Casseopea - Upside Down Jellyfish



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I ran into these little critters on a day paddle in Coupon Bight in the Florida Keys. Fascinating little creatures of widely varying shapes and colors were all over the bottom of this protected mangrove bay.




These jellyfish are found throughout the Gulf of Mexico and up the Florida Keys and in some of the shallow bays in Bermuda. They are an introduced species in Hawaii, having ridden in the hold waters of visiting cargo ships. There are many forms of them found in the same area. Some look like wayward jellyfish with longer tentacles protruding UP from a bell and others look like a lost head of cauliflower growing out of the bottom. They are relatively harmless, although the tentacles do have nematicysts (stinging cells) that make them feel sticky to the touch. Some people may get a slight stinging or itching sensation or light rash if sensitive skin is contacted, but by and large they are harmless to humans. The tentacles provide a means for the jellies to eat small fish, shrimp and zoo plankton, but their major food source is the algae that line their tentacles and give them a green, brown and rarely a blue color. They position themselves in clear warm shallow calm waters where their algae can grow peacefully in the strong sunlight. The algae provide a portion of their feeding needs. The rest is gotten from filter feeding the water and capturing small fish and shrimp in their tentacles. Since their structures are not very strong, they prefer shallow bays of quiet water where they can grow in abundance. I first saw them in Coupon Bight in the Florida Keys.

The bell of the Casseopea has a concave depression which they use to create a suction on the smooth bottom to help hold them upside down. Although they can swim, they spend most of their lives upside down sucking the bottom. Like most jellies they are mostly water, 95% water, 3% salt and 2% protein.


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The scientific name for these beauties is Cassiopea. it seems that the scientist are fond of Greek mythology for the lowly jellyfish. Although the Greek goddess is usually spelled Cassiopeia and the jellyfish is always spelled Cassiopea. This is especially confusing when one of the sub species is named Cassiopea Andromeda. ( In Greek mythology Andromeda was Cassiopeia's daughter. Both are star names.) Maybe the naming scientist wasn't quite up on his spelling either. The other species I have been able to locate is Casseopea Xamachana.

Cassiopeia - the vain Queen of Ethiopia


Cassiopeia-A supernova remnant in constellation Cassiopeia

They reproduce bisexually with eggs of the female fertilized by sperm released in the water from nearby males. The fertilized eggs are moved to tentacles near the center of the female until they develop into larvae. The larvae metamorphose into planulae, a flat free swimming stage that searches for a place to settle, attaching itself with a thin film to a hard surface. There it changes into a polyp with tentacles. it is during this stage that the jelly acquires it symbiotic algae, as they are not passed on from the adult. If the feeding is good and the water warm, the polyp can reproduce by asexual budding and dropping off another polyp that attaches immediately, giving the species a second and very efficient way of multiplying. Once mature in the polyp stage it begins to pulse (strobilate) and develops into the final Medusa form, completing the five stage cycle of egg, larvae, planula, polyp and Medusa.




While the symbiotic jellies get most of their carbon requirement from the algae growing in and on their oral arms, they do need to supplement their diet with captured food. When hapless small animals are captured by the stinging cells of their feeding arms they are pulled apart and consumed by multiple secondary mouths on the arms. The more common central mouth of most jellies has been closed in favor of the distributed secondary mouths.

Crabs sometimes grab these jellies and place them on the back of their shells as camouflage and protection.

Phylum Cnidaria
Class Scyphozoa
Order Rhizostomeae
Family Cassiopeidae


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