Table 1.

Parameters used in the calculation of forces exerted on the prey

Input variablesParametersSource
tnul, tmax, hnul, hmax, α, plateauChange in gape size with timeFitted for each sequence based on observed kinematics
tnul, tmax, hnul, hmax, α, plateauChange in mouth displacement with timeFitted for each sequence based on observed kinematics
tnul, tmax, hnul, hmax, α, plateauChange in flow speed with timeEstimated based on gape kinematics
Cd, Re=300–10 000Based on Kils (Kils, 1982)*
Cd, Re=10 000–85 000Measured
Added mass coefficient (Cam)Estimated based on the fit of observed and calculated force
Strike initiation distanceMeasured
Prey lengthMeasured
Prey diameterMeasured
Prey volumeCalculated based on length and diameter
  • Parameters were recalculated for each strike, based on observed kinematics. Definition of input variables, used to calculate continuous functions for gape, mouth displacement and flow speed, followed Muller et al. (Muller et al., 1982): tnul, initial value of the kinematic variable of interest; tmax, peak value; hnul, time of initiation (first deviation from tnul); hmax, time of peak value; α, a form coefficient for the rate of increase; plateau, the amount of time spent at peak value; Cd, drag coefficient (based on wetted area); Re, Reynolds number. The temporal patterns in flow speed were estimated based the relationships observed by Day et al. (Day et al., 2005)

  • * Based on measurements for Euphausia superba, similar in size and shape to ghost shrimps