Candiella Gray 1850
Creators: name: Silva, Felipe De Vasconcelos
name: Pola, Marta
name: Cervera, Juan Lucas
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Nudibranchia
Tritoniidae
Candiella

description: Candiella Gray 1850
(Figs 3B, 4B, 5B, 6B)
Nemocephala Costa 1867, Rc. Accad. Sci. fis. Mat. Napoli, 6: 137.
Type species: Candiella plebeia (G. Johnston 1828) (= Tritonia plebeia G. Johnston 1828), by original designation.
Diagnosis: First lateral tooth with single accessory denticle. Oesophagus long, connected to stomach in lower right part of ODG complex. Prostatic portion of vas deferens conspicuous, located anterior to distal end of penial sheath. Ampulla U-shaped.
Morphology: Body slender, length up to 34 mm (Fig. 3B). Oral veil narrow and entire. Four to eight simple velar processes, with the innermost ones oħen longer. Two to 16 pairs of arborescent gills with digitiform branches. Rachidian tooth tricuspid and smooth with a rectangular to quadrangular base (Fig. 4B). First lateral tooth differentiated with a single sharp accessory denticle on the upper region. Moderate number of lateral teeth (about 10–50 per half row). Ratio jaw/body length: 0.03–0.15. Masticatory border of jaws denticulate, with medium-sized (up to 40 µm) denticles with conical bases and sharp cusps. Cuticular folds absent. Stomach oħen located at boưom right region of ODG complex (Fig. 5B). Gonopore at beginning of one-third of body length, near rhinophores. Anus and nephroproct slightly anterior to middle of body length. Vas deferens has a conspicuous thickened prostatic portion located anterior to distal end of penial sheath (Fig. 6B). Bursa copulatrix pyriform or oval. Penis flagelliform or conical. Ampulla U-shaped (Fig. 6B).
Species composition: Candiella cincta (Pruvot-Fol 1937) comb. nov., Ca. coralliumrubri (Doneddu et al. 2014) comb. nov., Ca. lineata comb. nov., Ca. manicata comb. nov., Ca. odhneri comb. nov., Ca. pallescens Eliot 1906 comb. nov., Ca. plebeia, Ca. striata comb. nov. and Ca. taliartensis Ortea and Moro 2009 comb. nov.
Remarks: We disagree with the taxonomic validity of the name Duvaucelia proposed by Korshunova and Martynov (2020) for the maximum supported clade (PP = 1; BS = 100), which includes several Atlantic-Mediterranean plate-less tritoniids. The type species Duvaucelia gracilis Risso 1826 was synonymized with ‘ Duvaucelia ’ manicata (originally ‘ Tritonia ’ manicata) by Pruvot-Fol (1937) without further explanation. However, Haefelfinger (1963) pointed out that the original description of ‘ Du. ’ gracilis is different from any reported specimen of ‘ Du. ’ manicata: ‘ Du. ’ gracilis is described as a yellowish slug, with light brown shading, olive gills and 25 mm in size. Since 25 mm specimens of ‘ Du. ’ manicata have never been found and the ambiguous description could fit many other species of sea slugs from the Mediterranean, Haefelfinger (1963) hypothesized that the original description of ‘ Du. ’ manicata was probably based on a juvenile of M. blainvillea. This theory was later agreed by Schmekel and Portmann (1982), although they did not formally synonymize these species. We agree with these authors that the original description of ‘ Du. ’ gracilis does not refer to a specimen of ‘ Du. ’ manicata, and we propose the synonym of ‘ Du. ’ gracilis with M. blainvillea instead.Therefore, Duvaucelia is currently not valid and the name Candiella is revived based on the type species Ca. plebeia.
Apart from the diagnostic synapomorphies, Candiella is characterized by small species (up to 34 mm) with an entire oral veil, a smooth and tricuspid rachidian tooth and a moderate number of lateral teeth. The single accessory denticle in the upper part of the first lateral tooth was oħen broken in the specimens examined and may not be easily recognized. This character was previously mentioned only in the original description of Ca. odhneri (Tardy 1963), formerly ‘ Duvaucelia ’ nilsodhneri (Ev. Marcus 1983), whose original specific epithet is restored in this study, as Duvaucelia and Candiella are no longer considered synonyms of Tritonia. All Candiella species. have medium-sized denticles with conical bases and sharp cusps on the masticatory border of the jaw. In the reproductive system, the exact location of the prostatic part varies from species to species, from the proximal end of the vas deferens to closer to (but never at) the distal end of the penis sheath. Despite the high value of the minimum COI distance between species (Table 3), Candiella is predominantly morphologically homogeneous.
Species for which no molecular data are available, namely the Atlantic Ca. pallescens, the Atlantic Ca. taliartensis, the Mediterranean Ca. coralliumrubri and the AtlanticMediterranean Ca. cincta, are included in Candiella based on their internal and external morphology, which consistently fit the proposed diagnosis. In particular, Ca. cincta was originally described as ‘ Tritonia ’ cincta (Pruvot-Fol 1937) and later included in Tritoniopsis due to the similarity of the radular formula, anus position and flagelliform penis with Tritoniopsis (Schmekel and Portmann 1982). However, we do not consider these characters to be consistent with our diagnosis for Tritoniopsis: the rachidian tooth of C. cincta is shaped as an arch, formed by a small plate with five to seven rounded, thin denticles, whereas other Tritoniopsis species have a strong, unicuspid rachidian tooth with a long and sharp central cusp. As for the flagelliform penis and anus position, they are not exclusive to Tritoniopsis and also occur in other tritoniids. Candiella cincta also differs from Tritoniopsis in its external morphology: the species has only two pairs of gills and four pairs of oral veil processes of similar size, whereas Tritoniopsis has at least 14 pairs of gills and nine pairs of veil processes of varying size. Finally, Ca. cincta has a U-shaped ampulla, and the conspicuous prostatic part is located anterior to the base of the penis sheath, which are characteristic of Candiella.
Although Candiella species occur from southern England (Picton and Morrow 1994) to the Atlantic coast of South Africa (Pola and Gosliner 2010), our phylogenetic analyses suggest that the genus is distributed mainly in the Mediterranean. Notably, our phylogenetic, species delimitation and morphological analyses indicate a hidden diversity represented by the pseudocryptic speciation of Ca. manicata forming a species complex of four distinct species (Fig. 2), which will be thoroughly investigated in future studies.
description: Published as part of 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), pp. 445-476 in Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) (Zool. J. Linn. Soc.) 199 (2) on pages 463-464, DOI: 10.1093/zoolinnean/zlad013, http://zenodo.org/record/8432389