Strandesia martensi, 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 : 276-282

Strandesia martensi n. sp.

( Figures 1–3 )

Holotype. Female, soft parts dissected in glycerine on a sealed glass slide, valves stored dry in a micropalaeontological slide (MSU-ZOC.105).

Paratypes. Five dissected females (MSU-ZOC.106–110) stored like the holotype, five undissected female carapaces (MSU-ZOC.111–115) stored dry in micropalaeontological slide and c. 30 females in 70% EtOH.

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

Type locality. Phan Reservoir (swamp), Udon Thani Province ( Tab. 1 ). 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 pholpunthini n. sp., Strandesia kraepelini ( G.W. Müller, 1906) .

Other localities. 1) Bung Khong Long (swamp), Bueng Kan Province. Material collected on 30 January 2011, coordinates: 17° 57΄ 35˝ N and 104° 02΄ 06˝ E. Accompanying ostracod fauna: Alicenula sp., Cypridopsis sp., Fabaeformiscandona subacuta, (Yang, 1982) , Limnocythere sp., Thaicythere srisumonae Savatenalinton et al., 2008 , Physocypria sp.1, Physocypria sp.2, Pseudostrandesia striatoreticulata ( Klie, 1932) , Strandesia kraepelini ( G.W. Müller, 1906) .

2) Kud Thing (swamp), Bueng Kan Province. Material collected on 30 January 2011, coordinates: 18° 20΄ 36˝ N and 103° 39΄ 52˝ E. Accompanying ostracod fauna: Cypretta sp., Thaicythere srisumonae Savatenalinton et al., 2008 , Physocypria sp.1, Physocypria sp.2.

Etymology. The new species is named after Prof. Dr. Koen Martens (Royal Belgian Institute of Natural Sciences, Brussels) in recognition of his outstanding contributions to research on Ostracoda and for his warm hospitality during my study in Belgium.

Diagnosis. Carapace in lateral view subovate, with dorsal hump on both valves situated in front of mid-length; valve surface set with pits and robust, long setae, arising from both rimmed and un-rimmed-pores; LV overlapping RV anteriorly, ventrally and posteriorly; carapace in dorsal view sub-elliptical, with greatest width situated at midlength; LV with groove along valve margin; inner lamella calcified with one inner list; two large bristles on third endite of Mx1 smooth; d-seta on T1 present; length of Ga of caudal ramus c. 1/3 of that of ramus, Sp markedly long (reaching half of Gp); CR attachment stout, with Triebel’s loop situated at middle of distal part of main branch, db short, vb well-developed.

Differential diagnosis. Strandesia martensi n. sp. is similar to Strandesia perakensis Victor & Fernando, 1981 and Strandesia sanoamuangae Savatenalinton & Martens, 2010 . The new species can be distinguished from these two species by the presence of a large dorsal hump on both valves, large anterior LV/RV overlap, the shape of the valves and the ornamentation of the valve surface, which is set with pits, long spines and long rim-pore setae in S. martensi n. sp.; with tiny tubercles and long rim-pore setae in S. sanoamuangae and with pits, long setae and short spines in S. perakensis . In addition, the chaetotaxy of the limbs shows differences amongst them, especially by the long Sp of the CR in the new species.

Measurements (mean, in µm). LV (n = 3), L = 865, H = 624; RV (n = 3), L = 835, H = 620; carapace (n = 3), L = 878, W = 459.

Ecology. The new species is known from three localities. All localities are swamps, which have dense and diverse macrophytes in the littoral zone. The species occurs at a pH range of 7.1–7.6, a temperature range of 26.1–31.7° C and a dissolved oxygen range of 3.3–6.6 mg /l.

Description of female. Carapace in lateral view ( Fig. 1 A) subovate, anterior margin widely rounded, posterior margin more narrowly rounded, LV widely overlapping RV, especially anteriorly, dorsal margin with dorsal hump situated slightly in front of mid-length, ventral margin rather straight, valve surface set with pits, long spines and long rim-pore setae ( Fig. 1 D).

Carapace in dorsal view ( Fig. 1 C) subelliptical, with greatest width situated at mid-length, LV overlapping RV anteriorly and posteriorly, anterior margin of LV sharply curved with a large flange.

LV in interior view ( Fig. 1 F) with groove along valve margin, dorsal margin slightly concave, greatest height situated in front of mid-length; sloping down to anterior and posterior margin, the former widely rounded, the latter more narrowly rounded, ventral margin almost straight; calcified inner lamella relatively wide anteriorly, with one inner list, posteriorly narrower.

RV in interior view ( Fig. 1 G) with marginal selvage, inner lamella without inner list, anteriorly broader than posteriorly.

A1 ( Fig. 2 A): first segment with elongated proximal Wouters organ, one dorso-subapical seta of intermediate length (almost reaching tip of segment) and two long ventro-apical setae. Second segment slightly wider than long, with one long dorso-apical seta (reaching tip of the next segment) and a long Rome organ. Third segment bearing three setae: one long dorso-apical one, reaching halfway penultimate segment, and two shorter ventro-apical setae, one reaching slightly beyond the tip of fourth segment and another one spine-like. Fourth segment with two long dorsal setae and two subequal, shorter ventral setae (the long one reaching beyond half of penultimate segment). Fifth segment dorsally with two long setae, ventrally with two (one long, one shorter) setae, the shorter one reaching beyond tip of penultimate segment. Penultimate segment with four long setae. Terminal segment with three (two long, one short) apical setae and an aesthetasc y a, the latter c. twice as long as the short apical seta.

A2 ( Fig. 2 B): exopodite with three (one long, two short) setae, the long one reaching 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 reaching more than half way the penultimate segment, aesthetasc Y long, ventroapical seta long, reaching beyond tip of terminal segment. Penultimate segment divided, distally with three serrated claws, aesthetasc y2 long (reaching 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 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), a g-seta and an aesthetasc y3, length of Gm c. 3/4 of that of GM, length of aesthetasc y3 c. half of that of accompanying seta, the latter of similar length as seta g.

Md-palp ( Fig. 2 C): first segment with two large setae (s1 and s2), one slender, long seta and a long, smooth αseta. Second segment dorsally with three unequal long apical setae, length of the shortest c. 1/3 of that of the longest; ventrally with a group of three long 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 unequal, long, subapical setae; laterally with an apical γ-seta and three further smooth apical setae, the former stout, hirsute, long (length c. 2.3 times of 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 ( Fig. 2 D) bearing three claws and three setae.

Mx1 ( Fig. 3 A) with two-segmented palp, three endites and a 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 beyond tip of terminal segment (length c. twice that 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 c. 4/5 of that of long one.

T1 ( Fig. 3 B): protopodite with two short a-setae, long b and d-setae, distally with 14 (10 apical, four subapical) hirsute setae of unequal length. Endopodite a weakly built palp with three unequal apical setae.

T2 ( Fig. 3 C) with seta d1 c. twice the length of seta d2. Second segment with long e-seta (reaching c. 2/3 of penultimate segment). Penultimate segment divided, proximal segment (a) bearing long f-seta (reaching beyond tip of terminal segment), distal segment (b) with a pair of apical setae (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. 3 D) a cleaning limb. First segment with long d1, d2, d3 setae. Second segment with long apical e-seta (slightly less than half of the next segment). Third segment with medially long f-seta (reaching 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 c. 3/4 of that of third segment.

CR ( Fig. 3 E) well-developed, with ventral margin serrated, bearing c. 7 groups of setulae, Ga and Gp long, serrated, length of Ga c. 1/3 that of ramus, length of Gp c. 2/3 that of Ga. Sa long (slightly shorter than Gp), Sp markedly long (reaching half the length of Gp).

CR attachment ( Fig. 3 F) stout, with Triebel’s loop with two eyelets, situated at middle of distal part of main branch, db and vb well-developed.

Male unknown.

Remarks. The presence of dorsal hump occurs in several Strandesia species, for example, S trandesia mercatorum (Vávra, 1895) , S trandesia cyprinotoides Klie, 1938, S trandesia elatior (Vávra, 1897), S trandesia evae Gauthier, 1951, and is now also known from S trandesia martensi n. sp. Although the shape of dorsal hump differs between these species, the dorsal hump appears on the RV only, except in S. martensi n. sp., where it is found on both valves. Based on this character, S. martensi n. sp. is superficially similar to Sataracypris gibbosa (Baird, 1837) . Sataracypris is an uncertain and monospecific genus, which was established by Deb (1983) using Cypris gibbosa Baird, 1837 as type species. In her view, the appearance of the prominent dorsal hump was the main character to separate the species from other species in the genus Cypris and therefore a new genus was created for it. The discovery of S. martensi n. sp. in this study revealed that S. gibbosa probably belongs to the lineage of Strandesia in which the dorsal hump is present and prominent on both valves.

There are several differences between Sataracypris gibbosa and Strandesia martensi n. sp. There is a large anterior valve overlap in S. martensi n. sp., which is absent in S. gibbosa . This character can be clearly seen from carapaces in both lateral and dorsal views. The valve surface is ornamented by thin, scanty setae in S. gibbosa , whereas it is set with pits, long spines and long seta in rimmed pores in S. martensi n. sp. In S. gibbosa , the penultimate segment of A2 is undivided, while this segment is divided in S. martensi n. sp., although this may also be an erroneous observation in S. gibbosa . In addition, the new species differs from S. gibbosa in the morphology of the CR, which is more slender, with the Sp markedly long and with the length of the ramus c. twice of that of Ga in S. martensi n. sp. Sataracypris gibbosa , on the other hand, has stout caudal rami, a short Sp and relatively shorter rami (length c. 1.5 times of Ga). The morphology of the CR attachment remains unknown in S. gibbosa . As all Strandesia –species have Triebel’s loops on the attachments of the caudal rami (it is a synapomorphy of the entire subfamily Cypricercinae ), the redescription of S. gibbosa is thus needed before a new taxonomic position can be proposed.

Figures

FIGURE 1. Strandesia martensi n. sp. A. carapace, right lateral view; B. carapace, left lateral view; C. carapace, dorsal view; D. valve surface of A.; E. muscle scars of G.; F. LV, internal view; G. RV, internal view. Scale bar = 100 Μm for A – C, F – G; = 16 Μm for D; 40 Μm for E. Arrow points toward the anterior end.

FIGURE 2. Strandesia martensi 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.

FIGURE 3. Strandesia martensi n. sp. A. Mx 1; B. T 1; C. T 2; D. T 3; E. caudal ramus; F. caudal ramus attachment. Scale bar = 50 Μm for A – B; 100 Μm for C – F.

Tables

TABLE 1. List of sampling localities.

Locality	Coordinates	Collected date	Temp (°C) pH	DO (mg/l)
Phan Reservoir,	17° 50΄ 03˝ N, 103° 04΄ 21˝ E	31/01/2011	30.3 7.1	6.60
Udon Thani Province
Bung Khong Long,	17° 57΄ 35˝ N, 104° 02΄ 06˝ E	30/01/2011	26.1 7.6	7.25
Bueng Kan Province
Kud Thing,	18° 20΄ 36˝ N, 103° 39΄ 52˝ E	30/01/2011	31.7 7.4	7.21
Bueng Kan Province
Huay Yang Reservoir,	16° 56΄ 12˝ N, 104° 10΄ 42˝ E	21/12/2011	24.3 7.5	4.60
Sakon Nakhon Province