How the bending mechanics of setae modulate hydrodynamic sensing in copepods

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Copepods that catch prey using feeding currents beat their cephalic appendages to generate flow entrainment, and detect the presence of nearby prey through the mechanoreceptional setae on the antennules and other appendages. It remains unclear whether the feeding current can be used by the copepod to gain information about its surroundings by sensing when the current is disturbed by nearby particles. In this article, we present a numerical model to address how much the presence of free-floating prey can alter the feeding current velocity field, and how these prey-induced disturbances modify setal deformation patterns. We prescribe the beating strokes of the feeding appendages, and quantify the changes in the bending flows across the setae and setal deformations due to the prey entrainment. We find that, first, the seta bends more due to the time-averaged velocity component of the feeding current, while filtering out the oscillatory component. Second, 100 μm diameter freefloating prey do not induce any noticeable change in deformations of the proximal and distal setae unless they are less than 10 or 5.5 prey radii from the antennules, respectively. Larger prey cause bigger flow disturbances than small prey, which are expected to be even harder to detect. Last, if setae are responsive to changes in deformation relative to the deformations in the absence of prey, the distal seta may have long-ranged sensitivity to assist in detection of prey near the proximal seta, but if setae are responsive to absolute changes in deformation, both setae have very short-ranged sensitivity.

Section: Setal Deformation Due To Free-floating Prey Free-floating Prey Near the Distal Setamentioning

confidence: 99%

Section: Deformation Of Setamentioning

confidence: 99%

Section: Bending Flow Across Setamentioning

confidence: 99%

Section: Deformation Of Setamentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Can the mechanoreceptional setae of a feeding‐current feeding copepod detect hydrodynamic disturbance induced by entrained free‐floating prey?

Shen

Yao

Marcos

et al. 2021

Self Cite

The response of a freshwater copepod to small‐scale, dissipative eddies in turbulence

Ruszczyk

Webster

Yen

2023

The freshwater copepod Hesperodiaptomus shoshone was exposed to a Burgers vortex, a flow feature meant to mimic small‐scale, dissipative turbulent eddies found in the organism's environment, to determine how this copepod responds to microscale turbulent flow structures. Male and female H. shoshone were separately exposed to four turbulence intensity levels plus a negative control (i.e., stagnant flow) in two vortex orientations relative to gravity. H. shoshone demonstrates a mild behavioral change in the presence of a Burgers vortex that is dependent on both sex and vortex orientation. H. shoshone swim with fairly linear trajectories across all four levels of turbulence intensity, which is a notable difference from the swimming behavior of marine copepods exposed to the same flow feature. Variations in morphology, physical environment, or ecological niche between H. shoshone and marine copepods are potential factors that may explain the differences in how the species respond to a Burgers vortex. The setal array of H. shoshone differs from the setal array of the previously studied marine copepods, suggesting differences in sensory ability and response. The small pond habitat of H. shoshone is rarely or intermittently mixed, creating a different hydrodynamic landscape compared to the ocean, which may influence the copepod/turbulence interaction. H. shoshone has few, if any, naturally occurring predators whereas marine copepods have many, which may influence the difference in response to microscale turbulence.

High‐speed escape jumps in haptophytes: Mechanism and triggering fluid signal

Miano,

Asadzadeh,

Ryderheim

et al. 2024

Some planktonic organisms can remotely sense and evade predators by powerful escape jumps. Remote perception typically happens through the fluid disturbance generated by the approaching predator or its feeding current. In copepods and ciliates with mechanosensors, the perception and jump mechanisms are well understood. But how some flagellates perceive the fluid disturbance and achieve similar relative speeds with only two flagella is less explored. Here, we examined the ability of three haptophytes, Chrysochromulina simplex, Prymnesium polylepis, and Prymnesium parvum, to sense and evade the fluid disturbance generated by the feeding current of a copepod nauplius. Chrysochromulina simplex has a long haptonema (14 cell diameters), while the haptonema of the two other species are shorter (1 and 0.5 cell diameters). Only C. simplex responded to the fluid disturbance by fleeing at high speeds. The jump mechanism consists of two phases: the rapid coiling of the haptonema that pulls the cell about two cell diameters in the direction of the haptonema, followed by flagellar reversal and high‐speed swimming (70 cell lengths per second) in the opposite direction. We rationalize cell displacements and escape speeds from haptonema and flagellar kinematics and fluid dynamics. Using a microfluidic channel, we demonstrate that the component of the fluid signal that triggers the jumps is the maximum deformation rate rather than the magnitude of deformation. High‐speed escape jumps may be an avoidance mechanism evolved by haptophytes with long and coiling haptonema, while species with shorter haptonema may use other defense mechanisms, such as stealth and toxicity.