The polyp that packs a wallop

Okay, here's the follow-up to last night's post, "The little one with the long tentacles."  

Below is another photo showing a different individual, but the same type of animal:

 

And here are two close-ups showing the stinging tentacles, and a view of the mouth area in the middle of the ring of tentacles:

 

 

The stinging tentacles are a clue that this is a cnidarian (i.e., the group that contains jellyfish, sea anemones, corals, etc.).  But which one is it?

Because this stage of the life cycle is so small (only a few millimeters long), many people haven't seen it before.

These are jellyfish polyps (also known as scyphistomae)!  Eric found them growing on sea squirts at the Spud Point Marina docks.  

Referring to the diagram below, the basic life cycle goes like this: free-swimming adult medusae release gametes (eggs or sperm); a fertilized egg develops into a planula larva; the planula eventually settles and undergoes metamorphosis into a benthic (bottom-dwelling) polyp; the polyp eventually undergoes fission — i.e., it buds off tiny juvenile medusae (called ephyrae) that eventually grow into the adults to complete the life cycle.

 

Modified from:  Living Invertebrates by Vicki Pearse, John Pearse, Mildred Buchsbaum, and Ralph Buchsbaum.  1987.  Blackwell Sci. Pub. and Boxwood Press.

In the image below, the polyp might be in the early stages of strobilation (note the banding pattern in the polyp):

 

And here's one more showing the beautiful but deadly tentacles (at least to tiny, microscopic prey):

 

P.S.  I'm not sure which species of jellyfish this is, but perhaps someone will recognize it and let us know.