Encyclopedia

Chelidonura varians   A sleek, midnight-blue hunter of the sand, this sea slug wears neon-blue stripes like glowing racing lines along its body. Its head fans out into a distinctive hammer shape, with two broad lobes that give it a futuristic silhouette. Quick and purposeful, it zips across sandy reef floors in search of tiny flatworms, looking almost like a streak of living electricity as it glides effortlessly over the seafloor.  Size: Up to 70 mm Range: Tropical Indo-West Pacific Habitat / Depth: Shallow reef areas with sandy or muddy bottoms, typically up to 30 m depth Diet: Feeds on...

Sagaminopteron psychedelicum   A truly eye-catching species, this tiny sea slug looks like a living kaleidoscope. Its translucent body is splashed with a vibrant maze of orange, yellow, and black patterns edged in electric blue. With its wing-like parapodia folded back and fluttering as it moves, it appears to “fly” across the reef—hence its nickname, the batwing slug. Size: Up to 10 mm Range: Indo-Pacific; from the Mascarenes and Seychelles to the Philippines and Fiji Habitat / Depth: Sandy and silty bottoms of coral reefs, often near algae and rubble patches, at depths of 1–15 m

Phyllidia varicosa   This large nudibranch looks like a reef adorned with scrambled eggs—its elongated, ridged body is slate-gray to blue, with rows of yellow-tipped tubercles and black separating bands. A bright yellow rhinophore pair adds a pop of color. Its bold, toxic appearance serves as a clear warning: approach with caution, not touch.  Size: Up to 70 mm Range: Widely distributed across the Indo-Pacific, including the Red Sea and Hawaiian Islands Habitat / Depth: Subtidal coral reefs, typically at depths of 10–20 m Diet: Feeds on sponges, using its radula to scrape and consume sponge tissue for nourishment and...

Goniobranchus kuniei   Imagine a creamy sea slug dotted with sky-blue spots, each ringed in a lighter halo, all framed by concentric purple and blue borders — like a delicate little macaron with ornate icing. Usually spotted gliding over coral reef sponge gardens, it’s both elegant and whimsical. Size: Up to 40 mm Range: Western Pacific and eastern Indian Ocean; from Fiji and the Philippines to New Caledonia and Papua New Guinea Habitat / Depth: Coral reefs and rocky outcrops, typically found between 5 and 40 m depth Diet: Primarily feeds on sponges, including Chelonaplysilla violacea, storing their chemical defenses...

Chromodoris quadricolor   This colourful little sea slug looks like it’s dressed for bedtime — long and narrow with bold black and white stripes running down its back, all trimmed with a glowing orange border. Its bright orange “feelers” (rhinophores) and frilly gills make it stand out even more. Easy to spot on reefs, it often hangs around sponges where it feeds and shows off its vibrant “pyjama” look. Size: Up to 50 mm Range: Red Sea and western Indian Ocean Habitat / Depth: Shallow coral reefs and rocky reef areas, from intertidal zones to approximately 30 m depth Diet:...