Phyllodesmium colemani nudibranch organ pipe coral Romblon

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Coleman's Phyllodesmium

Phyllodesmium colemani Rudman, 1991

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A Newly Described Species

Cyerce katiae (Moreno, Gosliner, Wilson, Krug & Valdés, 2025) is one of the rarest butterfly sea slugs at our macro dive sites in Romblon, Philippines. Divers previously called it Cyerce sp. 4 or Cyerce sp. 4 (NSSI2). Scientists formally described it in 2025 as part of a major revision of the genus Cyerce. It belongs to the order Sacoglossa, family Caliphyllidae. Its close relatives Cyerce nigra and Cyerce blackburnae are also documented in our Marine Life Encyclopedia.

How It Defends Itself

Like all Cyerce species, Cyerce katiae has large, flattened, leaf-like cerata. These cerata carry a distinctive honeycomb pattern — hence its former dive community name. When a predator attacks, the animal sheds its cerata. The cerata continue to writhe after separation. As a result, the predator focuses on the moving cerata while the animal escapes. This defence strategy is called ceratal autotomy. Furthermore, the species stores chemical compounds in its body as an additional deterrent.

Finding It at Sunset Cove

At Sunset Cove Beach & Dive Resort, Cyerce katiae holds Epic rarity status. This means only one to three confirmed sightings exist at our dive sites. Our guides search sandy rubble substrate near Udotea algae patches at depth. The animal is small — just 5 to 15 mm. Therefore, it requires maximum magnification and a very slow approach. For underwater macro photographers in Romblon, spotting this species is one of the most exciting possible encounters on any dive.

Taxonomy & Classification

Order	Nudibranchs (Nudibranchia)
Suborder	Aeolidina (Aeolid Nudibranchs)
Family	Myrrhinidae
Subfamily	Phyllodesmiinae
Genus	Phyllodesmium
WoRMS AphiaID	548883
iNaturalist	418427

Described by Rudman (1991) from Lord Howe Island, Australia, named after Neville Coleman. Also documented from the Philippines and central Indo-Pacific. Family listed as Myrrhinidae (WoRMS 2025) — also placed in Facelinidae in older literature. Contains zooxanthellae stored in terminal chamber aggregations across the ceratal wall — a symbiotic photosynthetic relationship providing supplementary energy. Feeds exclusively on Tubipora musica (Organ Pipe Coral).

Morphology

Size	10–18 mm
Colour Variations	Body colour closely matches its prey Tubipora musica — pinkish-red to orange-red cerata with white tips, blending perfectly with the red skeletal tubes of the organ pipe coral. Zooxanthellae stored in aggregations of terminal chambers distributed across the ceratal wall, visible as darker spotting. Body translucent to pale. An extremely well-camouflaged species — almost impossible to spot without knowing exactly what to look for.
Identifying Features	Small — only 10–18 mm. Cerata coloured to match Tubipora musica organ pipe coral. Always found directly on or immediately beside Tubipora colonies. Zooxanthellae visible as clustered chambers in cerata walls. Distinguished from P. longicirrum by much smaller size and specific association with organ pipe coral rather than Sarcophyton. Distinguished from other Phyllodesmium by habitat association and ceratal colouration matching red coral.

Body small and slender, approximately 18mm. Cerata arranged in rows, containing zooxanthellae in aggregations of terminal chambers in the ceratal wall — a more compartmentalised arrangement than P. longicirrum. Rhinophores smooth. Lacks cnidosacs — defence relies on camouflage and chemical deterrents from coral prey. Oral tentacles slender.

Habitat & Ecology

Substrate	coral
Depth Range	2–10 m (most common: 5 m)
Temperature	24–29°C
Primary Prey / Host	Tubipora musica (Organ Pipe Coral, family Tubiporidae)

Activity & Behaviour

Active Time	day, night
Seasonal Presence	Year-round — dependent on presence of Tubipora musica colonies
Egg Ribbon	White, coiled ribbon
Spawning Season	Not yet documented at SSC
Chemical Defence	Present
Aposematic Colouring	Absent
Camouflage Strategy	Exceptional colour match with Tubipora musica organ pipe coral — the pinkish-red cerata are nearly indistinguishable from the red skeletal tubes of the coral colony. One of the most effectively camouflaged nudibranchs in Romblon waters.
Escape Response	Primary defence is camouflage. Remains motionless when threatened. No ceratal autotomy — unlike Cyerce species.

Scientific Literature

Further studies on the taxonomy and biology of the octocoral-feeding genus Phyllodesmium Ehrenberg, 1831 (Nudibranchia: Aeolidoidea)
Rudman, W.B. (1991). Journal of Molluscan Studies 57: 167–203

Literature for divers

Romblon Field Data

Look carefully on and around Tubipora musica organ pipe coral colonies in very shallow water — typically 2 to 5 metres. The cerata match the coral colour almost perfectly. Search the base of coral colonies and between the tubes. Best photographed with the coral colony as background to show the camouflage. A very small species — use maximum magnification. Extremely rewarding subject given the perfect camouflage story.

Frequency	rare
First Sighting	2019-01-01
Max Individuals	3