They are easily distinguished from the spotted jellyfish by the almost complete loss of spots on the exumbrella and the almost complete loss of their clubs, an appendage attached to the oral arms.
22.
This is a primitive gut or digestive cavity with only one opening that is used for ingestion and excretion; there are four long oral arms with crenulated margins that are the primary feeding surface.
23.
The oral arms ( of which there are usually four ) are located around the mouth and hold the stinging cells, or cnidocysts, which are used to inject potential prey ( or potential predators ) with venom.
24.
In species for which suspended food particles are important, the tentacles and oral arms often have rows of cilia whose beating creates currents that flow towards the mouth, and some produce nets of mucus to trap particles.
25.
Because the sting of this jellyfish is so weak, many small crustaceans, including larval crabs ( " Cancer gracilis " ) and Amphipoda, regularly ride on its bell and even steal food from its oral arms and tentacles.
26.
Traditional processing methods, carried out by a " Jellyfish Master ", involve a 20-to 40-day multi-phase procedure in which after removing the gonads and mucous membranes, the umbrella and oral arms are treated with a mixture of table salt and alum, and compressed.
27.
In medusae the tentacles round the edge of the bell are often short and most of the prey capture is done by " oral arms ", which are extensions of the edge of the mouth and are often frilled and sometimes branched to increase their surface area.
28.
The rarely encountered deep-sea jellyfish " Stygiomedusa gigantea " is another candidate for " largest jellyfish ", with its thick, massive bell up to wide, and four thick, " strap-like " oral arms extending up to in length, very different from the typical fine, threadlike tentacles that rim the umbrella of more-typical-looking jellyfish, including the Lion's Mane.
