Orienthella Korshunova et al. , 2017

Orienthella Korshunova et al., 2017 View in CoL , reinstated

( Figs 1, 2, 13, 18; Table 5)

Korshunova et al. 2017a: 43–4.

Korshunova et al. 2017b: 140.

Type species: Coryphella trilineata O’Donoghue, 1921 .

Diagnosis: Body moderately narrow. Notal edge discontinuous. Cerata in several groups. Rhinophores distinctly annulate in the type, and core Orienthella s.s., and annulate to tuberculate in Orienthella s.l.. Anterior foot corners present. Central teeth with compressed narrow cusp and distinct short denticles in type and closely related sister-species. Lateral teeth denticulated with attenuated process basally. Distal and proximal receptaculum seminis. Vas deferens short, expands into a broad penial sheath with an additional glandular formation, but not as an protruding accessory gland, prostate indistinct. Penis triangular, folded.

Species included: Orienthella trilineata ( O’Donoghue, 1921) comb. nov. (with additional external and radular data; Fig. 18), Orienthella piunca (Marcus Er., 1961) comb. nov. (= Coryphella fisheri MacFarland, 1966 ), Orienthella (?) cooperi ( Cockerell, 1901) comb. nov., Orienthella (?) fogata ( Millen and Hermosillo, 2007) comb. nov., and Orienthella (?) verta ( Marcus, 1970) comb. nov..

Remarks: All Orienthella species constitute a highly-supported clade (PP = 1, BS = 91; Figs. 1, 13), including the separate distinct clades Orienthella trilineata , O. piunca comb. nov., O. cf. verta , O. cooperi , and O. fogata . Uncorrected COI p -distances within the O. trilineata clade are 0–2.3%, and within the O. piunca comb. nov. clade are 0–1.7%. Uncorrected COI p -distances between the O. trilineata and O. piunca comb. nov. clades are 7.9%–9.6%. The genus Orienthella with representative taxon from warmer subtropical-boreal water, or even partly tropical water, is rare for a coryphellid. The genus Orienthella in its precise sense ( Orienthella s.s.), by combination of a discontinuous notal edge, annulate rhinophores, and compressed cusp of the central teeth, well differs from all other coryphellid genera. However, because molecular data are still unavailable or ambiguous and not well-supported by morphological data for several warm-water Coryphellidae , the real taxonomic situation, as a result, may be more complex, with more genera needing to be separated in future (therefore, currently considered ‘ Orienthella s.l. ’). Remarkably, by using finely differentiated genus-level taxonomy when the molecular data were not yet available, in Korshunova et al. (2017a) we accurately predicted the position of at least two species as closely related to the genus Orienthella using only morphological data: namely O. cooperi (original description in Cockerell 1901) and O. fogata (original description in: Millen and Hermosillo 2007) (see Fig. 13, the predicted taxa are indicated by tick marks on the phylogenetic tree). The molecular phylogenetic placement for these two species appeared seven years later in Ekimova et al. (2024) as sister-clade to O. trilineata , O. piunca , and O. cf. verta ( Fig. 13) and, therefore, we fundamentally predicted the position of O. cooperi and O. fogata as close to the proper Orienthella ( Korshunova et al. 2017a) using, exclusively, the fine-scale taxonomic differentiation of the genus Orienthella and other coryphellid genera (see: Korshunova et al. 2017a; detailed Synopsis of all the genera of the family Coryphellidae ; Figs 1, 13; Table 5). However, from a fine-scale taxonomic perspective, the species O. cooperi and O. verta do not match at an absolutely exact scale to the maximally narrowly defined Orienthella with the characters of two closely related species, the type species O. trilineata , and its close sister-species O. piunca , because O. cooperi has irregularly tuberculate, instead of annulate, rhinophores, and for O. verta smooth rhinophores have been reported ( Millen and Hermosillo 2007). However, O. fogata ( Fig. 13), a close sister-species to O. cooperi , also has somewhat irregular annulation on the rhinophores, compared to the distinct annulations in the type species O. trilineata ( Fig. 18C, D). Taking also into consideration some differences in the descriptions of the central teeth of the radula in O. cooperi and O. fogata , it is better to separate a new genus for at least the latter two species in order to make an absolutely precise genus-level unit for this group. We refrain from creating a new genus for O. cooperi and O. fogata in the present article since we do not have our own material to thoroughly study all the morphological details. We also only temporarily include ‘ Coryphella ’ verta Ev. Marcus, 1970 into the the somewhat more broadly understood genus Orienthella ( Fig. 13) due to its inconsistent rhinophoral morphology ( Marcus 1970, Millen and Hamann 2006) and the unavailability of relevant material for checking morphological and molecular data. Only a single COI sequence is present in GenBank, for which no morphological confirmation was obtained from specimens with verified morphology of true O. verta .

However, the original diagnosis of Orienthella inKorshunova et al. (2017a) included both annulate and tuberculate rhinophores, and, therefore, the confirmation of O. cooperi and O. fogata as phylogenetically closely related to the proper genus Orienthella seven years after Korshunova et al. (2017a) ( Fig. 13 predicted taxa indicated by tick marks) definitely demonstrates the high reliability and practical usefulness of the finely differentiated genus-level systematics of the family Coryphellidae . It is also remarkable that even after the addition of novel data, the position of the genus Occidenthella not only did not change, but significantly strengthened since the genus was initially proposed in Korshunova et al. (2017a). The distinctness and obvious differences between the ‘Western Pacific genus’ (noted in the genus name Occidenthella ) and the ‘Eastern Pacific genus’ (noted in the genus name Orienthella ) is now robustly confirmed ( Figs 1, 2, 13). No representatives of Orienthella have yet been discovered in the Western Pacific, and likewise no representatives of Occidenthella have yet been discovered in the Eastern Pacific (Synopsis; Figs 1, 2, 13; Table 5), despite the potential possibility, especially due to anthropogenic transportation.

cerata. M, details of rhinophores. N, radular teeth, anterior part of radula, SEM. O, radular teeth, posterior part of radula, SEM. P, radular teeth, details of posterior part of radula, SEM. Q, jaw, SEM. R, details of masticatory process of jaw, SEM. S, details of masticatory process of jaw, SEM. Portorchardia candela gen. et sp. nov. Paratype KM953 , Port Townsend , Washington, USA ( T –Y) 20 mm length (live). T, living animal on substrate. U, radular teeth, anterior part of radula, SEM. V, radular teeth, posterior part of radula, SEM. W, radular teeth, details of posterior lateral teeth, SEM. X, details of masticatory process of jaw, SEM. Y, details of masticatory process of jaw, SEM. Z, scheme of reproductive system. Scale bars: E, 100 μm; F, 10 μm; G, 100 μm; H, 50 μm; I, 10 μm; N, 50 μm; O, 100 μm; P, 20 μm; Q, 100 μm; R, 20 μm; S, 5 μm; U, 50 μm; V, 20 μm; W, 10 μm; X, 20 μm; Y, 10 μm; Z, 0.5 mm. Photos: Karin Fletcher. SEM Images: Alexander Martynov. Abbreviations: a, ampulla; fgm, female gland mass; p, penis; psh, penial sheath; rsd, receptaculum seminis distal; rsp, receptaculum seminis proximal; vd, vas deferens .

In the present study, we also confirm the heterogeneity within true Orienthella , and along with the type species Orienthella trilineata ( O’Donoghue, 1921) (original description in: O’Donoghue 1921) we have resurrected the sister-species Orienthella piunca (Marcus Er., 1961) comb. nov. (= Coryphella fisheri MacFarland, 1966 ). Both Orienthella trilineata and Orienthella piunca form distinct clades according to the molecular phylogenetic data ( Fig. 1, 13). Morphologically, O. trilineata can be distinguished from O. piunca by its paler coloration in which the orange pigment on the rhinophores and oral tentacles is lacking or insignificant ( O’Donoghue 1921, present study; Fig. 18A–D). In the present study, additional data for the true Orienthella trilineata are presented and the neotype is selected ( Fig. 18A–I). To provide robust taxonomic assessment, neotype KM 1069, 10 mm length (live), for O. trilineata is selected here from Rich Passage, Washington, USA, collected on 16 January 2017 by Karin Fletcher at the depth 20.1 m, from the geographic region close to the type locality in southern part of British Columbia ( Canada) ( O’Donoghue 1921), from essentially same depth range. The external, jaws, and radular characters of the neotype are presented in Figure 18A–I.

Marcus (1961) did not present a description completely consistent with the actual coloration because his study relied mostly on preserved specimens and greatly overstated the rhinophoral variability (also partly due to the usage of preserved specimens); however, otherwise ‘ Coryphella ’ piunca fits into the true Orienthella genus by details of its external morphology, the presence of a compressed cusp of the central teeth, and its reproductive system morphology. MacFarland (1966), though, described coloration for his ‘ C. ’ fisheri (currently considered a synonym of O. trilineata s.l.) as commonly with orange-tipped rhinophores, but he also mentioned some colour variability, and figured central teeth of radula under a lateral view. Instead, Marcus (1961) for the figured specimen of ‘ C. ’ piunca unequivocally presented distinct annulations of rhinophores and compressed cusp of the central teeth. Thus, ‘ C. ’ piunca well corresponds to Orienthella s.s.. Furthermore, despite that Marcus described the coloration of the living animal imprecisely, he clearly mentioned three lines on the body of ‘ C. ’ piunca . Taking into consideration that both Marcus’s (1961) ‘ C. ’ piunca and MacFarland’s (1966) ‘ C. ’ fisheri came from essentially similar type localities in Northern California, and that true O. trilineata has not yet been confirmed for the type localities of both ‘ C. ’ piunca and ‘ C. ’ fisheri ( Fig. 13), the external and internal characters of ‘ C. ’ piunca unambiguously indicate its placement within Orienthella s.s.. Given the precedence of ‘ C. ’ piunca Marcus, 1961 over ‘ C. ’ fisheri MacFarland, 1966 , it is correct to apply the name Orienthella piunca (Marcus Er., 1961) comb. nov. to the former Orienthella wrongly assigned to O. ‘ trilineata ’ with a more southern distribution plus commonly having orange-tipped rhinophores and oral tentacles ( Behrens et al. 2022). ‘ Coryphella ’ fisheri MacFarland, 1966 (original description in: MacFarland 1966), therefore, is a synonym of Orienthella piunca (Marcus Er., 1961) comb. nov..

Such a north–south gradient in distribution with the southern biogeographic boundary of the more northern species around Oregon –Northern California is quite characteristics for several NE Pacific nudibranchs, particularly the pairs Dendronotus robilliardi Korshunova et al., 2016 (northern)– D. albus MacFarland, 1966 (southern) (with a reservation that D. robilliardi and D. albus overlap in their range around the BC– WA regions) and Catriona columbiana (O’Donoghue, 1922) (northern)– Catriona spadix ( MacFarland, 1966) (southern) ( Korshunova et al. 2016, 2022). The latter case is in turn very similar to the distribution of Orienthella trilineata and Orienthella piunca . Therefore, ‘ C. ’ piunca Marcus, 1961 with type localities in Dillon beach and Monterey Bay in Northern California (and its synonym ‘ C. ’ fisheri MacFarland, 1966 from Monterey Bay) is resurrected as Orienthella piunca ( Marcus, 1961) comb. nov., which is sister to the proper Orienthella trilineata ( O’Donoghue, 1921) ( Fig. 13) with a distribution generally from the more southern parts of Alaska to Oregon, but its precise range still need to be investigated. Comparison of the genus Orienthella with all valid, currently included Coryphellidae genera is presented in Table 5.