Schizopera paktaii, Watiroyram & Sanoamuang & Brancelj, 2021

Watiroyram, Santi, Sanoamuang, La-Orsri & Brancelj, Anton, 2021, New species of Elaphoidella Chappuis, 1929 and Schizopera Sars, 1905 (Copepoda Harpacticoida) from two caves in northeastern and southern Thailand, Zootaxa 5051 (1), pp. 550-569 : 559-566

Schizopera paktaii sp. nov.

( Figs. 7–11 )

(http://zoobank.org/ urn:lsid:zoobank.org:act:ABD44820-0ECE-4DA0-9516-CFCCB58B8E7F )

Type locality. Khao Chang Hai Cave , Na Muen Si Subdistrict, Na Yong District, Trang Province, southern Thailand; coordinates of the cave entrance: 07°35’24.65”N, 099°34’08.62”E; altitude: 45 m a.s.l. ( Fig. 1A, D–E ) .

Material examined. Holotype: adult female, length 510 µm (access no: NHMUK 2019.1007 ), completely dissected and mounted on one slide . Allotype: adult male, length 500 µm (access no: NHMUK 2019.1008 ), completely dissected on one slide . Paratypes: three adult females and three adult males, stored in 70% ethanol (access nos: NHMUK 2019.1009 – 1014 , NPU 2019-02).All specimens collected from the type locality on December 1, 2017 by Santi Watiroyram .

Etymology. Schizopera paktaii sp. nov. is named after the Paktai region (Thai name for the southern part of Thailand), where the species was collected. The species epithet is a feminine singular adjective.

Distribution. Known only from the pools fed by dripping water at the type locality.

Description of female. Body length measured from anterior margin of rostrum to posterior margin of caudal rami: 460–540 µm (mean = 520 µm, n = 5). Habitus elongate, cylindrical, slightly tapering posteriorly; preserved specimens colourless ( Figs. 7A ; 8A ). Cephalothorax rectangular, about 1.5 times as long as wide. Rostrum triangular, more than 2.0 times as long as wide, with pair of sensilla halfway rostrum length ( Fig. 7B ). Naupliar eye not discernible. Prosomites and urosomites dorsally with tiny spinules on posterior margins, continued by serrated hyaline frill dorso-laterally and ventrally on urosomites. Genital double-somite ( Figs. 7C–D ; 8B, D ), completely fused, as long as wide. Genital complex ( Fig. 7E ) with single copulatory pore and two small seminal receptacles. Anal somite ( Figs. 7F ; 8C, E ) with row of robust spinules dorso-laterally and ventrally; with oblique row of long hairs along inner margin, just below anal operculum.

Anal operculum ( Figs. 7F ; 8C ) well developed, broadly rounded; not reaching to end of anal somite; free margin with fine, short hairs.

Caudal rami parallel ( Figs. 7A, C, F ; 8A–B ). Caudal ramus subcylindrical, slightly tapering dorso-ventrally, about twice as long as wide; row of strong spinules dorsally at distal part of ramus, just above insertion of terminal caudal setae; three oblique rows of tiny spinules on dorsal surface; row of long hairs at distal 3/4 of inner margin. Caudal setae represented with six elements. Anterolateral accessory seta (I) absent. Anterolateral seta (II) strong, spiniform, about 0.3 times as long as ramus, located at 3/4 of ramus length. Posterolateral seta (III) slender, bare, about 0.5 times as long as ramus, inserted next to seta II. Outer apical seta (IV) slender, unipinnate, about twice as long as ramus, without breaking plane. Inner apical seta (V) longest, bipinnate, with breaking plane just posterior to swollen region, about 3.5 times as long as ramus. Inner accessory seta (VI) slender, bare, shorter than caudal width. Dorsal seta (VII) biarticulated, slender, as long as caudal ramus; positioned near inner margin at about 1/3 of caudal ramus length.

Antennule ( Figs. 8A, F ; 9A ) eight-segmented, short. Segments 1 and 2 swollen, oriented forward; other segments oriented laterally. Aesthetasc on segments 4 and 8 fused with seta at its base (forming acrothek on apical segment); aesthetasc on segment 4 larger and longer than distal one, reaching beyond tip of antennule; aesthetasc on segment 8 slim, about half length of former one. Setal formula: 1, 8, 6, 3 + a, 2, 4, 4, 6 + a.

Antenna ( Figs. 8G ; 9B ) comprising coxa, allobasis, one-segmented Enp and two-segmented Exp. Coxa unornamented. Allobasis about 2.5 times as long as wide, not completely fused; with unipinnate seta on median margin. Exp-1 with one unipinnate seta at inner corner distally. Exp-2 with one robust bipinnate seta and one slender, bare seta apically. Enp as long as allobasis, with several spinules and two strong spines along outer distal margin; apical margin with seven elements: three bare and four geniculate setae; additionally, Enp bearing two thin setae inserted sub-apically.

Mandible ( Fig. 9C ) robust, with seven strong chitinized teeth, one unipinnate seta on gnathobase. Mandibular palp two-segmented; proximal segment with three setae unequal in length, inserted distally, additional short seta at base of distal segment; distal segment with two lateral setae and five apical setae, unequal in length. All mandibular palp setae thin and bare.

Maxillule ( Fig. 9D ) comprising robust praecoxa, coxa, basis, Enp and Exp. Praecoxal arthrite with seven strong spines (one unipinnate, remaining spines bare) and one bare, slender seta; two additional setae positioned laterally on praecoxal surface. Coxal endite with one bare and one pinnate seta. Basis with one unipinnate, claw-like seta, one bipinnate and five bare apical setae, unequal in length. Enp about 1.5 times as long as wide, with three bare setae apically, unequal in length. Exp small, with two bare setae apically.

Maxilla ( Fig. 9E ) two-segmented; syncoxa with three endites, two proximal endites with one unipinnate and one bare seta; distal endite with two unipinnate setae. Basis drawn into strong, claw-like expansion, unipinnate. Exp and Enp reduced to two bare setae each.

Maxilliped ( Figs. 8I ; 9F ) prehensile. Coxobasis with three unipinnate setae on median margin, with few strong spinules on anterior surface. Two-segmented Enp; Enp-1 about 2.4 times as long as wide, with two bare setae and row of strong spinules along inner margin, row of setules on outer margin proximally. Enp-2 smaller than Enp-1, about twice as long as wide; with claw-like unipinnate spine and three bare setae apically.

P1–P4 with three-segmented Exp and Enp; P2–P4 intercoxal sclerites with acute projections on distal margin. Armature formula of P1–P4 as follows (legend: inner-outer seta/spine; inner-apical-outer; Arabic numerals represent setae, Roman numerals represent spines); distribution of spinules and hairs as shown in Fig. 10A–D :

P1 ( Fig. 10A ) Enp longer than Exp; Enp-1 slightly shorter than Exp, about 5.5 times as long as wide, with one slender, bare seta inserted on 3/4 length of inner margin; Enp-2 as long as wide; Enp-3 about twice as long as wide, with short bare seta on inner margin inserted subapically, one geniculate and one unipinnate seta on apical margin. Exp-1-2 with one spine on outer margin distally. Exp-3 with one spine on outer margin inserted subapically, two geniculate and one spiniform seta on apical margin.

P2 ( Fig. 10B ) Enp as long as Exp. Enp-2 with unipinnate seta in distal half on inner margin. Enp-3 with unipinnate seta in distal half on inner margin, two normal setae apically, subequal in length, longest one slightly longer than Enp. Exp-1-2 each with one spine on outer margin distally, as long as segment. Exp-3 with two setae and one spine apically; both setae as long as Exp; outer margin with spine inserted subapically.

P3 ( Fig. 10C ) Enp slightly shorter than Exp. Exp with armature similar to P2. Enp-1-3 each with one long plumose seta on inner margin inserted distally. Enp-3 with two plumose setae and one unipinnate spine apically, both setae subequal in length, longest seta longer than Enp.

P4 ( Fig. 10D ) with armature similar to P3 except Enp-3 without plumose seta on inner margin.

P5 ( Fig. 10E ) Exp and baseoendopod well separated. Seta on outer margin of baseoendopod long, thin, bare. Baseoendopod slightly shorter than Exp, with four long, strong spiniform setae; second outer seta (III) the longest, followed by second inner one (II), innermost seta (I) and outermost seta (IV); middle margin of baseoendopod with row of spinules. Exp small, subquadrangular, with five elements: second inner seta (II) the longest, about four times as long as segment, robust, bipinnate; innermost seta (I) spiniform, slightly longer than segment. Setae on outer margin bare, unequal in length.

P6 ( Fig. 7C, E ) reduced to simple plate, located near the base of copulatory tube, with one small bipinnate seta on outer side and one long bare seta on inner side. Outer seta about three times shorter than inner one.

Females ( Figs. 7A ; 8D ) with two egg sacs, each containing three large eggs (n = 5).

Description of male ( Figs. 8J ; 11A ). Slightly smaller than female; body length measured from anterior margin of rostrum to posterior margin of caudal rami: 470–530 µm (mean = 510 µm, n = 5). Habitus and ornamentation similar to female except number of urosomites (six compared with five in female), sexual dimorphism expressed in antennules, and caudal rami without long hairs on inner margin and lacking swollen region on inner apical seta (V) ( Figs. 8L ; 11C ).

Antennule ( Figs. 8M ; 11D ) eight-segmented, with minor geniculation between fifth and sixth segments. Aesthetascs on segments four and eight as in female. Setal formula: 1, 7, 8, 6 + a, 1 + 3s, 1, 4, 6 + a.

P1 ( Fig. 10F ) as in female, except basis with spine on inner margin transformed into finger-like process.

P2 ( Fig. 10G ) as in female except morphology and armature of Enp-2-3: Enp-2 with inner margin shaped into rounded lobe, with bare seta distally; outer distal part of segment produced into long apophysis. Enp-3 very small, slightly longer than wide, with two thin, bare equally long setae apically, accompanied by long unipinnate seta, twice as long as bare setae; unipinnate seta inserted subapically.

P3 ( Fig. 10H ) as in female except armature of inner margin of Exp-3: seta transformed into acute spine inserted on posterior surface of the segment near the inner margin, closely adpressed to segment, not reaching distal margin of Exp-3.

P4 ( Fig. 10I ) as in female.

P5 ( Fig. 10J ) Exp and baseoendopod well separated. Seta on outer margin of baseoendopod long, thin, bare. Baseoendopod slightly shorter than Exp, with two subequal spiniform setae, secondary setae limited to distal section of the armature. Exp as in female.

P6 ( Fig. 11B, E ) represented by simple unarmed bilobate plate.

Variability. Besides the differences in length among females and males, the only morphological variability was observed in one of the five examined male specimens showing a P6 which bears two tiny spinules on one side of the plate ( Fig. 11E ).

Figures

FIGURE 1. Sampling locations of the two new species from Thailand: (A) black circles: capital cities, black triangle: type locality of Elaphoidella isana sp. nov.; black square: type locality of Schizopera paktaii sp. nov.; (B–C), (D–E), images of sampling sites of Elaphoidella isana sp. nov., and Schizopera paktaii sp. nov., respectively.

FIGURE 7. Schizopera paktaii sp. nov., female: (A) habitus, dorsal view; (B) rostrum; (C) urosome, ventral view; (D) urosome, lateral view; (E) genital complex; (F) urosomite 4, anal somite and caudal rami, dorsal view.

FIGURE 8. Schizopera paktaii sp. nov., SEM photographs of female (A–I) and male (J–M): Female: (A) habitus, dorsal view; (B) urosome, dorsal view; (C) anal somite and caudal rami, dorsal view; (D) pediger 5 (with P5) and genital double-somite (with eggs), lateral view; (E) anal somite and caudal ramus, lateral view; (F) antennules; (G) antenna; (H) maxillule and maxilla; (I) maxilliped. Male: (J) habitus, dorsal view; (K) urosome, dorsal view; (L) anal somite and caudal rami, dorsal view; (M) antennule.

FIGURE 9. Schizopera paktaii sp. nov., female: (A) antennule; (B) antenna; (C) mandible; (D) maxillule; (E) maxilla; (F) maxilliped.

FIGURE 10. Schizopera paktaii sp. nov., female (A–E) and male (F–J): (A, F) P1; (B, G) P2; (C, H) P3, black arrow indicates a hyaline spine; (D, I) P4; (E, J) P5. All anterior view.

FIGURE 11. Schizopera paktaii sp. nov., male: (A) habitus, dorsal view; (B) urosomites 2 to 5, ventral view; (C) urosomite 6, anal somite and caudal rami, dorsal view; (D) antennule; (E) P6 plate.