How to Identify Harlequin Filefish

To identify Harlequin Filefish (Oxymonacanthus longirostris), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Bright orange or yellow body covered with numerous small, iridescent blue or green spots. The caudal fin is typically yellow with a black ocellus (eyespot) near its base. The snout is often a contrasting color, such as blue or green.

Scale type

placoid

Mouth position

terminal

Distinctive features

Elongated, tubular snout ending in a small, terminal mouth, Two dorsal spines, the first of which is prominent and can be locked upright, Small, rough scales giving a sandpaper-like texture, Large, prominent eyes, Vibrant orange/yellow body with blue/green spots

Dorsal fin

Two dorsal fins; the first consists of two spines, the first spine being long and strong, capable of being locked erect. The second dorsal fin is soft-rayed (29-33 rays).

Tail fin

Rounded to slightly truncate caudal fin (12 rays), typically yellow with a prominent black ocellus.

Pectoral fin

Small and rounded (10-12 rays), positioned high on the body.

Distinctive fins

Pelvic fin reduced to a single spine, often fused to the belly flap, providing stability.

Identification Tips

1. 1

   Coloration and Pattern

   The bright orange or yellow body with numerous iridescent blue or green spots is highly distinctive. The black ocellus on the caudal fin is also a key identifier.

2. 2

   Snout Shape

   Its exceptionally long, tubular snout is a defining characteristic, used for feeding on coral polyps.

3. 3

   Body Shape

   The highly compressed, kite-shaped body, typical of filefish, helps distinguish it from other reef fish.

4. 4

   Behavior

   Often observed hovering near or within Acropora coral colonies, exhibiting a unique, almost 'rocking' swimming motion.

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