Opisthobranch of the Week Data
This very attractive tritoniid was originally featured at this URL as an unknown opisthobranch of the week (Tritonia sp. 1); I'm happy to say the animal has now been recently described as Tritonia bollandi (Smith & Gosliner, 2003). The above image is one of the holotype* (CASIZ** 105327), deposited at California Academy of Sciences. This animal is considered to be uncommon on Okinawa as I have seen and collected a total of eight individuals. The above specimen was collected on the twelfth of May, 1995 from a moderately early morning Scuba dive (08:30) from an area of mixed sand and coral rubble. It was found on a red ellisellid octocoral. Additional specimens of red ellisellid octocorals found with T. bollandi were identified by Gary Williams of the California Academy of Sciences as Verrucella aurantia. Quite remarkably, all but one of the eight collected specimens were found on a red gorgonian octocoral (ellisellids, most were identified as V. aurantia) and the tritoniid was not cryptically colored and actually stood out quite readily against the red-colored octocoral. In addition to the Okinawan specimens the species is also known from Indonesia (Rudman, 2003).
The following is a copy of the abstract taken from the Smith & Gosliner paper (2003) describing T. bollandi :
A new species of tritoniid nudibranch is described. Tritonia bollandi sp. nov. is known from its type locality of Seragaki Tombs, Okinawa, and from Indonesia, and has been found at depths of 58 to 75 m. The animal reaches 88 mm in length, and mature specimens are olive green in color, with lighter colored branchial plumes, nearly white rhinophores, and a thin white margin along the notal margin. The body appears granular due to the presence of small low tubercles on all parts of the body, except for the foot. The oral veil is slightly bilobed and bears 12 to 14 elongate digitiform processes, many of which are apically bifid. The notal margin extends along and slightly overhangs the sides of the body. From the notal margin are produced 9 to 14 pairs of arborescent branchial plumes, and the sheaths of the rhinophores, whose margins are undulate and flange-like. The rhinophore shafts are retractable, and are palmate in appearance, with a central clavus surrounded by a stepped series of pinnate processes. External genitalia are on the right side of the animal, behind the third anterior branchial plume. The anus and nephroproct are also on the right side, behind and just below the 4th branchial plume, close to the notal margin. The anterior foot margin is rounded. Buccal armature includes a pair of jaws with 2 to 4 rows of microscopic denticles along the masticatory border. The radula has a tricuspid rachidian, a differentiated first lateral tooth, and a series of hamate to falcate lateral teeth. There are no cuticular plates within the stomach. Tritonia bollandi sp. nov. has been observed to feed upon gorgonian octocorals of the family Ellisellidae (Gray, 1859), in particular Verrucella aurantia (Gray, 1869). Sclerites produced by the octocoral were isolated from nudibranch digestive system contents and compared with sclerites isolated from octocoral samples, providing further evidence of the association between Tritonia bollandi sp. nov. and the octocoral family Ellisellidae. This is the first record of predation by a nudibranch on this family of octocoral.
I've also added an additional page featuring paratype specimens of the newly described species.
T. bollandi is the only confirmed species of the genus known from Okinawa's main island although I've collected several closely related unknown tritoniids here (Tritonia sp. 2 and Tritoniid sp. 1), profiled previously.
*Holotype & Paratype: See "Type" Dictionary for explanation.
**CASIZ: California Academy of Sciences Department of Invertebrate Zoology