Karstodiaptomus sheni, Shu, Shusen, Brancelj, Anton, Chen, Feizhou, Yang, Junxing & Chen, Xiaoyong, 2017

Shu, Shusen, Brancelj, Anton, Chen, Feizhou, Yang, Junxing & Chen, Xiaoyong, 2017, A new freshwater stygobiotic calanoid (Copepoda: Speodiaptominae) from Yunnan, China, Zootaxa 4290 (1), pp. 192-200 : 194-197

Karstodiaptomus sheni n. gen., n. sp.

( Figs. 2–4 )

Type locality. A pool in Dadong Cave (coordinates of the entrance: 24° 50' 54.95'' N; 104° 23'39.90'' E; altitude 1451 m), Agou Village , Luoping County, Qujing City, Yunnan Province, China.

Material examined. Holotype (male) total length 820 µm (KIZ-CR-2012001); collected from type locality on 12 Sept. 2012 by Shusen Shu and Guihua Cui; dissected and mounted on a slide in glycerol. Allotype (female) total length 970 µm (KIZ-CR-2012002); collected on same date and locality as holotype; dissected and mounted on a slide in glycerol. Paratypes: 2 males (KIZ-CR-2012003, 2012004); male 2012003 dissected and mounted on a slide in glycerol; 12 females (KIZ-CR-2012005-16); female 2012005 dissected and mounted on a slide in glycerol; all paratypes collected on the same date and locality as the holotype and allotype; 12 paratypes preserved in 95% ethanol.

Description of female. Body length, from forehead margin to posterior margin of caudal rami, 760–1010 µm; mean body length 900 µm; mean prosome length 640 µm; mean urosome length 270 µm (n= 12). Body slender, with maximum width near middle of Pd1 ( Fig. 2 A). Rostrum represented by pair of soft, finger-like filaments, pointed backward ( Fig. 2 B). Pd4–Pd5 fused, except lateral margins. Pd5 with moderately developed asymmetrical lobes; left lobe distinctly slender than right one, triangular, with 1lateral sensillum; right lobe without sensillum.

Urosome of 3 free somites. Genital double-somite slightly longer than following 2 urosomites combined; asymmetrical, anterior part only slightly curved, with distinct invagination at posterior part ( Fig. 2 C). Right side slightly dilated, with a minute spine at 1/2 length of its margin. Urosomite 2 short, asymmetrical; left margin longer than right. Urosomite 3 (anal somite) sub-quadrate, longer than urosomite 2.

Caudal rami symmetrical; each ramus about 2 times as long as wide, with medial and lateral margins smooth. Anterior lateral seta (I) not discernible; setae II–VI plumose on distal half; length of all setae subequal except outer one (II; about 80% of length of others). Dorsal seta (VII) inserted on medial distal corner of caudal ramus, as long as longest terminal seta, smooth.

Antennule with 25 discernible segments ( Fig. 2 D), reaching distal margin of anal somite ( Fig 2 A). Seta on segment 1 short, not reaching distal margin of segment 2. Longest setae on segments 7, 9, 11, 14, 18, 21–25. Armature per segment as follows (Arabic numbers—discernible segments; numbers in brackets: s—number of setae, Sp—spine, A—aesthetasc):

I(1s), II (3s + A), III(1s), IV(1s), V(1s + A), VI(1s), VII(1s), VIII(1s + Sp), IX(2s + A), X(1s), XI(1s), XII(1s + Sp + A), XIII(1s), XIV(1s + A), XV(1s), XVI(1s + A), XVII(1s), XVIII(1s), XIX(1s + A), XX(1s), XXI(1s), XXII(1s + Sp), XXIII(2s), XXIV(2s), XXV(4s).

Antenna ( Fig. 2 E) with Exp as long as Enp; coxa with 1 seta; basis with 2 smooth setae. Enp 2-segmented; Enp-1 with 2 short setae at 1/2 length of segment; Enp-2 with 2 lobes distally, proximal (inner) lobe with 7 setae increasing in length from anterior to posterior; 7 long setae apically, 1 long seta subapically. Exp 7-segmented; Exp-1 with 1, Exp-2 with 3 and Exp-3 to Exp-6 each with 1 seta laterally. Exp-7 with 1 laterally and 3 setae apically.

Mandible ( Fig. 2 F) basis with 4 setae, proximal 2 setae longest, uni-pinnate. Exp 4-segmented, with 1, 1, 1, 3 setae. Enp 2-segmented; Enp-1 with 4 setae, equal in length; Enp-2 with 7 setae apically, similar in length; gnathal lobe with 6 small teeth and strong outermost tooth.

Maxillule ( Fig. 2 G) well developed; praecoxal arthrite with 9 setae (proximal 2 longer and plumose), with 4 setae submarginally; epipod of coxa with 5 setae: 2 smooth, short and 3 plumose, long; coxal endite with 1 seta; basal endite small, with 6 setae; Exp fused, with 6 setae distally; Enp fused, with 4 setae laterally and 9 distal setae apically.

Maxilla ( Fig. 2 H) small, praecoxal endites separated, with 3 and 2 long setae, respectively; coxal endites with 2 and 2 long setae; basis with 1 short and 2 long setae; Enp 2-segmented: Enp-1 with 2 setae; Enp-2 with 4 setae, apical one very short.

Maxilliped ( Fig. 2 I) well developed; syncoxa with 4 lobes, with 1, 2, 3, 4 setae, unequal in length. Basis with 3 setae along distal margin and a row of slender spinules (about 9, n = 2) anteriorly. Enp 6-segmented; segments 1 and 2 completely separated, setal formula: 2, 3, 2, 2, 2, 5.

P1–P3 with 2-segmented Exp and Enp; P4 with 3-segmented Exp and 2-segmented Enp ( Fig. 3 A–D). P2 Enp without Schmeil’s organ. Coxa and basis without setae. Armature formula of P1–P4 as follows (Roman numerals—spine; Arabic numerals—setae; lateral-medial, lateral-apical-medial):

Exopodite Endopodite

Segments 1 2 3 1 2 P 1 I-1 I- 3-2 - 0-1 0-2-2 P 2 I-1 I- 2-4 - 0-1 0-3-2 P 3 I-1 I- 3-3 - 0-1 0-2-3 P 4 I-1 I- 1 I-3-2 0-1 0-2-3 P5 ( Fig. 3 E) slightly asymmetrical. Coxa as long as wide, with well-developed hyaline membrane along 3/4 of lateral distal margin; small spine in medial distal corner. Basis narrower than coxa, without seta. Exp-1 about 2 times as long as wide, with smooth margins. Basal region of Exp-2 as long as wide, prolonged into robust claw-like apophysis on medial corner, as long as Exp-1; short seta at 1/2 length of lateral margin of Exp-2. Exp-3 reduced; represented with 1 spine and short seta at the distal lateral corner of Exp-2. Enp 1-segmented; right one slightly shorter than Exp-1, with no armature; left one as long as Exp-1, with long seta subterminally.

Egg sac ( Fig. 2 A) with 6 relatively large eggs.

Description of male. Body length from forehead margin to posterior margin of caudal rami, 810–890 µm; mean body length: 840 µm; mean prosome length: 584 µm; mean urosome length: 281µm (n= 3). Body slender, with widest part at anterior portion of cephalothorax ( Fig. 4 A). Rostrum as in female. Pd2–Pd4 incompletely separated; Pd4–Pd5 completely fused; Pd5 with moderately developed, asymmetrical wings; left with 2 sensilla; right with 1 sensillum.

Urosome with 5 somites. Genital somite wider than long, slightly asymmetrical, left margin a little concave; with 1 spine on right margin distally. Caudal rami about 2.8 times as long as wide, medial and lateral margins smooth. Anterior lateral seta (I) not discernible/reduced. Setae II–VI sub-equal in length; plumose at distal half. Dorsal seta (VII) articulated, smooth, half of length of seta VI.

Left antennule with 25 discernible segments, extending up to end of caudal rami. Right antennule with 23 discernible segment, geniculation between segments 18 and 19; with long setae on segments 7, 8,14, 16; aesthetascs on segments 5, 8, 14; small spines on segments 7, 9,10, 12, 13, 15; spine on segment 13 longest ( Fig. 4 B). Segments 17–19 with 1, 1, 2 long spines. No spine or hyaline membrane on antepenultimate segment. Segments 13–16 slightly dilated.

Antenna, mouthparts, P1–P4 as in female.

Left P5 ( Fig. 4 C) short, reaching middle of Exp-2 of right leg. Coxa as long as wide, without coxal lobe or spine. Basis trapezoidal, smooth, without hyaline lamella or sensory seta. Exp-1 incurved, with field of short bristles on distal half of medial margin. Exp-2 small, almost triangular; medial margin with bristles; proximal half with longer and sparser bristles, distal half with shorter and denser ones. Terminal spine small, finger-like; outcurved piniform seta sun-terminally. Enp-1 1-segmented, reaching middle of Exp-2, finger-like, without armature.

Coxa of right P5 ( Figs. 4 C–D) as long as wide, with 1 spine on posterior corner. Basis wide, with a chitinous, triangular process at proximal medial corner; a hyaline lobe with a sturdy spine distally from triangular process. Exp-1 as long as wide, with large hyaline lobe on medial part of segment dorsally. Exp-2 elliptical, about 1.7 times as long as wide, medial margin only slightly convex; lateral margin slightly convex; small hyaline lobe with a short spine near anterior medial corner dorsally. Lateral spine long, straight, inserted at 3/4 of margin length, about 0.9 times as long as segment bearing it. End claw long, slightly curved, slender, smooth, about 2.6 times as long as outer lateral spine, tip curved outward. Endopodite 1-segmented, finger-like, long, reaching middle of Exp-2.

Etymology. The generic name is a compound formed with the root of ‘karst’, which is the habitat of the new genus, prefixed to the existing generic name. The gender is masculine. The specific name is an accusative adjective, dedicated to Prof. Chia-Jui Shen, an excellent Chinese specialist on Copepoda and editor-in-chief of the book Crustacea: Freshwater Copepoda in a series of Fauna Sinica.

Figures

FIGURE 2. Karstodiaptomus sheni n. gen., n. sp.; female. A, habitus, dorsal view; B, antennule; C, rostrum, frontal view; D, pedigers 4 & 5 and urosome, dorsal view; E, antenna; F, mandible with mandibular palp; G, maxillula; H, maxilla, with details of tip of endopod; I, maxilliped. Scale bars: A, D, 100 µm; B – C, E – I, 50 µm.

FIGURE 3. Karstodiaptomus sheni n. gen., n. sp.; female. A, P 1; B, P 2; C, P 3; D, P 4; E, P 5, posterior view. Scale bar: 100 µm.

FIGURE 4. Karstodiaptomus sheni n. gen., n. sp.; male. A, habitus, dorsal view; B, right antennule, with detail of geniculation area; C, P 5, with detail of left Exp- 2, posterior view; D, right leg 5, lateral view. Scale bars: 100 µm.