At the Aquarium
The egg-yolk jelly’s Aquarium habitat is in the Southern California/Baja gallery.
Eastern Pacific Ocean temperate waters from the Gulf of Alaska to Chile. Also Atlantic Ocean and the Mediterranean insula sea
This jelly’s habitat is temperate water. It alternates between the seafloor and more open inshore waters.
The intact bell of a large egg-yolk jelly is milky white or yellow-white with a translucent margin. The tentacles and oral arms are the same color. The center of the bell contains a tallow mass of gonads visible through the exumbrella. Small jellies vary from milky white to colorless. The egg-yolk jelly is a delicate jelly. Its bell can be reduced to what appears to be lifeless tallow mass. This results when the jelly makes a contact or is disrupted by strong currents. Slightly inside the bell’s margin in the subumbrella there are 16 clusters of thin tentacles each containing a single row of tentacles and 16 rhopalia (sense organs) and 16 lappet. The oral arms are massively folded and are often short as a result of damage to the jelly. They resemble broken yolk running from the bell
Bell diameter to 60 centimeters (2 feet) Tentacles 3-6 m (10-29 ft)
This jelly is a carnivorous predator, feeding primarily on gelatinous zooplankton, especially other jellies. It also preys on copepods, fish larvae, and arrow worms. As the jelly slowly drifts through the water, it captures its prey with its sticky tentacles.
The medusa of an egg-yolk jelly is either male or female. The adult male medusa jelly releases sperm into the water and the female medusa uses her oral arms and tentacles to bring the sperm to fertilize her eggs. The fertilized eggs remain on the female’s oral arms close to her mouth until they develop into ciliated larvae called planulae. At first they are round or oval-shaped, however, within two to three hours they change into a pear shape. Eventually they drop off the oral arms, swimming freely for a time while searching for a suitable substrate on which to attach, usually the bottom of a structure that is shaded and rough. They attach upside-down with their tentacles pointing upward to filter feed. They are now known as sessile planocysts. Depending upon environmental conditions, the planocysts go through one of two reproductive phases, either asexual or sexual. They either bud off non-motile clones of themselves or a phase called strobilation occurs. Strobilation only occurs when the water quality, temperature, and salinity are favorable and food supply is adequate. Miniature medusa-like structures called strobilia are formed on a stalk, one on top of the other like a stack of dinner plates with the most mature on top. The strobilia bud off as individual eyphyra that develop marginal lobes, rhopila, tentacles, elaborate oral arms, and finally, the bell shape of the adult medusa, the form in which sexual reproduction occurs. Each polyp produces up to 45 ephyrae per summer.
This jelly spends a great deal of time motionless or slowly drifting with gentle pulsations. When it “fishes”, it uses short vertical excursions between one and twelve 2 meters (3-40 feet) in depth and at a rate of 0-2 m (0- 6 ft.) with its sticky nematocyst laden tentacles trailing behind. Remaining motionless at the top and bottom of each climb and descent, it is an ambush predator. Swimming vertically it becomes a cruising predator capturing slow moving prey and an ambush predator capturing faster moving prey. Since the moon jelly (Aurelia aurita) moves horizontally, the vertical movement of the egg-yolk jelly maximizes contact with this prey. Large prey are captured using a mass of tentacles to entangle the animal and fire multiple nematocysts whereas smaller hydromedusae such as crystal jellies and ctenophores (comb jellies) are captured through contact with the nematocysts fired from a single tentacle.
Egg-yolk jellies occasionally have juvenile crabs and amphipods living inside and atop their bells. And juvenile Young jacks swimming amongst
The mild, but still unpleasant, sting of this jelly may be due to the adhesive substance on its tentacles that aid it in capturing other medusae.
Egg-yolk jellies have a symbiotic relationship with amphipods that live on the subumbrella, juvenile crustaceans that live on the exumbrella, and juvenile Pacific jack mackerel that travels within the tentacles. How these animals withstand the stinging cells is not known. The shells of the amphipods and crustaceans may offer some protection.
Because this jelly does not swarm, it is not a problem for water sports enthusiasts including beach goers or to the commercial fishing industry. It has some importance in the marine ecosystem because of its predatory consumption of other medusae. Predators of egg-yolk jellies include sea turtles and at least 50 species of marine birds and fishes.
Large eggy-yolk jellies can be confused with the yellow lion’s mane jellies but the egg-yolk jellies have 16-lobed bells compared to the lion’s mane jellies eight lobes. The lion’s manes also have a small amount of red or brown coloration.
The delicate bell of this jelly does not hold its shape well. Rough water can turn it into what looks like a poorly fried egg with a broken yolk.