Dorsal spines (total): 8; Dorsal soft rays (total): 9; Anal spines: 1; Anal soft rays: 7. Diagnosis: Pectoral rays 16 (rarely 15 or 17). Gill rakers 6-7 + 22-26 (total 29-33). Body depth 3.25-3.8 in SL (body deeper with growth); head length (HL) 2.85-3.1 in SL; snout long, its length 1.61.8 in HL; eye small, the orbit diameter 5.3-8.95 in HL (SL 118-392 mm); barbels very long, 1.15 in HL to longer than head; longest dorsal spine 1.5-1.7 in HL; penultimate dorsal ray 1.1-1.2 in length of last dorsal ray; pectoral-fin length 1.5-1.7 in HL; pelvic-fin length 1.35-1.55 in HL. Color of large adults yellowish gray, the edges of the scales bright blue except ventrally, the edges more broadly blue posteriorly; a large, hemispherical, saddle-like, yellow spot covering most of upper half of caudal peduncle; region around eye yellow with radiating short narrow blue bands; caudal fin with longitudinal blue bands; second dorsal and anal fins with narrow oblique blue bands; a second smaller color phase entirely yellow, the dorsal peduncular spot sometimes apparent by being brighter yellow than rest of body.
It occurs solitarily or in groups, in all areas of the coral reefs and detrital bottom area from 1 to 95 m deep. It uses its barbels to probe holes and force out prey.
Feed primarily on small fishes, crustaceans, peanut worms, shrimps, crabs, octopi, and small gastropods during the day.
There are no species-specific conservation measures in place for P. cyclostomus. It occurs in marine protected areas in some parts of its range.
Used in aquarium trade.
As of 2008, fifteen percent of the world’s coral reefs were considered under imminent threat of being “Effectively Lost” (with 90% of the corals lost and unlikely to recover soon), with regions in East Africa, South and South-east Asia, and the wider Caribbean being the most highly threatened (Wilkinson 2008). Of 704 zooxanthellate reef-building coral species which were assessed by using the International Union for Conservation of Nature Red List Criteria, 32.8% are in categories with elevated risk of extinction (Carpenter et al. 2008).