Cypretta triangulata, Savatenalinton, 2018

Savatenalinton, Sukonthip, 2018, Two new species of Cypretta Vávra, 1895 (Crustacea, Ostracoda) from Thailand and discussion of genus, Zootaxa 4532 (4), pp. 483-502 : 489-494

Cypretta triangulata n. sp.

( Figs 4–6 , 7 E–H)

2016 Cypretta sp. 2—Savatenalinton & Suttajit: 4, Table 2.

Holotype. Female, soft parts dissected in glycerine on a sealed glass slide, and valves stored dry in a micropalaeontological slide ( MSU-ZOC.240).

Paratypes. Three dissected females ( MSU-ZOC. 241–243) stored like the holotype, two undissected female carapaces ( MSU-ZOC. 244–245) stored dry in micropalaeontological slides and several females in 70% EtOH .

Type locality. Pond, Wangpikul village, Phitsanulok Province, collected on September 27 th 2005, coordinates: 16° 45΄ 13˝ N and 100° 18΄ 24˝ E. Accompanying ostracod fauna: Bradleystrandesia weberi ( Moniez, 1892) , Cypris subglobosa Sowerby, 1840 , Hemicypris exigua Broodbakker, 1983 , Stenocypris orientalis Victor & Fernando, 1981, Chrissia sp.

Other localities. 13 localities (see Table 2 in appendix).

Etymology. The species name “triangulata” refers to the conspicuous triangular carapace shape in dorsal view.

Diagnosis. Carapace in dorsal view subtriangular with greatest width situated at three fourth from anterior. Carapace in lateral view subelliptical, anterior and posterior margins subequally rounded, dorsal margin slightly arched, greatest height slightly situated in front of mid-length, RV overlapping LV anteriorly, ventrally, posteriorly. Septa well developed along anterior margins (c.12–13 septa). Valve surface set with setae and mildly shallow pits. LV in internal view: anterior inner lamella wide with straight lines, anterior margin slightly sinuated inwardly, postero-ventral margin without tubercles. RV in internal view: anterior inner lamella wide with sinuated inner list, postero-ventral part with denticulated ridge (c. 9–11 denticles). Length of A1 aesthetasc ya c. 8 times that of terminal segment. Shortest natatory seta of A2 reaching beyond tips of terminal segment. Two large bristles on third endite: one slightly serrated distally, another one smooth. b- and c- setae on T1 absent. d1 seta on T2 short (c. half of d2 seta). T3 with short e-seta (shorter than half of next segment) and short f-seta (not reaching tip of segment). CR with Ga and Gp thin and very long, length of Ga c. 4/5 of that of ramus, length of Gp c. 3/5 of that of Ga; Sa absent, Sp short (c. half of Gp).

Measurements (in µm). Female, carapace, L = 540–561 (n = 5), H = 340–345 (n = 5), W = 455–465 (n = 5); LV, L = 500–553 (n = 8), H = 300–340 (n = 8); RV, L = 510–555 (n = 8), H = 310–350 (n = 8).

Description of female. Carapace in dorsal view ( Fig. 4A ) triangular with greatest width situated at three fourth from anterior. Carapace in ventral view ( Fig. 4B ): ventral margin of RV thicken appearing distinctive wide border with tiny pores along inward edge of border anteriorly and posteriorly; ventral margin at mid-length with expansion.

Carapace in lateral view ( Fig. 4C ) subelliptical, anterior margin rounded, posterior margin narrower rounded, dorsal margin slightly arched, greatest height situated slightly in front of mid-length, ventral margin almost straight, RV overlapping LV anteriorly, ventrally, posteriorly, anterior of RV and LV with c. 12–13 septa; valve surface set with setae and mildly shallow pits.

LV in internal view ( Fig. 4D , 7 E–F): anterior inner lamella wide with straight lines, anterior margin slightly sinuated inwardly, postero-ventral margin without tubercles.

RV in internal view ( Fig. 4E , 7 G–H): anterior inner lamella wide with sinuated inner list, postero-ventral part with denticulated ridge (c. 9–11 denticles).

A1 ( Fig. 5A ): seven-segmented, first segment with one long dorso-subapical seta (reaching to half of next segment) and two long ventro-apical setae. Second segment slightly wider than long, with one short dorso-apical seta (slightly beyond tip of segment). Third segment bearing two setae: one long dorso-apical (reaching tip of penultimate segment) and one short ventro-apical setae (reaching half of next segment). Fourth segment with two long dorsal setae and two short ventral setae (one reaching slightly beyond tip of next segment, the one reaching tip of next segment). Fifth segment dorsally with two long setae, ventrally with two shorter setae (both reaching slightly beyond tip of terminal segment). Penultimate segment with four long apical setae. Terminal segment with three (two long, one shorter) apical setae and long aesthetasc ya, length of aesthetasc ya c. eight times of that of terminal segment.

A2 ( Fig. 5B ): exopodite with three (one long, two short) setae, long one reaching tip of penultimate segment. First endopodal segment with five long (reaching far beyond tips of terminal claws) and one shorter natatory setae reaching beyond tips of terminal segment. Aesthetasc Y long, ventro-apical seta long, extending beyond tip of terminal segment. Penultimate segment undivided, distally with three serrated claws (G1, G2, G3), aesthetasc y2 short (reaching half of terminal segment), z1–z3 setae long; this segment medially with two subequally long dorsal setae, four ventral setae of unequal length (t1–t4). Terminal segment distally with two serrated claws (GM and Gm), length of Gm c. 2/3 of that of GM; and ventral aesthetasc y3, length of aesthetasc y3 c. 3/5 of that of accompanying seta.

Md-palp ( Fig. 5C ): first segment with two large setae, one long and slender seta, and a long, smooth α-seta. Second segment dorsally with three unequal long apical setae, shortest seta reaching to half of terminal segment; ventrally with group of three long hirsute setae, one shorter hirsute seta and plumose, cone-shaped β-seta with pointed tip. Penultimate segment consisting of three groups of setae: dorsally with group of four unequal, long, subapical setae; laterally with apical γ-seta and three further apical setae; ventrally with one long, subapical seta (length c. four times of terminal segment). Terminal segment bearing three claws and two shorter setae.

Mx1 ( Fig. 6A ) with two-segmented palp, basal segment of palp dorsally with group of four long, unequal apical setae and one long subapical seta; ventrally with one long subapical seta (reaching tip of terminal segment). Terminal segment elongated (length c. two times of width), apically with three claws and two setae. Two large bristles on third endite: one slightly serrated distally, another one smooth. Sideways-directed bristles on first endite subequal, length of shorter one c. 3/4 of long one.

T1 ( Fig. 6 B–C): protopodite with two unequally short a-setae, distally with c. 13 hirsute setae of unequal length (10 apical and 3 subapical setae), medially with long d-seta. Endopodite a weakly built palp with one very long, hirsute and two unequally shorter apical setae.

T2 ( Fig. 6D ) with short d1 and long d2 setae, length of d1 seta c. half of d2 seta. Second segment with long eseta (length c. 3/4 of penultimate segment). Penultimate segment divided, proximal segment bearing very long fseta (reaching beyond half of h2 claw), distal segment with short g-seta (reaching tip of segment). Terminal segment with two (one dorsally, one ventrally) short apical h1 and h3 setae (h3 spine-like seta) and very long, serrated claw (h2), being c. twice as long as penultimate segment.

T3 ( Fig. 6E ) a cleaning limb. First segment with long d1, d2, dp setae (d1 shortest seta). Second segment with short apical e-seta (much less than half of next segment). Third segment with medially short f-seta (not reaching tip of segment). Terminal segment with an apical pincer and one short reflexed subapical seta, length of the latter c. 3/ 4 of third segment.

CR ( Fig. 6 F–G) thin, ventral margin smooth. Ga and Gp thin, very long and slightly serrated distally, length of Ga c. 4/5 of that of ramus, length of Gp c. 3/5 of that of Ga; Sa absent, Sp short (c. half of Gp).

Male unknown.

Ecology and distribution. Cypretta triangulata n. sp. has a restricted distribution, as it occurred in only 14 localities (from a total of 293 surveyed localities) and it is thus considered a rare species in Thailand. Its habitats are lakes, swamps, reservoirs, ponds, rivers, springs and rice fields. The microhabitats of the sampled localities were similar to those of C. aculeata n. sp. appearing on the banks of water bodies covered by macrophytes. Several localities of C. triangulata n. sp. were the same as those of C. aculeata n. sp. Cypretta triangulata n. sp. occurs within a pH range of 6.38–9.30, a temperature range of 24.5–31.3° C and a dissolved oxygen range of 2.14–8.25 mg /l.

Figures

FIGURE 4 Cypretta triangulata n. sp. A. Carapace, dorsal view (MSU-ZOC.245). B. Carapace, ventral view (ditto). C. Carapace, left lateral view (MSU-ZOC.244). D. LV, internal view (MSU-ZOC.240). E. RV, internal view (ditto). Scale bar: 200 µm for A–E. Arrow points to anterior end.

FIGURE 5 Cypretta triangulata n. sp. (MSU-ZOC.240). A. A1, B. A2, C. Md-palp, D. Md-coxa. Scale bar: 100 µm for A–B, D, 50 µm for C.

FIGURE 6 Cypretta triangulata n. sp. (MSU-ZOC.240). A. Mx1, B. T1, C. Terminal part of T1 endopodite, D. T2, E. T3, F– G. CR, H. CR-attachment. Scale bar: 50 µm for A–C, 100 µm for D–H.

FIGURE 7 Cypretta aculeata n. sp. (A–D) (MSU-ZOC.235), Cypretta triangulata n. sp. (E-H) (MSU-ZOC.240). A. LV, internal view, posterior part (arrow indicates tubercles). B. LV, internal view, anterior part (arrow indicates sinuated inward margin). C. RV, internal view, anterior part (arrows indicate septa). D. RV, internal view, posterior part (arrows indicate denticulated inner list and complementary sockets). E. LV, internal view, posterior part. F. LV, internal view, anterior part (arrow indicates sinuated margin). G. RV, internal view, anterior part (arrow indicates sinuated inward margin). H. RV, internal view, posterior part (arrow indicates denticulated inner list).