Pseudostrandesia ratchaburiensis, Savatenalinton, 2021

Savatenalinton, Sukonthip, 2021, Two new species of Cypricercinae McKenzie, 1971 (Crustacea: Ostracoda) from Thailand, European Journal of Taxonomy 733, pp. 19-41 : 21-28

Pseudostrandesia ratchaburiensis sp. nov.

urn:lsid:zoobank.org:act:DB1E6F7C-8DB2-4093-9CF1-E081614BE8F6

Figs 1–6

Diagnosis

Cp in lateral view elongated (length ca 2.2 times of height) with greatest height situated at one third of length, LV overlapping RV along all free margins, LV with flange on antero-ventral part and one anterior inner list, A1 seven-segmented, A2 with long natatory setae, undivided penultimate segment (in both females and males), Md-palp with long α seta and markedly large β seta, two bristles on third endite of Mx1 serrated, T1 without d-seta, T2 with d1 seta longer (ca two times) than d2 seta, f-seta long (reaching far beyond tip of terminal segment), g-, h1 and h3 setae long (length ca ⅓ of that of h2 claw), T3 with pincer organ, e- and f-setae long, CR slender, length of Ga ca half that of ramus, sa slightly longer than Gp, sp thin and long (reaching tip of ramus), CR attachment stout, with Triebel’s loop, situated at middle of distal part of main branch, db and vb well-developed, right palp of male T1 anteriorly with triangular lobe and two small apical triangular protrusions, hemipenis with medial shield broadly rounded, lateral shield elongated with blunt distal end, postlabyrinthal spermiduct curved, with 2 loops, Zenker’s organ set with 13 spiny whorls, length ca 3.5 times the width.

Differential diagnosis

Pseudostrandesia ratchaburiensis sp. nov. is similar to P. complexa ( Victor & Fernando, 1981) and P. phetchabunensis Savatenalinton & Martens, 2010 . It differs from P. complexa by the more elongated Cp in the lateral view, the large β–seta on the Md-palp, the long g and h3 setae on the T2 and the morphology of the CR. It is obviously distinguishable from P. phetchabunensis by the presence of the antero-ventral flange of the LV.

Etymology

The species is named after Ratchaburi Province, where specimens of the new species were discovered.

Type material

Holotype THAILAND – Ratchaburi Province • ♀ (soft parts dissected in glycerine on a sealed glass slide and valves stored dry in a micropalaeontological slide); Huai Mahat Reservoir, Ban Kha District ; 13º27.212′ N, 99º27.721′ E; 20 Oct. 2018; MSU-ZOC.291 .

Allotype THAILAND – Ratchaburi Province • ♂ (stored as the holotype); same collection data as for holotype; MSU-ZOC.298 .

Paratypes THAILAND – Ratchaburi Province • 3 ♀♀ (stored as the holotype); same collection data as for holotype; MSU-ZOC.292 to 294 • 3 ♀♀ (carapaces stored dry in micropalaeontological slides); same collection data as for holotype; MSU-ZOC.295 to 297 • 61 ♀♀, 62 ♂♂ (in 70% ethanol); same collection data as for holotype; MSU-ZOC.302 • 3 ♂♂ (carapaces stored dry in micropalaeontological slides); same collection data as for holotype; MSU-ZOC.299 to 301 .

Type locality

A total of 68 female specimens (1 holotype, 67 paratypes) and 66 male specimens (1 allotype, 65 paratypes) were collected at the type locality on 20 Oct. 2018. Accompanying ostracod fauna: Bradleycypris vittata (Sars, 1903) , Bradleytriebella decorata (Sars, 1903) , Dentocypria chantaranothaii Savatenalinton, 2017 , Dentocypria sp., Pseudocypretta maculata Klie, 1932 , Pseudostrandesia mamarilorum ( Victor & Fernando, 1981) , Strandesia hornei Savatenalinton & Martens, 2010 , Strandesia kraepelini (Müller, 1906) .

Repository

The holotype, allotype and all paratypes are deposited in the MSU-ZOC.

Measurements (in μm)

♀: Cp (n = 3), L = 679–745, H = 318–321, W = 329–336; LV (n = 3), L = 729–745, H = 336–343; RV (n = 3), L = 721–737, H = 336–343.

♂: Cp (n = 3), L = 650–691, H = 307–309, W = 293–295; LV (n = 2), L = 686–691, H = 307–309; RV (n = 2), L = 650–655, H = 304–306.

Description

Female

CP IN LATERAL VIEW ( Fig. 1A ). Elongated (length ca 2.2 times of height), greatest height situated at one third of length, anterior margin rounded with flange on antero-ventral part of LV, posterior margin more narrowly rounded, LV overlapping RV, especially antero-ventrally, valve surface set with short rim-pore setae.

CP IN DORSAL VIEW ( Fig. 1B ). Subelliptical, with greatest width situated slightly behind mid-length, LV overlapping RV anteriorly and posteriorly, anterior and posterior extremities narrowly rounded.

LV IN INTERNAL VIEW ( Fig. 1C , E–F). With groove along ventral margin, dorsal margin gently arched, greatest height situated at one third of length, sloping down to anterior and posterior margin, the former more widely rounded than the latter one, antero-ventral part with flange, ventral margin slightly sinuated around mid-length, calcified inner lamella relatively wide anteriorly, with one inner list, posteriorly narrower.

RV IN INTERNAL VIEW ( Fig. 1D , G–I). With marginal selvage, calcified inner lamella without inner list, anteriorly broader than posteriorly.

A1 ( Fig. 3A ). First segment with one short, dorso-subapical seta (reaching tip of segment) and two long ventro-apical setae. Second segment slightly wider than long, with one short dorso-apical seta (slightly beyond tip of segment) and long Rome organ. Third segment bearing two setae: one long dorso-apical seta, reaching halfway penultimate segment, and one short ventro-apical seta (reaching tip of next segment). Fourth segment with two long dorsal setae and two subequal, short ventral setae (the longer one reaching slightly beyond tip of next segment). Fifth segment dorsally with two long setae, ventrally with two (one long, one shorter) setae, the shorter one reaching halfway terminal segment. Penultimate segment with four long setae. Terminal segment with three (two long, one short) apical setae and an aesthetasc y a, the latter ca 4/5 of short apical seta.

A2 ( Fig. 3 B–C). Exopodite with three (one long, two short) setae, the long one reaching beyond tip of first endopodal segment. First endopodal segment with five long (reaching beyond tip of terminal claws) and one short natatory setae, length of the shortest seta less than half way penultimate segment, aesthetasc Y long, ventro-apical seta long, reaching beyond tip of terminal segment. Penultimate segment undivided, distally with three serrated claws G1–G3, aesthetasc y2 markedly long (reaching far beyond tip of terminal segment), z1–z3 setae long; this segment medially with two (one long, one shorter) dorsal setae (length of the short one ca ⅔ of that of the long one) and four ventral setae of unequal length (t1–t4), t4 shortest seta (not reaching tip of segment). Terminal segment ( Fig. 3C ) with two serrated claws (GM and Gm), g-seta and aesthetasc y3 with accompanying seta, length of Gm ca ¾ of that of GM, length of aesthetasc y3 slightly more than half of that of accompanying seta, the latter slightly shorter than Gm, length of seta g ca 3/5 of that of Gm.

MD- PALP ( Fig. 3D ). First segment with two large setae (S1 and S2), one slender, long seta and noticeably long, smooth α-seta. Second segment dorsally with three unequal long apical setae, length of the shortest ca ¼ of that of the longest; ventrally with a group of three long hirsute setae, one shorter hirsute seta and markedly large β-seta (length ca 5/6 of that of penultimate segment), the latter plumose, cone-shaped and with pointed tip. Penultimate segment bearing three groups of setae: dorsally with a group of four unequal, long, subapical setae; laterally with apical γ-seta and three further apical setae, the former stout, hirsute, long (length ca 2 times that of terminal segment); ventrally with two (one long, one short) apical setae, the latter reaching slightly beyond mid length of terminal segment). Terminal segment bearing three claws and two setae.

MD- COXA ( Fig. 4A ). Elongated, distally set with rows of teeth (large dorsally and smaller ventrally) and small setae, and with one dorso-subapical seta situated close to palp.

MX 1 ( Fig. 4B ). With two-segmented palp, three endites and large branchial plate; basal segment of palp with a group of four long, unequal apical setae and two (one long, one shorter) subapical setae, the latter reaching beyond tip of terminal segment, terminal segment elongated (length ca twice as long as width), apically with three claws and three setae. Two large bristles on third endite serrated apically. Sidewaysdirected bristles on first endite unequally long, length of short one ca ⅔ of that of long one.

T1. Protopodite ( Fig. 4C ) with two short a-setae and long b-seta, distally with 14 (10 apical, four subapical) hirsute setae of unequal length. Endopodite ( Fig. 4D ) a weakly built palp, slender shape, with three unequal apical setae.

T2 ( Fig. 5 A–B). With seta d1 ca twice the length of seta d2. Second segment with short e-seta (reaching mid-length of penultimate segment). Penultimate segment divided, proximal segment bearing long f-seta (reaching far beyond tip of terminal segment), distal segment with long g-seta (almost the same length as h1 seta). Terminal segment with two (one dorsally, one ventrally) apical h1 and h3 setae and serrated claw (h2), length of h1 seta ca ⅓ of that of h2 claw, h3 seta slightly shorter than h1 seta.

T3 ( Fig. 5C ). A cleaning limb. First segment with long d1, d2, dp setae. Second segment with long apical e-seta (extending slightly beyond half of the next segment). Third segment with medially long f-seta (reaching beyond tip of segment). Terminal segment with an apical pincer and three setae, one short h1 seta, one claw-like h2 seta and one reflexed subapical h3 seta, length of the latter ca ⅔ of that of third segment.

CR ( Fig. 5D ). Slender, ventral margin of ramus with tiny setules, Ga and Gp long, serrated, length of Ga ca half of ramus, length of Gp ca ⅔ that of Ga. sa long (slightly longer than Gp), sp thin and long (reaching tip of ramus).

CR ATTACHMENT ( Fig. 5E ). Stout, with Triebel’s loop situated at middle of distal part of main branch, db and vb well-developed, vb with swollen end.

Male

Carapace and valves as in female, although somewhat smaller ( Fig. 2 ). All limbs as in female, except for last two segments of A2, T1 and reproductive organs ( Fig. 6 ); penultimate segment of A2 with clawlike z1 and z2 setae, considerably reduced claw G1 and with claw G3 reduced to seta ( Fig. 6A ); T1- endopodites forming asymmetrical prehensile palps; right palp ( Fig. 6B ) anteriorly with triangular lobe and two small apical triangular protrusions; left palp ( Fig. 6C ) anteriorly with elongated, curved lobe, two apical spines and few tubercles.

Hemipenis ( Fig. 6D ) with medial shield rounded, lateral shield elongated with blunt distal end. Postlabyrinthal spermiduct curved, with 2 loops. Zenker’s organ ( Fig. 6E ) set with 13 spiny whorls, length about 3.5 times the width, distal end plate forming a crown of petal-like structures.

Figures

Fig. 1. Pseudostrandesia ratchaburiensis sp. nov., ♀. A. Paratype (MSU-ZOC.295). B. Paratype (MSU-ZOC.296). C–I. Holotype (MSU-ZOC.291). A. Cp, right lateral view. B. Cp, dorsal view. C. LV, internal view. D. RV, internal view. E. Posterior part of LV. F. Anterior part of LV. G. Muscle scars of RV.H. Anterior part of RV. I. Posterior part of RV. Scale bars: A–D = 100 μm; E–F, H–I = 50 μm; G = 20 μm. Arrows point toward the anterior end.

Fig. 2. Pseudostrandesia ratchaburiensis sp. nov., ♂. A. Paratype (MSU-ZOC.299). B. Paratype (MSU- ZOC.300). C–D. Allotype (MSU-ZOC.298). A. Cp, dorso-lateral view. B. Cp, slightly oblique ventral view. C. LV, internal view. D. RV, internal view (idem). Arrows point toward the anterior end. Scale bars: 100 μm.

Fig. 3. Pseudostrandesia ratchaburiensis sp. nov. Paratype, ♀ (MSU-ZOC.292). A. A1. B. A2. C. Terminal segment of A2. D. Md-palp. R–Rome organ.

Fig. 4. Pseudostrandesia ratchaburiensis sp. nov. Paratype, ♀ (MSU-ZOC. 292). A. Md-coxa. B. Mx1. C. A part of basal protopod with medial endite of T1. D. T1-palp.

Fig. 5. Pseudostrandesia ratchaburiensis sp. nov. Paratype, ♀ (MSU-ZOC. 292). A. T2. B. Distal part of T2. C. T3. D. CR. E. CR attachment.

Fig. 6. Pseudostrandesia ratchaburiensis sp. nov. Allotype, ♂ (MSU-ZOC.298). A. Distal end of penultimate segment and terminal segment of A2. B. Right prehensile palp. C. Left prehensile palp. D. Hemipenis. E. Zenker’s organ.