Marionia flani Silva et al., 2023

Silva, Felipe De Vasconcelos, Pola, Marta & Cervera, Juan Lucas, 2023, A stomach plate to divide them all: a phylogenetic reassessment of the family Tritoniidae (Nudibranchia: Cladobranchia), Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 199 (2), pp. 445-476 : 468-470

Marionia flani Silva et al. , sp. nov. ( Fig. 7 )

Zoobank registration: urn:lsid:zoobank.org:act:3F2EAFD1-C7F9-450C-B93A-63DB0D27B5A9

Examined material: (MNHNC/MB28-005600): holotype, 70 mm (preserved), dissected and sequenced; ( MNHNC / MB28-005601 ) : paratype, 80 mm (preserved), dissected; ( MNHNC / MB28-005602 ) : paratype, 80 mm (preserved), dissected. All specimens were collected at 84 m depth at Haul 17 (06°28.7´W, 36°16.3´N) in the Gulf of Cádiz , south-western Iberian Peninsula, during campaign ARSA 1110 conducted by the Instituto Español de Oceanografía ( IEO), November 2010 .

Diagnosis: Colour translucent cream with network of irregular white polygons. Ampulla L-shaped. Bursa copulatrix large, folded without clear shape.

External morphology ( Fig. 7A, B ): Body elongated, broad, length up to 80 mm. Colour cream, semi-translucent. Notum smooth, covered by a network of white polygons. White spots present all over the notum, veil, rhinophore sheath and gills; these spots are translucent, except the ones on the rim of the mantle and closer to the foot. Tips of rhinophores and gills are cream-coloured. Mantle broad with an undulated margin. Foot broad, rounded at the anterior region. Mouth located ventrally and anterior to the foot. Rhinophore sheath cylindrical, with smooth margin. Retractable rhinophore club with eight pinnate plumes, divided in to three branches. Oral veil broad and bilobed, with up to 14 simple digitiform processes. Nine to ten pairs of arborescent gills. Gonopore at end one-third of body length on right side, below third pair of gills. Anus in middle of body length, between fourth and fiħh pairs of gills; nephroproct below fourth pair of gills.

Digestivesystem( Fig.7C–G ): Radularformula50×40–10.1.1.1.10– 40 (MNHNC/MB28-005600) and 58 × 41–10.1.1.1.10–41 (MNHNC/MB28-005601). Rachidian tooth broad, tricuspid, with rectangular base ( Fig. 7C ). Central cusp of the rachidian sharp and prominent ( Fig. 7D ). Lateral cusps blunt, broad and slightly square. First lateral tooth differentiated, blunt and broad ( Fig. 7D ). Remaining lateral teeth long, slender and sharp. Jaws broad, with three irregular rows of sharp denticles on the masticatory border ( Fig. 7E ). Jaw/body length ratio of 0.14–0.16. Buccal mass is large and muscular and extroverted in all specimens examined ( Fig. 7A ). Nervous ring surrounds the upper region of the long and broad oesophagus, and a pair of slender salivary glands is visible on the outer wall of the proximal end ( Fig. 7F ). Oesophagus long and broad, with fleshy ridges on the inner walls. It opens into the stomach in the upper part of the posterior ODG complex ( Fig. 7F ). The stomach is a sac whose lower part is covered by the posterior ODG complex. Inside the stomach are 42 stomach plates aưached to the stomach plate belt ( Fig. 7G ). They are blunt, rectangular, whitish at the base and black towards the upper edge, with smaller plates interspersed between the largest without any discernible paưern ( Fig. 7G ). Stomach opens into the large intestine in the upper right region of the ODG complex, which is divided into two distinct lobes (cladohepatic): the larger posterior part fills a large part of the posterior region of the animal, and the smaller anterior part is located between the oesophagus, stomach and intestine ( Fig. 7F ). One ciliated conducting tubule connects the upper region of the stomach to the anterior ODG complex ( Fig. 7F ), and another connects the ventral region to the posterior ODG complex (not shown). Intestine exits the stomach towards the anterior region of the body, turns leħ to surround the anterior ODG complex and turns right before terminating at the anus. The intestine has ridges on the wall and a thick typhlosole. Digestive system is arranged in a U-shape ( Fig. 7F ).

Reproductive system ( Fig. 7H ): Male, female and vaginal openings are in a common atrium. Orange ovotestis covers the surface of the ODG complex and is visible through the semi-skin. Narrow hermaphroditic duct comes from the anterior ODG complex and connects the ovotestis to the middle region of the ampulla. Whitish ampulla is massively folded into two lobes and L-shaped. The lower lobe is larger and has a slightly flaưened proximal end with an internal groove resting on the posterior ODG complex. The upper lobe is smaller. Deferent duct narrow and somewhat long and exits at the distal end of the ampulla. It runs straight until it branches above the female gland into the vas deferens and oviduct over the female gland. Vas deferens is tortuous, with a narrow proximal end that widens towards the distal end until it joins the penial sheath. Penis unarmed and mostly conical with a flagelliform and curved tip. Bursa copulatrix is a large, folded mass without a clear shape; connected to the gonopore by a long and somewhat broad vaginal duct. Albumen gland can be seen in the small female gland mass, opening outwards through a short and narrow female orifice.

Type locality: Haul 17 (06°28.7´W, 36°16.3´N), Gulf of Cádiz , south-western Iberian Peninsula, Atlantic Ocean .

Etymology: Species dedicated to Francisco Javier Casado Garcia, who has always supported the lead author over the years.

Geographical distribution: Marionia flani has only been reported from Gulf of Cádiz, south-western Iberian Peninsula, Atlantic Ocean.

Remarks: The marine fauna of the European coast is probably the best known in the world ( Costello and Wilson 2011), and yet several new species of marine heterobranchs have been discovered in recent years ( Almón et al. 2018; Araújo et al. 2019, 2022; Pola et al. 2019; Martín-Hervás et al. 2020; Paz-Sedano et al. 2022; among others). Part of this phenomenon is due to the development of molecular biology techniques and bioinformatics soħware for phylogenetic studies, which allow researchers to correctly identify previously overlooked and undescribed species. Mariona flani was previously reported as Marionia species ( Silva et al. 2019) or misidentified as its sister-taxon Marionia blainvillea due to its similar size and shape, a phenomenon also reported for Marionia gemmi ( Almón et al. 2018) . These three European species can be distinguished primarily by their colour paưern: Mariona flani is characterized by a translucent cream background with a network of irregular white polygons, while Marionia blainvillea has an orange to pale-pink background with white spots and warts ( Schmekel and Portmann 1982) and Marionia gemmi is cream with scaưered purple and white spots ( Almón et al. 2018). Internally, the animals differ mainly in the radular formula, the stomach plates and the morphology of the reproductive system. The radular formula is smaller in Marionia blainvillea (26 × 21.1.1.1.21; Schmekel and Portmann 1982) than in Marionia gemmi (96 × 100–120.1.1.1.100–120; Almón et al. 2018) and Marionia flani (50–58 × 41–10.1.1.1.10–41). The stomach plates are triangular in Marionia blainvillea ( Schmekel and Portmann 1982) , but rectangular in Marionia gemmi ( Almón et al. 2018) and Marionia flani . As for the reproductive system, the ampulla is elongate and slightly curved in Marionia blainvillea ( Fig. 6G ) but elongate and folded into two lobes in Marionia gemmi ( Almón et al. 2018) and L-shaped in Marionia flani ( Fig. 7H ). The bursa copulatrix of Marionia flani , a large, folded mass without a clear shape, is unique in the genus ( Fig. 7H ). Moreover, the phylogenetic analyses, the species delimitation analyses and the p -distances between representative Atlantic Marionia species. ( Table 4 ) strongly support the hypothesis that Marionia flani is a distinct and previously unknown species of Marionia .

Figures

Figure 6. Reproductive system arrangements of analysed key species of Tritoniinae and Marioniinae subfam. nov., dorsal view:A, Tritonia hombergii (ZMBN 83471); B, Candiella plebeia (ZMBN 83471); C, Tritoniopsis flydis (GR7-DMC00040); D, Tritonidoxa capensis (MNCN15.05/93399); E, Tochuina gigantea (NHMD-115967); F, Tritonicula hamnerorum (MNCN15.05/93378); G, Marionia blainvillea (NHMD115968). Abbreviations: ag, albumen gland; am, ampulla; bc, bursa copulatrix; fo, female opening; fgm, female gland mass; hd, hermaphrodite duct; o, oviduct; p, penis; pp, prostatic portion; ps, penial sheath; v, vagina; vd, vas deferens.

Figure 7. Marionia flani sp. nov., holotype (MNHNC/MB28-005600): A, ‘fresh’ collected specimen with extroverted buccal mass; B, illustration of specimen; C, SEM of half row of radula showing rachidian, first lateral and remaining laterals teeth (MNHNC/MB28-005601); D, SEM of detail of tricuspid rachidian and first lateral teeth (MNHNC/MB28-005601); E, SEM of denticles from masticatory border of the jaws (MNHNC/MB28-005601); F, digestive system arrangement; G, stomach plates aưached to the belt; H, reproductive system. Abbreviations:a, anus; aodg, anterior ODG complex; ag, albumen gland; am, ampulla; bm, buccal mass; bc, bursa copulatrix; cct: ciliated conducting tubules; dd, deferent duct; e, esophagus; fgm, female gland mass; fo, female opening; hd, hermaphrodite duct; hd, hermaphodic duct; i, intestine; ov, oviduct; p, penis; ps, penial sheath; s, stomach; sg, salivary glands; spb, stomach plate belt; podg, posterior ODG complex; v, vagina; vd, vas deferent.Scale bars: A = 13 mm; B = 13.3 mm; C = 1 mm; D = 180 μm; E = 50 μm; F = 8 mm; G = 0.5 mm; H = 0.8 mm. Images A and G by F. Silva.