The word nudibranch comes from the Latin words nudus (naked) and brankhia (gills). There are thousands of different species of nudibranch in thousands of different colors and shapes and you will find them in almost every ocean all around the globe! The opalescent nudibranch or Hermissenda crassicornis is one of many species of often brightly colored sea slugs that live here in the Puget sound. They are gastropods of the phylum Mollusca. This particular nudibranch lives in waters from Alaska down to northern California, this creature can inhabit any different habitats including inter tidal zones of rock shores, bays, and estuaries.
Opalescent nudibranchs can grow to be around 3 inches long and are easily recognizable by their bright orange tipped cerata (the feathery finger like projections on their back that contain stinging cells) , an orange stripe on their head and there blue white “opalescent” body which is where they get their name. Nudibranchs generally feed on hydroids, sea squirts and sea anemones by cruising over colonies and biting off polyps. These nudibranchs recycle the stinging cells from its prey to arm itself by transferring them into the tips of there cerata also known as cnidosacs. They use there tentacle like projections to sense and smell food and other nudibranchs, and as they can only see light and dark they also use those tentacles to sense their surroundings. Biologist believe that this creature uses its bright colors to warn other animals that might harm it of its stinging power.
Nudibranchs are aggressive fighters, often when challenged they will begin biting one another and when one bites the tail of another they win the fight and will often eat their losing opponent! Nudibranchs are hermaphrodites meaning they have both male and female sexual organs, they only live for a year so finding a mate is a high priority. Once they mate they lay tiny white eggs that connect to each other much like links of sausage and attach then to pieces of eel grass and algae.
Because nudibranchs tend to live along rocky shorelines they are often exposed to water-borne pollution which can be easily minimalized and even eliminated by properly disposing hazardous and harmful materials.