Cypris songkhramensis, Savatenalinton, 2022

Savatenalinton, Sukonthip, 2022, On Cypris songkhramensis, a new species of Ostracoda (Crustacea) from Thailand, Raffles Bulletin of Zoology 70, pp. 440-450 : 441-447

Cypris songkhramensis new species

( Figs. 1–5 )

Material examined. Holotype: Female , soft parts dissected in glycerine on a sealed slide, valves stored dry on a micropalaeontological slide ( MSU-ZOC.348), Nong Chai Wan (swamp), Si Songkhram District, Nakhon Phanom Province, Thailand, 17°39.309′ N 104°10.664′ E, coll. S Savatenalinton, 16 November 2021.

Paratypes: two dissected females stored like the holotype ( MSU-ZOC.349–350) .

Measurements (μm). Female. Cp (n=1): L = 1589 (spines not included), W = 1158; LV (n=2): L = 1569 – 1611 (spines not included), H = 1011 – 1032, RV (n=2): L = 1558 – 1589, H = 968 – 989.

Diagnosis. Cp in dorsal view subglobose with beak-shaped anterior extremity, Cp in lateral view with strongly arched dorsal margin. LV with two anterior spines and one posterior large spine, one well-developed anterior inner list, ventral inner list with a short row of denticles situated just before mid-length. RV with a row of small pointed spines on external part of posteroventral margin and with inwardly displaced anterior selvage. A2 natatory setae long (not reaching tip of terminal claws). Second segment of Md-palp with a group of four setae close to β-seta, β-seta thin, long, set with scattered setules. Two large bristles on Mx1 third endite smooth. T2 with d1 seta about twice as long as d2 seta and remarkably short h3 seta. T3 with very long e-seta and short h3 seta. CR with long and slender claws Ga and Gp, claw Ga c. two thirds of ramus, length of claw Gp c. two thirds that of claw Ga, seta Sp very long (reaching two thirds length of claw Gp).

Description of female. Carapace in dorsal view subglobose, greatest width situated at mid-length, anterior extremity strongly beak-shaped, posterior extremity narrowly rounded. LV slightly overlapping RV all free margin. Valve surface with small and shallow pits and with long rimmed-pore setae ( Fig. 1E ).

LV in external view ( Fig. 1A, C ) subovate, greatest height situated just before mid-length, anterior margin widely rounded with two large spines situated on c. mid-height and lower half, posterior margin narrowly rounded with one large, straight spine situated at two thirds of height. Dorsal margin strongly arched, subtriangular, ventral margin somewhat straight.

RV in external view ( Fig. 1B, D ) same as in LV, except for anterior and posterior margins without large spines, and posteroventral margin with a row of obvious, small, pointed spines.

LV in interior view ( Figs. 1F , 2A, B ) with submarginal selvage, anterior calcified inner lamella wide with one welldeveloped inner list, ventral inner list with a short row of denticles situated just before mid-length, posterior calcified inner lamella narrow with strong inner list.

RV in interior view ( Figs. 1G , 2C, D ) with inwardly displaced anterior selvage, anterior calcified inner lamella wide with two well-developed inner lists, posterior calcified inner lamella narrow with strong inner list, gap between ventral inner list and valve margin with structure complementary to LV denticles.

A1 ( Fig. 3A ): First segment with intermediate length, dorsal seta (reaching half of next segment) and two long ventroapical setae, Wouters organ not seen. Second segment subquadrate with one long dorso-apical seta, Rome organ very small and short. Third segment bearing two setae: one long dorso-apical seta (reaching beyond tip of fifth segment), and one shorter ventro-apical seta (reaching tip of next segment). Fourth segment with two long dorsal apical setae and two ventral apical setae, one long (reaching tip of terminal segment) and one shorter (reaching slightly beyond tip of next segment). Fifth segment with two long dorsal apical setae and two ventral apical setae, one long, one shorter (shorter one reaching beyond tip of aesthetasc ya). Penultimate segment with four long apical setae. Terminal segment with three (one short, two long) apical setae and an aesthetasc ya, the latter c. 5.8 times of terminal segment, short seta less than half length of aesthetasc ya.

A2 ( Fig. 3B ): Exopodite with three (one long, two short) setae, the long one reaching tip of first endopodal segment. First endopodal segment with five long natatory setae (not reaching tip of terminal claws) and short accompanying seta (less than half length of penultimate segment), aesthetasc Y short and slender, ventro-apical seta long (reaching tip of terminal segment). Penultimate segment undivided, medially with two (one long, one shorter) dorsal setae (short one reaching beyond tip of terminal segment and its length c. two thirds of long one) and four ventral setae of unequal length (t1–t4), t4 seta shortest (reaching tip of segment); this segment distally with three claws G1–G3 (length c. 1.5 times of that of penultimate segment), aesthetasc y2 short (c. half of length of terminal segment), z1– z3 setae long (not reaching tip of terminal claws). Terminal segment with two claws (GM and Gm), aesthetasc y3 with accompanying seta, and g seta (shorter than y3), length of Gm c. three fourths of that of GM, length of aesthetasc y3 c. two thirds of accompanying seta, the latter shorter than GM (length c. five sixths of that of GM).

Md-coxa ( Fig. 3C ) elongated, distally set with rows of teeth (large dorsally and smaller ventrally) and small setae, and with one dorso-subapical seta, the latter short (not reaching base of teeth).

Md-palp ( Fig. 4A–D ): First segment with two large setae (S1 and S2), one long seta and long, slender, smooth α-seta. Second segment dorsally with three unequally long subapical setae (length of shortest seta c. half of that of long ones); ventrally with a group of four long setae ( Fig. 4C ), one shorter seta and β-seta, the latter thin, long, set with scattered setules. Penultimate segment bearing three groups of setae: dorsally with group of four unequal, long, subapical setae; laterally with apical γ-seta and three further apical setae, the former slender and long (length c. 2.4 times of terminal segment), distally covered with long setules over c. two thirds of its length, the latter subequal in length (length of the longest seta slightly beyond tip of γ-seta); ventrally with two subapical setae, one very long (length c. 2.5 times of terminal segment), one short (not reaching tip of terminal segment). Terminal segment bearing two claws and three setae, length of terminal claws c. three times that of terminal segment.

Mx1 ( Fig. 3D ) with two-segmented palp, three endites and large branchial plate with 20 plumose rays and six reflexed basal rays; basal segment of palp dorsally with a group of four long, unequal apical setae and one subapical seta (reaching tip of terminal claws), medially with one long apical seta (reaching beyond tip of terminal segment); terminal segment elongated (length 2.5 times of width), apically with three claws and three setae. Remark: In Fig. 3D , the third endite of the Mx1 was twisted because of the slide preparation. This affects the lateral seta which shifts to the opposite side. Also, the shape of two large bristles was unusual due to the distortion; it is thus not taken into account.

T1 ( Fig. 4E–G ): protopodite with two a-setae (one long, one short, with long seta c. twice as long as short seta) and long b-and d-setae (both setae long and distally covered with very long setules c. two thirds of its length), c-seta absent; distally with 10 apical setae of unequal length and four subapical setae, all these 14 setae distally covered with very long setules c. two thirds of their length ( Fig. 4G ). Endopodite elongated, weakly built palp with three (one long, two shorter) apical setae, length of long one c. 2.3 times of shortest one. Branchial plate with six plumose rays.

T2 ( Fig. 5A ): First segment with d1 and d2 setae, length of d1 seta c. 2 times that of d2 seta. Second segment with short e-seta (reaching mid-length of penultimate segment). Penultimate segment undivided, medially with long f-seta (reaching tip of terminal segment) and long apical g-seta (reaching tip of terminal segment). Terminal segment with two (one anterior, one posterior) apical h1 and h3 setae and serrated claw (h2), length of h1 seta c. one fourths of that of h2 claw, h3 seta remarkably short (slightly beyond tip of terminal segment).

T3 ( Fig. 5B ): First segment with long d1, d2 and dp setae, all subequal in length. Second segment with long apical e-seta (reaching three fourths of next segment). Third segment with medium-length f-seta (reaching beyond tip of its segment). Terminal segment with pincer organ and bearing very short h1seta, claw-like h2 seta and short h3seta (length less than half that of third segment).

CR ( Fig. 5C ) with subequal, long claws Ga and Gp, length of claw Ga c. two third of that of ramus, length of claw Gp c. two thirds of that of claw Ga, seta Sa short (length c. one fourths that of Gp), seta Sp very long (reaching two thirds length of claw Gp). CR attachment ( Fig. 5D ) long and slender, distally with two branches.

Female genital lobe ovate, undivided and without protrusion and special features.

Figures

Fig.1. Cypris songkhramensis, new species, female (MSU-ZOC.348). A. LV, external view. B. RV, external view. C. LV, dorsal view. D. RV, ventral view. E. LV, valve surface. F. LV, internal view. G. RV, internal view. H. RV, muscle scars. Scale bar: A–D, F–G = 200 μm, E = 10 μm, H = 100 μm.

Fig. 2. Cypris songkhramensis, new species, female (MSU-ZOC.348). A. LV, internal view, posterior part. B. LV, internal view, anterior part. C. RV, internal view, anterior part. D. RV, internal view, posterior part. Scale bar: A–D = 100 μm.

Fig. 3. Cypris songkhramensis, new species, female (MSU-ZOC.348). A. A1. B. A2. C. Md-coxa. D. Mx1. Scale bars: A–C = 100 μm, D = 50 μm.

Fig. 4. Cypris songkhramensis, new species, female (MSU-ZOC.348). A. Md-palp. B. Md-palp, terminal segment. C. Md-palp, a group of four setae on second segment. D. Md-palp, α, β, γ-setae. E. T1 palp. F. T1. G. T1, terminal part of protopodite. Scale bars: A–G = 50 μm.

Fig. 5. Cypris songkhramensis, new species, female (MSU-ZOC.348). A. T2. B. T3. C. CR. D. CR attachment. Scale bars: A–C = 100 μm, D = 107 μm.