Jellyfish Facts: Moon jellyfish (Aurelia sp. & Aurelia aurita)

Moon jellyfish (Aurelia aurita) are from the phylum Cnidaria. This phylum contains over 9,000 aquatic species. While estimates vary due to morphological similarities, there are somewhere between ten and twenty species belonging to the genus Aurelia. To the naked eye they are identical. One can only be differentiated from another through DNA testing. All of these species are collectively referred to as moon jellyfish. 

Moon jellyfish are the most common jellyfish on the planet. This is because of their diversity in nature. Moon jellies can be found in almost every ocean in the world. Their natural habitat stretches from the equator as far north as 70° latitude and as far south as 40° in every ocean that falls within those geographic parameters.

They are prominent in the shallow coastal waters of estuaries and harbors which explains their abundance in the jellyfish aquarium tank industry an infant branch within the larger saltwater aquarium trade.  Because they are common in both temperate and tropical waters, they can tolerate temperature ranges anywhere between 42-88 °F (6-31 °C). Although they can survive in brackish water, a salinity level (specific gravity) of 1.023 will mimic their native marine environment.

In nature, moon jellies spend most of their time drifting on currents rather that swimming. In captivity, a jellyfish aquarium tank requires a specially designed turbulence system to keep these delicate creatures from becoming a helpless ball of gelatinous goo at the bottom of your tank. 

Fortunately, enterprising enterpreneurs at JellyfishArt have taken the necessary steps to design and produce a  jellyfish aquarium fish tank  specifically engineered to make keeping pet jellyfish no more complicated than your average freshwater aquarium. As a result, moon jellyfish are becoming immensely popular as pets. Just three years ago there was no such thing as a desktop jellyfish aquarium.   Moon jellyfish are one of the most easily obtainable jellyfish for home aquarium owners who wish to expand their area of expertise.  They are also the easiest jellyfish to keep alive and healthy in captivity.  The concept & design team at JellyfishArt captured  live moon jellyfish from the temperate coastal waters off the coast of California.  They then bred and tank raised Moon Jellyfish  for Sale to the general public to insure their year round availability for the demand created by this new, up and coming segment of the home aquarium industry.

Check Out JellyfishArt's Desktop Jellyfish Aquarium

In the wild moon jellyfish can easily grow to up to 12 inches in diameter. Commercially tank raised moon jellies typically range in size from 2-5 inches in diameter. Their growth rate and maximum disc size is proportional to their caloric intake. This means that in a jellyfish aquarium tank they may never grow to their potential maximum disc size. You can, in fact, prevent them from doing so if you wish to keep them in a smaller aquarium. 

Jellyfish are carnivorous. In nature a moon jellyfish's diet consists almost entirely of zooplankton. In a jellyfish tank, pet moon jellies can be fed commercially available frozen or freeze-dried plankton food products or live brine shrimp. Brine shrimp are readily available at any fish specialty store that sells saltwater fish. Many aquarists prefer to raise their own brine shrimp. See Jellyfish Aquariums for more details on feeding pet jellyfish.

  Jellyfish Facts: Blue Blubber Jellyfish (Catostylus mosaicus)

The blue jelly’s unique appearance makes it one of the more exotic jelly specimens currently available to home aquarist. They have become increasingly popular as pets in the Eastern hemisphere because of their almost “other worldly” look and their abundance. Unlike moon jellyfish, blue jellies are translucent rather than transparent. They do not have that eerie, floating ghost-like appearance when light flows through them. They look, however, equally stunning under an LED fader. The combination of their globular shape, they way they swim, their pearlescent reflection, and the colored light passing through  their semi-transparent bodies makes them resemble the globules in a lava lamp. They also look great under T5 and actinic lighting. They come in a variety of colors including white, red, blue, purple, and yellow with hues of contrasting accent shades. 

Upside down jellyfish (Cassiopeia xamachana) are another member of the order Rhizostomae. The species name, xamachana, means Jamaican although their natural habitat is in no way exclusive to Jamaican waters. Populations exist throughout the Gulf of Mexico and Caribbean as well as along the coats of Florida. They are also present half way across the globe in the Pacific Ocean.  

Upside down jellyfish populations have also established themselves along the coastal shores of the Hawaiian Islands. It is speculated that these creatures where first introduced to Hawaiian shores from jellyfish polyps adhering to the underbellies of war ships returning from the Philippines. 

This species is prevalent in shallow, warm tropical waters such as mangrove swamps. They are frequently referred to as mangrove jellyfish of the large aggregations found in this swampy saltwater environment. Unlike many species of jellyfish, upside down jellies are exclusively marine in nature. None have been found in brackish or freshwaters.

 These jellies differentiate themselves from most species of jellyfish in yet another significant manner. Most jellyfish spend the entirety of the adult phase of their lives drifting haplessly on ocean currents. Upside down jellies are only free swimming as juveniles. Once their bell reaches approximately 2cm in diameter it inverts. The jellyfish then sinks to the bottom of its shallow watered domain. They spend the entire adult stage of their lives upside down on the muddy substrate. This points their oral arms (tentacles) in an upward position which allows them to capture and absorb an endless found source from the ever present zooplankton existing in water columns throughout the world’s oceans.

Much like blue jellies, upside down jellyfish have a symbiotic relationship with zooxanthellae. This is the same symbiosis that occurs with many jellyfish and coral species.  In addition to providing essential nutrients, these golden algae also produce oxygen to help support respiratory metabolic functions the jellyfish needs to survive in oxygen poor environments. This is of particular importance to upside down jellyfish because they spend the vast majority of their life nestled in muddy substrate and must rely on their food to come to them. Because of their specialized eating habits, upside down jellyfish are usually found in nutrient rich waters with high concentrations of decaying matter to support the zooplankton teaming within these swampy, saltwater environments.

Upside down jellies have flat, saucer shaped bells. Their umbrellas are typically greenish grey or blue in color. They have a central depression or exumbrella in their bell. The exumbrella acts as a suction device to help them stay anchored to the ocean floor. Rather than a single mouth opening, they have 4 elaborately branched oral arms. These arms have a frilly, lace-like appearance similar to many green, leafy vegetables. They are often referred to as cabbage-head jellyfish because of these appendages. It is believed that this species a filter feeder and also relies on some form of absorption of dissolved nutrients directly from the water to supplement its nutritional needs. 

Upside down jellyfish do not directly inject their prey like most jellyfish do. Their nematocysts (stinging cells) are controlled by the cnidocil. This is the equivalent to a mechanically or chemically triggered grenade launcher. The stinging cells launched from the cnidocil produce a cnidoblast that will stun or paralyze prey in the immediate vicinity. The jellyfish then begin ingesting their prey with their primary mouth openings. Once the prey is reduced to food fragments, these nutrient particles are passed on to secondary mouths for further digestion.

Sea Nettles are one of the most popular exhibits in public aquariums. Their movement looks like sheer poetry in motion. Sea nettles inhabit the Atlantic (Chrysaora fuscescens), Pacific Ocean (Chrysaora quinquecirrha). Depending on the species, they grow anywhere from 6 inches all the way up to three feet in diameter. Typically their trailing tentacles reach over twice that length. Pacific sea nettles are the larger of the two species. The Pacific sea nettle was successfully cultivated in Monterey California less than two decades ago. This was the first time they had ever been bred in captivity. Monterey was the first aquarium to exhibit jellyfish to the public.

A sea nettle’s sting in very often deadly to proportionately sized prey. Their sting is rated from moderate to severe in regards to human interaction. Their venom is not lethal unless it is the result of an allergic reaction. They will cause moderate discomfort levels in people that are not overly sensitive to jellyfish toxins. Toxicology reports on Japanese sea nettles (Chrysaora melanaster) indicate more serious reactions.

Sea nettle bells are semi-transparent. Pacific sea nettles can either be white and opaque in appearance or striped. Striped bells are typically reddish-brown adorned with small white dots. The species 

Unlike most jellyfish, sea nettles are very good swimmers and swim continuously. They seem to prefer swimming against the current which is why they are so often seen swimming upside down in most pictures.  

It should be noted that Pacific sea nettles are the larger of the two species. There are not any readily fabricated aquariums large enough to house them. They will require a custom built set up. You should also be aware that these jellies are indigenous to colder waters, from northern California to Alaska. They are accustomed to water temperatures in the mid-fifty degree range. Your jellyfish aquarium will require a water chiller to accommodate their environmental needs.