The Giant Barrel Sponge (Xestospongia muta) dominates Caribbean coral reef communities, where it is an important spatial competitor, increases habitat complexity, and filters seawater. Average densities of approximately 0.2 individuals per square meter are typical. This sponge has been called the "redwood of the reef" because of its size (often greater than a meter in height and diameter) and its presumed long life. (McMurray et al. 2008)
McMurray et al. (2008) reported on a multi-year study of these sponges in the Florida Keys (U.S.A.). They found that growth rates were variable and decreased with increasing size. The mean specific growth rate was 0.52 per year, but sponges grew as fast or slow as 404% or 2% year. Based on their modeling, the largest sponge in their study was estimated to be 127 years old. Although age extrapolations for very large sponges are subject to more error, McMurray et al. suggest that the largest X. muta present on Caribbean reefs may be in excess of 2,300 years old, which would rank them among the longest-lived animals on earth.
Tissues of X. muta contain Synechococcus cyanobacteria, but it appears that these symbionts are commensals that provide no clear advantage to their sponge host (López-Legentil et al. 2008).
These sponges are vulnerable to a disease syndrome affecting large coral reef sponges known as "sponge orange band’’ (SOB), which generally results in the death of the individuals on which it is observed (McMurray et al. 2008 and references therein).
Synchronous broadcast spawning of male and female Xestospongia muta has been observed (and photographed) in Belize, but the factors triggering and controlling spawning in this species remains unknown (Ritson-Williams 2005).
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