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Opisthobranch of the Week Data
Taxonomy:
Halgerda dalanghita is unknown from Okinawa Island as of late-March, 2001, but the close proximity of Okinawa, as well as the similar opisthofauna to that of the Kerama Islands, suggests the possibility that it is also present here on the main island of Okinawa. The above featured, but uncollected animal, is one which was photographed in the waters of Gahi Island, one of a series of islands in the Kerama Islands Group, which are located 30 ~ 40 kilometers west of the Okinawa capitol, Naha. This featured animal was photographed by Atsushi Ono during December of 1999 in the South area of Gahi Island in approximately 10m of water from the underside of dead coral. Atsushi's photograph is used here with his kind permission. It should be noted that Atsushi considers the species to be very rare in the Kerama Islands as he has seen only the above featured two individuals (per. comm.).
Fahey & Gosliner (1999) named the species based on the color of the animals from a Tagalog name (the holotype was collected from the Batangas Province, Luzon, Philippines), dalanghita, having reference to a small orange fruit. This attractive animal is immediately separated from other Halgerda species by its bright orange body color; most other Halgerda species have a white or gray-white body color. Fahey & Gosliner mention H. dalanghita feeds on unidentified orange sponges and that the three specimens from the Philippines were almost entirely embedded in a lobate orange sponge on which they had been feeding. The range of the species is the tropical Indo-Pacific (Natal, South Africa, Papua New Guinea, the Philippines, and Southern Japan {Kerama Islands}). Also, Mike Miller has a terrific photo of H. dalanghita, taken by Terry Gosliner, on his Slug Site. This photo shows a bit more detail of the gills and angled body ridges.
As of late November, 2005, thirteen described species of Halgerda are known from Okinawa's main island and the Keramas. These thirteen species are:
Halgerda albocristata H. brunneomaculata H. carlsoni H. dalanghita - The above featured animal H. diaphana H. elegans H. malesso H. okinawa H. onna H. rubicunda H. tessellata H. wasinensis H. willeyi
Literature Cited:
