Horned Nudibranch: A Colorful Sea Slug of the Pacific Ocean

The horned nudibranch is a colorful sea slug that inhabits the Pacific ocean. These slugs are primarily found from southern Alaska to California. Horned nudibranchs are part of a group of sea slugs called aeolids. Aeolid nudibranchs are covered with frilly tentacle-like cerata. The cerata help them breathe, and defend them from predators. Horned nudibranchs can feed on stinging animals like anemones and hydroids. Like other aeolids, they can collect and store the stinging cells from the animals they consume. The cells pass through the nudibranch's digestive

system without harm and get stored in the tips of the cerata. Horned nudibranchs typically have a milky colored body. There are electric blue lines down each side of the big tentacles on their head. An orange line originates from the head region and trails toward their middle with electric blue edges. Their body tapers to a fine point. Their cerata vary in coloration from translucent white to orange, with a notable white central core and a bright orange tip. On top of their head is a pair of sensory organs called rhinophores that serve to help detect smells in their environment.

Horned nudibranchs mainly feed on hydroids and small anemones, but they will also eat a variety of other small organisms. They are found from the low intertidal zone to depths of about 122 ft (37 m). They may be found on rocks, mudflats, pilings, and in tidepools. They can grow to about 3.25 in (8.3 cm) long, but they are usually much smaller in tidepools. Horned nudibranchs can be easily mistaken for a similar species that also lives along the Pacific coast, called the southern opalescent nudibranch (Hermissenda opalescens). However, unlike the horned nudibranch, this

species does not have white lines on their cerata. Horned nudibranchs are known for their aggressive nature, both to other horned nudibranchs and to other sea slug species. Biting and lunging among individuals is normal, especially during the mating season. Like other nudibranchs, they are simultaneous hermaphrodites, possessing both male and female reproductive organs. They lay eggs in clusters attached to rocks, algae, or eelgrass. For more marine facts, click the SUBSCRIBE button!