Strandesia prachuapensis, Savatenalinton, 2021

Savatenalinton, Sukonthip, 2021, Two new species of Cypricercinae McKenzie, 1971 (Crustacea: Ostracoda) from Thailand, European Journal of Taxonomy 733, pp. 19-41 : 29-36

Strandesia prachuapensis sp. nov.

urn:lsid:zoobank.org:act:9F78C65D-157A-4E1C-9601-37399A71C764

Figs 7–10

Diagnosis

Cp large (ca 1.5 mm), elongated in lateral view (length ca 1.7 times of height), LV with angulated antero-ventral part, a weak and small anterior inner list situated on antero-ventral part, RV with anterior flange, not close to mouth region, A1 seven-segmented with small Rome organ, A2 with long natatory setae, aesthetasc Y markedly small (short and slender) with insertion situated ca one fourth of segment, β-seta on Md-palp large, two large bristles on third endite of Mx1 smooth, d-seta on T1 present, T2 with d1 and d2 setae (length of d2 seta less than half length of d1 seta), f-seta of intermediate length (not reaching tip of terminal segment), T3 with pincer organ, CR slender, claw Ga ca ⅓ of ramus, claws Ga and Gp and ventral margin of ramus with tiny spine-like setules, sa seta slightly longer than claw Gp, sp seta slender, reaching slightly beyond tip of ramus, CR attachment with Triebel’s loop situated at middle of distal part of main branch.

Differential diagnosis

Strandesia prachuapensis sp. nov. resembles S. flavescens Klie, 1932 and S. odiosa ( Moniez, 1892) . It can be distinguished from them mainly by the narrower anterior flange on the RV, the size of the Cp (ca 1.5 mm), the angulated antero-ventral part of the LV and the small and weak anterior inner list on the LV (for details of the differences, see the Discussion).

Etymology

The species is named after Prachuap Khiri Khan Province, which is also called in short ‛Prachuapʼ, where specimens of the new species were discovered.

Type material

Holotype THAILAND – Prachuap Khiri Khan Province • ♀ (soft parts dissected in glycerine on a sealed glass slide and valves stored dry in a micropalaeontological slide); Kui Buri District , rice field; 12º06.36′ N, 99º48.42′ E; 21 Oct. 2018; MSU-ZOC.303 .

Paratypes THAILAND – Prachuap Khiri Khan Province • 3 ♀♀ (carapaces stored dry in micropalaeontological slides); same collection data as for holotype; MSU-ZOC.304 to 306 .

Type locality

A total of 4 female specimens (1 holotype, 3 paratypes) were collected at the type locality on 21 Oct. 2018. Accompanying ostracod fauna: Cypretta sp., Cypris subglobosa Sowerby, 1840 , Dentocypria aequiloba Savatenalinton, 2017 , Hemicypris exigua Broodbakker, 1983 , Hemicypris ovata Sars, 1903 , Ilyocypris monstrifica (Norman, 1862) , Notodromas sp., Pseudostrandesia mamarilorum , Stenocypris orientalis Victor & Fernando, 1981 .

Repository

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

Measurements (in μm)

Cp (n = 3), L = 1446–1483, H = 836–848, W = 662-677; LV (n = 1), L = 1483, H = 848; RV (n = 2), L = 1434, H = 800.

Description

Female

CP. Large (ca 1.5 mm), elongated in lateral view ( Fig. 7A ) (length ca 1.7 times height), anterior and posterior margins widely rounded, LV overlapping RV posteriorly and ventrally, dorsal margin gently arched, greatest height situated at mid-length, valve surface set with short rim-pore setae.

CP IN DORSAL VIEW ( Fig. 7B ). Subelliptical, with greatest width situated at mid-length, anterior margin of RV slightly protruded than LV.

LV IN INTERNAL VIEW ( Fig. 7C , E–F). With groove along valve margin, dorsal margin arched, greatest height situated slightly in front of mid-length; sloping down to anterior and posterior margin, the former widely rounded, the latter slightly less widely rounded, antero-ventral part angulated, ventral margin slightly sinuated at mid-length; calcified inner lamella relatively wide anteriorly, with a weak and small inner list situated on antero-ventral part, posteriorly narrower.

RV IN INTERNAL VIEW ( Fig. 7D , G–H). With inwardly displaced selvage and anterior flange, the latter not close to mouth region, calcified inner lamella without inner list, anteriorly broader than posteriorly.

A1 ( Fig. 8 A–Aʹ). First segment with one dorso-subapical seta of intermediate length (almost reaching tip of segment) and two long ventro-apical setae, Wouters organ absent. Second segment slightly wider than long, with one markedly short dorso-apical seta (reaching tip of segment) and small Rome organ. Third segment bearing two (one dorso-apical and one ventro-apical) setae of intermediate length, both reaching slightly beyond tip of next segment. Fourth segment with two long dorsal setae and two subequal, shorter ventral setae (the short one not reaching tip of next segment, 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 beyond tip of terminal segment. Penultimate segment with four long setae. Terminal segment with three (two long, one short) apical setae and aesthetasc y a, the latter markedly long (ca 1.7 times that of short apical seta).

A2 ( Fig. 8B ). 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 tip of terminal claws) and one short natatory setae, length of the shortest seta reaching half way the penultimate segment, aesthetasc Y small (short and slender), insertion situated ca ¼ of segment, ventro-apical seta long, reaching slightly beyond tip of penultimate segment. Penultimate segment undivided, distally with three serrated claws G1–G3, aesthetasc y2 short (not 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 ca ¾ 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 with accompanying seta, length of Gm ca ¾ of that of GM, length of aesthetasc y3 more than half of that of Gm and slightly shorter than accompanying seta, length of g-seta ca ¾ of aesthetasc y3.

MD- COXA ( Fig. 8C ). Elongated, distally bearing rows of teeth (large dorsally and smaller ventrally) and small setae, and one dorso-subapical seta situated close to palp.

MD- PALP ( Fig. 9A ). 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 the shortest seta less than half of that of the longest seta; ventrally with a group of three long hirsute setae, one shorter hirsute seta and large β-seta (length ca ¾ of that of penultimate segment), the latter large, plumose, cone-shaped and with pointed tip. Penultimate segment consisting of 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 1.5 times of that of terminal segment); ventrally with two (one long, one short) apical setae, the latter reaching ¼ of length of terminal segment. Terminal segment bearing three claws and two setae.

MX 1 ( Fig. 9B ). With two-segmented palp, three endites and large branchial plate; basal segment of palp with a group of five long, unequal apical setae and two (one long, one shorter) subapical setae, the latter reaching half way of terminal segment, terminal segment elongated, apically with three claws and three setae. Two large bristles on third endite smooth. Sideways-directed bristles on first endite unequally long, length of short one ca half of that of long one.

T1 ( Fig. 9C ). Protopodite with two short a-setae, long b and d-setae, masticatory process distally with 14 (10 apical, four subapical) hirsute setae of unequal length. Endopodite a weakly built palp with three unequal apical setae.

T2 ( Fig. 10A ). With seta d1 more than twice the length of seta d2. Second segment with short e-seta (reaching slightly beyond mid-length of penultimate segment). Penultimate segment divided, proximal segment bearing f-seta of intermediate length (not reaching tip of terminal segment), distal segment with a short g-seta (reaching slightly beyond tip of terminal segment). Terminal segment with two (one dorsally, one ventrally) apical h1 and h3 setae and a serrated claw (h2), h1 and h3 setae subequal in length, length of claw h2 longer than that of penultimate segment.

T3 ( Fig. 10B ). A cleaning limb. First segment with long d1, d2, dp setae. Second segment with long apical e-seta (ca ½ 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 ca ½ of that of third segment.

CR ( Fig. 10 C–D). Slender, claws Ga and Gp weakly serrated, claw Ga short (ca ¼ of ramus), length of claw Gp ca 3/5 of that of claw Ga, sa seta slightly longer than claw Gp, sp seta slender, reaching slightly beyond tip of ramus, ventral margin of ramus with tiny setules.

CR ATTACHMENT ( Fig. 10E ). With Triebel’s loop situated at middle of distal part of main branch, db and vb well-developed, vb with swollen end.

Male

Unknown.

Figures

Fig. 7. Strandesia prachuapensis sp. nov., ♀. A. Paratype (MSU-ZOC.304). B. Paratype (MSU- ZOC.305). C–H. Holotype (MSU-ZOC.303). A. Cp, left 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. Anterior part of RV. H. Posterior part of RV (idem). Scale bars: A–D = 200 μm; E–H = 100 μm. Arrows point toward the anterior end.

Fig. 8. Strandesia prachuapensis sp. nov. Holotype, ♀ (MSU-ZOC.303). A. A1. Aʹ. Aesthetasc-like setae on third and fourth segments of A1. B. A2. C. Md-coxa. R–Rome organ.

Fig. 9. Strandesia prachuapensis sp. nov. Holotype, ♀ (MSU-ZOC.303). A. Md-palp. B. Mx1. C. Basal protopod with medial endite of T1. D. T1-palp.

Fig. 10. Strandesia prachuapensis sp. nov. Holotype, ♀ (MSU-ZOC.303). A. T2. B. T3.C. CR. D. Distal end of CR. E. CR attachment.