Most nudibranchs sport bright colors—sea lemons are deep yellow to burnt orange. Black spots mingle with protruding bumps (tubercles) on the sea lemon's back. Fleshy antennae (sensory organs) and a rosette of gills protrude from the back of a sea lemon's slim, flat body.
Nudibranchs' bright colors are usually a warning—eat me at your own risk—and predators scorn the sea lemon's fruity, penetrating odor and acidic taste. Observers have seen fish spit out accidentally ingested nudibranchs. Nudibranchs do prey on other nudibranchs, however.
To feed, sea lemons use their filelike tongue (radula) to rasp sponges. They usually concentrate on one species of food, a favorite prey is the breadcrumb sponge.
Sea lemons are abundant now and will stay abundant if we protect their ecosystem. The main environmental dangers to sea life like nudibranchs are pollution and habitat destruction. We can help limit pollution by decreasing our use of pesticides, recycling motor oil and keeping other chemicals out of storm drains, rivers and lakes. Whatever goes in these waters eventually finds its way to the ocean.
A sea lemon, like all nudibranchs, is hermaphroditic and can produce both sperm and eggs. Since nudibranchs live only about one year, the ability to mate with any other nudibranch increases their chances of reproducing.
Circular, light yellow ribbons contain as many as 2,000,000 eggs; less than 1% of the resulting larvae survive. In Monterey Bay, the spawning season is from November to March.
Sea lemons breathe through the rosette of gills on their back. Nudibranchs that have this arrangement of gills are in a family called dorids.
Because the neurons of sea lemons are larger and easier to access than human neurons, researchers find sea lemons useful in their studies of nerve cells. In addition, the abundance of sea lemons makes their collection for research feasible.
A nudibranch's color often matches the color of the sponge it eats.