspaper articles have been published speculating about female performance and dominance—especially in open-water ultra-distance swimming. The aim of this narrative review is to review the scientific literature regarding the difference between the sexes for all swimming strokes (i.e., butterfly, backstroke, breaststroke, freestyle and individual medley), different distances (i.e., from sprint to ultra-distances), extreme conditions (i.e., cold water), different ages and swimming integrated in multi-sports disciplines, such as triathlon, in various age groups and over calendar years. The influence of various physiological, psychological, anthropometrical and biomechanical aspects to potentially explain the female dominance was also discussed. The data bases Scopus and PUBMED were searched by April 2020 for the terms ’sex–difference–swimming’. Long-distance open-water swimmers and pool swimmers of different ages and performance levels were mainly investigated. In open-water long-distance swimming events of the ’Triple Crown of Open Water Swimming’ with the ’Catalina Channel Swim’, the ’English Channel Swim’ and the ’Manhattan Island Marathon Swim’, women were about 0.06 km/h faster than men. In master swimmers (i.e., age groups 25–29 to 90–94 years) competing in the FINA (Fédération Internationale de Natation) World Championships in pool swimming in freestyle, backstroke, butterfly, breaststroke, individual medley and in 3000-m open-water swimming, women master swimmers appeared able to achieve similar performances as men in the oldest age groups (i.e., older than 75–80 years). In boys and girls aged 5–18 years—and listed in the all-time top 100 U.S. freestyle swimming performances from 50 m to 1500 m—the five fastest girls were faster than the five fastest boys until the age of ~10 years. After the age of 10 years, and until the age of 17 years, however, boys were increasingly faster than girls. Therefore, women tended to decrease the existing sex differences in specific age groups (i.e., younger than 10 years and older than 75–80 years) and swimming strokes in pool-swimming or even to overperform men in long-distance open-water swimming (distance of ~30 km), especially under extreme weather conditions (water colder than ~20 °C). Two main variables may explain why women can swim faster than men in open-water swimming events: (i) the long distance of around 30 km, (ii) and water colder than ~20 °C. Future studies may investigate more detailed (e.g., anthropometry) the very young (<10 years) and very old (>75–80 years) age groups in swimming

Abstract Introduction. When evaluating the swimming technique of people with disabilities, a particularly important factor, besides physiological aspects, is the efficiency of the effort expended. This suggests that assessing and monitoring the effectiveness of swimming should be a regular part of training for swimmers with disabilities. Therefore, it seems important to distinguish how changes occur in the parameters that determine the effectiveness of swimming. This is especially true of anaerobic lactic exercise as the lactic acid concentration in the blood increases significantly. The aim of this study was to evaluate the usefulness of calculating velocity and the stroke index in the swimming training of people with disabilities, along with the progressive fatigue of a high-intensity interval training workout. Material and methods. The sample comprised 12 elite competitors with a disability. The experiment consisted in swimming sequential distances of 48 m, 50 m, 52 m, and 54 m at maximum intensity. Competitors performed four sets of four repetitions with a 75-second interval between repetitions and 15 minutes of active resting between sets. All sets were recorded using five digital cameras with a frequency of 50 frames per second. The recorded material was analysed with the use of motion analysis software, and the stroke index was calculated. Results. There was found to be no significant change in the average swimming velocity during each set and corresponding repetition, which means that the participants were able to tolerate the training intensity. Also, the stroke index did not change to a statistically significant degree in either of the subsequent sets or the subsequent repetitions (p < 0.05). Conclusions. We conclude that analysing the value of the swimming stroke index for people with disabilities can be a diagnostic method for assessing the effectiveness of high-intensity interval training.

The behavioral responses of fishes to temperature variation have received little attention despite their direct implications to bioenergetics-based models of production and encounter-based models of food web dynamics. Behavioral characteristics of juvenile walleye pollock (Theragra chalcogramma), a pelagic marine zooplanktivore, were examined between 2 and 9 °C in large arenas. Routine swim speed, path sinuosity, and schooling cohesiveness of fish in small groups were described from overhead video observations. In a separate experiment, maximum swimming speeds were measured in a recirculating flume. Routine and maximum swimming speeds had contrasting responses to temperature demonstrating a behavioral rather than physiological regulation of activity level. Routine swim speed was 48% faster at 2 °C than at 9 °C. This result is inconsistent with the assumption of a constant activity multiplier for metabolism incorporated into most bioenergetics models of fish growth. Increased swim speed, along with the reduced path sinuosity observed at low temperatures, may reflect kinetic aspects of habitat selection. Group cohesion increased at low temperatures, with nearest neighbors averaging 32% closer at 2 °C than at 9 °C. These results demonstrate that representative models of energy flow through marine food webs depend on an improved understanding of the behavioral as well as physiological responses of fishes to thermal variation.

Introdução: o desempenho na natação pode ser influenciado por diferentes fatores, como a técnica de nado, as forças envolvidas na tarefa ou, ainda, aspectos fisiológicos e biomecânicos, dentre estes as análises das forças propulsiva (FP) e resistivas (FR) são de fundamental importância para o desenvolvimento da natação competitiva. O nado amarrado é um método largamente utilizado por técnicos pesquisadores nos últimos 50 anos, podemos atribuir isso a sua praticidade e custo reduzido quando comparado a outros métodos. Objetivo: elucidar a aplicabilidade do nado amarrado em nível histórico e prático. Método: foi realizado um levantamento bibliográfico em bases de dados cujos trabalhos utilizaram de alguma forma o nado amarrado ou que o estudaram. Resultados: foi observado que o nado amarrado é uma ferramenta com alta reprodutibilidade, possui boa relação com o desempenho na natação e pode ser utilizada para o acompanhamento de atletas ao longo de um programa de treino, bem como servir de potencial preditor de talentos esportivos. Conclusão: o nado amarrado possui lacunas quando a descrição detalhada dos métodos utilizados, contudo devido ao volume de trabalhos produzidos nas últimas décadas, podemos afirmar que este possui base sólida para ser aplicado para pesquisas e treinamento de natação.ABSTRACT. Tethered swim: a historical review and applicability. Background: swimming performance can be influenced by different factors, such as swimming technique, the forces involved in the task or, also, physiological and biomechanical aspects, among which the analyzes of the propulsive (PF) and resistive (FR) forces are of fundamental importance for the development of competitive swimming. The tied swim is a method widely used by technical researchers in the last 50 years, we can attribute this to its practicality and reduced cost when compared to other methods. Objective: to elucidate the applicability of the tied swim in historical and practical level. Methods: a bibliographic survey was carried out in databases whose works somehow used the tethered swimming or studied it. Results: It has been observed that the tied swim is a tool with high reproducibility, has a good relationship with swimming performance and can be used to accompany athletes throughout a training program, as well as to serve as a potential predictor of sports talents. Conclusion: the tied swim has gaps when the detailed description of the methods used, however due to the volume of work produced in the last decades, we can affirm that it has a solid base to be applied for research and swimming training.

Abstract Ultra Short Race Pace training (USRPT) is an emerging training modality devised in 2011 to deviate from high-volume swimming training that is typically prescribed. USRPT aims to replicate the exact demands of racing, through its unique prescription of race-pace velocity sets with short rest intervals. It has been surmised, with little physiological evidence, that USRPT provides swimmers with the best opportunity to optimize the conditioning, technique, and psychology aspects of racing at the most specific velocity of the relevant event, with low blood lactate concentration. The aim of this study was to examine acute physiological responses of USRPT. Fourteen swimmers were recruited to perform a USRPT set: 20 x 25 m freestyle with a 35-s rest interval. Swimmers were required to maintain the velocity of their 100 m personal best time for each sprint. Sprint performance, blood lactate, heart rate and the RPE were measured. Blood lactate was taken before, during (after every 4 sprints) and 3 minutes after the USRPT protocol. Heart rate monitors were used to profile the heart rate. Athletes reported the RPE before- and after completion of the USRPT set. Sprint times increased by 3.3-10.8% when compared to the first sprint (p < 0.01). There was high blood lactate concentration (13.6 ± 3.1mmol/l), a significant change in the RPE from 8 ± 1.6 to 18 ± 1.6 (p < 0.01) and a substantially high heart rate profile with an average HRmax of 188 ± 9 BPM. The results show the maximal intensity nature of USRPT and portray it as an anaerobic style of training.

Glycolytic flux in white muscle can be increased several-hundredfold by exercise. Phosphofructokinase (PFK; EC 2.7.1.11) is a key regulatory enzyme of glycolysis, but how its activity in muscle is controlled is not fully understood. In order not to neglect integrative aspects of metabolic regulation, we have studied in frogs (Rana temporaria) a physiological form of muscle work (swimming) that can be triggered like a reflex. We analysed swimming to fatigue in well rested frogs, recovery from exercise, and repeated exercise after 2 h of recovery. At various times, gastrocnemius muscles were tested for glycolytic intermediates and effectors of PFK. All metabolites responded similarly to the two periods of exercise, with the notable exception of fructose 2,6-bisphosphate (F2,6P2), which we proved to be a most potent activator of frog muscle PFK. The first bout of exercise triggered a more than 10-fold increase in F2,6P2; PFK activity and the content of F2,6P2 in muscle were well correlated. F2,6P2 decreased to pre-exercise levels in fatigued frogs and it virtually disappeared during recovery. Varying by a factor of 70, F2,6P2 was the most dynamic of all metabolites in muscle. Even more surprisingly, F2,6P2 did not respond at all to a second bout of exercise. Other activators of PFK, such as Pi, AMP and ADP, are increased as a consequence of increased ATP turnover in contracting muscle cells. This does not apply to F2,6P2, which is likely to respond to extracellular signals and could be involved in mechanisms by which muscle metabolism is integrated into the metabolism of the whole body. Whether this phenomenon exists in vertebrates other than the frog, and maybe even in humans, and how the content of F2,6P2 in muscle is controlled are intriguing open questions.

SUMMARY This study investigated physiological and behavioural aspects of diving development in pups of the harbour seal Phoca vitulina. Behavioural data (4280 h, 6027 dives) from time/depth recorders (N=13) deployed on pups aged 0–19 days are presented concomitantly with physiological measurements (N=8, sampled both early and late in the nursing period) of blood oxygen stores and body composition. Pups grew from 12.6±1.8 kg (mean age 2 days, total body fat 16±4 %) to 22.2±2.5 kg (mean age 16 days, total body fat 35±5 %; means ± s.d.) over the duration of the experiment. Pups less than 5 days of age had an elevated haematocrit and reduced plasma volume compared with older pups. Although plasma volume and blood volume increased, mass-specific blood oxygen stores (total haemoglobin) fell during the study period. Simultaneously, the following behavioural indicators of diving ability increased: the proportion of time spent in the water, dive depth, dive duration, bottom time and maximum daily swimming velocity. In addition, the proportion of dives that were identified by cluster analyses as being U-shaped increased significantly with age. On the basis of the measured blood oxygen stores, less than 1 % of the recorded dives exceeded the calculated aerobic dive limit. Thus, development in blood oxygen stores or rates of oxygen consumption did not seem to restrain the rate of neonatal dive development in harbour seals. It appears that behavioural modifications (experience and learning) may be the primary rate-limiting factors for ontogeny of diving skills in neonates of this species.

In Loligo opalescens, a sudden visual stimulus (flash) elicits a stereotyped, short-latency escape response that is controlled primarily by the giant axon system at 15 C. We used this startle response as an assay to examine the effects of acute temperature changes down to 6 C on behavioral and physiological aspects of escape jetting. In free-swimming squid, latency, distance traveled and peak velocity for single escape jets all increased as temperature decreased. In restrained squid, intra-mantle pressure transients during escape jets increased in latency, duration and amplitude at low temperature. Recordings of stellar nerve activity revealed repetitive firing of the giant motor axon accompanied by increased activity in the non-giant motor axons that run in parallel. Selective stimulation of giant and non-giant motor axons in isolated nerve-muscle preparations failed to show the effects seen in vivo, i.e. increased peak force and increased neural activity at low temperature. Taken together, these results suggest that L. opalescens is able to compensate escape jetting performance for the effects of acute temperature reduction. A major portion of this compensation appears to occur in the central nervous system and involves alterations in the recruitment pattern of both the giant and non-giant axon systems.

Few studies have evaluated the joint effects of elevated temperature and pCO2 on marine organisms. In this study we investigated the interactive effects of Intergovernmental Panel on Climate Change predicted temperature and pCO2 for the end of the 21st century on key aspects of larval development of the American lobster, Homarus americanus, an otherwise well-studied, iconic, and commercially prominent species in the northeastern United States and Atlantic Canada. Our experiments showed that larvae (stages I–III) and postlarvae (stage IV) reared in the high temperature treatments (19 °C) experienced significantly lower survival, developed twice as fast, and had significantly higher oxygen consumption rates, than those in ambient treatments (16 °C). Larvae from the ambient temperature/high pCO2 (750 ppm) treatment had significantly longer carapace lengths, greater dry masses in stages I–III and higher C: N ratios in stage IV than larvae from all other treatments. Stage IVs raised in the high pCO2 treatment at 19 °C had significantly higher feeding rates and swimming speeds than stage IVs from the other three treatments. Together these results suggest that projected end-century warming will have greater adverse effects than increased pCO2 on larval survival, and changing pCO2 may have a complex effect on larval metabolism and behaviour. Understanding how the most vulnerable life stages of the lobster life cycle respond to climate change is essential in connecting the northward geographic shifts projected by habitat quality models, and the underlying physiological and genetic mechanisms that drive their ecology.

Chemotaxis of sperm is an important step toward fertilization. During chemotaxis, sperm change their swimming behavior in a gradient of the chemoattractant that is released by the eggs, and finally sperm accumulate near the eggs. A well established model to study chemotaxis is the sea urchin Arbacia punctulata. Resact, the chemoattractant of Arbacia, is a peptide that binds to a receptor guanylyl cyclase. The signaling pathway underlying chemotaxis is still poorly understood. Stimulation of sperm with resact induces a variety of cellular events, including a rise in intracellular pH (pHi) and an influx of Ca2+; the Ca2+ entry is essential for the chemotactic behavior. Previous studies proposed that the influx of Ca2+ is initiated by the rise in pHi. According to this proposal, a cGMP-induced hyperpolarization activates a voltage-dependent Na+/H+ exchanger that expels H+ from the cell. Because some aspects of the proposed signaling pathway are inconsistent with recent results (Kaupp, U.B., J. Solzin, J.E. Brown, A. Helbig, V. Hagen, M. Beyermann, E. Hildebrand, and I. Weyand. 2003. Nat. Cell Biol. 5:109–117), we reexamined the role of protons in chemotaxis of sperm using kinetic measurements of the changes in pHi and intracellular Ca2+ concentration. We show that for physiological concentrations of resact (&lt;25 pM), the influx of Ca2+ precedes the rise in pHi. Moreover, buffering of pHi completely abolishes the resact-induced pHi signal, but leaves the Ca2+ signal and the chemotactic motor response unaffected. We conclude that an elevation of pHi is required neither to open Ca2+-permeable channels nor to control the chemotactic behavior. Intracellular release of cGMP from a caged compound does not cause an increase in pHi, indicating that the rise in pHi is induced by cellular events unrelated to cGMP itself, but probably triggered by the consumption and subsequent replenishment of GTP. These results show that the resact-induced rise in pHi is not an obligatory step in sperm chemotactic signaling. A rise in pHi is also not required for peptide-induced Ca2+ entry into sperm of the sea urchin Strongylocentrotus purpuratus. Speract, a peptide of S. purpuratus may act as a chemoattractant as well or may serve functions other than chemotaxis.

Background Depending on the stroke and distances of the events, swim starts have been estimated to account for 0.8% to 26.1% of the overall race time, with the latter representing the percentage in a 50 m sprint front crawl event (Cossor & Mason, 2001). However, it is still somewhat unclear what are the key physiological characteristics underpinning swim start performance. The primary aim of this study was to develop a multiple regression model to determine key lower body force-time predictors using the squat jump for swim start performance as assessed by time to 5 m and 15 m in national and international level swimmers. A secondary aim was to determine if any differences exist between males and females in jump performance predictors for swim start performance. Methods A total of 38 males (age 21 ± 3.1 years, height 1.83 ± 0.08 m, body mass 76.7 ± 10.2 kg) and 34 females (age 20.1 ± 3.2 years, height 1.73 ± 0.06 m, body mass 64.8 ± 8.4 kg) who had competed at either an elite (n = 31) or national level (n = 41) participated in this study. All tests were performed on the same day, with participants performing three bodyweight squat jumps on a force platform, followed by three swim starts using their main swimming stroke. Swim start performance was quantified via time to 5 m and 15 m using an instrumented starting block. Results Stepwise multiple linear regression with quadratic fitting identified concentric impulse and concentric impulse2 as statistically significant predictors for time to 5 m (R2 = 0.659) in males. With time to 15 m, concentric impulse, age and concentric impulse2 were statistically significant predictors for males (R2 = 0.807). A minimum concentric impulse of 200–230 N.s appears required for faster times to 5 m and 15 m, with any additional impulse production not being associated with a reduction in swim start times for most male swimmers. Concentric impulse, Reactive strength index modified and concentric mean power were identified as statistically significant predictors for female swimmers to time to 5 m (R2 = 0.689). Variables that were statistically significant predictors of time to 15 m in females were concentric impulse, body mass, concentric rate of power development and Reactive strength index modified (R2 = 0.841). Discussion The results of this study highlight the importance of lower body power and strength for swim start performance, although being able to produce greater than 200 or 230 N.s concentric impulse in squat jump did not necessarily increase swim start performance over 5 m and 15 m, respectively. Swimmers who can already generate greater levels of concentric impulse may benefit more from improving their rate of force development and/or technical aspects of the swim start performance. The sex-related differences in key force-time predictors suggest that male and female swimmers may require individualised strength and conditioning programs and regular monitoring of performance.

In this study, we report the first allometric equations relating gait parameters and swimming speed to body size for fish employing pectoral fin locomotion. Comparisons of locomotor kinematics and performance among striped surfperch (Teleostei: Embiotocidae) are made at the pectoral&shy;caudal gait transition speed (Up-c). Up-c is considered to elicit physiologically equivalent levels of exercise in animals varying over 100-fold in body mass (Mb) by virtue of dynamically similar pectoral fin movements (constant duty factor, length-specific stride length and fin-beat amplitude) and size-independent propulsive efficiency. At Up-c, pectoral fin-beat frequency scales in proportion to Mb-0.12&plusmn;0.03, a size-dependence consistent with that observed for stride frequency in fishes swimming by axial undulatory propulsion and in many running tetrapods. It is proposed that the similarity in the scaling of frequency in these vertebrate groups reflects an underlying similarity in the allometry of the maximal velocity of muscle shortening. Absolute Up-c (m s-1) generally increases with body size, but the fastest speeds are not exhibited by the largest animals. A pattern of declining performance in fish 23 cm in standard length and longer may be related to their disproportionately small fin areas and aspect ratios. The pronounced negative allometry of Up-c expressed as standard body lengths per second indicates that a given length-specific speed does not induce comparable levels of activity in large and small fish. Thus, normalization of swimming speed to body length may not be a sufficient correction for kinematic comparisons across size.

Coordinated motion of cilia is a fascinating and vital aspect of very diverse forms of eukaryotic life, enabling swimming and propulsion of fluid across cellular epithelia. There are many questions still unresolved, and broadly they fall into two classes. (i) The mechanism of how cilia physically transmit forces onto each other. It is not known for many systems if the forces are mainly of hydrodynamical origin, or if elastic forces within the cytoskeleton are important. (ii) In those systems where we know that forces are purely hydrodynamical, we do not have a framework for linking our understanding of how each cilium behaves in isolation to the collective properties of two or more cilia. In this work, we take biological data of cilia dynamics from a variety of organisms as an input for an analytical and numerical study. We calculate the relative importance of external flows versus internal cilia flows on cilia coupling. This study contributes to both the open questions outlined above: firstly, we show that it is, in general, incorrect to infer cilium–cilium coupling strength on the basis of experiments with external flows, and secondly, we show a framework to recapitulate the dynamics of single cilia (the waveform) showing classes that correspond to biological systems with the same physiological activity (swimming by propulsion, versus forming collective waves). This article is part of the Theo Murphy meeting issue ‘Unity and diversity of cilia in locomotion and transport’.

Buoyancy control is a fundamental aspect of aquatic life that has major implications for locomotor performance and ecological niche. Unlike terrestrial animals, the densities of aquatic animals are similar to the supporting fluid, thus even small changes in body density may have profound effects on locomotion. Here, we analysed the body composition (lipid versus lean tissue) of 32 shark species to study the evolution of buoyancy. Our comparative phylogenetic analyses indicate that although lean tissue displays minor positive allometry, liver volume exhibits pronounced positive allometry, suggesting that larger sharks evolved bulkier body compositions by adding lipid tissue to lean tissue rather than substituting lean for lipid tissue, particularly in the liver. We revealed a continuum of buoyancy control strategies that ranged from more buoyant sharks with larger livers in deeper ecosystems to relatively denser sharks with small livers in epipelagic habitats. Across this eco-morphological spectrum, our hydrodynamic modelling suggests that neutral buoyancy yields lower drag and more efficient steady swimming, whereas negative buoyancy may be more efficient during accelerated movements. The evolution of buoyancy control in sharks suggests that ecological and physiological factors mediate the selective pressures acting on these traits along two major gradients, body size and habitat depth.

Abstract Impacts of fisheries-induced evolution may extend beyond life history traits to more cryptic aspects of biology, such as behaviour and physiology. Understanding roles of physiological traits in determining individual susceptibility to capture in fishing gears and how these mechanisms change across contexts is essential to evaluate the capacity of commercial fisheries to elicit phenotypic change in exploited populations. Previous work has shown that metabolic traits related to anaerobic swimming may determine individual susceptibility to capture in trawls, with fish exhibiting higher anaerobic performance more likely to evade capture. However, high densities of fish aggregated ahead of a trawl net may exacerbate the role of social interactions in determining an individual fish’s behaviour and likelihood of capture, yet the role of social environment in modulating relationships between individual physiological traits and vulnerability to capture in trawls remains unknown. By replicating the final moments of capture in a trawl using shoals of wild minnow (Phoxinus phoxinus), we investigated the role of individual metabolic traits in determining susceptibility to capture among shoals of both familiar and unfamiliar conspecifics. We expected that increased shoal cohesion and conformity of behaviour in shoals of familiar fish would lessen the role of individual metabolic traits in determining susceptibility to capture. However, the opposite pattern was observed, with individual fish exhibiting high anaerobic capacity less vulnerable to capture in the trawl net, but only when tested alongside familiar conspecifics. This pattern is likely due to stronger cohesion within familiar shoals, where maintaining a minimal distance from conspecifics, and thus staying ahead of the net, becomes limited by individual anaerobic swim performance. In contrast, lower shoal cohesion and synchronicity of behaviours within unfamiliar shoals may exacerbate the role of stochastic processes in determining susceptibility to capture, disrupting relationships between individual metabolic traits and vulnerability to capture.

Animals from polar seas exhibit numerous so called resistance adaptations that serve to maintain homeostasis at low temperature and prevent lethal freezing injury. Specialization to temperatures at or below 0 °C is associated with an inability to survive at temperatures above 3-8 °C. Polar fish synthesize various types of glycoproteins or peptides to lower the freezing point of most extracellular fluid compartments in a non-colligative manner. Antifreeze production is seasonal in boreal species and is often initiated by environmental cues other than low temperature, particularly short day lengths. Most of the adaptations that enable intertidal invertebrates to survive freezing are associated with their ability to withstand ariel exposure. Unique adaptations for freezing avoidance include the synthesis of low molecular mass ice-nucleating proteins that control and induce extracellular ice-formation. Marine poikilotherms also exhibit a range of capacity adaptations that increase the rate of some physiological processes so as to partially compensate for the effects of low temperature. However, the rate of embryonic development in a diverse range of marine organisms shows no evidence of temperature compensation. This results in a significant lengthening of the time from fertilization to hatching in polar, relative to temperate, species. Some aspects of the physiology of polar marine species, such as low metabolic and slow growth rates, probably result from a combination of low temperature and other factors such as the highly seasonal nature of food supplies. Although neuromuscular function shows a partial capacity adaptation in Antarctic fish, maximum swimming speeds are lower than for temperate and tropical species, particularly for early stages in the life history.

ABSTRACT Most swimming bacteria are capable of following gradients of nutrients, signaling molecules and other environmental factors that affect bacterial physiology. This tactic behavior became one of the most-studied model systems for signal transduction and quantitative biology, and underlying molecular mechanisms are well characterized in Escherichia coli and several other model bacteria. In this review, we focus primarily on less understood aspect of bacterial chemotaxis, namely its physiological relevance for individual bacterial cells and for bacterial populations. As evident from multiple recent studies, even for the same bacterial species flagellar motility and chemotaxis might serve multiple roles, depending on the physiological and environmental conditions. Among these, finding sources of nutrients and more generally locating niches that are optimal for growth appear to be one of the major functions of bacterial chemotaxis, which could explain many chemoeffector preferences as well as flagellar gene regulation. Chemotaxis might also generally enhance efficiency of environmental colonization by motile bacteria, which involves intricate interplay between individual and collective behaviors and trade-offs between growth and motility. Finally, motility and chemotaxis play multiple roles in collective behaviors of bacteria including swarming, biofilm formation and autoaggregation, as well as in their interactions with animal and plant hosts.

Objective To explore the fluctuation of reticulocyte during different altitude training in swimming athletes and their difference between altitude training focused on special aerobic capacity and altitude training focused on high load and sprint, to provide the theory basis for further analyze the altitude training improve the physiological function and athletic performance. Methods Twenty female swimming athletes participated in altitude training for four weeks, which could be divided into two patterns, special aerobic capacity group(G1, n=9) and intensity and sprint group(G2, n=11). Fasting venous blood samples were drawn for each week were determined using Beckman Coulter LH780 automated hematology analyzer, including Reticulocyte related parameters such as Reticulocyte percentage (Ret%), Reticulocyte count (Ret#) and immature Reticulocyte fraction (IRF) and also erythrocyte related parameters. Results (1) In G1, Ret%, Ret# and MRV showed continuous decline and represented minimum level in 4th week. While IRF increased during 2nd and 3rd, and then decreased in 4th week. (2) In G2, Ret%, Ret# and MRV were relatively steady during 1st and 2nd week. Ret% and Ret# gave an increased in 3rd week, and then decreased in 4th week, while MRV decreased in 3rd week and increased in 4th week. IRF significantly decreased in latter period compared to earlier period. (3) There were no significant changes for RBC, HCT and HGB in both G1 and G2. MCV, MCH, MCHC and RDW showed improved in later stages compared to their in earlier stages for all in G1, while MCV increased and then decreased, MCH and MCHC continued decline, and RDW kept at sustaining higher levels in G2. Conclusions (1) Reticulocytes were not in accordance with the trend of erythrocyte during different altitude training. Compared to erythrocyte, the behavior of Reticulocyte could reflect erythropoiesis, and IRF could more sensitively detect the change of bone marrow stimulation in particular. (2) The variability of Reticulocytes during altitude training was influenced by hypoxia, training and especially their interactive effects. In aspect of training type, it was crucial for considering the fluctuation of training load and athletes’ adaptation during different patterns.

Of all anomopods, daphniids have been the most successful exponents of life in open water. Many of them are completely independent of the bottom and subsist entirely on seston. A few of them are truly planktonic. Although the family has been intensively studied from many points of view, various morphological attributes have remained either inadequately known or never investigated. Some of these attributes, understanding of which is necessary if functions are to be appreciated, are considered, especially in the genus Daphnia , with which other genera are later compared. They include aspects of general morphology, the exoskeleton, endoskeleton and muscular system. How Daphnia swims is described, antennal movements being analysed from high-speed cine films. Locomotion is clearly derived from a naupliar mechanism, though the nauphus has long been eliminated from the anomopod life cycle. Antennal beat is more versatile than is immediately apparent and the animals are capable of far more complex manoeuvres than the simple ‘hop and sink' movements in which they often indulge. The trunk limbs are responsible for collecting and manipulating the food. Their morphology and arrangement are discussed and their armature, especially as revealed by scanning electron microscopy, is considered. The armature of limbs 3 and 4 dominates the trunk limb complex and makes up an extensive filter chamber. The mouthparts and labrum are basically the same as those already described in detail for other anomopods, but the labrum lacks a keel. A wide range of particulate foods is consumed. A detailed account is given of the feeding mechanism, which has been studied both by direct observation and with the aid of high-speed cine-photography. Most of the basic principles involved were elucidated by Cannon, Storch and Eriksson who, however, disagreed on various points. The account now given is more detailed than any previously presented and is supported by numerous illustrations, whose lack has hitherto hindered comprehension. Parts of some of the earlier interpretations are incorrect, sometimes in ways that are not only intrinsically important, but which have led to erroneous views on such matters as the amount of energy expended in filtration. Trunk limb movements follow a regular rhythmic cycle. Water, containing suspended particles, flows into the carapace chamber via the ventral gape to replace that driven out posteriorly by the pumping action of trunk limbs 3 and 4 and their exopodites, is drawn into the filter chamber and through the filters borne on limbs 3 and 4 into interlimb spaces, from which it is finally expelled posteriorly. Trunk limb 5, whose movements initiate both promotion (the suction and filtration phase of the cycle) and remotion (the expulsion phase), seals the posterior interlimb space posteriorly during promotion of the limbs. There is no pressing of water through the filters during remotion of the limbs. Filtration occurs during approximately half the cycle. Notwithstanding claims to the contrary, the filter plates of trunk limbs 3 and 4 are correctly designated as such and serve as filters. Material abstracted by the filter plates is cleaned off by a series of devices, seven in all, passed into the median food groove, and swept forward by mechanical means to the mouthparts. The mandibles display a high degree of both skeletal and muscular asymmetry, which improves their performance. Any excess food material collected in the food groove is discarded. From the anterior end it is removed by the ejector hooks of the first trunk limbs, then swept out by the post-abdominal claws: from the posterior end it is removed by the post-abdominal claws alone. Errors and shortcomings in certain recent accounts that purport to explain the feeding mechanism are discussed. Trunk limbs 1 and 2 are incapable of filtration and are specialized for roles that have nothing to do with this process. The inapplicability of a model of filtration to the daphniid mechanism is noted and the importance of morphology, even in minute details, is emphasized. Contrary to recent suggestions, the function of ‘bristles’ cannot easily be changed without changes in morphology. The necessity of understanding a mechanism before making calculations is emphasized and examples of misleading calculations, based on erroneous data, are noted. The habits of certain species of Daphnia are described. Both D. magna and D. obtusa are able to settle on their ventral carapace margins and attach themselves to surfaces, over which they can then glide forward, collecting food material by means of scraper-like spines borne distally on the second trunk limbs as they do so. D. magna can also lift accumulations of detritus from the bottom. Such material is then processed in the usual way. Some species sometimes indulge in swarming behaviour, which involves remarkable coordination between individuals. The way in which phenotypic changes in shape occur in Daphnia and the light this throws on phyletic changes in the genus are described, partly by the method of transformation of coordinates, which can be used to show changes in three dimensions, rather than the usual two. The influence of environmental factors is noted. Geographical, ecological and physiological aspects of radiation are considered. Other genera are treated more briefly. Daphniopsis departs little from Daphnia in its functional morphology and may not merit generic separation. Simocephalus attaches itself to a support by means of simple but effective specializations of the antennae and then remains stationary while it filters. This has enabled it to acquire a robust carapace in a way not permitted to Daphnia (of which a few of the more heavily built species sometimes rest on the bottom). Protection is thereby granted. Acquisition of this habit was probably assisted by the way in which Simocephalus swims, predominantly ventral surface uppermost. The feeding mechanism is essentially the same as that of Daphnia. Scapholoberis and Megafenestra have the same orientation during swimming as Simocephalus and have acquired the habit of hanging suspended beneath the surface film by their ventral carapace margins, for which they are highly specialized in morphology and behaviour. Here too the basic daphniid feeding mechanism is employed. Ceriodaphnia has specialized in small size. Although studied in less detail than Daphnia , it clearly has a similar feeding mechanism. Moina and Moinodaphnia are now often separated from the Daphniidae as the family Moinidae, but this seems unjustified. Trunk limb structure and the feeding mechanism are essentially the same as in other daphniids. These two genera, while primitive in certain respects, have a suite of specializations related to the nourishment of eggs and embryos by secretions produced by a Nährboden, or ‘placenta’. This necessitates sealing of the brood pouch, by a device involving the post-abdomen, to prevent loss of the secretion. As embryos grow during development by the accretion of material from without, rather than from stored yolk, distortion and distension of the carapace are necessary to accommodate their increasing volume. The Daphniidae clearly arose from benthic ancestors, some indication of whose morphology and habits is given by certain extant macrothricids. Key features in the evolution of the family, which has existed since at least early Cretaceous times and probably originated even earlier than this, are listed. Of prime importance was the expansion of the gnathobasic filter plates of trunk limbs 3 and 4 at the expense of other filters.

Many studies have shown that the space environment plays a pivotal role in changing the characteristics of conditional pathogens, especially their pathogenicity and virulence. However, Stenotrophomonas maltophilia, a type of conditional pathogen that has shown to a gradual increase in clinical morbidity in recent years, has rarely been reported for its impact in space. In this study, S. maltophilia was exposed to a simulated microgravity (SMG) environment in high-aspect ratio rotating-wall vessel bioreactors for 14days, while the control group was exposed to the same bioreactors in a normal gravity (NG) environment. Then, combined phenotypic, genomic, transcriptomic, and proteomic analyses were conducted to compare the influence of the SMG and NG on S. maltophilia. The results showed that S. maltophilia in simulated microgravity displayed an increased growth rate, enhanced biofilm formation ability, increased swimming motility, and metabolic alterations compared with those of S. maltophilia in normal gravity and the original strain of S. maltophilia. Clusters of Orthologous Groups (COG) annotation analysis indicated that the increased growth rate might be related to the upregulation of differentially expressed genes (DEGs) involved in energy metabolism and conversion, secondary metabolite biosynthesis, transport and catabolism, intracellular trafficking, secretion, and vesicular transport. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that the increased motility might be associated the upregulation of differentially expressed proteins (DEPs) involved in locomotion, localization, biological adhesion, and binding, in accordance with the upregulated DEGs in cell motility according to COG classification, including pilP, pilM, flgE, flgG, and ronN. Additionally, the increased biofilm formation ability might be associated with the upregulation of DEPs involved in biofilm formation, the bacterial secretion system, biological adhesion, and cell adhesion, which were shown to be regulated by the differentially expressed genes (chpB, chpC, rpoN, pilA, pilG, pilH, and pilJ) through the integration of transcriptomic and proteomic analyses. These results suggested that simulated microgravity might increase the level of corresponding functional proteins by upregulating related genes to alter physiological characteristics and modulate growth rate, motility, biofilm formation, and metabolism. In conclusion, this study is the first general analysis of the phenotypic, genomic, transcriptomic, and proteomic changes in S. maltophilia under simulated microgravity and provides some suggestions for future studies of space microbiology.