Hermissenda crassicornis
PREPARED BY: RANA BROWN
TAXONOMY:
Phylum: Mollusca
Class: Cephalopodia
Order: Opisthobranch
Family: Nudibranchia
Genus: Hermissenda
Species: crassicornis
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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.
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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).
SIZE: Hermissenda crassicornis may be considered a smaller
nudibranch reaching only approximately 50mm in length.
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.
FOR MORE
INFORMATION ON HERMISSENDA CRASSICORNIS
SEE THE LINK BELOW TO THE SEA SLUG FORUM, RAN BY DR. BILL RUDMAN.
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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.