Fahey & Gosliner, 2001
Known only from Okinawa.
(CASIZ 104720), 17 mm. Photo taken by R. Bolland. (From Fahey & Gosliner, 2001: Fig. 1B).
The ridges and tubercles are quite reduced and differe from most species of Halgerda in being the same translucent white colour as the background colour of the mantle. Another unusual feature is the yellow pigment on the notum is not associated with the ridges but is scattered randomly along the flat midregion of the mantle. Halgerda onna has black lines on both the anterior and posterior sides of the gill branches. The rhinophore club appears to be balck and the stalk white. It is described from a single small animal, 17 mm long found by Bob Bolland. It has also been seen on Guam by Clay Carlson. It is named after the village in Okinawa nearest to where it was found by Bob Bolland.
• Fahey, S.J. & Gosliner, T.M. (2001) The phylogeny of Halgerda (Opisthobranchia, Nudibranchia) with the description of a new species from Okinawa. Zoologica Scripta, 30(3): 199-213.
Rudman, W.B., 2001 (October 10) Halgerda onna Fahey & Gosliner, 2001. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/halgonna