Prey Detection and Prey Capture in Copepod Nauplii

Abstract

Copepod nauplii are either ambush feeders that feed on motile prey or they produce a feeding current that entrains prey cells. It is unclear how ambush and feeding-current feeding nauplii perceive and capture prey. Attack jumps in ambush feeding nauplii should not be feasible at low Reynolds numbers due to the thick viscous boundary layer surrounding the attacking nauplius. We use high-speed video to describe the detection and capture of phytoplankton prey by the nauplii of two ambush feeding species (Acartia tonsa and Oithona davisae) and by the nauplii of one feeding-current feeding species (Temora longicornis). We demonstrate that the ambush feeders both detect motile prey remotely. Prey detection elicits an attack jump, but the jump is not directly towards the prey, such as has been described for adult copepods. Rather, the nauplius jumps past the prey and sets up an intermittent feeding current that pulls in the prey from behind towards the mouth. The feeding-current feeding nauplius detects prey arriving in the feeding current but only when the prey is intercepted by the setae on the feeding appendages. This elicits an altered motion pattern of the feeding appendages that draws in the prey.

Feeding capabilities and limitations in the nauplii of two pelagic estuarine copepods, Pseudodiaptomus marinus and Oithona davisae

“…Although knowledge of feeding mechanisms is limited Bruno et al 2012), the main factors influencing feeding by nauplii in the field likely include (1) the size, morphology, motility, and density of food particles (Berggreen et al 1988); (2) the motility, swimming speed, and feeding behavior of the nauplius (Frost 1977;Kiørboe 2010); (3) the morphological constraints of the nauplius, such as the size of mouthparts and feeding appendages (Fernandez 1979); (4) the ability of the nauplius's rudimentary sensory apparatus to detect prey (Svensen and Kiørboe 2000;Bruno et al 2012); (5) the perception of predatory threats, which can alter the nauplius's movement or feeding behavior (Tiselius et al 1997); and (6) the feeding history of the nauplius (Donaghay 1985).…”

“…This feeding mode is described as most effective for capturing motile prey (Atkinson 1996), but ineffective for capturing nonmotile prey (Kiørboe 2010). Neither the adult nor the nauplius stage of O. davisae generates a feeding current, and both are thought to rely instead on the perception of hydromechanical cues to remotely detect moving prey, capturing it raptorially (Svensen and Kiørboe 2000;Bruno et al 2012).…”

Distinctly different behavioral responses of a copepod, Temora longicornis , to different strains of toxic dinoflagellates, Alexandrium spp.

“…Most previous studies of the response of copepods to toxic algae are incubation studies, in which the net outcome of the copepod-prey interaction is quantified in terms of feeding rate, prey selection, growth or egg production rate, or other similar bulk measures (reviewed by Turner, 2014). The direct video observation of individual responses and of direct copepod-prey cell interactions provided by this and a few other studies (Bruno et al, 2012;Hong et al, 2012;Tiselius et al, 2013) Selander et al, 2006;Teegarden, 1999). The fact that the copepods can distinguish between cells of very similar size and shape suggests that selection is mediated by chemical information.…”

Ciliates in Planktonic Food Webs: Communication and Adaptive Response

“…Nauplii perform attack jumps against moving prey that touches their sensory setae. Interestingly, these jumps are not directed towards but past a prey and the nauplius sets up a strong intermittent feeding current pulling the prey to the mouth (Bruno et al 2012). Consequently, a prey ciliate has to be moving to be detected.…”