Chondrochelia sp.

Sato, Akari, Arakawa, Kazuharu & Kakui, Keiichi, 2023, Two new species in Leptocheliidae (Crustacea: Peracarida: Tanaidacea) from Japan, with notes on their phylogenetic position and aspects of morphology, Zoologischer Anzeiger (Zool. Anz.) 306, pp. 51-68 : 54-64

Chondrochelia sp. : Kakui et al., 2021.

3.1.1.1. Type material. See Table 1.

3.1.1.2. Etymology. This specific name sublitoralis (Latin: sublittoral) is an adjective referring to collection of this species from the sublittoral zone.

3.1.1.3. Diagnosis. Female: in antennules, combined length of articles 3 and succeeding article(s) at least 1.5 times as long as article 2 (1.56–1.82 times in type series); maxillipedal palp articles 2 and 4 each with outer seta; cheliped slender, having carpus with parallel dorsal and ventral margins and length at least two times width (2.54–3.27 times in type series), with merus bearing inner simple seta and carpus bearing two dorsal simple setae; carpus of pereopods 4–6 with three ventral spiniform setae; protopod of pleopods 1–5 with inner plumose setae. Male: propodus of pereopod 1 without ventrodistal spiniform setae; uropodal exopod uniarticulate.

3.1.1.4. Description of female, based on holotype. Body ( Figs. 1A, B and 2A, B ) slightly dorsoventrally flattened, 7.95 times as long as CW, translucent, slightly yellowish when alive ( Fig. 1A and B ). Cephalothorax ovate, 0.19 times as long as BL, 1.55 times as long as wide, with two pairs of lateral simple setae posterior to eye and pair of mid-lateral simple setae; anterodorsal region orangish in living animal ( Fig. 1A ); second thoracomere demarcated dorsally on carapace ( Fig. 7C ); eyes well developed, pigmented, dark brown in living animal ( Fig. 1B ). Pereon 0.19 times as long as BL. Pereonites 1–6 with length ratio 1.00: 1.55: 1.52: 1.75: 1.61: 1.40; pereonite 1 with pair of lateral setae in anterior region and another pair in posterior region; pereonites 2, 4–6 with pair of lateral setae; pereonite 3 without setae. Pleon 0.19 times as long as BL. Pleonites as wide as pereonite 6; all wider than long, similar in shape; pleonites 1–4 with pair of lateral setae, pleonite 5 with two pairs of lateral setae. Pleotelson ( Fig. 2C ) 0.52 times as long as wide, narrower than pleonite 5, trapezoid in dorsal view ( Fig. 2C ), with pair of lateral setae and two pairs of posterior setae.

Antennule ( Fig. 3A ) with five articles (article 5 cap-like), slender, 7.12 times as long as wide, 1.08 times as long as cephalothorax; articles 1–5 with length ratio 1.00: 0.23: 0.22: 0.20: 0.04. Article 1 with one mid-outer, one mid-ventral, one outer distal, and one inner distal simple setae; two proximal, four mid-outer, and four distal PSS; and several inner-proximal setae. Article 2 with one outer distal and one inner distal simple setae, and one inner PSS. Article 3 naked. Article 4 with one simple seta and one PSS in distal region. Article 5 with three distal simple setae and one distal PSS.

Antenna ( Fig. 4A ) 0.70 times as long as antennule, with six articles; articles 1–6 with length ratio 1.00: 1.30: 0.87: 2.96: 1.63: 0.20. Article 1 with one ventrodistal seta. Article 2 with one dorsodistal and one ventrodistal spiniform setae and one dorso-subdistal simple seta. Article 3 with dorsodistal spiniform seta. Article 4 with one mid-inner and three distal simple setae (shorter than article-4 length) and several PSS. Article 5 with two distal simple setae and one PSS. Article 6 with five distal simple setae.

Labrum ( Fig. 4B ) not projecting anteriorly, setulate. Mandibles ( Fig. 4C and D ) with molar well developed; masticatory region broad. Incisor of left mandible ( Fig. 4C ) with six small teeth; lacinia mobilis with four small and one large teeth; incisor process with six small teeth. Incisor of right mandible ( Fig. 4D ) bifurcate distally, with anterior subdistal crenulation. Labium ( Fig. 4E ) bilobed; inner and outer lobes setulate. Maxillule ( Fig. 4F and G ) with setulate endite bearing 11 distal spines; palp ending in two long simple setae. Maxilla lost during dissection. Maxillipeds ( Fig. 4H ) with bases not fused medially, both bearing four simple setae at insertion of palp. Endites ( Fig. 4J ) not fused medially, reaching distal margin of palp article 1, each with outer distal long simple seta, three distal flat spiniform setae (two longer and one shorter, relatively rounded), two inner distal coupling hooks, and two outer distal setulations. Palp ( Fig. 4I ) article 1 naked; article 2 with one outer short and four inner long distal setae; article 3 with eight inner simple setae; article 4 with one outer and ten distal simple setae. Epignath ( Fig. 4K ) elongate, slender, setulate.

Cheliped ( Fig. 4L ) chelate, with triangular articulation with cephalothorax via sclerite; sclerite with simple seta. Basis 1.69 times as long as wide, with free posterior portion and outer simple seta. Merus with three ventral and one inner simple setae. Carpus 2.54 times as long as wide, longer than basis, with two dorsal and three ventro-subdistal simple setae; outer ventrodistal margin not extending as cuff over proximal region of propodus. Propodal palm with simple seta at insertion of dactylus and inner comb-row of six setae ( Fig. 4M and N ). Fixed finger with three dorsal and four ventral simple setae, and cone shaped claw. Dactylus and unguis fused to claw, as long as fixed finger; dactylus with inner proximal simple setae.

Pereopods 1–6 cylindrical, with length ratio 1.00: 0.55: 0.50: 0.56: 0.55: 0.58. Pereopod 1 ( Fig. 5A ) 0.31 times as long as BL, with length ratio of articles from basis to dactylus-unguis 1.00: 0.05: 0.33: 0.34: 0.64: 0.95. Coxa with simple seta. Basis slightly arched, 5.09 times as long as wide, with dorsoproximal simple seta. Ischium wider than long, with ventral simple seta. Merus 1.76 times as long as wide, with ventrodistal short simple seta. Carpus 1.81 times as long as wide, with five distal simple setae. Propodus 4.80 times as long as wide, with three dorso-subdistal and one ventro-subdistal simple setae. Dactylus with proximal simple seta. Unguis 0.73 times as long as dactylus, naked. Pereopod 2 ( Fig. 5B ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.07: 0.36: 0.37: 0.52: 0.17. Coxa with simple seta. Basis cylindrical, 3.95 times as long as wide, with dorsoproximal simple seta and two PSS. Ischium wider than long, with one ventral simple seta. Merus 1.76 times as long as wide, with ventrodistal simple seta and ventrodistal spiniform seta. Carpus 2.07 times as long as wide, with one dorsodistal and one ventrodistal simple setae and two ventrodistal spiniform setae. Propodus 3.91 times as long as wide, with four dorso-subdistal simple setae and ventrodistal spiniform seta. Dactylus with simple proximal seta. Unguis 0.40 times as long as dactylus, naked. Pereopod 3 ( Fig. 5C ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.07: 0.31: 0.35: 0.58: 0.14; similar to pereopod 2, except basis with one proximodorsal PSS and propodus with three dorso-subdistal setae. Pereopod 4 ( Fig. 5D ) lacking coxa, with length ratio of articles from basis to dactylus-unguis 1.00: 0.06: 0.36: 0.35: 0.44: 0.33. Basis thick, 2.59 times as long as wide, with three dorsal and one ventral PSS. Ischium wider than long, with two ventral simple setae. Merus 2.11 times as long as wide, with two ventrodistal spiniform setae. Carpus 1.95 times as long as wide, with two dorsodistal simple setae and three ventrodistal spiniform setae. Propodus 3.69 times as long as wide, with five dorsodistal simple setae, dorsodistal serrated spiniform seta, and two ventro-subdistal spiniform setae. Dactylus naked. Unguis 0.33 times as long as dactylus, naked. Pereopod 5 ( Fig. 5E ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.09: 0.43: 0.44: 0.36: 0.27; similar to pereopod 4, except basis with ventral simple seta and two ventral PSS. Pereopod 6 ( Fig. 5F ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.04: 0.36: 0.37: 0.37: 0.30; similar to pereopod 4, except basis with one dorsal PSS and ventral simple setae, carpus with distal simple seta, and propodus with seven serrated spiniform setae and four simple setae.

Pleopods five pairs, all similar. Pleopod 1 ( Fig. 5G and H ) protopod with inner plumose seta. Exopod with vestigial proximal article bearing ventral plumose seta; remaining portion with 25 outer plumose setae. Endopod with one inner-subdistal, 13 outer plumose setae, and outer distal step-tipped plumose seta. Setal numbers/conditions in pleopods 2–5 summarized in Supplementary Material 3.

Uropod ( Fig. 5I ) with naked protopod. Endopod with five articles; article 1 with simple seta; article 2 with two distal simple setae and distal PSS; article 3 with distal simple seta; article 4 with one distal simple seta; article 5 with one middle and three distal simple setae. Exopod uniarticulate, shorter than endopodal article 1, with one middle and two distal simple setae.

3.1.1.5. Description of male, based on allotype. Body ( Figs. 1C and D , 2D, E ) slightly dorsoventrally flattened, 6.19 times as long as CW, translucent, slightly yellowish in living animal ( Fig. 1C and D ). Cephalothorax ovate in outline, 0.20 times as long as BL, 1.25 times as long as wide, with pair of mid-lateral simple setae; anterodorsal region orangish in living animal ( Fig. 1C ); second thoracomere not demarcated dorsally on carapace; eyes well developed, pigmented, dark brown in living animal. Pereon 0.52 times as long as BL. Pereonites 1–6, with length ratio 1.00: 1.31: 1.64: 2.20: 1.92: 1.64; all wider than long; pereonites 1–3 with pair of lateral setae in anterior region and another pair in posterior region; pereonites 4–6 with two pairs of lateral setae. Pleon 0.28 times as long as BL. Pleonites as wide as pereonite 6; all wider than long, similar in shape; all with pair of lateral setae. Pleotelson ( Fig. 2F ) 0.43 times as long as wide, narrower than pleonite 5, pentangular in dorsal view, with two pairs of posterior setae.

Antennule ( Fig. 3C ) with 12 articles, 1.67 times as long as cephalothorax; articles 1–12 with length ratio 1.00: 0.39: 0.14: 0.12: 0.12: 0.13: 0.11: 0.12: 0.10: 0.09: 0.02: 0.01. Article 1 with one outer distal and one inner distal setae, and three outer distal PSS. Article 2 with one mid-inner and one distal simple setae, and four distal PSS. Article 3 with one distal simple seta and one PSS. Article 4 with two ventral rows of aesthetascs. Articles 5–10 each with ventral row of aesthetascs. Article 11 with one distal simple seta and two aesthetascs. Article 12 with two distal simple setae.

Antenna ( Fig. 6A ) 0.46 times as long as antennule, with six articles; articles 1–6 with length ratio 1.00: 1.16: 0.79: 3.11: 2.58: 0.32. Article 1 naked. Articles 2–6 similar to those of female; spiniform setae on article 2 thinner than females; simple setae on article 4 longer than article-4 length.

Maxillule with two distal setae ( Fig. 6B ). Maxillipedal endite lacking, palp lacking.

Cheliped ( Fig. 6C and D ) chelate, with triangular articulation with cephalothorax via sclerite; sclerite with simple seta. Basis 1.19 times as long as wide, with one outer seta. Merus with three ventral and one inner simple setae. Carpus slender, 4.74 times as long as wide, longer than basis, with three dorsal and three ventrodistal simple setae; outer ventrodistal margin extending as cuff over proximal region of propodus. Propodus also slender, as long as carpus. Propodal palm with outer simple seta at insertion of dactylus, and inner comb-row of 21 setae; comb-row almost parallel with dorsal margin of propodal palm. Fixed finger robust, width of region between two apophyses 0.83 times width of base of fixed finger, with two dorsal apophyses and three ventral and three dorsal simple setae (one of three ventral setae broken). Dactylus and unguis fused to claw, nearly as long as fixed finger, with inner proximal simple seta and eight ventral spiniform setae.

Pereopods 1–6 cylindrical, with length ratio 1.00: 0.59: 0.52: 0.67: 0.64: 0.61. Pereopod 1 ( Fig. 6E ) 0.46 times as long as BL, with length ratio of basis, ischium, merus, carpus, propodus, and dactylus-unguis 1.00: 0.06: 0.35: 0.36: 0.69: 0.71. Setation on coxa, ischium, carpus, propodus, and dactylus-unguis similar to that in female. Basis cylindrical, narrow, 5.76 times as long as wide, with dorsoproximal simple seta and PSS. Ischium wider than long. Merus 2.97 times as long as wide, with dorsodistal and inner distal simple setae. Carpus 3.11 times as long as wide. Propodus 8.22 times as long as wide. Unguis 0.69 times as long as dactylus. Pereopod 2 ( Fig. 6F ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.08: 0.34: 0.33: 0.57: 0.32. Setation of articles from coxa to dactylus-unguis similar to that in female. Basis cylindrical, 5.58 times as long as wide. Ischium wider than long. Merus 2.40 times as long as wide. Carpus 2.19 times as long as wide. Propodus 5.45 times as long as wide. Unguis 0.79 times as long as dactylus. Pereopod 3 ( Fig. 6G ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.06: 0.32: 0.34: 0.58: 0.37; similar to pereopod 2, except basis with one PSS and propodus with three dorso-subdistal simple setae. Pereopod 4 ( Fig. 6H ) without coxa, with length ratio of articles from basis to dactylus-unguis 1.00: 0.04: 0.32: 0.35: 0.50: 0.39. Setation on ischium, merus, and dactylus-unguis similar to that in female. Basis cylindrical, 3.17 times as long as wide, with two proximodorsal and midventral PSS. Ischium wider than long. Merus 2.28 times as long as wide. Carpus 2.56 times as long as wide, serrate ventrally, with two dorsodistal simple setae and one long and three short distal spiniform setae. Propodus 5.91 times as long as wide, with four longer and two dorsodistal serrated spiniform setae (tip broken), and two ventro-subdistal spiniform setae. Dactylus and unguis fused to claw. Pereopod 5 ( Fig. 6I ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.08: 0.40: 0.49: 0.61: 0.50; similar to pereopod 4, except basis with dorsal PSS but lacking ventral PSS and propodus with six dorsodistal simple setae (one tip broken). Pereopod 6 ( Fig. 6J ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.06: 0.38: 0.48: 0.51: 0.34; similar to pereopod 4, except basis with dorso-subdistal simple seta and propodus with four simple setae and four serrated spiniform setae in dorsodistal region.

Pleopods five pairs, all similar. Pleopod 1 ( Fig. 6K and L ) protopod with inner plumose seta. Exopod with vestigial proximal article bearing ventral plumose seta; remaining portion with 23 outer plumose setae. Endopod with one inner-subdistal and 13 outer plumose setae, and outer distal step-tipped plumose seta. Setal numbers/conditions in pleopods 2–5 summarized in Supplementary Material 3.

Uropod ( Fig. 6M ) with protopod bearing six inner distal simple setae. Endopod with six articles; article 1 with two distal simple setae and distal PSS; article 2 with three distal simple setae and distal PSS; article 3 with simple seta; article 4 with two distal simple setae and two distal PSS; articles 5 and 6 each with distal simple seta. Exopod uniarticulate, shorter than endopodal article 1, with one middle and two distal simple setae.

3.1.1.6. Variation. In addition to holotype and allotype, four female ( ICHUM6345 , ICHUM6346 , ICHUM6348 , ICHUM6349 ) and one male ( ICHUM6347 ) paratypes of C. sublitoralis sp. nov. were dissected, and selected characters were observed for the carapace, antennule, antenna, maxillipeds, cheliped, pereopods 1–6, pleopods 1–5, and uropods (see Supplementary Material 3). The following character states were shared with all specimens (selected characters only are presented): antennular article 1 with mid-inner and mid-outer setae (females) or without middle setae (males); antenna with article 2 bearing one dorsodistal and one ventrodistal spiniform setae, article 3 bearing dorsodistal spiniform seta; maxillipedal palp with article 2 bearing outer seta (female) and article 4 bearing outer seta (female); cheliped slender (female), i.e., carpus with parallel dorsal and ventral margins and at least two times longer than wide; chelipedal merus with one inner seta (female); chelipedal carpus with two (female) or three (male) dorsal setae; fixed finger robust (male), width of region between two apophyses more than 0.75 times width of base of fixed finger; carpus of pereopods 2 and 3 with one dorsal and one ventral simple setae and two ventrodistal spiniform setae; carpus of pereopods 4–6 with three distal spiniform setae (female); protopod of pleopods 1–5 with inner plumose seta; uropodal exopod uniarticulate .

The following characters varied among specimens (selected characters only are presented; states are in parentheses): length/width of female cephalothorax (1.31–1.57); dorsal demarcation of second thoracomere on carapace (present, slight, lacking) ( Fig. 7C and D ); number of antennular articles in females (4–5) ( Fig. 3A and B ); combined length of articles 3 and succeeding article(s) relative to article 2 length in female antennules (1.56–1.82); number of distal simple setae on maxillipedal basis in females (2–4); number of inner simple setae on palp article 4 of maxilliped in females (8–10); length/width of chelipedal carpus in females (2.54–3.27); width of region of fixed finger between two apophyses (0.83 or 0.86 times width of base of fixed finger); number of ventral simple setae on fixed finger of cheliped (3–4); number of distal simple setae on carpus of pereopod 1 (3–5); number of ventrodistal simple setae on merus of pereopods 2 and 3 (0 or 1); number of simple setae on ischium of pereopods 4–6 (1–2); and number of articles of uropodal endopod in females (3–5).

3.1.1.7. Genetic information. A partial COI sequence was determined from the allotype and three paratype specimens ( Table 1). Among four sequences (541 bp, encoding 180 amino acids; LC655988– LC655991 ), there were 0–2 synonymous nucleotide substitutions, i.e., K2P distances among them were 0–0.4%. Interspecific variation between this species and eight congeneric species was 23.1–33.7% K2P distance (Supplementary Material 4) .

3.1.1.8. Distribution. So far known only from the Kumano Sea, northwestern Pacific, 113–185 m depth.

3.1.2. Genus Neoleptochelia Guţu, 2011

Neoleptochelia japonica sp. nov.

[New Japanese name: Kagishippo-tanaisu]

( Figs. 8–12 )

3.1.2.1. Type material. See Table 2.

3.1.2.2. Etymology. The specific name is an adjective referring to Japan, the country wherein lies the type locality .

3.1.2.3. Diagnosis. Female: antenna with article 1 bearing ventrodistal simple seta and article 2 bearing outer simple seta; maxilliped-palp article 4 with outer seta; chelipedal carpus with seven dorsal simple setae; pleopodal protopods with inner plumose seta. Male: chelipedal carpus with seven dorsal simple setae and ventral simple setae; fixed finger with five ventral simple setae.

3.1.2.4. Description of female, based on holotype. Body ( Fig. 9A and B ) slightly dorsoventrally compressed, 6.91 times as long as CW. Cephalothorax ovate, length 0.18 times BL, 1.24 times as long as wide, with pair of lateral simple setae posterior to eye and pair of mid-lateral simple setae; second thoracomere not demarcated dorsally on carapace; eyes well developed, pigmented. Pereonites 1–6 with length ratio 1.00: 1.13: 1.33: 1.64: 1.60: 1.28; all wider than long, rectangular; pereonite 1 with pair of proximodorsal setae and three pairs of lateral setae in anterior region, and pair of lateral setae in posterior region; pereonites 2 and 3 with pair of proximodorsal setae and pair of lateral setae in anterior region, and pair of lateral setae in posterior region; pereonites 4–6 with pair of anterior dorsolateral setae (except pereonite 5) and pair of lateral setae. Pleon length 0.24 times BL. Pleonites as wide as pereonite 6; all wider than long, similar in shape, each with two pairs of lateral setae; pleonites 3–5 with pair of anterodorsal setae. Pleotelson 0.50 times as long as wide, narrower than pleonite 5, pentangular in dorsal view, with pair of anterodorsal setae, pair of anterior dorsolateral setae, and two pairs of posterior setae.

Antennule ( Fig. 10A ) with four articles (article 4 cap-like), stout, 4.98 times as long as wide, 0.79 times as long as cephalothorax; articles 1–4 with length ratio 1.00: 0.25: 0.28: 0.04. Article 1 with two mid-outer, one mid-ventral, one mid-inner, one outer distal, and one inner distal simple setae; two proximal, one mid-outer and two distal PSS; and several inner-proximal setae. Article 2 with one outer distal and one inner distal simple setae, and inner distal PSS. Article 3 with two simple setae, one PSS, and aesthetasc in distal region. Article 4 with four distal simple setae (three broken) and one distal PSS.

Antenna ( Fig. 10B ) with six articles, 0.92 times as long as antennule; articles 1–6 with length ratio 1.00: 1.56: 1.04: 2.34: 0.96: 0.22. Article 1 with ventrodistal seta. Article 2 with dorsodistal and ventrodistal spiniform setae and one outer distal simple seta. Article 3 with dorsodistal spiniform seta (shorter than any on previous article). Article 4 with one mid-outer, one mid-inner, and three distal simple setae and several PSS. Article 5 with two distal simple setae. Article 6 with six distal simple setae.

Labrum ( Fig. 10C ) not projecting anteriorly, setulate. Mandibles ( Fig. 10D and E ) with molar well developed; masticatory region broad. Incisor of left mandible ( Fig. 10D ) with slightly bifurcate tip; lacinia mobilis with four small and one large teeth; incisor process with two small and one large teeth. Incisor of right mandible ( Fig. 10E ) bifurcate distally, with anterior subdistal crenulation. Labium ( Fig. 10F ) bilobed; inner and outer lobes setulate. Maxillule ( Fig. 10G and H ) with setulate endite bearing 11 distal spines; palp ending in two long simple setae. Maxilla lost during dissection. Maxillipeds ( Fig. 10I ) with bases not fused medially, both bearing four long setae and one short seta at insertion of palp. Endites ( Fig. 10K ) not fused medially, reaching distal margin of palp article 1, each with outer distal long setulate seta, three distal flat spiniform setae (two longer and one short, relatively rounded; all with distal serration), three inner distal coupling hooks, and outer distal setulations. Palp ( Fig. 10J ) article 1 naked; article 2 with one outer short and four inner long distal setae; article 3 with one (left) or two (right) outer and eight inner simple setae; article 4 with one outer and nine distal simple setae. Epignath ( Fig. 10L ) elongate, slender, setulate distally.

Cheliped ( Fig. 10M ) chelate, with triangular articulation with cephalothorax via sclerite; sclerite with simple seta. Basis 1.60 times as long as wide, with free posterior portion and outer simple seta. Merus with three ventral and two inner simple setae. Carpus 1.91 times as long as wide, longer than basis, with seven dorsal and three ventrodistal simple setae; outer ventrodistal margin not extending as cuff over proximal region of propodus. Propodal palm with simple seta at insertion of dactylus and inner comb-row of five setae ( Fig. 10N and O ). Fixed finger with three dorsal and two ventral simple setae, and cone shaped claw. Dactylus and unguis fused to claw, as long as fixed finger, with several broad teeth; dactylus with inner proximal simple seta.

Pereopods 1–6 cylindrical, with length ratio 1.00: 0.54: 0.55: 0.68: 0.65: 0.56. Pereopod 1 ( Fig. 11A ) length 0.27 times BL, with length ratio of articles from basis to dactylus-unguis 1.00: 0.09: 0.42: 0.37: 0.66: 0.64. Coxa with simple seta. Basis arched, 3.57 times as long as wide, with dorsoproximal simple seta and PSS. Ischium wider than long, with ventral simple seta. Merus 1.88 times as long as wide, with one dorsal and one ventrodistal simple setae. Carpus 1.67 times as long as wide, with five distal simple setae. Propodus 3.23 times as long as wide, with three dorso-subdistal and one ventro-subdistal simple setae. Dactylus with proximal simple seta. Unguis 1.34 times as long as dactylus, naked. Pereopod 2 ( Fig. 11B ) with length ratio of articles from basis to propodus 1.00: 0.08: 0.39: 0.35: 0.58. Coxa with simple seta. Basis cylindrical, 2.18 times as long as wide, with dorsoproximal simple seta and two PSS. Ischium wider than long, with one ventral simple seta. Merus 1.26 times as long as wide, with one spiniform seta. Carpus 1.13 times as long as wide, with dorsal and ventrodistal simple setae, one very long ventrodistal simple seta (longer than propodus and dactylus combined) and two ventrodistal spiniform setae. Propodus 2.39 times as long as wide, with two simple setae and ventrodistal spiniform seta. Dactylus with one simple seta. Unguis 0.40 times as long as dactylus, naked. Pereopod 3 ( Fig. 11C ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.10: 0.43: 0.33: 0.54: 0.31; similar to pereopod 2, except carpus lacking ventrodistal simple seta and propodus with one dorsodistal simple seta. Pereopod 4 ( Fig. 11D ) without coxa, length ratio of articles from basis to dactylus-unguis 1.00: 0.11: 0.37: 0.27: 0.33: 0.26. Basis thick, 2.38 times as long as wide, with ventral simple seta and three dorsal PSS. Ischium wider than long, with two ventral simple setae. Merus 1.98 times as long as wide. Carpus 1.13 times as long as wide, with one simple seta and three serrated spiniform setae. Propodus 2.59 times as long as wide, with two dorsodistal serrate setae, dorsodistal serrated spiniform seta, and two short ventro-subdistal spiniform setae. Dactylus and unguis fused to claw; claw carved, serrated. Pereopod 5 ( Fig. 11E ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.10: 0.39: 0.32: 0.31: 0.21; similar to pereopod 4, except basis with ventral PSS but lacking three dorsal PSS. Pereopod 6 ( Fig. 11F ) with length ratio of articles from basis to propodus 1.00: 0.11: 0.47: 0.38: 0.39; similar to pereopod 4, except basis with one dorsal PSS and propodus with six dorsodistal serrated setae.

Pleopods five pairs, all similar. Pleopod 1 ( Fig. 11G and H ) protopod with inner plumose seta. Exopod with vestigial proximal article bearing ventral plumose seta; remaining portion with 20 outer plumose setae. Endopod with one inner-subdistal and 10 outer plumose setae, and outer distal step-tipped plumose seta. Setal numbers/conditions in pleopods 2–5 summarized in Supplementary Material 5.

Uropod ( Fig. 11I ) with protopod bearing simple seta. Endopod with three articles; article 1 with two simple setae; article 2 with four distal simple setae; article 3 with three middle and two distal simple setae and two PSS. Exopod uniarticulate, longer than endopodal article 1, with one middle and two distal simple setae.

3.1.2.5. Description of male, based on allotype. Body ( Figs. 8A, B and 9E, F ) slightly dorsoventrally compressed, 5.18 times as long as CW, slightly reddish in the living animal ( Fig. 8A and B ). Cephalothorax pearsharped in dorsal view, length 0.22 times BL, 1.13 times as long as wide, with pair of lateral simple setae posterior to eye and pair of mid-lateral simple setae; second thoracomere not demarcated dorsally on carapace; eyes well developed, pigmented. Pereonites 1–6 with length ratio 1.00: 1.27: 1.33: 1.98: 1.23: 1.52; all wider than long; pereonite 1 with three pairs of lateral setae in anterior region and pair of lateral setae in posterior region; pereonites 2 and 3 with pair of anterodorsal setae and pair of lateral setae in anterior region, and pair of anterior dorsolateral setae; pereonites 4–6 with pair of anterodorsal setae and three pair of lateral setae ( Fig. 12I and J ); pereonite 4 with pair of anterior dorsolateral setae. Pleon length 0.27 times BL. Pleonites slightly wider than pereonite 6; all wider than long, similar in shape, each with two pairs of lateral setae; pleonites 2–5 with pair of anterodorsal setae. Pleotelson ( Fig. 9F ) length 0.38 times width, narrower than pleonite 5, pentangular in dorsal view, with pair of anterodorsal setae and pair of anterior dorsolateral setae, and two pairs of posterior setae.

Antennule ( Fig. 12A ) with 12 articles, 2.66 times as long as cephalothorax; articles 1–12 with length ratio 1.00: 0.52: 0.12: 0.03: 0.08: 0.10: 0.10: 0.08: 0.05: 0.07: 0.09: 0.01. Article 1 with one mid-outer, one outer distal, and one inner distal setae; three ventro-subproximal and four outer distal PSS; and several inner-proximal setae. Article 2 with two distal simple setae and four distal PSS. Article 3 with two distal simple setae and one PSS. Articles 4–10 each with ventral row of aesthetascs. Article 11 with two simple setae and aesthetasc. Article 12 with four simple setae and one PSS.

Antenna ( Fig. 12B ) with seven articles, 0.43 times as long as antennule; articles 1–7 with length ratio 1.00: 1.38: 1.30: 2.03: 2.08: 1.73: 0.16. Article 1 with ventrodistal seta. Article 2 with dorsodistal and ventrodistal spiniform setae and one outer distal simple seta. Article 3 with spiniform seta (broken). Article 4 with one outer and one inner distal simple setae, and one inner PSS. Article 5 with three distal simple setae and several PSS. Article 6 with two distal simple setae. Article 7 with five distal simple setae.

Maxillipedal endite lacking, palp lacking ( Fig. 12C ).

Cheliped ( Fig. 12D and E ) chelate, with triangular articulation with cephalothorax via sclerite; sclerite with simple seta. Basis 1.54 times as long as wide, with one outer seta. Merus with three ventral and two inner simple setae. Carpus slender, 8.87 times as long as wide, longer than basis, with seven dorsal (four broken) and three ventrodistal simple setae; outer ventrodistal margin not extending as cuff over proximal region of propodus. Propodus also slender, nearly as long as carpus. Propodal palm with outer simple seta at insertion of dactylus and inner comb-row of 13 setae; comb-row nearly parallel to dorsal margin of propodal palm. Fixed finger curved distally, with three dorsal and five ventral simple setae. Dactylus and unguis fused to claw, curved distally, slightly longer than fixed finger; dactylus with ventral apophysis, inner proximal simple seta, and 13 ventral spiniform setae.

Pereopods 1–6 cylindrical, with length ratio 1.00: 0.82: 0.69: 0.78: 0.74: 0.69. Pereopod 1 ( Fig. 12F ) 0.47 times as long as BL, with length ratio of articles from basis to dactylus-unguis 1.00: 0.09: 0.51: 0.40: 0.66: 0.48. Setation of coxa, ischium, merus, carpus, and unguis similar to those of female. Coxa with simple seta. Basis slightly arched, 5.33 times as long as wide, with dorsoproximal simple seta. Ischium wider than long. Merus 3.38 times as long as wide. Carpus 2.56 times as long as wide. Propodus 5.00 times as long as wide, with three dorso-subdistal simple setae, ventro-subdistal spiniform seta, and ventro-subdistal setulate puff. Dactylus strongly bent ventrally at subproximal point (cf. Fig. 8E ), serrated. Unguis 0.48 times as long as dactylus. Pereopod 2 ( Fig. 12G ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.06: 0.33: 0.37: 0.61: 0.36. Setation of coxa, merus, and unguis similar to those of female. Basis cylindrical, 4.74 times as long as wide, with dorsoproximal simple seta and PSS. Ischium wider than long, with two ventral simple setae. Merus 2.13 times as long as wide. Carpus 2.45 times as long as wide, with three distal simple setae and two ventrodistal spiniform setae. Propodus 4.14 times as long as wide, with two dorso-subdistal simple setae, ventrodistal spiniform seta, and ventro-subdistal setulate puff ( Fig. 8C and D ). Dactylus strongly bent ventrally at subproximal point, with one simple seta; serrated. Unguis 0.77 times as long as dactylus. Pereopod 3 ( Fig. 12H ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.05: 0.32: 0.37: 0.51: 0.38; similar to pereopod 2, except propodus with one dorsal simple seta. Pereopod 4 ( Fig. 12I ) without coxa, length ratio of articles from basis to dactylus-unguis 1.00: 0.07: 0.27: 0.43: 0.65: 0.36. Setation on basis and ischium similar to that in female. Basis proportionally narrower than in female, 3.21 times as long as wide. Ischium wider than long. Merus 2.00 times as long as wide, with two ventral spiniform setae and serration. Carpus 2.97 times as long as wide, with one simple seta and four spiniform setae. Propodus 6.89 times as long as wide, with three dorsodistal simple setae and two ventro-subdistal spiniform setae. Dactylus and unguis fused to claw; claw nearly straight, serrated. Pereopod 5 ( Fig. 12J ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.12: 0.30: 0.50: 0.73: 0.38; similar to pereopod 4. Pereopod 6 ( Fig. 12K ) with length ratio of articles from basis to dactylus-unguis 1.00: 0.06: 0.34: 0.42: 0.61: 0.34; similar to pereopod 4, except basis lacking PSS and propodus having five dorsodistal serrated spiniform setae.

Pleopods five pairs, all similar. Pleopod 2 ( Fig. 12L and M ) protopod with inner plumose seta. Exopod with vestigial proximal article bearing ventral plumose seta; remaining portion with 21 outer plumose setae. Endopod with one inner-subdistal, 13 outer plumose setae, and outer distal step-tipped plumose seta. Setal numbers/conditions in pleopods 1, 3–5 summarized in Supplementary Material 5.

Uropod ( Fig. 12N ) with protopod bearing six simple setae. Endopod with five articles; article 1 with five simple setae and PSS; article 2 with five distal simple setae and PSS; article 3 with four simple setae; article 4 with one simple seta; article 5 with four simple setae. Exopod uniarticulate, longer than endopodal article 1, with one middle and two distal simple setae.

3.1.2.6. Variation. In addition to holotype and allotype, two female ( ICHUM8470 , ICHUM8471 ) paratypes of N. japonica sp. nov. were dissected, and selected characters were observed for the carapace, antennule, antenna, maxillipeds, cheliped, pereopods 1–6, pleopods 1–5, and uropods (see Supplementary Material 5). The following character states were shared with all specimens (selected characters only are presented; sexes are in parentheses): antennule with four articles (female); antennular article 1 with two mid-outer simple setae (female); antenna with article 1 bearing one ventral simple seta and article 2 bearing one outer simple seta; maxillipedal palp with article 2 bearing one outer simple seta (female) and article 4 bearing one outer simple seta (female); cheliped with merus bearing three ventral simple setae and carpus bearing seven dorsal setae; fixed finger with two (female) or five (male) ventral simple setae; pereopod 1 with merus bearing one dorsal and one ventral distal setae and propodus bearing three dorsodistal setae; carpus of pereopods 4–6 with three (female) or four (male) spiniform setae; protopod of pleopods 1–5 with inner plumose seta; uropodal exopod uniarticulate .

The following characters varied among females (selected characters only are presented; states are in parentheses): dorsal demarcation of second thoracomere on carapace (present, absent); number and length of distal simple setae on maxillipedal basis (1 short and 4 long; 1 medium and 3 long; 1 short, 1 medium, and 5 long); number of inner simple setae on chelipedal merus (1, 2); number of simple setae on pereopod 2 ischium (1, 2); number of ventrodistal simple setae on pereopod-3 carpus (1, 2); number of simple setae on pereopod-4 ischium (0, 2); number of articles on uropodal endopod (3, 4).

3.1.2.7. Genetic information. A partial COI sequence was determined from the holotype, allotype, and two paratype specimens ( Table 2). Among the four sequences (658 bp, encoding 219 amino acids; LC745706– LC745709 ), there were 0–3 synonymous nucleotide substitutions; K2P distances among them were 0–0.5%. Our sequences were the first from any Neoleptochelia species deposited in public databases .

3.1.2.8. Distribution. Presently known only from the intertidal zone at the type locality, Bise , Okinawa Island, Okinawa, Japan .

Figures

Fig. 1. Chondrochelia sublitoralis sp. nov., living paratype female (ICHUM6351) (A, B) and allotype male (C, D) in dorsal (A, C) and lateral (B, D) views. Scale bar: 1 mm.

Fig. 2. Chondrochelia sublitoralis sp. nov., holotype female (A–C) and allotype male (D–F); A, D body, dorsal view; B, E body, lateral view; C, F posterior region of body, dorsal view. Scale bars: 1 mm.

Fig. 7. Antennules (A, B) and carapaces (C, D) of Chondrochelia sublitoralis sp. nov., females; A five-articulate state; B four-articulate state; C, D carapaces with (C) and without (D) dorsal demarcation. Scale bars: 0.5 mm.

Fig. 3. Right antennules of Chondrochelia sublitoralis sp. nov.; A holotype female, five-articulate state; B paratype female (ICHUM6345), four-articulate state; C allotype male. Scale bars: 0.1 mm.

Fig. 4. Chondrochelia sublitoralis sp. nov., holotype female; A right antenna; B labrum; C, D left and right mandibles; E labium; F, G left and right maxillules; H maxillipeds (setae on palp articles 3 and 4 omitted); I same, left palp articles 3 and 4 (inner setae on palp article 2 omitted); J same, endites; K right epignath; L right cheliped, outer view; M, N same, distal portion of chela, outer (M) and inner (N) views. Scale bars: 0.1 mm.

Fig. 5. Chondrochelia sublitoralis sp. nov., holotype female; A–F right pereopods 1–6; G right pleopod 1 (most setal ornamentation and most outer plumose setae on endopod omitted); H same, endopod (most setal ornamentation omitted); I right uropod. Scale bars: 0.1 mm.

Fig. 6. Chondrochelia sublitoralis sp. nov., allotype male; A right antenna; B mouthparts; C right cheliped, outer view; D same (basis not illustrated), inner view; E–J right pereopods 1–6; K right pleopod 1 (most setal ornamentation and outer plumose setae on endopod omitted); L same, endopod (most setal ornamentation omitted); M right uropod. Scale bars: 0.1 mm.

Fig. 8. Neoleptochelia japonica sp. nov., allotype male; A, B living individual in dorsal (A) and lateral (B) views; C, D distal portion of right pereopod 2; E distal portion of right pereopod 3; arrowheads, setulate puff; arrow, point where dactylus is strongly bent ventrally. Scale bars: 1 mm (A, B), 0.1 mm (C, E), and 0.05 mm (D).

Fig. 9. Neoleptochelia japonica sp. nov.; holotype female (A–C) and allotype male (D–F); A, D body, dorsal view; B, E body, lateral view; C, F posterior region of body, dorsal view. p3, 4, pereonites 3 and 4. Scale bars: 1 mm (A, B, D, E) and 0.5 mm (C, F).

Fig. 10. Neoleptochelia japonica sp. nov., holotype female; A right antennule; B right antenna; C labrum, D, E left and right mandibles; F labium; G, H left and right maxillules; I maxillipeds, dorsal view (setae on palp and basis omitted); J same, palps and distal portion of bases, ventral view; K same, endites, dorsal view; L epignath; M right cheliped, outer view; N, O same, distal portion of chela, outer (N) and inner (O) views. Scale bars: 0.1 mm.

Fig. 11. Neoleptochelia japonica sp. nov., holotype female; A left pereopod 1; B–F right pereopods 2–6; G right pleopod 1 (most setal ornamentation and most outer plumose setae on endopod omitted); H same, endopod (most setal ornamentation omitted); I right uropod. Scale bars: 0.1 mm.

Fig. 12. Neoleptochelia japonica sp. nov., allotype male; A right antennule (most aesthetascs omitted); B right antenna; C maxillipeds; D right cheliped, outer view; E same, chela, inner view; F–H, J, K right pereopods 1–3, 5, 6; I left pereopod 4; L, right pleopod 2 (most setal ornamentation and most outer plumose setae on endopod omitted); M same, endopod (most setal ornamentation omitted); N right uropod. Scale bars: 0.5 mm (A, D, E) and 0.1 mm (all others).