How do jellyfish eat and poop?
Jellyfish use the same body opening for both eating and expelling waste.
Jellyfish have a single opening that serves as both a mouth and an anus. Located in the center of their bell-shaped body, this opening leads to a digestive pouch where food is processed. After absorbing nutrients, they eject undigested material back through the same opening. This simple anatomy has allowed them to survive for over 500 million years.
Nerd Mode
Jellyfish belong to the phylum Cnidaria, a group of animals characterized by a 'blind gut' or gastrovascular cavity. Unlike humans who have a complete digestive tract with two separate openings, cnidarians possess an incomplete digestive system. This means the single opening must handle the ingestion of prey and the egestion of metabolic waste.This anatomical setup is highly efficient for their low-metabolic lifestyle. According to marine biologists at the Smithsonian National Museum of Natural History, jellyfish have thrived using this body plan since the Cambrian Period, roughly 500 to 600 million years ago. Their digestive pouch uses specialized cells to secrete enzymes that break down small fish and zooplankton captured by stinging nematocysts.While this system seems primitive, it is a masterclass in evolutionary conservation. Research published in journals like 'Nature Communications' highlights how jellyfish can expand their gastric cavity to consume prey larger than themselves. Once digestion is complete, the muscular contractions of the bell help force the remaining waste out of the same orifice to clear the cavity for the next meal.
Verified Fact
FP-0002454 · Feb 16, 2026