Opisthobranch of the Week Data
Pleurobranchus grandis is considered to be very rare in Okinawan waters. I've never personally seen a specimen during more than thirty years of Okinawan diving. The above featured animal was photographed by Christopher Reschman in approximately twenty-five feet of water during a night dive. Chris reports (pers. comm.) finding two individuals of approximately the same size. I've added a second page showing the second of these two individuals. Chris's images are used here with his kind permission.
The following species description of Pleurobranchus grandisis taken from Bill Rudman's Sea Slug Forum (2001):
This large widespread Indo-West Pacific species is quite variable in colour, ranging form almost completely dark brown to white with pale brown spots. It usually can be described as white with large elongate brown patches. Like most large species of Pleurobranchus the mantle surface consists of rounded polygonal tubercles outlines by a reticulate pattern of white. The polygons in the white region are usually tipped with a diffuse pale brown. In living specimens the posterior part of the mantle is often held erect and folded into a posteriorly facing siphon. It can grow to 20cm or more.
In Rudman's "Related messages" section of the above citation there are numerous links which illustrate the variation within the species.
There are to date the following six described species of Pleurobranchus known from Okinawan waters, as well as several undescribed species.