Dendronotus iris
From ize2010
Dendronotus iris, also known as Dendronotus giganteus, The Giant Nudibranch, The Rainbow nudibranch, or The swimming nudibranch, is one of the largest in the order of nudibranch, which are also refured to as "sea slugs", though not all sea slugs are nudibranchs. Dengronotus iris can reach up to 30 cm long but usually averages around 6-10 cm. These nudibrachs have an amazing ability to swim away if threatened by bringing its foot together down the midline and then swaying its body to launch itself into the current.
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Taxonomy
Kingdom: Animalia. Phylum: Molluska. Class: Gastropoda. Order: Nudibranchia. Suborder: Dendronotacea. Family: Dendronotidae.
Description and Anatomy
These nudibranchs are highly variable in color. They are usually salmon-red or purple can be many other colors as well, from translucent white or grey to orange and yellow. A distinctive feature of D. iris is the white line that surrounds the edge of their foot, although this can be less obvious in some organisms. Another distinctive feature of this species is the vertical row of 3-6 branched projections off the posterior side of their rhinophores. This species possesses two rows of cerata that are arranged in longitudally down the dorsal side of the organism. These are the their gill structures. The gut reaches into the most anterior pair of cerata. The cerata resemble the rhinohpores, although the rhinophores are a little larger. Both the rhinophores and the cerata projections can be tipped with the color red, yellow, orange, purple, or white. The cerata have toxins in them and if the organism is being pursued and cannot get away by swimming, the predator might get a taste of these toxins. The cerata can be regenerated in such circumstances. D. iris has an oral veil that has four pairs of oral papillae. The anus of this species can be found on their right side (a trait of the family Dendronotida, to which this species belongs)of the body between the first and second set of dorsal cerata.
Habitat and Geographical Range
Dendronotus iris can be found on the west cost of North America from northern Alaska northern Mexico. They are mostly benthic, living on the sea floor. Sometimes they can be found on floats, pilings, or rocks and logs at low tide. They rarely exceed the depth of 200 meters and are mostly subtidal. D. iris usually comes up to shallower waters to mate in July and August.
Diet and Feeding Behavior
D. iris feeds mostly on tube anemones, as well has hydroids, nemateran worms, and scyphistomae form of jellyfish. They use chemophores to find their prey. Once the prey is located they rear up and using the radula found in the buccal bulb on their anterior, the nudibranch attaches to the prey and bites of the tentacles. Often, when hunting tube anemones, the nudibranch gets sucked partially or entirely into the tube when the anemone attempts to withdraw from the nudibranch. This does not usually harm either individual and the anemone eventualy succumbs to the nudibranch. Anemones usually live after nudibranch attacks, just missing some tentacles which it regenerates. D. iris has even been observed returning to the same anemone. Because D. iris is feeding on the tentacles, it retains the toxins in them. This makes the nudibranch toxic to many predators. 
Reproduction
Like all nudibranchs, D. iris are simultaneous hermaphrodites (meaning that they possess both male and female sex organs). This is advantageous to them because it increases the probability of finding a mate and of sucsessful reproduction. Their sexual organs are located on the right side behind their head. To copulate, they face opposite directions with their right sides touching each other. The individuals pass each other sperm sacs through a tube called the copulatory apparatus. They then go seperate ways and 1-6 egg masses which contain millions of eggs in gelainous counterclockwise spiral called spawns. These are usually laid next to or on tube anemones (as seen in picture). This provides protection for the spawn and food for the juveniles when they hatch. The spawns themself aslo provide a chemical defense for the eggs and the parent takes no part in raising the young. The eggs usually hatch after 30-45 days. Juvenile nudibranchs are called veligers. 
Refrences
- The Sea Slug Forum
- Intertidal Marine Invertebrates of the Puget Sound
- Emerald Sea
- Dive- Oz
- [1]
- Kohn, A. 1961. Chemoreception in Gastropod Molluscs. American Zoologist 1: 291-308.
- Fuhrman, f., Geraldine J., F and K DeRiemer. 1979. Toxicity and Pharmacology of Extracts from Dorid Nudibranchs. Biological Bulletin 156: 289-299.
