Unidentia nihonrossija, 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 : 53-54

Unidentia nihonrossija sp. n. Fig. 42

Type material.

Holotype. ZMMU Op-517, 4.5 mm long (preserved), Japan, Osezaki, depth 10-15 m, 11.09.2016, coll. T.A. Korshunova, A.V. Martynov.

Type locality.

Osezaki, Japan.

Etymology.

After nihon ( “日本” (= “にほん”), meaning “Japan” in Japanese) and rossija ( “Россия” meaning “Russia” in Russian) in reference to the international group of Russian and Japanese scientists who organised the field work in Japan, during which this unique representative of the family Unidentiidae was collected.

Diagnosis.

Five to seven ceratal clusters, background colour whitish with dispersed light violet middorsal line, cerata orange to reddish orange, subapical parts of cerata with broad opaque white line, apical parts of cerata with white pigment, rachidian tooth with up to six denticles, central cusp bears small denticles, distinct distal receptaculum seminis, no accessory penial gland, penis with hollow stylet.

Description.

External morphology (Fig. 42 A–E). Body relatively narrow. Foot and tail narrow, anterior foot corners long. Rhinophores ca. 1.5-2 times shorter than oral tentacles, smooth. Dorsal cerata finger-shaped to fusiform, forming 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 on right side below second large ceratal clusters. Reproductive openings lateral, below first anterior cluster of cerata.

Colour (Fig. 42A). Background colour whitish. Digestive gland diverticula reddish orange. Rhinophores and oral tentacles light violet. A narrow dispersed light violet band runs from base of oral tentacles through middle part of dorsal side. Subapical parts of cerata with broad opaque white line. Apical parts of cerata without opaque cap of white pigment.

Jaws (Fig. 42G, H). Masticatory process more than one-third as long as jaw body. Edge of masticatory processes bears several rows of ridge-shaped denticles.

Radula (Fig. 42I). Radula formula: 39 × 0.1.0. Rachidian tooth elongate-triangular with short broad cusp. Rachidian tooth bears four to seven well-defined separated long lateral denticles strongly adpressed towards cusp (Fig. 42I). Cusp is not compressed by adjacent first lateral denticles. Lateral teeth absent.

Reproductive system (Fig. 42J). Diaulic. Hermaphroditic duct leads to convoluted ampulla of about two whorls. Vas deferens relatively long, no distinct prostate. Penial sheath narrow. Penis narrow conical, armed with curved hollow stylet. Oviduct connects through insemination duct into female gland complex. Vagina short and indistinct. Double proximal receptaculum seminis. Supplementary ( “penial”) gland absent.

Ecology.

Shallow waters, stony habitats.

Distribution.

Pacific side of middle Japan (Honshu).

Remarks.

From the type species of the genus Unidentia , the Eastern Pacific Mexican species U. angelvaldesi Millen & Hermosillo, 2012, U. nihonrossija sp. n. differs substantially both morphologically and by colouration, details of the radular teeth, and presence of double proximal receptacles ( U. angelvaldesi possesses a single receptaculum seminis). From the tropical Indo-West Pacific species U. sandramillenae sp. n. (see below), U. nihonrossija sp. n. differs both morphologically and according to the molecular phylogenetic analysis (Figs 1, 2).