How Do Jellyfish & Sea Anemones Digest Their Food?

It's easy to consider jellyfish predatory -- many a human has felt their stinging tentacles just feet from dry land -- but anemones are estimable predators, as well. potential prey. The Electronic Atlas of the Fauna of British Columbia characterizes anemones as “silent slow-motion predators.” They use stinging tentacles that surround their central mouth structures to immobilize and collect prey. Extremely small stinging capsules cover anemones’ tentacles and serve as their primary weapons, enabling them to pierce the skin of their prey, hold them in place and inject them with a paralyzing poison.

These friendly looking creatures contain powerful digestive enzymes that are capable of breaking down small animals in approximately 15 minutes. After an anemone captures a meal, it moves the the prey into its mouth and consumes it whole, according to the “Journal of the Marine Biological Association of the United Kingdom.” Within the anemone’s central cavity, food disintegrates into nutrients the creature can absorb. The anemone will later expel shells, bones and any other parts it is unable to digest.

Jellyfish passively collect plankton and other delicacies floating in the water. Biologists note that jellies can intentionally propel themselves to create currents that force prey within reach, increasing their proverbial harvest. Like anemones, jellyfish tentacles are covered with tiny stinging capsules -- or, nematocysts -- that act like poisonous barbs. According to the South Carolina Department of Natural Resources, jellies have between four to eight oral arms that help move captured food from the tentacles into the mouth. Jellyfish feed on a steady diet of tiny animal plankton and even other jellyfish. Some larger varieties can consume crustaceans and bigger ocean-dwellers.

According to the National Ocean Service, jellyfish have rather simplified digestive systems -- often referred to by biologists as incomplete. Many animals rely on organs such as the liver, pancreas and intestines to aid in digestion, the jellyfish has none of these. A single cavity, the coelenteron, serves as a jellyfish’s stomach and intestine. Food that makes it into the jellyfish’s stomach is broken down by digestive enzymes produced by cells lining the inner body cavity. These cells help absorb and direct nutrients around the jellyfish body. Jellies have only one orifice into the digestive cavity, which acts as a mouth, for the intake of sustenance, and as an anus, for the expulsion of waste.