This is the triggerfish that gave up the family trade. Instead of crushing shells it picks plankton out of moving water, which is why you only ever find it where the current runs - a loose cloud of blue-purple fish off a wall, all facing the same way, feeding on nothing a diver can see.
The teeth stayed red. Bright red against a blue face and visible from a meter away, they are a leftover from an ancestry of hard-shelled food, kept by an animal that now eats copepods. Nothing on its menu requires them.
It kept 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, so a fish wedged into a crevice cannot be pulled out until it releases the lock itself. Every triggerfish sleeps that way, and this one bolts into a hole and locks in at the first sign of trouble.
Rueppell described it from this sea in 1836 and called it niger, black - which fits a specimen in a jar of alcohol far better than it fits the living fish, deep blue-purple with a pale line across the head and long trailing tips on the tail.
Unlike its titan and yellowmargin relatives it is no trouble to divers: no crater on open sand to defend, and no interest in anything larger than a copepod.
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 both lobes of the tail
- red teeth, visible at a meter
- hangs in loose clouds of dozens, all facing into the current
- up to 50 cm
Why it's threatened
There are no known major threats.
Threat classification from the IUCN Red List.
