About the Order Corallimorpharia - Mushroom anemones and their relatives

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Members of the order Corallimorpharia do not produce hard skeletons, but they are otherwise quite similar to the stony corals (Anthozoan Order Scleractinia - see Overview of Cnidarian Diversity) in certain morphological respects. Consequently, these two orders are considered to be closely related. However, with many corallimorpharians you have to be a specialist in the biology of the Cnidaria to see the resemblance.

 

Mushroom anemone appearance:

 

While some types of corallimorpharians do resemble coral polyps, those refered to as mushroom anemones bear little superficial resemblance to most corals. The polyps are broad and flat, attached to a rock or other hard surface by a stalk, causing the polyps to resemble mushrooms. In most kinds of mushroom anemones the tentacles are reduced to small stubs or bumps scattered across the surface of the disk, though in some types the tentacles are pretty much completely absent.

 

The different sorts of mushroom anemones vary greatly in appearance. Some types are no more more than a few centimeters in diameter, while others can grow to diameters of nearly 30 cm. Some have very smooth surfaces, some have ridged surfaces, others are bumpy or hairy in appearance. They are quite diverse in their coloration as well, with colors including various shades of brown, blue, red, fluorescent green, or other colors either alone or in myriad combinations.

 

Nutrition:

 

All of the mushroom anemones in our aquaria at Augsburg get a large proportion of their energy from symbiotic dinoflagellate algae called zooxanthellae, which live within their tissues. These algal symbionts use photosynthesis to manufacture energy-rich food molecules, some of which leak out of the algal cells to the surrounding animal tissues.

 

Some types of mushroom anemones also feed. Though some types never seem to feed in aquaria (e.g., Discoma species), others close up rapidly around food particles that land on them, looking like a pouch with a tightened drawstring while they are ingesting food. Some species can envelop food so quickly that they are capable of capturing live fish that rest on them.

 

Asexual Reproduction is commonplace in mushroom anemones:

• Some types such as members of the genus Discoma regularly reproduce by pedal laceration. The polyps gradually move to new locations on their rock substrate (a growth process, not creeping or gliding), leaving small bits of tissue behind in their original locations. These small bits of tissue quickly develop into complete polyps in a matter of weeks. By this process, Discoma mushroom anemones can form large patches.
  
  
• In crowded patches of Discoma mushroom anemones, polyps sometimes break free from the rocks and start to drift in the water. If they eventually come to rest in a suitable location they attach in a matter of days, thus founding a new patch.
  
  
• Some of the larger mushroom anemones such as some species in the genus Rhodactis commonly reproduce by splitting in two. When this occurs, they are partially retracted for several days (sometimes a week or more), and the animal appears to be ripping itself apart down the middle (which of course is exactly what is happening!), with each resulting piece ending up with a portion of the foot. One large type of mushroom in our aquaria has on occassion taken this even farther by shredding itself into as many as four or five pieces over the course of several weeks. In these cases, two of the resulting pieces had portions of the foot and were still attached to the rock substrate, but the others lacked any foot tissue (or mouth). These footless, mouthless fragments drifted until coming to rest in a location with low water flow, where they soon attached and developed into complete polyps.