Nudibranchs and Sea Slugs of the Philippines (Part I)

The Philippine Islands are an epicenter of marine biodiversity in the Pacific, including an incredibly diverse community of nudibranchs and sea slugs.  However, like most other members of marine ecological communities, particularly in developing nations suffering poverty and political unrest, nudibranch diversity is threatened and suspected to be in decline in the Philippines.  While we strive to protect these communities, let's also learn a little more about what it is we stand to lose.  

This Tritonia sp. and other members of the family Tritoniidae are specialized predators on soft corals, gorgonians and sea pens.   This Dermatobranchus sp., and others in the genus, belong to a group of nudibranchs called Arminids, which are also predators of soft corals.  Members of the Eubranchidae, like this Eubranchus sp.,  are small aeolid nudibranchs that feed on hydroids...also, note the eggs in this video clip.  Sakuraeolis nungunoides has distinct cerata, the body projections that assist in respiration, digestion and protection.  The volcanic appearance of the base of the gill cluster of Hypselodoris krakatoa inspired the species name of this attractive nudibranch.  Glossodoris averni and other close relatives are the only nudibranchs that vibrate their gills; this may increase their respiratory efficiency.  Some nudibranchs are very impressive mimics of their food sources; this sponge mimic may be a small individual of the very large species Atagema spongiosa ("cf" means "compare with")...or it may be something different, much remains to be learned about nudibranch diversity.  Another example of a sponge mimic is Halgerda dalanghita, seen here on an orange sponge which they prey on and blend into marvelously.  Glossodoris rufomarginata is named for the red margin around the mantle of the body.  "Cerato-" is Latin for "horn", and "soma" means "body"; the genus name of this Ceratosoma gracillimum describes the bodily outgrowths that surround, and may protect, the gills.  While we can't see it, one of the things that separates soft coral feeding Marionia sp. from other nudibranchs is the presence of stomach plates in the digestive tract.

With over 700 species of nudibranchs, >50% of which are not fully described by science, we've only just begun to explore the incredibly diverse nudibranch fauna of the Philippines.  Stay tuned for much more.