Hopkinsia plana (Baba, 1960) 3.5mm
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:

        The above featured little goniodorid, Hopkinsia plana, was photographed by Atsushi Ono from the waters of 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 photographed by Atsushi during May of 2003. Ono (pers. comm.) reports seeing in excess of 10 individuals in association with miscellaneous flotsam & jetsam.

        Hopkinsia plana was originally described by Baba (1960, as Okenia plana). The description was based on a series of animals from Osaka Bay (1 specimen collected from Zostera sp.) and many specimens (on Sargassum sp.) from Seto's Inland Sea.

        The following is taken from Rudman & Darvell (1990):

Remarks. Very similar to Hopkinsia pilosa in shape and colour but differs in having only a few long rounded papillae on the mantle. There is usually one in the middle of the back and about five down each side near the mantle edge. In Japanese and Hong Kong specimens there are small brown flecks all over the mantle and body but in Australia and New Zealand there are much larger brown patches. Hopkinsia plana is reported to feed on the colonial bryozoan Membranipora membranacea, a common fouling organism on wharf piles, and algae. Specimens from Hong Kong, 10 mm long preserved, have been found on an as yet unidentified bryozoan.

Geographic Distribution. It is suggested that the wide distribution of this species, known from Japan, New Zealand, Australia and California, is an artificial distribution brought about by its food, the fouling bryozoan Membranipora being transported long distances by shipping.

        In addition to Atsushi's image above, there are photos of Hopkinsia plana posted on-line at:


Literature Cited:

Page Date: 02 Aug '04
Page Modification Date: 02 Aug '04
Digitally manipulated photo
Copyright © 2004 Robert F. Bolland