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Sun corals are equipped with ejection seats

By Leonard Ho - Posted Oct 31, 2014 09:00 AM
Polyp bail-out is a phenomenon where a coral's polyps detach from their skeletal base to seek life elsewhere. Only a few species are known to do this. Scientists documented the first known such occurrence for sun corals, Tubastraea coccinea.
Sun corals are equipped with ejection seats

A stressed sun coral colony showing polyps ready to detach from the skeleton

In a few species of corals, polyps can detach from their skeleton and float off to settle elsewhere.  Many reefkeepers have reported polyp bail-out in corals such as Pocillopora, Catalaphyllia (AKA elegance corals), and Euphyllia (hammer, torch, and frogspawn corals).  This form of asexual reproduction is generally regarded as a defensive mechanism triggered by stress, although some corals such as Pocillopora seem to do this even when the parent colony is thriving.

Budding of sun corals is well documented.  Parent colonies will produce tiny planulae and broadcast them into the water.  In fact, Steinhart Aquarium biologists have farmed Tubastraea by collecting budded planulae and growing them into mature colonies.  However, polyp bail-out was not known in Tubastrea "sun corals" until this year when researchers documented the phenomenon in Tubastraea coccinea.

The photo below tracks the seven month development of a sun coral polyp bail-out.  During its early days (photos a-d), x-rays confirmed the coral lacked any hard skeletal structure.  By the sixth and seventh month (photo e-f), the polyp was still alive and attached itself to substrate by secreting a new skeletal base.


Author: Leonard Ho
Location: Southern California

I'm a passionate aquarist of over 30 years, a coral reef lover, and the blog editor for Advanced Aquarist. While aquarium gadgets interest me, it's really livestock (especially fish), artistry of aquariums, and "method behind the madness" processes that captivate my attention.


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