Opisthobranch of the Week Data
The holotype* of Flabellina delicata was collected from Papua New Guinea (PNG) on 11 February, 1988. Prior to the collection of this attractive flabellinid from the Kerama Islands it was known only from PNG and Natal, South Africa; this Okinawan animal is a new record for this part of the world, and it helps to fill in the rather large distributional gap between PNG and South Africa. This highly attractive flabellinid was named delicata by Gosliner & Willan (1991) in reference to the elongate, graceful body form of the species. A photograph of the species is also featured in Gosliner (1987: p. 114, #224, as Coryphellina sp.).
The following description is taken, in part, from the description of external morphology by Gosliner & Willan (1991):
The living animals are 15-20mm in length. The general body color is deep reddish purple. Generally, the oral tentacles are a deeper purple than the rest of the body. The rhinophores are deep red throughout. The cerata are translucent white basally, with the opaque white digestive gland giving the cerata an overall white appearance. Near the middle of each ceras, an opaque white transverse band is present on its surface. More distally, the ceras is again translucent and a golden-yellow-orange enlarged portion of the digestive gland is visible. A subapical transverse ring of translucent purple is present just below the translucent white apex.
The body is narrow and delicate in appearance. The oral tentacles are slender and elongate, terminating at an acute apex. The rhinophores are elongate and slender with approximately 30 well-separated papillae on their posterior surface. The numerous cerata are slender and cylindrical throughout their length. The cerata are arranged in distinct, well-separated clusters.
Willan (per. comm.) feels that the differences in ceratal coloration between the above featured animal and the original specimens from PNG are very minor and must be part of the intraspecific variation.
I've not personally seen nor collected any specimens and it is unknown from Okinawa Island at the current time (mid-September, 2001), but it has been photographed by Atsushi Ono in the Kerama Islands. The close proximity of the main island of Okinawa to the Kerama Islands, as well as the similar opisthofauna to that of the Kerama Islands, suggests the possibility that it is also present here on Okinawa proper. The above featured animal is one which was photographed in the waters of Zamami 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 found by Atsushi Ono on the common hydrocoral, Millepora dichotoma in 8m of water. Atsushi's photograph is used here with his kind permission and the species is considered to be uncommon in the Kerama Islands (Ono, via pers. comm., mentions seeing five or six individuals).
F. delicata is one of six described Flabellina species presented on these pages. These six species known from Okinawan waters are:
F. bicolor F. delicata - the above featured animal F. exoptata F. macassarana F. riwo F. rubrolineata
*Holotype: See "Type" Dictionary for explanation.