Pseudobornella sp. 1 (15mm)
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:

        I've not personally seen Pseudobornella sp. 1 here in the waters of Okinawa's main island and Atsushi Ono mentions (pers. comm.) seeing only three individuals in the Keramas* and of course considers the species to be very rare there. Atsushi also reports the above featured animal was found on Euphysora bigelowi (Hydrozoa, Corymorphidae) in association with a sandy bottom.

        The genus Pseudobornella was proposed by Baba (1932) and the following is taken from Baba's original description of external morphology concerning the proposed genus:

        General body form much as in Bornella. Two tentacles at the anterior end of the head subdivided into several (2-4) extraordinarily elongated, tapered papillae. Rhinophore-sheath strong, elevated, with papillae, of which two are lateral, short and conical, and one is posterior and extremely slender, in addition to the perfoliated rhinophore. Dorsal papillae arranged in several (usually 4) pairs, each papilla accompanied by a moderate number of branchial leaflets. Genital opening on the right anterior body side, obliquely below the 1st dorsal papilla.
Baba designated the type species to be Pseudobornella orientalis (Baba, 1932).

The following comparison between Bornella and Pseudobornella is modified from Baba (1932):



Body size:

moderate size (20mm more or less)

small (3-7mm)


2, each formed of short conical papillae
arranged in two rows

2, each subdivided into 2-4 very long papillae


several slender papillae around the rhinophore

with 2 short lateral and 1 very long posterior papillae

Dorsal papilla:

elongated, divided into a few fingers



1-3 or more, pinnate

gill-leaflets simple and numerous

        I've previously featured three members of the closely related genus, Bornella, from the waters of Okinawa's main island. These three animals are:

  • B. anguilla
  • B. stellifer
  • B. sp. 1
  • Literature Cited:

            * Keramas = the Kerama Islands Group, located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.

    Page Date: 09 May '05
    Page Modification Date: 09 May '05
    Digitally manipulated photo
    Copyright © 2005 Robert F. Bolland