Prey perception mechanism determines maximum clearance rates of planktonic copepods

Abstract

The ecological consequences of “sit‐and‐wait” (ambushing) vs. “searching” (active feeding) foraging strategies are not well‐understood in marine plankton food webs. We determined the maximum clearance rates of ambush and active feeders to evaluate the trade‐off between foraging gain and predation risk associated with the main foraging strategies in planktonic copepods. We show that maximum clearance rates are similar among feeding behaviors for motile prey but one order of magnitude lower for ambush than for active feeders toward nonmotile prey. The prey size spectrum is narrower and toward relatively larger prey in ambushers compared with active feeders. Prey detection in ambushers relies on the hydrodynamic disturbances and is inefficient toward nonmotile prey but highly efficient for large motile prey. The effective prey perception mechanism in ambushers compensates for the lower prey encounter velocity in ambush feeding copepods compared with active feeding copepods. Therefore, ambushers are more restricted in target prey than active feeders and prey perception mechanism determines the efficiency of planktonic copepod foraging strategies. The lower clearance rates of ambush feeders on nonmotile prey is compensated for by a lower predation risk, which can partially explain the coexistence of both “high‐gain & high‐risk” (active feeders) and “low‐gain & low‐risk” (ambush feeders) foraging strategies in marine plankton food webs.

Feeding of plankton in turbulent oceans and lakes

“…When R c < η 0 , we have the analytical relations , with an empirically determined constant C ν ≈ 1. Also the field of view is important for the encounter rate (Almeda et al ), and is here included by the factor χ ( θ ), accounting for the effects of an opening angle θ for a conical field of view. For a hemispherical field of view, we have χ ( π /2) ≈ 0.8, while χ ( π /4) ≈ 0.45.…”

“…For ambush predators like Gadus morhua L., the turbulent mixing in the surroundings will dominate the encounter rate between predators and prey. Later also the effect of self‐induced locomotion has been included, considering in particular different motion patterns such as cruising and pause‐travel search behavior (MacKenzie and Kiørboe ; Pécseli et al ; Almeda et al ).…”

Bottom-up behaviourally mediated trophic cascades in plankton food webs

“…Rhodomonas salina was kept in exponential growth in B1 medium [35] at 188C. All copepod species were kept in culture at 15-188C and fed with a mixture of cultured plankton as described in Almeda et al [36]. We obtained cohorts of similarly sized naupliar stages by separating adults from the stock culture with 100-200 mm mesh-sieves and placing them in a new tank.…”

“…Behaviour of the grazers was filmed at four different resource concentrations, ranging from 0 to 30.000 cells ml 21 (table 1). These concentrations were chosen to include both the concentration where feeding effort is expected to be at a maximum (intermediate resource concentrations) and at satiating concentration based on previous grazing experiments [36]. All animals were picked individually to ensure a consistent body size between individuals.…”

Top‐down regulation of filamentous cyanobacteria varies among a raptorial versus current feeding copepod across multiple prey generations

“…Although body size is recognised as a master trait affecting ecological functions such as growth, reproduction, and survival (Hébert et al, 2016;Litchman et al, 2013;Vanni, 1987), recent work highlights the importance of feeding traits in controlling food-web interactions (Almeda et al, 2018;Kiørboe, 2011;Kiørboe et al, 2018).…”