OKINAWAN
OPISTHOBRANCH OF THE WEEK

Sagaminopteron nigropunctatum Carlson & Hoff, 1973 (12mm)
[photo by Atsushi Ono]

Opisthobranch of the Week Data

Taxonomy:

Frequency on Okinawa: Collection Data:
[brackets indicate range for all Okinawa-collected specimens of the species]


Species Account:

        Sagaminopteron nigropunctatum was originally described from Guam (Carlson & Hoff, 1973) and the authors named the animal nigropunctatum because of the numerous small black punctate markings which cover its body. The species has since been found in many other areas of the Western Pacific as well as the Indian Ocean. Incidentally, the generic name, Sagaminopteron, was named by Tokioka & Baba (1964) for Sagami Bay, Japan, where Emperor Hirohito collected numerous opisthobranchs that have been subsequently studied by Kikutaro Baba.

        The following information, in part, is taken from a recent personal communication (February, 2001) from Clay Carlson:

        Sagaminopteron nigropunctatum is considered to be one of the most common of the Gastropteridae found on Guam, although due to the cryptic color resemblance to its host, the species is difficult to find. Distribution of the species is known to include Guam, Rota (Northern Marianas), Palau, Philippines (Batangas {Luzon}, Bohol, Mindoro), and Japan (Kerama Islands, Okinawa). The host is a demosponge, Dysidea spp. (the gray colored D. granulosa, and also occasionally another sponge, D. herbacea, which is sometimes a pale blue-gray color on parts of the sponge not exposed to sunlight). Specimens of S. nigropunctatum tend to match the color 'intensity' of the host -- e.g., darker on darker forms of D. granulosa. The few found on D. herbacea have been very pale. Clay reports that they are most frequently found singly, rarely in pairs. At least 229 specimens have been observed although the count is a little misleading since Clay & Patty Jo no longer look for the animal unless they want to show it to someone. Specimen sizes range between 3.2mm and 16mm.

        Clay & Patty Jo have a photo of several egg masses of S. nigropunctatum as well as a photograph of the internal shell, posted on Bill Rudman's Sea Slug Forum.

        Sagaminopteron nigropunctatum is unknown from Okinawa Island as of late February, 2001, but the close proximity of Okinawa to the Kerama Islands suggests the possibility that it is also present here on 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 (1999) in 1998 and is used here with his kind permission. This same animal is featured in his Opisthobranchs of Kerama Islands, 1999 (photo # 019, p. 19). More than ten individuals have been seen in the Kerama Islands in the last five years and is considered to be uncommon there (Atsushi Ono, pers. comm.).

        There are three described species of Sagaminopteron found here in the Ryukyu Archipelago (as of late-February, 2001), plus an unknown Okinawa-collected species. These are:

  • Sagaminopteron nigropunctatum (the above featured animal)
  • Sagaminopteron ornatum
  • Sagaminopteron psychedelicum
  • Sagaminopteron sp. 1
  • Literature Cited:


    Page Date: 26 Feb '01
    Page Modification Date: 26 Feb '01
    Digitally manipulated photo