Strandesia hornei, 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 : 7-12

Strandesia hornei sp. nov. ( Figs 2–4)

Holotype. Female, with soft parts dissected in glycerine in a sealed slide, valves stored dry in a micropalaeontological slide (O.C.3129).

Paratypes. Two dissected females ( MSU-ZOC.050, MSU-ZOC.051) stored as the holotype and four undissected females (O.C.3130, MSU-ZOC.049, MSU-ZOC.052, MSU-ZOC.053) stored dry in micropalaeontological slides after use for SEM .

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

Type locality. Huai Prasatyai reservoir, Dan khuntod district, Nakhon Ratchasima Province, 10 November 2006, coordinates: 15° 07´22.7˝ N and 101° 33´22.8˝ E (TH119). Accompanying ostracod fauna: Bradleytriebella decorata ( Sars, 1903) , B. lineata (Victor & Fernando, 1981) , Cypridopsis sp. , Cyprinotus sp. , Cypris subglobosa Sowerby, 1840 , Hemicypris sp. , Physocypria sp.1 , Physocypria sp.2 , Potamocypris sp. , Pseudostrandesia mamarilorum (Victor & Fernando, 1981) , Stenocypris sp., Strandesia kraepelini ( Müller, 1906) .

Other localities. Nalao natural spring, Konsarn district, Chaiyaphum Province, 9 October 2007, coordinates: 16° 35´22˝ N and 101° 53´49.8˝ E (TH151). Accompanying ostracod fauna: Bradleystrandesia weberi ( Moniez, 1892) , Bradleytriebella lineata (Victor & Fernando, 1981) , Chrissia sp. , Cypretta sp.1 , Cypretta sp.2 , Cypretta sp.3 , Cypridopsis vidua (Müller, 1776) , Cypris subglobosa Sowerby, 1840 , Physocypria sp. , Pseudocypretta maculata Klie, 1932 , Pseudostrandesia mamarilorum (Victor & Fernando, 1981) , P. thailandensis sp. nov., Strandesia kraepelini ( Müller, 1906) , S. sanoamuangae sp. nov., Stenocypris sp., Thaicythere srisumonae Savatenalinton, Borgonie & Martens, 2008 .

Etymology. The new species is named after Prof. Dr. David J. Horne (Queen Mary University of London, Department of Geography, United Kingdom) in recognition of his outstanding contributions to research on Ostracoda and for his friendship with the second author spanning over many years.

Diagnosis. Carapace in lateral view elongated (length c. 1.8 times width), greatest height situated in front of mid-length; dorsal margin evenly arched, anterior margin broadly rounded, posterior margin more narrowly rounded; valve surface weakly pitted, with dispersed setae; carapace in dorsal view elongated, greatest width situated at mid-length; anterior and posterior extremities unequal; LV overlapping RV along anterior, ventral and posterior sides, LV with internal groove along valve margin, valve margin with large border, inner lamella without inner list; Wouters organ small, Rome organ long, aesthetasc ya shorter than short apical seta on A1; aesthetasc Y on A2 long; two large bristles on third endite of Mx1 distally serrated; d seta on T1 present; length of distal claw of caudal ramus less than half of that of ramus, length of proximal claw c. 2/3 of that of distal claw, distal seta slightly shorter than distal claw, proximal seta reaching far beyond tip of ramus; caudal ramus attachment stout, with Triebel’s loop situated at middle of distal part of main branch, dorsal and ventral branches well-developed.

Differential diagnosis. The new species is similar to Strandesia purpurescen s (Brady, 1886) and S. indica ( Hartmann, 1964) . It can be distinguished from both of them by the presence of a large border along the anterior, ventral and postero-ventral margins of the LV and the more tumid carapace in dorsal view as well as the conspicuously long proximal seta of the caudal ramus. Additionally, the new species is different from S. purpurescens by the continuously serrated ventral margins of the caudal ramus.

Measurements (in µ m). LV (n=2), L=878–891, H=441–453; RV (n=2), L=845–862, H=448–467; Carapace (n=4), L=861–907, W=434–441.

Ecology. Strandesia hornei sp. nov. has so far been found in 2 localities: in a man-made reservoir and a natural spring. In both cases, the pH was over 7.0 and the temperature ranged between 26.7–34.0° C.

Description of female. Carapace in lateral view ( Fig. 2A) elongated (length c. 1.8 times width), greatest height situated in front of mid-length; dorsal margin evenly arched, ventral margin slightly sinuous in front of mid-length, anterior margin broadly rounded, posterior margin more narrowly rounded, valve surface weakly pitted, set with dispersed setae.

Carapace in dorsal view ( Fig. 2B) elongated, greatest width situated at mid-length; anterior and posterior extremities unequal; LV overlapping RV along anterior, ventral and posterior margins.

Carapace in ventral view ( Fig. 2C): ventral margin of LV almost straight.

LV in interior view ( Fig. 2D) with a groove along valve margin; valve margin with large border; calcified inner lamella, anteriorly wide, without inner list, posteriorly more narrow.

RV in interior view ( Fig. 2E) without selvage; inner lamella without inner list; ventral margin slightly sinuous in front of mid-length.

A1 ( Fig. 3A): first segment with small proximal Wouters organ, long dorso-subapical seta (almost reaching tip of segment) and two long ventro-apical setae. Second segment slightly wider than long, with one short dorso-apical seta and a long Rome organ. Third segment bearing two (one dorso-, one ventro-) apical setae, the former reaching tip of fifth segment, the latter slightly longer than half of fourth segment. Fourth segment with two long dorsal setae and two subequal, short ventral setae (reaching tip of fifth segment). Fifth segment dorsally with two long setae, ventrally with two (one long, one short) setae, the short one reaching beyond tip of terminal segment. Penultimate segment with five (four long, one short) setae, length of the short one c. half of that of terminal segment. Terminal segment with three (two long, one short) apical setae and an aesthetasc ya, the latter shorter than short apical seta.

A2 ( Fig. 3B–C): exopodite with three (one long, two short) setae, the long one reaching tip of first endopodal segment. First endopodal segment with long natatory setae, length of shortest seta slightly more than half of that of penultimate segment, aesthetasc Y long, ventro-apical seta long (reaching beyond tip of terminal segment). Penultimate segment undivided, distally with three serrated claws (slightly longer than penultimate segment), 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 (t1–t4). Terminal segment with two serrated claws (GM and Gm), a g-seta and an aesthetasc y3, length of the latter c. half of that of accompanying seta.

Md-palp ( Fig. 3D–E): first segment with two large setae, one slender, long seta and a long, smooth α- seta. 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 hirsute setae, one shorter seta with setules 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 Ύ- seta and three further smooth apical setae, the former stout, hirsute, long (length c. 2.2 times of that of terminal segment); ventrally with two (one long, one short, the latter slightly less than half length of terminal segment) apical setae. Terminal segment ( Fig. 3E) bearing three claws and three setae.

Mx1 ( Fig. 4A) 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, the latter not reaching tip of terminal segment) subapical setae, terminal segment elongated, apically with three claws and three setae. Two large bristles on third endite distally serrated. Sideways directed bristles on first endite unequal, length of short one c. half of that of long one.

T1 ( Fig. 4B–C): protopodite with two short a-setae, long b and d-setae, distally with 14 (10 apical, four subapical) long, hirsute setae. Endopodite a weakly built palp with three unequal apical setae.

T2 ( Fig. 4D) with d1 c. 2.1 times longer than d2. Second segment with one long apical seta (length c. 2/3 of that of penultimate segment). Penultimate segment divided, proximal segment (a) bearing one long apical seta (reaching beyond tip of segment), distal segment (b) with a pair of apical setae (one short, one spine-like). Terminal segment with two (one dorsally, one ventrally) apical setae and a serrated claw.

T3 ( Fig. 4E) a cleaning limb. First segment with three long setae. Second segment with one long apical seta (slightly more than half of the next segment). Third segment with medially one long seta (not reaching tip of segment). Terminal segment with an apical pincer and one long reflexed subapical seta, length of the latter c. 3/4 of that of third segment.

Caudal ramus ( Fig. 4F) stout, with ventral margin serrated, distal and proximal claws long, serrated, length of distal claw less than half of that of ramus, length of proximal claw c. 2/3 of that of distal claw. Distal seta long (slightly shorter than distal claw), proximal seta markedly long (reaching far beyond tip of ramus).

Caudal ramus attachment ( Fig. 4G) stout, with Triebel’s loop situated at middle of distal part of main branch, dorsal and ventral branches well-developed.

Male unknown.

Remarks. Based on the external morphology of the carapace, the new species can be confused with S. purpurescens and S. indica . Characters of valves, especially in interior view, and extremities are needed for species identification in this group. For example, the morphology of the caudal ramus is different amongst these species. While the proximal seta is short in S. purpurescens and S. indica , it is markedly long in S. hornei sp. nov. In S. purpurescens , the ventral margin of the caudal ramus is set with seven groups of setae, whereas it is continuously serrated in S. hornei sp. nov. and S. indica . The distal seta reaches beyond the tip of the distal claw in S. purpurescens , while it is slightly shorter than the distal claw in S. hornei sp. nov. and S. indica . Other differences can be found in the pair of large bristles on the third endite of Mx1: smooth in S. purpurescens , serrated in S. hornei sp. nov.