Читать книгу Life in the Open Ocean - Joseph J. Torres - Страница 78

Perspective is important when evaluating the foraging behavior of medusae. Equipped with rudimentary sensory systems and limited locomotory capabilities, they forage in a profoundly three‐dimensional environment. Prey are captured on tentacles deployed in a stationary ambush or a slowly moving array as the animal swims forward. Stinging cells (nematocysts) on the tentacles paralyze the prey, which are then conveyed to the mouth and digested. Since both locomotion and the sensory field are quite limited, feeding success of a medusa will be determined by the number of its physical encounters with prey and the effectiveness of its tentacles in subduing the prey item.

In their mathematical model of predator–prey interactions in zooplankton, Gerritsen and Strickler (1977) assumed that the “encounter radius” of a predator was determined by its sensory system. In the case of medusae, it is determined by the volume enclosed within their tentacle array and the likelihood that a prey item once within the “kill zone” will contact a tentacle and be trapped (Madin 1988).