Strandesia pholpunthini, Savatenalinton, Sukonthip, 2015

Savatenalinton, Sukonthip, 2015, On three new species of non-marine ostracods (Crustacea: Ostracoda) from Northeast Thailand, Zootaxa 3914 (3), pp. 275-300 : 282-287

Strandesia pholpunthini n. sp.

( Figures 4 –6)

Holotype. Female, soft parts dissected in glycerine on a sealed glass slide, valves stored dry in a micropalaeontological slide (MSU-ZOC.116).

Paratypes. One dissected female (MSU-ZOC.117) stored like the holotype, one undissected female (MSU- ZOC.118) stored dry in a micropalaeontological slide.

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

Type locality. Phan Reservoir (swamp), Udon Thani Province. Material collected on 31 January 2011, coordinates: 17° 50΄ 03˝ N and 103° 04΄ 21˝ E. Accompanying ostracod fauna: Astenocypris papyracea ( Sars, 1903) , Chrissia sp., Cypretta sp.1, Cypretta sp.2, Cypridopsis sp. Physocypria sp., Pseudocypretta maculata Klie, 1932 , Pseudostrandesia striatoreticulata ( Klie, 1932) , Strandesia kraepelini ( G.W.Müller, 1906) , Strandesia martensi n. sp.

Etymology. The new species is named after Assoc. Prof. Dr. Pornsilp Pholpunthin (Prince of Songkla University, Songkla, Thailand) in recognition of his prominent contributions to aquatic science and taxonomy in Thailand.

Diagnosis. Carapace in lateral view elongated (length 1.9 times width), greatest height situated in front of midlength; anterior margin broadly rounded, posterior margin more narrowly rounded; carapace in dorsal view subelliptical, with greatest width situated at mid-length, anterior and posterior extremity with different asymmetry: LV overlapping RV anteriorly, RV overlapping LV posteriorly, posterior extremity slightly compressed on RV. LV in interior view with groove along valve margin, greatest height situated at c. 1/3 of length, inner lamella anteriorly wide, without inner list, posteriorly narrower. RV in interior view with marginal selvage, inner lamella without inner list, posterior part with large flange; A1 with short Rome organ, aesthetasc Y on A2 long; one large bristle on third endite of Mx1 smooth, another one serrated; d seta on T1 present; length of Ga of CR c.1/3 of that of ramus, Sp stout and long; CR attachment stout, with Triebel’s loop situated at middle of distal part of main branch, db short, vb well-developed.

Differential diagnosis. Strandesia pholpunthini n. sp. has Strandesia caudata Klie, 1939 as its closest congener. It can be distinguished by the shape of the posterior part in dorsal view, which is compressed at the posterior extremity of the RV in Strandesia pholpunthini n. sp. (this feature is absent in S. caudata ) and by the large flange at posterior part of the RV in internal view.

Measurements (mean, in µm). LV (n = 2), L = 1161, H = 657; RV (n = 2), L = 1163, H = 652; Carapace (n = 1), L=1135, W = 581.

Ecology. The new species is only known from the type locality, in which dense macrophyte stands occupy the littoral zone. It occurs at a pH of 7.1, a temperature of 30.3° C and a dissolved oxygen content of 6.6. mg/l.

Description of female. Carapace in lateral view ( Fig 4 A) elongated (length c. 1.89 times width), greatest height situated in front of mid-length, dorsal margin slightly unevenly arched, ventral margin slightly sinuous in front of mid-length, anterior margin broadly rounded, posterior margin more narrowly rounded; valve surface weakly reticulated ( Fig. 4 B–C).

Carapace in dorsal view ( Fig. 4 D) subelliptical, greatest width situated at mid-length, LV overlapping RV anteriorly, RV overlapping LV posteriorly, anterior and posterior extremity unequal, posterior extremity compressed on RV.

LV in interior view ( Fig. 4 E) with groove along valve margin, dorsal margin curved, greatest height situated at c. 1/3 of length, sloping down to anterior and posterior margin, the former widely rounded, the latter more narrowly rounded; ventral margin slightly sinuous; inner lamella calcified, anteriorly wide, without inner list, posteriorly narrower.

RV in interior view ( Fig. 4 F) with marginal selvage, inner lamella without inner list, anteriorly broader than posteriorly; ventral margin slightly sinuous in front of mid-length, posterior part with large flange.

A1 ( Fig. 5 A): first segment with a long dorsal, subapical seta (reaching mid-length of the next segment), with two long ventro- apical setae, no proximal Wouters organ. Second segment slightly wider than long, with one short dorso-apical seta and a short Rome organ. Third segment bearing two (one shorter dorso-, one long ventro-) apical setae, the former reaching tip of next segment, the latter reaching tip of fifth segment. Fourth segment with two long dorsal setae and two shorter ventral setae (the longer one reaching beyond tip of fifth segment, the shortest with length c.2/3 of next segment. Fifth segment dorsally with two long setae, ventrally with two (one long, one short) setae, the short one reaching beyond half of 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 slightly shorter than the short apical seta.

A2 ( Fig. 5 B): exopodite with three (one long, two short) setae, the long one reaching beyond tip of first endopodal segment. First endopodal segment with six (five long, one shorter) natatory setae, the shorter seta reaching c. 1/3 of next segment, aesthetasc Y long, ventro-apical seta long (reaching beyond tip of terminal segment). Penultimate segment undivided, distally with three serrated claws (length c. 1.2 times penultimate segment) and with long aesthetasc y2 (reaching beyond tip of terminal segment), z1–z3 setae long but not reaching tips of claws; this segment medially with two (one long, one shorter) dorsal setae (length of short one c. 2/3 of that of long one) and four ventral setae of unequal length (t1–t4), the shortest one reaching tip of segment. Terminal segment with two serrated claws (GM and Gm), a long g-seta and an aesthetasc y3, length of Gm c. 2/3 of that of GM, length of aesthetasc y3 c. 2/3 of that of accompanying seta.

Md-palp ( Fig. 5 C): first segment with two large setae set with setulae (S1 and S2), one slender, long seta and a long, smooth α-seta, the latter basally widened, length c. half of that of large setae. Second segment dorsally with three unequal long apical setae, length of the shortest c. 45% of that of the longest; ventrally with a group of three hirsute setae, one shorter hirsute seta and the 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 long, but unequal subapical setae; laterally with an apical γ–seta and three further apical setae, the former stout, hirsute, long (length c. 2 times of that of the terminal segment); ventrally with two (one long, one short) apical setae, length of the short one c. half the length of terminal segment. Terminal segment ( Fig. 5 D) bearing three claws and three setae.

Mx1 (Fig. 6A) with a two-segmented palp, three endites and a large branchial plate. Basal segment of palp with a group of five long, but unequal apical setae and two (one long, one shorter) subapical setae, the shorter one reaching slightly beyond mid-length of terminal segment; terminal segment elongated, with three claws and tree setae. Third endite with two large bristles, one distally serrated, another one smooth. Sideways-directed bristles on first endite unequal, length of short one c. 2/3 of that of long one.

T1 (Fig. 6B–C): protopodite with two short a-setae, a long b seta and a d-seta, distally with 14 (10 apical, four subapical) long, hirsute setae. Endopodite a weakly built palp with three unequal apical setae.

T2 (Fig. 6D) with d-setae, length of d2 c. 3/4 of that of d1. Second segment with one long apical e-seta reaching half of penultimate segment. Penultimate segment divided, proximal segment (a) bearing one long apical f-seta (reaching beyond tip of terminal segment), distal segment (b) with a pair of apical setae (one long g-seta, one spine-like). Terminal segment with two (one dorsally, one ventrally) apical h1 and h3 setae and a serrated claw (h2).

T3 (Fig. 6E) a cleaning limb. First segment with long d1, d2, d3 setae. Second segment with one markedly long apical e-seta (length almost equal of that of next segment). Third segment with medially one 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 long reflexed subapical h3 seta, length of the latter c. 7/10 of that of third segment.

CR (Fig. 6F) stout, with ventral margin strongly serrated, Ga and Gp long, serrated, length of Ga slightly less than half of that of ramus, length of Gp c. 2/3 of that of Ga; Sa long (slightly longer than Gp), Sp long (reaching beyond tip of ramus).

CR attachment (Fig. 6G) stout, with Triebel’s loop at middle of distal part of main branch, db short, vb welldeveloped.

Male unknown.

FIGURE 6. Strandesia pholpunthini n. sp. A. Mx1; B. T1; C. T1; D. T2; E. T2; F. T3; G. caudal ramus; H. caudal ramus attachment. Scale bar = 50 Μm for A–B; 100 Μm for C–D, F–H; 58 Μm for E.

Remarks. Most of the species in Strandesia and indeed in all genera of the subfamily Cypricercinae have the LV overlapping the RV on all sides. The combination of a LV overlapping a RV anteriorly and a RV overlapping a LV posteriorly is seen in few Strandesia species, such as Strandesia obtusata (Sars, 1901) , Strandesia mulargiae Anichini, 1967 , and Strandesia caudata Klie, 1939 . However, the morphology of carapace in dorsal view is different in the new species; for example, the posterior part of the RV is evenly round without valve compression in S. obtusata , S. mulargiae , and S. caudata while it is compressed in Strandesia pholpunthini n. sp.

Figures

FIGURE 4. Strandesia pholpunthini n. sp. A. carapace, left lateral view; B. valve surface of anterior part of A.; C. valve surface of postero-dorsal part of A.; D. carapace, dorsal view; E. LV, internal view; F. RV, internal view. Arrow points toward the anterior end. Scale bar = 100 Μm for A, D – F; 12 Μm for B – C.

FIGURE 5. Strandesia pholpunthini n. sp. A. A 1; B. A 2; C. Md-palp; D. Md-palp, terminal segment; E. Md-coxa. Scale bar = 100 Μm for A – B, E; 50 Μm for C – D.