[youtube width=”680″ height=”400″]http://www.youtube.com/watch?v=lcPD1Ajp75k[/youtube]
Most reefers are aware of sweeper tentacles that are large and noticeable in LPS corals, but we don’t think about the reach of SPS corals very much. Galaxea, Scapophyllia, Oulogyra and Euphyllia all have large and long-reaching sweeper tentacles that show no mercy when they come into contact with other corals. Acontia filaments are the SPS equivalent of sweeper tentacles although they are just as unforgiving as LPS corals.
Acontia filaments and sweeper tentacles are two physically very different things – sweeper tentacles are modified tentacles of the coral polyp which are a little or much further reaching, and which usually pack a denser payload of nematocysts than other tentacles. On the other hand Acontial filaments originate from the gastric cavity and these have an even higher density of stinging cells and other digestive nasties to nuke a coral neighbor. Acontia filemants are most often seen in SPS corals and also commonly seen poking out the sides of stressed mushroom anemones, or even through the tissues of LPS corals like Scolymia and Acanthastrea.
If you needed any evidence of how SPS corals keep control of their turf on their reef, this oregon blue tort, Acropora tortuosa, was all too willing to show the camera how reef coral warfare is done. Although acontia filaments may not have quite the same reach as elongated sweeper tentacles of LPS corals, SPS corals grow fast and the source of the acontia filaments as delivered in an axial tip will be an inch closer to its target within a month or so. In this case the Oregon blue tort’s acontia were merely clearing the glass as a substrate to be on but if that had been almost any coral, the tissue would be toast.