Dentocypria aequiloba, Savatenalinton, Sukonthip, 2017

Savatenalinton, Sukonthip, 2017, A new genus and four new species of subfamily Cyclocypridinae (Crustacea, Ostracoda) from Thailand, Zootaxa 4243 (2), pp. 329-365 : 350-356

Dentocypria aequiloba n. gen. n. sp.

( Figs 15–18 )

2016 Physocypria sp. 1—Savatenalinton & Suttajit: 11, Table 2.

Holotype. Male, soft parts dissected in glycerine on a sealed slide, valves stored dry in a micropalaeontological slide (MSU-ZOC.181).

Allotype. Female, stored like the holotype (MSU-ZOC.182).

Paratypes. One dissected male (MSU-ZOC.183) stored like the holotype, two undissected males (MSU- ZOC.184–185) stored dry in micropalaeontological slides, two dissected females (MSU-ZOC.186–187) stored like the holotype, two undissected females (MSU-ZOC.188–189) stored dry in a micropalaeontological slide and c. 25 males and 35 females in 70% ethanol.

Repository. All specimens are deposited in the MSU-ZOC.

Type locality. Roadside canal, Phichit Province. For details on the locality see description of D. chantaranothaii n. gen. n. sp.

Other localities. Ricefield, Chaiyaphum Province. Material collected on 28 Sep. 2005, coordinates: 16° 23΄ 03˝ N and 101° 58΄ 47˝ E. Accompanying ostracod fauna: Cypris subglobosa Sowerby, 1840 , Hemicypris mizunoi Okubo, 1990 , Cypridopsine sp., Candonopsis sp., Ilyocypris sp., Notodromas fasciata ( O.F. Müller, 1776) , Strandesia sp. (juveniles).

Etymology. The species is named after the appearance of the a- and b-lobes of the hemipenis, which are almost equal in length.

Diagnosis. Carapace in lateral view subovate, dorsal margin strongly arched, valve surface smooth. CpD subovate with greatest width situated at c. two third of length. Male A2 with transformed t2 and t3 setae and reaching tip of terminal segment. CR: length of Gp c. 4/5 of that of Ga, Sa short (less than half of that of Ga), Sp very long (reaching beyond tip of ramus). Right prehensile palp of male T1 with large distal protrusion on first segment. Hemipenis with a-lobe slightly longer than b-lobes, a-lobe elongated, b-lobe subtriangular with pointed and distinctively dorsally curved end.

Differential diagnosis. The main diagnostic features of Dentocypria aequiloba n. gen. n. sp. are the relatively round and smooth carapace, the subovate shape of the carapace in dorsal view, the short G1 claw of female A2 and the subequal length of a- and b-lobes of the hemipenis.

Measurements (mean, in µm). Female, LV (n = 2), L = 400, H = 265; RV (n = 2), L = 388, H = 265; Carapace (n = 2), L = 388, H = 253, W = 218. Male, LV (n = 2), L = 347, H = 224; RV (n = 2), L = 335, H = 224; Carapace (n = 2), L = 356, H = 212, W = 185.

Description of female. Carapace subovate in lateral view ( Fig. 15 A), anterior margin rounded, slightly narrower rounded than posterior margin, LV overlapping RV anteriorly, ventrally and posteriorly, dorsal margin strongly arched, greatest high situated at mid-length, valve surface smooth.

CpD ( Fig. 15 B) subovate, with greatest width situated at c. two third of length.

LVi ( Fig. 15 C) with selvage slightly inwardly displaced along anterior margin, internal tooth on antero-ventral part and tubercle-sockets anteriorly and posteriorly, calcified inner lamella anteriorly wider than posteriorly (also see male specimen, Fig. 15 G), with one weak inner list anteriorly.

RVi ( Fig. 15 D) with submarginal selvage anteriorly, complementary pit of internal tooth on antero-ventral part, valve margin tuberculated anteriorly and posteriorly, posterior tubercles more prominent than anterior ones, calcified inner lamella anteriorly wider than posteriorly, with one inner list anteriorly.

A1 ( Fig. 16 A): first segment with proximal Wouters organ, one long dorso-subapical seta (reaching beyond tip of segment) and two long ventro-apical setae. Second segment slightly wider than long, with one long dorso-apical seta (reaching beyond mid-length of next segment) and large Rome organ. Third segment bearing two (dorsoapical and ventro-apical) setae, shorter seta not reaching tip of fourth segment. Fourth segment with two long dorsal setae and two subequal ventral setae, short one reaching tip of fifth segment. Fifth segment dorsally with two long setae, ventrally with two (one long, one shorter) setae, short one reaching tip of terminal segment. Penultimate segment with four long apical setae. Terminal segment with three (two long, one short) apical setae and aesthetasc y a, length of latter c. 2/3 of that of short apical seta.

A2 ( Fig. 16 B): exopodite with three (one long, two short) setae, long one reaching beyond tip of first endopodal segment. First endopodal segment with five long (reaching tip of terminal claws) and one short natatory setae, length of shortest seta less 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 (G1, G2, G3), G2 short (length c. half of that of G1), aesthetasc y2 very long (reaching tip of terminal segment), z1 seta short, z2–z3 setae long; this segment medially with two unequally long dorsal setae (long one reaching beyond tip of segment), four ventral setae (t1–t4) of unequal length, and ventral aesthetasc y1, latter long (reaching tip of segment). Terminal segment distally with two serrated claws (GM and Gm), length of Gm c. 3/4 of that of GM; medially with ventral aesthetasc y3, length of aesthetasc y3 c. half of that of accompanying seta.

Md-palp ( Fig. 16 C) as in D. mesquitai n. gen. n. sp. with few differences: apical γ-seta long (reaching tip of terminal segment), terminal segment very elongated (length c. 3 times its width) bearing two claws, one long seta and one short seta.

Mx1 ( Fig. 17 A) as in D. mesquitai n. gen. n. sp. with few differences, e.g. sideways-directed bristles on first endite unequally long, length of long one c. 2.5 times of that of short one.

T1 ( Fig. 17 B) as in D. mesquitai n. gen. n. sp. with different setae lengths.

T2 ( Fig. 17 C) as in D. mesquitai n. gen. n. sp. with few differences, e.g. h3 seta of terminal segment long (not spine-like) and length of h2 almost same of that of penultimate segment.

T3 ( Fig. 17 D) as in D. mesquitai n. gen. n. sp. with few differences, e.g. first segment with long d1, d2, dp setae, length of d1 c. 2/3 of that of d2 seta. Second segment with long apical e-seta (not reaching half of third segment).

CR ( Fig. 18 A) as in D. mesquitai n. gen. n. sp. with few differences, e.g. length of Gp c. 4/5 of that of Ga, Sp very long (reaching beyond tip of ramus).

CR attachment ( Fig. 18 B) as in D. mesquitai n. gen. n. sp.

Description of male. Carapace and valves ( Fig. 15 E–H) as in female, but somewhat smaller. All limbs as in female, except for terminal two segments of A2 ( Fig. 18 C) and T1 ( Fig. 18 D–E).

A2 with divided penultimate segment, transformed t2 and t3 setae subequally long, t2 longer than t3 and reaching tip of terminal segment. Setae z1 and z2 of penultimate segment transformed into claws; claw G1 reduced, appearing smaller and shorter; claw G3 reduced to seta (reaching far beyond tip of terminal segment); Gm on terminal segment of A2 reduced, appearing smaller and shorter (length more than half of that of GM).

T1 with asymmetrical prehensile palps (endopodites). First segment of right prehensile palp ( Fig. 18 D) with large distal subtriangular protrusion and bearing one short apical spine; second segment large, subtriangular. Left prehensile palp ( Fig. 18 E) elongated with first segment bearing two long apical spines; second segment narrow, curved and pointed.

Hemipenis ( Fig. 18 F): a-lobe and b-lobe subequally long, a-lobe elongated, b-lobe subtriangular with pointed and distinctively dorsally curved tip.

Zenker organ ( Fig. 14 E) elongated, length c. 2.6 times width, set with seven chitinous spiny whorls.

Remarks. Dentocypria aequiloba n. gen. n. sp. resembles Physocypria nipponica Okubo, 1990 . Apart from the internal tooth of LV, other differences between these two species can be found, for example, in the carapace shape in dorsal and lateral views. In the new species, the carapace is more ovate in dorsal view, the greatest width is situated at c. two-thirds of the length (it is at mid-length in P. nipponica ) and the carapace in lateral view is more elongated. Additionally, a- and b-lobes of the hemipenis are subequal in length in the new species whereas the alobe is longer than the b-lobe in P. nipponica .

Figures

FIGURE 14. Dentocypria smithi n. gen. n. sp., male (MSU. ZOC. 168). A. A 2. B. right prehensile palp. C. left prehensile palp. D. hemipenis. E. Zenker organ. Scale bar: A = 40 µm; B – D = 46 µm; E = 100 µm.

FIGURE 15. Dentocypria aequiloba n. gen. n. sp., female (A – D), male (E – H). A. CpR (MSU. ZOC. 188). B. CpD (MSU. ZOC. 189). C. LVi (MSU. ZOC. 186). D. RVi (MSU. ZOC. 186). E. CpR (MSU. ZOC. 184). F. CpD (MSU. ZOC. 185). G. LVi (MSU. ZOC. 183). H. RVi (MSU. ZOC. 183). Scale bar: A – H = 100 µm.

FIGURE 16. Dentocypria aequiloba n. gen. n. sp., female (MSU. ZOC. 182). A. A 1. B. A 2. C. Md-palp. D. Md-coxa. Scale bar: A – B = 50 µm; C – D = 40 µm.

FIGURE 17. Dentocypria aequiloba n. gen. n. sp., female (MSU. ZOC. 182). A. Mx 1. B. T 1. C. T 2. D. T 3. Scale bar: A – B = 34 µm; C = 50 µm; D = 40 µm.

FIGURE 18. Dentocypria aequiloba n. gen. n. sp., female (A – B, MSU. ZOC. 182), male (C – G, MSU. ZOC. 181). A. CR. B. CR attachment. C. A 2, D. right prehensile palp. E. left prehensile palp. F. hemipenis. G. Zenker organ. Scale bar: A = 47 µm; B = 40 µm; C = 35 µm; D – F = 40 µm; G = 100 µm.