Opisthobranch of the Week Data
Roboastra sp. 1 is considered to be rare in Okinawan waters. I'm not aware it has been seen or collected in the waters off Okinawa's main island and Atsushi Ono reports (pers. comm.) seeing only the above two uncollected animals this year as well as four others seen last year. Atsushi's photograph is used here with his kind permission. The above featured animals were found on a sandy bottom in the waters off Nishihama beach, Aka Island in the Keramas*. In the above photograph the two individuals are aligned right side to right side and are in the process of exchanging sperm (the extended reproductive organ on the right hand side of both animals is seen in the photo. Opisthobranch molluscs are simultaneous hermaphrodites with both male and female sex organs). There is a Roboastra sp. similar to the above featured animals pictured in Gosliner, et al (2008, p. 123 as Roboastra sp.).
On these pages I've previously featured two described species of Roboastra from Okinawa's main island, R. gracilis and R. luteolineata.
* Keramas = the Kerama Islands Group, located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.