Adalaria boussoleana, Bergh, 1878

Ekimova, Irina A., Grishina, Darya Yu. & Nikitenko, Ekaterina D., 2024, Nudibranch molluscs of Sakhalin Island, Northwestern Pacific: new records and descriptions of two new species, Ruthenica, Russian Malacological Journal 34 (2), pp. 69-91 : 76-80

Adalaria boussoleana sp. nov.

( Figs 2C, 4 , 5 )

Zoobank registration: urn:lsid:zoobank.org:act:

B1249966-6553-466D-A81E-715C146F0F79

Type material: Holotype MIMB48047 , dissected, the Sea of Okhotsk , Bay of Patience, 47°42.5’N, 144°30.3’E, 209–240 m in depth, 28.07.2019, coll. A. Mayorova.

Type locality: Sea of Okhotsk , Bay of Patience, 47°42.5’N, 144°30.3’E, 209–240 m in depth.

External morphology ( Fig. 4A, B ): Body length 24 mm. Max width 10 mm. Body rounded anteriorly and gradually narrowing posteriorly. Rhinophores conical and massive, with 14 lamellae, retractable, rhinophoral sheaths bear 7 spiculate elongated tubercles on their edges. Notum densely covered by long and narrow tubercles bearing long spicules. On dorsal side smaller tubercles also common. 13 multipinnate branchial leaves forming horseshow ring around anal opening, gill cavity absent. Reproductive opening on right anterior side, atrium forming spiral fold. Large oral veil with distinct lateral processes on both sides.

Coloration ( Fig. 4A, B ): Notum uniform milky-white. Foot and head same color as notum. Rhinophores yellowish.

Internal morphology ( Fig. 4C–I ): Spicule complex performed by mono-, di-, and multiaxons. Multiaxons most abundant. Several spicules, especially mono- and diactines may bear minute spines on surface, irregularly placed. Tubercles formed by vertical tracts continuing by stellular tract in upper notal parts, spicule types mixed. Notal edge formed by triactines, which densely packed and oriented by different angles to each other, concatenated by their central short rays.

Buccal pump large, prominent, rounded, with narrow short stalk. Peripheral muscle narrow, covering up to third part of pump width. Radular formula: 32 × 5–6.1.5–6 ( Fig. 5 ). Rachidian tooth rectangular, with vertical folds. Lateral teeth massive, beak-shaped with wide base, its cusp edge bearing 0–7 reduced minute denticles. Marginal teeth triangular, lacking distinct denticles, slightly folded, inner marginal teeth larger than outer.

Reproductive system triaulic ( Fig. 2C). Ampulla narrow, with two distinct folds. Penial sheath massive, large, convoluted. Vas deferens moderate in length, highly convoluted, prostatic part indistinct. Vagina massive, slightly narrowing to seminal receptacle region. Bursa copulatrix rounded, distinct, connecting to middle vagina part by short duct.

Molecular data: This species forms a derived singleton on the Onchidorididae phylogenetic trees ( Fig. 6) with a highly supported (PP = 1; BS = 85) sister relationship with Adalaria slavi Martynov, Korshunova, Sanamyan et Sanamyan, 2009 . Although most onchidoridid genera were recovered as monophyletic (i.e. Onchidoris , Atalodoris, Idaliadoris , Acanthodoris , Onchimira ), the genus Adalaria was polyphyletic in both ML and BI analyses. It is arranged into two clades and two singletons with unresolved basal relationships between them and other Onchidorididae genera: (1) Adalaria evincta Millen, 2006 , which recovered sister to the genus Onchidoris (PP = 1, BS = 100), (2) Adalaria slavi Martynov et al., 2009 and A. boussoleana sp. nov. clade (PP = 1; BS = 85), (3) Adalaria loveni (Alder et Hancock, 1862) , A. proxima and A. rossica Martynov et Korshunova, 2017 clade (PP = 1; BS = 91), (4) Adalaria jannae Millen, 1987 .

Distribution: This species is known only from the type locality.

Remarks: Although our analysis shows that the genus Adalaria is likely polyphyletic ( Fig. 6), we have chosen to designate the new species as a member of the genus Adalaria for several reasons. Firstly, the genus is currently accepted as valid with Adalaria loveni as the type species [ Furfaro et al., 2022]. Secondly, Adalaria boussoleana sp. nov. clearly fits the diagnosis of this genus according to the most recent revision of the family Onchidorididae [ Furfaro et al., 2022]: it has rachidian teeth, a large number of marginal teeth, and a boreal distribution. Additionally, the nodal support for deep relationships of Adalaria in our phylogenetic trees is low ( Fig. 6), suggesting that the polyphyly of the genus may not be entirely fully justified. Lastly, our analysis does not include several species of the genus Adalaria , which were recently described from the North-West Pacific ( Adalaria olgae Martynov et al., 2009 , Adalaria ultima Martynov et Korshunova, 2017 , Adalaria neptuni Martynov et Korshunova, 2022 , Adalaria sergeii Martynov et Korshunova, 2022 ). Therefore, we tentatively designate Adalaria boussoleana sp. nov. as a member of the genus Adalaria , recognizing that a comprehensive revision of the genus is warranted with the inclusion of extensive molecular data and increased sampling efforts.

The new species clearly differs from most of species of the genus Adalaria in external morphology due to the presence of narrow and elongated notal tubercles. Adalaria ultima was recently described from Sakhalinsky Bay (Northwestern Sakhalin, the Sea of Okhotsk) and possesses a similar external morphology with elongated narrow spicular tubercles [ Martynov, Korshunova, 2017]. Adalaria boussoleana sp. nov. differs from A. ultima by the radular morphology: the former has 5 triangle and smooth marginal teeth on each side ( Fig. 5E, F ), while the latter has up to 10 elongated marginals bearing curved hooked cusps [ Martynov, Korshunova, 2017]. Also, the lateral teeth of A. ultima are smooth, but in A. boussoleana sp. nov. they possess a single row of reduced denticles ( Fig. 5B ). Adalaria tschuktchica Krause, 1885 and A. rossica from the Chukchi Sea and Franz Josef Land respectively, also possess elongated tubercles, but have more marginal teeth than A. boussoleana sp. nov.: up to 8 in A. tschuktchica and up to 10 in A. rossica . From the latter species A. boussoleana sp. nov. is considerably different in molecular data as these species are placed in different supported clades ( Fig. 6). Adalaria boussoleana sp. nov. radular morphology is similar to “Lamellidoris ” spiculoides Volodchenko, 1941 , which was described from the tidal areas of the Bering Sea [Bering Is., see Volodchenko, 1941b] and subsequently transferred to the genus Adalaria [ Martynov, 2006]. Adalaria spiculoides has 5 triangle marginals and possesses a single row of denticles on the lateral teeth [Volodchenko, 1941b]. Externally A. spiculoides has spiculate elongate and narrow tubercles and thus show many similarities with A. boussoleana sp. nov. However, the reproductive system of A. spiculoides has not been described. Martynov [2006], Millen [2006] and Martynov et al. [2009] suggested A. spiculoides to be a nomen dubium: Martynov [2006] highlighted that specimens from ZIN labelled as “ Archidoris spiculoides (sic!)” collected from the type locality of the species and identified by Volodchenko, belong in fact to the genus Onchidoris . The type material of this species is lost [ Martynov, 2006]. Also, it should be noted that A. spiculoides was described from the intertidal areas and has much smaller body size (up to 11 mm in length), while Adalaria boussoleana sp. nov. was collected from 209–240 m in depth. Finally, in external morphology Adalaria boussoleana sp. nov. possesses well-expressed elongate tubercles on rhinophoral sheaths (similarly to A. tschuktchica ) ( Fig. 4A, E, G ), which are absent in A. spiculoides . Thus, we follow the suggestion by Martynov [2006] and Millen [2006] and consider A. spiculoides as nomen dubium and support A. boussoleana sp. nov. as distinct species. From phylogenetically close A. slavi the new species differs in both external morphology (shape of tubercles) and internal morphology ( A. slavi has up to nine marginal teeth and well-expressed denticles on the lateral teeth).

Etymology: This species is named after French ship “Boussole” commanded by Jean-François de Galaup, Comte de Lapérouse, famous French explorer and leader of the scientific expedition around the world. The Comte de Lapérouse was the first European explorer reaching the northwestern coast of the Sea of Japan (Tataria), western and southern parts of Sakhalin Island. On the 15–16 August 1787 his expedition reached the same locality as the type locality of the new species to the south from the Gulf of Patience.

Figures

FIG.4. External morphology and spicular complex of Adalaria boussoleana sp. nov, holotype MIMB48047.A. Living specimen, dorsal view. B. Living specimen, lateral view from right. C, D, E. Spicular complex, (C) dorsal view, (D) ventral view, (E) lateral view. F. Spicules of ctenidia. G. Spicules of rhinophore in the front part of the body, lateral view. H. Spicules of the stellular tract at the tubercle base, front part of the body.H. Monoaxone spicules.J. Diaxone spicules.K. Multiaxone spicules. Abbreviation: sc = spicules of ctenidia; sf = spicules of foot; sne = spicules of notum edge; srh = spicules of rhinophore; srht = spicules of tubercles on rhinophoral sheath; sst = spicule of stellular tract. Photo credits: A, B. Anastassya Maiorova.

FIG. 5. Radular morphology of Adalaria boussoleana sp. nov., holotype MIMB48047 (SEM). A. Median and anterior radular portion. B. Lateral and inner marginal teeth. C, D. Rachidian teeth. E. Lateral and marginal teeth, posterior radular portion. F. Marginal teeth. Scale bars: A = 100 µm; B, E = 50 µm; C, D, F = 20 µm. РИС. 5. МорфологиЯ радулы Adalaria boussoleana sp. nov., голотип MIMB48047 (СЭМ). A. СреднЯЯ и переднЯЯ часть радулы.B. Латеральные и внутренние маргинальные Зубы.C, D. Центральные Зубы.E. Латеральные и маргинальные Зубы, ЗаднЯЯ часть радулы. F. Маргинальные Зубы.Масштабные линейки:A = 100 µm; B, E = 50 µm; C, D, F = 20 µm.