Elaphoidella ligorae, Watiroyram, Santi, Sanoamuang, La-Orsri & Brancelj, Anton, 2017

Watiroyram, Santi, Sanoamuang, La-Orsri & Brancelj, Anton, 2017, Two new species of Elaphoidella (Copepoda, Harpacticoida) from caves in southern Thailand and a key to the species of Southeast Asia, Zootaxa 4282 (3), pp. 501-525 : 511-518

Elaphoidella ligorae sp. nov.

( Figs. 7 –11)

Type locality. Khao Plu Cave , Khao Ro Subdistrict, Thung Song District, Nakhon Si Thammarat Province, southern Thailand ( Fig. 1 ).

Material examined. Holotype: adult female, length 460 µm (access No.: NHMUK 2016.650), completely dissected and mounted on one slide. Allotype: adult male, length 440 µm (access No.: NHMUK 2016.651), completely dissected and mounted on one slide. Paratypes: three females with egg sacs and three males, stored in 70% ethanol (access No.: NHMUK 2016.652–657); three females with egg sacs and three males, stored in 70% ethanol (access No.: NPU 2016–002). The material was collected from Khao Plu Cave (loc. typ.) by S. Watiroyram on 29 October 2015.

Etymology. The specific name ligorae , refers to the settlement name of Ligor from the 16th century, which today is known as Nakhon Si Thammarat, the locality where the new species was collected. The species epitheton is the feminine singular genitive.

Description of female. Body length, measured from anterior margin of rostrum to posterior margin of caudal rami, 430–490 µm (mean = 450 µm, n = 5). Habitus ( Fig. 7 A) elongated, subcylindrical; maximal width at posterior margin of cephalothorax; preserved specimens colourless; naupliar eye not discernible. Cephalothorax with several pairs of sensilla, integumental window well discernible, and expanded anteriorly. Posterior margins of prosomites and urosomite 1 smooth, with several pairs of sensilla on each somite. Genital double-somite ( Figs. 7 A–D) about 0.8 times as long as wide, completely fused; with a row of strong spinules dorsally, ventrally and laterally; with distinct gap on dorsal and ventral rows. Genital complex ( Fig. 7 C) with a large bell-shaped copulatory pore; seminal receptacles symmetrical and well developed. Urosomites 2–4 serrated along entire free margins. Urosomite 3 with a row of strong spinules dorsally, laterally and ventrally, and a row of dorsal spinules with a gap in middle. Urosomite 4 with two strong spinules laterally and a group of small spinules vertically along distal margin. Anal somite ( Figs. 7 B–D) with one pair of thin sensilla dorsally, at base of anal operculum; no spinules ventrally at base of caudal ramus.

Anal operculum ( Figs. 7 B, D) large, with a row of numerous fine spinules along free margin; not reaching distal end of anal somite.

Caudal rami parallel ( Figs. 7 B, C). Caudal ramus asymmetrically conical, about 1.5 times as long as wide, with a well developed dorsal keel. Inner margin with several strong spinules at distal half of caudal ramus. Anterolateral accessory seta (I) reduced, and inserted close to seta II. Setae II, III, VI, VII bare and thin. Anterolateral seta (II) inserted at about 1/3 of caudal ramus length, as long as caudal ramus. Posterolateral seta (III) at 2/3 of caudal ramus length, slightly shorter than anterolateral seta (II). Outer terminal seta (IV) about two times as long as caudal ramus, spiniform, without a breaking plane. Inner terminal seta (V) longest, pinnate, without a breaking plane. Inner accessory seta (VI) slightly shorter than seta III. Dorsal seta (VII) slightly longer than seta II, inserted on the end of dorsal keel.

Antennule ( Fig. 8 A) relatively short, eight-segmented, not reaching posterior margin of cephalothorax. Aesthetasc on segment 4 reached well beyond distal segment. Second aesthetasc on last segment long and slim. Both aesthetascs combined with seta as an acrotheck. Setal formula: 1, 8, 5, 3+aesthetasc, 2, 2, 2, 7+aesthetasc.

Antenna ( Fig. 8 B) composed of coxa, allobasis, one-segmented Exp and Endp. Coxa as long as wide, unornamented. Allobasis with two short spinules at half the length of inner margin. Exp with four unipinnate setae, unequal in length (laterally two thin setae; apically one stout and one thin seta). Endp laterally with two strong spines at distal half of segment and two rows of strong spinules along inner margin, proximal row with five spinules, and distal row with two spinules. Apically five elements; three geniculate, one thin and one spine-like seta; outer surface of Endp with thin seta inserted subapically.

Mandible ( Fig. 8 C) robust, with eight strongly chitinized teeth and one unipinnate seta on dorsal side of gnathobase. Mandibular palp two-segmented; proximal segment with smooth seta; distal segment with smooth seta at half the length of margin and four unequal setae apically.

Maxillule ( Fig. 8 D) composed of robust praecoxa, coxa, and basis. Praecoxal arthrite with four strong spines on arthrite base, unequal in length. Coxa with a cylindrical endite bearing two pinnatae setae. Basis with a smooth seta and pinnate seta apically; three smooth setae along inner margin representing reduced Exp and Endp.

Maxilla ( Fig. 8 E) two-segmented; syncoxa with two endites, each with two setae. Basis drawn out into strong, beak-like spine with few distal spinules; Exp and Endp reduced to two smooth setae.

Maxilliped ( Fig. 8 F) prehensile; comprising syncoxa, basis, and one-segmented Endp. Syncoxa unornamented. Basis more than two times as long as wide, with about 15 spinules along inner margin. Endp drawn out into a smooth, curved claw, as long as basis; with a small seta at its base.

P1 with three-segmented Exp and Endp; P2–P4 with three-segmented Exp and two-segmented Endp. The armature formula of P1–P4 is as follows (legend: inner-outer seta/spine; inner-apical-outer; Arabic numerals represent setae, Roman numerals represent spines):

Leg Coxa Basis Exopod Endopod

1 2 3 1 2 3

1 0-0 1-I 0-I 1-I 0-2+I-I 1-0 1-0 0-2+I-0 2 0-0 0-I 0- I 1-I 1-2 +I-I 1-0 2- 2-I ---- 3 0-0 0-1 0-I 1-I 2- 2-II 0-0 2- 2-I ---- 4 0-0 0-1 0-I 1-I 2- 2-II 0-0 2-1+I-0 ---- P1 Exp as long as Endp-1 and Endp-2 combined; Exp and Endp with strong spinules along outer margins (Fig. 9A). Coxa with rows of small spinules on outer margin. Basis with thin inner and stout outer seta, and spinules at base of both elements; an additional row of spinules at insertion of Endp-1. Exp-1–3 similar in length, each with a strong spine on outer margin. Exp-2 with thin and bare seta on inner margin. Exp-3 with three elements apically; a strong unipinnate spine and two long geniculate setae. Endp-1 longer than Exp-1 and Exp-2 combined, with unipinnate spiniform seta on inner margin. Endp-2 with smooth seta on inner margin. Endp-3 two times as long as wide, with three setae apically; innermost seta thin, middle one geniculated and longest, outermost spiniform, as along as innermost one.

P2 (Fig. 9B) coxa with a short row of spinules on outer margin. Basis with stout seta on outer margin and few strong spinules at its base. Exp-1–3 with strong spinules on outer margin. Exp-1 as long as Exp-2. Exp-1 and Exp- 2 each with a strong spine on outer margin. Exp-2 with long unipinnate seta on inner margin. Exp-3 3.5 times as long as wide, with a spine and two pinnate setae apically; an unipinnate seta on inner margin. Endp-1 small, shorter than wide, with smooth seta on its inner margin. Endp-2 about 3 times as long as wide, with a spiniform spine on outer margin, two long pinnate setae apically, and two short and smooth setae on inner margin.

P3 (Fig. 9C) coxa ornamented as P2; basis with thin seta on outer margin, with few spinules at its base. Exp-1 slightly longer than wide; with a strong spine having a rounded tip on outer margin. Exp-2 with short unipinnate seta on inner margin and a strong spine with a rounded tip on outer margin. Exp-3 with two setae on its inner margin, proximal seta unipinnate, and distal one pinnate; apical margin with two pinnate setae; outer margin with two strong spines. Endp-1 small, shorter than wide, without seta on inner margin. Endp-2 about four times as long as wide, with a spine on outer margin subapically, two long pinnate setae apically and two smooth setae on inner margin.

P4 (Fig. 9D) coxa with few spinules on outer margin. Basis with thin smooth seta on outer margin. Exp-1–2 similar in length, about 1.3 times as long wide. Exp-2 with unipinnate spiniform seta on inner margin. Exp-3 about 3.5 times as long as wide, with two spines on outer margin, two pinnate seta apically and two setae on inner margin (proximal one unipinnate, spiniform; distal seta long, pinnate). Endp two-segmented, as long as Exp-1. Endp-1 shorter than wide, without seta on inner margin. Endp-2 about four times as long as wide, with a spine and long pinnate seta apically; two smooth setae on inner margin.

P5 (Fig. 9E) Exp and baseoendopod well separated. Baseoendopod shorter than half of Exp; with four strong spiniform setae; second inner one (II) longest followed by innermost seta (I), second outer one (III), and outermost seta (IV). Outer lateral seta on baseoendopod long and bare. Exp subrectangular, with four strong spiniform setae: second inner seta (II) longest followed by second outer seta (III) and outermost (IV); innermost seta (I) shortest.

Additional ornamentation of P1–P5 as in Figs. 9A–E.

P6 ( Fig. 7 C) fused, small, forming a simple plate, with two pinnate setae on each side of copulatory pore; inner one longer than outer one.

Egg sac: holotype with 10 eggs; other females with 6–12 eggs (n = 5).

Description of male. Slightly smaller than female; body length, measured from the anterior margin of rostrum to posterior margin of caudal rami, 420–460 µm (mean = 450 µm, n = 5); preserved specimens colourless; naupliar eye not discernible. Cephalothorax with a well discernible integumental window having anterior and posterior sections expanded. Habitus similar to female but tapering posteriorly. Urosomites serrated along entire free margins, urosomite 1 without spinulation. Urosomite 2 dorsally and laterally with a row of spinules and two groups of spinules ventrally on posterior margins. Urosomites 3 and 4 dorsally, laterally and ventrally with a row of spinules on posterior margins, dorsal rows with gap in middle. Urosomite 5 with a row of spinules laterally. Anal somite with three small ventral spinules near insertion of caudal rami. Caudal rami, antenna, mouthparts, P1 and P2 similar to those of female ( Figs.10 A–D, 11A–B).

FIGURE 9. Elaphoidella ligorae sp. nov. Female: A, P1; B, P2; C, P3; D, P4; E, P5. Scale bar: 50 µm.

FIGURE 11. Elaphoidella ligorae sp. nov. Male: A, P1; B, P2; C, P3; D, P4; E, P5. Scale bar: 50 µm.

Antennule ( Fig. 8 G) seven-segmented. First aesthetasc cylindrical, not reaching distal end of antennule. Second aesthetasc shorter than first one, about 1.2 times as long as terminal segment. Both aesthetascs combined with adjacent setae as an acrotheck. Setal formula: 1, 6, 8, 5+aesthetasc, 0, 0, 8+aesthetasc.

P3 (Fig. 11C) coxa, basis and Exp as in female. Endp three-segmented, slightly longer than Exp-1. Endp-1 shorter than wide, without seta on inner margin. Endp-2 with a short apophysis shaped in a harpoon-like tip, reaching the end of Exp-2. Endp-3 about two times as long as wide, with two pinnate setae apically; inner one small, shorter than segment bearing it; outer one long, about two times as long as segment.

P4 (Fig. 11D) coxa, basis and exopodite as in female. Endp two-segmented, as long as Exp-1. Endp-1 shorter than wide, without seta on inner margin. Endp-2 about two times as long as wide, with a spine and pinnate seta apically; smooth seta on inner margin.

Additional ornamentation of P1–P4 as in Figs. 11A–D.

P5 (Fig. 11E) Exp and baseoendopod distinctly separated. Outer lateral seta on baseoendopod long and smooth. Exp small, oval, with four spiniform setae: second inner seta (II) longest followed by second outer seta (III) and innermost (I); outermost seta (IV) shortest. Baseoendopod with no elements.

P6 ( Fig. 10 C) represented by a simple bilobate plate, with a smooth free margin.

Variability. Not found.

Figures

FIGURE 1. The geographical distribution of the genus Elaphoidella Chappuis, 1929 in Southeast Asia. Black dots indicate approximate locations of Elaphoidella sampling sites; arrows indicate locations of two new species. Numbers are the same as in Table 1.

FIGURE 7. Elaphoidella ligorae sp. nov. Female: A, habitus, dorsal view; B, urosome (without urosomite 1), dorsal view; C, urosome (without urosomite 1), ventral view; D, urosome (without urosomite 1), lateral view. Scale bar: 50 µm.

FIGURE 8. Elaphoidella ligorae sp. nov. Female: A, antennule; B, antenna; C, mandible; D, maxillule; E, maxilla; F, maxilliped. Male: G, antennule. Scale bar: 50 µm.

FIGURE 10. Elaphoidella ligorae sp. nov. Male: A, habitus, dorsal view; B, urosome (without urosomite 1), dorsal view; C, urosome (without urosomite 1), ventral view; D, urosome (without urosomite 1), lateral view. Scale bar: 50 µm.