Nudibranchs, members of the sea slug family, come in an amazing variety of shapes and colors. Several outstanding specimens were recently placed on exhibit at the Aquarium’s Closer Look table: the opalescent nudibranch, Hermissenda crassicornis; the alabaster or white-lined nudibranch, Dirona albolineata; and the Monterey sea lemon, Doris montereyensis.
Opalescent nudibranchs’ colors are variable but an orange and white strip down the dorsal (back) side is one of their distinguishing features. The pointed projections on their backs are called cerata and, among other things, they contain unfired nematocysts, or stinging cells, that the nudibranch acquired from its prey. When threatened by a kelp crab or other predator, opalescent nudibranchs may release a single cerata or a cluster of them as a defense.
The alabaster or white-lined nudibranch and the bright yellow Monterey sea lemon share a similar diet with the opalescent nudibranch: anemones, cup corals and sea pens. Like all nudibranchs, they use the radula (a band bearing numerous, very small teeth) in their head region to gnaw at their prey.
Come see the new nudibranchs the next time you visit the Seattle Aquarium!