Chrissia ueluenakarati, Savatenalinton, 2025

Savatenalinton, Sukonthip, 2025, Two new species of freshwater ostracods (Crustacea: Ostracoda) from the northeast of Thailand, with notes on sexually reproducing populations of Chrissia and Strandesia, Zootaxa 5717 (2), pp. 235-257 : 236-244

publication ID	https://doi.org/10.11646/zootaxa.5717.2.4
publication LSID	lsid:zoobank.org:pub:E97982BB-6164-47BA-9FF0-4974484888A6
DOI	https://doi.org/10.5281/zenodo.17890287
persistent identifier	https://treatment.plazi.org/id/B6204209-FFD8-FFC3-4499-F8F7C82D5EE9
treatment provided by	Plazi
scientific name	Chrissia ueluenakarati
status	sp. nov.

Treatment

Chrissia ueluenakarati sp. nov.

( Figs 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Etymology. The species is named after the King, Ue-Lue Nakarat, in the Naka legend of Bueng Khong Long District where the new species was discovered.

Diagnosis. Cp in lateral view elongated, length c. 1.77 mm in female (H/L = 0.40–0.42), c. 1.58 mm in male (H/L = 0.40–0.41), greatest H situated at mid-length, Cp in dorsal view elongated with narrow anterior and posterior extremities, RV overlapping LV along all free margins, anteriorly slightly larger than posteriorly, valve surface smooth with sparse rimmed-pore setae, both valves with marginal anterior selvage, rounded anterior margins, narrowly rounded posterior margins with blunt tip, and wide anterior inner lamella without inner list. A1 with small, unsegmented RO. A2 natatory setae long (reaching beyond tip of terminal claws), aesthetasc Y slender, three-segmented. Male A2 with claw-like z1 and z2 setae, strongly reduced claw G1 and with claw G3 modified to thin setae, claw Gm large with robust teeth, claw GM considerably reduced to short and thin seta. Md-palp with short α-seta, third seta of lateral apical setae on penultimate segment short, terminal segment elongated with three claws and two setae. Mx1-palp with elongated terminal segment bearing two claws and three setae, two large bristles on 3rd endite serrated. T2 with short and thin d1 and d2 setae, h2 claw with setules far from its tip. CR well-developed, asymmetrical with right CR larger (but slightly shorter) than left one, right ramus with c. eight groups of long and robust spines on ventral margin, left ramus with c. 6 groups of small spines and setules on ventral margin, claws Ga and Gp of both CR strongly serrated with two subsets of robust spines. CR attachment with basal triangular loop. Male T1 palps asymmetrical, basal segment of right and left palps subquadrate, terminal segment of both palps elongated, left one narrower than that of right one. Hp with subrectangular ms, widely rounded distal margin, medially slightly concave with marginal tiny warts, ls subquadrate with widely rounded distal margin, distal inner corner bearing tiny warts and fine setules, dls with pointed protrusion; Hp internally with large bladder-like part ‘c’ of labyrinth, postlabyrinthal spermiduct curved, with three loop. ZO elongated with c. 25 spiny whorls.

Type materials: Holotype. Female, soft parts of a dissected specimen preserved in glycerine on a slide, and valves stored dry in a micropalaeontological slide ( MSU-ZOC.426).

Allotype. Male, stored like the holotype ( MSU-ZOC.427).

Paratype. Male, stored like the holotype ( MSU-ZOC.428), whole individuals of three males and three females in 70% ethanol ( MSU-ZOC.429) .

Type locality. A marshy area next to a weir connecting Bueng Khong Long (marsh) and a rice field, Bueng Khong Long District, Bueng Kan Province, Thailand ( 17º 57.53′ N, 104 º 02.09′ E), coll. S. Savatenalinton, 18 Mar. 2024 GoogleMaps .

Measurements (in μm). Female: LV (n = 2), L = 1705–1726, H = 704–726; RV (n = 2), L = 1753–1774, H = 711–732. Male: LV (n = 2), L = 1558–1571, H = 619–641; RV (n = 2), L = 1551–1583, H = 621–643.

Description of female. Cp in lateral view elongated (length c. 1.77 mm, H/L = 0.40–0.42), greatest height situated at mid-length, Cp in dorsal/ventral views elongated, greatest width situated at mid-length, narrower anterior and posterior extremities, RV overlapping LV along all free margins, anteriorly slightly larger than posteriorly, valve surface smooth with sparse rimmed-pore thin setae.

LV in internal view ( Figs 1A, E–F View FIGURE 1 ) with rounded anterior margins, narrow posterior margin with blunt end, dorsal margin strongly arched, ventral margin slightly concave in front of mid-length, marginal selvage anteriorly, anterior calcified inner lamella wide without inner list, posterior calcified inner lamella narrow without inner list, one short ventral inner list situated at c. mid-length, marginal pore canals present.

RV in internal view ( Figs 1B, G–H View FIGURE 1 ) with rounded anterior margins, narrow posterior margin with blunt end, dorsal margin strongly arched, ventral margin concave in front of mid-length, marginal selvage anteriorly, calcified inner lamella wide anteriorly, narrow posteriorly, without anterior and posterior inner lists, antero-dorsal and postero-dorsal parts with small, shallow pit-like structure, postero-dorsal one more elongated, marginal pore canals present.

A1 ( Fig. 3A View FIGURE 3 ) seven-segmented. First segment with one long dorso-subapical seta (reaching mid-length of next segment), two long ventro-apical setae, WO not seen. Second segment c. 1.3 times wider than long, with one short dorso-apical seta (length c. 1/4 of next segment) and small, unsegmented RO. Third segment bearing two setae: one long dorso-apical (reaching beyond tip of terminal segment) and one very short ventro-apical setae (not reaching mid-length of next segment). Fourth segment with two long dorsal setae and two short ventral setae, shortest one not reaching tip of next segment and with flagellum-like tip. Fifth segment dorsally with two long setae, ventrally with two setae (one long, one shorter), shorter one reaching beyond tip of terminal segment. Penultimate segment with four long apical setae and one very short seta (reaching mid-length of terminal segment). Terminal segment elongated (c. three times longer than width) with three apical setae (two long, one short) and remarkably long aesthetasc ya (length more than two times that of short seta).

A2 ( Fig. 3B View FIGURE 3 ) protopodite with two proximal setae and one long ventro-apical seta (reaching beyond tip of first endopodal segment), third proximal seta not seen. Exopodite with three (one long, two short) setae, long one reaching tip of first endopodal segment. Endopodite three-segmented. First endopodal segment with five long natatory setae (reaching beyond tips of terminal claws) and one short accompanying seta (reaching c. 1/3 of that of penultimate segment), aesthetasc Y medium size, three-segmented, situated at c. 1/3 of its segment length, ventro-apical seta long, reaching tip of terminal segment. Penultimate segment undivided, medially with two subequally short dorsal setae, four t-setae of unequal length, longest seta reaching beyond tip of claw Gm, distally with long z1–z3 setae (z1 shorter than other z setae, z2–z3 not reaching tip of claws G1), long aesthetasc y2 (reaching slightly beyond tip of terminal segment), three large, serrated claws (G1–G3), G1 larger than other claws, G2 shorter than other claws. Terminal segment with small ventro-apical projection set with fine marginal setules (not illustrated); distally with two claws (GM and Gm), medium length g seta (longer than claw Gm) and aesthetasc y3, claw GM large, claw Gm remarkably short and thin (length c. half of that of GM), length of aesthetasc y3 half of that of accompanying seta.

Md-coxa ( Fig. 3D View FIGURE 3 ) elongated, distally set with rows of teeth (large dorsally and smaller ventrally) and small (smooth or hirsute) ventro-apical setae, and with one slightly hirsute dorso-subapical seta, the latter thin and short (not reaching base of teeth).

Md-palp ( Fig. 4A View FIGURE 4 ) four-segmented. First segment composed of two large setae (S1 and S2) with long setules, one long and slender seta with few setules at its tip, and smooth, elongated α-seta with long thin tip. Second segment dorsally with three unequal long apical setae, shortest seta reaching tip of next segment; ventrally with group of three long, hirsute setae, one shorter hirsute seta (reaching tip of next segment) and cone-shaped, plumose β-seta with pointed tip. Penultimate segment bearing three groups of setae: dorsally with group of four unequal, long, subapical setae; laterally with short apical γ-seta (reaching beyond tip of terminal segment) and three (two long, one remarkably short and thin) apical setae, length of the longest seta more than two times of terminal segment length; ventrally with two subapical setae, one long (length c. two times of terminal segment), one very short (not reaching tip of its segment). Terminal segment elongated (length c. 1.6 times of width) bearing three claws and two thin setae, length of longest claws c. 2.8 times of that of terminal segment.

Mx1 ( Figs 4B–C View FIGURE 4 ) with two-segmented palp, basal segment of palp dorsally with group of four long, unequal apical setae, one of them with long setules; laterally with one subapical seta (reaching beyond tip of its segment), terminal segment cylindrical (length c. 1.6 times of width), apically with two claws and three setae (length of setae c. 3/4 of that of claws). Third endite basally with one long seta, apically with two large bristles bearing slightly serrated distal part. First endite with two unequally long sideways-directed bristles and two basal setae.

T1 ( Figs 4D–E View FIGURE 4 ): protopodite with two short a-setae, subequal in length, long b-and d-setae with long setules, c-seta absent; distally with 10 hirsute apical setae of unequal length and four (three long and one short) subapical setae with long setules. Endopodite very elongated, weakly built palp with three (one long with setules, two short) apical setae, length of long one c. 3.5 times of shortest one.

T2 ( Fig. 5A View FIGURE 5 ) five-segmented. Basal segment with short, thin d1 and d2 setae. Second segment with long, thin, hirsute e-seta (almost reaching tip of next segment). Penultimate segment divided, medially with medium length, slightly hirsute f-seta (reaching tip of terminal segment), distally with long apical g-seta (reaching c. 1/3 of h2 claw). Terminal segment dorsally with one short apical h1 seta, ventrally with one short subapical h3 seta, h1 and h3 subequal in length, laterally with long, serrated apical h2 claw (length c. 1.6 times of that of penultimate segment), setules on h2 claw far from tip.

T3 ( Fig. 5B View FIGURE 5 ) three-segmented. First segment with long d1, d2 and dp setae, all hirsute and subequal in length. Second segment with medium-length apical e-seta (reaching mid-length of next segment). Third segment medially with short f-seta (not reaching tip of segment). Terminal segment with pincer organ and bearing very short h1seta, claw-like h2 seta and long, hirsute h3 seta.

CR ( Figs 5C–D View FIGURE 5 ) well-developed, asymmetrical with right CR larger than left one, right ramus slightly shorter than left ramus.

Right CR ( Fig. 5C View FIGURE 5 ) with c. eight groups of long and robust spines on ventral margin of ramus, spines in each group reduced in size towards posterior, claw Ga short (length c. 0.4 time of that of ramus), claw Gp short (length c. 2/3 of that of claw Ga), both claws strongly serrated with two subsets of large spines, sa seta thin and short (shorter than claw Gp), sp seta absent.

Left CR ( Fig. 5D View FIGURE 5 ) with c. 6 groups of small spines and setules on ventral margin of ramus, claw Ga short (length c. 0.4 time of that of ramus), claw Gp short (length c. 2/3 of that of claw Ga), both claws strongly serrated with two subsets of large spines, sa seta thin and short (slightly longer than claw Gp), sp seta absent.

CR attachment ( Fig. 5E View FIGURE 5 ) thin, basally with triangular loop and distally with two well-developed branches (db and vb).

Description of male. Carapace and valves as in female, but somewhat smaller (length c. 1.58 mm, H/L = 0.40–0.41) ( Figs 1C–D View FIGURE 1 , 2A–D View FIGURE 2 ). All limbs as in female, except for last two segments of A2, T1, CR and reproductive organs. Penultimate segment of A2 ( Fig. 3C View FIGURE 3 ) with claw-like z1 and z2 setae, considerably reduced claw G1 and with claw G3 reduced to thin setae; terminal segment with claw Gm large with distal pectinate shape, claw GM considerably reduced, length of GM c. half of length of Gm ( Fig. 3C View FIGURE 3 ). T1-endopodites forming asymmetrical prehensile palps; basal segment of right ( Fig. 6C View FIGURE 6 ) and left palps ( Fig. 6D View FIGURE 6 ) subquardrate with two long subapical spines; terminal segment of both palps elongated, left one narrower than that of right one. sa seta of right and left CR shorter than that of female, robust spines on ventral margin of right ramus shorter than those of female, small spines and setules on ventral margin of left ramus stronger than those of female with longest spine at subapical part. Hp ( Figs 6E–F View FIGURE 6 ) with ms subrectangular, widely rounded distal margin, medially concave with tiny warts on lateral margin, ls subquadrate with widely rounded distal margin, distal inner corner bearing tiny warts and fine setules, dls with pointed protrusion; Hp internally with large bladder-like part ‘c’ of labyrinth, postlabyrinthal spermiduct curved, with three loops. ZO ( Fig. 6G View FIGURE 6 ) elongated with c. 25 spiny whorls.