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Hermissenda crassicornis
Size:
Hermissenda crassicornis may be considered a smaller nudibranch reaching only approximately 50mm in length.
Identification:
Hermissenda crassicornis is a sea slug commonly found in the Pacific Northwest. It is sometimes referred to as the "opalescent sea slug" due to the reflective white stripe that runs along the sides of the animal's translucent body. Its cerata are usually bright orange, tipped with white, and it also has an opaque blue line that runs along its body, and through to the oral tentacles. Color may vary. It has also been described, or also named as Phidiana crassicornis.
Range:
Hermissenda crassicornis can be found from Kodiak Island, Alaska to Punta Eugenia, Mexico. It can also be found in Baja California, and Japan (Behrens 1991).
Habitat:
This sea slug is most often found on docks and floats. It is abundant on floating buoys among colonies of Metridium senile, an anemone on which it feeds. It is common in marinas such as Boston Harbor Marina in Puget Sound, Olympia, Wa (personal observation). It can also be found on eelgrass beds and on rocky shores.
Reproduction:
Hermissenda crassicornis is like most other sea slugs in that it is hermaphroditic. Reproduction can therefore occur between any two individuals, not requiring the match of a male and female pair. This form of sexual reproduction is highly beneficial to the sustenance of the species considering H. crassicornis has a short lifespan of approximately one year (www.mbayaq.org). It is also of interest to note that H. crassicornis are highly aggressive toward each other and may even be cannibalistic while they fight. This hostile behavior would lead one to assume that their style of mating must involve a tricky introduction.
Diet:
This sea slug eats mainly hydroids, anemones, eggs of other animals, and occasionally each other! This species is considered less picky about its diet (Kozloff 2000).
Defense:
One of the most intriguing facts about H. crassicornis is that it employs a defense strategy by uniquely utilizing the food it consumes. Certain sea anemones and other food types contain nematocyst in their tissues. These are also called stinging cells. When H. crassicornis consumes the animal, it incorporates these cells into its cerata, which are the fleshy structures on its dorsal surface. These aid in prey protection, along with the animal's vivid colors which are thought to deter would be predators.
References:
Kozloff, E. Seashore Life of the Pacific Northwest. (1991). University of Washington Press, Seattle, WA.
Kozloff, E. Marine Invertebrates of the Pacific Northwest. (1999). University of Washington Press, Seattle, WA.
Brusca & Brusca. Invertebrates. (2003). Sinauer Associates, Inc. Sunderland, MA.
Behrens, D. Pacific Coast Nudibranchs (1991). Sea Challengers. Monterey, CA.
Last updated Tuesday, September 05, 2006, by Lisa Ferrier
