Tochuina Odhner 1963

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 : 466-467

Tochuina Odhner 1963

( Figs 3H , 4E , 5E , 6E )

Type species: Tochuina gigantea Bergh 1904 , by original designation.

Diagnosis: Large species (up to 300 mm). Oral veil broad, entire with velar processes differentiated or absent. Secondary gills differentiated; numerous short arborescent gills or packed glandular projections. Rachidian tooth unicuspid, first lateral tooth slightly differentiated; several lateral teeth per row.

Morphology: Body broad, length up to 300 mm ( Fig.3H ). Notum tuberculate. Oral veil broad and entire. Velar processes differentiated or absent. Secondary gills differentiated (numerous and short arborescent gills or packed glandular projections). Radula broad. Rachidian tooth unicuspid ( Fig. 4E ), smooth or denticulate. First lateral tooth slightly differentiated from the remaining laterals. Remaining laterals hooked or hamate. Masticatory border of jaws smooth. Stomach with cuticular folds. ODG complex holohepatic ( Fig. 5E ). Bursa copulatrix large with long vaginal duct ( Fig. 6E ). Penis large and conical ( Fig. 6E ).

Species composition: Tochuina gigantea , To. nigritigris and To. nigromaculata (Roginskaya 1984) .

Remarks: The phylogenetic position of Tochuina in our analyses varied depending on the composition of the superfamily Proctonotoidea ( Fig. 1 ). Regardless of the possible relationship with Proctonotoidea , Tochuina is included in Tritoniinae based on the BI and ML analyses ( Figs 1C , 2 ) and morphological evidence (holohepatic ODG complex and absence of stomach plates). Furthermore, the recovered relationship with Tritoniella ( Figs 1C , 2 ) agrees with recent molecular studies ( Korshunova and Martynov 2020, Moles et al. 2021) and is further supported by several morphological characters: adaptations in the oral veil processes and secondary gills, distinct anterior corners of the notum, distinct notal margin and presence of cuticular folds in the stomach.

Figures

Figure 1. Bayesian phylogenetic trees based on the concatenated molecular data (COI + 16S + H3) of Tritoniidae (sensu Odhner 1963) with three distinct outgroup compositions: A, Proctonotoidea including Curnon granulosa (Curnonidae) and Dirona picta (Dironidae); B, Proctonotoidea including Antiopella barbarensis (Janolidae) and Antiopella capensis (Janolidae); C, no Proctonotoidea were included. Outgroup and clades are depicted in grey and Tritoniidae genera are independently coloured. PP are shown right/top and BS leħ/boưom. Unsupported branches are not labelled. Green circles indicate maximum support by both analyses.

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.