Nannodiaptomus phongnhaensis Dang & Ho, 2001

Tran, Duc Luong & Brancelj, Anton, 2017, Amended diagnosis of the genus Nannodiaptomus (Copepoda, Calanoida), based on redescription of N. phongnhaensis and description of a new species from caves in central Vietnam, Zootaxa 4221 (4), pp. 457-476 : 460-467

Nannodiaptomus phongnhaensis Dang & Ho, 2001

( Figs. 2–6 )

Type locality. River in Hang Phong Nha Cave (17° 34' 59.0'' N, 106° 16' 55.0'' E), Quang Binh province, Central Vietnam.

Neotype designation. As the type material was lost, a neotype is designated. Neotype (total length 625 µm; IEBR-COP3418): male, collected on 0 9 August 2014; dissected and mounted in glycerol; deposited in the Institute of Ecology and Biological Resources ( IEBR), Hanoi, Vietnam .

Additional material. 10 males, 10 females, prepared for SEM examination; one adult male (IEBR-COP3419), one adult female (IEBR-COP3420), both dissected and mounted in glycerol; 8 males, 13 females (IEBR-COP- AED08.14.013) preserved in 70 % ethanol; deposited in the IEBR. 15 males, 15 females preserved in 70 % ethanol; deposited in the National Institute of Biology (NIB), Ljubljana, Slovenia. All specimens collected at the same locality and date as neotype.

One male (IEBR-COP3421), one female (IEBR-COP3422), both dissected and mounted in glycerol; 30 males, 30 females (IEBR-COP-AED04.14.021) preserved in 70 % ethanol; all deposited in the IEBR. Material collected on 19 April 2014 from two pools inside Hang Va Cave (17° 29' 22.3" N, 106° 17' 04.8" E), Quang Binh province, Central Vietnam.

Description of female. Total length (without caudal setae) 595–670 µm, mean 640 µm (N= 25). Preserved specimens colourless and eyeless. Body ( Fig. 2 A) slender with maximum width at middle of Pd1. Mean prosome length: 445 µm; mean urosome length: 194 µm; prosome/urosome ratio 2.3 (N= 10). Rostrum represented by pair of large finger-like filaments, with pointed tips ( Figs. 5 C, D; 6L). Pd4 and Pd5 fused, dorsal and lateral spinules lacking. Lateral wings of Pd5 moderately developed, nearly symmetrical, with rounded posterolateral margins, smooth, without sensilla/spines ( Figs. 2 C, D; 6H).

Urosome ( Fig. 2 A) of 3 free somites (ratio of Ur1: Ur2: Ur3: CR = 0.53: 0.12: 0.16: 0.19). Ur1 (genital doublesomite) ( Figs. 2 C–E, 6H) about 2-times as long as wide, slightly asymmetrical in dorsal view; without sensilla.

Genital field with pair of gonopores located mid-ventrally, gonopores completely covered by large genital operculum; genital area large, sac-like ( Fig. 2 E); spermatophore insertion point on left posterolateral corner of somite. Ur2 small, cylindrical, about 0.7 times as long as wide. Ur3 (anal somite) slightly shorter than caudal rami, with concave lateral margins. Anal operculum small, semicircular, posterior margin smooth.

Caudal rami ( Fig. 2 A) symmetrical, 1.8–2.1 times as long as wide (mean 1.9, N=10). Inner and outer margins smooth; with 5 plumose setae (setae II–VI) and articulated smooth dorsal seta (VII), inserted on inner distal corner; seta I lacking. Length of setae II–VI increases from outer to inner; seta VI 1.6 times as long as seta II; seta VII longest.

Antennule ( Fig. 3 A) 25-segmented, reaching beyond posterior margins of caudal rami. Seta on segment 1 short, not reaching distal margin of segment 2. Largest setae on segments 3, 7, 9, 14, 21–25. Armature of segments as follows (Arabic numerals = evident segments; a—aesthetasc; S—seta; sp—spine): 1(S+a), 2(3S+a), 3(S+a), 4(S), 5(S+a), 6(S), 7(S+a), 8(S+sp), 9(2S+a), 10(S), 11(S), 12(S+sp+a), 13(S), 14(S+a), 15(S), 16(S), 17(S), 18(S), 19(S+a), 20(S), 21(S), 22(S+S), 23(S+S), 24(S+S), 25(4S+a).

Antenna ( Fig. 3 B) with Exp as long as Endp; coxa small, with 1 seta; basis robust with 2 setae on inner distal corner. Endp 2-segmented; proximal segment elongated, 3.7 times as long as wide, with 2 setae at 1/2 length of inner margin; distal segment with 2 lobes. Outer lobe with 6 long setae terminally and 1 short sub-terminal seta; inner lobe with 1 short seta, 2 medium-sized and 5 long setae. Exp 7-segmented; segment 1 with 1 seta, segment 2 with 3 setae, 1 seta on each of segments 3–6, terminal segment with 1 lateral and 3 apical setae.

Mandible ( Fig. 3 C) with 7 small teeth on gnathobase; ventral tooth medium sized. Basis with 4 sub-equal setae, proximal one plumose. Endp 2-segmented, proximal segment with 4 setae, distal segment with 8 setae. Exp 4-segmented with 1, 1, 1, 3 setae; ancestral segments 4 and 5 fused.

Maxillule ( Fig. 3 D) with 9 apical spiniform and 4 plumose setae on posterior surface of praecoxal arthrite. Coxal epipodite with 7 long setae and 2 short spiniform setae. Basal exite with 1 small spine-like seta. Coxal and first basal endites with 4 setae each. Basis and Endp fused, with 5 setae laterally and 8 setae apically. Exp with 6 long setae.

Maxilla ( Fig. 3 E) with 2 praecoxal and 2 coxal lobes, with 5, 3, 3, 3 setae, respectively. Basal lobe well developed, with 3 long setae. Endp 2-segmented, proximal one with 2 setae, distal one with 3 setae.

Maxilliped ( Fig. 3 F) well developed. Syncoxa with 4 endites with 1, 2, 3, 4 unequal setae. Distal endite of syncoxa with well developed protuberance projecting over basis. Basis elongated, with 3 plumose setae increasing in length distally, inserted near 1/2 length of inner margin. Endp 6-segmented, segment 1 partially incorporated into the basis. Segment 1 with 2, segment 2 with 3 sub-equal setae; segments 3–5 with 2, 2, 1+1, segment 6 with 4 setae, respectively.

P1–P4 ( Figs. 2 F–I) with 2-segmented Exp and 1-segmented Endp; coxa and basis without seta. P1–P4 Endp-1 and Exp-2 with setules along inner margin. Armament of swimming legs as follows (Roman numerals—spines; Arabic numerals—seta; outer-apical-inner position of element):

P5 ( Figs. 5 E, 6I, K). Coxa sub-cylindrical, about 1.4 times as long as wide; posterior surface with small protuberance bearing short spine at 2/3 of coxa length. Bases asymmetrical; left basis triangular, slightly larger than right one; right one’s inner margin convex. Left Endp small, triangular, with rounded tip, no armature; right Endp lack. Exp 2-segmented on both sides; Exp-1 about 2.1 times as long as wide, cylindrical; Exp-2 short, prolonged into robust terminal claw-like apophysis, with row of small spinules along both margins; lateral spine lack.

Description of male. Total length (without caudal setae) 525–640 µm, mean 615 µm (N=25). Mean prosome length: 438 µm; mean urosome length: 193 µm; prosome/urosome ratio 2.3 (N= 10). Preserved specimens colourless and eyeless. Body slender, with typical diaptomid shape ( Fig. 4 A). Rostrum represented by pair of finger-like filaments with pointed tips. Pd4 and Pd5 fused. Pd5 slightly asymmetrical ( Figs. 4 A, C), with rounded posterolateral margins, lack dorsal ornamentation or sensilla.

Urosome ( Fig. 4 A) with 5 free somites; somites ratio 1–5 + CR as follows: 0.22: 0.18: 0.13: 0.13: 0.14: 0.20. Ur1 (= genital somite) asymmetrical; middle part of left lateral margin slightly protuberant, expanded; sensilla lack on both margins of somite. Dorsal and ventral surface of Ur2–5 un-ornamented; posterior margins smooth.

Caudal rami symmetrical, 1.7–2.0 times as long as wide (mean 1.8, N= 10), with inner and outer margins smooth. Setae II–VI plumose; dorsal seta (VII) articulated, smooth, inserted on inner distal corner of caudal ramus. Length of caudal setae II–VI increases from outermost to innermost; seta VI 1.2 times as long as outer seta (II). Dorsal seta (VII) 1.3 times as long as seta VI.

Antennule shorter than in female, reaching distal part of caudal rami. Right antennule with 22 evident segments ( Figs. 5 A, B), with largest setae on segments 3, 7, 9, 14, 19, 20, 21; none of segments especially broadened. Segments 8, 10–13 each with short spine-like seta. Segments 17-19 with 1 large, knife-like spine each. One small aesthetasc on segments 1, 2, 3, 5, 7, 9, 12, 14, 15, 16, 19, 22. Armature segments as follows (Arabic numerals = evident segments; a—aesthetasc, S—seta, sp—spine): 1(S+a), 2(3S+a), 3(S+a), 4(S), 5(S+a), 6(S), 7(S+a), 8(S+sp), 9(2S+a), 10(S+sp), 11(S+sp), 12(S+sp+a), 13(S+sp), 14(2S+a), 15(S+a), 16(2S+a), 17(S+sp), 18(sp), 19(S+sp+a), 20(2S+2S), 21(S+S), 22(4S+a). Setation of left antennule as in female.

Antennae, mouthparts and P1–P4 as in female.

P5 asymmetrical, coxae on posterior side each with 1 spine at 2/3 of length of segment, unequal in size ( Fig. 4 F). Right P5 ( Figs. 4 F; 6A–C, G): basis about 1.4 times as long as wide, with large, semicircular and flattened hyaline lobe along full length of inner margin. Exp-1 short and trapezoidal, 1.1 times as long as wide, with narrow hyaline lamella along inner margin; distal margin with small rounded lobe. Exp-2 oval, about 1.4 times as long as wide, outer margin convex, outer lateral spine curved, inserted at 2/3 length of segment, extending beyond distal margin of Exp-2. Exp-2 claw slender, almost semicircular, 2.2 times as long as Exp-2; inner margin with a short row of tiny spinules. Endp lack.

Left P5 ( Figs. 4 E–G; 6A, C–F) reaching posterior margins of right P5 Exp-2. Basis cylindrical, elongated, 1.8 times as long as wide, without lateral seta. Exp-1 about 2.2 times as long as wide, with row of setules on inner margin. Exp-2 rounded, inner margin with field of short setules. Apical process slightly shorter than segment bearing it, with 3–4 denticular protrusions along inner margin. Subterminal lateral seta stout, spiniform, about twice as long as apical process, with 3 denticular protrusions on inner 2/3 margin length. Endp 1-segmented, elongated, with width/length ratio of 2.3, laterally curved, about half as long as basis; with group of short setules apically.

Figures

FIGURE 2. Nannodiaptomus phongnhaensis Dang & Ho, 2001. Female: A, habitus, dorsal view; B, detail of setulation of terminal caudal setae; C, pedigerous somites 4 and 5 and genital double-somite, dorsal view; D, pedigerous somites 4 and 5, genital double-somite and leg 5, lateral view; E, genital double-somite, ventral view; F, leg 1; G, leg 2; H, leg 3; I, leg 4. Scale bars: 100 µm.

FIGURE 3. Nannodiaptomus phongnhaensis Dang & Ho, 2001. Female: A, antennula; B, antenna; C, mandible; D, maxillula; E, maxilla; F, maxilliped. Scale bars: 100 µm.

FIGURE 4. Nannodiaptomus phongnhaensis Dang & Ho, 2001. Male: A, habitus, dorsal view; B, setulation of terminal caudal setae; C, pedigerous somites 4 and 5, genital somite and urosomite 2, dorsal view; D, right leg 5, lateral view; E, left leg 5, lateral view; F, leg 5 posterior view; G, left leg 5, detail of basis, Exp and Endp. Scale bars: A – F, 100 µm; G, 10 µm.

FIGURE 5. Nannodiaptomus phongnhaensis Dang & Ho, 2001. Male: A, right antennule, evident segments 1 – 13; B, right antennule, evident segments 14 – 22. Female: C, rostrum, lateral view; D, rostrum, ventral view; E, leg 5, posterior view. Scale bars: A – D, 100 µm; E, 10 µm.

FIGURE 6. Nannodiaptomus phongnhaensis Dang & Ho, 2001. SEM micrographs. Male: A, leg 5, anterior view; B, leg 5, lateral view; C, leg 5, posterior view; D – F, left side of leg 5, distal part; G, right leg 5, Exp- 2. Female: H, last prosomites and genital double-somite, dorsal view; I, leg 5, anterior view; K, leg 5, posterior view; L, rostrum, ventral view.