Sargocentron diadema belongs to the order of Beryciformes (Sawbellies) and family of Holocentridae (Squirrelfishes, Soldier-fishes), it is commonly known as the Crown squirrelfish, or Crowned squirrelfish, in Mauritius it is called the Lion parasol.
The Crown squirrelfish is red in colour with thin white silvery lateral stripes over its body. The head is red with two vertical white streaks on the operculum, one on the edge and the other oblique below the eye. A third line extends along the upper lip and below the large eye. There is a distinctive reddish-black to black dorsal fin with two white streaks. It has a total of 11 dorsal spines, 12 to 14 dorsal soft rays, 4 anal spines and 8 to 9 anal soft rays.
This species is present in the Indo-Pacific region. Its recorded depth range is between 1 to 60m. Sargocentron diadema is benthopelagic, that is, it can be found near the sea floor as well as in the water column or near the water surface. It dwells in caves, shallow coral reefs, lagoons and seaward reefs. During the day, it is often found in coral reef caves and crevices.
At night, it feeds on crabs, polychaetes, small clams and other crustaceans. It is oviparous and its eggs and larvae are planktonic.
According to the IUCN Red list, this species is categorized as being of ‘Least Concern’ as it is common and widespread with no major threats. It does not hold much value to commercial or subsistence fisheries because of its small size. Although it is collected for the aquarium trade, there is no documented decline in its abundance. No conservation measures are in place for this species, but it is present in many MPAs within its range.
This species can reach a maximum length of 17cm.