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Aurelia limbata

Aurelia Limbata
Aurelia Limbata, Sea of Okhotsk
Scientific classification
Kingdom:	Animalia
Phylum:	Cnidaria
Class:	Scyphozoa
Order:	Semaeostomeae
Family:	Ulmaridae
Genus:	Aurelia
Species:	A. Limbata
Binomial name
Aurelia limbata (Brandt, 1838)

Aurelia limbata, also called the Brown banded moon jellyfish, is a widely dispersed cold-water jellyfish species of the genus Aurelia. It belongs to the class Scyphozoa in the family Ulmaridae and is characterized by having a brown bell margin and an intricate gastrovascular system. All Aurelia species are transparent but A. limbata is recognizable because of the dark brown trim on the bottom of its' bell, and the yellow or pink hue of the gonads that rest at the highest point of the jellyfishes internal structure.

A. limbata exist all over the Northern Hemisphere including the the Pacific, Atlantic, and Indian Oceans. They breed asexually through a process called strobilation. A. limbata feed on planktonic organisms, copepods, and crustaceans by using their oral arms to bring the caught prey into the their mouth. To deter predators, like decapods, they use nematocysts in order to 'sting' an organism.

Distribution

Species in the genus Aurelia are vastly spread across the world’s oceans but A. limbata exists mostly in the Northern Hemisphere. The Brown banded moon jellyfish has been documented in Alaska, Bering Sea, Canada, Greenland, Gulf of Maine, Japan, Northern Africa, the Sea of Okhotsk, the Northern Pacific Ocean, and off of both coasts of the United States.

These jellyfish have been found anywhere between the ocean surface and about 430 meters deep. A. limbata exist in colder northern waters and is able to withstand a large range of salinity and pressure. They inhabit waters between 2-26 degrees Celsius (35-79 degrees Fahrenheit) and a salinity range of 33.0-33.7 PSU.

A. limbata medusa typically occur in shallow, coastal waters. Staying in the vicinity of the shore protects the jellies from the bigger jellyfish that prey on A. limbata that live in the deep water. Another reason they are found in coastal waters is because jellyfish prefer man-made structures because their polyp offspring can easily attach and thrive there.

Description

Aurelia species are often identified by four horseshoe shaped gonads present in the center of the bell and typically have a shallow, wide bell. The adult medusae are typically translucent, but the color of their gut can change depending on their diet. If a moon jelly eats brine shrimp, the gut will have a yellow hue, but if they feed on crustaceans, their gut typically has a pink or light purple hue.

Multiple young A. Limbata swimming at Nagoya Aquarium.

A. limbata typically has a light blue bell with a yellow or orange tinted gut but is known for its distinctive brown color along the margins of the bell. The gonads can be light pink or brown in females, or a darker purple in males. A. limbata has a documented bell size ranging from 10-50 cm in diameter and 3-5 cm in height. The polyp form of A. limbata ranges from 0.9-2.5 mm from the hypostome tip to the basal disc. It has 4 oral arms that are the length of the bell, 16 marginal lappets that are short and broad, an incredibly complicated canal system, and many short tentacles. The gastrovascular system looks similar to mesh due to its intricate complexity.

Life Cycle of Cnidaria beginning at fertilized egg developing into sexually mature medusa

Life Cycle

The medusa of A. limbata are gonochoristic, which means they are either male or female. The two main life stages of A. limbata are medusa and polyp. Medusa are the free-swimming organisms with distinctive U-shaped gonads in the bell, which produce gametes into the water, through a process called broadcast spawning. After the egg is fertilized, a planula larva forms. The microscopic larva settles on the bottom and attaches itself to a hard substrate, which then grows into a polyp.  The polyps lose their tentacles and go through a process called strobilation. Individuals begin budding off the Strobila until only the original polyp is left. These free-floating individuals are called Ephyra and will eventually turn into sexually mature medusa.

Diet

Aurelia limbata generally feed on small zooplankton, fish eggs, crustaceans, and other gelatinous zooplankton. Medusas have also been observed eating copepods, phytoflagellate, and POM, or particulate organic matter, made of bivalve meat. Aurelia can also be efficient filter feeders and when they ‘bloom’ the overwhelming number and density of the organisms can employ top-down control on the planktonic food web. Polyps of A. limbata feed on planktonic ciliates and small shrimp. Prey is typically caught by the jellyfishes tentacles and then brought to the mouth using the oral arms. When a sensor, called a Cnidocil, is triggered on a moon jellies tentacle, pressure builds up inside the nematocyst, which causes the barb inside to shoot out and inject the organism with venom. This stuns both prey and predator, which gives time for either the jellyfish to grab the prey or alerts the predator that the jellyfish is not an easy meal.

Predation

Aurelia are known for being a part of many food chains as is there is a large variety of predators that eat them. Both the Medusa and Ephyra life stages of A. limbata are preyed upon by larger jellyfish, like the sea nettle and the fried egg jellyfish. They are also prey to decapods, other crustaceans, sea anemones, and species in the phylum Echinodermata. The most recognizable and common of the Aurelia predators are the Ocean Sunfish and Leatherback sea turtle. The polyps are also preyed upon by gastropods and crustaceans.