Nitocra typica typica Boeck, 1865.

Nitocra affinis Gurney, 1927; N. alperi Yıldız & Karaytuğ, 2024; N. arctolongus Shen & Tai, 1973; N. australis Soyer, 1975; N. balli Rouch, 1972; N. balnearia Por, 1964; N. bdellurae (Liddell, 1912); N. bisetosa Mielke, 1993; N. blochi Soyer, 1975; N. californica Lang, 1965b; N. cari Petkovski, 1954; N. chelifer Wilson, C. B., 1932; N. colombiensis Fuentes-Reinés & Suárez-Morales, 2014; N. delaruei Soyer, 1975; N. divaricata caspica Behning, 1936; N. divaricata divaricata Chappuis, 1924; N. dubia Sars, G. O., 1927; N. elegans (Scott, T., 1905); N. elongata Marcus, 1968; N. esbe Karanovic, Eberhard, Cooper & Guzik, 2015; N. evergladensis Bruno & Reid, 2002; N. fallaciosa baltica Lang, 1965a; N. fallaciosa fallaciosa Klie, 1937; N. fluviatilis Galhano, 1968; N. fragilis fragilis Sars, G. O., 1905, N. fragilis paulistana Jakobi, 1956; N. galapagoensis Mielke, 1997; N. hamata Bodin, 1970; N. hibernica bulgarica (Apostolov, 1976); N. hibernica hibernica (Brady, 1880); N. hibernica hyalina Jakubisiak, 1929; N. humphreysi Karanovic & Pesce, 2002; N. husmanni Kunz, 1976; N. hyperidis Jakobi, 1956; N. karanovici Chullasorn, Kangtia & Klangsin, 2014; N. kastjanensis Kornev & Chertoprud, 2008; N. koreanus Chang, 2007; N. lacustris azorica Kunz, 1983; N. lacustris colombianus Reid, 1988; N. lacustris lacustris (Schmankevitsch 1875); N. lacustris pacifica Yeatman, 1983; N. lacustris sinoi Marcus & Por, 1961; N. laingensis Fiers, 1986; N. langi Karanovic, Eberhard, Cooper & Guzik, 2015; N. loweae Yıldız & Karaytuğ, 2024; N. malaica Kiefer, 1929; N. marinae Jaschnov, 1935; N. mediterranea jakubisiak Karanovic, Eberhard, Cooper & Guzik, 2015; N. mediterranea mediterranea Brian, 1928; N. medusaea Humes, 1953; N. minor Willey, 1930; N. mozambica Huys, 2021; N. oligochaeta Giesbrecht, 1882; N. phlegraea Brehm, 1909; N. phreatica Bozic, 1964; N. pietschmanni Chappuis, 1933; N. platypus platypus Daday, 1906; N. platypus bakeri Chappuis, 1930; N. pontica Boeck, 1865; N. pori Karanovic, Eberhard, Cooper & Guzik, 2015; N. psammophila Noodt, 1952; N. pseudospinipes Yeatman, 1983; N. puebloviejensis Fuentes-Reinés, Suárez-Morales & Silva-Briano, 2022; N. pusilla mediterranea Brian, 1928; N. pusilla pusilla Sars, G. O., 1911; N. quadriseta Wells & Rao, 1987; N. quangnamensis Tran, Trinh-Dang, Nguyen & Brancelj, 2025; N. reducta Schäfer, 1936; N. reunionensis Bozic, 1969; N. rijekana Petkovski, 1954; N. salina (Schmankevitsch, 1875); N. serdarsaki Yıldız & Karaytuğ, 2024; N. sewelli Gurney, 1927; N. simplex Schmeil, 1894; N. sonmezi Yıldız & Karaytuğ, 2024; N. sphaeromata Bowman, 1988; N. spinipes orientalis Sewell, 1924; N. spinipes spinipes Boeck, 1865; N. stygia Por, 1968; N. taylori Gómez, Carrasco & Morales-Serna, 2012; N. tenuicornis Brady & Robertson, 1873; N. typica adriatica Petkovski, 1954; N. typica pontica Jakubisiak, 1938; N. uenoi Miura, 1962; N. vietnamensis Tran & Chang, 2012; N. wolterecki Brehm, 1909; N. yahiai (Blanchard & Richard, 1891); N. yeelirrie Karanovic, Eberhard, Cooper & Guzik, 2015.

• Adult female holotype dissected and mounted on one slide (ZC-DTU-COPEPODA-0014) • adult male allotype dissected and mounted on one slide (ZC-DTUCOPEPODA-0015) • two female and two male paratypes preserved in 70% ethanol (ZC-DTU-COPEPODA-0013).

Hyporheic zone in Vu Gia – Thu Bon river (15°50'15"N, 108°09'05"E), Quang Nam province, Central Vietnam.

Caudal rami 1.2× as long as wide. Anal operculum with six marginal spinules. Female antennule eight-segmented; male antennule haplocer, eight-segmented. Antenna with allobasis. P1Exp-2 with inner seta; Exp-3 with five elements in all; P1Enp-1 reaching approximately the middle of Exp-2, with inner seta; Enp-2 with three elements. P2–P4Exp-2 with inner seta, Exp-3 with seven setae/spines; P2–P4Enp-1 without, Enp-2 with inner seta, Enp-3 with four, five, and five setae/spines respectively. Female P5Exp with six, Benp with five setae and reaching the middle of Exp; male P5Exp with six, baseoendopods fused medially, each with three setae.

Habitus (Fig. 1A) semicylindrical; total body length measured from tip of rostrum to posterior margin of caudal rami ranging from 492 to 546 μm (average = 519 μm, n = 5; holotype = 546 μm). Nauplius eye not visible. Rostrum (Fig. 1A) linguiform, small, not reaching end of first antennule segment, with pair of tiny sensilla subapically. Prosome four-segmented, comprising cephalothorax with completely fused first pedigerous somite, and three free pedigerous somites; cephalothorax and P2–P4-without surface ornamentation other than sensilla as shown (Fig. 1A). Urosome five-segmented, comprising fifth pedigerous somite, genital double-somite, two free urosomites, and anal somite with caudal rami (Fig. 1A, B); P5-bearing somite without spinular ornamentation, with few posterior sensilla; genital double-somite (Fig. 1A–C) formed by the fusion of genital and third urosomite, with dorsolateral suture indicating original division, completely fused ventrally, proximal half with dorsolateral sensilla close to suture and with short row of lateral spinules as depicted (Fig. 1B), ventrally with medially interrupted row of minute spinules and with sensilla along partial ventral suture, genital field close to anterior margin of first half of somite (Figs 1C, 6B), with large median copulatory pore; fourth urosomite with posterior spinular row ventrally (Fig. 1C); fifth urosomite with medial ventrolateral row of small spinules and with continuous row of small ornaments close to posterior margin, without sensilla (Fig. 2A, B); anal somite (Figs 1A, 2A, B) with median ventrolateral row of spinules, with strong spinules close to caudal rami dorsally (Figs 1A, 2A), and with comparatively smaller ornaments ventrally (Fig. 2B), anal operculum semicircular with six strong marginal spinules and flanked by pair of sensilla (Figs 1A, B, 2A). Caudal rami (Figs 1B, C, 2A, B) short, subquadrate, 1.2× as long as wide, with seven elements each; anterolateral seta I slender, short, ~0.3× as long as caudal ramus; anterolateral seta II and posterolateral seta III smooth, the former slightly shorter than the latter, with short strong spinules at base of seta II; outer apical seta IV and middle apical seta V well-developed, with fracture planes, seta V longest; distal inner accessory seta VI slender, smooth, 0.9 as long as caudal ramus, with several small spinules at its base; dorsal seta VII tri-articulated, ~2.4× as long as caudal ramus, issuing close to posterior margin of ramus.

Antennule (Fig. 3A) 8-segmented, long and slender; all segments smooth except for first segment with a row of spinules; all setae smooth except for pinnate seta on first segment. Aesthetasc on fourth segment, fused to long seta, reaching well beyond distal end of last segment. Armature formula as follows: 1(1), 2(7), 3(2), 4(2+(1+ae)), 5(2), 6(1), 7(4), 8(5+acrothek).

Antenna (Fig. 3B) relatively short, composed of coxa, allobasis, one-segmented endopod, and one-segmented exopod. Coxa short, unornamented. Allobasis 2.7× as long as wide, with a short row of inner spinules proximally, and several minute proximal spinules close to coxa. Exopod with three distal unequal setae (one bare, two unipinnate). Endopod with inner longitudinal spinular row; lateral armature consisting of one inner spine and one strong inner seta; distally with one smooth seta, four geniculate setae and one distal outer geniculate seta fused basally to slender element.

Mandible (Fig. 3C) with well-developed coxa; gnathobase with ~11 teeth as shown, and single lateral seta. Mandibular palp 2-segmented, first segment (basis) with one strong plumose seta; endopod with one lateral and four smooth apical setae.

Maxillule (Fig. 3D) with well-developed praecoxa; arthrite with two surface setae, and four large robust distal spines. Coxal endite with two smooth setae. Basis with five normal unequal setae distally. Endopod 1-segmented, with four slender smooth setae.

Maxilla (Fig. 3E) without spinular ornamentation on syncoxa, the latter with two endites; proximal endite somewhat bulbous, with one strong plumose seta; distal endite cylindrical, with three subequal setae. Allobasis drawn out into long claw accompanied by a shorter bare seta. Endopod short, one-segmented; with two subequal, smooth setae.

Maxilliped (Fig. 3F) with short and stout syncoxa, the latter 1.3× as long as wide, with short row of posterior spinules, with one small bare seta subapically. Basis ~2.2× as long as wide, with short row of inner spinules and with one outer subdistal spinule. Endopod drawn out into long curved smooth claw accompanied by single short slender seta.

P1–P4 (Figs 4A, B, 5A, B) with short unornamented intercoxal sclerites, the latter with dorsal tines as shown. Coxa of P1 and P2 with, of P3 and P4 without outer subdistal spinules. Basis of P1 with spinules at the base of inner and outer spine, with additional ornaments between rami; basis of P2–P4 with spinules at the base of outer spiniform (P2) and setiform elements (P3–P4), of P2 and P3 with, of P4 seemingly without spinules close to the base of the endopod. Rami three-segmented. Exopodal segments with outer and subdistal spinules as shown; Exp-1 with outer spine, without inner armature; Exp-2 with outer spine and inner seta; Exp-3 with three outer spines, two distal geniculate setae and without inner armature (P1) or with one distal outer spiniform and one distal inner setiform element and with two inner setae (P2–P4). Endopodal segments with outer ornaments as figured; P1Enp visibly longer than Exp, Enp-1 not reaching beyond Exp-2; Enp-1–2 with inner seta, Enp-3 with three elements; P2–P4Enp shorter than Exp; P2–P3Enp reaching distal tip of Exp-2, P4Enp reaching slightly above the middle of Exp-2; Enp-1 short, wider than long, unarmed; Enp-2 with one inner seta and a projection at the inner distal corner; Enp-3 with one (P2) or two (P3 and P4) inner setae, two distal elements, and one outer spine; length ratio of armature elements on P3Enp-3 (starting from outer most apical spine) 1: 1.9:4.7:5.2:2.9. Armature formula of P1–P4 as in Table 1.

P5 (Fig. 6A) with exopod and baseoendopod separated. Baseoendopod with outer unipinnate seta; endopodal lobe well-developed, with longitudinal row of outer spinules, with three inner spinulose spines, and two robust distal setae of which distal inner longest. Exopod oval, 1.6× as long as wide, with six unequal smooth setae of which two outer and outer subdistal seta shortest.

P6 (Fig. 6B) represented by narrow plate with one single plumose seta on each side.

Body shape and general appearance as in female (Fig. 7A); total body length measured from tip of rostrum to posterior margin of caudal rami ranging from 476 to 508 μm (average = 492 μm, n = 2; holotype = 508 μm). Rostrum, prosomites, anal operculum, and caudal rami as in female (Fig. 7A, C, D). Sexual dimorphism expressed in urosomal segmentation (genital and third urosomite not fused), spinular ornamentation of urosomites, antennule, basis of P1, P5, and P6.

Genital somite (Fig. 7A, B) with continuous posterior dorsolateral spinular row; third urosomite with dorsolateral spinular row interrupted ventrolaterally; fourth and fifth urosomites (Fig. 1A–D) with continuous posterior and median spinular row, respectively, and fifth urosomite with short spinular row ventrally.

Antennule (Fig. 8A) haplocer, 8-segmented, with geniculation between sixth and seventh segments; all segments smooth except for first segment with some spinules. All setae smooth except for plumose seta on first segment. Fourth segment with large aesthetasc fused to long seta overreaching last segment, and with one robust short unipinnate spine. Armature formula as follows: 1(1), 2(8), 3(5), 4(6+(1+ae)), 5(0), 6(1), 7(1), 8(7+acrothek).

Antenna, mandible, maxillule, maxilla, and maxilliped (not shown) as in female.

P1 (Fig. 9A) as in female except for inner spine of basis modified into element with rounded tip; inner margin of Exp-2 and outer margin of Enp-2 naked.

P2 and P4 (not shown) as in female.

P3 (Fig. 9B) as in female except for absence of spinular row on distal margin of basis, and for length ratio of all setae on Enp-3 (1:1.3:1.5:3.6:1.2).

P5 baseoendopods (Fig. 8B) fused medially. Baseoendopod with one outer long smooth seta, endopodal lobe weak, with three naked spiniform setae of which outermost shortest, innermost longest. Exopod with six smooth unequal setae; relative length of exopodal setae (from outermost to innermost seta) 1:0.5:1.2:1.3:0.7:1.8.

P6 (Fig. 8C) small, with two bare unequal setae, of which inner longer.

No variability was observed.