OKINAWAN
OPISTHOBRANCH OF THE WEEK

Haminoea sp. 1 (6mm)
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:

        The above featured attractive little haminoeid, Haminoea sp. 1, was photographed by Atsushi Ono from the waters of Gahi 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 November of 1999 in 5m of water from a reef ridge amid dead Acropora corals. I've not personally seen Haminoea sp. 1 in the waters of Okinawa's main island and Atsushi reports (pers. comm.) he has seen numerous individuals but considers the animal to be uncommon in the Kerama Islands.

        There are similar appearing haminoeids on the Sea Slug Forum (as Haminoea sp. 1). Clay Carlson (pers. comm. 2004) recently mentioned that he feels the above Gahi Island specimen is the same as Haminoea sp. 1 on the Forum. Clay points out the following information concerning his Guam material:

We have no idea if this particular species has already been described and haven't tried wandering around various museums to see if there is a match. The SEM we have on a 4.8mm specimen shows a radular formula of 4.1.4 with the innermost lateral denticulate on the inner edge; the 2 outermost on the outer edge -- a pattern so far unreported for any haminoeid form.

        Paula Mikkelsen (2004) points out some of the challenges* associated w/ studying the shelled cephalaspids:

Shelled Opisthobranchs (Cephalaspidea)

Opisthobranch gastropods comprise a large and diverse group of marine snails and slugs, including some of the most beautiful and most specialized forms. The most recognizable to non-specialists are perhaps the sea slugs, or nudibranchs, and the pelagic sea butterflies, or pteropods. Morphologically intermediate between the more traditional snails and the shell-less nudibranchs are the "bubble-snails," belonging to the Order Cephalaspidea. Challenges to studying the relationships among these snails are: (1) species descriptions based almost exclusively on shells, which are themselves reduced (i.e., relatively featureless, paper-thin) compared to those of other gastropods; (2) high phylogenetic importance of characters from soft-body morphology, necessitating live observation, gross dissection, and histology; (3) reduction and loss of many morphological features, such as the shell, operculum, radular teeth, jaws, and stomach chamber; and (4) high incidence of parallelism and/or convergence in characters, especially those related to the burrowing habit. Phylogenetic analyses from these studies have confirmed the "rampant parallelism" suspected in cephalaspid morphology, but have nevertheless identified useful characters to suggest new classifications and re-defined clades.
* Taken from an on-line resource of the American Museum of Natural History, Division of Invertebrate Zoology.

        In addition to the above featured animals, I've previously presented on these pages the following three members of the genus from Okinawan waters:

Literature Cited:


Page Date: 08 Mar '04
Page Modification Date: 06 Nov '06
Digitally manipulated photo
Copyright © 2006 Robert F. Bolland