Mixtadopsis namiotkoi, Savatenalinton, 2025

Mixtadopsis namiotkoi , new species

( Figs. 1–6 View Fig View Fig View Fig View Fig View Fig View Fig )

Holotype. THAILAND, Huai Bang Bat Reservoir , Bueng Kan Province ( 18.2769°N, 103.8812°E), 19 March 2024, coll. S. Savatenalinton, female ( MSU-ZOC.417) GoogleMaps

Paratypes. Same location data as for holotype, eight females ( MSU-ZOC.418 to 425) GoogleMaps

Etymology. The species is named in honour of Prof. Dr. Tadeusz Namiotko (University of Gdansk, Poland) in recognition of his prominent work on Ostracoda and also for his kind assistance during the meeting (EOM9) in Poland.

Measurements (μm). Cp (N = 3), L = 378–381, H = 238–239, W = 283–291; LV (N = 2), L = 392–393, H = 253–254; RV (N = 2), L = 380–381, H = 240–241.

Diagnosis. Cp in lateral view subtriangular, Cp in dorsal view subglobular, LV overlapping RV anteriorly and ventrally, valve surface strong ornamentation with concentric deep pits and ridges and scattering long thin setules, RV with complete marginal septa anteriorly and posteriorly and with knob-like structures ventrally, RV with well-developed anterior groove and poorly developed posterior groove, LV with incomplete marginal septa anteriorly and posteriorly and with knob-like structures ventrally, LV with well-developed posterior inner list but not doubled and with postero-ventral space appearing not concave, A1 seven-segmented, A2 natatory setae long with distal pseudosegmentation, claw G2 of A2 strongly serrated, claws G1–G3 long (length ca. 2.9 times of that of penultimate segment), aesthetasc Y four-segmented with large and striated last segment, t2 seta large and long, Md-palp with large α and β setae, the former with long flagellum-like tip, the latter plumose with needle-like tip, terminal segment with four large claws and two thin setae, Mx1-palp with cylindrical terminal segment and with subapical seta on basal segment, T1 with unequal a-setae, T2 with intermediate-length d2 seta, penultimate segment undivided, E seta present, g and h3 setae tiny, spine-like, h2 claw long and strongly curved, T3 with completely separated terminal segment, without pincer organ, F seta tiny, spine-like, reduced CR with cylindrical base and moderate length flagellum-like seta.

Description of female. Cp in lateral view subtriangular ( Fig. 1A View Fig ), anterior and posterior ends widely rounded,

dorsal margin strongly arched, maximum height at mid-length, ventral margin straight, LV slightly larger than RV, LV overlapping RV anteriorly and ventrally, valve surface strong ornamentation with concentric deep pits and ridges and long thin setules dispersedly ( Fig. 1B View Fig ).

Cp in dorsal and ventral views subglobular ( Fig. 1C, D View Fig ) with evenly curved lateral margins, maximum width situated ca. mid-length, posterior and anterior extremities rounded, ventral outer lists well-developed with tiny pores along postero-ventral and antero-ventral margins of both valves, tiny pores without accompanying setae ( Fig. 1D–F View Fig ).

LV in internal view subtriangular ( Fig. 2A, C View Fig , 6I, J View Fig ) with greatest height at mid-length, ventral margin straight. Anterior part ( Fig. 6J View Fig ) with submarginal selvage, anterior calcified inner lamella wide with one well-developed inner list and a groove. Posterior part ( Fig. 6I View Fig ) with calcified inner lamella very narrow, one well-developed (not doubled) posterior inner list. This posterior inner list oblique and straight, neither curved nor parallel to valve margin, consequently a wide space appearing between inner list and valve margin at postero-ventral part, this space flat (not concave). Marginal septa ( Fig. 2C View Fig ) not well-developed (incomplete) anteriorly and posteriorly, posterior ones with pointed tips. Ventral margin with knob-like structures.

RV in internal view triangular ( Fig. 2B, D View Fig , 6K, L View Fig ) with greatest height at mid-length, ventral margin slightly sinuate. Anterior part ( Fig. 6K View Fig ) with marginal selvage, anterior calcified inner lamella wide with well-developed groove. Posterior part ( Fig. 6L View Fig ) with calcified inner lamella narrow, poorly developed groove. Marginal septa ( Fig. 2D View Fig ) well-developed (complete) anteriorly and posteriorly. Ventral margin with knob-like structures.

A1 ( Fig. 3A View Fig ) seven-segmented, first segment with one short dorso-subapical seta (not reaching tip of next segment) and two unequally long ventro-apical setae, Wouters organ absent. Second segment c. two times wider than long, with one very short dorso-apical seta (reaching slightly beyond tip of its segment) and Rome organ. Third segment bearing two setae: one long dorso-apical (reaching tip of terminal segment) and one very short ventro-apical setae (reaching half of next segment). Fourth segment with two long dorsal setae and two short ventral setae (longer seta reaching slightly beyond tip of penultimate segment, shortest seta reaching tip of next segment). Fifth segment dorsally with two long setae, medially with one long seta, ventrally with one short seta (not reaching tip of terminal segment). Penultimate segment with four long apical setae (two dorsally, one medially and one ventrally), small seta (α) absent. Terminal segment with three (two long, one short) apical setae and remarkably long aesthetasc ya, length of aesthetasc ya ca. more than that of last six segments, length of short seta ca. ⅓ that of aesthetasc ya.

A2 ( Fig. 3B View Fig ) basal segment with two subequally long proximal setae and one long ventro-apical seta. Exopodite with three (one long, two short) setae, long seta with exceptional length (reaching tip of terminal claws), shortest seta with needle-like tip. First endopodal segment with five very long natatory setae (reaching beyond tips of terminal claws) and one shorter accompanying seta (reaching tip of penultimate segment), distal parts of long natatory setae with discontinuously thicken lateral margins appearing pseudosegmentation, aesthetasc Y four-segmented with large and striated last segment, ventro-apical seta long, extending beyond tip of terminal segment. Penultimate segment short, undivided, medially with two subequally long dorsal setae, and four ventral setae of unequal length (t1–t4), t2 seta more developed than other t setae appearing large and long; this segment distally with three large, long, serrated claws (G1–G3) (length of G1–G3 ca. 2.9 times of that of penultimate segment), G2 with strong serration apically (serration appearing ca. half of its length), aesthetasc y2 not seen, z1–z3 setae long (almost reaching tip of terminal claws), z1 clearly larger than other z setae. Terminal segment with two serrated claws GM and Gm (length of Gm ca. ⅔ of that of GM), short g seta (almost reaching tip of aesthetasc y3) and aesthetasc y3, length of the latter ca. half of that of Gm and shorter than accompanying seta (ca. ⅔ of accompanying seta).

Md-palp ( Fig. 4A–B View Fig ) first segment with two large setae (S1 and S2), one long and slender seta, and large, smooth α seta with long flagellum-like tip. Second segment dorsally with three unequally long apical setae, shortest seta almost reaching tip of next segment; ventrally with a group of three long hirsute setae, one shorter hirsute seta and large, plumose, cone-shaped β seta with needle-like tip. Penultimate segment dorsally with a group of four unequal, long, subapical setae; laterally with slightly plumose apical γ seta (length ca. three times of terminal segment) and three long apical setae; ventrally with two subapical setae, one long (length ca. three times of terminal segment), one very short (reaching mid-length of terminal segment). Terminal segment short (subquadrate shape) bearing four large claws and two shorter, thin setae, length of largest claw ca. 4.5 times that of terminal segment.

Md-coxa ( Fig. 4C View Fig ) elongated, distally with rows of teeth and small setae, largest tooth on dorsal side and other teeth gently decreasing in size toward ventral side, and with slender subapical dorsal seta.

Mx1 ( Fig. 4D–E View Fig ) with two-segmented palp, terminal segment elongated (length ca. two times its width), distally with three claws and two setae, basal segment of palp dorsally with a group of five unequally long apical setae and one long subapical seta; laterally with one short subapical seta (not reaching tip of its segment). Two large bristles on third endite smooth with pointed-tip (without spatula-shaped apex), this endite ventrally with one long basal seta.

T1 ( Fig. 5A–B View Fig ) protopodite with two unequally long a-setae (length of short one ca. ⅔ that of long one), b, c, and d setae absent, distally with 8–9 hirsute apical setae of unequal length, subapical setae absent. Endopodite weakly built palp with one very long, hirsute seta and two unequally shorter apical setae.

T2 ( Fig. 5C View Fig ) with long and very thin d2 seta, d1 absent. Second segment distally with long e seta (almost reaching tip of next segment) and accompanying E seta, length of the latter ca. ¾ of that of e seta. Penultimate segment undivided, medially with long f seta (reaching beyond tip of terminal segment), distally with tiny, spine-like apical g seta. Terminal segment apically with one dorsal seta (h1) and serrated claw (h2), subapically with one tiny, spine-like ventral seta (h3). Claw h2 very long (length ca. that of last three segments) and strongly curved.

T3 ( Fig. 5D–E View Fig ) first segment with three setae (d1, d2, dp), d1 shortest seta (ca. half-length of dp), d2 and dp setae longer (not reaching tip of next segment). Second segment with short apical e-seta (reaching ca. ⅓ of next segment). Third segment with short f seta (not reaching tip of segment) and tiny, spine-like F seta. Terminal segment completely separated from previous segment, bearing short seta (h1), long claw-like seta (h2) and one reflexed subapical seta (h3), length of h1 less than half length of h2, length of h2 ca. ¼ of third segment, h3 slightly shorter than h2, pincer organ absent.

CR ( Fig. 5F View Fig ) reduced with cylindrical base and moderate length flagellum-like seta and medially with very short seta, length of ramus ca. ⅝ of that of flagellum-like seta.

Male unknown.

Remarks. Mixtadopsis namiotkoi , new species, is the second species of the tribe Cypettadopsini described from Thailand. The species Potamocypris sp. , which was reported in the Thai ostracod checklist ( Savatenalinton & Suttajit, 2016), was recently identified as Neopotamocypris indivisa (see Savatenalinton, 2024a). Hence, the genus Potamocypris sensu stricto has not yet been found in Thailand. Two species of Zonocypris , which were also mentioned in the Thai checklist, were eventually classified as other genera. Zonocypris sp. 1 has been placed as a member of Sarscypridopsis , but due to limitation in terms of the number of specimens and the quality of specimens available, its nomenclature is left open for now. The identity of Zonocypris sp. 2 was eventually clarified as being Cyprettadopsis sutura Savatenalinton, 2020 (see Savatenalinton, 2020). Zonocypris is therefore no longer known from Thailand. The new taxon brings the numbers of Cypridopsinae species and genera in Thailand to 13 and nine, respectively. A key to the genera of the Thai Cypridopsinae is here provided.