Black Sea Rod
Plexaura homomalla
Knotted Fan Coral
Melithaea ochracea
About
The bright red and orange fans that light up a torch beam on Indo-Pacific walls and muck sites. The branches are visibly knobbly, which is where the name comes from.
Also known as: Melithaea, knotted fan coral, red spongy coral, red sea fan, gorgonian, sea fan
- Length
- 1 m
- Depth
- 5–30 m
How to tell it apart
A red, orange or yellow branching fan with visibly knotted, beaded branches and contrasting polyp cups. The genus is straightforward underwater; species within Melithaea are not reliably separable by eye.
Appearance
A tree-like fan, typically around 20 cm but sometimes spreading over a metre across. Colours run through yellow, orange, red and white, often with the polyp cups in a contrasting colour to the branches. Swollen nodes give the branches a knotted, beaded look.
Habitat
Indo-Pacific coral reefs, best known from Indonesia and the South China Sea, from just below the low tide mark down to around 50 m and deeper on the shelf. Shallow colonies grow larger, with yellow branches and red cups; deeper ones are smaller with other colour combinations.
Behaviour
Grows on walls, overhangs and jetty pilings, usually oriented across the current. It is azooxanthellate, carrying no symbiotic algae, so it is entirely dependent on plankton and just as happy in shade as in the light.
Diet
Zooplankton and suspended organic particles caught by the polyps.
Breeding
Broadcast spawning into the water column, with larvae settling on hard substrate. Colonies also spread when broken fragments reattach.
Conservation
Not formally assessed. Collected for the aquarium and curio trade in parts of its range, and vulnerable to sedimentation and physical damage on shallow coastal reefs.
Did you know?
The colour has nothing to do with sunlight, because this coral carries no algae at all. Anything red at depth is invisible without a torch, so these fans read as dull grey on a dive and blaze red only when you light them.
Log it in Into the Blue
Describe what you saw and we name it, then keep every species you find in your Oceandex.
