An orange-red cushion with a coarse honeycomb of openings across its surface, growing on shaded rock and under overhangs. It is one of the sponges a diver actually notices here, which is unusual: most are drab, encrusting and easy to mistake for the rock they sit on.
The honeycomb is plumbing. The small pores over the whole surface draw water in; the large openings are the exits, and their raised rims lift the outflow clear of the intake so the animal does not refilter its own waste water. Every sponge solves that problem, and the pattern of holes is the visible half of the solution.
Sponges have no organs, no nerves and no muscles, and they still manage coordinated behavior: a sponge can slowly close its openings and shut down filtration for hours when the water carries too much sediment, and reopen when it clears.
Color comes with a warning. Bright red-orange sponges are typically loaded with defensive compounds - which is why most of them are untouched on a reef where everything else is grazed, and why sponges are one of the richest sources of new pharmaceutical molecules in the sea.
- cushion or cup of orange to red tissue with a coarse honeycomb surface
- large round openings scattered over the surface, each ringed slightly raised
- firm and slightly rough to touch, not slimy
- up to 35 cm across
