Turbulence: Does Vorticity Affect the Structure and Shape of Body and Fin Propulsors?

SUMMARY Jumping is a common form of locomotion for many arboreal animals. Many species of the arboreal lizard genus Anolis occupy habitats in which they must jump to and from unsteady perches, e.g. narrow branches, vines, grass and leaves. Anoles therefore often use compliant perches that could alter jump performance. In this study we conducted a small survey of the compliance of perches used by the arboreal green anole Anolis carolinensis in the wild (N=54 perches) and then, using perches within the range of compliances used by this species, investigated how perch compliance (flexibility) affects the key jumping variables jump distance, takeoff duration, takeoff angle, takeoff speed and landing angle in A. carolinensis in the laboratory (N=11). We observed that lizards lost contact with compliant horizontal perches prior to perch recoil, and increased perch compliance resulted in decreased jump distance and takeoff speed, likely because of the loss of kinetic energy to the flexion of the perch. However, the most striking effect of perch compliance was an unexpected one; perch recoil following takeoff resulted in the lizards being struck on the tail by the perch, even on the narrowest perches. This interaction between the perch and the tail significantly altered body positioning during flight and landing. These results suggest that although the use of compliant perches in the wild is common for this species, jumping from these perches is potentially costly and may affect survival and behavior, particularly in the largest individuals.

Section: Discussionmentioning

confidence: 99%

Total recoil: perch compliance alters jumping performance and kinematics in green anole lizards (Anolis carolinensis)

Gilman

Gillis

Irschick

2012

“…Similarly, several groups have found increased fish abundance in areas of streams with high turbulence intensity (Smith et al, 2005;Van Zyll De Jong et al, 1997). Horizontal cylinders, in contrast, destabilize several species of fishes (Eidietis et al, 2002;Webb, 1998;Webb and Cotel, 2010). Finally, other studies have found that generalized turbulence has negative impacts on energetic demands of some fish species (Enders et al, 2003;Lupandin, 2005;Roche et al, 2014;Tritico and Cotel, 2010).…”

Section: Introductionmentioning

confidence: 95%

“…Finally, other studies have found that generalized turbulence has negative impacts on energetic demands of some fish species (Enders et al, 2003;Lupandin, 2005;Roche et al, 2014;Tritico and Cotel, 2010). Small turbulent eddies may also interfere with sensory receptors (Webb and Cotel, 2010). Lacey et al (2012) suggested that some of the diversity in the results could be organized by considering the intensity, periodicity, orientation and size of vortices in a wake, which they termed the 'IPOS' (intensity, periodicity, orientation and size) framework.…”

Section: Introductionmentioning

confidence: 99%

Streamwise vortices destabilize swimming bluegill sunfish (Lepomis macrochirus)

Maia

Sheltzer

Tytell

2015

In their natural environment, fish must swim stably through unsteady flows and vortices, including vertical vortices, typically shed by posts in a flow, horizontal cross-flow vortices, often produced by a step or a waterfall in a stream, and streamwise vortices, where the axis of rotation is aligned with the direction of the flow. Streamwise vortices are commonly shed by bluff bodies in streams and by ships' propellers and axial turbines, but we know little about their effects on fish. Here, we describe how bluegill sunfish use more energy and are destabilized more often in flow with strong streamwise vorticity. The vortices were created inside a sealed flow tank by an array of four turbines with similar diameter to the experimental fish. We measured oxygen consumption for seven sunfish swimming at 1.5 body lengths (BL) s −1 with the turbines rotating at 2 Hz and with the turbines off (control). Simultaneously, we filmed the fish ventrally and recorded the fraction of time spent maneuvering side-to-side and accelerating forward. Separately, we also recorded lateral and ventral video for a combination of swimming speeds (0.5, 1.5 and 2.5 BL s −1 ) and turbine speeds (0, 1, 2 and 3 Hz), immediately after turning the turbines on and 10 min later to test for accommodation. Bluegill sunfish are negatively affected by streamwise vorticity. Spills (loss of heading), maneuvers and accelerations were more frequent when the turbines were on than in the control treatment. These unsteady behaviors, particularly acceleration, correlated with an increase in oxygen consumption in the vortex flow. Bluegill sunfish are generally fast to recover from roll perturbations and do so by moving their pectoral fins. The frequency of spills decreased after the turbines had run for 10 min, but was still markedly higher than in the control, showing that fish partially adapt to streamwise vorticity, but not completely. Coping with streamwise vorticity may be an important energetic cost for stream fishes or migratory fishes.

“…Those that most effectively do so can allocate a greater proportion of available resources (time and energy) to other activities, such as the detection and evasion of predators, growth and reproduction (Parker and Maynard Smith, 1990). For streamdwelling fish adapted to the challenges imposed by a spatially and temporally complex hydrodynamic environment, energetic costs include those associated with maintaining stability (Tritico and Cotel, 2010;Webb and Cotel, 2010), swimming (Enders et al, 2003;Liao, 2004) and capturing food (Chesney, 1989). The use of space that enables fish to minimise energy expenditure under complex flows is of interest to evolutionary biologists, ecologists, fisheries managers and conservationists, and is the focus of this study.…”

Section: Introductionmentioning

confidence: 99%

Assessing hydrodynamic space use of brown trout, Salmo trutta, in a complex flow environment: a return to first principles.

Kerr

Manes

Kemp

2016

It is commonly assumed that stream-dwelling fish should select positions where they can reduce energetic costs relative to benefits gained and enhance fitness. However, the selection of appropriate hydrodynamic metrics that predict space use is the subject of recent debate and a cause of controversy. This is for three reasons: (1) flow characteristics are often oversimplified, (2) confounding variables are not always controlled and (3) there is limited understanding of the explanatory mechanisms that underpin the biophysical interactions between fish and their hydrodynamic environment. This study investigated the space use of brown trout, Salmo trutta, in a complex hydrodynamic flow field created using an array of different sized vertically oriented cylinders in a large open-channel flume in which confounding variables were controlled. A hydrodynamic drag function (D) based on single-point time-averaged velocity statistics that incorporates the influence of turbulent fluctuations was used to infer the energetic cost of steady swimming. Novel hydrodynamic preference curves were developed and used to assess the appropriateness of D as a descriptor of space use compared with other commonly used metrics. Zones in which performanceenhancing swimming behaviours (e.g. Kaŕmań gaiting, entraining and bow riding) that enable fish to hold position while reducing energetic costs (termed 'specialised behaviours') were identified and occupancy was recorded. We demonstrate that energy conservation strategies play a key role in space use in an energetically taxing environment with the majority of trout groups choosing to frequently occupy areas in which specialised behaviours may be adopted or by selecting low-drag regions.