Wednesday, 18 May 2016

The upside-down jellyfish: Cassiopea

Cassiopea sp.

Upside-Down Jellyfish

Seeing as my favorite marine animal is a jellyfish, I thought it fitting to choose this guy to post about. On Tuesday, May 17th, our second stop of the day was Zane Gray Creek, a mangrove swamp located on the east side of Long Key.

When undisturbed, the water there is unbelievably clear, making this habitat most suitable for Cassiopea. Like coral, upside-down jellyfish have symbiotic relationships with zooxanthellae, requiring them to stay in high sunlit areas with full clarity to maximize photosynthesis. They rest on the bottom with their oral arms oriented upward to speed the growth of the zooxanthellae that grow in their tissues which, in turn, give the jelly nourishment. 

As a cnidarian, this jellyfish has an asexual and sexual reproduction. It reproduces asexually by budding when it is in a polyp form (attached to bottom). When it is in a medusa form (free-floating), it reproduces sexually. The medusa female produces the eggs and keep them. As the male produces the sperm and releases them in the water, the female uses its tentacles to bring the sperm to fertilize its eggs.

Cassiopea are carnivorous and eat small animals from the sea or just pieces of them after it paralyzes its prey with its mucous and nematocysts.

Their sting is mild, producing a transparent sheet of mucus in the water above them which lifts into the water column to be encountered by an unsuspecting swimmer, leaving a red-rash skin irritation.

Cassiopea xamachana     Photo: Jenna Martin

If you know any Greek mythology, Cassiopea is named after the beautifully vain queen Cassiopeia, the wife of king Cepheus of Ethiopia. As punishment for trying to sacrifice her daughter, Andromeda, Poseidon chained her upside-down to a throne in the heavens. The northern-sky constellation, an upside-down chair, is also named after her.
For more information click here!

During our visit to Zane Gray Creek, I observed at least two species of Cassiopea:

      • Cassiopea andromeda (right)
      • Cassiopea xamachana (above)

Being appropriately named, they are definitely beautiful creatures!

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