Halgerda diaphana Fahey & Gosliner, 1999 (58mm)
OPISTHOBRANCH OF THE WEEK
Opisthobranch of the Week Data
Frequency on Okinawa:
- Order: NUDIBRANCHIA
- Suborder: Doridina
- Family: Discodorididae
[brackets indicate range for all Okinawa-collected specimens of the species]
- Individual Collection No: RFB #3738
- Location: Seragaki, Okinawa (26o30.0'N, 127o50.9'E) [Channel Crevices, Horseshoe Cliffs, Onna Flats, Seragaki]
- Date: 9 October, 1999 [1987(1 indiv), 1990(2 indiv), 1991(5 indiv), 1992(4 indiv), 1994(2 indiv), 1995(2 indiv), 1996(3 indiv), 1998(4 indiv), 1991 (1 indiv)]
- Depth: 40ft (12m) [Intertidal, 10ft(3 indiv), 35ft, 40ft(2 indiv), 60ft, 70ft, 75ft, 80ft, 90ft, 105ft, 130ft, 135ft, 140ft(4 indiv), 145ft(2 indiv), 150ft, 165ft, 190ft]
- Water temperature at collection depth: 79.0oF (26.1oC)
- Size (Notum): 58mm [29mm(2 indiv), 34mm, 37mm, 39mm, 41mm, 42mm, 46mm, 48mm, 49mm(2 indiv), 50mm, 53mm, 58mm, 60mm, 61mm, 63mm(3 indiv), 66mm, 69mm, 73mm(2 indiv)]
- Specimen deposited: RFB Personal Research Collection (different individuals of the species deposited at Cal Acad Sci)
Halgerda diaphana, is a beautiful, recently described discodorid (Fahey & Gosliner, 1999), which is apparently unique to waters of the Ryukyu Archipelago*. The animal is considered uncommon on Okinawa; the first specimen was collected in May of 1990 and several dozen others have been collected since that time. The specific name diaphana comes from the Greek word diaphanes, meaning a gauzy texture which is translucent or transparent; this name was chosen by Fahey & Gosliner because the ground color of both the dorsal surface and the foot of the animal is translucent white and the viscera is clearly visible in a dorsal and lateral view.
The above featured animal was found during a daytime SCUBA excursion; it was crawling in the open amid spur and groove formations of a mostly dead coral reef, near the reef drop-off. Others have been collected from vertical rock walls, coral rubble, and silty-sand. In addition to the featured animal, I've included a photo of the designated type specimen (the holotype), which is typical of the species. In addition to the "type species", I've also included scans of two additional specimens showing some of the variation associated with the species.
* Okinawa is the largest of approximately seventy-two islands making up the Ryukyu Archipelago which stretches for 600km.
- Fahey, S. J. & T. M. Gosliner. 1999. Preliminary Phylogeny of Halgerda (Nudibranchia: Halgerdidae) from the Tropical Indo-Pacific, with descriptions of three new species. Proceedings of the California Academy of Sciences 51(11): 425-448, 10 figs., 2 tables.
Page Date: 20 Dec '99
Page Modification Date: 20 Dec '99
Digitally manipulated photo
Copyright © 1999 Robert F. Bolland