Swimming Rate Research Articles

Can varying photoperiod regimes alter the growth response, behaviour and physiology of <i>Clarias gariepinus</i>?

To understand the welfare implication of photoperiod manipulation on Clarias gariepinus, fingerlings (n = 108) and juveniles (n = 108) of C. gariepinus with a mean weight of 3.75±0.03 g and 21.7±2.88 g were exposed to zero light (0L:24D)-T1, average light (12L:12D)-T2 and continuous light (24L:0D)-T3 in triplicates for 35 days. The highest mortality rate was recorded in T2 and T3 for the fingerlings (13.9%) and juveniles (22.2%). T1 recorded a significantly higher (p = 0.03) weekly growth rate and mean weight gain (MWG). Specific Growth Rate (SGR) and Feed Conversion Ratio (FCR) were highest in T1 for both fingerlings and juveniles. Lowest average swimming rate was observed in T1 while the highest aggressive act, bruises, and scars were recorded in T3 for fingerlings and juveniles. The highest (58.6 mg/dl and 56.9 mg/dl) plasma glucose was found in T3 for both fish categories. There were no significant differences (P = 0.11) among the average cortisol levels of both categories of fish at the different photoperiod regimes. Fingerlings and juveniles exposed to 24-hour darkness had a higher MWG, survival rate, SGR and FCR without any physiological stress. A photoperiod regime of 24-hour darkness is recommended for the culture of fingerlings and juveniles of C. gariepinus to boost fish production in the Aquaculture sector.

Effect of non-permeable cryoprotectant sucrose on the development of spotted knifejaw (Oplegnathus punctatus) embryos

In this study, the toxicity of sucrose to Oplegnathus punctatus embryos was evaluated. Embryos at the 4–6 somite, tail-bud, heart formation, and heart-beating stages were exposed to 0, 0.5, 1,1.5, 2, 2.5, or 3 M sucrose for 1 h. Survival rates of embryos at the tail-bud, heart formation, and heart-beating stages after rehydration for 1 h were not affected by treatment with 2 M sucrose (the maximum concentration). Embryos at the tail-bud, heart formation, and heart-beating stages were exposed to 2 M sucrose for 0, 30, 60, 90, 120, 150, or 180 min. Long-term developmental indicators, including rates of survival, hatching, swimming, and malformation, were evaluated for 4 days after rehydration. Based on the survival rates 10 min after rehydration, the longest tolerance time for embryos at the three stages was 120 min. Based on long-term developmental indicators, the longest tolerance times were 60 min at the tail-bud, 60 min at the heart formation stage and 30 min at the heart beating stage. The malformation rates increased as the treatment time increased. The malformation rates were 100% when embryos were exposed to sucrose for ≥120 min. Malformation was divided into larval and embryonic abnormality. As the exposure time increased for tail-bud stage embryos, the rate of larval malformation increased. Treatment at heart formation and heart-beating stages resulted in higher rates of failure to hatch at exposure time. Based on these results, toxicity tests of non-permeable cryoprotectant in embryos requires the observation of development for at least 2 days after rehydration. Based on long-term observation, it was concluded that dehydration before freezing was not the direct cause of larvae deformity that hatched from frozen-thawing embryo. These results provide a reference for the singly use of representative non-permeable cryoprotectant sucrose.

First successful production of adult corals derived from cryopreserved larvae

Coral reefs worldwide are declining due to increasing concentrations of greenhouse gases, which, combined with local anthropogenic pressure, are exacerbating unprecedented mass coral bleaching. For corals to survive, restoring coral reefs through cryopreservation is crucial. The aim of this study was to vitrify and laser-warm Stylophora pistillata planulae to allow for feasible settlement, post-settlement survival, and the production of adult corals. The no-observed-effect concentrations were used to determine the best cryoprotective agents for S. pistillata. The larvae were then subjected to cooling and nanolaser warming (300 V, 10 ms pulse width, 2 mm beam diameter) by using two vitrification solutions (VSs; VS1: 2 M dimethyl sulfoxide and 1 M ethylene glycol and VS2: 2M EG and 1M DMSO and gold nanoparticles. The results revealed that VS1-treated larvae had a higher vitrification rate (65%), swimming rate (23.1%), settlement rate (11.54%), and post settlement survival rate (11.54%) than those treated with VS2. Seasonal variations also affected the cryopreservation of the planulae; VS1 was more favorable for the planulae in spring than in fall. Although laser-warmed larvae developed slower morphologically than their controlled counterparts, the production of adult S. pistillata corals from cryopreserved larvae was achieved. The proposed technique can improve the cryopreservation of corals and advance efforts to protect endangered coral species.

The Soft Ray-Inspired Robots Actuated by Solid-Liquid Interpenetrating Silicone-Based Dielectric Elastomer Actuator.

Dielectric elastomer actuators (DEAs) are widely used in robotics and artificial muscles because of their large energy densities and short response time. In this study, we developed two types of soft ray-inspired robots using solid-liquid interpenetrating silicone-based DEAs, named SIS DEAs. The optimized SIS DEA had an actuation strain of 79.8% at 20.43 kV/mm in a freestanding state, which was used as the muscle of the ray robot. To imitate the swimming behavior of the ray, the effect of the driving frequency on the velocity of the ray robot was explored. The ray robot achieved a maximum swimming rate of 5.7 mm/s when the driving frequency was ∼0.6 Hz. In addition, the steady-state and the transient simulation were carried out to reveal the mechanism of the ray robot's electro-swimming. The results revealed that the actuating deformation of the SIS DEAs caused the electro-deformation of the ray robot, and the periodical electro-deformation generated the high-speed vortex beneath the robot to push the ray robot forward. The high actuation strain in the freestanding state and the shape customizability of the SIS DEAs made it an ideal alternative to muscles for various soft robots.

Studies on temperature impact (sudden and gradual) of the white-leg shrimp Litopenaeus vannamei.

In the present study, the effect of temperature shock (sudden and gradual) by increasing water temperature from 28°C to 40°C on survival, behavioral responses and immunological changes in Litopenaeus vannamei (L. vannamei) was studied. In sudden temperature shock, experimental groups were maintained at different temperature ranges such as 28°C- 31°C; 28°C-34°C; 28°C-37°C and 28°C-40°C along with 28°C as control. For gradual temperature shock experiments, the initial water temperature was maintained at 28°C for 24h in control and then increased to 1°C for every 24h until reaching 40°C. On reaching the final temperature of 40°C, it was kept stable for 120h. Results indicated that the increasing water temperature (sudden shock) affected survival, behavioral responses and immunological parameter. No shrimp survived at 40°C treatment (sudden), whereas in the gradual temperature shock experiment 20% of animals survived at 40°C. The increasing water temperature had no effects on behavioral responses up to 37°C (gradual), but at 40°C the observation of muscle cramps, low swimming rate, no feeding, muscle and hepatopancreas color turned whitish. Overall, the results suggest that L. vannamei can tolerate water temperature up to 34°C under sudden shock and 37°C under gradual shock conditions. This study reveals that shrimp L. vannamei can self-regulate to a certain extent of temperature variation in the environment.

Behavioral and histo-pathological indices of striped catfish (Pangasionodon hypophthalmus) exposed to different salinities

Salinity intrusion due to climate changes in the coastal area is substantially jeopardized for sustainable aquaculture. This study was focused on behavioral and histo-pathological changes (gills, liver and kidney) of striped catfish (Pangasionodon hypopththalmas) exposed to four salinities (0, 4, 8 and 12 ppt), each with three replications for 56 days. Both behavioral and histological analyses were carried out for durations of 7, 14, 28 and 56 days of exposure. Mild to moderate behavioral abnormalities such as rate of swimming, food intake, gill motion and convulsions were observed in 8 ppt, but pronounced alterations were detected at higher salinity (12 ppt), increasing with longer exposures. Similarly, mild to moderate histological anomalies in gills (hypertrophy of the chloride cell, telangiectasia at the tips of secondary lamellae, epithelial necrosis, fusion of some secondary lamellae and lifting of the lamellar epithelium), liver (vacuolation, blood congestion, melanomacrophage centers, patchy degeneration, necrosis and hypertrophy nucleus) and kidney (degeneration of renal tubule, enlarged Bowman's capsule, increased space in between glomerulus center, melanomacrophage centers, vacuolation and necrotic cell in the hematopoetic tissue) were detected in 8 ppt but pronounced alterations were detected at higher salinity (12 ppt) with increasing the days of exposure. This preliminary study revealed more profound responses to higher salinity exposure in the striped catfish, and this species could serve as a model bio-indicator in costal aquaculture.

A report of Bilharziella polonica cercariae in Knowsley Safari, Prescot, United Kingdom, with notes on other trematodes implicated in human cercarial dermatitis.

As part of surveillance of snail-borne trematodiasis in Knowsley Safari (KS), Prescot, United Kingdom, a collection was made in July 2021 of various planorbid (n = 173) and lymnaeid (n = 218) snails. These were taken from 15 purposely selected freshwater habitats. In the laboratory emergent trematode cercariae, often from single snails, were identified by morphology with a sub-set, of those most accessible, later characterized by cytochrome oxidase subunit 1 (cox1) DNA barcoding. Two schistosomatid cercariae were of special note in the context of human cercarial dermatitis (HCD), Bilharziella polonica emergent from Planorbarius corneus and Trichobilharzia spp. emergent from Ampullacaena balthica. The former schistosomatid was last reported in the United Kingdom over 50 years ago. From cox1 analyses, the latter likely consisted of two taxa, Trichobilharzia anseri, a first report in the United Kingdom, and a hitherto unnamed genetic lineage having some affiliation with Trichobilharzia longicauda. The chronobiology of emergent cercariae from P. corneus was assessed, with the vertical swimming rate of B. polonica measured. We provide a brief risk appraisal of HCD for public activities typically undertaken within KS educational and recreational programmes.

Cardioprotective Effects of Oroxylum indicum Extract Against Doxorubicin and Cyclophosphamide-Induced Cardiotoxicity.

Administration of Chemotherapeutics, especially doxorubicin (DOX) and cyclophosphamide (CPS), is commonly associated with adverse effects such as myelosuppression and cardiotoxicity. At this time, few approved therapeutic options are currently available for the management of chemotherapy-associated cardiotoxicity. Thus, identification of novel therapeutics with potent cardioprotective properties and minimal adverse effects are pertinent in treating Doxorubicin and Cyclophosphamide-induced cardiotoxicity. Oroxylum indicum extract (OIE, Sabroxy®) is a natural product known to possess several beneficial biological functions including antioxidant, anti-inflammatory and cytoprotective effects. We therefore set to investigate the cardioprotective effects of OIE against Doxorubicin and Cyclophosphamide-induced cardiotoxicity and explore the potential cardioprotective mechanisms involved. Adult male mice were treated with DOX and CPS in combination, OIE alone, or a combination of OIE and DOX & CPS. Swimming test was performed to assess cardiac function. Markers of oxidative stress were assessed by levels of reactive oxygen species (ROS), nitrite, hydrogen peroxide, catalase, and glutathione content. The activity of interleukin converting enzyme and cyclooxygenase was determined as markers of inflammation. Mitochondrial function was assessed by measuring Complex-I activity. Apoptosis was assessed by Caspase-3 and protease activity. Mice treated with DOX and CPS exhibited reduced swim rate, increased oxidative stress, increased inflammation, and apoptosis in the heart tissue. These cardiotoxic effects were significantly reduced by co-administration of OIE. Furthermore, computational molecular docking studies revealed potential binding of DOX and CPS to tyrosine hydroxylase which validated our in vivo findings regarding the inhibition of tyrosine hydroxylase activity. Our current findings indicated that OIE counteracts Doxorubicin and Cyclophosphamide-induced cardiotoxicity-through inhibition of ROS-mediated apoptosis and by blocking the effect on tyrosine hydroxylase. Taken together, our findings suggested that OIE possesses cardioprotective effects to counteract potentially fatal cardiac complications associated with chemotherapy treatment.

Toxicity of oleate-based amino protic ionic liquids towards Escherichia coli, Danio rerio embryos and human skin cells

Protic ionic liquids (PILs) have been widely employed with the label of “green solvents'' in different sectors of technology and industry. The studied PILs are promising for corrosion inhibition and lubrication applications in industry. Industrial use of the PILs can transform them in wastes, due to accidental spill or drag in water due to washing, that can reach water bodies. In addition, the handling of the product by the workers can expose them to accidental contact. Thus, the aim of this work is to evaluate the toxicity of PILs 2-hydroxyethylammonium oleate (2-HEAOl), N-methyl-2-hydroxyethylammonium oleate (m-2HEAOl) and bis-2-hydroxyethylammonium oleate (BHEAOl) towards Escherichia coli, zebrafish embryos, model organisms that can be present in water, and human skin cells. This is the first work reporting toxicity results for these PILs, which constitutes its novelty. Results showed that the studied PILs did not inhibit E. coli bacterial growth but could cause human skin cells death at the concentrations of use. LC50 values for zebrafish eggs were 40.21 mg/L for 2HEAOl, 12.92 mg/L for BHEAOl and 32.74 mg/L for m-2HEAOl, with sublethal effects at lower concentrations, such as hatching retarding, low heart rate and absence of free swimming.

Imidazole antifungal drug clotrimazole alters the behavior, brain acetylcholinesterase and oxidative stress biomarkers in African catfish Clarias gariepinus (Burchell 1822)

This study was carried out to determine the effect of clotrimazole (CTZ), an imidazole fungicide on behavior, brain acetylcholinesterase, lipid peroxidation and oxidative stress parameters in Clarias gariepinus juveniles. Fish were acutely exposed to five nominal concentrations of CTZ and control to assess the behavioral effects on fish. To determine the effects on brain acetylcholinesterase, lipid peroxidation and oxidative stress parameters, fish were exposed to three sub-lethal concentrations vis 7.76, 3.89 and 1.94 mg/L which corresponds to 20 10 and 5% of 96 h LC50 value of CTZ respectively and a control for 21 days and allowed to recover for 7 days. The brain, liver and gills were sampled weekly. Fish exposed to different concentrations of the drug displayed behavioral responses such as reduced swimming rate, mucus secretion, decrease in both the feeding frequency and rate. A duration dependent increase in the levels of brain acetylcholinesterase was observed among the exposed groups. The result of the sub-lethal exposure revealed concentration and duration significant increase in lipid peroxidation (LPO), catalase activity (CAT), superoxide dismutase (SOD), reduced glutathione (GSH), glutathione reductase (GR) and glutathione peroxide (GPx) in both the liver and gill tissues of the exposed groups compared to the control. The effects of the drug on many of the observed parameters did not wane after the 7-day withdrawal period. This study revealed that CTZ has a negative impact on the observed parameters, thus providing additional evidence of its toxic effect on non-target aquatic species, especially fish.

A Method for Estimating the Velocity at Which Anaerobic Metabolism Begins in Swimming Fish

Anaerobic metabolism begins before fish reach their critical swimming speed. Anaerobic metabolism affects the swimming ability of fish, which is not conducive to their upward tracking. The initiation of anaerobic metabolism therefore provides a better predictor of flow barriers than critical swimming speed. To estimate the anaerobic element of metabolism for swimming fish, the respiratory metabolism and swimming performance of adult crucian carp (Carassius auratus, mass = 260.10 ± 7.93, body length = 19.32 ± 0.24) were tested in a closed tank at 20 ± 1 °C. The swimming behavior and rate of oxygen consumption of these carp were recorded at various swimming speeds. Results indicate (1) The critical swimming speed of the crucian carp was 0.85 ± 0.032 m/s (4.40 ± 0.16 BL/s). (2) When a power function was fitted to the data, oxygen consumption, as a function of swimming speed, was determined to be AMR = 131.24 + 461.26Us1.27 (R2 = 0.948, p < 0.001) and the power value (1.27) of Us indicated high swimming efficiency. (3) Increased swimming speed led to increases in the tail beat frequency. (4) Swimming costs were calculated via rate of oxygen consumption and hydrodynamic modeling. Then, the drag coefficient of the crucian carp during swimming was calibrated (0.126–0.140), and the velocity at which anaerobic metabolism was initiated was estimated (0.52 m/s), via the new method described herein. This study adds to our understanding of the metabolic patterns of fish at different swimming speeds.

Cardioprotective effects of Oroxylum indicum extract against chemotherapeutics‐induced cardiotoxicity

Cancer chemotherapy, especially doxorubicin (DOX) and cyclophosphamide (CPS) is commonly associated with adverse effects such as myelosuppression and cardiotoxicity. At this time, little approved therapeutic options are available for the management of chemotherapy-associated cardiotoxicity. Thus, identification of novel therapeutics, with potent cardioprotective effects and minimal adverse effects are pertinent in chemotherapy-induced cardiotoxicity. Oroxylum indicum extract (OIE, Sabroxy®) is a natural product known to possess several biological functions including antioxidant, anti-inflammatory and cytoprotective effects. This study was designed to examine whether OIE extract confers protection against chemotherapy-induced cardiotoxicity, and explored potential mechanism involved. Adult male mice were treated with DOX and CPS, OIE or a combination of OIE and DOX & CPS. Swimming test was performed to assess cardiac function. Markers of oxidative stress were assessed by levels of reactive oxygen species (ROS), nitrite, hydrogen peroxide, catalase and glutathione content. Activity of interleukin converting enzyme and cyclooxygenase was determined as markers of inflammation. Mitochondrial function was assessed by measuring complex I activity. Apoptosis was assessed by caspase and protease activity. Mice treated with DOX and CPS exhibited reduced swim rate, increased oxidative stress markers, increased markers of inflammation and apoptosis. These effects were prevented by co-administration of OIE. Furthermore, computational molecular docking revealed potential binding of DOX and CPS to tyrosine hydroxylase and OIE as a potential protective agent. These data indicated that OIE counteracts chemotherapy-induced cardiotoxicity through inhibition of ROS-mediated apoptosis. Taken together, our findings suggested that OIE possesses potential as a means to counteract potentially fatal cardiac complications associated with chemotherapy treatment.

Rhamnolipids on Aedes aegypti larvae: a potential weapon against resistance selection.

The resistance of Aedes aegypti to chemical insecticides has been reported and our work proposes the use of biosurfactants as an alternative larvicide. We evaluated the effect of rhamnolipids against larvae of pyrethroid-resistant and susceptible A. aegypti strains. Time-mortality and sublethal effects were evaluated via survival analysis and swimming behavior, respectively. Rhamnolipids showed larvicidal effect at all tested concentrations. Rhamnolipids at 300mg L-1 killed 100% of both susceptible and resistant larvae within 24h of exposure and 99% after 30-days stored (pyrethroid-susceptible larvae). Regarding the sublethal effects, the swimming rate was reduced in 50 and 100mg L-1 of rhamnolipids in grouped (pyrethroid-susceptible) larvae. Rhamnolipids at 50mg L-1 reduced the distance and speed and increased the number of stops and resting time of individualized pyrethroid-susceptible larvae. The larvicidal effect of the rhamnolipids evaluated demonstrates that these compounds represent an alternative to control A. aegypti.

Anti-Fatigue Activity of a Mixture of Stauntonia hexaphylla (Thunb.) Decaisne and Vaccinium bracteatum Thunb. Fruit Extract.

Stauntonia hexaphylla (Thunb.) Decaisne and Vaccinium bracteatum Thunb. are commonly used in traditional herbal medicine and food and both exhibit antioxidant and anti-inflammatory effects. Herein, hot-water extracts of Stauntonia hexaphylla (Thunb.) Decaisne and Vaccinium bracteatum Thunb. fruits (1:1 mixture) were used to produce a complex extract NET-1601. The anti-fatigue activity of NET-1601 was evaluated in an in vitro oxidative stress model induced by treating C2C12 myotubes with H2O2. An exhaustive swimming test (EST) in vivo model was established using ICR mice. NET-1601-treated C2C12 myotubes (50, 100, and 200 mg/mL) with H2O2-induced oxidative stress displayed significantly increased cell viability and ATP content, but significantly decreased levels of reactive oxygen species. All NET-1601-treated EST models demonstrated significantly higher maximum swimming rates than control mice. Furthermore, serum lactate, lactate dehydrogenase activity, non-esterified fatty acid, and intramuscular glycogen levels were higher in NET-1601-treated mice than in control mice. In addition, mRNA levels of regulatory factors involved in muscle mitochondrial fatty acid β-oxidation increased upon NET-1601 treatment. Moreover, catalase, superoxide dismutase, glutathione-S-transferase, and liver glutathione content, and antioxidant activity were higher in NET-1601-treated mice than in control mice. Reduced malondialdehyde levels indicated that NET-1601 treatment inhibited exercise-induced lipid peroxidation. Together, these results suggest that NET-1601 retains antioxidant enzyme activity during oxidative stress, simultaneously enhancing both muscle function via glycogen and fatty acid oxidation, thereby exerting a positive effect on recovery from fatigue.

A New Antagonist of Caenorhabditis elegans Glutamate-Activated Chloride Channels With Anthelmintic Activity.

Nematode parasitosis causes significant mortality and morbidity in humans and considerable losses in livestock and domestic animals. The acquisition of resistance to current anthelmintic drugs has prompted the search for new compounds for which the free-living nematode Caenorhabditis elegans has emerged as a valuable platform. We have previously synthetized a small library of oxygenated tricyclic compounds and determined that dibenzo[b,e]oxepin-11(6H)-one (doxepinone) inhibits C. elegans motility. Because doxepinone shows potential anthelmintic activity, we explored its behavioral effects and deciphered its target site and mechanism of action on C. elegans. Doxepinone reduces swimming rate, induces paralysis, and decreases the rate of pharyngeal pumping required for feeding, indicating a marked anthelmintic activity. To identify the main drug targets, we performed an in vivo screening of selected strains carrying mutations in Cys-loop receptors involved in worm locomotion for determining resistance to doxepinone effects. A mutant strain that lacks subunit genes of the invertebrate glutamate-gated chloride channels (GluCl), which are targets of the widely used antiparasitic ivermectin (IVM), is resistant to doxepinone effects. To unravel the molecular mechanism, we measured whole-cell currents from GluClα1/β receptors expressed in mammalian cells. Glutamate elicits macroscopic currents whereas no responses are elicited by doxepinone, indicating that it is not an agonist of GluCls. Preincubation of the cell with doxepinone produces a statistically significant decrease of the decay time constant and net charge of glutamate-elicited currents, indicating that it inhibits GluCls, which contrasts to IVM molecular actions. Thus, we identify doxepinone as an attractive scaffold with promising anthelmintic activity and propose the inhibition of GluCls as a potential anthelmintic mechanism of action.

Análise quantitativa temporal sobre os efeitos do uso de agrotóxicos em anfíbios – anuros

A presença de anfíbios em ambientes agrícolas alterados é notável, mas o desaparecimento de algumas espécies traz preocupação com o risco de aplicação de produtos químicos associados à agricultura nas populações de larvas e adultos. A avaliação quantitativa abrangente da sensibilidade comportamental dos anfíbios faz-se imprescindível para entender melhor o impacto populacional e os impactos ecológicos resultantes dos contaminantes. Com isso, o objetivo do estudo foi realizar uma revisão utilizando o método cienciométrico para avaliar os efeitos dos agrotóxicos na população de anuro. Os resultados indicaram que a maioria dos estudos foi realizada na Europa e na Ásia envolvendo estágios larvais e embrionários deste grupo sendo que, 46,33% dos 218 estudos se concentraram nos efeitos dos inseticidas. Em particular, os inseticidas aumentaram as taxas de natação anormal e reduziram as respostas de escape aos ataques de predadores. No entanto nos artigos analisados verificou-se que a falta de testes de campo e a dependência excessiva de testes de toxicidade direta em laboratório podem limitar a capacidade de interpretar os resultados sob condições realistas de campo.

Acceptability and perceptions of end-users towards an online sports-health surveillance system

AimTo describe the acceptability and the perceptions of athletes and staff members (ie, end-users) towards an online sports-health surveillance system.MethodsA pilot study with a mixed-methods approach was pursued. Descriptive analysis...

Modeling the metabolic costs of swimming in polar bears (Ursus maritimus)

Climate change is expected to increase the frequency and duration of long-distance swims by polar bears (Ursus maritimus). The energetic costs of such swims are assumed to be large, however, no estimates of metabolic costs of swimming for polar bears are available. Here, I use data on internal body temperature and external ambient temperature for two swimming polar bears, combined with mathematical modeling of heat production and of heat conduction to the surrounding water, to estimate the metabolic rate of swimming. Using this metabolic rate, I then examine the relative heat production and heat loss for bears of a range of sizes and body conditions. I calculated overall mean metabolic rate for a swimming bear to be 2.75 ml O2 g−1 h−1, which is generally higher than metabolic rates previously reported for walking polar bears. When compared at the same movement rate, the cost of transport for swimming was estimated to be approximately 5× that of walking. I further show that for small bears (less than approx. 145 cm body length or 90 kg) and bears in poor body condition, heat loss while swimming in cold Arctic waters should exceed heat production, and long swims should therefore not be thermodynamically sustainable. These results support previous claims that increasing frequency and duration of long-distance swims in polar bears is energetically stressful. Energetic and thermodynamic costs of long swims may be further exacerbated by recent declines in body condition that have been documented due to climate warming.

Competitive Swimming and Racial Disparities in Drowning.

This paper provides compelling evidence of an inverse relationship between competitive swimming rates and drowning rates using Centers for Disease Control and Prevention (CDC) data on fatal drowning rates and membership rates from USA Swimming, the governing organization of competitive swimming in the United States. Tobit and Poisson regression models are estimated using panel data by state from 1999-2007 separately for males, females, African Americans and whites. The strong inverse relationship between competitive swimming rates and unintentional deaths through fatal drowning is most pronounced among African Americans males.

Acute Toxicity Evaluation of Environmental Hormones Using Daphnia magna

Daphnia magna are common planktonic crustacean of the subclass Phyllopoda that can be found in lakes and ponds all over the Holarctic. They have been the subject of biological research since the 1700s because of their value as an experimental organism; this is due to their plentitude, easily observable organs, easy maintenance, and quick reproduction rate. As a result, they are a well-known reference organism to study aquatic environmental contamination. Using this species, three different environmental hormones, deltamethrin, bifenthrin, and glyphosate, were introduced to develop an environmental pollution research model. The standard method of determining physiological differences of Daphnia magna typically observes only its heartbeat. However, in this study, one more variable was added in order to more accurately reflect the physiological changes underwent by Daphnia magna when their environmental conditions were altered: their swimming rate. In the actual experiment, the Daphnia magna were exposed to a serial dilution solution of the environmental hormones in a contamination model and then had their heartbeat rate measured. The experiment was then repeated under the same conditions for estimating their change in swimming rate. In each pollution model technique, the data demonstrated a mathematical relation of heartbeat rate and swimming rate with polynomial functionality. The sensitivity along the dilution concentration was different between the % heartbeat change and % swimming rate change, which might mean that both parameters should be mutually complementary and carried out simultaneously, when any environmental hormone’s toxicity is required to be thoroughly studied. The dangers of environmental hormones should not be downplayed and a more effective method for checking acute toxicity should be useful.