OKINAWAN
OPISTHOBRANCH OF THE WEEK

Bornella johnsonorum Pola, Rudman & Gosliner, 2009 (ca. 40mm)
Photo by Randy Birt

Opisthobranch of the Week Data

Taxonomy:

Frequency on Okinawa: Collection Data:
[brackets indicate range for all Okinawa-photographed specimens of the species]


Species Account:

        Bornella johnsonorum is considered to be very rare in the waters of Okinawa's main island. I've never personally seen the species after many years of okinawan diving however both Randy Birt and Shawn Miller have kindly provided recent photos of B. johnsonorum from Okinawa and the images are used here with their kind permission.

        The above photo is one taken by Randy on the twenty-forth of April this year from 30 feet of water during a night dive off the Kadena North dive site. I've added a second page with an additional photo taken by Randy as well as one taken by Shawn Miller.

        Also, Scott Johnson has an image of B. johnsonorum from Kwajalein posted on the Sea Slug Forum.

        The following morphologic description of Bornella johnsonorum is taken from Pola, Rudman & Gosliner (2009):

External morphology: The general body shape is elongate and limaciform with the posterior end of the foot being long and tapering. The background color is translucent clear with the orange to orange-brown viscera showing through. Epidermal and sub-epidermal white flecks are scattered all over, mostly aggregated into patches of varying sizes. In some specimens, a faint, diffuse orange reticulation is visible around the whitish patches. On either side of the mouth is a lobe-like oral tentacle with 9-10 papillae arranged along the margin. The rhinophore sheaths have a narrow stalk and the posterior papilla is slender, about three times taller than the three anterior and anterolateral papillae. The rhinophore sheaths and anterior papillae are colored as in the rest of the body, while the tall posterior papilla, on each sheath, is mostly white. None of the papillae have an orange subapical ring. The rhinophores are translucent white with a minute orange tip and have approximately 16 to 18 lamellae. There are five to six pairs of dorsolateral processes, with one or two small, unpaired processes near the tail. The first dorsolateral process on each side has two or three bulbous papillae, usually one on the outside and two on the inside. The processes in the second and often the third pair have a single papilla on the outer side. The fourth through sixth processes are usually unbranched, lacking any papillae. They are arranged irregularly on either side of the dorsal midline. The final one or two single processes are very small and located in the dorsal midline. Like those on the rhinophore sheaths, the bulbous papillae are mostly white, without orange subapical rings. Small tripinnate gills are located on the inner surfaces of the first four to six pairs of processes, and become smaller posteriorly. The reproductive opening is on the right side, about two thirds of the way from the rhinophore stalk to the first dorsolateral process. The anus is more dorsal, also on the right, between the first and second dorsolateral process, a bit closer to the second.

        As of early September, 2012 I've recorded three described species of Bornella from the waters of Okinawa's main island. These three animals are:

Etymology:

Literature Cited:


Page Date: 10 Sep '12
Page Modification Date: 24 Sep '12
Digitally manipulated photo
Copyright © 2012 Robert F. Bolland