Chemoreception and the deformationof the active space in freely swimming copepods: a numerical study

Abstract

A three-dimensional alga-tracking, chemical advection–diffusion model was used to calculate the deformation of the active space surrounding an alga entrained within the flow field around a freely swimming copepod. From the model, the advance warning time resulting from the copepod's chemo-reception of the entrained alga was quantified, and copepod chemoreception capability compared for several different swimming behaviors: hovering in the water, swimming slowly (swimming upward, swimming backward and swimming forward), swimming fast (swimming upward, swimming backward and swimming forward) and sinking (with the anterior pointing upward or downward). The results show that when it hovers or swims slowly, a copepod can use chemoreception to remotely detect individual algae entrained by the flow field around itself. In contrast, a fast-swimming copepod is not able to rely on chemoreception to remotely detect individual algae. The possibility of a free-sinking copepod using chemoreception to detect algal particles is also indicated. It is shown that advection by the fluid motion dominates over diffusion in transporting the chemical signals inside the active space to the location of a copepod's chemoreceptors. The feeding current structure for a hovering copepod is described. It is suggested that the feeding current structure and re-routing or re-orienting response by a copepod in response to its antennule or other cephalic appendage inputs allow the copepod to capture the food particles that would otherwise pass outside its capture area and increase the amount of food captured.