The coral calls this fish for help, and the fish comes.
When a strand of toxic seaweed drifts against an Acropora and touches it, the coral releases a chemical signal into the water. Within minutes the gobies living in that colony arrive at the contact point and trim the seaweed away. The experiment that showed this was published in 2012: researchers put the seaweed on corals with gobies and on corals without, and only the occupied colonies got cleaned. Water taken from a damaged coral and squirted onto a healthy one brought the gobies out too, so the signal is chemical and it is specific.
This species eats the seaweed rather than just cutting it, and afterwards its own skin mucus becomes more toxic. It takes the coral's defense problem and turns it into its own defense.
The rest of the arrangement is straightforward: the fish is a poor swimmer, everything eats it, and the coral is the only place it is safe. The coral, for its part, has hired a gardener that never leaves.
The genus. Gobiodon Bleeker 1856 - odon (tooth). ETYFish
- green body crossed by red to violet lines, sometimes broken into spots
- four or five reddish bars across the head
- no scales; blunt head and a steep forehead
- deep inside a branching Acropora colony, alone or in pairs
- up to 3.5 cm
Why it's threatened
Threat classification from the IUCN Red List.
