Rhombonemertes rublinea, Hookabe & Moritaki & Jimi & Ueshima, 2022

Hookabe, Natsumi, Moritaki, Takeya, Jimi, Naoto & Ueshima, Rei, 2022, A new oerstediid discovered from wood falls in the Sea of Kumano, Japan: Description of Rhombonemertes rublinea gen. et sp. nov. (Nemertea: Eumonostilifera), Zoologischer Anzeiger 301, pp. 154-162 : 156-157

publication ID

https://doi.org/ 10.1016/j.jcz.2022.10.003

persistent identifier

https://treatment.plazi.org/id/AE6187FD-FFAB-FF88-FFD2-FBC77D94FB3A

treatment provided by

Felipe

scientific name

Rhombonemertes rublinea
status

gen. et sp. nov.

3.2. Rhombonemertes rublinea gen. et sp. nov.

[New Japanese name: hishimochi-himomushi]

Material examined. Holotype: NSMT-Ne-003, unsectioned complete specimen except for the posterior tip, fixed in Bouin’ s fluid and later preserved in 70% ethanol, posterior tip preserved in 99% ethanol, male, collected on January 10 2022 by NJ, at depths of 150–200 m, off Owase (approx. 34 ◦ 06 ′ 49.0 ′′ N, 136 ◦ 30 ′ 35.0 ′′ E), the Sea of Kumano , Japan, NW Pacific. Paratype: NMST-Ne-004, serial transverse sections from anterior tip to intestinal region (6 slides), everted proboscis (5 slides), and serial frontal sections of intestinal region (5 slides), posterior tip used for DNA extraction, rest of body fixed in Bouin’ s fluid and later preserved in 70% ethanol, female, collected on February 7 2022 by TM, at depths of 150 m, off Kumano (33 ◦ 52 ′ 18.4 ′′ N, 136 ◦ 11 ′ 54.8 ′′ E), the Sea of Kumano, Japan, NW Pacific GoogleMaps .

Diagnosis. Same as for generic diagnosis.

Description. External morphology: body 0.8 cm in length and 0.1 cm in width in male (holotype); 3.2 cm in length and 0.7 cm in width in female (paratype) ( Fig. 2A View Fig ); single median brownish-red stripe extending from transverse band in head region to posterior tip of body ( Fig. 2A, D View Fig ). Four eyes present ( Fig. 2B, D View Fig ). Head demarcated from body, anteriorly pointed, and diamond shaped ( Fig. 2A View Fig ); brownish-red-colored transverse band present between head and trunk (= dorsally between anterior and posterior cephalic furrows ( Fig. 2B View Fig ) while ventrally overlapped with posterior cephalic furrows ( Fig. 2C View Fig )). Anterior cephalic furrows not meeting mid-dorsally, each slightly curving posteriorly in lateral margin ( Fig. 2B View Fig ); ventrally transverse, meeting at mid-line without reaching to proboscis pore ( Fig. 2C View Fig ). Posterior cephalic furrows meeting at mid-line both dorsally ( Fig. 2B View Fig ) and ventrally ( Fig. 2C View Fig ); gently V-shaped in dorsal surface ( Fig. 2B View Fig ) and steeply A-shaped in ventral surface ( Fig. 2C View Fig ). Blood not red, probably uncolored. Cerebral ganglia red colored in squeezed preparation ( Fig. 2D View Fig ), laterally leading from cerebral organs via cerebral canals ( Fig. 2E View Fig ). Intestinal caecum with lateral diverticula, anteriorly not reaching cerebral ganglia ( Fig. 2D View Fig ); lateral diverticula of intestinal caecum and intestinal diverticula deeply branched ( Fig. 2D View Fig ). Pinkish ovary or pale testes visible thorough body wall ( Fig. 2A View Fig ).

Internal morphology: Internal morphology. Epithelium 45–60 μm thick, with red-stained acidophilic gland cells in precerebal region ( Fig. 3A View Fig ) and with yellow- and red-stained gland cells in foregut region ( Fig. 3B View Fig ). Dermis up to 20 μm, cup-shaped in precerebal region ( Fig. 3A View Fig ) and flattened in foregut region ( Fig. 3B View Fig ). Cephalic glands anteriorly with red-stained acidophilic cells ( Fig. 3D and E View Fig ) and posteriorly replaced with blue-stained basophilic cells ( Fig. 3G View Fig ). Body-wall musculature with outer longitudinal and inner circular muscles ( Fig. 3A and B View Fig ). Some diagonal muscle fibers present as a lattice between outer circular and inner longitudinal muscle layers ( Fig. 3C View Fig ). Dorsoventral muscles present between intestinal diverticula ( Fig. 3L View Fig ). Precerebral vessel bifurcated ( Fig. 3E and F View Fig ). Mid-dorsal vessel without protruding into rhynchocoel ( Fig. 3H View Fig ). Oesphagus short, replaced with stomach in precerebral region (around cerebral organ opening) ( Fig. 4 View Fig ); stomach with ciliated cells, well-developed basophilic glands, and acidophilic glands ( Fig. 3G View Fig ). Intestinal caecum developed beneath pylorus, 2 or 3 pairs of lateral diverticula deeply branched, not reaching brain region anteriorly ( Fig. 3G View Fig ).

Proboscis pore subterminal, opening ventrally ( Fig. 2B View Fig ). Rhynchocoel short, less than half of body length ( Fig. 2D View Fig ). Rhynchocoel musculature with outer circular and inner longitudinal muscles ( Fig. 3L View Fig ). Proboscis epithelium with developed papillae up to 70 μm thick, basophilic, and acidophilic glands ( Fig. 3I View Fig ); outer circular, middle longitudinal, and inner circular muscles ( Fig. 3I View Fig ); 8 proboscis nerves ( Fig. 3I View Fig ). Stylet basis oval, 22 μm in length and 13.0 μm in maximum width; central stylet smooth, 26.4 μm in length; stylet-to-basis-length ratio 1.20 ( Fig. 2E View Fig ). Two accessory stylet pouches present, each containing 2–3 stylets.

A single frontal organ present ( Fig. 3D View Fig ). Cerebral organs opening ventrolaterally; cerebral canals without branching and replaced with acidophilic glands anterior to precerebral septum ( Fig. 4 View Fig ). Brain with outer neurilemma ( Fig. 3J View Fig ); glomerular structures present in dorsal cerebral ganglia ( Fig. 3J View Fig ). Lateral nerves without accessory nerves ( Fig. 3K View Fig ).

Nephridial tubules convoluted and opening dorsolaterally at intestinal caecum ( Fig. 3K View Fig ). Each ovary containing as many as 10 oocytes; each oocyte containing a germinal vesicle; oocyte 150–200 μm in diameter ( Fig. 3L and M View Fig ).

Etymology. The specific name is derived from a composite of the Latin ruber (= red coloured) + linea (= line), referring to the mid-dorsal stripe of the present species.

Type locality and distribution. The present species was found from the type locality, off Owase to Kumano, the Sea of Kumano, Japan .

2. Molecular phylogeny and interspecific genetic distances

Our molecular phylogenetic analyses indicated that R. rublinea gen. et sp. nov. constituted a clade together with Monostilifera sp. Genroku Seamount collected from a gentle slope of Genroku Seamount at a depth of 2084 m along the Nishi-Shichito ridge, Japan, with 72% bootstrap value and 0.99 posterior probability ( Fig. 5 View Fig ). Although R. rublinea appeared to be included in the clade formed by Eumonostilifera sp. Vema2B (Vema Fracture Zone), Monostilifera sp. Genroku Seamount ( Japan), Kurilonemertes dilutebasisae ( Kulikova, 1987) , Kurilonemertes papilliformis ( Korotkevitsch, 1977) ( Russia), Kurilonemertes phyllospadicola ( Stricker, 1985) ( Canada), Pseudotetrastemma sp. ( Russia), and Tetrastemma bilineatum Coe, 1904 ( USA), phylogenetic relationships within the clade were not well resolved except for monophyly of Kurilonemertes Chernyshev, 1993 .

An uncorrected p- distance based on 635 bp of COI was 11.9% between R. rublinea gen. et sp. nov. and Monostilifera sp. Genroku Seamount.

TM

Teylers Museum, Paleontologische

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