Slow-moving predatory gastropods track prey odors in fast and turbulent flow

Ferner, Matthew C.; Weissburg, Marc J.

doi:10.1242/jeb.01438

Cited by 79 publications

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“…This flume produces stable and reproducible boundary layers at current speeds ranging from 1 to 15 cm sec j1 . See Ferner and Weissburg (2005) for a detailed flume description and characterization of the flow environment boundary.…”

Section: Methodsmentioning

confidence: 99%

Hard Clams (Mercenaria mercenaria) Evaluate Predation Risk Using Chemical Signals from Predators and Injured Conspecifics

2006

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Abstract-Hard clams, Mercenaria mercenaria, are sessile, filter-feeding organisms that are heavily preyed upon by blue crabs, which find their clam prey using chemical cues. Clams may evade blue crabs by reducing their pumping (feeding) behavior when a threat is perceived. The purpose of this study was to determine the type of signals that clams use to detect consumers. Clams decreased their pumping time in response to blue crabs and blue crab effluent, but not to crab shells, indicating that chemical signals and not mechanical cues mediated the response of clams to distant predators. Because predator diet can influence prey evaluation of predatory threats, we compared clam responses to blue crabs fed a steady diet of fish, clams, or that were starved prior to the experiment. In addition, we used injured clams as a stimulus because many organisms detect predators by sensing the odor of injured con-or heterospecifics. Clams reduced feeding in response to injured conspecifics and to blue crabs that had recently fed. Clams reacted similarly to fed crabs, regardless of their diet, but did not respond to starved blue crabs. Because blue crabs are generalist predators and the threat posed by these consumers is unrelated to the crab's diet, we should expect clam reactions to blue crabs to be independent of the crab's diet. The failure of clams to react to starved blue crabs likely increases their vulnerability to these consumers, but clam responses to injured conspecifics may constitute a strategy that allows animals to detect an imminent threat when signals emanating from blue crabs are not detectable.

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Section: Methodsmentioning

confidence: 99%

Hard Clams (Mercenaria mercenaria) Evaluate Predation Risk Using Chemical Signals from Predators and Injured Conspecifics

2006

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Section: Dominant Predator-prey Interactionmentioning

confidence: 99%

“…Blue crabs are less successful predators during highly turbulent hydrodynamic conditions (Jackson et al 2007). In contrast, knobbed whelks are successful in highly turbulent regimes (Ferner & Weissburg 2005). Also, blue crabs prefer clams of a small size range despite the fact that they can consume prey over a wide size range (Micheli 1995).…”

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“…For example, blue crabs prefer to consume smaller, more easily crushed clams, depending on availability and level of starvation (Micheli 1995). In contrast, whelks consume clams of all sizes and have predation success in high turbulence intensity regimes (Ferner & Weissburg 2005).There were several clam jet quantities that were significantly different according to the size of the organism. The jet mean vertical velocity was influenced by the bulk mean crossflow velocity (although a pattern is not clear in Table 1), and that influence was dependent on the size of the clam.…”

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Unsteadiness of bivalve clam jet flow according to environmental conditions

Delavan¹,

Webster²

2011

Aquat. Biol.

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To determine whether hard clams Mercenaria mercenaria alter excurrent jet velocity as a function of environmental factors, this laboratory study quantified the excurrent jet velocity as a function of bulk mean crossflow velocity, density of clam patch, and clam size. The excurrent velocity was measured via the non-intrusive particle image velocimetry technique. The flow and unsteady patterns in the time records of vertical velocity near the tip of the excurrent siphon were analyzed by calculating the mean, variance, power spectral density, fractal dimension, lacunarity, and mean jet-to-crossflow ratio. The results revealed that clams vary their excurrent flow characteristics according to bulk mean crossflow velocity; in particular, the texture of the time record of velocity varied. Further, the jet-to-crossflow velocity ratio was larger for smaller clams, and the response of clams to the density of the clam patch was dependent on the size of the animal. These observed behaviors may impact the predation success of blue crabs Callinectes sapidus and knobbed whelks Busycon carica under various environmental conditions. In this context, the results indicated that blue crabs dominate the predator-prey system because of the dependence on clam size and bulk mean crossflow velocity. Alternatively, the varying clam excurrent siphon velocity behavior may provide hydrodynamic signaling of the clam patch recruitment status to settling larvae.KEY WORDS: Predator-prey · Olfactory predation · Jets-in-crossflow · Bivalve · Non-consumptive predator effects · Lacunarity Resale or republication not permitted without written consent of the publisherAquat Biol 13: [175][176][177][178][179][180][181][182][183][184][185][186][187][188][189][190][191] 2011 acteristics of the excurrent flow as a function of bulk mean crossflow velocity and clam size are of interest because the predators of this system, blue crabs and knobbed whelks, both consume clams and use olfactory navigation as a means of locating prey, but the turbulence regimes in which they are successful are highly disparate. Blue crabs are less successful predators during highly turbulent hydrodynamic conditions (Jackson et al. 2007). In contrast, knobbed whelks are successful in highly turbulent regimes (Ferner & Weissburg 2005). Also, blue crabs prefer clams of a small size range despite the fact that they can consume prey over a wide size range (Micheli 1995). Therefore, as clams increase in size, they become less susceptible to predation by blue crabs while maintaining their susceptibility to whelk predation. Thus, there may be alternate strategies for predator avoidance depending on the size of the clams and the turbulence regime of the environment in which they live.The influence of the density of the clam patch was also of interest because there may be predator avoidance strategies depending on the proximity of conspecifics. High-density patches may appear as one large, hard to eat prey to blue crabs, and small clams may have higher survival rates in these ...

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The pirouette effect in turbulent flows

2011

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The disorganized fluctuations of turbulence are crucial in the transport of particles or chemicals 1,2 and could play a decisive role in the formation of rain in clouds 3 , the accretion process in protoplanetary disks 4 , and how animals find their mates or prey 5,6 . These and other examples 7 suggest a yet-to-bedetermined unifying structure of turbulent flows 8,9 . Here, we unveil an important ingredient of turbulence by taking the perspective of an observer who perceives its world with respect to three distant neighbours all swept by the flow. The time evolution of the observer's world can be decomposed into rotation and stretching. We show that, in this Lagrangian frame, the axis of rotation aligns with the initially strongest stretching direction, and that the dynamics can be understood by the conservation of angular momentum. This 'pirouette effect' thus appears as an important structural component of turbulence, and elucidates the mechanism for small-scale generation in turbulence.To an observer who perceives its world with respect to three distant fluid tracers, all carried by the flow, the seemingly random turbulent motion modifies the distances to and between them. Turbulent motion, on average, separates two tracers [10][11][12] . However, as shown in Fig. 1, given a set of four tracers initially located on a regular tetrahedron, that is, with all pairs equally separated by a distance R 0 , the growth of the distance between pairs is very uneven, resulting in strong shape deformation [13][14][15][16] . As first observed in ref. 17, the resulting 'minimal' four-point description provides important insights into the dynamics of turbulence.Remarkably, our study of the relative motion between these neighbouring particles, as shown in Fig. 1, reveals the alignment of the rotation towards the direction of the initially strongest stretching, while the angular momentum remains constant (statistically, see Supplementary Information). This is a manifestation of the 'pirouette effect', well known from classical ballet or ice-skating.We used a particle tracking technique to follow several hundreds of nearly neutrally buoyant, 30 µm size polystyrene particles as tracers in a turbulent water flow 11,18,19 with high turbulence intensities as defined by the Taylor microscale Reynolds number 10,20 350 ≤ R λ ≤ 815. We recorded tracer motion in volumes as large as (5 cm) 3 with a spatial resolution of approximately 20 µm and a time resolution of 0.04 ms by stereoscopic observation using three high-speed cameras. We accurately determined the trajectories and velocities of millions of tracers in three dimensions, from which we extracted the dynamics of initially regular tetrahedra by conditioning statistics on four tracers with nearly equal mutual distances (as in ref. 15 and Supplementary Information). We complemented the experiments by direct numerical simulations (DNS) of the Navier-Stokes equations for 100 ≤ R λ ≤ 170 (ref. 14).The time evolution of the observer's world can be decomposed into rotation and stretching, ...

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Slow-moving predatory gastropods track prey odors in fast and turbulent flow

Cited by 79 publications

References 58 publications

Hard Clams (Mercenaria mercenaria) Evaluate Predation Risk Using Chemical Signals from Predators and Injured Conspecifics

Hard Clams (Mercenaria mercenaria) Evaluate Predation Risk Using Chemical Signals from Predators and Injured Conspecifics

Unsteadiness of bivalve clam jet flow according to environmental conditions

The pirouette effect in turbulent flows

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