Valencinura jambio, Kajihara & Abukawa & Chernyshev, 2022

Kajihara, Hiroshi, Abukawa, Shushi & Chernyshev, Alexei V., 2022, Exploring the basal topology of the heteronemertean tree of life: establishment of a new family, along with turbotaxonomy of Valenciniidae (Nemertea: Pilidiophora: Heteronemertea), Zoological Journal of the Linnean Society 196, pp. 503-548 : 521-522

VALENCINURA JAMBIO SP. NOV.

( FIGS 2D, E , 4D )

Zoobank registration: u r n: l s i d: z o o b a n k. org:act: E998BBEE-F62E-4D2A-9C27-DE7A889056B4.

Material examined: Holotype, ICHUM 6305 , extracted total DNA (no morphological voucher remains); 19 February 2014, dredged at station 3 of the 2 nd JAMBIO Coastal Organism Joint Survey (Nakano etal., 2015), off Misaki, Sagami Bay, Kanagawa (between 35°08′48″N, 139°34′41″E, 87 m depth and 35°08′38″N, 139°34′35″E, 89 m depth), Japan, collected by H. Kajihara.

Sequences: From the holotype: LC178643 , 28S (2104 bp) ; LC178692 , 16S (507 bp) ; LC190964 , COI (476 bp) .

Etymology: The new specific name is a noun in apposition, from the acronym for the Japanese Association for Marine Biology.

Description: Anterior fragment, 2 cm long, 1 mm wide; anteriorly circular in cross-section, anterior 9 mm pure white; posteriorly flattened dorsoventrally, pinkish in colour ( Fig. 2D ); rhynchocoel (or proboscis) yellowish ( Fig. 2E ). Head pointed, not demarcated from body, but pair of transverse cephalic furrows present just anterior to mouth; no secondary furrows. Proboscis pore mid-ventral, opening between cephalic tip and mouth ( Fig. 4D ).

Distribution: Known only from the type locality, Sagami Bay, Japan (present study).

Remarks: Our generic assignment of Valencinura jambio depends almost entirely on the phylogenetic closeness of this taxon to Vu. bahusiensis in our analyses ( Fig. 1 ) and should be regarded as tentative and provisional, because the species could equally likely belong to Valencinia or Valencinina based on internal morphology, data that are lacking for this species. In Valencinia , Valencinina and Valencinura , the proboscis pore is located far posterior to the cephalic tip. At least some species in Valencinia and Valencinura are similar to one another in external appearance. They supposedly differ in the presence (in Valencinura ) or absence (in Valencinia ) of (1) the proboscis inner longitudinal muscles and (2) the body-wall inner circular muscle layer in the foregut region (e.g. Bürger, 1895a; Bergendal, 1902; Senz, 1996). Valencinina and Valencinura are similar in having the proboscis anteroposteriorly differentiated into several regions. These two genera supposedly differ in the frontal organ, which is present in Valencinina but absent in Valencinura , and also in the outer longitudinal muscles in the posterior part of the proboscis, which are present in Valencinura but absent in Valencinina (Bergendal, 1902; Gibson, 1981b). Additional morphological data will be necessary to ascertain the generic affiliation of Vu. jambio .

Valencinura jambio is almost certainly a different species from Valencinura bahusiensis and Valencinura bergendali Senz, 1996 . The uncorrected p -distance for COI between Vu. jambio and Vu. bahusiensis ( GU392026 ; Strand & Sundberg, 2011) is 11.6%, a value considered high enough to indicate interspecific distance within any nemertean genus (cf. Sundberg et al., 2016b). The cephalic furrows seem to be lacking in Vu. bahusiensis , or at least are not as distinct as in Vu. jambio ( Fig. 4C ). In addition, the rhynchocoel and the proboscis are not evident on the dorsal surface of the body in the intestinal region, or at least are not as clearly evident as in Vu. jambio ( Fig. 2E ; cf. Strand et al., 2010: 122, unnumbered fig. with the caption ‘13 × naturlig storlek’).

Information on the external features of living animals and barcode sequences are lacking for Vu. bergendali . Compared to Vu. bergendali , we ventured to establish Vu. jambio on the basis of smaller body diameter (~ 1 mm vs. 2.5 mm in Vu. bergendali ) and geographical separation ( Vu. jambio in Japan; Vu. bergendali in the Adriatic Sea). As the ending of the generic name suggests (-ura, from the Greek οὐρά, ‘tail’), the type species Vu. bahusiensis possesses a caudal cirrus, while Vu. bergendali lacks one. It remains to be determined whether Vu. jambio has a caudal cirrus.

Valencinura jambio differs from all potential members of Valencinia , although the latter genus requires taxonomic study with fresh material. As Corrêa (1956) has pointed out, Valencinia was established without typespecies fixation for the four nominal species Valencinia dubia Quatrefages, 1846 ; Valencinia longirostris Quatrefages, 1846 ; Valencinia ornata Quatrefages, 1846 ; and Valencinia splendida Quatrefages, 1846 . Valencinia dubia (having eyes, and thus differing from Vu. jambio ) was subsequently regarded as species inquirenda ( Bürger, 1904: 78); Vi. ornata was synonymized with Tubulanus superbus ( Kölliker, 1845) ( Bürger, 1904: 13) ; and Vi. splendida was synonymized with Tubulanus polymorphus Renier, 1804 ( Bürger, 1895a: 517) . This left Vi. longirostris as the only species that Friedrich (1936: 34) considered valid, which prompted Corrêa (1956: 204) to designate it as the type species.

Some other nominal species in Valencinia are no longer regarded as congeneric. These include Valencinia annulata Stimpson, 1855 [now Tubulanus annulatus ( Montagu, 1804) ]; Valencinia armandi McIntosh, 1875 (now Carinoma armandi ); Valencinia elegans Stimpson, 1857 (now Tubulanus annulatus ); Valencinia lineformis McIntosh, 1874 (nomen dubium, having eyes); Valencinia phalaerata Gay, 1849 (nomen dubium); and Valencinia rubens Coe, 1895 (now Zygeupolia rubens ) (see: Gibson, 1995: 533–535 for more details).

Hereweelevate Valencinialongirostris var. rava Bürger, 1895a to species rank as Valencinia rava ; rava is an available species-group name in accordance with Article 45.6 of the Code ( ICZN, 1999). Originally established as Valencinia longirostris var. rava from Naples (along with a redescription of Vi. longirostris , also from Naples), this species was later regarded as subspecies Joubinia longirostris rava ( Bürger, 1904: 86) . Recognizing two subspecies in the same locality, however, is not in accord with the modern concept of subspecies ( Mayr, 1982; Monroe, 1982). As opposed to Vi. longirostris (posteriorly pink as in Vu. jambio ), Vi. rava is posteriorly yellowish grey (and is thus different from Vu. jambio ). The species Valencinia blanca Bürger, 1895a has a uniformly white body and, thus, also differs from Vu. jambio . For the three potentially valid species Vi. blanca , Vi. longirostris , and Vi. rava , no earlier researchers (e.g. Quatrefages, 1846; Hubrecht, 1879; Bürger, 1895a; Corrêa, 1956) described cephalic furrows, which are present in Vu. jambio . Indeed, Hubrecht (1879: 208) mentioned, as part of the generic diagnosis, that no cephalic furrows or fissures are present in Valencinia .

Morphologically, Valencinia shares with Cephalomastax an unusual proboscis musculature in which the proboscis nerve lies between the two (inner and outer) longitudinal muscle layers, an arrangement unique in the phylum ( Norenburg, 1993; Chernyshev, 2011a). To the extent that this morphological similarity indicates a close phylogenetic relationship, Valencinia is presumably more closely related to Cephalomastax than to Valencinura , which supports our placement of Vu. jambio in Valencinura rather than in Valencinia , despite their close relationship in our phylogenetic tree ( Fig. 1 ). Valencinura jambio differs from the two species in Valencinina in body colour: Valencinina albula Gibson, 1981b is cream white overall, whereas Valencinina hubrechti Senz, 2001 is uniformly light brown.

Aside from species in Valencinia , Valencinina and Valencinura , Vu. jambio differs in the following features from all other known heteronemerteans lacking horizontal lateral cephalic slits: in habitat (marine) from Apatronemertes , Planolineus and Siolineus (freshwater); in phylogenetic position ( Fig. 1 ) from Baseodiscus , Cephalomastax , Oxypolella , Riserius , Sonnenemertes and Zygeupolia ; in the nature of the cephalic furrows (paired and disjunct) from Oxypolia beaumontiana (continuous, encircling the head; Punnett, 1901); in body colour (anteriorly white; pink in the intestinal region) from Paralineopsis taki (blueish white anteriorly; foregut region pale yellow; intestinal region milky white; Iwata, 1993), Paramicrura borborophila (light beige-brown to pink-brown; Gibson & Sundberg, 1992), Parapolia aurantiaca (bright orange; Coe, 1895), Parapolia grytvikensis (pinkish brown; Wheeler, 1934), Poliopsis lacazei (dark pink; Joubin, 1890) and Pseudobaseodiscus nonsulcatus (light pink; Senz, 1993). Valencinura jambio further differs from Poliopsis in lacking the peculiar dorsal and ventral medial furrows on the head that are present in the latter ( Joubin, 1890).

Figures

Figure 1. Maximum-likelihood (ML) tree showing the phylogenetic relationships among 41 newly sequenced specimens of pilidiophorans (indicated with solid blue circles). Numbers near nodes are support values, ML bootstrap/Bayesian inference (BI) posterior probability. Nodes with yellow triangles are fully supported, with 100% ML bootstrap and 1.00 BI posterior probability. New species names are indicated in bold. Some nodes were polytomous in the BI tree (indicated by hyphens in place of posterior probability values).

Figure 2. A, Eopilidion misakiense gen. et sp. nov., holotype, ICHUM 6303, lateral view, head to the right; B, Oxypolella hiebertae sp. nov., holotype, MIMB 42256; C, Cephalomastax brevis Iwata, 1957, ICHUM 6304; D, E, Valencinura jambio sp. nov., holotype, ICHUM 6305, anterior body fragment (D) and enlargement of intestinal region (E) showing yellowish proboscis (indicated by arrowheads); F, Baseodiscus takakurai Gibson, 1995, ICHUM 6306; G, Baseodiscus profundus sp. nov., holotype, MIMB 42257; H, I, Baseodiscus narusei sp. nov., holotype, ICHUM 6310, anterior end of body, dorsal (H) and ventral (I) views; J, Baseodiscus paracelensis sp. nov., holotype, MIMB 33132; K, Baseodiscus komatsui sp. nov., holotype, NMNS-Ne 1; L, Baseodiscus unicolor Stiasny-Wijnhoff, 1925; M, Baseodiscus giribeti sp. nov., holotype, MCZ IZ-135324; N, Baseodiscus cf. amboinensis (Staub, 1900); O, Baseodiscus hemprichii (Ehrenberg, 1828-1831), specimen from Okinawa, different from any voucher specimens in this study; P, Baseodiscus zebra sp. nov., holotype, RUMF-ZN-00001; Q, Baseodiscus quinquelineatus (Quoy & Gaimard, 1833), ICHUM 6319. Photographs by H. Kajihara (A, C, D, E, F, O), A.V. Chernyshev (B, G, J), T. Naruse (H, I), H. Komatsu (K), G. Giribet (L, M), D. Uyeno (P), and R.Yoshida (Q).

Figure 4. A–C, Eopilidion misakiense gen. et sp. nov., holotype, ICHUM 6303, anterior end of body, ventral view, head to the right (A), frontal view (B), squeezed-slide preparation (C); D, Valencinura jambio sp. nov., holotype, ICHUM 6305, anterior end of body, ventral view. Photos by H. Kajihara.