Opisthobranch of the Week Data
Jorunna parva is considered to be very rare in the waters of Okinawa's main island as I have collected only two of these attractive little animals during more than thirty years of previous Okinawan diving. Both specimens were collected at the same time from an area of mixed sand and coral rubble at 200ft. Unfortunately, I can't be any more exact as to precisely where they came from as I had collected several large Ziploc® bags of miscellaneous phyla of both plants and animals from the same depth. The area from which the material came from, in addition to the mixed sand and coral rubble, was one rich in thallophytes (miscellaneous browns, greens, and reds). The material was placed into sorting bowls later at home and shortly thereafter the animals were found crawling about within the confines of the containers. A third individual was collected, photographed, and returned to the collection site by Shawn Miller from Maeda-misaki (Maeda Point) on 17 March, 2012 from twenty feet of water. Previously on these pages J. parva was mistakenly listed as Thordisa parva.
I've added a second page with images of the three Okinawa animals . . . Shawn's image is shown there with his kind permission. Incidentally, Atsushi Ono (2004, p. 145) has several images of Jorunna parva found in the Kerama Islands*.
Baba (1938) originally described Jorunna parva (as Thordisa parva) from a single 6mm specimen collected from Seto, Kii Japan during March of 1937. Baba (1949) suggests that this animal is indeed quite rare, at least in Japan at the time. Gosliner, et al (2008) mention J. parva is now known from the western Indian Ocean of South Africa, Tanzania, Aldabra Atoll, to the western Pacific of Australia, Papua New Guinea, Indonesia, Philippines, Palau, and Japan to the Marshall Islands. Rudman (2000) has a page on the Sea Slug Forum for J. parva. There is a discussion as well as several images showing some of the color variations within the species.
* Kerama Islands = the Kerama Islands Group, located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.