Size-specific swimming behavior of Daphnia pulex

Body length affects several aspects of the behavior of quietlyswimming Daphnia pulex Swimming and sinking rates were measuredat 0.033 s intervals during the ‘hops’ characteristicof Daphnia swimming behavior Larger animals swim faster, covermore distance, and produce more powerful swimming strokes. LargerDaphnia also sink faster, but the sinking rate scales as lengthto the 0 58 power, far lower than the power of 2 00 predictedby Stokes Law considerations. The number of hops s^–1 wasindependent of body size, although a theoretical analysis predictshopping rate (antennal beat frequency) should increase as bodylength squared. Turning behavior, measured as the ratio of displacementto total distance, during 5 s, is also independent of body sizeIndependence of several parameters of body motion and body sizeimplies that factors other than simple mechanics affect Daphniaswimming behavior     

水流对团头鲂(Megalobrama amblycephala)幼鱼游泳行为的影响

为探讨团头鲂幼鱼(Megalobrama amblycephala)游泳行为对水流的响应规律,该文通过特制鱼类游泳行为测定装置,测定了团头鲂幼鱼在25℃,0、0.1、0.2、0.3、0.4m/s流速条件下的游速、游距、转角、至中心点的距离及游泳轨迹。结果表明:随着流速的增大,个体游速、游距及转角值均相应增大。0、0.1及0.2m/s流速组间的游速、游距及转角差异均不显著(P>0.05),但显著小于0.3和0.4m/s组别,且0.3和0.4m/s流速组之间差异均不显著(P>0.05);整个时间段内,个体至中心点的距离随流速增大并未呈现明显规律性,各流速间差异不显著(P>0.05),游速与游距呈显著线性正相关,而与转角呈显著线性负相关,与至中心点的距离则无相关性;游泳轨迹随水流增大趋向复杂化。     

Seasonal changes in reproductive behavior in two ovariectomized female rhesus monkeys treated year-round with estradiol

Two ovariectomized female rhesus monkeys treated year-round with estradiol-filled capsules were used in hour-long behavioral tests with male rhesus monkeys both in and out of the normal breeding season. The study was designed primarily to test male hormonal responses to copulatory behavior and it was expected that behavior of the females would be essentially the same under both seasonal conditions. Several behaviors of the female, however, were found to fluctuate on a seasonal basis, namely (1) proximity to the male, (2) grooming of the male, (3) sexual presentations, and (4) threatening away (a form of sexual invitation). All of these behaviors, except proximity, were found to be positively correlated with the male partner's testosterone levels before and after the behavior test in the only test condition in which most males ejaculated. The preliminary suggestion is made that these females responded to some cue, either from the environment or from the males, that caused a change in their behavior between breeding and nonbreeding seasons despite the constant hormonal environment provided by the estradiol capsules. Since the same behaviors which were sensitive to seasonal effects were positively correlated with male testosterone levels, it is possible that the male's hormonal status affects affects female behavior.     

Seasonal dynamics of agonistic behavior and hormones in an ex situ all‐male colony of large flying foxes

Large flying foxes (Pteropus vampyrus) are a socially complex species. In situ colonies typically comprise thousands of individuals in small harems of one male to many females. In ex situ environments, all‐male colonies are becoming more common due to a surplus of males in the population. There is limited information describing the hormonal and behavioral patterns of all‐male colonies during the breeding season. We assessed seasonal changes in hormones and behavior in an all‐male colony of 12 large flying foxes at Disney's Animal Kingdom^®. We validated hormone assays using morning urine and fecal samples to assess seasonal changes in excreted immunoreactive testosterone and glucocorticoid metabolites. We collected behavior data using an all‐occurrence method, recording agonistic behaviors related to territorial defense (hooking, biting, wing flexing, vocalizing, and wrestling), and sexual behavior (mounting and frontal grabbing). Results indicated that (i) we could reliably measure testosterone and glucocorticoid metabolites concentrations from fecal and urine samples collected from individual bats; (ii) there were distinct relationships between changes in levels of agonism and hormone concentrations throughout the year; and (iii) three agonistic behaviors (chasing, wrestling, and open‐mouth threat) peaked prior to the increase in testosterone and glucocorticoid hormones measured during the breeding season. These three behaviors could potentially be used as early indicators to signal the onset of the breeding season and allow time to implement ex situ management changes to reduce the incidence of agonism between individuals.     

Changes in the swimming behavior of Pseudodiaptomus annandalei (Copepoda,Calanoida) adults exposed to the diatom toxin 2-trans, 4-trans decadienal

Diatoms are broadly present in marine habitats and often dominate seasonal phytoplankton blooms in polar and temperate latitudes. Certain species produce polyunsaturated aldehydes upon mechanical wounding caused by mesozooplankton grazing. Ample evidence is available on toxin-induced reproductive failure in copepods, yet their behavioral effects remain unclear. Here we present results of laboratory experiments in which we investigated the immediate effects of the diatom-derived aldehyde 2-trans, 4-trans decadienal on the three-dimensional swimming behavior of the calanoid copepod Pseudodiaptomus annandalei. Short-term direct exposure to the toxin at 3 μM, 6 μM and 12 μM induced hyperactivity in the three adult states, as evidenced by a marked and dose-dependent increase in the number of trajectories. It also caused a higher proportion of vertical movements. In males and ovigerous females exposed to decadienal at 3 μM and 6 μM, hyperactivity came with an equally specific dose-dependent decrease in swimming speed. Males and ovigerous females swam faster at 12 μM than at 6 μM, suggesting a complex mode of action of the toxin. In non-ovigerous females, decadienal had little effects on swimming speed, supporting the assumption that female copepods are less affected by certain environmental stressors. Multifractal analysis revealed differences in the statistical properties of the swimming behavior between experimental conditions. The moment structure function of the displacement appeared to be moderately multifractal in the three adult states swimming in control water. Ethanol as carrier solvent at 200 ppm caused an increase in swimming speed and a switch toward a more ballistic motion in males and ovigerous females. On the opposite, exposure to the toxin reduced or cancelled the effects of ethanol and resulted in a more Brownian motion for high moment values. Decadienal had little effects on the behavior of non-ovigerous females except at the highest concentration. Our results demonstrate that decadienal, a model diatom aldehyde, impairs the behavior of adult copepods. They provide further information on the interaction between diatoms and their main predator.     

Seasonal occurrence of silica-scaled chrysophytes under eutrophic conditions

The seasonal occurrence of silica-scaled chrysophytes (Paraphysomonadaceae and Mallomonadaceae) in the eutrophic lake Tystrup Sø, was examined during 1979–1981 in relation to temperature and to overall phytoplankton biomass and composition. The 33 species recorded represent three seasonality types, with occurrence in spring alone, spring and autumn, and during a greater or lesser part of the whole year, including summer. The great majority of the species have their main occurrence in early spring and at low temperatures, perhaps due to effects of the high phytoplankton biomass, especially cyanophytes, during summer and autumn.     

Seasonal variation of behavior and brain size in a freshwater fish

1. Teleost fishes occupy a range of ecosystem, and habitat types subject to large seasonal fluctuations. Temperate fishes, in particular, survive large seasonal shifts in temperature, light availability, and access to certain habitats. Mobile species such as lake trout (Salvelinus namaycush) can behaviorally respond to seasonal variation by shifting their habitat deeper and further offshore in response to warmer surface water temperatures during the summer. During cooler seasons, the use of more structurally complex nearshore zones by lake trout could increase cognitive demands and potentially result in a larger relative brain size during those periods. Yet, there is limited understanding of how such behavioral responses to a seasonally shifting environment might shape, or be shaped by, the nervous system.
2. Here, we quantified variation in relative brain size and the size of five externally visible brain regions in lake trout, across six consecutive seasons in two different lakes. Acoustic telemetry data from one of our study lakes were collected during the study period from a different subset of individuals and used to infer relationships between brain size and seasonal behaviors (habitat use and movement rate).
3. Our results indicated that lake trout relative brain size was larger in the fall and winter compared with the spring and summer in both lakes. Larger brains coincided with increased use of nearshore habitats and increased horizontal movement rates in the fall and winter based on acoustic telemetry. The telencephalon followed the same pattern as whole brain size, while the other brain regions (cerebellum, optic tectum, olfactory bulbs, and hypothalamus) were only smaller in the spring.
4. These findings provide evidence that flexibility in brain size could underpin shifts in behavior, which could potentially subserve functions associated with differential habitat use during cold and warm seasons and allow fish to succeed in seasonally variable environments.

     

The swimming and feeding behavior of Mesocyclops

The swimming and feeding behaviors of Mesocyclops are described from a review of the literature and personal observations. Mesocyclops exhibits considerable behavioral flexibility in response to environmental stimuli. Mesocyclops edax exhibits an increase in horizontal looping behavior at high prey densities, and performs a tight vertical looping behavior in response to the loss of captured prey. Ingestion rates by Mesocyclops are a complex function of prey density, morphology, and behavior in addition to prey size. Vertebrate predators induce a rapid escape response in Mesocyclops and may be responsible at least in part for their extensive diel vertical migrations. The complex behavioral patterns of Mesocyclops suggest that its distribution and abundance in nature will be distinctly nonrandom and influenced as much by its own behavioral responses as by other external physical factors such as water circulation patterns.     

Computational methods for the analysis of swimming biomechanics

A series of computer programs is presented which enables the analysis of fish body shape and mass distributions, spine positions, spine curvatures and coordinates for the centre of mass. Data are derived from silhouette outlines of swimming fish, white muscle strains during swimming, white muscle force-time development functions for body bending cycles, muscle force and power production along the whole fish body and hydrodynamic efficiencies for fast-start swimming behaviours.     

High-speed video observation of swimming behavior and flagellar motility ofProrocentrum minimum (Dinophyceae)

Summary To understand the functions of the longitudinal and transverse flagella of dinoflagellates, the flagellar waveform and frequency of each flagellum were observed by high-speed video-recording. The longitudinal flagellum emerged from the anterior end of the cell and beat with a planar undulating wave whose plane was perpendicular to the valval sutural plane. The transverse flagellum curved around the anterior end of the cell and beat with a helical wave, with different alternating half pitches. The half pitch corresponding to the parts farther from the cellular antero-posterior axis was shorter than that of the parts closer to the axis. This pattern is described by the ratio of the outer-parts half pitch to the pitch of the whole period of the helix and seems to be characteristic of the dinoflagellates' transverse flagellum.Abbreviations p _in half pitch corresponding to the inner parts of the transverse flagellum - p _out half pitch corresponding to the outer parts of the transverse flagellum - P _p pitch of helical swimming trajectory - R _p radius of helical swimming trajectory - _c rotational frequency of the cell     

Hydrodynamic analysis of human swimming based on VOF method

A 3-D numerical model, based on the Navier-Strokes equations and the RNG k-ε turbulence closure, for studying hydrodynamic drag on a swimmer with wave-making resistance taken into account is established. The volume of fluid method is employed to capture the undulation of the free surface. The simulation strategy is evaluated by comparison of the computed results with experimental data. The computed results are in good agreement with data from mannequin towing experiments. The effects of the swimmer’s head position and gliding depth on the drag force at different velocities are then investigated. It is found that keeping the head aligned with the body is the optimal posture in streamlined gliding. Also wave-making resistance is significant within 0.3 m depth from the free surface.     

Evolutionary change in metabolic rate of Daphnia pulicaria following invasion by the predator Bythotrephes longimanus

Metabolic rate is a trait that may evolve in response to the direct and indirect effects of predator‐induced mortality. Predators may indirectly alter selection by lowering prey densities and increasing resource availability or by intensifying resource limitation through changes in prey behavior (e.g., use of less productive areas). In the current study, we quantify the evolution of metabolic rate in the zooplankton Daphnia pulicaria following an invasive event by the predator Bythotrephes longimanus in Lake Mendota, Wisconsin, US. This invasion has been shown to dramatically impact D. pulicaria, causing a ~60% decline in their biomass. Using a resurrection ecology approach, we compared the metabolic rate of D. pulicaria clones originating prior to the Bythotrephes invasion with that of clones having evolved in the presence of Bythotrephes. We observed a 7.4% reduction in metabolic rate among post‐invasive clones compared to pre‐invasive clones and discuss the potential roles of direct and indirect selection in driving this change.     

Seasonal variation in positional behavior of malagasy lemurs

I describe the positional behavior of four species of Malagasy lemur (Propithecus diadema, Eulemur fulvus rufus, Eulemur rubriventer,and Varecia variegata)at two times of year at Ranomafana National Park,Madagascar. There were significant seasonal differences in locomotor behavior in all species except P. diademaAmong the lemurids, leaping was more frequent and quadrupedism less frequent in the dry season. Only E. rubriventerexhibited seasonal differences in posture, and there were few seasonal differences in support use. The observed differences in positional behavior were not the result of differences in activity budget or in microhabitat use attributable to seasonal variation in resource use.     

Genetic Diversity,Heteroplasmy, and Recombination in Mitochondrial Genomes of Daphnia pulex,Daphnia pulicaria,and Daphnia obtusa

Genetic variants of mitochondrial DNA at the individual (heteroplasmy) and population (polymorphism) levels provide insight into their roles in multiple cellular and evolutionary processes. However, owing to the paucity of genome-wide data at the within-individual and population levels, the broad patterns of these two forms of variation remain poorly understood. Here, we analyze 1,804 complete mitochondrial genome sequences from Daphnia pulex, Daphnia pulicaria, and Daphnia obtusa. Extensive heteroplasmy is observed in D. obtusa, where the high level of intraclonal divergence must have resulted from a biparental-inheritance event, and recombination in the mitochondrial genome is apparent, although perhaps not widespread. Global samples of D. pulex reveal remarkably low mitochondrial effective population sizes, <3% of those for the nuclear genome. In addition, levels of population diversity in mitochondrial and nuclear genomes are uncorrelated across populations, suggesting an idiosyncratic evolutionary history of mitochondria in D. pulex. These population-genetic features appear to be a consequence of background selection associated with highly deleterious mutations arising in the strongly linked mitochondrial genome, which is consistent with polymorphism and divergence data suggesting a predominance of strong purifying selection. Nonetheless, the fixation of mildly deleterious mutations in the mitochondrial genome also appears to be driving positive selection on genes encoded in the nuclear genome whose products are deployed in the mitochondrion.     

Cryptic intercontinental colonization in water fleas Daphnia pulicaria inferred from phylogenetic analysis of mitochondrial DNA variation

The water fleas of the Daphnia pulex complex play a key role in freshwater ecosystems throughout the northern hemisphere. Despite the fact that they have been the subject of study for numerous biological disciplines, their phylogeny and species delimitation remain controversial. We used DNA sequence variation of the mitochondrial ND5 gene to reconstruct the phylogenetic relationships of D. pulicaria Forbes, a widespread member of this complex from North America and Europe. Populations from the two continents respectively split into two evolutionary lineages, Eastern Nearctic and European, which each belong to another main clade within the D. pulex complex (the pulicaria and tenebrosa groups, respectively). Unexpectedly, melanin and carotenoid pigmented D. pulicaria populations from European high-mountain lakes were not allied with the transparent populations inhabiting the same lakes and the lowland ponds and reservoirs throughout Europe, but were included with the samples from Canada and Greenland in the Eastern Nearctic lineage. Until now populations belonging to this lineage were known only from Canada and North Atlantic islands, but not from mainland Europe. Independent data from microsatellite markers supported the genetic distinctiveness of the sympatric carotenoid pigmented and transparent populations and suggested that they may have undergone transition to obligate parthenogenesis, possibly as a consequence of past introgressive hybridization. Two different taxa are therefore confused under the name D. pulicaria in Europe. The close phylogenetic relationships of European populations with those from Canada and Greenland suggest that the Nearctic lineage is of recent origin in Europe via intercontinental dispersal from the North America. It has evolved melanin and carotenoid pigmentation as adaptations against the UV light stress, which enable it to share habitat occupied by the transparent European species. The Nearctic D. pulicaria thus provides a new model for studying successful intercontinental invasion. In general, our study demonstrates that a considerable part of the diversity among widespread taxa of cladoceran crustaceans has been overlooked in morphological taxonomies.     

Seasonal influences on rhesus monkey (Macaca mulatta) behavior

Seasonal differences in the behavior of 2.5- to 4.5-year-old female subjects and male subjects >2.5 years of age were studied in two rhesus monkey groups over a period of 6 years. The frequencies and durations of sexual acts and states were higher during the Fall in Georgia, USA, but were significant only with regard to female partners. Total time in social proximity, scores for proximity by partner without social interaction, nonspecific contact, grooming received, and noncontact forms of aggression with female partners were also higher in the Fall. Although more submission and agonistically ambiguous responses were received from female partners during the Fall, no seasonal pattern prevailed for responses performed. More contact aggression was directed to males in the Spring, and the pattern of agonistic behavior observed cannot be accounted for by males fighting over estrous females. Significantly more play was observed among subjects in the Fall, but the oldest males played more in the Spring. Some patterns, like huddling, were seen more in the Fall, but they may have been due to temperature differences. Seasonal differences in morphology and behavior cannot be attributed to a single variable, like temperature, level of gonadal hormones, or sexual competition, and may reflect a broader adaptation to seasonal variables.     

Seasonal swimming behaviour in the queen scallop (Aequipecten opercularis) and its effect on dredge fisheries

Modified dredges were used on Aequipecten opercularis (queen scallop) fishing grounds off the Isle of Man in the north Irish Sea to determine seasonal variability in swimming behaviour in queen scallops and its effect on dredge fisheries. Scallops, which evaded dredge capture by swimming up into the water column, were captured by a specially designed net deployed above the dredge gear. The gear was used over a 20-month period and the number and size distribution of queen scallops captured in both the net and dredges were recorded. A subsample of captured scallops was maintained in running seawater tanks and used to assess two components of swimming behaviour, the time taken to respond to stimuli and the number of valve adductions carried out until exhaustion. There was considerable seasonal variability in the proportion of queen scallops that avoided dredge capture by swimming. Very low numbers of queen scallops were found in the net during the winter and spring. Net capture increased in June, and was high throughout the summer and autumn when up to 42% of scallops greater than 55 mm in height, captured in dredges, swam over the dredge mouths. There was a strong positive correlation between seawater temperature and proportion of captured scallops found in the net. Swimming experiments in the laboratory indicated that the observed seasonal variability in net capture was probably a result of changes in the time taken to respond to stimuli, rather than changes in the ability to perform a large number of valve adductions. There was no relationship between reproductive state and the proportion of actively swimming scallops. Analyses of size distributions indicated limited swimming activity in the largest scallops but no effect of epifaunal load was found on the ability of scallops to avoid dredge capture.     

The swimming performance of brown trout and whitefish: the effects of exercise on Ca2 + handling and oxidative capacity of swimming muscles

The swimming performance of two fish species, the brown trout and whitefish, having initially different swimming strategies, was measured after nine different training programs in order to relate the effects of exercise on Ca²⁺ handling and oxidative capacity of swimming muscles. The time to 50% fatigue was measured during the training period, and compared with the density of dihydropyridine (DHP) and ryanodine (Ry) receptors and succinate dehydrogenase (SDH) and phosphorylase activity determined by histochemical analysis of the swimming muscles. Overall, both trained brown trout and whitefish had superior swimming performance as compared to control ones. Interestingly, the training programs had different effect on the two species studied since brown trout achieved the highest swimming performance, swimming against the water flow velocity of 2 BL s⁻¹ while among whitefish the best efficiency was seen after training with lower swimming velocities. Training also induced a significant increase in DHP and Ry receptor density in both species. Generally, in brown trout the most notable increase in the receptor densities was observed in red muscle sections from the fish swimming for 6 weeks against water currents of 1 BL s⁻¹ (DHPR 176.5 ± 7.7% and RyR 231.4 ± 11.8%) and white muscle sections against 2 BL s⁻¹ (DHPR 129.6 ± 12.4% and RyR 161.9 ± 15.5%). In whitefish the most prominent alterations were noted in samples from both muscle types after 6 weeks of training against water current of 1.5 BL s⁻¹ (DHPR 167.1 ± 16.9% and RyR 190.4 ± 19.4%). Finally, after all the training regimens the activity of SDH increased but the phosphorylase activity decreased significantly in both the species. To conclude, our findings demonstrate an improved swimming performance and enhanced Ca²⁺ regulation and oxidative capacity after training. Moreover, there seems to be a connection between the swimming performance and receptor levels, especially in white swimming muscles of different fish species, regardless of their initially deviant swimming behaviours. However, depending on the training regimen the divergent swimming behaviours do cause a different response, resulting in the most prominent adaptational changes in the receptor levels of red muscle samples with lower swimming velocities in brown trout and with higher ones in whitefish.     

Hydrodynamic Characteristics of Daphnia middendorffiana

Sinking terminal velocities of D. middendorffiana (with and without tail spine) were measured and correlated with morphological parameters and water temperature. The main dimensions of the body showed positive growths rate correlations with the body weight. In turn, negative allometric variation was observed in the tail-spine length. The density of D. middendorffiana was age specific, and decreased as the individual grew. No differences in the sinking terminal velocities and trajectories between individuals with and without tail spine were observed. The observed hydrodynamic characteristics of D. middendorffiana were simulated by means of a model based on equivalent ellipsoids and spheres. The analysis showed that the effects of shape and the body projections are negligible on the sinking rates of D. middendorffiana.     

Swimming behavior of the spoon worm Urechis unicinctus (Annelida,Echiura)

Large numbers of swimming and stranding Urechis unicinctus were observed at night during low tide in Sasuhama, Miyagi Prefecture, northeastern Japan, during the periods from January to February in 2012 and 2013. Worms did not drift passively but swam actively, therefore hinting at a certain purpose for such behavior. As trochophore larvae of U. unicinctus were observed to occur simultaneously in the plankton, we infer the possibility that this is an event of reproductive swarming. Anatomical observations of both swimming and stranding U. unicinctus showed that none of the specimens had gametes, which may suggest that these were completely spent after spawning. Urechis unicinctus seemed to begin swimming after dusk and the observed swimming behavior occurred during the evening ebb tide throughout the night low tide during winter time. Stranding U. unicinctus have long been known in Japan and have been attributed to sea storms. The present study shows for the first time the possibility that U. unicinctus swims in order to reproduce at night and that this swimming behavior is closely linked to the stranding of U. unicinctus individuals.