City of Edmonds - Washington

Sea Slugs

Nudibranchs, or 'sea slugs', display a variety of colors and patterns, allowing some them to match their environment closely. The nudibranch has a shell early in its life, which is soon lost. It has few predators. Many have chemical defenses or discharge stinging cells (nematocysts). All nudibranchs have a pair of projections near the head called rhinophores, which help them detect chemicals in the water, some of which can lead to a food source.

Opalescent nudibranch

Hermissenda crassicornis

Description: Colorful mollusk without a shell. Most species absorb oxygen through unusual appendages, called cerata, that grow from their back. Body translucent white with cerata tipped with orange.Two white smell-sensing rhinophores extend from the head. Found in eelgrass beds and rocky beaches. Look for this animal on the undersides of older moon snail sand collars. Length up to 2 in (5 cm).

Food: Omnivorous

Reproduction: Most are hermaphrodites, having both male and female reproductive organs. Eggs are deposited in ribbon-like clusters.

Fun facts: This species has mouth parts adapted to separate the different layers of a moon snail sand collar so it can feast on the tiny eggs.

Shaggy mouse nudibranch

Aeolidea papillosa

Description: Colorful mollusk without a shell. Most species absorb oxygen through unusual appendages, called cerata, that grow from their back. Gray-brown body with numerous cerata. Found on rocks, pilings, eelgrass beds, and mudflats. Length up to 2.5 in (6 cm).

Food: This sea slug eats the tentacles of sea anemones.

Reproduction: Most are hermaphrodites, having both male and female reproductive organs. Eggs are deposited in ribbon-like clusters.

Fun Facts: Immune to the anemone sting, this species can consume 100 percent of its body mass per day. This species is found worldwide.

frosted nudibranch

Dirona albolineata

Description: Colorful mollusk without a shell. Most species absorb oxygen through unusual appendages, called cerata, that grow from their back. Opaque with leaf-like cerata edged in brilliant white. Length normally about to 1.5 in (4 cm), but can grow to 7 in (18 cm).

Food: Feeds primarily on small snails which it breaks open with its small teeth.

Reproduction: Most are hermaphrodites, having both male and female reproductive organs. Eggs are deposited in ribbon-like clusters.

Fun Facts: This species is also found in Japan and Russia.

brown-striped nudibranch

Armina californica

Description: Colorful mollusk without a shell. Lacks cerata. Instead has gill-like structures under a flap along its margins. Flattened leaf-shaped body with thin brown and white stripes. Length up to 3 in (8 cm).

Food: Feeds on orange sea pens.

Reproduction: Most are hermaphrodites, having both male and female reproductive organs. Eggs are deposited in ribbon-like clusters.

Fun Facts: This sea slug is most commonly found out on the sandy tidal flats at a very low tide.

barnacle-eating dorid

Onchidoris bilamellata

Description: Color is a mixture of browns and cream. Blunt-tipped projections cover entire body. Simple gills form a broad horseshoe. Up to 1 in (2 cm) long. Found on rocks or attached to clumps of seaweeds or feather duster tubeworms.

Food: Barnacles are the only food of the adults. This nudibranch sucks out the barnacle's body contents with a special pumping mechanism.

Reproduction: Individuals come together in large groups to mate and lay eggs in shallow water.

Fun Facts: This dorid is found on both sides of the Atlantic coast also.

Sea lemon

Doris montereyensis

Description: Colorful mollusk without a shell. Lacks cerata. Oval; pale to deep yellow with brown spots on back. A pair of pointy rhinophores at the front end, and a frilly gill cluster at the rear. Found on rocks and pilings, anywhere encrusting sponges may be found. Length up to 2 in (5 cm).

Food: Feeds on a variety of encrusting sponges.

Reproduction: Most are hermaphrodites, having both male and female reproductive organs. Eggs are deposited in ribbon-like clusters.

Fun Facts: This species has a citrus or fruity smell which may help it repel intruders.