The Xenia Mimic
Phyllodesmium jakobsenae (Burghardt & Wägele, 2004) is one of the most convincingly camouflaged nudibranchs at our macro dive sites in Romblon, Philippines. It feeds exclusively on Xenia soft coral and mimics it almost perfectly. Its cerata match the shape and colour of Xenia polyps. As a result, it is nearly invisible on the colony. It belongs to the order Nudibranchia, suborder Aeolidina, family Myrrhinidae. Furthermore, it is solar powered — retaining Xenia‘s zooxanthellae in unique sac-like structures in its cerata. You can find it on iNaturalist.
Solar Power & Camouflage Combined
The zooxanthellae in this species are stored in sac-like terminal structures on the flattened, light-facing side of each ceras. This unique arrangement maximises sunlight absorption. Consequently, Phyllodesmium jakobsenae generates energy from photosynthesis while simultaneously being camouflaged as part of its coral home. Its close relatives Phyllodesmium longicirrum and Phyllodesmium colemani are also documented in our Marine Life Encyclopedia. In contrast to those species, however, this nudibranch targets Xenia rather than Sarcophyton or organ pipe coral.
Finding It at Sunset Cove
At Sunset Cove Beach & Dive Resort, our guides search Xenia soft coral colonies carefully at 5 to 15 metres depth. The animal sits completely still and blends with the pulsing polyps. Therefore, finding it requires patience and a very close look. For underwater macro photographers in Romblon, the camouflage story makes this species one of the most compelling subjects possible. Consequently, a well-composed shot showing the nudibranch against the matching coral background is one of the most striking images from our dive sites.