Dolerocypris sisaketensis, Savatenalinton, Sukonthip & Suttajit, Maitree, 2016

Savatenalinton, Sukonthip & Suttajit, Maitree, 2016, A checklist of Recent non-marine ostracods (Crustacea: Ostracoda) from Thailand, including descriptions of two new species, Zootaxa 4067 (1), pp. 1-34 : 13-18

Dolerocypris sisaketensis n. sp.

( Figures 2–4 )

Holotype. Female, soft parts dissected in glycerine on a sealed glass slide, valves stored dry in a micropalaeontological slide (MSU-ZOC.128).

Paratypes. Two dissected females (MSU-ZOC.129–130) stored like the holotype, one whole female carapace (MSU-ZOC.131) stored dry in a micropalaeontological slide.

Repository. The holotype and all paratypes are deposited in the Natural History Museum, MSU (Mahasarakham, Thailand).

Type locality. Rice field, Kantharaluk district, Sisaket Province, collected on 5 October 2010, coordinates: 14° 43΄ 46˝ N and 104° 33΄ 56˝ E. Accompanying fauna: Bradleytriebella lineata (Victor & Fernando, 1981) , Bradleytriebella tuberculata ( Hartmann, 1964) , Chrissia formosa ( Klie, 1938) , Cypris subglobosa Sowerby, 1840 , Dolerocypris sinensis Sars, 1903 , Hemicypris exiqua Broodbakker, 1983 , Hemicypris mizunoi Okubo, 1990 , Ilyocypris sp., Limnocythere stationis Vávra, 1891 , Physocypria sp.2, Pseudocypretta maculata Klie, 1932 , Pseudostrandesia calapanensis ( Tressler, 1937) , Stenocypris cf. orientalis, Strandesia sexpunctata Klie, 1932 , and Strandesia kraepelini ( Müller, 1906) .

Other locality. Huai Pao (stream), Kaset Sombun district, Chaiyaphum Province, collected on 9 October 2007, coordinates: 16° 23΄ 3˝ N and 101° 58΄ 47˝ E. Accompanying fauna: Cypretta sp., Cypridopsis sp., Cypris subglobosa Sowerby, 1840 , Physocypria sp.1, Physocypria sp.2, Pseudostrandesia mamarilorum (Victor & Fernando, 1981) , Strandesia kraepelini ( Müller, 1906) , and Strandesia sexpunctata Klie, 1932 .

Etymology. The species is named after Sisaket Province, where it was discovered.

Diagnosis. Carapace in lateral view elongated, anterior margin rounded, posterior margin narrower rounded, LV with large marginal zone anteriorly, ventrally, and posteriorly, RV with large marginal zone anteriorly, and posteriorly and with spine-like projection at postero-ventral corner, calcified inner lamella of both valves wide and reticulated anteriorly and posteriorly, A2 with short natatory seta c. half of penultimate segment, longest reaching tip of terminal claws, terminal segment of Mx1 short (width and length subequal), two large bristles on third endite smooth, T1 with a, b and d setae, T2 with subequal, short d1 and d2 setae, CR claws long, large, set with strong denticles, length of Ga c. half of that of ramus, length of Gp c. 2/3 that of Ga, Sa shorter than Gp, Sp short (reaching slightly beyond tip of ramus).

Differential diagnosis. Dolerocypris sisaketensis n. sp. is characterized by the presence of a spine-like postero-ventral projection on the RV. It cannot be confused with any other species in the genus Dolerocypris .

Measurements (mean, in µm). LV (n = 2), L = 1530, H = 510; RV (n = 2), L = 1608, H = 490; Carapace (n = 2), L = 1400, W = 364.

Ecology. The new species has thus far been recorded from only two localities: a rice field, and a stream. It occurred at a pH range of 7.20 – 7.81, a temperature range of 25.6 – 29.6 °C and a DO range of 3.27 – 5.91 mg/l.

Description of female. Carapace in lateral view ( Fig. 2 G) elongated, anterior margin rounded, posterior margin narrower rounded with spine-like projection at postero-ventral corner of RV, RV overlapping LV anteriorly and posteriorly, dorsal margin arched, greatest high situated at mid-length, valve surface smooth.

Carapace in dorsal view ( Fig. 2 H) elliptical, with greatest width situated at mid-length.

LV in interior view ( Fig. 2 B) with large marginal zone anteriorly, ventrally, posteriorly, calcified inner lamella, wide and reticulated anteriorly and posteriorly, inner list and groove well developed along valve margin.

RV in interior view ( Fig. 2 A) with large displaced selvage at anterior end, calcified inner lamella, wide and reticulated anteriorly and posteriorly, marginal zone at postero-ventral corner wide with spine-like projection.

A1 ( Fig. 3 A): first segment with small proximal Wouters organ, one long dorso-subapical seta (reaching beyond tip of the segment) and two long ventro-apical setae. Second segment slightly wider than long, with one long dorso-apical seta (reaching mid-length of the next segment) and short Rome organ. Third segment bearing two setae: one long dorso-apical one, reaching beyond tip of terminal segment, and one short ventro-apical setae. Fourth segment with two long dorsal setae and two subequal ventral setae (short one reaching beyond tip of fifth segment, long one reaching beyond tip of terminal segment). Fifth segment dorsally with two long setae, ventrally with two (one long, one short) setae, short one reaching tip of penultimate segment. Penultimate segment with four long apical setae. Terminal segment with three (two long, one short) apical setae and aesthetasc y a, the latter c. twice as long as short apical seta.

A2 ( Fig. 3 B–C): exopodite with three (one long, two short) setae, length of the long one c. 3/4 of of first endopodal segment. First endopodal segment with five long (reaching tip of terminal claws) and one short natatory setae, length of the shortest seta c. half of penultimate segment, aesthetasc Y long, ventro-apical seta long, reaching tip of penultimate segment. Penultimate segment undivided, distally with three serrated claws, aesthetasc y2 long (reaching tip of terminal segment), z1–z3 setae long; this segment medially with two (one long, one shorter) dorsal setae (length of the short one c. 2/3 of that of the long one) and four ventral setae of unequal length (t1–t4). Terminal segment with two serrated claws (GM and Gm), g-seta and aesthetasc y3, length of Gm c. 5/6 of that of GM, length of aesthetasc y3 more than half way of that of accompanying seta, g-seta of similar length as Gm. Md-palp ( Fig. 3 D): first segment with two large setae (s1 and s2), one slender, long seta and long, smooth α-seta. Second segment dorsally with three unequal long apical setae, length of shortest c. half of that of longest; ventrally with group of three long hirsute setae, one shorter hirsute seta and β-seta, the latter plumose, cone-shaped and with pointed tip. Penultimate segment consisting of three groups of setae: dorsally with group of four unequal, long, subapical setae; laterally with apical γ-seta and three further smooth apical setae, the former stout, hirsute, long (length c. 1.3 times of that of terminal segment); ventrally with two (one long, one short) subapical setae, short one not reaching tip of segment. Terminal segment ( Fig. 3 E) bearing three claws and three setae.

Mx1 ( Fig. 4 A) with two-segmented palp, three endites and large branchial plate; basal segment of palp with group of four long, unequal apical setae and two (one long, one shorter, subapical setae, the latter not reaching tip of terminal segment), terminal segment short (width and length subequal), apically with three claws and three setae. Two large bristles on third endite smooth. Sideways-directed bristles on first endite unequally long.

T1 ( Fig. 4 B–C): protopodite with two a-setae (length of short one c. half of that of long one), long b and dsetae, distally with 14 (10 apical, four subapical) hirsute setae of unequal length. Endopodite weakly built palp with three unequal apical setae.

T2 ( Fig. 4 D) with subequal, short d1 and d2 setae.Second segment with short e-seta (reaching half of proximal segment of penultimate segment). Penultimate segment divided, proximal segment (a) bearing long f-seta (reaching less than tip of terminal segment), distal segment (b) with pair of apical setae (long g-seta, one spinelike). Terminal segment with two (one dorsally, one ventrally) apical h1 and h3 setae (the latter spine-like) and serrated claw (h2).

T3 ( Fig. 4 E) cleaning limb. First segment with long d1, d2, dp setae. Second segment with long apical e-seta (reaching half of next segment).Third segment with medially short f-seta (not reaching tip of segment). Terminal segment with apical pincer and three setae, one short h1 seta, one claw-like h2 seta and one reflexed subapical h3 seta, length of the latter equal of that of third segment.

CR ( Fig. 4 F) well-developed, robust, with ventral margin serrated, Ga and Gp long, large, set with strong denticles, length of Ga c. half of that of ramus, length of Gp c. 2/3 that of Ga. Sa long (shorter than Gp), Sp short (reaching slightly beyond tip of ramus).

CR attachment ( Fig. 4 G) stout, with two distal branches.

Male unknown.

Figures

FIGURE 2 Dolerocypris sisaketensis n. sp., female. A. RV, internal view (MSU-ZOC. 128); B. LV, internal view (ditto); C. anterior part of A; D. posterior part of A; E. posterior part of B; F. anterior part of B; G. carapace, left lateral view (MSU- ZOC. 131); H. carapace, dorsal view (ditto). Scale bar = 500 Μm for A – B; 310 Μm for C – F; 230 Μm for G – H.

FIGURE 3 Dolerocypris sisaketensis n. sp., female (MSU-ZOC. 128). A. A 1; B. A 2; C. distal part of penultimate segment and terminal segment; D. Md-palp; E. terminal segment of Md-palp; F. Md-coxa. Scale bar = 100 Μm for A – B, F; 50 Μm for C – E.

FIGURE 4 Dolerocypris sisaketensis n. sp., female (MSU-ZOC. 128). A. Mx 1; B. T 1; C. protopodite of T 1; D. T 2; E. T 3; F. caudal ramus; G. caudal ramus attachment. Scale bar = 54 Μm for A; 93 Μm for B; 50 Μm for C; 100 Μm for D – G.