Copepod escape behavior in non-turbulent and turbulent hydrodynamic regimes (original) (raw)
Related papers
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.
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.
Swim and fly. Escape strategy in neustonic and planktonic copepods
The Journal of experimental biology, 2017
Copepods may respond to predators by powerful escape jumps that in some surface dwelling forms may propel the copepod out of the water. We studied the kinematics and energetics of submerged and out-of-water jumps of two neustonic pontellid Anomalocera patersoni and Pontella mediterranea and one pelagic calanoid copepod Calanus helgolandicus (euxinus). We show that jumping out of the water does not happen just by inertia gained during the copepod's acceleration underwater, but also requires the force generated by the thoracic limbs when breaking through the water's surface to overcome surface tension, drag, and gravity. Such timing appears necessary for success. At the moment of breaking the water interface the instantaneous velocity of the two pontellids reaches 125 cm s-1, while their maximum underwater speed (115 cm s-1) is close to that of similarly sized C. helgolandicus (106 cm s-1). The average specific powers produced by the two pontellids during out-of-water jumps (1...
Turbulence decreases the hydrodynamic predator sensing ability of the calanoid copepod Acartia tonsa
The copepod Acartia tonsa is very sensitive to hydrodynamic signals, including those made by approaching predators, and responds with a vigorous escape jump. Whether the presence of moderate turbulence changes this ability to detect hydrodynamic signals was investigated by comparing the response of copepods to velocity gradients created by a siphon flow in turbulent and still water. Turbulence decreased the distance at which A. tonsa initiated escapes from the siphon and increased the capture rate, indicating decreased sensitivity to hydrodynamic signals, but did not trigger unnecessary escape reactions that might produce fatigue.
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.
Marine Ecology Progress Series, 2007
The heterogeneous distribution of water flow over structurally complex environments, such as coral reefs, may play an important role in the interactions between copepods and planktivorous fish by interfering with the copepods' ability to detect and evade predators. The escape response and capture rates of the copepod Acartia tonsa were examined in laboratory flumes that created both unidirectional and oscillatory flow conditions similar to those found near coral reefs. Two turbulent regimes were produced in each flume: 'smooth' flow was formed using a grid collimator and 'rough' flow was generated by placing a branched coral skeleton upstream of the flume's working section. A predator was simulated by a fixed siphon to generate a stimulatory flow field. Copepod detection of the siphon was measured as the distance from the siphon tip to where an escape response was initiated. This reactive distance remained the same in low-flow conditions as in still water, but was reduced by 25% at higher flow speeds, indicating a decline in the copepods' ability to detect velocity gradients formed by the siphon. Rough turbulence regimes intensified the effect of current speeds, resulting in an even shorter copepod reactive distance. Capture rates of copepods by the siphon increased with current speed, wave motion, and in rough flow, while the capture rates of non-evasive prey, Artemia nauplii, did not vary with flume conditions. The differences in capture rates between evasive and non-evasive prey suggest that behavioral shifts in copepod escape thresholds may account for increases in predation by reef-dwelling fishes observed in hydrodynamically complex coral environments.
Swimming and escape behavior in two species of calanoid copepods from nauplius to adult
Journal of Plankton Research, 2013
Subject to high predation risk, all developmental stages of copepods depend on evasive behaviors for survival in pelagic environments. Swim and escape behaviors were investigated in copepods from early nauplius to adult using 3D high-speed micro-cinematography. Parvocalanus crassirostris and Eurytemora affinis are two common estuarine species with broad geographic ranges. The early naupliar stages were mostly immobile, whereas the copepodids and adults spent most of the time actively swimming. Escapes and/or behavioral freezes were elicited by a predator mimic, an abrupt hydromechanical stimulus created by the rapid vertical movement of a 3-mm sphere, and video-recorded at 500 frames-per-second. All developmental stages of planktonic copepods responded with evasive behaviors and responses decreased with distance from the sphere. Maximum response distances were greater and response latencies were shorter in copepodids than in nauplii. Maximum escape speeds increased with copepod size, while the duration of the escape response decreased with the developmental stage. Maximum escape speeds scaled to body length as a power function from early nauplius to adult. Species-specific patterns in escape trajectories were apparent at the first nauplius (N1). These results start to differentiate between performance differences that result from size and design constraints, and those that are due to species-specific behavioral patterns.
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.