Opisthobranch of the Week Data
Colpodaspis thompsoni is a small and distinctively colored cephalaspid, which superficially appears to be more snail-(Prosobranch)like than the opisthobranch which it is. The mantle completely covers the fragile bubble-shaped shell and is black with large yellow warts on white patches of pigment. Marshall & Willan (1999) report the animal is able to secrete a milky-white fluid when it is irritated.
The following information concerning the species is taken from comments by Bill Rudman (2000) on the Sea Slug Forum:
A small, but brightly coloured, snail-like sea slug. The fragile bubble-shaped shell is completely enveloped by the mantle. On the right side of the mantle there is an elongate exhalent siphon. The head is produced into a pair of enrolled tentacles or rhinophores which lead to a deep lateral groove on each side. The eyes are embedded beneath the skin and can be seen as two black spots just in front of the shell. There is a large central mucus gland in the sole of the foot which probably produces a sticky mucus enabling the animal to stick on the algae on which it is found. It is black with large yellowish warts on white patches. We know nothing of the biology or food of any species of Colpodaspis.
The placing of Colpodaspis with Diaphana and Newnesia in the Diaphanoidea, by most experts, is a marriage of convenience rather than a convincing statement of phylogenetic relationships. Further studies are required before we can say anything sensible about their relationship to each other and to other opisthobranchs.
Colpodaspis thompsoni is considered to be very rare on the main island of Okinawa. I'm sorry to report that as of early March of 2001 I've not yet personally collected this small and unusual cephalaspid, although a single uncollected animal was photographed by Mr. Yokoi Kensuke, at the Sunabe Sea Wall dive area, Okinawa. One of his photographs of the Sunabe animal, which appears to be near-identical to Atsushi Ono's Kerama animal above, is used here with his permission.
The above featured, but uncollected animal, is one which was photographed in the waters of Zamami Island, 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 Ono in May of 1999 from the reef edge in a bay, in approximately 5m of depth. Atsushi's photograph is used here with his kind permission. Atsushi considers the species to be uncommon in the Kerama Islands and has seen 7~8 individuals there (per. comm.). Several images of this same animal are featured on Bill Rudman's Sea Slug Forum.
As of the current date (01 July, 2015) I've featured the following Colpodaspis species on these pages, the above described species as well as two unknown species, all from Okinawan waters. These featured Colpodaspis species are: