WHAT ARE THEY? Jellyfish or jellies are the major non-polyp form ofindividuals of the phylum Cnidaria. They are classified as free-swimming marineanimals consisting of a gelatinous umbrella-shapedbell and trailing tentacles. The bell can pulsate for locomotion, while stingingtentacles can be used to capture prey.
WHAT DO THEY EAT? Jellyfish normally eats whatever their long tentaclescatch while drifting in the ocean currents. A fewspecies of jellyfish like the box jellyfish are goodswimmers and chase their prey. The main foodsources of jellyfish are smaller fishes, eggs andlarvae of sea creatures and zooplankton. The largerspecies of jellyfish eat crustaceans and otherjellyfish.
FACTS The same opening under the body that serves asits mouth is used for releasing excreta from thebody. The food entering the opening is digested inthe cavity attached to it. The waste mattergenerated is expelled through the same opening. Jellyfish is carnivorous and ravenous eaters. Themouth of the jellyfish is located underneath the bell-shaped body. Its simple digestive system consistsof a gastro vascular cavity attached to the oralopening, which does the function of the stomach.
The tentacles are the main devices to catch prey forjellyfish. These tentacles have thousands of cnidocyteswith stinging capsules or nematocysts containingvenom. Even though these creatures are brainless, theirnervous system is highly developed. When the tentaclestouch a potential prey, the cnidocytes are activatedimmediately. They shoot nematocysts at the prey, whichattach itself to the skin of the prey. The venom present inthese nematocysts is released, which in turn stuns theprey. The shocked prey is caught by the arms surrounding theoral opening and brought to the mouth. The food isdigested immediately in the chamber attached to theopening and nutrients absorbed by the body. The wasteis discharged through the same opening.
Many species of jellyfish are passive hunters andwait for their prey to come to them. They havesticky tentacles and drift along the currents waitingfor a prey to get trapped in the tentacles. They eatmostly zooplankton, eggs and larvae of othermarine creatures and crustaceans. Some species of jellyfish are aggressive huntersand they are equipped with potent venom in theirtentacles. This venom when ingested in the preyeither paralyzes or kills it. This group of jellyfishpreys on smaller fishes, crustaceans and evenother jellyfishes. Some jellyfish is known to eatother jellies as large as themselves.