Giant Barrel Sponge - Xestospongia muta, Phylum Porifera, Class: Sponges Demospongiae3
These spectacular sponges can live to be over 2000 years old! The ones in this photograph are more likely to be less than
100 years (based on the fact that they grow an average of 1/2 an inch a year).
Sponges are filter feeders. Small holes (incurrent pores) draw water into the sponge. It's not the type of eating
that you can witness, but you can find evidence of it during a night dive. By waving your hand near the outside of one of these sponges at night (being very careful NOT to
touch it) the sponge will appear to glow. What you are actually seeing is the bioluminescence of the
water drawn into the sponge.
"Visual ID: Huge barrel-shape with rough, often jagged, stone-hard exterior. Shades of gray, brown, or red-brown.
Generally solitary, but one or two smaller individuals occasionally grown around base."
3Humann, Paul. Reef Creature Identification, Florida Caribbean Bahamas. Ed. Ned DeLoach. Jacksonville, FL: New World Publications, Inc., 1996.
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