Tritoniella Eliot 1907

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 : 465

Tritoniella Eliot 1907 ( Fig. 3E )

Type species: Tritoniella belli Eliot 1907 , by original designation.

Diagnosis: Rhinophore sheath laterally elongated. Dorsal ridge conspicuous. Secondary gills absent: notal margin smooth, serrated or with knobs.

Morphology: Body slightly broad, length up to 80 mm ( Fig. 3E ). Notum smooth or tuberculate. Conspicuous dorsal ridge running from between rhinophores to mid-body length. Oral veil narrow, entire or slightly bilobed. Velar processes absent or differentiated (six to 16 processes). Rhinophore sheath laterally extended. Secondary gills absent. Notal margin smooth, serrated or with knobs. Ratio of jaw/body length: 0.20. Rachidian tooth smooth, tri- or unicuspid. First lateral tooth undifferentiated or slightly differentiated. Masticatory border of jaws denticulate with small tubercles. Cuticular folds present. Bursa copulatrix elongated. Penis conical with distal character (distal ring).

Species composition: Tritoniella belli , Tritoniella gnathodentata Schächinger et al. 2022 , Tritoniella gnocchi Schächinger et al.2022 , Tritoniella heideae Schächinger et al. 2022 , Tritoniella prinzess Schächinger et al. 2022 and Tritoniella schoriesi Schächinger et al. 2022 .

Remarks: Recently, molecular data have confirmed that the type species Tritoniella belli is indeed a complex of species with a high diversity of morphological characters ( Moles et al. 2021, Schächinger et al. 2022). The phylogenetic position of Tritoniella in our analyses varied depending on the composition of the superfamily Proctonotoidea , and a relationship between Tritoniella and other Tritoniinae could only be recovered in the absence of Proctonotoidea ( Figs 1C , 2 ). In this scenario, Tritoniella and Tochuina form a sister-clade (clade B) to the remaining plateless tritoniids (clade A), as previously proposed in molecular studies ( Korshunova and Martynov 2020, Moles et al. 2021). This clade is characterized by adaptations in the oral veil processes and secondary gills, distinct anterior corners of the notum, a distinct notal margin and cuticular folds in the stomach ( MacFarland 1966, Wägele 1989).

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.