Scientific Name: Chelidonura hirundinina
Common Name: Swallowtail Headshield Slug

Adult Size: 15 – 35 mm
Depth Range: 1 – 20 m; most common in shallow lagoons, sandy patches, and seagrass beds
Biotope / Habitat: Prefers sandy bottoms, algal fields, and coral rubble zones where its prey is abundant. Often seen gliding quickly over the substrate, leaving tiny tracks behind
Diet: Carnivorous; feeds mainly on small flatworms, especially acoel worms. Uses chemoreceptors on its enlarged “headshield” to locate prey and quickly suck them up
Reproduction: Simultaneous hermaphrodite; mates by aligning side-to-side. Lays long, gelatinous strings of tiny eggs on sand, rubble, or algae. The eggs hatch into planktonic larvae before settling
Fun Fact: Its characteristic “swallowtail” shape—notably the two long tail extensions—gives Chelidonura hirundinina its name. This species is surprisingly fast for a sea slug, using its muscular foot and headshield to glide efficiently across the sand while searching for flatworms.

Sleek, active, and beautifully patterned in black, blue, or orange lines, Chelidonura hirundinina is a favourite find for macro lovers. Its elegant swallowtail silhouette and quick movements make it an unforgettable sight on any shallow-water dive.