Taxonomy
Family Janirellidae Menzies, 1956
[Japanese name: Kazari-mizumushi-ka]
Genus Janirella Bonnier, 1896
[New Japanese name: Kazari-mizumushi-zoku]
Janirella scutum sp. nov.
[New Japanese name: Tate-kazari-mizumushi]
https://zoobank.org/NomenclaturalActs/1CC15A80-1C18-4D72-B833-3E98C5B63735
(Figs. 1–4)
Type material. Holotype: male (ICHUM-8836), BL 4.4 mm, western Japan Trench, Station EC4, off Erimo Cape, Hokkaido, Japan, (41º20.79’N, 144º56.46’E to 41º20.52’N, 144º57.30’E), 3,143–3,176 m depth, 3-m beam trawl, 19 August 2020, R/V Shinsei-maru. Paratype: 1 female (ICHUM-8837), BL 5.4 mm, same collection data as for the holotype.
Specimens for DNA sequencing. Holotype male (ICHUM-8836) and paratype female (ICHUM-8837); one male (ICHUM-8838) and one female (ICHUM-8839), same collection data for the holotype.
Diagnosis. Pereonites 2 and 3 each with four dorsal spines. Pleotelson with two anterior pairs of short and one pair of long lateral projections. Posterior projection on pleotelson shorter than pleotelson length.
Description of holotype male. Body (Fig. 1a, b) ovoid, BL = 4.4 mm, body depth about 0.3 times BW, BW 0.48 times BL; cephalothorax to pereonite 3 increasing in width; pereonite 3 (widest body segment) 1.1 times as wide as pereonite 4; pereonites 4 to 7 decreasing in width; pereonite 7 as wide as pleotelson; fine setae sparsely distributed on body segments. Granules (some with seta) present on dorsal surface of cephalothorax and pereonites, dense laterally and sparse dorsally on pereonites; granules (some with seta) covering dorsal surface of pleotelson. Coxa slightly visible dorsally on pereonite 5.
Cephalothorax with pair of tapering lateral projections and pair of small dorsal spines. Rostrum as long as cephalothorax, tip concave, with two distal and two or three short lateral spines. Pereonites all subequal in length, with transverse groove dorsally. Pereonite 1 with pair of anterior dorsolateral spines bearing apical spine-like seta, pair of tapering lateral projections and four dorsal/dorsolateral spines. Pereonites 2–4 each with pair of anterolateral projections, each bearing apical spine-like seta, pair of tapering lateral projections longer than anterolateral projections, and four dorsal/dorsolateral spines. Pereonites 5–7 each with pair of tapering lateral projections and four dorsal/dorsolateral spines. Stylet on ventral side of pereonite 7 (Fig. 1d).
Pleotelson (Fig. 1a–d) with two anterior pairs of short and one posterior pair of long lateral projections each bearing apical spine-like seta, pair of longitudinal grooves, and two dorsal spines; length about 0.8 times as maximum pleotelson width exclusive of lateral projection; posterior projection length about 0.9 times pleotelson length.
Antennula (Fig. 1e) with 9 articles: article 1 rectangular, covered with scales, distally with two BP setae, and some simple setae; article 2 length 0.7 times as article 1 length, distal part with two BP setae and some simple setae; article 3 as long as article 2, with three simple setae ventrodistally; article 4 distinctly shorter than articles 3 and 5, with BP seta distally; article 5 equal in length to article 6; articles 6–9 decreasing in length, each with aesthetasc. Antenna (Fig. 1f, g, g1, g2, g3) long, reaching tip of posterior projection on pleotelson, peduncle articles 3 and 4 covered with scales. Peduncle article 1 trapezoidal; article 2 trapezoidal, slightly longer than article 1, with two short distal setae; article 3 trapezoidal, with one robust and some simple setae dorsodistally and two long simple setae ventrodistally; squama length 0.4 times article 3 length, with two robust setae and simple seta distally; article 4 triangular, with some dorsal and three long ventral simple setae distally; article 5 entirely covered with short simple setae; article 6 length 1.5 times article 5 length, entirely covered with short simple setae. Flagellum with 41 articles; article 1 long, about five times as long as article 2, articles 2–41 equal in length, each article with 1–4 distal simple setae.
Clypeus and labrum (Fig. 2a) smooth. Maxilliped (Fig. 2b) with coxa naked. Epipod tapering distally, beyond palp article 3, covered with circular scales. Endite (Fig. 2b1) distally concave, with row of four broad, fan-shaped serrate setae surrounded simple fine setae; dorsal medial region with numerous fine setae; lateral margins with fine setae; midline margins with three (left) or four (right) coupling hooks. Palp with five articles; article 1 with one lateral and one medial setae; article 2 rectangular, as wide and about three times as long as article 1, with fine lateral setae, five long medial, and several short distal setae; article 3 rectangular, length about 0.7 times article 2 length, with eight distomedial setae and some lateral setae; article 4 slightly shorter and narrower than article 3, with five distomedial, one or two distal, one lateral, and one distolateral simple setae; article 5 narrowest, length about 0.8 times article 4 length, with approximately ten simple setae distally. Left mandible (Fig. 2c) with lacinia mobilis 2 half as wide as incisor, with three teeth and two simple setae distally. Incisor with five teeth. Setal row with nine serrate setae. Molar process about twice as long as incisor, with five teeth and row of simple setae distomedially. Palp articles 1 and 2 subequal in length; article 1 with four long simple setae distally; article 2 with three short serrate setae distolaterally; article 3 with dense rows of stiff and serrate setae on concave and distal margins. Right mandible (Fig. 2d) with incisor bearing five teeth. Setal row with 11 serrate setae. Molar process about twice as long as incisor, with three large and some small teeth and row of some simple setae distolaterally. Palp articles 1 and 2 subequal in length; article 1 with four long simple setae distally; article 2 with three short serrate setae distolaterally; article 3 with dense row of stiff setae and serrate setae on concave margin. Lower lip (Fig. 2e) with large, ovoid outer lobe bearing dense row of fine setae medially; inner lobe small, rounded. Maxilla 1 (Fig. 2f) outer plate with 10 serrate distal setae and distomedial simple setae; inner plate with four long distal simple setae and surrounding short setae. Maxilla 2 (Fig. 2g) with outer and middle lobes subequal in length; inner lobe broader, shorter, rounded distally, with three distal and one distomedial serrate setae, with surrounding simple setae in distal and medial regions; outer lobe flat distally, with three long serrate setae distally, medial row of simple setae, and simple fine setae on lateral margin; middle lobe flat distally, with three long serrate setae distally, two medial rows of simple setae.
Pereopod 1 (Fig. 3a) shorter and more robust than more posterior pereopods, relative lengths (basis : ischum : merus : carpus : propodus : dactylus) 1 : 0.6 : 0.3 : 0.9 : 0.5 : 0.3. Basis length 2.5 times width; basis covered dorsally with tubercles and entirely with fine setae. Ischium as long as wide, covered entirely with fine setae. Merus triangular, length 0.6 times width, with two dorsodistal, one ventrodistal, and one mid-ventral UB setae, and ventral fine setae. Carpus length 2.4 times width; dorsal region with fine setae; ventral region with five simple setae anteriorly, eight UB setae and five simple setae marginally, and UB seta posterodistally. Propodus 2.8 times as long as wide, with several simple setae dorsally, three simple setae dorsodistally, and five UB setae and several simple setae ventrally. Dactylus three times as long as wide, with one dorsodistal and three ventral fine setae, and ventrodistal simple seta; main claw length 0.7 times dactylus length.
Pereopods 2–7 (Figs. 3b–f, 4a, b) similar but variable in number of setae on carpus and propodus. Pereopod 2 (Fig. 3b) relative lengths (basis to dactylus) 1 : 0.6 : 0.3 : 0.8 : 0.7 : 0.4. Basis 3.3 times as long as wide, covered with tubercles dorsally, with dorsoproximal BP seta and dorsolateral UB seta; entirely covered with fine setae. Ischium 2.8 times as long as wide, entirely covered with fine setae. Merus trapezoidal, 1.3 times as long as wide, with two dorsodistal UB setae, and one dorsodistal and several ventral fine setae. Carpus 3.8 times as long as wide; dorsal region with fine setae; ventral region with six UB setae and two simple setae anteriorly, two UB setae marginally, and eight UB and three simple setae posteriorly. Propodus 5.3 times as long as wide, with posterior distal subtriangular lobe; dorsal region with several simple setae; ventral region with four simple setae anteriorly, six UB setae marginally, and four simple setae posteriorly; ventrodistal corner with UB seta and several simple setae. Dactylus four times as long as wide, with one dorsodistal and three ventral fine setae and ventrodistal simple seta; main claw half as long as dactylus. Number and condition of ventral setae on carpus and propodus of pereopods 3–7 summarized in Table 2.
Table 2
Number and condition of ventral setae on the carpus and propodus of pereopods 3–7 for the holotypes of J. scutum sp. nov. and J. spinoscutum sp. nov. P3–7, pereopods 3–7.
| | | Carpus | | | | Propodus | | |
| | | Anterior | Marginal | Posterior | | Anterior | Marginal | Posterior |
| J. scutum sp. nov. | P3 | 8 UB | 8 UB | 1 UB and 5 fine | | 6 fine | 8 UB | 3 fine |
| | P4 | 6 UB and 1 fine | 6 UB and 1 fine | 2 UB and 5 fine | | 6 fine | 7 UB | 3 fine |
| | P5 | 5 UB and 2 fine | 7 UB | 4 UB and 1 fine | | 6 fine | 8 UB | 4 fine |
| | P6 | 3 UB and 3 fine | 10 UB and 1 fine | 3 UB and 3 fine | | 4 fine | 8 UB | 1 UB and 3 fine |
| | P7 | 3 UB and 1 fine | 9 UB | 3 UB | | 3 fine | 8 UB | 2 UB and 2 fine |
| J. spinoscutum sp. nov. | P3 | 6 UB and 6 fine | 10 UB | 1 UB and 1 fine | | 10 fine | 15 UB and 2 fine | 10 fine |
| | P4 | 3 UB and 3 fine | 12 UB | 2 UB and 5 fine | | 8 fine | 17 UB | - |
| | P5 | 5 UB and 5 fine | 14 UB | 1 UB and 2 fine | | 9 fine | 12 UB | 1 fine |
| | P6 | 4 UB and 5 fine | 14 UB | 1 UB and 3 fine | | 6 fine | 12 UB | 1 fine |
| | P7 | 4 UB and 4 fine | 12 UB | 2 UB and 4 fine | | 1 UB and 6 fine | 13 UB | - |
Pleopod 1 (Fig. 4c) 6.2 times as long as wide, with slight dorsolateral projection bearing some scales. Distal region bilobed; inner lobe pointed, overlapping outer lobe at base, with approximately 15 simple setae laterally; outer lobe fringed with fine setae. Pleopod 2 (Fig. 4d) protopod acutely pointed; stylet in retracted position reaching beyond tip of protopod. Pleopod 3 (Fig. 4f) endopod trapezoidal, with five long distal plumose setae; exopod with length 0.8 times endopod length, acutely pointed; lateral and partly medial margins covered with dense fine setae, with relatively long simple seta apically. Pleopod 4 (Fig. 4g) endopod broadly triangular, pointed apically; exopod rhomboidal, with pointed apex bearing long plumose seta. Pleopod 5 (Fig. 4h) ovoid, slightly smaller than pereopod 4 endopod, thickened laterally.
Uropod (Fig. 1h) with two articles; article 1 with some simple distal setae, article 2 length 1.3 times article 1 length, with some simple setae distomedially and broom seta apically.
Description of paratype female. Body ovoid, BL = 5.4 mm, body depth about 0.2 times BW, BW 0.52 times BL, proportionally slightly wider than holotype male, widest at pereonite 3, with numerous granules and spines dorsally, as in male. Cephalothorax, rostrum, pereonites, and pereopods as in male.
Operculum (Fig. 4e) ovoid, length 1.4 times width, apex slightly pointed and distal margin with some fine setae; ventrodistal area with some short setae.
Etymology. The specific name is a singular noun in the nominative case, derived from the Latin scutum (shield), referring to the convex, shield-like, oval body shape.
Janirella spinoscutum sp. nov.
[New Japanese name: Toge-tate-kazari-mizumushi]
https://zoobank.org/NomenclaturalActs/3A6FFF7B-E636-4B23-AE6A-2C0A9CBDB8FB
(Figs. 5–8)
Type material. Holotype: male (ICHUM-8840), BL 6.5 mm, western Japan Trench, Station K5, off Onagawa, Miyagi, Honshu Island, Japan (38º28.98’N, 143º28.24’E to 38º27.51’N, 143º28.74’E), 2893–2886 m depth, 3-m beam trawl, 12 November 2016, R/V Shinsei-maru. Paratypes: one male (ICHUM-8841), BL 6.5 mm, western Japan Trench, Station K7, off Otsuchi, Iwate, Honshu Island, Japan (39º20.00’N, 143º33.20’E to 39º21.21’N, 143º33.33’E), 2928–3024 m depth, 3-m beam trawl, 13 November 2016, R/V Shinsei-maru; one female (ICHUM-8842), BL 5.6 mm, same collection data as for paratype male.
Specimens for DNA sequencing. Holotype male (ICHUM-8840), paratype male (ICHUM-8841), and paratype female (ICHUM-8842); one female (ICHUM-8843), same collection data as for paratypes.
Diagnosis. Pereonites 2 and 3 each with eight dorsal/dorsolateral spines. Pleotelson with two pairs of short anterolateral projections and one pair of longer mid-lateral projections. Posterior projection on pleotelson shorter than pleotelson length.
Description of males, based primarily on holotype. Body (Fig. 5a, b) ovoid, BL = 6.5 mm, body depth about 0.2 times BW, BW 0.48 times BL; cephalothorax to pereonite 3 increasing in width; pereonite 3 (widest body segment) 1.1 times as wide as pereonite 4; pereonite 4 to pleotelson decreasing in width. Coxae slightly visible dorsally on pereonites 2–7.
Cephalothorax with pair of short, wide anterolateral projections lacking setae, pair of tapering lateral projections each bearing apical spine-like seta, and pair of dorsal spines; rostrum as long as cephalothorax, tip concave, with two distal spines, short dorsal spines, and several dorsal fine setae. Pereonites all subequal in length. Pereonite 1 with pair of tapering lateral projections and six dorsal/dorsolateral spines. Pereonites 2 and 3 each with pair of anterolateral projections, pair of tapering lateral projections longer than anterolateral projections, and eight dorsal/dorsolateral spines. Pereonite 4 with pair of anterolateral projections, pair of tapering lateral projections longer than anterolateral projections, and six dorsal/dorsolateral spines. Pereonites 5 and 6 each with pair of tapering lateral projections and six dorsal/dorsolateral spines. Pereonite 7 with pair of tapering lateral projections (left one broken in holotype) and four dorsal/dorsolateral spines. Stylet on ventral side of pereonite 7 (Fig. 5d).
Pleotelson (Fig. 5a–e) with two pairs of short lateral projections anteriorly and one posterior pair of long lateral projections posteriorly each with apical spine-like seta, pair of longitudinal grooves, and eight dorsal/dorsolateral spines; length about 0.8 times longer than maximum pleotelson width (excluding lateral projection); posterior projection length about 0.8 times pleotelson length; granules (some with seta) sparsely distributed on dorsal surface of pleotelson.
Antennula (Fig. 5f) with 12 articles. Article 1 rectangular, with BP seta and some simple setae distally; article 2 half as long as article 1, distally with four BP setae and some simple setae; article 3 as long as article 2; article 4 distinctly shorter than articles 3 and 5; article 5 about 3 times as long as article 4; articles 6–12 decreasing in length, each with aesthetasc; articles 6, 8, and 12 with one, one, and three simple setae, respectively. Antenna (Fig. 5g–i) long, reaching end of pleotelson, peduncle covered with scales. Peduncle article 1 triangular; article 2 trapezoidal, slightly longer than article 1, with some short lateral setae; article 3 trapezoidal, with some simple and some robust setae dorsodistally and some simple setae ventrodistally; squama length 0.4 times article 3 length, with distal fine seta; article 4 trapezoidal, with some short ventrodistal simple setae; article 5 entirely covered with short simple setae; article 6 length 1.3 times article 5 length, entirely covered with short simple setae. Flagellum with 50 articles; each article with 1–4 distal simple setae.
Clypeus and labrum (from paratype ICHUM-8841; Fig. 6a) smooth. Maxillipedal (Fig. 6b) coxa naked. Epipod tapering distally, reaching beyond palp article 3, covered with circular scales, with medial dense fine setae. Endite distally concave, with row of three broad fan-shaped serrate setae surrounded simple fine setae; dorsomedial region with numerous fine setae; medial margin with three coupling hooks. Palp with five articles; article 1 naked; article 2 rectangular, about three times as long as article 1, as wide as article 1, with some fine lateral setae, and eight medial long and several distal setae; article 3 trapezoidal, length about 0.7 times article 2 length, with eight distomedial setae and some lateral setae; article 4 slightly shorter and narrower than article 3, with two distomedial and one distolateral simple setae; article 5 narrowest, length about 0.7 times article 4 length, with four simple setae distally. Left mandible (Fig. 6c, c1, d) with lacinia mobilis one-third as wide as incisor, with five teeth and two simple setae distally. Incisor with six teeth; setal row with approximately 15 serrate setae. Molar process about twice as long as incisor, with row of some simple setae distomedially. Palp articles 1 and 2 subequal in length; article 1 with four long simple setae distally; article 2 without setae; article 3 with dense row of stiff setae and serrate setae on concave and distal margins. Right mandible (from paratype ICHUM-8841; Fig. 6e) with incisor bearing four teeth. Setal row with approximately 12 serrate and two simple setae. Molar process about twice as long incisor, with some small teeth. Palp articles 1 and 2 subequal in length; article 1 with five long simple setae distally; article 2 with two short serrate setae distolaterally; article 3 with dense row of stiff setae and serrate setae on concave and distal margins. Lower lip (Fig. 6f) with large, rounded outer lobe having dense row of fine setae medially, inner lobe small, rounded, with short setal row distomedially. Maxilla 1 (Fig. 6g) outer plate with 11 serrate distal setae, some distomedial simple setae, and dense fine setal row on part of lateral region; inner plate with four long distal simple setae and surrounding short setae. Maxilla 2 (Fig. 6h) with outer and middle lobes subequal in length, inner lobe broader, shorter; outer lobe rounded distally, setae lost during dissection; middle lobe rounded distally, distal and mediolateral margins with row of simple setae; inner lobe rounded distally, with four distal and one distomedial serrate setae and surrounding simple setae on distal and medial margins.
Pereopod 1 (Fig. 7a) shorter and more robust than posterior pereopods, relative lengths ratios (basis to dactylus) about 1 : 0.4 : 0.2 : 0.8 : 0.4 : 0.2. Basis 3.2 times as long as wide, ventrally with some fine setae and dorsoproximal BP seta, covered dorsally with tubercles. Ischium 1.6 times as long as wide, covered entirely with fine setae. Merus triangular, length 0.7 times width, with two dorsodistal, two ventrodistal, and one ventral UB setae and ventral fine setae. Carpus 2.4 times as long as wide; dorsal and dorsodistal regions with fine setae; ventral region with approximately 10 simple setae anteriorly, seven UB setae and some simple setae marginally, and UB seta posterodistally. Propodus twice as long as wide, with some simple setae dorsally, three simple setae dorsodistally, and five UB setae ventrally. Dactylus three times as long as wide, with two dorsodistal and two ventral fine setae; main claw length 0.7 times dactylus length.
Pereopods 2–7 (Figs. 7b–e, 8a, b) similar but variable in number of setae on carpus and propodus. Pereopod 2 (Fig. 7b) relative article lengths (basis to dactylus) 1 : 0.7 : 0.3 : 0.7 : 0.7 : 0.3. Basis 3.5 times as long as wide, covered with tubercles dorsally, two robust (unclear whether UB) setae dorsolaterally, and fine setae over the entirety. Ischium 2.8 times as long as wide, with some fine setae over the entirety. Merus trapezoidal, 1.4 times as long as wide, with two dorsodistal UB setae, and several ventrodistal and several lateral fine setae. Carpus 3.7 times as long as wide; dorsal region with fine setae; ventral region with 10 UB setae and three simple setae anteriorly, 11 UB setae marginally, UB seta and three simple setae posteriorly. Propodus 7.5 times as long as wide, with posterior distal subtriangular lobe; dorsal region with simple setae; ventral region with seven simple setae anteriorly and eight UB setae posteriorly; ventrodistal corner with UB seta. Dactylus four times as long as wide, with three dorsodistal fine setae, ventrodistal simple seta, and three ventrolateral fine setae; main claw length 0.3 times dactylus length. Number and condition of ventral setae on carpus and propodus of pereopods 3–7 summarized in Table 2.
Pleopod 1 (Fig. 8c) six times as long as wide, with slight dorsolateral projection having some scales. Distal region bilobed; inner lobe pointed, overlapping outer lobe at base, with approximately 12 lateral simple setae; outer lobe fringed with fine setae. Pleopod 2 (Fig. 8d, e) protopod acutely pointed; stylet (Fig. 8e) in retracted position extending beyond tip of protopod. Pleopod 3 (Fig. 8f) endopod trapezoidal, with three long distal plumose setae, medial margin partly covered with dense fine setae; exopod with length 0.8 times endopod length, acutely pointed, lateral and part of medial margin covered with dense fine setae, with long simple seta apically. Pleopod 4 (Fig. 8g) endopod broadly oval; exopod trapezoidal, pointed apex with long plumose seta, lateral margin covered with dense fine setae. Pleopod 5 (Fig. 8h) oval, thickened laterally.
Uropod (Fig. 5j) with two articles. Article 1 with some simple distal setae; article 2 with length 0.8 times article 1 length, with one lateral and one apical simple setae.
Description of paratype female. Body ovoid, BL = 5.6 mm, body depth about 0.2 times BW, BW 0.56 times BL, proportionally slightly wider than holotype male; widest at pereonite 3, dorsal spines relatively large, similar in size to those in male but slightly smaller to male. Cephalothorax, rostrum, all pereonites, and pereopods similar to those in male.
Operculum (Fig. 5k) ovoid, length 1.4 times as long as width, apex slightly pointed, and ventrodistal area with some fine setae.
Etymology. The specific name spinoscutum is a compound noun in the nominative case, derived from the Latin spina (spine) and scutum (shield), meaning spiny shield.
We obtained novel partial nucleotide sequences for the COI gene (652 bp) from 20 individuals representing eight Janirella species and two munnopsid species for outgroups (DDBJ/EMBL/GenBank accession numbers LC816599–LC816616, LC833825, LC833826; Table 1). The maximum K2P distance within taxa was 2.0% in J. (Parjanirella) sedecimtuberculata. Our phylogenetic tree (Fig. 9) shows a fully supported Janirella (Parjanirella) clade (approximate Bayesian value [BP] = 1.000; ultrafast bootstrap value [BS] = 100%) embedded within a paraphyletic Janirella (Janirella) group. The Janirella (Parjanirella) clade is the sister group to J. (J.) spinosa + J. (J.) polychaeta, with high nodal support (BP/BS = 1.000/95%). J. (J.) fusiformis, J. (J.) longicauda, and J. (J.) tuberculata clade were moderately supported (BP/BS = 1.000/95%), but no strong support was found among other species. Species of J. (Janirella) did not form an exclusive clade, i.e., J. (Janirella) was not monophyletic in our tree.