Mgueolia almamater Korshunova et al. , 2025

Mgueolia almamater Korshunova et al., 2025

( Figs 1, 10)

Mgueolia almamater Korshunova, Fletcher, Martynov gen. et sp. nov.: Martynov and Korshunova 2025: 27–8, figs F1,F2. urn:lsid:zoobank.org:act:

Holotype: KM980 , L = 19 mm (live), north-western Pacific , Russia, Kurile Islands, Urup Island, stones, 30–40 m depth, 1 September 2022, coll. T. A. Korshunova and A. V. Martynov.

Paratype: KM885 , L = 24 mm (live), north-western Pacific , Russia, Kurile Islands, Urup Island, stones, 30–40 m depth, 27 August 2021, coll . T. A. Korshunova and A . V. Martynov .

Paratype: KM1007 , L = 30 mm (live), north-western Pacific , Russia, Kurile Islands, Urup Island, stones, 30–40 m depth, 21 August 2022, coll . T. A. Korshunova and A . V. Martynov .

Etymology: See above under the genus name.

M, radular teeth, details of posterior part of radula, SEM. N, radular teeth, details of posterior part of radula, SEM. O, radular teeth, details of central posterior tooth, SEM. P, radular teeth, details of lateral posterior tooth, SEM. Q, jaw. R, details of masticatory process of jaw, SEM. S, details of masticatory process of jaw, SEM. T, scheme of reproductive system. Scale bars: K, 300 μm; L, 300 μm; M, 30 μm; N, 30 μm; O, 10 μm; P, 10 μm; Q, 300 μm; R, 30 μm; S. 10 μm; T 0.5 mm. Photos: Tatiana Korshunova. SEM images: Alexander Martynov. Abbreviations: a, ampulla; fgm, female gland mass; hd, hermaphroditic duct; p, penis; pvd, prostatic vas deferens; psh, penial sheath; rsd, receptaculum seminis distal; rsp, receptaculum seminis proximal.

Description

External morphology ( Fig. 10A–J) Body moderately wide. Foot moderately wide, anteriorly oblique with short foot corners. Rhinophores somewhat shorter or similar in size to oral tentacles, peculiarly wrinkled to smooth. Dorsal cerata relatively short, partly elongate, commonly conspicuously swollen, continuously attached to well-defined uninterrupted notal edge without forming clusters. Notal edge narrow but distinct throughout both lateral sides of body. Digestive gland diverticulum fills significant volume of cerata. Anal opening on right side below notal edge close to middle body part, difficult to observe even in living specimens. Reproductive openings on right side. Tail short and pointed, extending only a short distance beyond last cerata.

Colour ( Fig. 10A–J) Background colour whitish with sometimes a little pinkish shadow. Digestive gland diverticula with various shades of reddish-pink, reddish-brown, or salmon coloration. Rhinophores are similar in colour, but somewhat lighter. Oral tentacles whitish to pinkish. Ceratal apices more orange, with shine through whitish cnidosacs. Foot whitish with a little pinkish hue. Pinkish gonad partly shines through the ventral side of the foot.

Jaws ( Fig. 10 Q–S) Jaws oval. Edge of masticatory processes bears up to about 40 or more denticles that may form up to at least eight longitudinal rows of denticles and tubercles from the internal side, diminishing toward the inner part of the jaw. Denticles at the very edge of masticatory processes considerably elongated, narrowing toward the apical parts.

Radula ( Fig. 10 K–P) Radula formula 32 × 1.1.1. General pattern of radula remarkably similar to family Eubranchidae , with narrow cusp of central teeth significantly compressed by adjacent lateral denticles and almost smooth to slightly denticulated lateral teeth with strong broad ventro-lateral bases. Up to at least seven distinct lateral denticles on central teeth. Lateral teeth smooth to slightly denticulated with at least up to five slight serrations/reduced denticles on some teeth.

Reproductive system ( Fig. 10T) Hermaphroditic duct leads to moderately long, thick, convoluted ampulla of few whorls. Vas deferens long, relatively narrow, no distinct prostate. Penial sheath elongated. Penis elongated conical. Oviduct connects through insemination duct into female gland complex. Both distal and proximal receptaculum seminis detected, somewhat rounded, similar in size, almost sessile, on very short stalks.

Ecology: Shallow water, upper subtidal, stony environment.

Distribution: So far discovered only at the Urup Island, Kurile Island, in NW Pacific.

Remarks: Hereindetaileddescriptionandmoleculardata( Figs1, 2, 10) are for the first time provided. All three Mgueolia almamater formed a maximally supported clade (PP = 1, BS = 100) within the family Paracoryphellidae clade. Uncorrected COI p -distance within the M. almamater clade is 0–0.3%. The COI minimal uncorrected p -distance of 12.7% was found between the M. almamater clade and Ziminella salmonacea . For more see above under the genus name.

Family Flabellinidae Bergh, 1889 View in CoL

( Figs 1, 2, 5C, 12; Table 4)

Subfam. Flabellininae Bergh 1889: 215.

‘Genus Flabellina sensu latissimo ’ Gosliner and Griffiths 1981: 105 , 109–15.

Family Flabellinidae View in CoL in restricted sense, Korshunova et al. 2017a: 44.

Diagnosis: Body moderately narrow. Notal edge discontinuous or completely reduced. Cerata in separate clusters, on elevations or distinct stalks. Rhinophores smooth, annulate, or papillate. Anus mixed (pleuroproctic in higher acleioproctic position) or pleuroproctic. Elaborate oral glands present, commonly penetrate below anterior cerata. Masticatory edges of jaws with several rows of compound, sharpened or tubercle-like denticles. Radula formula 1.1.1. Central teeth usually with compressed cusp by adjacent lateral denticles. Lateral teeth with attenuated process basally, usually denticulated, rarely smooth. Number and position of receptaculum seminis variable: two separate ones, or double proximal and single distal, or double distal one, in few cases a proximal receptaculum is not evident. Vas deferens usually long, with indistinct prostate, more rarely short. Accessory gland absent. Massive external permanent penial collar absent. Penis internal, usually elongated conical, narrow, unarmed.

Genera included: Calmella Eliot, 1910 , Carronella Korshunova et al., 2017 , Coryphellina O’Donoghue, 1929 , Edmundsella Korshunova et al., 2017 , Flabellina Gray, 1833 in Griffith and Pidgeon, 1833–34, and Paraflabellina Korshunova et al., 2017 .

Remarks: The family Flabellinidae proper, after moving morphologically and molecularly highly heterogenous diversity into at least six separate families ( Korshunova et al. 2017a, present study) placed in four different distantly related superfamilies Samloidea , Apataoidea , Flabellinopsoidea , and Flabellinoidea ( Figs 1, 2) represents a well-diagnosed fine-scale taxonomic unit, externally characterized by notal edge usually modified into some low stalk- or elevation-like clusters (genera Carronella , Coryphellina , and Calmella ) or into some very distinct, high stalks as in the proper genus Flabellina . Internally, the taxa of the family Flabellinidae commonly possess a compressed cusp of the central teeth and a long to moderate vas deferens, but not commonly as short as in the family Coryphellidae .