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Peltodoris nobilis - Sea lemon

Geographic range:
West Coast of North America, from Alaska to Baja California.

Key features:
The animal uses a chemical defense system, by producing toxic compounds, which it stores in specialized skin glands. Predators scorn the sea lemons penetrating fruity odor, and acidic taste. Nudibranchs' bright colors are usually a warning sign to potential preda-tors: eat me at your own risk. Observers have witnessed fish spit out nudibranchs that were accidentally ingested. This could be an evolutionary response descended from ance-stral shelled mollusks that feed on sponges, which developed a tolerance to their quills and chemical deterrents and store them for use in their own defense. The new chemical defense may have given the mollusk its ability to later shed its shell, through the course of further evolution.

Similar species:
Doris montereyensis -- Monterey doris Doriopsilla albopunctata -- Salted dorid

exposed rocky shore, kelp forest, protected rocky shore
Peltodoris nobilis - Sea lemon image


Primary common name:
Sea lemon
  ITIS code:
Synonymous name(s):
Diaulula nobilis, Anisodoris nobiis
General grouping:
Nudibranchs or sea slugs

Geographic Range
Range description:
This species ranges from Alaska, to Islas Coronados, Baja California. Common intertidally in north end of range, subtidally in the south end.
Northern latitude extent:
  Southern latitude extent:
East longitude extent:
  West longitude extent:

Intertidal Height
Lowest intertidal height:
0 meters OR 0 feet
  Highest intertidal height:
-0.6006006 meters OR -2 feet
Intertidal height notes:
Low intertidal and deeper tidepools.

Subtidal Depth Range
Minimum depth:
0 meters OR 0 feet
  Maximum depth:
230 meters OR 70 feet
Subtidal depth notes:

exposed rocky shore, kelp forest, protected rocky shore
Habitat notes:
The sea lemon can be found at depths of up to 230 meters, on pilings, around docks, and in shady areas on rocks below the low tide line.

Relative abundance:
Where laminarians or other algae provide the least bit of shelter, the sea lemon, one of the largest nudibranchs, may be commonly found. The sea lemon is common on pilings, such as in the Monterey Harbor.

Species Description
General description:
The Sea Lemon Peltodoris nobilis, is a bright yellow nudibranch with a white gill-plume, sometimes spotted with light brown or orange. They have background splotches of dark brown or black, and the knoblike tubercle that cover the back are yel-low. Antennae (sensory organs) are comb-like, and short, with a ring of 6 frilly white gills on the back near the rear end. Similarly to some other dorid nudibranchs, especially the yellow ones, Anisodoris has a lemony, persistent, and penetrating odor. This elongate oval nudibranch is one of the largest on the Pacific Coast. Its average length is around 10 cm, but can reach lengths of up to 26 cm, and widths of 7.6 cm.
Distinctive features:
The sea lemon, when handled, gives off a pungent fruity or lemony smell which is a chemical defense against predators.
Length: up to 26 cm (10 in.) Width: up to 7.6 cm (3 in.)

Natural History
General natural history:
This species used to be placed in the genus Anisodoris and was known for a long time as Anisodoris nobilis. Subsequently it was known as Diaulula nobilis. The nudibranch's bright yellow color is due to the carotenoid pigment carotene, which occurs in many sponges. Nudibranchs in general live for up to one year. Sea lemons breathe through their rosette of gill the back, nudibranchs that have this type of gill arrangement are in a family called dorids. The family name dorid, refers to the Greek mythological character Doris, whose name represents the bounty of the sea. The common name sea lemon probably comes from this animal's similarity in visual appearance to a lemon based on such qualities as the rough-ened skin, the oval form when seen from above, and the common but not inevitable orange to pale yellow coloration. When handled out of the water, the sea lemon also pro-duces a lemon like odor. The name of the class gastrapoda, means stomach (or muscular) foot, used in locomotion, such as slithering across rocks and sponges. The clade name "nudibranch" comes from the Latin word nudus, meaning naked, and the Greek brankhia, meaning gills. Nudibranchs are often called "sea slugs", which is a misnomer. This has led people to assume that every sea slug is a nudibranch. Nudibranchs are extremely numerous in terms of species, and often very attractive and noticeable, but there is a wide variety of other forms of sea slugs, which belong to several taxonomic groups, not closely related to nu-dibranchs. A number of these other sea slugs are quite colorful, and are sometimes con-fused with nudibranchs. Nudibranchs lack a mantle cavity. They have simple eyes, and are and able to see little more than simple light and dark. Eyes are set into the body, are about a quarter of a mil-limeter in diameter, and consist of five photoreceptors forming a lens. Nudibranchs have cephalic (head) tentacles, which are sensitive to touch, taste, and smell, and club shaped rhinophores to detect odors, but gastropods have no hearing.
Like other nudibranchs, they have few or no predators because of their foul taste, but might occasionally become a meal to fish or other nudibranchs.
The sea lemon primarily feeds on a wide variety of sponges. They also occasionally feed on dead organic matter (detritus), bryozoans, tunicates, other nudibranchs.

Feeding behavior
Feeding behavior(s):
Feeding behavior notes:
This species does not have a radula, yet it feeds on several species of sponges. Its favorite prey is the breadcrumb sponge. A nudibranch's color often matches the color of the sponge it eats.The animal first macerates its food and then sucks out soft tissue, apparent-ly avoiding the sponge spicules, which have not been found in its gut. Studies of sea lem-ons in Pacific Grove, show that individual nudibranchs are quite conservative in their food habits, and they tend to keep on eating the same food species, even if they are trans-ferred to other sites.
November - March  
A sea lemon, like all nudibranchs, can produce both sperm and eggs (it's hermaphroditic), who mutually copulate. Since nudibranchs live for only about one year, their ability to mate with other nudibranchs increases their chances of reproducing. Females lay circular, elaborate, light yellow ribbons containing as many as 2,000,000 eggs; only 99% of the resulting larvae survive. The ribbon is attached in a coil by one edge to a hard substrate. Egg masses exposed to the light have higher mortality rates. Eggs hatch in 20-25 days, trochophore larvae settle within about 2 hours of hatching. In the Monterey Bay, the typical spawning season is from November to March.

Cordell Bank National Marine Sanctuary:
Gulf of Farallones National Marine Sanctuary:
Monterey Bay National Marine Sanctuary:
The sea lemon is widely used in neurophysiological research, because they have large cell bodies in their neurons. Single brain cells and neurotransmitters can be studied, such as receptors for serotonin, dopamine, nitric oxide etc. Sea lemons are abundant now, and should stay abundant if we protect their ecosystem. The sea lemon is currently not on the IUCN Red list of threatened species.
Listing Status:
Monitoring Trends:
Carlton, J.T. 2007.
The Light and Smith Manual, 4th edition
Intertidal Invertebrates from Central California to Oregon
University of California Press. 1001 p.

Langstroth, L. and L. Langstroth. 2000. A Living Bay: The Underwater World of Monterey Bay. University of California Press, Berkeley and Los Angeles, CA. 287 p.

Meinkoth, N.A. 1998. National Audubon Society Field Guide to North American Seashore Creatures. A.A. Knopf, New York, NY. 813 p.

Morris, R.H., D.P Abbott, and E.C. Haderlie. 1980. Intertidal Invertebrates of California. Stanford University Press, Stanford, California. 690 p.

Ricketts, E. F., J. Calvin, and J.W. Hedgpeth. 1985. Between Pacific tides. Stanford University Press, Stanford, CA. 652 p.

Data supplied by SIMoN Sanctuary Integrated Monitoring Network
Anthopleura xanthogrammica - Giant green anemone

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