Unidentia sandramillenae, Korshunova, Tatiana, Martynov, Alexander, Bakken, Torkild, Evertsen, Jussi, Fletcher, Karin, Mudianta, I Wayan, Saito, Hiroshi, Lundin, Kennet, Michael Schroedl, & Picton, Bernard, 2017

Korshunova, Tatiana, Martynov, Alexander, Bakken, Torkild, Evertsen, Jussi, Fletcher, Karin, Mudianta, I Wayan, Saito, Hiroshi, Lundin, Kennet, Michael Schroedl, & Picton, Bernard, 2017, Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new families, genera, and species (Mollusca, Gastropoda), ZooKeys 717, pp. 1-139 : 55

Unidentia sandramillenae sp. n. Fig. 43

Type material.

Holotype, ZMMU Op-617, 7 mm long (preserved), Bali, Tulamben, 02.02.2017, 5-10 m depth, stones, collector I Wayan Mudianta.

Type locality.

Bali Island, Indonesia.

Etymology.

In honour of prominent nudibranch researcher, Sandra Millen (The University of British Columbia), who for almost 50 years has conducted fine taxonomic studies, including separation of the new family, Unidentiidae , together with Alicia Hermosillo.

Diagnosis.

Eight to ten ceratal clusters, ground colour and cerata whitish with violet hue, purple middorsal line, rachidian tooth with up to eight denticles, central cusp bears small denticles only in anterior radula, two proximal seminal receptacles, no accessory penial gland, penis with hollow stylet.

Description.

External morphology (Fig. 43 A–C). Body elongate 7 mm in length (preserved). Rhinophores similar in size to oral tentacles, smooth. Cerata finger-shaped to fusiform, placed on several distinctly elongate elevations with ceratal clusters along dorsal edges. Apices of cerata gradually pointed, with elongate cnidosac. Distinct notal edge absent. Digestive gland diverticulum fills significant volume of the cerata. Anal opening pleuroproctic towards acleioproctic position on right side below second large ceratal clusters. Reproductive openings lateral, below first anterior cluster of cerata.

Colour (Fig. 43 A–D). General colour translucent white with purple thin middorsal line; oral tentacles covered in purple pigment nearly half its length; subapical purple rings on cerata.

Jaws (Fig. 43E). Jaws broadly triangular, masticatory borders with special elaborate long denticles placed in clusters.

Radula (Fig. 43H, I). Radula formula 25 × 0.1.0. Rachidian tooth with up to eight distinct denticles. Central cusp smooth, widened in the middle and distinctly narrowed towards the tip; no small denticles at the base in posterior and middle teeth; vestigial denticles may present on the cusp of a few anterior teeth (Fig. 43I). No lateral teeth.

Reproductive system (Fig. 43K). Diaulic. Ampulla very voluminous, folded twice (Fig. 43K, am). Prostate thick (Fig. 43K, pr). Vas deferens short (Fig. 43K, vd), penial sheath elongate, conical penis armed with hollow stylet (Fig. 43K). Double proximal receptaculum seminis (Fig. 43K, rsp).

Biology.

On stones and algae covered with athecate hydroids (Fig. 43C, D).

Distribution.

Currently Indonesia, but probably Indo-West Pacific.

Remarks.

Unidentia sandramillenae sp. n. differs considerably from the only other known species of the genus Unidentia , U. angelvaldesi Millen & Hermosillo, 2012, both externally and internally. Externally, Unidentia sandramillenae sp. n. has a whitish ground colour whereas the Mexican specimens of U. angelvaldesi often have a red-orange ground colour. Internally, Unidentia sandramillenae sp. n. differs from U. angelvaldesi in the shape of the central cusp of the rachidian teeth, the shape of the ampulla and the presence of a distinct second seminal reservoir. Furthermore, in the original description of U. angelvaldesi several distinct species from various regions of the Pacific were commingled. Because the holotype was originally from Mexico in the eastern Pacific, the species U. angelvaldesi should be restricted to specimens from the tropical eastern Pacific. There are no molecular data available for the Mexican U. angelvaldesi ; however, according to our new data, a separate species of Unidentia , which clearly differs from the Unidentia sandramillenae sp. n. from Bali, is also present in Japan and described here as U. nihonrossija sp. n. (Figs 42, 44, red lines). Therefore, taking into consideration the considerable morphological differences between U. angelvaldesi and Unidentia sandramillenae sp. n. these species should also have a considerable molecular gap (Fig. 44, blue line), that should be proved in further studies. In addition, the clade U. angelvaldesi is distant from Flabellinopsidae fam. n. according to a recent publication ( Goodheart et al. 2017).

Uncorrected p-distances of the mitochondrial barcode marker (COI) between U. sandramillenae sp. n. and U. nihonrossija sp. n. reach 14.2%. Uncorrected p-distances between P. amica sp. n. and P. goddardi reach 12.2%. In contrast, the distance values between Unidentia and Pacifia ranged between 18.3-20.7% supporting the decision to create the new genus Pacifia .