Ask the Aquarium: Does Anything Eat Jellyfish?
BY SHERRY WHITE
Special to The Pilot
Q. Does anything eat jellyfish?
A. Yes, and more than you might think!
Tuna, shark, swordfish, spadefish, banner fish, ocean sunfish, blue rockfish, sea turtles and even other jellyfish dine on these gelatinous orbs.
A species of Pacific salmon, a type of goby off the coast of Africa and mushroom coral in the Red Sea also find them irresistible. Sea slugs are also known to feed on young jellyfish polyps and can store the jellies' stinging cells for their own use, and it's thought that other marine animals graze on the young polyps.
In countries such as China and Japan, people consider jellyfish a culinary delicacy.
Two marine animals in particular are reputed to be major jellyfish consumers - leatherback sea turtles and ocean sunfish.
Leatherbacks can weigh 2,000 pounds and feed almost exclusively on jellies. Ocean sunfish can weigh in at nearly 5,000 pounds. Ridley and loggerhead sea turtles also eat the floating spheres, and some sea snails and crabs nibble on jellyfish tentacles. Sea birds will eat jellies by pecking at the inner tissue to avoid the tentacles.
Jellies are 95 percent water, thus requiring predators to consume large quantities to glean much nutritional value.
One has to wonder how jellyfish predators avoid stings. One factor to consider is that although all jellyfish can sting, not all pack the same punch.
Examples are the common moon jelly and cannonball jelly, whose stings aren't strong enough to penetrate human skin.
In addition, jellyfish predators often have thick skins, tough scales or mucus-covered bodies that prevent penetration. Still, how some tolerate the painful, toxic stings is not fully understood; however, it's thought some predators build up immunity.
Jellyfish deliver stings via thousands of small, capsule-like structures called nematocysts that line their tentacles. Depending on the species, tentacles can range from a few feet to more than 100 feet in length. The nematocysts house barb-like, spring-loaded lances that fire when triggered by the slightest disturbance. Even after a jellyfish is beached, its nematocysts can still discharge.
Although most jellyfish exhibit a slight pulsing motion for a bit of locomotion, they rely primarily on waves, currents and, in some cases, winds for transportation.
Surprisingly, a variety of sea animals live on or among jelly tentacles, notably certain types of crabs, shrimp and small fishes. Such an arrangement provides food, shelter and protection for the hitchhikers.
Jellies are found in all seas and oceans worldwide. There are also freshwater and deep sea varieties, and new species continue to be discovered. These graceful drifters often appear en masse in what are called "blooms" or swarms that can number as many as 100,000 individuals.
The state operates three public aquariums: one in Pine Knoll Shores, another at Fort Fisher and a third on Roanoke Island. The aquariums are administered by the North Carolina Department of Environment and Natural Resources, and are designed to inspire appreciation and conservation of North Carolina's aquatic environment.
For more information about the Aquariums, visit www.ncaquariums.com.
Sherry White works for the public affairs office of the N.C. Aquariums.
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