How to Identify Harlequin Sweetlips

To identify Harlequin Sweetlips (Plectorhinchus chaetodonoides), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Juveniles are dramatically different from adults. Juveniles (up to ~15 cm) have a white to yellowish body with large, irregular, black to dark brown blotches and spots, often with a few smaller spots on the fins. The fins, especially the dorsal and caudal, are greatly enlarged and undulate, mimicking a toxic flatworm or nudibranch. Adults (over ~20 cm) transition to a pale grey to whitish body covered in numerous small, closely-set black or dark brown spots, which extend onto the fins. The lips are thick and fleshy, often yellowish.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Dramatic ontogenetic color change from juvenile to adult., Thick, fleshy lips., Juveniles mimic flatworms with undulating fins and bold blotches., Adults covered in numerous small, dark spots.

Dorsal fin

Single dorsal fin with 12-14 spines and 18-22 soft rays. In juveniles, the dorsal fin is greatly enlarged and undulates.

Tail fin

Caudal fin is rounded to slightly emarginate. In juveniles, it is also enlarged and undulates.

Pectoral fin

Pectoral fins are moderately sized. In juveniles, they are often dark with light spots.

Distinctive fins

The greatly enlarged and undulating dorsal and caudal fins of juveniles are a key distinguishing feature, used in mimicry.

Identification Tips

1. 1

   Juvenile coloration and fin shape

   Look for the striking white/yellow body with large, irregular black blotches and greatly enlarged, undulating dorsal and caudal fins. This mimicry is unique among sweetlips.

2. 2

   Adult coloration

   Identify adults by their pale grey to whitish body densely covered with numerous small, dark spots, including on the fins. The thick, fleshy lips are also characteristic.

3. 3

   Body shape

   Observe the compressed, deep body shape, typical of many sweetlips species.

4. 4

   Behavior

   Juveniles often exhibit a slow, undulating swimming motion, enhancing their mimicry. Adults are more sedate, often resting during the day and foraging at night.

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