Thermocyclops oryzae Saetang, Koompoot, Watiroyram & Maiphae, 2024, sp. nov.

Thermocyclops oryzae sp. nov. Type locality. Central Thailand, Suphan Buri Province, Bang Pla Ma District, Phai Kong Din Subdistrict; 14 ° 19 ' 41.4 " N, 100 ° 15 ' 05.5 " E; rice field. Other localities. Northeastern Thailand, Bueng Kan Province, So Phisai District, Kham Kaeo Subdistrict, Ban Kham Kaeo; 18 ° 05 ' 32.0 " N, 103 ° 31 ' 52.3 " E; temporary roadside canal; 3 June 2022; leg. S. Watiroyram. Northeastern Thailand, Sakon Nakhon Province, at the boundary between Ban Muang-In Plaeng District; 17 ° 48 ' 49.0 " N, 103 ° 35 ' 19.8 " E; temporary roadside canal; 16 May 2022; leg. S. Watiroyram. Northeastern Thailand, Sakon Nakon Province, Akat Amnuai District, Samakkhi Phatthana Subdistrict, Ban Nong Sam Kha; 17 ° 19 ' 41.5 " N, 103 ° 52 ' 38.2 " E; temporary roadside canal; 16 June 2022; leg. S. Watiroyram. Northeastern Thailand, Udon Thani Province, Nam Som District, Ban Yuak Subdistrict, Ban Champa Thong; 17 ° 43 ' 37.8 " N, 102 ° 11 ' 20.4 " E; temporary roadside canal; 19 June 2022; leg. S. Watiroyram. Northeastern Thailand, Udon Thani Province, Kumphawapi District, Nong Wa Subdistrict, Ban Nong Wa; 17 ° 01 ' 33.9 " N, 102 ° 58 ' 55.8 " E; temporary roadside canal; 18 June 2022; leg. S. Watiroyram. Northeastern Thailand, Ubon Ratchathani Province, Samrong District, Bon Subdistrict, Ban Kho Bon; 15 ° 04 ' 47.2 " N, 104 ° 48 ' 00.9 " E; temporary roadside canal; 3 May 2022; leg. S. Watiroyram. northeast Thailand, Ubon Ratchathani Province, Pho Sai District, Lao Ngam Subdistrict, Ban Pong Pao; 15 ° 45 ' 54.7 " N, 105 ° 23 ' 33.0 " E; temporary pond; 5 May 2022; leg. S. Watiroyram. Material examined. Holotype. • One adult female, dissected and mounted onto two slides, central Thailand, Suphan Buri Province, Bang Pla Ma District, Phai Kong Din Subdistrict, 27 March 2023, leg. T. Saetang and S. Maiphae; PSUZC-PK 2010-01 and PSUZC-PK 2010-02. Allotype. • One adult male, dissected and mounted onto two slides, collected from the same locality as the holotype: PSUZC-PK 2010-03 and PSUZC-PK 2010-04. Paratype. • One adult female, dissected and mounted onto two slides, collected from the same locality as the holotype: PSUZC-PK 2010-05 and PSUZC-PK 2010-6. Other specimens examined. Ten adult females, collected from those other seven localities and deposited in the collection of the second author (KK); two adult males, collected from the type locality and deposited in the collection of the fourth author (SM). Differential diagnosis. Thermocyclops oryzae sp. nov. differs from congeneric species in the following characters: female, (i) caudal ramus elongate, about 3.5–4.1 times as long as wide, (ii) innermost terminal seta (VI) 1.1–1.3 times as long as outermost terminal seta (III), (iii) second endopodal segment of antenna with 8 setae, (iv) round projections on the distal margin of intercoxal sclerite of P 1 – P 4 with spinules, (v) intercoxal sclerite of P 1 – P 3 ornamented with one intermittent row of spinules on posterior surface, (vi) intercoxal sclerite of P 4 ornamented with spinules arranged in two arcs on the anterior surface, and two transverse rows of spinules on the posterior surface, (vii) medial margin of basis of P 4 with serrate lobe, (viii) inner apical spine of third endopodal segment of P 4 length about 0.9 times as long as outer spine, (ix) exopodal and endopodal segments of P 1 – P 4 with tiny spinules on posterior surface. Description of the adult female. Body (Fig. 1 A). Total body length measured from anterior margin of rostrum to posterior margin of caudal rami, ranging from 768–990 µm (mean 894 µm, n = 3; 990 µm in holotype). Prosome (Figs 1 A, B, 2 A, B, 3 C) composed of cephalothorax and three free prosomites (second to fourth pedigerous somites). Surface of prosome pitted. Cephalothorax and second pedigerous somites smooth along posterior margin (Figs 2 A, B, 3 C); third and fourth pedigerous somites coarsely serrated along posterior margin (Figs 1 B, 2 B arrow). Urosome (Figs 1 C – E, 2 C, D, 3 D, E, G, 10 A) composed of fifth pedigerous somite, genital double-somite, two free urosomites, and anal somite with caudal rami. Fifth pedigerous somite ornamented with two dorsal sensilla and with dense pattern of tiny spinules on dorsal and lateral surface. Genital double-somite about as long as wide, with two dorsal sensilla; dorsal and ventral surfaces with irregular but mostly transverse short striae; coarsely serrated hyaline frill along posterior margin. Lateral arms of seminal receptacle slightly curved posteriorly. Two free urosomites with irregular but mostly transverse short striae dorsally and ventrally and with coarsely serrated hyaline frill along posterior margin. Anal somite with two dorsal sensilla at base of anal operculum; with spinules present along posterior margin on ventral surface; dorsal surface ornamented with tiny spinules; ventral surface unornamented. Caudal rami (Figs 1 C – E, 2 D, 3 F). cylindrical, parallel, about 3.5–4.1 times as long as wide (mean 3.8, n = 13; 4.1 in holotype); inner margin without hairs; dorsal and ventral surfaces with dense pattern of tiny spinules. Each ramus with six setae: innermost terminal seta (VI) 1.1–1.3 times as long as outermost terminal seta (III). Labrum (Figs 4 A, 6 C) trapezoidal, with nine teeth between two blunt lateral corners, posterior surface ornamented with two rows of long hairs. A 1 (Figs 3 A, 4 B, C) 17 - segmented. Armature formula (number of segment- [number of setae + aesthetasc (ae) + spine (s)]) of each segment as follows: 1 - [8], 2 - [4], 3 - [2], 4 - [6], 5 - [4], 6 - [1 + s], 7 - [2], 8 - [1], 9 - [1], 10 - [0], 11 - [1], 12 - [1 + ae], 13 - [0], 14 - [1], 15 - [2], 16 - [2 + ae], 17 - [7 + ae]. Last two antennular segments bearing hyaline membrane on ventral surface (Fig. 3 A). A 2 (Figs 3 B, 4 D, E, 6 A, B) composed of coxa, basis, and three-segmented endopod. Coxa rectangular, unarmed and unornamented. Basis cylindrical, with one outer bipinnate seta and two inner smooth setae along distal corner; anterior surface (Fig. 4 D) ornamented with one oblique row of inner spinules along proximal part, one longitudinal row of inner spinules along middle part; posterior surface (Fig. 4 E) ornamented with one oblique row of outer and inner spinules along proximal part, one longitudinal row of outer spinules in middle part, field of tiny spinules near base of inner setae, and one longitudinal row of tiny spinules along inner margin. ENP 1 with one inner smooth seta. ENP 2 with 7–8 inner smooth setae. ENP 3 with seven apical setae. Posterior surface of each endopodal segment ornamented with one longitudinal row of outer spinules. Mandible (Fig. 5 A, B, F) composed of coxa and palp. Coxal gnathobase with eleven chitinized teeth and two pinnate setae; anterior surface ornamented with one row of three spinules. Palp reduced, with one short smooth seta and two plumose setae. Maxillule (Figs 5 C, 6 D, F) composed of praecoxa and two-segmented palp, representing one-segmented coxobasis and one-segmented endopod. Praecoxal arthrite with three smooth and one pinnate apical spine. Praecoxa with seven inner elements; one short naked proximalmost seta, one sub-proximal plumose seta, three middle smooth setae, two distal smooth setae; group of tiny spinules present at base of short naked proximalmost seta. Coxobasis with one spiniform and two smooth setae apically; anterior surface ornamented with tiny spinules. Exopod reduced into one smooth seta near proximal part of coxobasis. Endopod with three apical smooth setae. Maxilla (Figs 5 D, 6 E) composed of praecoxa, coxa, basis, and two-segmented endopod. Praecoxal endite with two apical pinnate setae. Coxa with two endites; proximal endite with one apical plumose seta; distal endite with two apical pinnate setae. Basis with claw-like endite and one pinnate seta. ENP 1 with two pinnate setae. ENP 2 with one pinnate and two smooth setae. Maxilliped (Fig. 5 E) composed of syncoxa, basis, and two-segmented endopod. Syncoxa cylindrical, with three inner pinnate setae; anterior surface ornamented with one group of spinules in middle part of segment. Basis with two inner pinnate setae; long spinules present on medial margin and anterior surface; posterior surface ornamented with two rows of outer spinules. ENP 1 with one inner pinnate seta; anterior surface ornamented with one row of inner spinules. ENP 2 with one inner pinnate and two inner smooth setae. P 1 – P 4 (Figs 2 E, 7 A – D, 8 A – D, 9 A – G) composed of intercoxal sclerite, coxa, basis, three-segmented exopod, and three-segmented endopod. Armature formula of P 1 – P 4 as in Table 1. P 1 (Figs 7 A, B, 9 A, 10 B, D). Intercoxal sclerite subquadrate; distal margin with round projection bearing 6-7 spinules; anterior surface unornamented; posterior surface ornamented with one intermittent row of spinules. Coxa with one inner plumose seta; anterior surface ornamented with one longitudinal row of hair-like spinules laterally and three rows of tiny spinules along distal margin; posterior surface ornamented with one oblique row of hair-like spinules near the lateral margin. Basis with one outer plumose seta and one inner pinnate spine, distal tip of inner spine reaching middle of ENP 2; anterior surface ornamented with two rows of tiny spinules between bases of exopod and endopod, one row of spinules at base of endopod, one row of spinules at base of inner spine, one row of inner tiny spinules along proximal margin of segment, and long setules on median margin of basis. EXP 1 with one pinnate outer spine and one inner plumose seta; anterior surface ornamented with one longitudinal row of outer spinules and one longitudinal row of inner setules; one row of tiny spinules at base of outer spine; and one row of spinules along distal margin of segment; posterior surface ornamented with dense pattern of tiny spinules. EXP 2 with one pinnate outer spine and one inner plumose seta; anterior surface ornamented as in EXP 1. EXP 3 with two pinna