Elaphoidella quangnamensis, Tran & Phung & Watiroyram, 2025

Tran, Ngoc-Son, Phung, Khanh Chuyen & Watiroyram, Santi, 2025, Elaphoidella quangnamensis sp. nov. (Copepoda, Harpacticoida, Canthocamptidae), a new hyporheic species from central Vietnam, Subterranean Biology 53, pp. 13-29 : 13-29

Elaphoidella quangnamensis sp. nov.

Etymology.

The specific name refers to Quang Nam Province, where the species was discovered. Latin suffix - ensis, meaning “from”, hence quangnamensis refers to from Quang Nam.

Type locality.

Hyporheic zone of the Vu Gia stream (15°22'41"N, 108°15'33"E, 90 m a. s. l.) in Tra Duong Subdistrict , Bac Tra My District, Quang Nam Province, central Vietnam (Fig. 1 ).

Material examined.

Holotype: • adult female, completely dissected and mounted on one slide; deposited in the Zoological Collection of Duy Tan University, Da Nang City, Vietnam (access No: ZC-DTU-COPEPODA-0014 ) . Paratypes: • five females stored in 70 % alcohol (access No: ZC-DTU-COPEPODA-0015 ). All material collected by Ngoc-Son Tran on March 20, 2024, in the hyporheic zone of the Vu Gia stream .

Description of female.

Body length (holotype), measured from anterior margin of rostrum to posterior margin of caudal rami 410 µm (n = 6; 361–477 µm, mean = 420 µm). Habitus (Fig. 2 A ) elongated, subcylindrical, tapering posteriorly. Rostrum small, curving backward. Cephalothorax wider than the rest of the body, with well discernible integumental window with three lobes. Prosomites 2–4 with serrated hyaline frill. First to fourth urosomites with serrated hyaline frill dorsally and laterally (Fig. 2 A, B ). Somite of genital double-somite completely fused (Fig. 2 F ), about 0.8 times as long as wide, with several rows of spinules on latero-ventral side. Genital complex with large copulatory pore, sclerotized, bell-shaped; seminal receptacles small, well sclerotized, symmetrical. Anal somite with row of small spinules on proximal part, circumvent the somite. Pair of sensilla at base of anal operculum dorsally. Several strong spines laterally at 1 / 2 length of somite. Row of thin spinules on both side of anal sinus. Two strong spines near inner corner of base of each caudal ramus ventrally. Anal operculum (Fig. 2 C ) large, slightly curved, with 38–41 fine spinules along free margin; not reaching distal end of anal somite.

Caudal rami (Fig. 2 C , 2 D ) trapezoidal in shape, parallel, about 1.2 times as long as wide, with a small dorsal keel. Inner margin smooth. Anterolateral accessory seta (I) absent. Anterolateral seta (II) inserted at about 1 / 3 of caudal ramus length, with small spine near its base. Posterolateral seta (III) smooth, inserted at near 1 / 2 of caudal ramus length, as long as seta II, with two strong spines near its base. Outer apical seta (IV) about 2.4 times as long as caudal ramus, smooth, with large swelling at base. Inner apical seta (V) longest, distal two-thirds pinnate, without fracture plane. Inner accessory seta (VI) thin, about 0.6 times as long as seta IV. Dorsal seta (VII) articulated, about 1.5 times as long as caudal ramus, inserted at 2 / 3 of caudal ramus length.

Antennule (Fig. 3 A ) relatively short, eight-segmented, not reaching posterior margin of cephalothorax. Aesthetasc on segment 4 cylindrical, with rounded tip, reached middle of distal segment. Aesthetasc on terminal segment long and slim. Setal formula as follows: 1, 9, 4, 2 + ae, 1, 3, 1, 9 + ae. All setae bare except that on first segment as unipinnate seta.

Antenna (Fig. 3 B ) with short bare coxa. Allobasis about 2.6 times as long as wide; inner margin with three spinules. One-segmented Exp and Enp. Exp with one unipinnate and one bipinnate apical setae, one unipennate subapical seta, one lateral unipennate seta; all setae of subequal length. Enp with six elements apically, from inner to outer: one spine, one smooth seta, three geniculate seta, one small bare seta; strong spine along inner margin associates with several robust spinules.

Mandible (Fig. 3 C ) short and robust, with five strongly chitinized teeth on gnathobase, dorsal seta near gnathobase. Mandibular palp two-segmented; first segment with one thin and short seta; second segment with one seta laterally and four setae, unequal in length, apically; all setae bare.

Maxillule (Fig. 3 D ) composed of robust praecoxa, coxa, and basis. Praecoxal arthrite with five strong spines on arthrite base; one bare seta on anterior surface. Spines unequal in length, all with acute tips; one bipinnate, one unipinnate and three bare. Coxa with pinnate spiniform seta. Basis with smooth seta and pinnate spiniform seta apically; four smooth setae along inner margin represent reduced Exp and Enp.

Maxilla (Fig. 3 E ) two-segmented, composed of syncoxa and allobasis. Syncoxa with two endites; proximal endite with two unipinnate setae and one smooth seta; distal endite with two unipinnate setae; all setae subequal in length. Allobasis drawn out into a strong serrate claw, with two bare setae near base represented Enp and Exp.

Maxilliped (Fig. 3 F ) comprising syncoxa, basis and Enp. Syncoxa with row small spinules on distal part along inner margin. Basis 2.4 times as long as wide, with row of spinules along inner margin, one short spinule on distal outer margin. Enp drawn out into smooth, curved claw, longer than the basis.

P 1 (Fig. 4 A ) with three-segmented Exp and Enp. P 2 – P 4 (Figs 4 B , 5 A, B ) with three-segmented Exp and two-segmented Enp. Armature formula of female P 1 – P 4 as follows (legend: inner-outer seta / spine; inner-apical-outer; Arabic numerals represent setae, Roman numerals represent spines):

P 1 (Fig. 4 A ) coxa with row of robust spinules on outer margin and row of small spinules on distal inner corner. Basis with pinnate seta on inner margin, accompanied with few robust spinules at its base; pinnate seta with two robust spinules at its base on outer margin; additional row of spinules at insertion of Enp- 1. Exp- 1 and Exp - 2 with strong pinnate spine on outer margin. Exp- 1 with several row spinules at anterior and outer margins. Exp - 2 with unipinnate seta on inner margin and row spinules on outer margin. Exp - 3 with row of spinules on outer margin; three elements apically: two smooth geniculate setae and one unipinnate spine; one smooth spine sub-apically. Enp- 1 reach mid-length of Exp - 2; one unipinnate seta at 3 / 4 length of inner margin; row or robust spines along outer and distal margin; several thin spinules on inner margin. Enp - 2 with one seta on inner margin and a row of robust spinules along outer margin. Enp - 3 about as long as Enp - 2, with row of robust spinules along outer margin; one subapical seta on inner margin; two elements apically: one geniculate seta and one unipinnate spine.

P 2 (Fig. 4 B ) coxa with a row of robust spinules on outer margin and a row of small spinules near inner margin. Basis with unipinnate seta on outer margin and few strong spinules at its base; with a row small spinules at base of Enp- 1. Exp- 1 and Exp - 2 with a strong spine and a row spinules along on outer margin each. Exp- 1 about 1.7 times as long as wide; ornamented with row of robust spinules on anterior proximal section and a row of small spinules along distal margin; several robust spinules along outer margin. Exp - 2 about as long as Exp- 1, with one unipinnate inner seta. Exp - 3 about 4.5 times as long as wide, as long as Exp- 1 and Exp - 2 combined; with five elements: one unipinnate seta on inner margin, two pinnate setae and one pinnate spine apically, one pinnate spine on outer margin; inner apical seta longest, about 2.6 times as long as Exp - 3, outer apical seta slightly shorter than inner apical seta. Enp- 1 short, about 0.7 times as long as wide, without seta on inner margin. Enp - 2 about three times as long as wide, with one unipinnate seta on inner margin; one soft long seta and one spiniform seta apically.

P 3 (Fig. 5 A ) coxa with a row of robust spinules on outer margin. Basis with long thin seta on outer margin, with few robust spinules at its base. Exp- 1 and Exp - 2 similar to those of P 2. Exp - 3 about four times as long as wide, with six elements: one unipinnate and one pinnate seta along inner margin, two plumose setae and one pinnate spine apically, one pinnate spine on outer margin at 2 / 3 of segment length. Enp- 1 about 0.5 times as long as wide. Enp - 2 about three times as long as wide; with few spinules on inner and outer margin; with five elements: one smooth and one unipinnate seta inserted close to each other at about mid-length of inner margin; three pinnate setae unequal in length apically; middle seta longest, about three times as long as Enp.

P 4 (Fig. 5 B ) coxa unornamented. Basis similar to P 3. Exp- 1 with transversal row of spinules on proximal anterior surface; with strong spine on distal outer corner and row of large spinules along outer margin. Exp - 2 slightly longer than Exp- 1, with row of strong spinules along outer margin; one unipinnate seta on inner margin and one strong pinnate seta on outer margin. Exp - 3 shorter than Exp- 1 and Exp - 2 combined; with six elements: two pinnate setae on inner margin; two pinnate setae and one pinnate spine apically; one pinnate spine on outer margin. Enp- 1 about 0.5 times as long as wide, naked. Enp - 2 about four times as long as wide; with three elements: one unipinnate seta on inner margin; one long plumose and one unipinnate seta apically; plumose seta about six times as segment bearing it.

P 5 (Fig. 2 E ) with separated Exp and baseoendopod. Baseoendopod well-developed, reaching to distal end of Exp; with four strong pinnate setae, unequal in length: second inner one (II) longest; outermost one (IV) shortest; innermost one (I) slightly longer than second outer seta (III); with a process extending between insertion of seta I and seta II. Exp suboval in shape, 1.3 times as long as wide, with four setae: three pinnate setae apically, one smooth seta on outer margin; seta length gradually decreases from inner to outer one.

P 6 (Fig. 2 F ) fused to somite, small, forming a simple plate, with one unipinnate seta on outer side; one smooth seta on inner side, reaching orifice of copulatory pore; inner seta longer than outer one; copulatory pore small, slightly chitinized.

Male. Not found.

Variation.

P 6 of female with one unipinnate seta and one smooth seta on left side, and one unipinnate setae on right side of copulatory pore as observed in one of six examined females.

Figures

Figure 1. The sampling location of Elaphoidella quangnamensis sp. nov.

Figure 2. Elaphoidella quangnamensis sp. nov., female holotype A habitus, dorsal view B urosome, lateral view C urosomite IV, anal somite and caudal rami, dorsal view D urosomite IV, anal somite and caudal rami, ventral view E P 5 F P 6 and genital complex.

Figure 3. Elaphoidella quangnamensis sp. nov., female holotype A antennule B antenna C mandible D maxillule E maxilla F maxilliped.

Figure 4. Elaphoidella quangnamensis sp. nov., female holotype A P 1 B P 2.

Figure 5. Elaphoidella quangnamensis sp. nov., female holotype A P 3 B P 4.