The effect of fluid viscosity, habitat temperature, and body size on the flow disturbance of Euchaeta (original) (raw)
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Copepod escape behavior in non-turbulent and turbulent hydrodynamic regimes
Marine Ecology Progress Series, 2007
Copepods respond to velocity gradients in the ambient fluid generated by the movement of nearby predators. Escape behavior of several species in response to hydrodynamic stimuli has been analyzed under non-turbulent conditions; however, copepods normally experience a flowing or turbulent environment. Two neritic species (Paracalanus parvus and Temora turbinata) were exposed to a siphon-generated flow field under both non-turbulent and turbulent conditions. Deformation rates of 6.16 and 3.93 s-1 were required to elicit escape behavior in P. parvus and T. turbinata, respectively. Copepod jump distances in response to the siphon-generated flow field were > 6.8 mm and were not significantly different under non-turbulent and turbulent conditions.
Quantitative analysis of tethered and free-swimming copepodid flow fields
Journal of Experimental Biology, 2007
associated calculations differ for tethered versus freeswimming conditions. Consideration of the flow field of the free-swimming predatory copepodid shows the intensity of the biologically generated flow and the extent of the mechanoreceptive signal quantified in terms of shear strain rate. The area in the dorso-ventral view surrounded by the 0.5·s -1 contour of e xy , which is a likely threshold to induce an escape response, is 11 times the area of the exoskeletal form for the free-swimming case. Thus, mechanoreceptive predators will perceive a more spatially extended signal than the body size.
Copepod sensitivity to flow fields: detection by copepods of predatory ctenophores
Marine Ecology Progress Series, 2006
Copepods have the mechanoreceptive abilities to detect velocity gradients generated by approaching predators and the ability to respond to these predators within milliseconds. Ctenophores produce a low-velocity feeding current to entrain slow-swimming and non-motile prey. Since copepod species vary in their sensitivity to hydrodynamic disturbances, it is possible that species will differ in their ability to distinguish flow-generating ctenophores from the surrounding fluid. Predatorprey interactions were recorded between the ctenophore Mnemiopsis leidyi and 3 copepod species, Acartia tonsa, Paracalanus parvus and Temora turbinata. Although A. tonsa is more sensitive to hydrodynamic disturbances, T. turbinata was most successful in escaping the ctenophore predator. T. turbinata entered the inner lobe area (capture surfaces) of the ctenophore significantly less than either A. tonsa or P. parvus and were better able to escape both encounters and contacts with the inner lobes. These results suggest that sensitivity to velocity gradients may play only a minor role in determining escape success and an intermittent swimming pattern may increase susceptibility to capture by flow-generating predators.
Response of copepods to physical gradients associated with structure in the ocean
Limnology and Oceanography, 2005
We studied the response of the copepods Acartia tonsa and Temora longicornis to spatial gradients of flow velocity and fluid density to determine whether the presence of physical gradients initiated local search for resources or promoted aggregation. Two additional species of copepods, Candacia ethiopica and Labidocera madurae, were also exposed to velocity gradients. A plane jet flume apparatus facilitated the isolation of physical structures that mimic those found in the ocean and permitted high-resolution behavioral observations. All four species significantly increased the proportion of time in the gradient layer region relative to the total time in the observation window (proportional residence time) in response to the velocity-gradient layer. Behavioral changes, such as increased swimming speed and turn frequency, were consistent with area-restricted search behavior. T. longicornis also significantly increased proportional residence time in response to the density-gradient layer, but changes in swimming speed and turn frequency were not significantly different. A. tonsa and T. longicornis appeared to contact the density gradient and swim away or along the boundary. Hence, density gradients may act as a barrier to vertical movement and not as a positive cue for area-restricted search behavior. Velocity and density gradients play important, yet different, roles in defining patterns at fine-to-intermediate scales in zooplankton ecology.
The escape behavior of marine copepods in response to a quantifiable fluid mechanical disturbance
Journal of Plankton Research, 1997
The threshold shear values needed to elicit the escape reaction to a quantifiable fluid mechanical disturbance were compared between five free-swimming oceanic copepod species. The results indicate a significant difference in the threshold for different species of copepods and between different age groups within a single species. In general, animals captured from more energetic regimes required a higher threshold than those captured from more pacific locations. Labidocera madurae required the highest shear values with 51.5 s~' for 50% of the animals tested to elicit an escape reaction (5jo). Acartia tonsa and Euchaeta rimana, in contrast, were behaviorally the most sensitive requiring an 550 of only 1.5 and 4.
Advertisement and Concealment in the Plankton: What Makes a Copepod Hydrodynamically Conspicuous?
Invertebrate Biology, 1996
Euchaeta rimana, a pelagic marine copepod, roams a 3-dimensional environment and its antennular setal sensors are oriented to detect water-borne signals in 3 dimensions. When the copepod moves through water or moves water around itself, it creates a fluid disturbance distinct from the ambient fluid motion. As it swims and hovers, the copepod's laminar feeding current takes the unstable nature of small-scale turbulence, organizes it, and makes the local domain a familiar territory within which signals can be specified in time and space. The streamlines betray both the 3-dimensional spatial location (x, y, z) as well as the time (t) separating a signal caught in the feeding current and the copepod receptor-giving the copepod early warning of the approach of a prey, predator, or mate. The copepod reduces the complexity of its environment by fixing information from a turbulent field into a simpler, more defined laminar field. We quantitatively analysed small-scale fluid deformations created by copepods to document the strength of the signal. Physiological and behavioral tests confirm (a) that these disturbances are relevant signals transmitting information between zooplankters and (b) that hydrodynamically conspicuous structures, such as feeding currents, wakes, and vibrations, elicit specific responses from copepods. Since fluid mechanical signals do elicit responses, copepods shape their fluid motion to advertise or to conceal their hydrodynamic presence. When swimming, a copepod barely leaves a trace in the water; the animal generates its flow and advances into the area from which the water is taken, covering up its tracks with the velocity gradient it creates around itself. When escaping, it sheds conspicuous vortices. Prey caught in a flow field expose their location by hopping. These escape hops shed jet-like wakes detected by copepod mechanoreceptors. Copepods recognize the wakes and respond adaptively.
The fluid mechanics of copepod feeding in a turbulent flow: A theoretical approach
Progress in Oceanography, 1991
An important area of biodynamics research is the interaction between predator and prey in nature. Several scales are significant for interactions between predator and prey over the life cycle of each organism. A key factor is the encounter probability (group and individual). On the basis of physical considerations, the group encounter probability depends upon the respective patch sizes (on the order of 10s of kin) and their relative dispersion (or aggregation) rates in turbulent systems. The encounter probability at the individual level is affected by the relative motion of the predator and the prey and is controlled by the velocity spectrum. In addition, at the individual level, the striking distance of a predator will depend on motility and perception of the prey. Here we address the mechanics of copepod predation on phytoplankton and the coupling with the physics of turbulent fluid motions. Our aim is to review pertinent fluid dynamics, on scales of less than a few metres, to provide a flamework in which to consider the role of fluctuating fluid velocities on copepod feeding. 2. 3. 4.
Journal of Plankton Research, 1997
Many marine planktonic organisms create water currents to entrain and capture food items. Rheotactic prey entrained within these feeding currents often exibit escape reactions. If the direction of escape is away from the feeding current, the prey may successfully deter predation. If the escape is towards the center of the feeding current, the prey will be re-entrained towards its predator and remain at risk of predation. The direction of escape is dependent on (i) the ability of the prey to escape in a direction different than its pre-escape orientation and (ii) the orientation caused by the interaction of the prey's body with the moving fluid. In this study, the change in orientation of Acartia hudsonica nauplii as a result of entrainment within the feeding current of Euchaeta rimana, a planktonic predatory copepod, was examined, When escaping in still water, A.hudsonica nauplii were able to vary their pre-escape direction by only 10°. This allows only a limited ability to escape in a direction different than their pre-escape orientation. Analyses of the feeding current of E.rinuma show the flow speed to be most rapid in the central region with an exponential decrease in speed distally. In contrast, flow vorticity is minimal in the center of the feeding current and maximal at 1.75mm along the antennae. As a result, the degree of rotation of the prey towards the center of the feeding current shows a strong dependency on the prey's location within the feeding current. The feeding current of E.rinuma rotated the prey 14° when near the center of the flow field and up to 160° when located more distal in the feeding current Since the prey's escape abilities cannot compensate for the rotation due to the flow, this mechanism will maintain the escaping prey within the feeding current of their predator. Therefore, the feeding current facilitates predatory copepods in capturing prey by (i) increasing the amount of water which passes over their sensors and through their feeding appendages and (ii) controlling the spatial orientation of their prey prior to escape. C Oxford University Press 79 by guest on October 14, 2011 plankt.oxfordjournals.org Downloaded from
The European physical journal. E, Soft matter, 2018
Suspensions of small planktonic copepods represent a special category in the realm of active matter, as their size falls within the range of colloids, while their motion is so complex that it cannot be rationalized according to basic models of self-propelled particles. Indeed, the wide range of individual variability and swimming patterns resemble the behaviour of much larger animals. By analysing hundreds of three-dimensional trajectories of the planktonic copepod Clausocalanus furcatus, we investigate the possibility of detecting how the motion of this species is affected by different external conditions, such as the presence of food and the effect of gravity. While this goal is hardly achievable by direct inspection of single organism trajectories, we show that this is possible by focussing on simple average metrics commonly used to characterize colloidal suspensions, such as the mean square displacement and the dynamic correlation functions. We find that the presence of food lea...