Tanycypris siamensis Savatenalinton & Martens, 2009

Savatenalinton, Sukonthip, 2014, Ostracods (Crustacea: Ostracoda) from the floodplain of the Chi River, Mahasarakham Province, Northeast Thailand, with the first record of male Tanycypris siamensis Savatenalinton & Martens, 2009, Zootaxa 3838 (2), pp. 195-206 : 201

Tanycypris siamensis Savatenalinton & Martens, 2009

( Figs 2–3 )

Material examined. Three males, with soft parts dissected in a sealed glycerine slide, valves stored dry in a micropalaeontological slide (MSU-ZOC.102-104); two undissected males stored dry in micropalaeontological slides (MSU-ZOC.100, MSU-ZOC.101) and several undissected males kept in 70% ethyl alcohol.

Repository. All specimens are deposited in the Natural History Museum, MSU, Thailand.

Locality. Kud KamHeng (a small oxbow lake, number 12 in Fig 1 ), Mahasarakham Province, Thailand, collected by S. Savatenalinton, 21 February 2010.

Description of males. Carapace and valves as in female (see Savatenalinton & Martens 2009c), although somewhat smaller ( Fig. 2 ). All limbs as in female, except for last two segments of A2, T1 and reproductive organs ( Fig. 3 ); penultimate segment of A2 with claw-like z1 and z2 setae and with claw G1 and G3 reduced to setae ( Fig. 3 E); T1-endopodites forming asymmetrical prehensile palps; right palp ( Fig. 3 A) anteriorly with triangular lobe and two apical spines; left palp ( Fig. 3 B) anteriorly with elongated, curved lobe, two apical spines and a few small tubercles.

Hemipenis ( Fig. 3 C) with medial shield rounded, lateral shield subquadrate, distal end of lateral shield somewhat pointed. Postlabyrinthal spermiduct curved, with 2 loops. Zenker organ ( Fig. 3 D) set with c. 23 spiny whorls, length about 4.7 times the width, distal end plate forming a crown of petal-like structures.

Measurements (mean, in Μm). Carapace (n = 3), L = 1087, W = 300; LV (n = 2), L = 1075, H = 438; RV (n = 2), L = 1070, H = 440.

Ecology. This sexual population of T. siamensis which was composed of 97 female and 62 male specimens, occurred in an oxbow lake (Kud KamHeng) in the floodplain of the Chi River, with a water temperature of 28 °C, DO of 4.13 mg /L and a pH of 7. This species has now been found in reservoirs, natural springs, and an (oxbow) lake.

Figures

FIGURE 1. Sampled localities in floodplain of the Chi River, Mahasarakham Province, Thailand.

FIGURE 2. Tanycypris siamensis Savatenalinton & Martens, 2009, female (A – F) and male (G – K). A. Carapace, dorsal view (MSU-ZOC. 097). B. Carapace, right lateral view (MSU-ZOC. 098). C. Carapace, right lateral view, showing valve surface (idem). D. Left valve, internal view (MSU-ZOC. 099). E. Right valve, internal view (idem). F. Right valve, internal view, showing muscle scars (idem). G. Carapace, dorsal view (MSU-ZOC. 100). H. Carapace, right lateral view (MSU-ZOC. 101). I. Left valve, internal view (MSU-ZOC. 102). J. Right valve, internal view (idem). K. Right valve, internal view, showing muscle scars (idem). Scale bars: 100 Μm for A – B, D – E, G – J, 10 Μm for C and 20 Μm for F, K. Arrows point toward the anterior end.

FIGURE 3. Tanycypris siamensis Savatenalinton & Martens, 2009, male. A. Right prehensile palp (MSU-ZOC. 101). B. Left prehensile palp (idem). C. Hemipenis (idem). D. Zenker organ (idem). E. Distal end of penultimate segment and terminal segment of A 2 (MSU-ZOC. 102). Scale bar: 50 Μm.