Potamocypris meissneri, Szwarc & Martens & Namiotko, 2021

Szwarc, Agata, Martens, Koen & Namiotko, Tadeusz, 2021, Two new Cypridopsinae Kaufmann, 1900 (Crustacea, Ostracoda) from southern Africa, ZooKeys 1076, pp. 83-107 : 83

Potamocypris meissneri sp. nov.

Figures 2 , 3 , 4

Material examined.

Type locality: South Africa, North-West Province , small temporary open pan (SA-9) near the village of Ganalaagte (Fig. 1 , Suppl. material 1: Fig. 1A ); 26°26'45"S, 25°32'19"E, elevation 1380 m a.s.l.; 1 Apr. 2011; T. Namiotko leg.

Holotype: • 1 ♀ (adult); dissected female stored on a permanent microscopic slide and valves stored dry on a micropalaeontological slide (RBINS INV.159058). Paratypes: South Africa • 2 ♀♀ (adults); same collection data as for holotype (OC-UG 110401-9A2L and OC-UG 110401-9A3L) • 136 ♀♀ (adults), 78 juv.; same collection data as for holotype : 115 ♀♀ and 78 juv. preserved in 96% ethanol; 16 ♀♀ stored as the holotype; 5 ♀♀ stored with carapaces stored on micropalaeontological slides (RBINS INV.159059-INV.159063); repositories: RBINS and OC-UG. Accompanying ostracod fauna: Hemicypris cf. inversa (Daday, 1913); Limnocythere cf. stationis Vávra, 1891.

Etymology.

This species is named after Dr Włodzimierz Meissner, Professor of ornithology at the University of Gdansk, Poland, a long-standing friend of TN who provided unrelenting support in the collection of ostracods from all over the world and who has encouraged and helped TN to join various scientific expeditions for collecting ostracods.

Diagnosis.

Carapace in lateral view somewhat ovoid, broadly rounded dorsally, with both extremities more or less equally rounded, ventral margin weakly concave, and maximum height situated at mid-length. Valves distinctly asymmetrical, with LV overlapping RV anteriorly and posteriorly, RV overlapping LV dorsally and ventrally. Anterior and posterior margins on LV with marginal flange, anterior one larger than posterior one. Carapace external surface hirsute, strongly ornamented with ridges, set with thickly rimmed pores with long sensilla. Antenna with long swimming setae. Terminal segment of maxillula palp spatulate with five claws. T1 with two hirsute branchial rays. CR of whip-like shape with elongated base, fused with distal long flagellum-like seta and set with additional short subapical seta.

Description.

Female. Cp in lateral view (Fig. 2A, B ) with posterior extremity more broadly rounded than anterior one, dorsal margin broadly rounded, ventral margin weakly concave, almost straight. Maximum height situated at mid-length. Valves distinctly asymmetrical, with LV overlapping RV along anterior and posterior margins with flanges (Fig. 2E, G ). Carapace of hirsute appearance with reticulate external surface bearing numerous thickly rimmed normal pores with long sensilla (Fig. 2F ). Cp in dorsal (Fig. 2C ) and ventral view (Fig. 2D ) with posterior extremity slightly rounded, anterior extremity more pointed. Greatest width situated slightly behind mid-length. RV slightly overlapping LV dorsally and ventrally. LV in internal view (Fig. 2H ) subtriangular, with greatest height situated in front of mid-length, posterior part of dorsal margin straight and sloping towards the posterior side; anterior margin rounded, posterior margin almost straight, ventral margin slightly sinuous at mid-length. Anterior and posterior margins with marginal flanges, extending beyond inwardly displayed selvage along anterior and posterior margins, but peripheral along ventral margin (Fig. 2H, J-K ). Flanges particularly expanded in the lower two-thirds of the anterior and posterior margins, with LV overlapping RV (Fig. 2A ). Anterior and posterior calcified inner lamella narrow with one inner list, the latter not reaching halfway posterior margin. RV in internal view (Fig. 2I ) ovoid, with maximum height situated in front of mid-length, anterior margin rounded, posterior margin less so. Anterior calcified inner lamella wide without inner list, but with submarginal peripheral selvage.

A1 (Fig. 3B ) 7-segmented. First segment with one short subapical dorsal seta (not reaching tip of segment) and two long ventral setae. Second segment subquadrate with one short antero-dorsal seta. Rome organ not seen. Third segment ~ 2 × as long as wide, with two setae, one short antero-dorsal (reaching tip of next segment) and one very short antero-ventral seta. Fourth segment with two long antero-dorsal setae and one short antero-ventral seta (reaching 1/3 of next segment). Fifth segment bearing two long antero-dorsal setae and two ventral setae, one long and one of medium length (reaching beyond tip of terminal segment). Penultimate segment with four long apical setae. Terminal segment distally with three (two long and one medium-length) setae and an aesthetasc ya, length of aesthetasc ya ~ 5/6 of that of medium seta.

Chaetotaxic formula: I: A-1s, P-2l / II: A-1s / III: A-1s, P-1s / IV: A-2l, P-1s / V: A-2l, P-1l-1m / VI: A-4l / VII: D: 2l-1m-ya.

A2 (Fig. 3A ) with protopodite, exopodite and 3-segmented endopodite. Basal segment of protopodite with two short ventro-apical setae. Second segment of protopodite with one long apical seta, reaching beyond first endopodal segment. Exopodite reduced to a small plate with three setae, two short and one long, the latter reaching halfway second endopodal segment. Endopodite 3-segmented. First endopodal segment with one long ventro-apical seta, extending beyond tip of terminal segment and one aesthetasc Y of medium length, divided in three parts, distal sensorial part with conspicuously sunken appearance; antero-dorsal with five long natatory setae (reaching tips of terminal claws) and one shorter (6th) seta reaching half of next segment. Second endopodal segment undivided, with two subequal medio-dorsal setae and four medio-ventral setae (t1-t4), two long, one medium and one short; distally with three z-setae, z1 and z3 long, z2 ~ 1/2 the length of z1 and z3, and three long serrated G-claws: G1 thick and apically strongly serrated, G2 and G3 more slender. Terminal endopodal segment subquadrate, with a long serrated claw GM, a shorter (~ 2/3 length of GM) smooth claw Gm and an aesthetasc y3 fused with slightly longer accompanying seta. Aesthetascs y1, y2 and seta g not seen, the latter almost certainly absent as typical of the subfamily.

Chaetotaxic formula: Pr: 1l / Exo: 1l-2s / EI: A-5l-1m, P: Y-1l / EII+III: A-2m, P-1m(t1)-2l(t2,3)-1s(t4), D-2l(z1,z3)-1m(z2)-3l(G1,2,3: ser) / EIV: 1l(GM: ser)-1m(Gm)-y3-1m

Md with sclerotised coxa (Fig. 3D ) and 4-segmented palp (Fig. 3C ). First palp-segment ventro-apically with two long plumed setae (S1 and S2), one long slender and smooth seta and a short but stout, smooth α-seta. Second segment antero-dorsally with two long slender and smooth setae and one thick plumed seta; ventrally with three unequally long smooth setae, one long hirsute seta and a stout and hirsute β-seta. Third segment antero-ventrally with one long hirsute seta and one short smooth seta; medio-dorsally with four setae, two reaching tip of terminal segment, and two longer setae, one of these smooth γ-seta; antero-dorsally with four setae reaching beyond tips of terminal segment. Terminal segment with four claws, two ~ 3 × as long as length of terminal segment, one of these serrated, and two shorter claws. Md coxa typically elongated, distally with rows of teeth and small setae, and with one short smooth seta situated near the insertion place of the palp.

Chaetotaxic formula: Palp: I: In-1s(alfa)-1l-2l(S1,S2: pl) / II: In-1s(beta: pl)-1l(pl)-2m-1l, Ex:1l(pl)-2l / III: In-1l(pl)-1s, D-3m-1m(gamma), Ex-4m / IV: 2m-1l-1l(ser)

Mx1 (Fig. 4B ) with three endites (with chaetotaxy incompletely illustrated), a 2-segmented palp and a large respiratory plate (not illustrated). Third endite with two smooth teeth bristles (Zahnborsten). First palp-segment dorso-apically with four unequal setae; medio-dorsally with one long, subapical seta, reaching beyond tip of terminal segment. Second palp-segment spatulate, apically with four stout claws (~ 1.5 × as long as terminal segment) and one shorter claw (~ 1/2 length of others).

Chaetotaxic formula: Palp: I: Ex-3s-1l, In-1m / II: D-5s

T1 (Fig. 4D ). Protopodite with two short a-setae; b-, c-, and d-setae absent, endite distally with a dozen apical setae (exact number not determined). Endopod elongated, apically with one long seta (h2) and two shorter setae (h1 and h3) of differing lengths. Respiratory plate with two hirsute rays.

Chaetotaxic formula: Pr: A-2s(a and a’) / Mastic: D-? / Exo: 2m(pl) / E: D-3l

T2 (Fig. 4A ) a walking limb. Protopodite with seta d2 of medium length, seta d1 absent. First three endopodal segments each with one ventro-apical seta. Setae e and f reaching tip of the next segment, seta g ~ 3 × as long as terminal segment. Fourth segment with one short seta (h3), one medium seta of length (h1) and a long claw, distally serrated (h2), the latter ~ 3 × as long as the second endopodal segment.

Chaetotaxic formula: Pr: A-1s(d2) / EI: A-1m / EII: A-1m / EIII: A-1m / EIV: P-1s(h3), D-1m(h1)-1l(h2 G:ser)

T3 (Fig. 4E ) a cleaning limb. First segment with two long apical setae (dp and d2) and one shorter medio-ventral seta (d1). Second segment fused with third segment, with e-seta of medium length, and with f-seta reaching tip of segment. Distal part of limb consisting of a pincer-organ (fusion between tip of third segment and fourth segment), bearing a seta (h3) of medium length and a short, serrated seta (h2); h3 ~ 2/3 of the length of penultimate segment, h2 ~ 1/3 of length of h3.

Chaetotaxic formula: Pr: A-1l(d2)-1m(d1), P-1l(dp) / EI: A-1m(e) / EII + III: A-1s(f) / EIV: 1s(h2: ser)-1m(h3)

CR (Fig. 4C ). Reduced to a whip-like structure, with elongated base fused with long flagellum-like seta and bearing a short subapical seta.

Remark.

It should be noted that juveniles of this species do not have tubercles on the valves (see discussion).

Measurements (in μm). Cp (n = 4): L = 512-526, H = 305-306; LV (n = 11): L = 510-530, H = 278-298; RV (n = 11): L = 498-517, H = 301-319.

Male unknown.

Ecology.

Potamocypis meissneri was collected only from the type locality in the North-West Province of South Africa. This is an open temporary pan with the following physical and chemical water properties: pH = 7.0, electrical conductivity = 36 µS /cm and water temperature 25.8°C.

Key to southern African Potamocypris species (partly based on Martens 2001):

1	Natatory setae of A2 short (not reaching tips of terminal claws	P. paludum Gauthier, 1939
-	Natatory setae of A2 long	2
2	Cp elongated (L ≥ 2 × H), crescent-shaped	P. mastigophora (Methuen, 1910)
-	Cp compressed (L <2 × H), differently shaped, not crescent-shaped	3
3	Cp subtriangular, dorsally arched with blunt angle	P. gibbula (Sars, 1924)
-	Cp with dorsal margin broadly rounded or straight on a long distance and sloping down to the posterior	4
4	Cp with posterior margin rounded; maximum height at mid-length	P. meissneri sp. nov.
-	Cp with posterior margin straight; maximum height in front of mid-length	5
5	RV with wide dorsal overlap of LV	P. deflexa (Sars, 1924)
-	Dorsal overlap of RV minute or lacking	P. humilis (Sars, 1924)

Figures

Figure 1. Localities of Potamocypris meissneri sp. nov. (purple star SA- 9) in the North-West Province of South Africa and Sarscypridopsis harundineti sp. nov. (red dots SA- 96 to SA- 103) in the outskirts south of the Okavango Delta in Botswana. The type locality of Sarscypridopsis harundineti sp. nov. (SA- 103) is marked with a dark red dot.

Figure 2. Carapace and valves of Potamocypris meissneri sp. nov. ♀ A RBINS INV. 159060 B RBINS INV. 159062 C RBINS INV. 159061 D RBINS INV. 159063 E-G RBINS INV. 159060 H-K RBINS INV. 159059. A carapace right view B carapace left view C carapace dorsal view D carapace ventral view E carapace right view of posterior end, detail of A F detail of external surface of A G carapace right view of anterior end, detail of A H left valve internal view I right valve internal view J left valve internal view of posterior part, detail of H K left valve internal view of anterior part, detail of H. Scale bars: 400 μm (A-D, H, I); 200 μm (E, G, J, K); 50 μm (F); arrows indicate anterior end.

Figure 3. Limbs of Potamocypris meissneri sp. nov. ♀. Holotype (OC-UG 110401 - 9 A 1 L) A second antenna B first antenna C mandibular palp D mandibular coxa. Scale bars: 100 μm. Abbreviation: ns = natatory setae.

Figure 4. Limbs of Potamocypris meissneri sp. nov. ♀ A, B, C holotype (OC-UG 110401 - 9 A 1 L) D paratype (OC-UG 110401 - 9 A 3 L) E paratype (OC-UG 110401 - 9 A 2 L) A second thoracopod (walking leg) B maxillula C caudal ramus D first thoracopod (maxilliped) E third thoracopod (cleaning leg). Scale bars: 100 μm.