Nudibranch (Phidiana Crassicornis)
Nudibranchs are marine snails (gastropod molluscs) that have no shell at maturity.
Nudibranch means “naked gills” because their gills are on the rear of the back (posterior dorsal) of some species or along the side covered by a protective flap as these species tend to bury into sand or mud. The gills can be used for identification. Some species “wave” their gills as they move or feed.
Nudibranchs live in marine environments from Antartica to the tropics. Most spend their adult life on the bottom. Glaucus marginata and Glaucus altanticus float around (pelagic) upside down on the ocean surface. They feed on blue bottles or Portuguese man-of-war’s (Physalia physalis) and By-the-wind sailors (Velella velella).Fiona pinnata feeds on goose barnacles that attach to flotsom and jetsom or Velella.
The largest species grow to 40cm, the smallest, microscopic and are easily able to move through grains of sand. Most are smaller than 10cm.
Nudibranchs appear to live for a maximum of one and a half years, depending on food and suitable conditions. At times there will be population explosions and droughts. When food is plentiful the numbers increase, as the food source is consumed or decreases for natural reasons numbers decline. Water temperature and climatic conditions may play a part in their survival chances.
The life style can be categorised as:
1. Nudibranchs that feed upon hydroids, etc., (ephemeral prey) tend to appear several times each year.
2. Those feeding upon sponges live longer, possibly beyond a year.
Nudibranchs are sea slugs belonging to the suborder Nudibranchia, the largest suborder of the order Opisthobranchia. There are more than 3,000 described species.
