Jellies

Not the kind you make from fruit, but the gelatinous, often translucent, floating animals you rarely see in the water.  The Monterey Bay aquarium houses an amazing collection of such jellies, many of them common along the California coast.

Sea Nettles, Monterey Bay aquarium

Sea Nettles are well named. Coming into contact with those long, trailing fringes produces a painful sting.  Since they are colonial, swimming through water where sea nettles are thick would be a really bad idea.

Sea jellies, often mis-named jellyfish (although they are not at all closely related to fish), are very simple animals consisting basically of water and gelatinous goo.

Moon Jelly, Monterey Bay Awuarium

Moon Jellies lack the long tentacles, but a short fringe along the edge of the umbrella secretes sticky mucous that traps suspended particles of food and passes it along to the oral arms in the center that surround the “mouth”.  This jelly was about 6 inches in diameter.

A circular nerve net coordinates the contraction of muscle cells at the edge of the umbrella, giving them the ability to move slowly through the water.  Tentacles lined with stinging cells stun prey that come into contact with them, and ciliated cells in the tentacles then slowly move that food toward the central opening in the underside of the bell, where it enters a gastric cavity for digestion.  There are really no organ systems per se, but simply cells specialized for specific tasks.

Moon Jellies, Monterey Bay Aquarium

Dense aggregations of jellies can indicate some disturbance in normal ecosystem function, e.g., excess nutrients entering from the run-off coming from heavily fertilized agricultural areas.

Even though these sea jellies would seem to offer so little nutrition to other consumers, they are favorite prey items of sea turtles and some sea birds.  Unfortunately, the many plastic bags floating around In our oceans also look like sea jellies, and vertebrates that eat those instead often end up starving to death from digestive tracts impacted with plastic.

Comb Jellies, Monterey Bay Aquarium

Comb Jellies are striking as they flash their neon colors down the length of their bells.  Small-bodied prey attracted to the flashing lights (provided by luminescent symbiotic bacteria), become trapped in sticky mucus and are engulfed.  In fact, these voracious jellies can trap and consume prey 1/2 as big as they are.

Sea Jelly, Monterey Bay Aquarium

An incredibly simple, but elegant body plan.

5 thoughts on “Jellies

  1. Sue,, your photos are absolutely magnificent ! I have seen lots of the jellies, but never taken a photo as good as these !

    • The room of jellies was probably my favorite, with its dim light with gorgeous backlighting of the critters, and accompanied by mood music perfectly suited to the slow movements of the jellies in their tanks.

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