The Largest Solar-Powered Nudibranch
Phyllodesmium longicirrum (Bergh, 1905) is the largest aeolid nudibranch in the Indo-Pacific. It grows up to 140 mm. Divers call it the Solar-Powered Nudibranch. It belongs to the order Nudibranchia, suborder Aeolidina, family Myrrhinidae. Furthermore, zooxanthellae live inside its cerata. These algae photosynthesise sunlight and produce energy directly for the animal. As a result, it can go long periods without feeding on its prey coral. Find observations on iNaturalist.
Giant Solar Paddles
The cerata are large and flat — like solar panels. They maximise surface area for photosynthesis. In contrast to most aeolid nudibranchs, this species carries no cnidosacs. Instead, it stores diterpene chemicals from its prey as defence. It feeds on Sarcophyton trocheliophorum soft coral. Its close relatives Phyllodesmium colemani, Phyllodesmium jakobsenae and Phyllodesmium koehleri all appear in our Marine Life Encyclopedia. Together, these four species show the remarkable diversity of solar-powered nudibranchs at Romblon.
Finding It at Sunset Cove
At Sunset Cove Beach & Dive Resort, our guides search Sarcophyton soft coral colonies on sandy rubble at 5 to 30 metres depth. The animal is large and visible from a distance. However, it blends well against the coral. Therefore, check the base and underside of colonies carefully. For underwater macro photographers in Romblon, the enormous flat cerata create outstanding images. Consequently, this species ranks among the most impressive nudibranch photography subjects at our dive sites.