Re: what's the difference between a Simple sponge and Sea Annemone

Hello Diontae,

It turns out that there are many differences between sponges and sea anemones. These animals are so unlike each other that each belongs in its own major group. We biologists call these major groups "phyla" (the singular version is "phylum") – animals in different phyla are about as distantly related as you can get.

Sponges are members of the Phylum Porifera, which means "pore bearer." They make a living by pumping seawater through the many pores in their bodies and filtering out the particles, which they then eat. Sponges are Mother Nature's filterers extraordinaire; some sponges can filter up to 1200 times their body volume every day! A sponge's body is made up of loosely aggregated cells that aren't really connected to each other. In fact, there are some sponges that can be pushed through mesh to separate the individual cells, and after a while the cells start coming together to re-form the sponge's body. There aren't any "real" animals that can do that!

Sea anemones belong to the Phylum Cnidaria. The cnidarians (anemones, corals, jellies, etc.) take their name from the specialized stinging cell that they, and ONLY they have. This cell is called a cnidocyte and contains a capsule called a nematocyst. The nematocyst is the business end of a cnidarian, and is used both for defense and for food capture. Some cnidarian stings can be extremely painful, or even fatal, to humans, but many cnidarians have nematocysts that don't penetrate human skin. Still, you should approach with caution any cnidarian that you come across, unless you know for certain that it is one of the harmless ones.

Cnidarians, including anemones, catch food by trailing or hanging tentacles in the water. The tentacles are loaded with cnidocytes and zap small animals that blunder into them. So these animals are active hunters preying on other animals (some cnidarians can even catch and eat fish!), compared to the sponges that make do with whatever particles happen to be in the water they filter.

I hope this answers your question. For more information about both of these animals, check out the following pages from the University of California Museum of Paleontology:

Phylum Porifera
Phylum Cnidaria

Allison J. Gong
MAD Scientist