Most corals live in colonies. In some species, the individual animals conjoin themselves in a single mass:
While others live as collections of separate polyps joined at the bases.
Palythoas (like the coral pictured above) and zoanthid species are among the types that live as separate, conjoined polyps.
The colonies normally spread by forming new polyps around the outside edges of the existing colony mass. The colony gets larger and wider over time, until the polyps form a bushy-looking cluster like the brown and teal ones in the photo.
But not always.
Like many other coral species, a palythoa polyp is an individual animal, and capable of living apart from the colony. Once in a while, a polyp decides the colony has become too claustrophobic and “decides” to set off to found a brand-new colony of its own.
A couple of months ago, I noticed one of my palythoas seemed taller than the others. Six weeks later, I realized the coral had separated itself from the group and started a slow-motion march up the glass at the back of the tank.
In the two weeks since, the coral has moved about 1/4″ – a pace that makes a snail look like an Indy 500 winner. It’s also started putting out a bump at its base (visible below – look for the little bump on the right side of the coral’s base) that’s the start of a second polyp, though whether this means the coral has decided to found a new colony there (mere inches from the former one) remains to be seen.
It’s unusual to see a coral just “up and go” from its colony without any visible stimulus for the departure. Given that, I thought I’d share the unusual story of this rugged individualist of the reef.
Have you ever seen a coral leave its colony? Do you think I should leave this one where it is or move it to another rock (or another tank)? I’d love to hear your thoughts in the comments!