The Tree-Like Solar Nudibranch
Phyllodesmium pinnatum (Moore & Gosliner, 2009) is one of the most cryptic solar-powered nudibranchs at our macro dive sites in Romblon, Philippines. Its cerata are elongate, flattened and pinnate — branching like tiny trees. This structure matches octocoral colonies almost perfectly. As a result, it is nearly invisible on its prey. It belongs to the order Nudibranchia, suborder Aeolidina, family Myrrhinidae. Furthermore, its type locality is the Philippines — described from Batangas Province. Find it on iNaturalist.
Solar Power Through Octocoral
Like all Phyllodesmium species, Phyllodesmium pinnatum retains zooxanthellae from its octocoral prey. These algae photosynthesise sunlight and provide the animal with supplementary energy. In contrast to Phyllodesmium longicirrum, which feeds on Sarcophyton, this species targets octocorals of the order Alcyonacea. Its close relatives Phyllodesmium colemani, Phyllodesmium jakobsenae and Phyllodesmium koehleri are also in our Marine Life Encyclopedia. Together they represent five different solar-powered strategies documented at Sunset Cove — the most diverse Phyllodesmium collection documented at any single dive resort in the Philippines.
Finding It at Sunset Cove
At Sunset Cove Beach & Dive Resort, our guides search octocoral colonies carefully at 3 to 25 metres depth. The pinnate cerata match coral branches almost exactly. Therefore, look for slightly irregular branch structure on a colony. Approach very slowly — it sits completely still. For underwater macro photographers in Romblon, the tree-like cerata create extraordinary close-up images. Consequently, finding all five Phyllodesmium at our dive sites is one of the great macro photography challenges at Sunset Cove.