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Facelinella semidecora
(Pease, 1860)
Facelinella semidecora
Maximum size:  16 mm.

Identification:  This species ranges from white to brown in overall appearance depending on the amount of pigment on the body and on the color of the cerata. The body is translucent white with opaque white flecks that can be scattered over the entire animal. There may also be streaks or reticulations of rusty orange on the body, head, rhinophores and cephalic tentacles. The cerata are translucent to clear and are sometimes flecked with white. They are dark at the base where the digestive gland is visible and are tipped with white. In some animals, the cerata have a rust-orange tinge and there is a translucent orange or translucent white subapical band. The rhinophores are tipped with white and typically have several low ridges.

Natural history:  Facelinella semidecora is a moderately common species and one of the more commonly encountered aeolids in Hawaii. It is found under rocks in tide pools and the low intertidal as well as in protected to highly exposed rocky habitats down to 9 m (30 ft). It feeds on hydroids.

Distribution:  Big Island, Maui, Kahoolawe, Oahu, Kauai, Midway and Kure.

Taxonomic notes: This species was described from Hawaii and is sometimes listed as Phidiana semidecora. A similar species, Phidiana anulifera, was described from Japan, and some authors consider the Hawaiian animals to be that species. See the Sea Slug Forum for further discussion. It was first reported from Hawaii in Pease, 1860 (as Aeolis semidecora).
Photo:  CP: 14 mm: Poipu State Park, Kauai; May 4, 2010.

Observations and comments:

Note 1:  ( )
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