Colonial Tube-sponge

A sponge has no organs at all. No mouth, no gut, no nerves, no muscles, no front end: it is a colony of cells built around plumbing. Water is pulled in through thousands of pinhole pores in the surface, driven along internal canals by chambers of whip-bearing cells, and pushed out through the large vents. Each cell catches its own food, bacteria and particles far too small for anything with a mouth, and a sponge of this size moves many times its own volume of water every hour.

This one grows as a cluster of upright tubes rising from a shared base, each tube ending in a single wide vent at the top, the whole stand reaching about 60 cm (24 in). The surface is finely meshed and soft to the touch, without the rasp of a spicule-stiffened sponge, and the color runs from pale lavender through pink to a purplish brown.

Be honest about identification: most sponges cannot be named from a photograph, because what separates the species is the skeleton, and that means a slide and a microscope. A stand of tubes of this shape and color on a northern 🌊 Red Sea slope is one of the safer calls, but it is still a call.

It is common along reef slopes and walls in the Gulf of Aqaba and the Gulf of Suez, mostly deeper than 5 m and recorded down to about 35 m (115 ft).

An animal that cannot move, hide or bite defends itself chemically, and this species is one of the best studied cases in the sea. It makes sipholane triterpenoids, and one of them, sipholenol A, reverses in cultured tumor cells the pump that those cells use to throw chemotherapy drugs back out, which is why it keeps appearing in cancer research. The chemistry is not even uniform along the coast: sponges from the Gulf of Aqaba and from the Dahlak archipelago carry measurably different mixtures. Older papers file all of this under its former name, Siphonochalina siphonella.