OKINAWAN
OPISTHOBRANCH OF THE WEEK

Trapania naeva (20mm)
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:

        Trapania naeva is considered to be very rare in Okinawan waters; only four individuals have been seen by Atsushi (pers. comm.) and RFB has seen none directly off Okinawa's main island. Previously this animal was posted on these pages as Trapania sp. 2, but with publication of the recent Gosliner & Fahey (2008) paper I've now upgraded the page and made the name change. The above featured animal was photographed and collected from Zamami Island in the Kerama Islands, 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 during July of 1998 in 20m of water. The animal was initially found on a sponge having endoprocts on its surface and it was located in a rocky area having strong currents. Atsushi reports (pers. comm.) other individuals have been seen on both dark brown and orange-colored sponges. Atsushi's photograph is used here with his kind permission.

        Bill Rudman has numerous images of this attractive animal on the Sea Slug Forum.

        The following is taken from Gosliner & Fahey (2008):

Distribution
This species has been reported from Japan (Ono, 1999; Nakano, 2004), Indonesia, Fiji, Tanzania, Kenya, Reunion, Rodrigues Island, the Maldives and Northwest Australia (Rudman SeaSlug Forum).

External morphology
The living animals range from 5-7mm long. The body shape is elongate and convex, without a distinct notal margin. The body only slightly broadens in the branchial region The head is rounded anteriorly and the anterior foot margin is extended into elongate tentacles. The oral tentacles are short and cylindrical with a curved apex. The posterior end of the foot is sharply tapered with a rounded posterior tip. The non-retractile, perfoliate rhinophores are relatively short with 12-14 lamellae. The apex of the rhinophores is simply rounded without an extended appendage. The extra-rhinophoral appendages are relatively short and have a curved apex. The gill consists of three tripinnate branches. The extra-branchial appendages are nearly upright and stout. The body is white and nearly transparent. There are large blotches of black pigment arranged somewhat symmetrically along the sides of the dorsum and one patch on the anterior side of the foot. The anterior head tentacles are white. The oral tentacles are dark brown or black. The extra-rhinophoral and extra-branchial appendages are the same dark brown or black as the oral tentacles. The base of the extra-branchial appendages however, is white. The rhinophores and gill leaves are dark brown or black.

        Previously I've featured several members of the genus Trapania on these pages and as of the current date, there are several described species reported from Okinawan waters. The featured animals are as follows:

  • T. euryeia
  • T. gibbera
  • T. naeva the above featured animal
  • T. squama
  • T. toddi
  • T. vitta
  • Etymology:

    Literature Cited:


    Page Date: 05 May '08
    Page Modification Date: 01 Aug '13
    Digitally manipulated photo
    Copyright © 2013 Robert F. Bolland