Opisthobranch of the Week Data
Trapania toddi is unknown from Okinawa's main island as of late-July, 2013, but the close proximity of Okinawa, as well as the similar opisthofauna to that of the Kerama Islands, suggests the possibility that it is also present here on the main island of Okinawa. The above featured animal was photographed but not collected in the waters from Agonoura Bay, off 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 during January of 2011 in 20m of water from an area of small rocks and deal corals. Atsushi's photograph is used here with his kind permission. It should be noted that Atsushi considers the species to be very rare in the Kerama Islands as he has seen only the above featured individual (per. comm.).
The following description of color as well as remarks concerning Trapania toddi are taken from Rudman's 1987 publication:
Colour: The body of Hong Kong specimens is translucent white with brown reticulate patches arranged in a regular pattern. There are yellow markings on the oral tentacles, lateral processes, rhinophores, gills and posterior tip of the foot.
There is a brown reticulate patch forming a band across the head and three patches on the dorsum between the gills and the rhinophores. One of these patches is in the midline just behind the rhinophores and the other two are behind the median patch, one on either side of the midline. On the sides of the body there is a patch below and just behind the rhinophores, and another just below and in front of the gills. Behind the gills there is an elongate patch on each side.
The oral tentacles and lateral processes are white with a yellow band just below the tip. The lateral processes alongside the gills also have a brown spot halfway along their length. The rhinophore stalk is translucent and the bottom half of the club is brown with white specks. The top half of the club is yellow and there is a translucent white tip. The translucent gills have a yellowish tip with a band of brown just below. The posterior tip of the foot is also yellow.
In the much smaller specimen from the Red Sea the brown reticulate markings are finer and more elongate but apart from the head region all the brown patches are placed as in the Hong specimen. In the Red Sea specimen there is an elongate brown reticulate patch running along each side of the head and out on to the series, the largest being alongside the cusp and basal third of the oral tentacles. Another difference is that there are no yellow markings on the Sudanese specimen but opaque cream regions, visible in the photographs, suggest that a yellow pigmentation may develop in larger specimens.
There are close similarities in colour and radular morphology between the specimens from the Red Sea and Hong Kong and the slight differences are probably related to size and age, the Red Sea specimen being small and immature. However to prevent possible confusion the Hong Kong material only is designated type material.
Trapania fusca (Lafont) has a whitish body with patches of brown spots and the appendages and rhinophores are yellow. This Mediterranean species therefore has a superficial similarity to T. toddi but in the latter the brown patches are situated differently and consist of brown reticulations not spots. The radular morphology is also different, the teeth of T. fusca being more similar to those of T. reticulata and T. darvelli than to T. toddi.
The records presented here from the Sudanese Red Sea and Hong Kong suggest a wide distribution for this species.
Previously I've featured several members of the genus Trapania on these pages and as of the current date (1 August, 2013), there are several described species reported from Okinawan waters. These featured animals are as follows:
T. euryeia T. gibbera T. naeva T. squama T. todii the above featured animal T. vitta