Blue-purple fish in a loose cloud off a wall, all facing into the current, feeding on nothing a diver can see. This is the triggerfish that gave up the family trade: instead of crunching shells it picks plankton out of moving water, which is why it is always where the current is.
The teeth are still red. Bright red against the blue face, and visible at a meter - a leftover from an ancestry of hard-shelled food, kept by a fish that now eats copepods.
It keeps the family's other invention too. The first dorsal spine locks upright and is held there by a second small spine behind it, like a latch; a fish wedged into a crevice with that spine up cannot be pulled out until it releases the lock itself. Every triggerfish sleeps this way, and this one bolts into a hole and locks in at the first sign of trouble.
Unlike its titan and yellowmargin relatives, it is harmless to divers - no nest to defend on open reef, no interest in anything larger than a copepod. Fifty centimeters (20 in) at most, and one of the most reliable sights on any current-swept corner.
The genus. Odonus Gistel 1848 - odon (tooth). ETYFish
The species. Odonus niger (Rüppell 1836) - black. ETYFish
- deep blue-purple body with a pale line across the head
- long trailing tips on the tail lobes
- red teeth, visible at close range
- in loose clouds of dozens facing into the current
- length up to 50 cm
Why it's threatened
There are no known major threats.
Threat classification from the IUCN Red List.
