Changes In Swimming Performance Research Articles

High water temperature significantly influences swimming performance of New Zealand migratory species.

Anthropogenic structures in freshwater systems pose a significant threat by fragmenting habitats. Effective fish passage solutions must consider how environmental changes introduce variability into swimming performance. As temperature is considered the most important external factor influencing fish physiology, it is especially important to consider its effects on fish swimming performance. Even minor alterations in water properties, such as temperature and velocity, can profoundly affect fish metabolic demands, foraging behaviours, fitness and, consequently, swimming performance and passage success. In this study, we investigated the impact of varying water temperatures on the critical swimming speeds of four migratory New Zealand species. Our findings revealed a significant reduction in critical swimming speeds at higher water temperatures (26°C) compared to lower ones (8 and 15°C) for three out of four species (Galaxias maculatus, Galaxias brevipinnis and Gobiomorphus cotidianus). In contrast, Galaxias fasciatus exhibited no significant temperature-related changes in swimming performance, suggesting species-specific responses to temperature. The cold temperature treatment did not impact swimming performance for any of the studied species. As high water temperatures significantly reduce fish swimming performance, it is important to ensure that fish passage solutions are designed to accommodate a range of temperature changes, including spatial and temporal changes, ranging from diel to decadal fluctuations. Our research underscores the importance of incorporating temperature effects into fish passage models for habitat restoration, connectivity initiatives, and freshwater fish conservation. The influence of temperature on fish swimming performance can alter migration patterns and population dynamics, highlighting the need for adaptive conservation strategies. To ensure the resilience of freshwater ecosystems it is important to account for the impact of temperature on fish swimming performance, particularly in the context of a changing climate.

Effect of different concentrations of biodegrader (Bacillus subtilis) on the survival of fingerlings in crude oil polluted environment

The role of various concentrations of hydrocarbon degraders (Bacillus subtilis) in the survivability of Clarias gariepinus reared in hydrocarbon polluted aquaria was investigated under laboratory conditions using standard microbiological and analytical protocols. Six aquaria containing ten fingerlings each were contaminated with 100ml of crude oil and different amount (5ml, 10ml, 15ml and 20ml) of hydrocarbon degraders (Bacillus subtilis) in broth culture were introduced into each of the aquarium. The set-up which was adequately aerated was monitored for 21 days for survivability of the fingerslings. The results revealed changes in swimming performance and feeding pattern of the fingerlings after crude oil contamination. Reduction in swimming was observed in those fingerlings with less hydrocarbon biodegraders. Similarly, the feeding habit of those fingerlings with less hydrocarbon degraders decreased significantly. The aquarium with no biodegrader recorded 3,2 and 3 deaths on the 1st, 2nd and 3rd week respectively while the aquarium with the highest biodegraders recorded 2, 2 and 0 death on the 1st, 2nd and 3rd week respectively. The rate of death of the fingerlings revealed that increase in hydrocarbon biodegraders in the aquarium increased the survival of the fingerlings in the aquarium. Specifically, it was observed that aquarium with the highest biodegrader (20ml) recorded the lowest mortality of 40% at the end of 21 days. No mortality was recorded in aquarium with no crude oil contamination. This study revealed that in the aquarium with highest hydrocarbon degraders, the effect of crude oil was quickly neutralised thus eliminating the mortality of the exposed fingerlings on the third week of the experiment.

Design, Fabrication, and Characterization of a Helical Adaptive Multi-Material MicroRobot (HAMMR)

Adaptive locomotion is an advanced function of microrobots that can be achieved using smart materials. In this letter, a responsive hydrogel is utilized as a smart material and used to fabricate Helical Adaptive Multi-material MicroRobots (HAMMRs) with deformable tails to achieve adaptive locomotion capabilities. Moreover, a novel fabrication method is proposed to realize these types of helical microrobots with enhanced swimming performances by taking advantage of a strong magnetic head and deformable tail. The deformations of different tail designs and the fabricated microrobots are tested in different solvents. The swimming performances of the swimming microrobots are investigated experimentally under a rotating magnetic field and verified with theoretical calculations. The HAMMRs show significant deformations upon stimulation and changes in swimming performance which are in agreement with the scaled calculation result. Finally, the HAMMRs present an enhanced mobility with a highest published translational velocity for an adaptive swimming microrobot of 8.1 body length per second.

Biophysical Impact of 5-Week Training Cessation on Sprint Swimming Performance.

To assess changes in swimming performance, anthropometrics, kinematics, energetics, and strength after 5-week training cessation. Twenty-one trained and highly trained swimmers (13 males: 17.4 [3.1]y; 50-m front crawl 463 [77] FINA points; 8 females: 16.7 [1.7]y; 50-m front crawl 535 [48] FINA points) performed a 50-m front-crawl all-out swim test, dryland and pool-based strength tests, and 10-, 15-, 20-, and 25-m front-crawl all-out efforts for anaerobic critical velocity assessment before and after a 5-week training cessation. Heart rate and oxygen uptake (V˙O2) were continuously measured before and after the 50-m swim test (off-kinetics). Performance was impaired 1.9% (0.54s) for males (P = .007, d = 0.91) and 2.9% (0.89s) for females (P = .033, d = 0.93). Neither the anthropometrical changes (males: r2 = .516, P = .077; females: r2 = .096, P = .930) nor the physical activities that each participant performed during the off-season (males: r2 = .060, P = .900; females: r2 = .250, P = .734) attenuated performance impairments. Stroke rate and clean swimming speed decreased (P < .05), despite similar stroke length and stroke index (P > .05). Blood lactate concentrations remained similar (P > .05), but V˙O2 peak decreased in females (P = .04, d = 0.85). Both sexes showed higher heart rate before and after the 50-m swim test after 5 weeks (P < .05). Anaerobic metabolic power deterioration was only observed in males (P = .035, d = 0.65). Lower in-water force during tethered swimming at zero speed was observed in males (P = .033, d = 0.69). Regarding dryland strength, lower-body impairments were observed for males, while females showed upper-body impairments (P < .05). A 5-week training cessation yielded higher heart rate in the 50-m front crawl, anaerobic pathways, and dryland strength impairments. Coaches should find alternatives to minimize detraining effects during the off-season.

Morphological predictors of swimming speed performance in river and reservoir populations of Australian smelt Retropinna semoni.

Dam construction is a major driver of ecological change in freshwater ecosystems. Fish populations have been shown to diverge in response to different flow velocity habitats, yet adaptations of fish populations to river and reservoir habitats created by dams remains poorly understood. We aimed to evaluate divergence of morphological traits and prolonged swimming speed performance between lotic and lentic populations of Australian smelt Retropinna semoni and quantify the relationship between prolonged swimming speed performance and morphology. Prolonged swimming speed performance was assessed for 15 individuals from each of three river and two reservoir populations of R. semoni using the critical swimming speed test (Ucrit ). Body shape was characterized using geometric morphometrics, which was combined with fin aspect ratios and standard length to assess morphological divergence among the five populations. Best subsets model-selection was used to identify the morphological traits that best explain Ucrit variation among individuals. Our results indicate R. semoni from river populations had significantly higher prolonged swimming speed performance (Ucrit = 46.61 ± 0.98 cm s-1 ) than reservoir conspecifics (Ucrit = 35.57 ± 0.83 cm s-1 ; F1,74 = 58.624, Z = 35.938, P < 0.001). Similarly, R. semoni sampled from river populations had significantly higher fin aspect ratios (ARcaudal = 1.71 ± 0.04 and 1.29 ± 0.02 respectively; F(1,74) = 56.247, Z = 40.107, P < 0.001; ARpectoral = 1.85 ± 0.03 and 1.33 ± 0.02 respectively; F(1,74) = 7.156, Z = 4.055, P < 0.01). Best-subset analyses revealed Ucrit was most strongly correlated with pectoral and caudal fin aspect ratios (R2 adj = 0.973, AICc = 41.54). Body shape, however, was subject to a three-way interaction among population, habitat and sex effects (F3,74 = 1.038. Z = 1.982; P < 0.05). Thus sexual dimorphism formed a significant component of unique and complex variation in body shape among populations from different habitat types. This study revealed profound effects of human-altered flow environments on locomotor morphology and its functional link to changes in swimming performance of a common freshwater fish. While past studies have indicated body shape may be an important axis for divergence between lotic and lentic populations of several freshwater fishes, fin aspect ratios were the most important predictor of swimming speed in our study. Differences in body morphology here were inconsistent between river and reservoir populations, suggesting this aspect of phenotype may be more strongly influenced by other factors such as predation and sexual dimorphism.

Biophysical Follow-up of Age-Group Swimmers During a Traditional Three-Peak Preparation Program.

Zacca, R, Azevedo, R, Ramos, VR, Abraldes, JA, Vilas-Boas, JP, Castro, FAdS, Pyne, DB, and Fernandes, RJ. Biophysical follow-up of age-group swimmers during a traditional three-peak preparation program. J Strength Cond Res 34(9): 2585-2595, 2020-The aim of this study was to quantify changes and contributions of bioenergetic, technique, and anthropometric profiles across a traditional 3-peak swimming season. Twenty-four age-group swimmers (11 boys: 15 years 6 months ± 1 year 1 month; 13 girls: 14 years 5 months ± 10 months) of equal maturational stage were monitored through a 400-m test in front crawl (T400). Bioenergetic, technique, and anthropometric characteristics were compared before and after macrocycles I, II and III. Sex interaction was verified only for amplitude of the fast oxygen uptake component and height (moderate). Multiple linear regressions and principal component analysis were used to identify the most influential variables and the relative contribution of each domain (bioenergetics, technique, and anthropometrics) to changes in swimming performance of T400. The relative contributions for the performance of T400 after macrocycles I, II, and III were, respectively, 6, 18, and 27% for bioenergetics, 88, 69, and 54% for technique, and 6, 13, and 20% for anthropometrics. Technique was the biggest contributor (71%) for changes in the performance of T400 over the training season, followed by bioenergetics (17%) and anthropometrics (12%). Technique played the main role during the competitive season, regardless of gradual increase in the contribution of bioenergetics and anthropometrics. Despite that, bioenergetics and technique are closely connected, thus a powerful and endurable metabolic base and cannot be overlooked. Changes and contribution of bioenergetics, technique, and anthropometrics on age-group swimmers' performance over a traditional 3-peak swimming season could be described by the T400 swimming test, providing a comprehensive biophysical overview of the main contributors to swimming performance.

In-Season Strength Training in Elite Junior Swimmers: The Role of the Low-Volume, High-Velocity Training on Swimming Performance.

The aim of this study was to analyze the effect of long-term combined strength training (ST) and plyometrics on strength, power and swimming performances in elite junior swimmers during a competitive season. Ten elite junior swimmers (5 women and 5 men) completed the study (age: 16.6 ± 0.7 years; mass: 62.2 ± 5.4 kg; stature: 1.70 ± 0.07 m). The participants trained twice a week during 20 weeks. The ST program consisted of upper- and lower limbs exercises with low loads and low volume, lifting the load at maximal intended velocity. The effect of the training protocol was assessed using the 1RM in the full squat (SQ) and bench press (BP), jump height (CMJ), the maximal number of repetitions completed in the pull-up (PU) exercise and time during 50-m freestyle. Training program resulted in significant improvements in CMJ (12.1%, ES: 0.57), maximal dynamic strength in the SQ (16.4%, ES: 0.46) and BP (12.1%, ES: 0.34) exercises, the maximum number of repetitions completed during the PU test (90.7%, ES: 0.57) and swimming performance (-3.9%, ES: 0.45). There were no significant differences between both genders. The relative changes in swimming performance showed significant relationship with the relative changes in 1RM of SQ for pooled data (r=-0.66, p<0.05) and the relative changes in the PU exercise in female swimmers (r=-0.99, p<0.05). Therefore, coaches and strength and conditioning professionals should consider including in-season dry-land ST programs within the training routine in order to obtain further improvements in swimming performance.

The ontogeny of sea turtle hatchling swimming performance

AbstractSea turtle hatchlings experience high mortality rates during dispersal. To minimize time spent in predator-dense waters, hatchlings typically undergo a period of hyperactivity termed the ‘frenzy’, characterized by almost continuous swimming for ~24 h. Research has focused on swimming performance during the frenzy, but our understanding of changes in swimming performance post-frenzy is limited. Thus, we measured green turtle (Chelonia mydas) hatchling swimming performance during the frenzy and post-frenzy when the turtles were 4, 12 and 24 weeks old. Using load cells, we recorded thrust production, stroke rates and the time turtles spent performing various swimming gaits. We found that the proportion of time spent powerstroking and the thrust generation per powerstroke were the main determinants of overall swimming performance. Older, larger turtles generated more thrust per stroke, but the proportion of time spent powerstroking throughout the entire swimming trial did not differ among age groups. Hatchlings have been thought mainly to use currents to reach nursery foraging grounds, and our findings suggest that hatchling swimming might also play an important role in directing hatchlings to optimal nursery habitats, supporting recent studies. Additionally, turtle size is positively related to swimming performance in post-frenzy turtles, suggesting that faster-growing turtles might have fitness advantages over slower-growing turtles.

The metabolism and swimming performance of sheepshead minnows (Cyprinodon variegatus) following thermal acclimation or acute thermal exposure.

Ectothermic animals are especially susceptible to temperature change, considering that their metabolism and core temperature are linked to the environmental temperature. As global water temperatures continue to increase, so does the need to understand the capacity of organisms to tolerate change. Sheepshead minnows (Cyprinodon variegatus) are the most eurythermic fish species known to date and can tolerate a wide range of environmental temperatures from - 1.9 to 43.0°C. But little is known about the physiological adjustments that occur when these fish are subjected to acute thermal challenges and long-term thermal acclimation. Minnows were acclimated to 10, 21, or 32°C for 4weeks or acutely exposed to 10 and 32°C and then assessed for swimming performance [maximum sustained swimming velocity (Ucrit), optimum swimming velocity (Uopt)] and metabolic endpoints (extrapolated standard and maximum metabolic rate [SMR, MMR), absolute aerobic scope (AS), and cost of transport (COT)]. Our findings show that the duration of thermal exposure (acute vs. acclimation) did not influence swimming performance. Rather, swimming performance was influenced by the exposure temperature. Swimming performance was statistically similar in fish exposed to 21 or 32°C (approximately 7.0 BL s-1), but was drastically reduced in fish exposed to 10°C (approximately 2.0 BL s-1), resulting in a left-skewed performance curve. There was no difference in metabolic end points between fish acutely exposed or acclimated to 10°C. However, a different pattern was observed in fish exposed to 32°C. MMR was similar between acutely exposed or acclimated fish, but acclimated fish had a 50% reduction in extrapolated SMR, which increased AS by 25%. However, this enhanced AS was not associated with changes in swimming performance, which opposes the oxygen-capacity limited thermal tolerance concept. Our findings suggest that sheepshead minnows may utilize two distinct acclimation strategies, resulting in different swimming performance and metabolic patterns observed between 10 and 32°C exposures.

Monitoring Age-Group Swimmers Over a Training Macrocycle: Energetics, Technique, and Anthropometrics.

Zacca, R, Azevedo, R, Chainok, P, Vilas-Boas, JP, Castro, FAdS, Pyne, DB, and Fernandes, RJ. Monitoring age-group swimmers over a training macrocycle: energetics, technique, and anthropometrics. J Strength Cond Res 34(3): 818-827, 2020-The aim of this study was to quantify changes and contributions of energetic, technique, and anthropometric profiles across the first training macrocycle (16-week) in a traditional 3-peak swimming season. Twenty-four age-group swimmers (10 boys and 14 girls age 14.4 ± 0.9 years) of equal maturational stage were monitored through a 400-m test in front crawl (T400). Energetic, technique, and anthropometric characteristics were compared before (experimental testing 1, E1) and after the preparatory (E2), specific (E3), and competitive (E4) training periods. Sex interaction was not significant for any variable. Multiple linear regressions and principal component analysis were used to identify the most influential variables and the relative contribution of each domain (energetics, technique, and anthropometrics) to changes in swimming performance of T400. The relative contributions for performance of T400 at E1, E2, E3, and E4 were 15, 12, 6, and 13% for energetics, 78, 85, 75, and 70% for technique, and 7, 3, 19 and 17% for anthropometrics, respectively. Technique played the main role during the first 16-week macrocycle in a competitive season, regardless of small fluctuations in the influence of energetics and anthropometrics. Changes and influence of energetics, technique, and anthropometric on age-group swimmers' performance could be described by the T400 swimming test, providing a comprehensive biophysical overview of the main contributors to swimming performance.

Effects of Postexercise Sauna Bathing on Recovery of Swim Performance.

Despite indications of positive effects of sauna (SAU) interventions, effects on performance recovery are unknown. The aim of the current study was to investigate acute effects of SAU bathing after an intensive training session on recovery of swim performance. In total, 20 competitive swimmers and triathletes (3 female and 17 male) with a minimum of 2 y of competition experience (national level or higher) participated in the study. Athletes completed an intensive training session followed by either a SAU bathing intervention or a placebo (PLAC) condition in a randomized order. SAU consisted of 3 × 8 min of SAU bathing at 80-85°C, whereas during PLAC, athletes applied a deidentified, pH-balanced massage oil while passively resting in a seated position. Prior to training, swimmers conducted a 4 × 50-m all-out swim test that was repeated on the following morning. Furthermore, subjective ratings of fatigue and recovery were measured. Swimmers performed significantly worse after SAU (4 × 50-m pre-post difference: +1.69s) than after PLAC (-0.66s; P = .02), with the most pronounced decrease in the first 50m (P = .04; +2.7%). Overall performance of 15 athletes deteriorated (+2.6s). The subjective feeling of stress was significantly higher after SAU than after PLAC (P = .03). Based on published findings, the smallest substantial change in swimming performance is an increase in time of more than 1.2 s; thus, the observed reductions appear relevant for competitive swimmers. According to the current results, coaches and athletes should be careful with postexercise SAU if high-intensity training and/or competitions are scheduled on the following day.

How cold is too cold? Establishing the minimum water temperature limits for marathon swim racing

ObjectivesTo provide a rationale for minimum water temperature rules for elite and subelite marathon swim racing and highlight factors that make individuals vulnerable to excessive cooling during open water swimming.Methods12...

Acute exposure to methylmercury chloride induces fast changes in swimming performance, cognitive processes and oxidative stress of zebrafish (Danio rerio) as reference model for fish community

Fishes are the first group of vertebrates that respond when the environment is contaminated with pollutants resulted from anthropogenic activities. The development of the toxicity tests is bringing new evidence about the toxicological effects of the pollutants upon the life forms. Behavioural abnormalities in the swimming performance and cognitive processes were well associated with the response of organisms to pollutants from environment. The aim of the paper was to study the behavioural changes of zebrafish (memory, swimming performances and aggression) and oxidative stress (superoxide dismutase and malondialdehyde) during 32 h of acute exposure with methylmercury (II) chloride to measure its neurotoxicity effects upon fish community. The experiments from this study tested and measured the fish community response to methylmercury concentrations (1 μg L−1 and 15 μg L−1) in the first hours after it contamination based on zebrafish model. The changes of the behaviour in the case of a fish species may lead in the end to their population reduction based on less reproductive success, lower food resource exploitation and problems in the predator avoidance. The behavioural tests described in the present study can be applied to measure the neurotoxicity of other metals compounds, to do plans and protocols for avoiding future ecological disasters. The behavioural changes of zebrafish exposed to methylmercury (II) chloride were similar to mammal models and they will have applications in future research.

Metabolic, behavioral, and locomotive effects of feeding in five cyprinids with different habitat preferences.

Fish generally perform routine swimming behaviors during food digestion; thus, changes in swimming performance and adjustments to spontaneous behavior resulting from digestion can have important ecological significance for wild fishes. The effects of feeding on metabolism, spontaneous activity, fast-start escape movement, and critical swimming speed (U crit) were investigated in five cyprinids with different habitat preferences, specifically the Chinese crucian carp (Carassius auratus), common carp (Cyprinus carpio), black carp (Mylopharyngodon piceus), Chinese bream (Parabramis pekinensis), and qingbo (Spinibarbus sinensis). Generally, species in still water exhibited increased feeding metabolism, whereas species in flowing water showed higher spontaneous activity and locomotion performance. Digestion had no significant effects on either spontaneous activity or fast-start escape movement in the five cyprinids. These results could be due to the small meal sizes (approximately 2% body mass) and active foraging modes of cyprinids. The changes in aerobic swimming performance due to feeding were more complex. No effect of digestion on U crit was observed in crucian carp (still water, high feeding metabolism, and low U crit), common carp (widely distributed, high feeding metabolism, and high U crit), and qingbo (flowing water, low feeding metabolism, and high U crit), but digestion resulted in a significant decrease in the U crit of Chinese bream (moderate feeding metabolism but high U crit) and black carp (moderate feeding metabolism and low U crit), suggesting no connection between postprandial U crit changes and feeding metabolism (or between U crit and preferred habitat). The maximum metabolic rate (MMR) of common carp and crucian carp increased after feeding, whereas the corresponding values for the other three cyprinids remained the same. The oxygen uptake capacity appears to meet the oxygen demand of both aerobic swimming and digestion in common carp and crucian carp, whereas qingbo sacrifices digestion for locomotion, and black carp and Chinese bream sacrifice locomotion for digestion under postprandial swimming conditions. The locomotion-priority mode of qingbo is adaptive to its active foraging mode in the demanding swimming habitat of rapidly flowing water, whereas the high respiratory capacities of postprandial crucian carp and common carp and hence the maintenance of their aerobic swimming performances might be a by-product of natural selection for hypoxia tolerance rather than for swimming speed.

Effect of weight and frontal area of external telemetry packages on the kinematics, activity levels and swimming performance of small-bodied sharks.

This study sought to observe the effects of submerged weight and frontal cross-sectional area of external telemetry packages on the kinematics, activity levels and swimming performance of small-bodied juvenile sharks, using lemon sharks Negaprion brevirostris (60-80 cm total length, LT ) as a model species. Juveniles were observed free-swimming in a mesocosm untagged and with small and large external accelerometer packages that increased frontal cross-sectional area of the animals and their submerged weight. Despite adhering to widely used standards for tag mass, the presence of an external telemetry package altered swimming kinematics, activity levels and swimming performance of juvenile N. brevirostris relative to untagged individuals, suggesting that tag mass is not a suitable standalone metric of device suitability. Changes in swimming performance could not be detected from tail-beat frequency, which suggests that tail-beat frequency is an unsuitable standalone metric of swimming performance for small N. brevirostris. Lastly, sharks experienced treatment-specific changes in activity level and swimming kinematics from morning to afternoon observation. Therefore, the presence of external telemetry packages altered the kinematics, activity levels and swimming performance of small young-of-the-year N. brevirostris and these data may therefore be relevant to other similar-sized juveniles of other shark species.

Q10 measures of metabolic performance and critical swimming speed in King George whiting Sillaginodes punctatus.

This study examined thermally driven changes in swimming performance and aerobic metabolism (Q10 and aerobic scope of activity) of adult King George whiting Sillaginodes punctatus to the coldest (16° C) and the warmest (26° C) temperature encountered by this species. Compensation of aerobic scope, higher maximal swimming speeds and a maintained capacity to repay oxygen debt indicate that this species is capable of thermal acclimation to conditions expected under global warming.

东方蝾螈幼体热耐受性和游泳表现的热驯化响应

东方蝾螈幼体热耐受性和游泳表现的热驯化响应

Male sexually coercive behaviour drives increased swimming efficiency in female guppies.

Summary Sexual coercion of females by males is widespread across sexually reproducing species. It stems from a conflict of interest over reproduction and exerts selective pressure on both sexes. For females, there is often a significant energetic cost of exposure to male sexually coercive behaviours.Our understanding of the efficiency of female resistance to male sexually coercive behaviour is key to understanding how sexual conflict contributes to population level dynamics and ultimately to the evolution of sexually antagonistic traits.Overlooked within this context are plastic physiological responses of traits within the lifetime of females that could moderate the energetic cost imposed by coercive males. Here, we examined whether conflict over the frequency and timing of mating between male and female guppies Poecilia reticulata can induce changes in swimming performance and aerobic capacity in females as they work to escape harassment by males.Females exposed to higher levels of harassment over a 5‐month period used less oxygen to swim at a given speed, but displayed no difference in resting metabolic rate, maximal metabolic rate, maximal sustained swimming speed or aerobic scope compared to females receiving lower levels of harassment.The observed increase in swimming efficiency is at least partially related to differences in swimming mechanics, likely brought on by a training effect of increased activity, as highly harassed females spent less time performing pectoral fin‐assisted swimming.Sexual conflict results in sexually antagonistic traits that impose a variety of costs, but our results show that females can reduce costs through phenotypic plasticity. It is also possible that phenotypic plasticity in swimming physiology or mechanics in response to sexual coercion can potentially give females more control over matings and affect which male traits are under selection.

Co-evolution of offspring antipredator competence and parental brood defense in convict cichlids

Convict cichlids are Neotropical freshwater fish with biparental brood defense of their free-swimming young. In this study, we correlate ontogenetic changes in swimming performance measured by maximum velocity and burst speeds with skeletal ossification of larvae and consider how these data provide insights into the proximate mechanisms for the evolution of parental care. In lab tests, swimming velocity and acceleration of the young increased nonlinearly with body length with a rapid improvement at 7 mm in standard length (SL). The timing of abrupt improvement in swimming velocity and acceleration coincided with the timing of skeletal ossification from cartilage to bone. Radii of defended broods in the field reflected the interaction of parental defense competence and offspring antipredator competence. In the Rio Cabuyo, Costa Rica, brood radii increased steadily until the young were 6.45 mm SL, and then plateaued. Taken together, these data indicate interdependent and co-evolved traits that encompass larval ontogenetic development, antipredator performance, habitat-specific predation regime, and parental care.

Will women soon outperform men in open-water ultra-distance swimming in the ‘Maratona del Golfo Capri-Napoli’?

This study investigated the change in sex differences across years in ultra-distance swimming performances at the 36-km ‘Maratona del Golfo Capri-Napoli’ race held from 1954 to 2013. Changes in swimming performance of 662 men and 228 women over the 59-year period were investigated using linear, non-linear and hierarchical regression analyses. Race times of the annual fastest swimmers decreased linearly for women from 731 min to 391 min (r2 = 0.60, p < 0.0001) and for men from 600 min to 373 min (r2 = 0.30, p < 0.0001). Race times of the annual top three swimmers decreased linearly between 1963 and 2013 for women from 736.8 ± 78.4 min to 396.6 ± 4.5 min (r2 = 0.58, p < 0.0001) and for men from 627.1 ± 34.5 min to 374.1 ± 0.3 min (r2 = 0.42, p < 0.0001). The sex difference in performance for the annual fastest decreased linearly from 39.2% (1955) to 4.7% (2013) (r2 = 0.33, p < 0.0001). For the annual three fastest competitors, the sex difference in performance decreased linearly from 38.2 ± 14.0% (1963) to 6.0 ± 1.0% (2013) (r2 = 0.43, p < 0.0001). In conclusion, ultra-distance swimmers improved their performance at the ‘Maratona del Golfo Capri-Napoli’ over the last ~60 years and the fastest women reduced the gap with the fastest men linearly from ~40% to ~5-6%. The linear change in both race times and sex differences may suggest that women will be able to achieve men’s performance or even to outperform men in the near future in an open-water ultra-distance swimming event such as the ‘Maratona del Golfo Capri-Napoli’.