Pseudostrandesia phetchabunensis, Savatenalinton & Martens, 2010

Savatenalinton, Sukonthip & Martens, Koen, 2010, On the subfamily Cypricercinae McKenzie, 1971 (Crustacea, Ostracoda) from Thailand, with the description of six new species 2379, Zootaxa 2379, pp. 1-77 : 40-44

Pseudostrandesia phetchabunensis sp. nov. ( Figs 25–27)

Holotype. A female, with soft parts dissected in glycerine in a sealed slide, and valves stored dry in a micropalaeontological slide (O.C.3139).

Paratypes. One dissected female ( MSU-ZOC.092) stored as the holotype and two undissected females (O.C.3140, MSU-ZOC.054) stored dry in micropalaeontological slides after use for SEM .

Repository. The holotype and one undissected paratype are deposited in the Ostracod Collection of the R. B.I.N.Sc. One dissected and one undissected paratype are deposited in the Natural History Museum , MSU (Mahasarakham, Thailand) .

Type locality. Nong Naree swamp, Muang district, Phetchabun Province, 28 September 2005, coordinates: 16° 26´23.7˝ N and 101° 08´29˝ E (TH051). Accompanying ostracod fauna: Bradleycypris vittata ( Sars, 1903) , Bradleytriebella decorata ( Sars, 1903) , Chrissia sp. , Hemicypris exigua Broodbakker, 1983 , Physocypria sp.3 , Pseudostrandesia calapanensis ( Tressler, 1937) , P. gaetani sp. nov., P. mamarilorum (Victor & Fernando, 1981) , P. thailandensis sp. nov., Sarscypridopsis sp. , Strandesia kraepelini ( Müller, 1906) .

Etymology. The new species is named after Phetchabun Province from where the species is described.

Diagnosis. Carapace in lateral view subelliptical, anterior and posterior margins broadly rounded, dorsal margin moderately arched, greatest height situated in front of mid-length; valve surface with dispersed setae; carapace in dorsal view subelliptical, greatest width situated at mid-length; LV overlapping RV along anterior, ventral and posterior margin, but more widely so anteriorly; LV with internal groove along valve margin, bor- der of valve wide anteriorly, more narrow posteriorly, inner lamella with one inner list; RV with marginal selvage; Wouters and Rome organs long, aesthetasc ya on A1 shorter than the short apical seta; aesthetasc Y on A2 long, aesthetasc y2 long; two large bristles on third endite of Mx1 serrated, d seta on T1 absent; length of distal claw of caudal ramus c. 2/5 of that of ramus, distal seta long; caudal ramus attachment with Triebel’s loop situated at middle of distal part of main branch, dorsal and ventral branches well-developed.

Differential diagnosis. Pseudostrandesia phetchabunensis sp. nov. resembles Pseudostrandesia calapanensis ( Tressler, 1937) . It can be distinguished from it by the larger anterior L/R overlap, the highly arched dorsal margin, the absence of the large selvage on the anterior margin of the RV, the length of the shortest apical seta on terminal segment of the A1 (conspicuously long in S. calapanensis ) and the morphology of two apical setae on the b segment of the penultimate segment of the T2. Thus far, the latter feature is not found in other species of Pseudostrandesia .

Measurements (in µ m). LV (n=1), L=782, H=387; RV (n=1), L=760, H=379; Carapace (n=2), L=765– 768, W=367–373.

Ecology. The new species has so far been found only from its type locality: Nong Naree swamp. It was found in water with a pH of 6.79 and a temperature of 27.6° C.

Description of female. Carapace in lateral view ( Fig. 25A) subelliptical, anterior and posterior margins both broadly rounded, dorsal margin moderately arched, greatest height situated in front of mid-length, ventral margin slightly sinuous; valve surface set with dispersed setae.

Carapace in dorsal view ( Fig. 25B) subelliptical, greatest width situated at mid-length; LV overlapping RV, more so anteriorly than posteriorly, posterior extremity symmetrical, bluntly pointed.

Carapace in ventral view ( Fig. 25C) with LV overlapping RV, ventral margin of LV slightly protruding at mid-length.

LV in interior view ( Fig. 25D) with groove along valve margin, dorsal margin arched, greatest height situated in front of mid-length, sloping down to anterior and posterior sides, both of these margins subequally rounded, ventral margin sinuous slightly in front of mid-length; inner lamella calcified, anteriorly more widely and set with one inner list, posterior calcified inner lamella more narrow.

RV in interior view ( Fig. 25E) with anterior marginal selvage; calcified inner lamella broad anteriorly, narrower posteriorly, without inner list.

A1 ( Fig. 26A) first segment with dorso-subapical seta short (not reaching tip of segment), two long, subequal ventro-apical setae and with long, tube-like proximal Wouters organ. Second segment slightly wider than long, with one short dorso-apical seta and long Rome organ. Third segment bearing two (one dorso-, one ventro-) apical setae, the former long (reaching beyond tip of fifth segment), the latter short (slightly more than half the length of fourth segment). Fourth segment dorsally with two long setae, ventrally with two subequal short setae (reaching tip of fifth segment). Fifth segment dorsally with two long setae, ventrally with two (one long, one shorter) setae, short one reaching half length of terminal segment. Penultimate segment with five (four long, one short) setae, the short one more than half of that of terminal segment. Terminal segment with three (two long, one short) apical setae and short aesthetasc ya, the latter shorter than short apical seta.

A2 ( Fig. 26B–C): exopodite with three (one long, two short) setae, the long one reaching tip of first endopodal segment. First endopodal segment with natatory setae long, shortest c. 1/3 of length of penultimate segment, aesthetasc Y long, ventro-apical seta long (reaching tip of penultimate segment). Penultimate segment undivided, distally with three serrated claws (slightly longer than penultimate segment) and with long aesthetasc y2 (reaching far beyond tip of terminal segment), z1–z3 setae long; medially with two (one long, one shorter) dorsal setae (short one length c. 2/3 of that of long one) and four ventral setae (t1–t4). Terminal segment ( Fig. 26C) with two serrated claws (GM and Gm), g-seta and aesthetasc y3, the latter with length c. 2/3 of that of accompanying seta.

Md-palp ( Fig. 26D–E): first segment with two large setae, one slender, long seta and long, smooth α- seta. Second segment dorsally with three (two long, one short) apical setae, short one with length c. 2/7 of that of long one; ventrally with a group of three hirsute setae, one shorter seta with setules and β- seta, the latter 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 Ύ–seta and three smooth apical setae, the former stout, hirsute, long (length c. 2.2 times of that of terminal segment); ventrally with one long, one short (length c. half of that of terminal segment) apical setae. Terminal segment ( Fig. 26E) bearing three claws and three setae.

Mx1 ( Fig. 26I) with a two-segmented palp, three endites and a large respiratory plate. Basal segment of palp with a group of five unequal long apical setae and two (one long, one shorter) subapical setae, shorter one reaching beyond tip of terminal segment; terminal segment elongated, with three claws and three setae. Two large bristles on third endite serrated. Sideways directed bristles on first endite unequal, length of short one length c. 2/3 of that of long one.

T1 ( Fig. 26G–H): protopodite with two short a-setae, long b-seta, without d-seta, distally with 14 (10 apical, four subapical) long, hirsute setae. Endopodite a weakly built palp with three unequal apical setae.

T2 ( Fig. 27A) with two slim d-setae, d1 1.7 times as long as d2. Second segment with one long apical seta (length slightly more than half of that of penultimate segment). Penultimate segment divided, proximal segment (a) bearing one long apical seta, distal segment (b) with a pair of apical setae (one short, one shorter), length of shorter one c. 2/3 of that of longer one. Terminal segment with two (one dorsally, one ventrally) short apical setae and a serrated claw.

T3 ( Fig. 27B–C) a cleaning limb. First segment with three long setae. Second segment with one long apical seta (c. half length of next segment). Third segment with medially one short seta (reaching tip of segment). Terminal segment with an apical pincer and one long reflexed subapical seta.

Caudal ramus ( Fig. 27E) stout, with ventral margin serrated, distal and proximal claws long, serrated, distal claw with length c. 2/5 of that of ramus, proximal claw c. 2/3 of length of distal claw. Distal seta long (length c. 5/6 of that of distal claw), proximal seta thin, short (not reaching tip of ramus).

Caudal ramus attachment ( Fig. 27D) stout, with Triebel’s loop situated at middle of distal part of main branch, dorsal and ventral branches well-developed.

Male unknown.

Remarks. Although the present new species has Pseudostrandesia calapanensis ( Tressler, 1937) as its closest congener, the identification is rather difficult as it also shares features with several other species, e.g. Pseudostrandesia ovata sp. nov., Strandesia indica Hartmann, 1964 and Strandesia hornei sp. nov. These latter species have elliptical carapaces, a large border on the anterior margin of the LV (except for S. indica ), and a LV largely overlapping the RV anteriorly. The new species is different from S. hornei sp. nov. by the absence of the d seta on T1, which is one of generic characters ( Savatenalinton & Martens 2009c), the absence of a large border on the ventral margin of the LV, inner lamella on the LV with one inner list and by the morphology of a pair of apical setae on the distal part of the penultimate segment of the T2. Pseudostrandesia phetchabunensis sp. nov. can be distinguished from S. indica by the more tumid carapace in dorsal view, the rounded posterior extremity and the presence of a large border on the anterior margin of the LV. Pseudostrandesia phetchabunensis sp. nov. is distinguishable from P. ovata sp. nov. by the shape of the carapace in lateral and dorsal views, the feature of a pair of apical setae on the distal part of the penultimate segment of T2 and by the presence of a long ventro- apical seta on the first endopodal segment of the A2.