Opisthobranch of the Week Data
Ceratosoma palliolatum is an attractive member of the genus and is considered to be very rare in Okinawan waters; I've not personally seen nor collected any specimens and it is unknown from Okinawa Island but has been photographed by Atsushi Ono in the Kerama Islands. The close proximity of the main island of Okinawa to the Kerama Islands, as well as the similar opisthofauna to that of the Kerama Islands, suggests the possibility that it is also present here on Okinawa proper. The above featured, but uncollected animal, is one which was photographed in the waters of Gahi 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 during September of 1998, in the East area of Gahi Island in 3m of water (the animal was found on the underside of dead coral rubble). Atsushi's photograph is used here with his kind permission and also, it should be noted that Atsushi considers the species to be rare in the Kerama Islands in as much as he has seen only the above featured animal as well as a second 20mm (approx.) individual found in the same area (per. comm.).
Rudman (1988) described the species from two animals; the holotype* specimen was collected from Darwin Australia in late 1985 and a paratype* specimen from Kwajalein (Marshall Islands) in late 1983. The following partial description of the species is from Rudman (1988).
The animal has relatively high sides and the posterior end of the foot extends some distance beyond the mantle. The body is firm and rigid and there is a continuous mantle edge around the body with three lateral lobes on each side. There is no development of a mantle "horn" or lobe in the posterior midline. The rounded anterior end of the foot is split transversely and the foot corners are slightly angled. There is a distinct keel down the dorsal midline of posterior foot.
The name palliolatum comes from Latin and means to wear a small Greek coat or mantle. The name was chosen by Rudman in reference to the presence of the entire mantle skirt around the body.
There are seven described species of Ceratosoma currently known (as of April, 2001) from Okinawan waters, these seven are:
*holotype and paratype specimens: See "Type" Dictionary for explanation.