Plocamopherus imperialis (Angas, 1864) 40mm
Photo by Atsushi Ono

Opisthobranch of the Week Data


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

Species Account:

        Plocamopherus imperialis is considered to be uncommon in Okinawan waters; I've not personally seen this attractive polycerid in the waters of Okinawa's main island although Atsushi Ono mentions the above featured animal is one of seven which he has seen in the Keramas* (pers. comm.). The animal was collected by Atsushi in January of 1999 from a rope-supported buoy within the confines of a Zamami Island bay. Atsushi's specimen nicely illustrates the pair of posterior lateral bulbs ("globes") on the side of the body which produce flashes of light.

        The following description of Plocamopherus imperialis is taken from Marshall & Willan (1999):

This is a large dorid nudibranch that cannot retract the gills into a pocket beneath the mantle. The mantle brim and the tail crest bear numerous small papillae. The foot ends in a pointed tail. Plocamopherus imperialis bears one pair of "globes" on the mantle brim immediately behind the level of the gills. The rhinophores are lamellate and their [sic] are five large gills.

The body is orange or red, and copiously spotted with brown. The rhinophores have an orange stalk, and a brownish clavus with a white apex. The gills have orange bases with brown speckles with white apices. The "globes" are a reddish colour.

Plocamopherus imperialis is able to swim by powerful, side-to-side flexions of the body. The "globes" on the mantle brim emit a brief flash of bluish light when the animal is irritated.

Both the diet and spawn are unknown.

        There are currently (as of Mid-Mar., 2012) four described species of Plocamopherus found in Okinawan waters, as well as several undescribed animals:

  • P. ceylonicus
  • P. imperialis (the above featured animal)
  • P. maculatus
  • P. tilesii
  • P. species 1
  • P. species 2
  • P. species 3
  •         * Keramas = the Kerama Islands Group, located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.

    Literature Cited:

    Page Date: 12 Nov '01
    Page Modification Date: 19 Mar '12
    Digitally manipulated photo
    Copyright © 2012 Robert F. Bolland