Increase In Swimming Speed Research Articles

Gastrointestinal Blood Flow and Postprandial Metabolism in Swimming Sea BassDicentrarchus labrax

In trout and salmon, the metabolic costs of exercise and feeding are additive, which would suggest that gastrointestinal blood flow during exercise is maintained to preserve digestive and absorptive processes related to the specific dynamic action (SDA) of food. However, in most published studies, gastrointestinal blood flow drops during swimming, hypoxia, and general stress. To test whether gastrointestinal blood flow is spared during exercise after feeding, sea bass were instrumented with flow probes to measure cardiac output and celiacomesenteric blood flow while swimming in a respirometer before and after feeding. Swimming at 2 body lengths per second (bl s(-1)) increased metabolic rate considerably more than did feeding (208% vs. 32% increase, respectively, relative to resting), and a similar pattern was observed for cardiac output. In unfed fish, resting gastrointestinal blood flow was 13.8+/-0.5 mL min(-1) kg(-1). After feeding, resting gastrointestinal blood flow increased by 82% but then decreased progressively with increasing swimming speeds. At 2 bl s(-1), gastrointestinal blood flow in fed fish was not significantly different compared with that in unfed swimming fish, and, therefore, the data do not support the gastrointestinal sparing hypothesis. The magnitude of the SDA was maintained despite the decrease in gastrointestinal blood flow and the consequent reduction in oxygen supply to the gut. An estimate of maximal oxygen flow to the gastrointestinal tract after feeding yielded 2.6 mmol O(2) h(-1) kg(-1), but this amount is not able to cover the oxygen demand of 3.16 mmol O(2) h(-1) kg(-1). Therefore, the SDA must reflect metabolic processes in tissues other than those directly perfused by the celiacomesenteric artery.

Long-term cognitive dysfunction following experimental subarachnoid hemorrhage: New perspectives

Cognitive dysfunction is increasingly recognized as a significant long-term complication following subarachnoid hemorrhage (SAH), affecting up to 60% of survivors. We proposed to determine the incidence and explore potential mechanisms of cognitive dysfunction in a rat model. The effects of intracisternal blood, saline and sham injections were compared. At five weeks, Morris water maze escape latency (P=0.001) and swimming distance (P=0.001) were significantly different between groups, with increased latencies and distances recorded in the blood group in spite of increased swimming speed. The number of morphologically intact cortical (r=−0.75, P=0.0001) and hippocampal CA1 (r=−0.80, P<0.0001) neurons correlated with escape latency. In spite of only slight early reductions in proximal cerebral arterial diameters, pronounced and prolonged reductions in regional cerebral blood flow were observed in SAH rats, suggesting microvascular dysfunction. In concordance, cerebral microangiographic perfusion remained incomplete even after 2 weeks. 8-hydroxydeoxyguanosine immunohistochemistry also revealed microvascular as well as neuronal oxidative DNA damage. These results provide new insights into the pathogenesis of cognitive dysfunction in SAH. They reveal a surprisingly prolonged time course of diffuse cerebrovascular insufficiency, most likely due to reversible microvascular dysfunction. Similar to findings in experimental models of vascular dementia, the data indicate a potentially important role for prolonged cerebrovascular insufficiency, probably due to microvascular dysfunction, and selective cortical and subcortical neuronal loss in cognitive failure following SAH.

The effects of acute temperature change on swimming performance in bluegill sunfishLepomis macrochirus

Many fish change gait within their aerobically supported range of swimming speeds. The effects of acute temperature change on this type of locomotor behavior are poorly understood. Bluegill sunfish swim in the labriform mode at low speeds and switch to undulatory swimming as their swimming speed increases. Maximum aerobic swimming speed (U(max)), labriform-undulatory gait transition speed (U(trans)) and the relationships between fin beat frequency and speed were measured at 14, 18, 22, 26 and 30 degrees C in bluegill acclimated to 22 degrees C. At temperatures below the acclimation temperature (T(a)), U(max), U(trans) and the caudal and pectoral fin beat frequencies at these speeds were reduced relative to the acclimation level. At temperatures above T(a) there was no change in these variables relative to the acclimation level. Supplementation of oxygen levels at 30 degrees C had no effect on swimming performance. The mechanical power output of the abductor superficialis, a pectoral fin abductor muscle, was measured in vitro at the same temperatures used for the swimming experiments. At and below T(a), maximal power output was produced at a cycle frequency approximately matching the in vivo pectoral fin beat frequency. At temperatures above T(a) muscle power output and cycle frequency could be increased above the in vivo levels at U(trans). Our data suggest that the factors triggering the labriform-undulatory gait transition change with temperature. Muscle mechanical performance limited labriform swimming speed at T(a) and below, but other mechanical or energetic factors limited labriform swimming speed at temperatures above T(a).

Purple sweet potato color repairs d-galactose-induced spatial learning and memory impairment by regulating the expression of synaptic proteins

Purple sweet potato color (PSPC), a class of naturally occurring anthocyanins used to color food (E163), has been reported to possess a variety of biological activities, including anti-oxidant, anti-tumor, and anti-inflammatory. The effect of PSPC on the spatial learning and memory of mice treated with d-galactose (d-gal) was evaluated by the Morris water maze; d-gal-treated mice had decreased performance compared with mice in the vehicle and PSPC groups, while the PSPC+d-gal group showed significantly shortened escape latency to platform, increased swimming speed, more target quadrant search time and more platform crossings as compared with the d-gal group. Brain functions, such as memory formation and recovery of function after injury, depend on proper regulation of the expression levels of the pre- and post-synaptic proteins. We investigated the expression of four pre-synaptic proteins (growth-associated protein-43, synapsin-I, synaptophysin, and synaptotagmin) and two post-synaptic proteins (post-synaptic density protein-95 and Ca2+/calmodulin-dependent protein kinase II) in the hippocampus and cerebral cortex, respectively, in response to different treatments. Western blotting analysis showed that there were significant decreases in the expression of these representative synaptic proteins in the hippocampus and cerebral cortex of d-gal-treated mice. Interestingly, these decreased expression levels of synaptic proteins could be reversed by PSPC. The levels of expression of these representative synaptic proteins in mice treated with PSPC alone were not significantly different from those in untreated mice. The results of this study suggested that memory impairment and synaptic protein loss in d-gal-treated mice may be improved by treatment with PSPC.

Hypoxic avoidance behaviour in cod ( Gadus morhua L.): The effect of temperature and haemoglobin genotype

Hypoxia can influence fish growth, survival and on larger scales, population structure. These effects may be influenced by water temperature, and may vary intra-specifically with genotype. In Atlantic cod ( Gadus morhua L.), the two haemoglobin homozygotes ( Hb-I⁎11 and Hb-I⁎22) vary in oxygen affinity at different temperatures, which is thought to correspond to variation in hypoxia tolerance. We therefore tested if hypoxic avoidance behaviour in cod 1) depends on ambient temperature and 2) is modified by haemoglobin genotype. In a laminar flow choice box, we subjected juvenile cod to an initial phase of non-escapable hypoxia, and a subsequent recovery phase, where one habitat was kept at 20% O 2 saturation while the other was raised in steps to full saturation. The experiment was performed at 5 and 15 °C with Hb-I⁎11 and Hb-I⁎22 cod. Cod responded to inescapable hypoxia by reducing their overall swimming speed and then, at the initial levels of the recovery phase, avoiding the most hypoxic habitat, irrespective of temperature or genotype. Fish recovered quickly as O 2 levels increased, as evidenced by increased swimming speed and time spent in the most hypoxic habitat. The avoidance response depended strongly on temperature: the relative reduction in speed and avoidance of the most hypoxic habitat was more pronounced at 15 than at 5 °C. During the recovery phase, stressed fish initially maintained a higher swimming speed in the most hypoxic habitat. However, as O 2 increased, swimming speed in both habitats converged. This point of convergence occurred at a lower O 2 saturation at 5 °C. Fish ventilation rate in inescapable hypoxia was also higher at 15 °C. Haemoglobin genotype did not influence either ventilation rates or the nature of the hypoxic avoidance response at either temperature, but Hb-I⁎11 cod swam faster than Hb-I⁎22 cod in normoxia at 15 °C. Our results indicate that increased temperature limits the ability of cod of both haemoglobin genotypes to exploit hypoxic habitats. This may have negative future consequences for coastal cod stocks in light of increasing global temperatures and eutrophication in coastal waters.

Active migration of wild Atlantic salmon Salmo salar smolt through a coastal embayment

Migration patterns of wild Atlantic salmon Salmo salar smolt were examined in a coastal embayment in the Gaspe peninsula of Quebec, Canada. Twenty-four smolt in 2005 and 30 in 2006 were tagged with coded ultrasonic transmitters, and their migration throughout the bay was moni- tored using an array of fixed VR2 hydrophone receivers. Migration patterns were complex, with some smolt taking a direct route through the coastal embayment and others repeatedly changing direction over short spatial and temporal scales. Migration was mainly an active process with an overall outward (seaward) migration in the face of an inward residual circulation. Swimming direction was mainly outward during nocturnal inflowing currents but was more dispersed during daytime and nocturnal outflowing currents; swimming speed was greater during daytime than during nighttime. This pattern was consistent with smolt migrating offshore nocturnally and using daytime for prey detection and predator avoidance. Salinity had a strong effect: exposure to more saline waters caused increased swimming speeds. These observations are consistent with the hypothesis that smolt exploit an innate compass to maintain a preferred bearing and that the speed and direction of swimming is controlled by salinity and the diurnal cycle.

Speed-dependent intrinsic caudal fin muscle recruitment during steady swimming in bluegill sunfish,Lepomis macrochirus

There are approximately 50 muscles that control tail fin shape in most teleost fishes, and although myotomal muscle function has been extensively studied, little work has been done on the intrinsic musculature that controls and shapes the tail. In this study we measured electrical activity in intrinsic tail musculature to determine if these muscles are active during steady rectilinear locomotion, and to compare intrinsic muscle recruitment patterns to previous data on myotomal muscle fibers. Five bluegill sunfish (Lepomis macrochirus) were anaesthetized and electrode wires surgically placed into a total of 24 intrinsic caudal muscles, up to 13 at a time, and activity was correlated with synchronous recordings from myotomal fibers in the caudal peduncle. After recovery, fish swam steadily at speeds of 0.5, 1.2 and 2.0 L s(-1), while filmed from lateral, posterior and ventral views simultaneously at 250 frames s(-1). Comparison among speeds confirmed that muscle recruitment varies significantly with speed. At 0.5 L s(-1), the caudal fin was generally not used for propulsion, and swimming was accomplished primarily through body undulations. Intrinsic caudal muscle activity at this speed was intermittent and variable. At 1.2 and 2.0 L s(-1), the supracarinalis and infracarinalis muscles acted on the dorsal- and ventral-most fin rays, respectively, to expand the surface area of the caudal fin. The interradialis muscles adducted individual fin rays, dorsally to ventrally, following activation of the hypochordal longitudinalis. Contralateral muscle activity of interradialis muscles occurred as the caudal fin crossed the mean direction of travel and fin height was greatest, whereas ipsilateral activity of carinalis muscles occurred near points of maximum excursion of the fin, at speeds of 1.2 and 2.0 L s(-1), after fin height was lowest. Burst intensity increased with swimming speed, suggesting stiffening of the tail fin against imposed hydrodynamic loads. Activity patterns of intrinsic caudal muscles suggest that these most posterior muscles in fishes, located within the tail, are among the very first recruited as swimming speed increases, and that slow undulatory swimming is powered by muscle fibers located posteriorly in the caudal peduncle and tail.

Finding females: pheromone-guided reproductive tracking behavior by male Nereis succinea in the marine environment

Pheromones trigger reproductive responses of many marine organisms, but little is known about how pheromones mediate mate-finding behavior in the marine environment. This paper investigates whether the tetrapeptide nereithione (cysteine-glutathione disulfide), known to be released by females of the polychaete Nereis succinea to trigger spawning in male N. succinea, can also be used at lower concentrations to guide males to the females. Low concentrations of pheromone elicited increased swim speed and turning left or right 84% of the time. Animals sometimes weaved back and forth, or in other cases swam straight along the trails an average of 8.1+/-1.2 cm before veering off. At higher concentrations, the males circled frequently, often encountering 10-20 cm of pheromone trail before swimming away. Male responses to nereithione were modeled by computer simulation, taking into account arousal of swim speed, activation of turning, speed of response and its decay, etc. In the model, low concentrations (<10(-8) mol l(-1)) of pheromone significantly increased the number of encounters with the pheromone trail, an average following of simulated trails of 10.5+/-3.6 cm, and a significant increase in the frequency of encountering a virtual female on the trail (ANOVA, P<0.001). The model supports the hypothesis that a pheromone can have a dual function, with low concentration pheromone trails being used by male N. succinea to find females and increase their likelihood of mating whereas high concentrations of the same pheromone trigger the spawning behavior itself.

Sperm competition: linking form to function

BackgroundUsing information from physics, biomechanics and evolutionary biology, we explore the implications of physical constraints on sperm performance, and review empirical evidence for links between sperm length and sperm competition (where two or more males compete to fertilise a female's eggs). A common theme in the literature on sperm competition is that selection for increased sperm performance in polyandrous species will favour the evolution of longer, and therefore faster swimming, sperm. This argument is based on the common assumption that sperm swimming velocity is directly related to sperm length, due to the increased thrust produced by longer flagella.ResultsWe critically evaluate the evidence for links between sperm morphology and swimming speed, and draw on cross-disciplinary studies to show that the assumption that velocity is directly related to sperm length will rarely be satisfied in the microscopic world in which sperm operate.ConclusionWe show that increased sperm length is unlikely to be driven by selection for increased swimming speed, and that the relative lengths of a sperm's constituent parts, rather than their absolute lengths, are likely to be the target of selection. All else being equal, we suggest that a simple measure of the ratio of head to tail length should be used to assess the possible link between morphology and speed. However, this is most likely to be the case for external fertilizers in which females have relatively limited opportunity to influence a sperm's motility.

Integrated diversification of locomotion and feeding in labrid fishes

An organism's performance of any ecological task involves coordination of multiple functional systems. Feeding performance is influenced by locomotor abilities which are used during search and capture of prey, as well as cranial mechanics, which affect prey capture and processing. But, does this integration of functional systems manifest itself during evolution? We asked whether the locomotor and feeding systems evolved in association in one of the most prominent and diverse reef fish radiations, the Labridae. We examined features of the pectoral fins that affect swimming performance and aspects of the skull that describe force and motion of the jaws. We applied a recent phylogeny, calculated independent contrasts for 60 nodes and performed principal components analyses separately on contrasts for fin and skull traits. The major axes of fin and skull diversification are highly correlated; modifications of the skull to amplify the speed of jaw movements are correlated with changes in the pectoral fins that increase swimming speed, and increases in force capacity of the skull are associated with changes towards fins that produce high thrust at slow speeds. These results indicate that the labrid radiation involved a strong connection between locomotion and feeding abilities.

SPERM MOTILITY IN MYTILUS EDULIS IN RELATION TO MITOCHONDRIAL DNA POLYMORPHISMS: IMPLICATIONS FOR THE EVOLUTION OF DOUBLY UNIPARENTAL INHERITANCE IN BIVALVES

Bivalves of the families Mytilidae, Unionidae, and Veneridae have an unusual mode of mitochondrial DNA (mtDNA) transmission called doubly uniparental inheritance (DUI). A characteristic feature of DUI is the presence of two gender-associated mtDNA genomes that are transmitted through males (M-type mtDNA) and females (F-type mtDNA), respectively. Female mussels are predominantly homoplasmic with only the F-type expressed in both somatic and gonadal tissue; males are heteroplasmic with the M-type expressed in the gonad and F-type in somatic tissue for the most part. An unusual evolutionary feature of this system is that an mt genome with F-coding sequences occasionally invades the male route of inheritance (i.e., a "role reversal" event), and is thereafter transmitted as a new M-type. Phylogenetic studies have demonstrated that the new or "recently masculinized" M-types may eventually replace the older or "standard" M-types over time. To investigate whether this replacement process could be due to an advantage in sperm swimming behavior, we measured differences in motility parameters and found that sperm with the recently masculinized M-type had significantly faster curvilinear velocity and average path velocity when compared to sperm with standard M-type. This increase in sperm swimming speed could explain the multiple evolutionary replacements of standard M-types by masculinized M-types that have been hypothesized for the mytilid lineage. However, our observations do not support the hypothesis that DUI originated because it permits the evolution of mitochondrial adaptations specific to sperm performance, otherwise, the evolutionarily older, standard M genome should perform better.

Hitching a ride: the formation locomotion strategy of dolphin calves

Summary 1. Formation locomotion theoretically provides energy savings and it is evident across diverse taxa. Echelon position, described in cetacean (dolphin and whale) mother‐infant dyads as calf in very close proximity of its mother’s mid-lateral flank, may be a type of formation locomotion that provides hydrodynamic benefits for the calf. Until now, the difficulties associated with assessing the swimming energetics of marine mammals have precluded empirical quantifications of these benefits. 2. Through kinematic analyses, this study demonstrates empirically that 0‐1 month-old dolphin ( Tursiops truncatus ) calves in echelon position are afforded locomotor advantages as evident by increased swim performance with concurrent reductions in effort. 3. Compared to periods of independent swimming, calves in echelon position showed a 28% increase in average swim speed with reduced effort during stroke phases, as evident by a 22% reduction in fluke stroke amplitude and 19% increase in distance per stroke. 4. In addition, calves in echelon position spent over a third of their time gliding while no glide phases were observed for independently swimming calves. 5. The hydrodynamic benefits of echelon position enable cetacean calves, which have extremely limited locomotor performance, to maintain proximity of their mothers during travel, which is vital to infant survival. 6. This study adds to the limited empirical data regarding the energy economy of formation locomotion in animals.

The origin of evolutionary innovations: locomotor consequences of tail shape in aquatic snakes

1 Phylogenetic shifts in habitat use often impose strong selective forces on locomotor systems; for example, the transition from terrestrial to aquatic existence has stimulated the evolution of laterally compressed ‘paddles’ on the tails, feet or fins of a diverse array of vertebrate taxa. 2 Under the traditional gradualist model of evolutionary change, even a small paddle is predicted to enhance aquatic locomotion but impose a cost in terrestrial performance. However, direct evaluation of those early evolutionary stages is impossible from modern-day aquatic species, because the initial steps have been obscured by complex subsequent adaptations of morphology, physiology and behaviour. 3 Unlike most major features of locomotor-system morphology (e.g. leg length, muscle mass), the caudal paddles of aquatic snakes are morphologically so simple that they can be recreated experimentally. We attached artificial paddles to the tails of juvenile tigersnakes (Notechis scutatus) to assess the effect of tail shape on locomotor performances. 4 The presence of a small paddle on the tail greatly increased swimming speeds (by 25%) but decreased crawling speeds on land (by 17%). A small paddle (35% of tail length) was more effective for aquatic locomotion than a larger paddle (84% of tail length). 5 Presumably, larger paddles are effective only after adaptive modification of musculoskeletal propulsive systems. Our experimental manipulations thus provide unusually direct evidence of a functional advantage to modest lateral flattening of the tail in the earliest aquatic snakes, mediated via enhanced locomotor speeds in water.

Ontogeny of swimming speed in larvae of pelagic-spawning, tropical, marine fishes

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 349:255-267 (2007) - DOI: https://doi.org/10.3354/meps07107 Ontogeny of swimming speed in larvae of pelagic-spawning, tropical, marine fishes Jeffrey M. Leis1,3,*, Amanda C. Hay1, Matthew M. Lockett1, Jeng-Ping Chen2, Lee-Shing Fang2,4 1Ichthyology, Australian Museum, 6 College Street, Sydney, New South Wales 2010, Australia 2National Museum of Marine Biology and Aquarium, 2 Houwan Road, Checheng, Pingtung 944, Taiwan 3School of Biological Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia 4Present address: Department of Sport, Health and Leisure, Cheng Shiu University, 840 Chengcing Road, Niaosong hsiang, Kaohsiung County 83347, Taiwan *Email: jeff.leis@austmus.gov.au ABSTRACT: During the pelagic larval phase of teleost fishes, the larvae are subject to dispersal by currents. Dispersal trajectories can be substantially modified if the larvae have sufficient swimming abilities, so it is important to document how swimming ability develops during the pelagic larval phase. We used reared larvae (4 to 29 mm standard length) from commercial aquaculture farms in Taiwan to measure the development of swimming ability (critical speed, Ucrit) in larvae of 9 species (from 7 families) of Indo-Pacific coral reef and coastal fishes that hatch from pelagic eggs: Trachinotus blochii (Carangidae – jacks), Chanos chanos (Chanidae – milkfish), Platax teira (Ephippidae –batfishes), Leiognathus equulus (Leiognathidae – ponyfishes), Lutjanus malabaricus (Lutjanidae – snappers), Eleutheronema tetradactylum (Polynemidae – threadfins), and Epinephelus coioides, E. fuscoguttatus and E. malabaricus (Serranidae – groupers). Mean critical swimming speeds increased from <5 cm s–1 in the smallest larvae to a maximum of 47 cm s–1 in settlement stage larvae, with the increase in speed by the time of settlement ranging from 6- to 100-fold. Increase in swimming speed was more strongly correlated with size of larvae (R2 = 0.38 to 0.93, p < 0.005) than with age (correlation with age was absent in 3 species and explained 10 to 43% less variation than did size in the others). The relationship between speed and size was linear. In 6 species (T. blochii, C. chanos, L. malabaricus and the 3 Epinephelus species) speed increased at a rate of 2.1 to 2.6 cm s–1 for each 1 mm increase in size. Three species (P. teira, L. equulus and E. tetradactylum) had a significantly slower rate of increase of 1.3 to 1.7 cm s–1 for each 1 mm increase in size. On average, the best performers in each 1 mm size increment were 1.5 to 7.3 cm s–1 faster than mean performers, depending on species. Throughout development the vast majority of mean length-specific speeds were 10 to 20 body lengths (BL) s–1, and length-specific speed increased significantly with size in 6 species. Maximum length-specific speeds for each species reached 18 to 31 BL s–1. Although the ontogeny of swimming speed varies among species of tropical marine fishes, over similar size ranges, larvae that hatch from pelagic eggs have swimming abilities similar to those reported for larvae that hatch from demersal eggs. KEY WORDS: Marine fishes · Pelagic eggs · Pelagic larvae · Swimming speed · Ontogeny · Dispersal · Serranidae · Lutjanidae · Carangidae · Chanidae Full text in pdf format PreviousNextCite this article as: Leis JM, Hay AC, Lockett MM, Chen J, Fang L (2007) Ontogeny of swimming speed in larvae of pelagic-spawning, tropical, marine fishes. Mar Ecol Prog Ser 349:255-267. https://doi.org/10.3354/meps07107Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 349. Online publication date: November 08, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Paddlefish Polyodon spathula juveniles food searching behaviour evoked by natural food odour

Summary Using the behavioural bioassay, food search behaviour was investigated in paddlefish Polyodon spathula juveniles (2.3, 3.0, 5.0, 15.0 and 35.0 cm TL; and 16, 23, 35, 50 and 130 days post-hatch respectively) evoked by Daphnia water extracts. Main characteristics of this behaviour were increased swimming speed, sinking to the lower water layer, short and straight trajectories in the odour cloud and opening of the mouth. These responses were seldom clearly pronounced and had a fairly short time-pattern. Biting and snapping, common in food search by many other species, were never observed. Ability to respond to food odour developed at the beginning of exogenous feeding. Olfactory sensitivity of P. spathula to natural food extract was relatively low, 10 )1 –10 )2 gL )1 , 2–3 orders of magnitude lower than in some sturgeons. It was concluded that olfaction plays a minor role in the food search behaviour of paddlefish.

The prevalence and implications of copepod behavioral responses to oceanographic gradients and biological patchiness

Several species and developmental stages of calanoid copepods were tested for responses to environmental cues in a laboratory apparatus that mimicked conditions commonly associated with patches of food in the ocean. All species responded to the presence of phytoplankton by feeding. All species responded by increasing proportional residence time in one, but not both, of the treatments defined by gradients of velocity or density. Most species increased swimming speed and frequency of turning in response to the presence of chemical exudates or gradients of velocity. Only one species, Eurytemora affinis, increased proportional time of residence in response to gradients in density of the water. Responses of E. affinis to combined cues did not definitively demonstrate a hierarchical use of different cues as previously observed for Temora longicornis and Acartia tonsa. A simple foraging simulation was developed to assess the applicability in the field of the behavioral results observed in the laboratory. These simulations suggest that observed fine-scale behaviors could lead to copepod aggregations observed in situ. The present study demonstrates that behavioral response to cues associated with fine-scale oceanographic gradients and biological patchiness is functionally important and prevalent among copepods and likely has significant impacts on larger-scale distributional patterns.

Thermal effects on behavior of juvenile walleye pollock (Theragra chalcogramma): implications for energetics and food web models

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.

Feeding, fins and braking maneuvers: locomotion during prey capture in centrarchid fishes

Locomotion is an integral aspect of the prey capture strategy of almost every predatory animal. For fishes that employ suction to draw prey into their mouths, locomotor movements are vital for the correct positioning of the mouth relative to the prey item. Despite this, little is known regarding the relationships between locomotor movements and prey capture. To gain insights into how fishes move during prey capture and the mechanisms underlying deceleration during prey capture, I measured the fin and body movements of largemouth bass, Micropterus salmoides, and bluegill sunfish, Lepomis macrochirus. Using a high-speed video camera (500 frames s(-1)), I captured locomotor and feeding movements in lateral and ventral (via a mirror) view. Largemouth bass swam considerably faster than bluegill during the approach to the prey item, and both species decelerated substantially following prey capture. The mean magnitude of deceleration was significantly higher in largemouth bass (-1089 cm s(-2)) than bluegill (-235 cm s(-2)), and the timing of maximum deceleration was much later for largemouth bass (30.3 ms after maximum gape) than bluegill (6.7 ms after maximum gape). Both species employed their pectoral, anal and caudal fins in order to decelerate during prey capture. However, largemouth bass protracted their pectoral fins more and faster, likely contributing to the greater magnitude of deceleration in the species. The primary mechanism for increased deceleration was an increase in approach speed. The drag forces experienced by the fins and body are proportional to the velocity of the flow squared. Thus, the braking forces exerted by fins, without any change in kinematics, will increase exponentially with small increases in swimming speed, perhaps allowing these fishes to achieve higher braking forces at higher swimming speeds without altering body or fin kinematics. This result can likely be extended to other maneuvers such as turning.

Biomimetic evolutionary analysis: testing the adaptive value of vertebrate tail stiffness in autonomous swimming robots

For early vertebrates, a long-standing hypothesis is that vertebrae evolved as a locomotor adaptation, stiffening the body axis and enhancing swimming performance. While supported by biomechanical data, this hypothesis has not been tested using an evolutionary approach. We did so by extending biomimetic evolutionary analysis (BEA), which builds physical simulations of extinct systems, to include use of autonomous robots as proxies of early vertebrates competing in a forage navigation task. Modeled after free-swimming larvae of sea squirts (Chordata, Urochordata), three robotic tadpoles (;Tadros'), each with a propulsive tail bearing a biomimetic notochord of variable spring stiffness, k (N m(-1)), searched for, oriented to, and orbited in two dimensions around a light source. Within each of ten generations, we selected for increased swimming speed, U (m s(-1)) and decreased time to the light source, t (s), average distance from the source, R (m) and wobble maneuvering, W (rad s(-2)). In software simulation, we coded two quantitative trait loci (QTL) that determine k: bending modulus, E (Nm(-2)) and length, L (m). Both QTL were mutated during replication, independently assorted during meiosis and, as haploid gametes, entered into the gene pool in proportion to parental fitness. After random mating created three new diploid genotypes, we fabricated three new offspring tails. In the presence of both selection and chance events (mutation, genetic drift), the phenotypic means of this small population evolved. The classic hypothesis was supported in that k was positively correlated (r(2)=0.40) with navigational prowess, NP, the dimensionless ratio of U to the product of R, t and W. However, the plausible adaptive scenario, even in this simplified system, is more complex, since the remaining variance in NP was correlated with the residuals of R and U taken with respect to k, suggesting that changes in k alone are insufficient to explain the evolution of NP.

Influence of water temperature and fish length on the maximum swimming speed of sand flathead, Platycephalus bassensis: Implications for trawl selectivity

The maximum swimming speed of Australia's commercially important sand flathead ( Platycephalus bassensis) was assessed by video observation of fish swimming in a tank and measurement of muscle contraction time. Knowledge of the maximum swimming speed is important because it influences the ability or otherwise of fish to escape from various parts of the trawl. In our study fish were collected locally by angling and divided into three groups based on total length. Each group was tested at three water temperatures (10, 15 and 20 °C) to reflect typical changes in seasonal water temperature. Tank-held fish were first induced to swim in a raceway to measure tail beat frequency (in Hz) and distance swum per tail beat (stride length). The highest measured swimming speed was 336.6 cm −1 for a 24.1 cm fish at 20 °C. At this speed the recorded tail beat frequency was 17.9 Hz. The observed swimming speeds of each group of P. bassensis were linearly related with tail beat frequency, and a statistically significant ( P < 0.05) increase in stride length was detected with increased swimming speed. For all size groups, tail beat frequency increased with an increase in water temperature. The time taken for the anaerobic swimming muscle blocks dissected from newly euthanased P. bassensis to complete their contraction following an electric stimulus (5 V, 2 ms) was measured at each water temperature. Water temperature significantly ( P < 0.01) affected mean contraction times for all fish tested, but fish length did not affect contraction time ( P = 0.49). The mean pooled contraction times at each water temperature were 30.2 ms at 10 °C, 22.5 ms at 15 °C and 20.0 ms at 20 °C. For all size groups, the temperature effect on the muscle activity made tail beat frequency greater from 16.6 Hz at 10 °C to 25.0 Hz at 20 °C on average. We then used this data to calculate the maximum tail beat frequency and swimming speed of each group of fish at each water temperature. All estimated maximum swimming speeds were in excess of the typical trawl towing speed of 1.5 m s −1, and the implications of these results for seasonally varied towing strategies are discussed.