Marionia Vayssière 1877

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

Genus Marionia Vayssière 1877 ( Figs 3J , 4G , 5G , 6G )

Duvaucelia Risso 1826 , Paris, Levrault, 4: 38.

Type species: Marionia blainvillea Risso 1818 (= Marionia berghii Vayssière 1879 ), by subsequent designation by Vayssière (1879).

Diagnosis: Rachidian tooth tricuspid, smooth. Masticatory border denticulate, denticles sharp, triangular or rounded. Digestive system arrangement cladohepatic, U- or G-shaped.

Morphology: Body slender or broad, length up to 200 mm ( Fig. 3J ). Oral veil bilobed. Four to 18 simple or branched velar processes, with the outermost ones oħen longer. Five to 16 pairs of arborescent gills. Rachidian tooth tricuspid and smooth ( Fig. 4G ). Masticatory borders of the jaws denticulate, with medium-sized (up to 50 µm) denticles with sharp cusps and conical or triangular bases. ODG complex cladohepatic, with the stomach located in the upper region of the posterior ODG complex ( Fig. 5G ). Penis flagelliform ( Fig. 6G ), cylindrical or conical.

Species composition: Marionia abrahamorum , Marionia blainvillea , Marionia cucullata Couthouy 1852 , Marionia chloanthes Bergh 1902 , Marionia echinomuriceae Jensen 1994 , Marionia ghanensis Edmunds and Carmona 2017 , Marionia gemmii , Marionia kinoi , Marionia limceana , Marionia pellucida Eliot 1904 , Marionia pusa Er. Marcus and Ev. Marcus 1968 , Marionia vanira Ev. Marcus and Er. Marcus 1966 and the new species Marionia flani Silva et al. sp. nov. (see description below).

Remarks: The morphological synapomorphies of Marionia within Marioniinae are the smooth tricuspid rachidian tooth ( Fig. 4G ), sharp and triangular or rounded denticles in the masticatory border and a unique arrangement of the cladohepatic digestive system: the stomach and intestine are located above the upper region of the posterior ODG complex, and the entire arrangement is in the shape of a ‘U’ or ‘G’ ( Fig. 5G ).

According to our phylogenetic analyses, Marionia consists of two clades with different geographical compositions: one clade includes the Pacific Marionia kinoi and several Atlantic species, including the type species Marionia blainvillea , whereas the other is comprised of the Atlantic Marionia limceana and many unnamed Pacific species ( Fig. 2 ). The inclusion of Marionia cucullata in the genus is based on a recent phylogenetic hypothesis that shows the species grouped with Marionia blainvillea ( Moles et al. 2021) , as well as on morphological evidence that fits our proposed diagnosis: the G-shaped arrangement of the digestive system and the smooth tricuspid rachidian tooth ( Odhner 1934). Species for which molecular data are not available, namely Marionia chloanthes , Marionia echinomuriceae , Marionia ghanensis , Marionia pellucida , Marionia pusa and Marionia vanira , are included in this genus on the basis of the presence of true stomach plates, the cladohepatic ODG complex and the smooth tricuspid rachidian tooth (Ev. Marcus and Er. Marcus 1966; Er. Marcus and Ev. Marcus 1968; Ev. Marcus 1983, Edmunds and Carmona 2017). Marionia gemmi is the only species of Marionia with smooth masticatory border of the jaw ( Almón et al. 2018).

Figures

Figure 2. Bayesian phylogenetic tree based on the concatenated molecular data (COI + 16S + H3) of Tritoniidae (sensu Odhner 1963). Outgroup taxa are depicted in grey.Tritoniidae genera are independently coloured, and branches with several replicates for each species hypothesis were collapsed for clarity.Names in bold are species which sequences were generated for this study with the number of sequenced specimens showed in brackets. PP are shown right/top and BS leħ/boưom.Unsupported branches are not labelled. Green circles indicate maximum support by both analyses. Solid vertical bars indicate specimens grouped as species entities based on COI dataset. Empty vertical bars indicate the specimens grouped as species based on the 16S dataset.

Figure 3. Representative species of genera of Tritoniidae (with exception of Paratritonia). A, Tritonia hombergii (MNCN15.05/93379) (Portaferry, Ireland); B, Candiella plebeia (MNCN15.05/93393) (Portaferry, Ireland); C, Tritoniopsis elegans (MB28-0045061) (Zavora, Mozambique); D, Tritonidoxa capensis (MNCN15.05/93399) (Scoưburg, South Africa); E, Tritoniella belli (Antarctica); F, Marianina rosea (French Polynesia); G, Myrella challengeriana comb.nov.(Bahía Camarones, Argentina); H, Tochuina gigantea (Agnew Pass, USA); I, Tritonicula khaleesi (MZUSP113165) (Fortaleza, Brazil); J, Marionia cucullata (Golfo Nuevo, Argentina); (K) Marioniopsis levis ‘1’ (MNHNC/ MB28-004895) (Nacala, Mozambique). Photo A and B, courtesy of B. Picton; photo C and K courtesy of Y.Tibiriça; photo D courtesy of V. Fraser; photo E courtesy of M. Caballer; photo F courtesy of G. Rouse; photo G and J, courtesy of N. Baưini; photo H courtesy of S. Thiebaud; photo I by F. Silva.

Figure 4. Scanning electron micrographs of radulae of analysed key species of Tritoniinae and Marioniinae subfam. nov.: A, tricuspid rachidian teeth and differentiated first lateral of Tritonia hombergii (ZMBN 83471); B, tricuspid rachidian teeth and differentiated first lateral with single accessory denticle (circled) of Candiella plebeia (MNCN15.05/93393); C, unicuspid rachidian teeth and undifferentiated first lateral of Tritoniopsis elegans (MNHNC/MB28-004506); D, tricuspid rachidian teeth and differentiated first lateral of Tritonidoxa capensis (MNCN15.05/93399); E, unicuspid rachidian teeth and undifferentiated first lateral of Tochuina gigantea (NHMD-115967); F, tricuspid rachidian teeth and differentiated first lateral with several accessory denticles (circled) of Tritonicula hamnerorum (MNCN15.05/93378); G, tricuspid rachidian teeth and differentiated first lateral of Marionia blainvillea (NHMD115968); Scale bars: A, D, E = 60 μm; B, C = 22 μm; F = 20 μm; G = 110 μm.

Figure 5. Digestive system arrangements of analysed key species of Tritoniinae and Marioniinae subfam. nov., dorsal view: A, Tritonia hombergii (ZMBN 83471); B, Candiella plebeia (MNCN15.05/93393); 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:a, anus; aodg, anterior ODG complex; e, esophagus; i, intestine; odg, ovotestis-digestive gland complex; s, stomach; podg, posterior ODG complex.

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.