Opisthobranch of the Week Data
Hypselodoris krakatoa is considered to be very rare in Okinawan waters. I've never personally seen the species during numerous years of diving in Okinawan waters. The above image was taken by Shawn Miller and is used here with his kind permission. Shawn photographed this attractive chromodorid from beneath the pilings of Tengan Pier. There's a series of photographs and associated messages ofH. krakatoa on Bill Rudman's Sea Slug Forum.
In addition, I've also added a second page w/ two additional images of Shawn's animal, photographed at the same date and place.
The following information on the external morphology of H. krakatoa is taken from Gosliner & Johnson (1999):
External morphology: Living animals are 10-55 mm in length. The body is elongate and high in profile. The posterior gill region is higher than the rest of the mantle. The head is spatulate. The mantle has a very complex pattern. The body is light yellowish brown with darker brown patches over the body surface. These brown patches from [sic] a distinctive irregular figure eight pattern over the surface of the notum. The arrangement and density of these patches is highly variable. The notum is marked by two parallel black lines that begin anterior to the rhinophores and end and join posterior to the gills. These lines are overlaid by scattered opaque, white or light blue spots. Between these lines is a complete or interrupted black line with opaque whitish spots. Other isolated black lines or black and opaque white spots may be scattered over other portions of the dorsal surface, sides of body and foot. The mantle margin around the head and foot is light purple. The well separated rhinophores are uniformly rusty-brown with opaque white apical spots. Immediately behind the rhinophores are two patches of lighter, more translucent pigment, through which the eyes are visible. Each of the seven simply pinnate gills is yellowish brown with a rust-red rachis.
The above featured animal is one of thirteen described species of Hypselodoris found in Okinawan waters. The thirteen species identified to date (July, 2011) are: