Cypricercus tiao, Almeida & Ferreira & Higuti & Martens, 2021

Almeida, Nadiny Martins De, Ferreira, Vitor Góis, Higuti, Janet & Martens, Koen, 2021, On two new species of Cypricercus Sars, 1895 (Crustacea, Ostracoda) from Brazil with a discussion on the taxonomy of the genus, Zootaxa 4938 (5), pp. 501-536 : 523-527

Cypricercus tiao sp. nov.

( Figs. 1 , 15–17 )

2017 Strandesia sp. 3 n. sp.—Higuti et al.: 7, table 2.

Diagnosis. Cp elongated (length c. twice the height), with greatest height situated slightly in front of the middle. Posterior spine absent from both valves. Anterior margin with an outer list prominent in both valves, giving the front in dorsal and ventral views a lip-like appearance. A2 with natatory setae reaching tips of end claws. CR slender, its attachment with Triebel’s loop in the main branch.

Type locality. Pombas Lake ( PAR 1394 ), in Eichhornia azurea . Coordinates: 22° 47’ 59.5” S, 53° 21’ 36.8” W .

Type material. Holotype: A female, with soft parts dissected in glycerine in a sealed slide and with valves stored dry in a micropalaeontogical slide ( MZUSP 41546 ).

Paratypes: Three females dissected and stored as the holotype ( MZUSP 41547 , MZUSP 41548 , MZUSP 41549 ) . Three female carapaces stored dry in micropalaeontogical slides ( MZUSP 41550 , MZUSP 41551 , MZUSP 41552 ) .

Etymology. The present species is named after Sebasti„o (Ti„o) Rodrigues (Nupélia, Universidade Estadual de Maringá, Porto Rico, Brazil), in recognition of his vast knowledge of the ever-changing biotopes of the Upper Paraná River floodplain, and his continued technical assistance in the collections of ostracods, especially in the river-floodplain system of the Upper Paraná River.

Measurements of illustrated specimens. See Table 1.

Description of female. Valves ( Figs. 15A, B ) elongated, with greatest height situated slightly in front of the middle. Both valves with anterior calcified inner lamellae wider than posterior ones; inner margins evenly rounded. LVi ( Fig. 15A, C, D ) with an inner groove running parallel to the ventral, anterior and posterior valve margins ( Fig. 15A ) disappearing in the dorsal side ( Fig. 15C ). RVi ( Fig. 15B, E, F ) without an inner groove running parallel to the ventral margins, with posterior margin ( Fig. 15F ) without a prominent spine. CpRl ( Fig. 15G ) LV slightly overlapping RV along the ventral margin; surface smooth with few setae, some emerging from rimmed pores ( Fig. 15J ). CpD ( Fig. 15H ) and CpV ( Fig. 15I ) with greatest width (about half of the length) situated slightly in front of the middle; both anterior margins with a prominent outer list in both valves, giving the front in dorsal and ventral views a lip-like appearance. CpF ( Fig. 15K ) only slightly skewed, with RV positioned somewhat higher than LV.

A1 ( Fig. 16A ) with seven segments. First segment large, dorsally with one short subapical seta and ventrally with two long apical setae (c. 4 times the length of the short one); Wouters’ organ not seen. Second segment subquadrate, wider than long, with one short dorso-apical seta (c. the length of the second segment). Rome organ not seen. Third segment about three times longer than wide, with two short apical setae. Fourth segment with two long dorso-apical setae and two short ventro-apical setae. Fifth segment with three long and one short setae (reaching beyond tip of terminal segment). Sixth segment with four long apical setae. Terminal segment with one short aesthetasc ya, two long apical setae and one short seta, slightly shorter than ya.

A2 ( Fig. 16B, C ) with protopodite, exopodite and three-segmented endopodite. Protopodite with three ventral setae (two short and one long and hirsute, reaching beyond the middle of third segment); exopodite reduced to a small plate, with two short and one long setae. First endopodal segment with one ventral aesthetasc Y, one long ventro-apical seta (reaching beyond the middle of second endopodal segment) and five long, hirsute, natatory setae, just reaching tips of the apical claws and one short accompanying seta with length about 1/3 of the second endopodal segment. Second endopodal segment undivided, dorsally with one long and one short smooth seta, ventrally with four t-setae (two long setae, one seta with intermediate length and one short smooth seta); apically with three claws (G1, G2, G3), three setae (z1, z2, z3) and one short aesthetasc y2. Terminal segment ( Fig. 16C ) with two claws (one long GM, one short Gm), aesthetasc y3 fused with accompanying seta over short distance only and a fine g-seta (the latter shorter than aesthetasc y3).

Md-palp ( Fig. 17 A—chaetotaxy incomplete in this drawing) with four segments. First segment with two long and plumose (“s”-) setae, one long and smooth seta and one smooth and long α-seta (reaching beyond tip of third segment). Second segment dorsally with one group of three apical setae, two long and one short (about half the length of the long); ventrally with one long but narrow hirsute β-seta, three hirsute setae (unequal but long) and one short hirsute seta. Penultimate segment with three groups of setae, dorsally with four setae (unequally long and smooth), laterally with hirsute and stout γ-seta, three subapical smooth setae, ventrally with one long and one short (reaching beyond middle of terminal segment). Terminal segment apically with three claws and three setae.

Md-coxa (not illustrated) elongated with a series of five strong teeth, interspaced with short setae; dorsally with one subapical seta.

Mx1 ( Fig. 16D ) with a basal (basipodite) part carrying a large branchial plate, three endites, and a two-segmented palp. Branchial plate (not illustrated) elongated, with c. 16 respiratory rays, some quite short, others long, proximally with a group of five unequal setae. Palp with first segment carrying six long (but unequal) apical setae, and one short subapical and hirsute seta. Terminal palp segment c. 1.5 times as long as basal width, tapering, distally with three claws and three setae. Third endite with two large apical tooth-bristles, apically serrated, and one long sub-basal seta (reaching tip of second endite). First endite with two large but unequal sideways-directed bristles and two basal setae, also of unequal length.

T1 ( Fig. 17B ) protopodite apically with a group of 14 hirsute setae; two hirsute, unequal but short a-setae; one long hirsute b-seta and one long hirsute d-seta (these setae subequal). Endopodite (not illustrated) carrying three plumose setae, two long but unequal and one short, the latter about 1/3 of the longer ones.

T2 ( Fig. 17F ) with six segments. First segment with one long and hirsute seta d1. Second segment with one short and hirsute seta d2 (the latter c. 2/3 of the length of seta d1). Third segment with one subapical hirsute seta (e). Fourth segment with one long hirsute apical seta (f), reaching beyond tip of terminal segment. Fifth segment with one short apical hirsute seta (g), about 1/3 of length of f seta. Terminal segment with one apical claw (h2), one subapical seta (h1) and one apical seta (h3).

T3 ( Fig. 17 E—chaetotaxy not completely shown) with three segments. First segment with three long and hirsute setae (d1 inserted in the middle of the segment, setae d2 and dp inserted apically). Second segment longer than wide, with one apical hirsute seta (e), reaching middle of third segment. Third segment longer than wide, with one medially inserted hirsute seta (f), half of length of seta (e). Distal part of the third segment ( Fig. 17E ) with a pincer structure, a long hirsute seta h3, one spine-like seta h1 and one broad seta h2, about 2/3 of the length of seta h3.

CR ( Fig. 17D ) slender, curved, with ventral margin serrated. Apically with two serrated claws (one longer, and one short, the latter about 2/3 the length of the longest) and two hirsute setae (one longer distal seta, approximately 2/3 of length of longest claw, and one short proximal seta, about 2/5 of length of longer seta).

CR attachment ( Fig. 17C ) slim, with Triebel’s loop situated in the dorsal branch. vb short; db longer and curved.

Male unknown.

Differential diagnosis. We here compare Cypricercus tiao sp. nov. to the other five species in the genus without posterior spines (see discussion and Table 3 ). The type species to the genus, C. cuneatus , was re-described by Savatenalinton & Martens (2009b) using type material, and several apparent differences with the present new species exist. In C. cuneatus , the posterior margin of both valves is pointed (more rounded in C. tiao sp. nov.); the anterior LV/RV overlap is also much larger in C. cuneatus and in frontal, dorsal and ventral views, the anterior valve margins show more extensive lip-like expansions in the new species. The anterior list in the LV in C. cuneatus is also more inwardly displaced

Also Cypricercus inermis ( Brady, 1904) was extensively re-described by Savatenalinton & Martens (2009b) based on type materials and it turned out that the valves of these type specimens are more elongated than illustrated in the original description. This aspect also distinguishes this species from C. tiao sp. nov. Cypricercus maculatus G. W. M̹ller, 1908 is less elongated, wider in dorsal view and with a more pronounced anterior LV/RV overlap. Farkas (1957) described two species of Cypricercus without posterior spines from India: Cypricercus setosus Farkas, 1957 with an unusually high and short Cp, and Cypricercus vietsi Farkas, 1957 in which the posterior margins of the valves are much more broadly rounded than in C. tiao sp. nov.

Ecology and Distribution. Cypricercus tiao sp. nov. was recorded only in a single lake of the Upper Paraná River floodplain, associated with the root systems of Eichhornia azurea . Water temperature at the time of collecting was 18.8°C; pH was 7.2; electrical conductivity was 59.2 µS. cm-1 and dissolved oxygen was 2.9 mg. L- 1. (see Table 2 ).

Figures

FIGURE 1. Map of Brazil, indicating areas where Cypricercus centrurus, Cypricercus alfredo sp. nov. (asexual and sexual populations) and Cypricercus tiao sp. nov. were found.

FIGURE 15. Cypricercus tiao sp. nov. Upper Paraná River floodplain. A–K. Female. A, C, D: arrows pointing to the inner groove. A. LVi (MZUSP 41546). B. RVi (MZUSP 41546). C. LVi, detail of posterior part (MZUSP 41546). D. LVi, detail of anterior part (MZUSP 41546). E. RVi, detail of anterior part (MZUSP 41546). F. RVi, detail of posterior part (MZUSP 41546). G. CpRl (MZUSP 41550). H. CpD (MZUSP 41551). I. CpV (MZUSP 41552). J. CpRl, detail of carapace surface (MZUSP 41550). K. CpFr (MZUSP 41552). Scale bars: A–B, G–I, K: 1000 µm. C–F: 500 µm. J: 50 µm.

FIGURE 16. Cypricercus tiao sp. nov. Upper Paraná River floodplain. A–D: Female. A. A1 (MZUSP 41549). B. A2, without terminal segment (MZUSP 41546). C. A2, terminal segment (MZUSP 41546). D. Mx1 (MZUSP 41547). Scale bars: 50 µm.

FIGURE 17. Cypricercus tiao sp. nov. Upper Paraná River floodplain.A–F: Female. A. Md-palp showing α, β, γ setae (MZUSP 41547). B. T1 (MZUSP 41546). C. CR attachment (MZUSP 41546). D. CR (MZUSP 41546). E. T3 (MZUSP 41547), apical pincer. F. T2 (MZUSP 41547). Scale bars: 50 µm.