A small pale damselfish with a black-edged dorsal fin, in a tight group inside a branching coral head, and one that lives in this sea and the 🌊 Gulf of Aden and nowhere else.
Six centimeters (2.4 in) makes it the smallest of its genus here, and the size fits the habit: it lives deeper inside the branches than its striped relatives, and it rarely leaves the colony at all. A group of them in a Porites head is effectively a population living in a single organism.
That dependence is total. These fish do not relocate as adults, so a colony that dies takes its residents with it - and the coral benefits in turn from the nutrients they release and the water they keep moving through the branches. Both sides lose when one goes.
Like its relatives it lives in a size-ordered group with one breeding pair, and males guard eggs laid on a cleaned patch at the base of the coral.
The species. Dascyllus marginatus (Rüppell 1829) - margined. ETYFish
- pale yellow-brown body with a black margin along the dorsal fin
- small - the smallest damselfish of its genus here
- in tight groups inside a single coral head
- length up to 6 cm
Why it's threatened
Threat classification from the IUCN Red List.
