Rangabradya (Siamorangabradya) wongkamhaengae, Boonyanusith & Athibai, 2021

Boonyanusith, Chaichat & Athibai, Sujeephon, 2021, A new species of Rangabradya (Copepoda, Harpacticoida, Ectinosomatidae) from a cave in Satun Province, southern Thailand, ZooKeys 1009, pp. 45-66 : 45

publication ID	https://dx.doi.org/10.3897/zookeys.1009.54554
publication LSID	lsid:zoobank.org:pub:5400526C-94CA-4E73-B738-57427B8635DD
persistent identifier	https://treatment.plazi.org/id/17517BF1-EA91-46A4-98C5-66F8144065DF
taxon LSID	lsid:zoobank.org:act:17517BF1-EA91-46A4-98C5-66F8144065DF
treatment provided by	ZooKeys by Pensoft
scientific name	Rangabradya (Siamorangabradya) wongkamhaengae
status	sp. nov.

Treatment

Rangabradya (Siamorangabradya) wongkamhaengae sp. nov. Figures 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7A View Figure 7 , 9 (female); 7B, 8, 10 (male) View Figure 9

Material examined.

Holotype: Thailand • 1 ♀ (adult), 485 μm long; Satun Province, Khay Cave; 6°53'40"N, 99°46'44"E, 17 m a.s.l.; 17 Dec. 2014; C. Boonyanusith leg.; hand net; completely dissected and mounted on a slide in glycerol and sealed with nail polish; PSUZC-PK2005-01. Allotype: Thailand • 1 ♂ (adult), 428 μm long, collection data as for holotype; PSUZC-PK2005-02. Paratypes: Thailand • 1 ♀ (adult) and 1 ♂ (adult); same data as for holotype; PSUZC-PK2005-03 and PSUZC-PK2005-04, respectively.

Additional material.

Thailand • 3 ♂♂ (adult), 1 ♀ (adult), 3 copepodids; same data as for holotype; preserved in 70% ethanol; retained in collection of the first author (CB).

Type locality.

Khay Cave in La-Ngu District, Satun Province, Thailand. The cave’s geography and morphology have previously been described in Boonyanusith et al. (2020) (Fig. 1 View Figure 1 ).

Description of female.

Total body length, excluding caudal setae, 485-489 µm (mean = 487; N = 3). Preserved specimens colourless. Habitus fusiform, gradually tapering posteriorly, with maximum width at posterior margin of cephalothorax (Figs 2A View Figure 2 , 9A View Figure 9 ). Rostrum (Fig. 2B View Figure 2 ) well developed, broadly rounded, completely fused with cephalothorax, with two lateral sensilla near base. Prosome ca 1.6 × as long as urosome (including caudal rami), comprising cephalothorax and three free pedigerous somites. Cephalothorax ca 1.1 × as long as wide and ca 0.5 × as long as length of prosome; posterior margin smooth. Distribution of sensilla and cuticular pores as illustrated (Figs 2A View Figure 2 , 9B View Figure 9 ). All free pedigerous somites dorsally with a pair of pores on anterior margin; finely spinulated hyaline frill incised on posterior margin.

Urosome comprising fifth pedigerous somite, genital double-somite, and three free abdominal somites (Fig. 2A View Figure 2 ). Posterior margin of all urosomites with finely spinulated hyaline frill, except anal somite; hyaline frill on genital double-somite and subsequent somite uniform in width dorsally and laterally, and central part wider than outer parts ventrally (Fig. 3A, B View Figure 3 ). Ornamentation as illustrated (Figs 2A View Figure 2 , 3A, B View Figure 3 ). Fifth pedigerous somite wider than long, dorsally with pair of cuticular pores near anterior margin plus continuous row of minute spinules and four sensilla along posterior margin (Fig. 2A View Figure 2 ). Two rows of spinules lateroventrally, positioned next to implantation of P5, with one pore close to tip of proximal row (Figs 7A View Figure 7 , 9G View Figure 9 ). Genital double-somite slightly wider than long, with three pores dorsally, arranged in triangle. Two sensilla near posterior margin and three rows of minute spinules dorsally on anterior half of double-somite; distal row with short gap medially (Fig. 3B View Figure 3 ). Ventrally a pore on either side of copulatory pore and two transverse rows of minute spinules along medial margin. Antero-laterally with three additional rows of relatively strong spinules, continuing into rows of spinules dorsally. Genital field (Fig. 3B View Figure 3 ) with small copulatory pore medially, at 1/3 of the double-somite length. Short seta representing P6 on peduncle. Second and third abdominal somites, with one single pore mid-dorsally, near anterior margin plus pair of sensilla dorsally, near posterior margin and row of minute spinules, next to cuticular pore. Ventrally pair of cuticular pores present in second abdominal segment, but absent in the subsequent one, with lateral and lateroventral row of spinules anteriorly. Additional row of spinules ventrally, near posterior margin. Third abdominal somite with cuticular bell-shaped flap dorsally, representing pseudoperculum. Anal somite with cleft medially, with two pairs of cuticular pores dorsally.

Caudal rami (Figs 2A View Figure 2 , 3A, C View Figure 3 ) slightly divergent, as long as anal somite, ca 1.3 × as long as wide, with transparent triangular lappets dorsally and ventrally, reaching beyond fracture plane of inner apical seta (V); each ramus armed with seven setae. Lateral accessory seta (I) minute (Figs 3A View Figure 3 , 10D View Figure 10 ). Lateral seta (II) and outermost apical seta (III) subequal in length. Outer apical seta (IV) and inner apical seta (V) well developed, with fracture plane; seta V longest, ca 1.3 × as long as seta IV. Innermost apical seta (VI) ornamented with spinules on inner margin, ca 1.5 × as long as seta II. Dorsal seta (VII) biarticulate, inserted at ½ length of ramus on medial margin, ca 1.5 × as long as seta II.

Antennule (Figs 4A View Figure 4 , 9C View Figure 9 ) short, six-segmented. Third segment longest, with robust and curved aesthetasc, reaching well beyond tip of antennule. Ultimate segment incompletely separated from preceding one, with remnant of ancestral articulation and aesthetasc on tip of segment. Both aesthetascs combined as acrothec (common base of seta and aestetasc). Armature formula: 1-[1], 2-[8], 3-[5 + 1 pinnate + (1 + ae)], 4-[2], 5-[2], 6-[5 + (1 + ae)].

Antenna (Figs 4B View Figure 4 , 9D, E View Figure 9 ) biramous. Coxa short, without ornamentation. Basis with transverse row of long spinules at ½ length of medial margin and set of long setules on distal medial corner. Exp three-segmented. Exp-1 bare, Exp-2 ca 0.5 × as long as Exp-1, with seta subapically. Exp-3 elongate, as long as Endp-2, ca ⅗ of length of Exp, with two apical setae; shorter one as long as segment bearing it, longer one ca 2.2 × as long as shorter one and ca 2 × as long as segment bearing it. Row of long setules subapically. Endp two-segmented. Endp-1 bare. Endp-2 with short seta accompanied by two groups of strong spinules on proximal lateral corner. Two strong spiniform setae at ½ length of Endp-2, and six spiniform apical setae, one very short. All spiniform setae on Endp-2 robust, with spinules along margins.

Labrum (Fig. 2D View Figure 2 ) large, rhomboidal in ventral view, strongly bulging, without beak on posterior margin.

Mandible (Figs 4C, D View Figure 4 , 9E View Figure 9 ) comprising sclerotized coxal gnathobase and mandibular palp. Coxal gnathobase with two spines at ventral base. One spine at dorsal site of tridentate pars incisiva; lacinia unidentate. Mandibular palp comprising basis, one-segmented Exp and one-segmented Endp. Basis large, armed with three setae on distal medial corner. Exp small, armed with lateral and apical seta; lateral seta plumose. Endp armed with four setae laterally. Three setae apically, and one robust, plumose seta subapically.

Maxillule (Figs 5A, B View Figure 5 , 9E, F View Figure 9 ) with large praecoxa. Praecoxal arthrite mobile, bearing slender seta at base plus three spines apically and one spine subapically. Anterior apical and subapical spines on praecoxal arthrite with row of curved long spinules, two other spines armed with few setules. Coxa small, one-segmented, bare. Basis and Endp completely fused, with two endites and endopodal lobe. Proximal endite with three subequal setae; distal endite with two setae. Endopodal lobe with two lateral and four apical setae, each seta fused with neighbouring one at its base. Exp free, one-segmented, with two plumose setae.

Maxilla (Figs 5C View Figure 5 , 9F View Figure 9 ) non-prehensile, with slight angle between syncoxa and allobasis. Syncoxa with rows of spinules laterally and three endites along medial margin. Proximal endite at ⅓ of syncoxa length, with three setae apically; one robust and pinnate, other two smooth. Middle endite situated at ½ length of syncoxa, with one robust, pinnate seta and one smooth, slender seta apically. Distal endite triangular, mobile, with three elements; one plumose, one smooth, and one curved and pinnate. Medial margin of allobasis with one bare and one pinnate seta, at ½ length of segment. Distal endite small, with long smooth seta apically. Endp short, inconspicuous, with four bare setae, unequal in length and two robust, uni-pinnate setae.

Maxilliped (Fig. 5D View Figure 5 ) three-segmented, comprising syncoxa, basis, and one-segmented Endp. Syncoxa with one long, robust, uni-pinnate seta at distal medial corner. Basis long, with two rows of long spinules anteriorly and one row of long setules on outer margin. Endp with seta at ⅓ of segment length, with bipinnate seta subapically. Two setae apically fused at base, longer one ca 4 × as long as shorter one.

P1-P4 with three-segmented Exp and Endp. Endp always longer than Exp. Segments with rows of strong spinules on outer margins and without ornamentations on inner margins. Armature formula as follows (legend: inner-outer element; inner-apical-outer; Arabic numerals representing setae; Roman numerals representing spines):

Legs	Basis	Exopod			Endopod
Legs	Basis	1	2	3	1	2	3
P1	I-1	0-I	1-I	1-II-II	1-0	1-0	2-II-I
P2	0-1	1-I	1-I	2-II-II	1-0	1-0	2-II-I
P3	0-1	1-I	1-I	2-II-II	1-0	1-0	2-II-I
P4	0-1	1-I	1-I	2-II-II	1-0	1-0	2-II-I

P1 (Fig. 5E View Figure 5 ). Coxa rectangular, with continuous row of spinules at distal lateral corner on anterior surface. Intercoxal sclerite narrow, elongate, free margin with obtuse lobes, without surface ornamentation. Basis with row of spinules at base of insertion of inner spine. Row of three or four spinules on distal lateral corner, near insertion of outer seta. Exp reaching just midlength of Endp-3. Endp-1 with additional row of spinules on anterior surface.

P2-P4 (Fig. 6A-C View Figure 6 ) with coxa and intercoxal sclerite similar to those of P1. Basis with short row of spinules on inner margin and row of strong spinules on distal lateral corner. Exp and Endp as in P1.

P5 (Figs 7A View Figure 7 , 9G View Figure 9 ). Baseoendopodal lobe well developed, slightly shorter than Exp. Left and right leg distinctly separated. Endopodal lobe with two pinnate, spiniform spines; outer one short, inner one ca 6 × as long as outer one. Smooth, slender seta on outer margin of basis, with cuticular pore near insertion of seta. Anterior surface of baseoendopod with arched row of spinules. Exp partly fused with baseoendopod, without surface seta and with three robust pinnate spines; outermost one longest, as long as inner spine on endopodal lobe. Inner two spines as long as Exp, subequal in length.

P6 (Fig. 3B View Figure 3 ) reduced to minute prominence, forming simple plate near anterior margin of genital double-somite. With one short seta on peduncle on each side of plate.

Description of male.

Body slightly smaller than in female, fusiform. Total body length, excluding caudal setae, 427-431 µm (mean = 429; N = 3). Preserved specimens colourless. Prosome ca 1.5 × as long as urosome (Fig. 7B View Figure 7 ). Cephalothorax longer than wide, ca 0.5 × as long as length of prosome. Rostrum and surface ornamentation of prosome as in female.

Urosome (Figs 7B View Figure 7 , 8A View Figure 8 ) five-segmented, comprising fifth pedigerous somite, genital somite and four free abdominal somites. All somites with finely spinulated hyaline frill on posterior margin, except anal somite. Fifth pedigerous somite as in female. Genital somite with continuous row of minute spinules dorsally and row of strong spinules ventrally. Cuticular pore near anterior margin mid-dorsally and pair of sensilla near posterior margin. Genital field with copulatory pore mid-ventrally. First to third abdominal somites each with row of minute spinules dorsally, continuing into row of strong spinules ventrally. Sixth thoracic somite with finely spinulated hyaline frill on posterior margin. Ornamentation of first abdominal to anal somites as in female.

Antennule (Fig. 8B View Figure 8 ) geniculate, six-segmented, with geniculated articulation between fourth and fifth segment. Third segment with apical aesthetasc on peduncle. Armature formula 1-[1], 2-[8], 3-[7 + (1 + ae)], 4-[2], 5-[0], 6-[7 + (1 + ae)]. Aesthetasc on third segment robust, reaching well beyond tip of antennule.

Rostrum, antenna, mouthparts and P1-P4 (not figured) as in female.

P5 (Fig. 8A View Figure 8 ). with simple plate fused to somite bearing it. Left and right leg separated by cleft. Exp completely fused to baseoendopod. Smooth soft seta on outer margin of basis. Endopodal lobe with two pinnate spiniform setae apically. Inner one slightly longer than outer one. Exopodal lobe with three pinnate spiniform setae. Outermost one longest, ca 2 × as long as median one, and ca 3 × as long as innermost one.

P6 (Fig. 8A View Figure 8 ) reduced to simple, rectangular plate, without armature and ornamentation. Posterior margin serrated. Left leg distinct, but right leg fused to somite bearing it.

Variability.

No variability was observed in the female. In one male, on the right P3Endp were two segments only. The terminal segment short, armed with one lateral spine and two apical setae, unequal in length (Fig. 8C View Figure 8 ). In all specimens of the male, left and right P6 are asymmetrical. The left P6 is articulated, but the right P6 is completely fused to genital somite.

Etymology.

The species name is a feminine noun in the genitive singular case, named after Dr Koraon Wongkamhaeng (Kasetsart University) in honour of her contribution to the research into the diversity of cave-dwelling copepods in Satun and Songkhla provinces.

Distribution.

The species is known only from the type locality.

Ecology.

As previously mentioned in the descriptions of Boholina laorsriae ( Boonyanusith et al. 2020), the new species was collected from a temporary pool, where there is a small opening on the cave wall (Fig. 1C View Figure 1 ). The water temperature was 24.6 °C, pH 8.93, electrical conductivity 450 µS cm-1, dissolved oxygen 5.7 mg L-1, and salinity 0.2 ppt. The new species was accompanied by other species, including Thermocyclops crassus (Fischer, 1953), Boholina laorsriae , Metacyclops sp., Mesocyclops sp., and Schizopera sp.