Potamocypris variegata ( Brady & Norman, 1889 )

Peng, Ping, Zhai, Dayou, Smith, Robin J., Wang, Qianwei, Guo, Yun & Zhu, Liping, 2021, On some modern Ostracoda (Crustacea) from the Tibetan Plateau in SW China with descriptions of three new species, Zootaxa 4942 (4), pp. 501-542 : 518-520

Potamocypris variegata ( Brady & Norman, 1889)

( Figs 16 , 17 )

Cypridopsis variegata Brady & Norman, 1889

Material examined. One dissected female ( WOC 57) ( Table 1 ).

Dimensions. Female ( LV, n = 1) length 0.60 mm, height 0.35 mm, H/L ratio 0.58.

Description of female. Carapace ( Fig. 16 ) sub-triangle in lateral view. Dorsal margin strongly arched with highest point near mid-length. Anterior margin broadly rounded with maximum curvature at antero-ventral area. Postero-dorsal angle prominent with central posterior margin slightly curved and running down to tightly curved postero-ventral margin. Ventral margin concave. Valve surface densely pitted and covered with fine setae; pits slightly smaller towards periphery of valves compared with central area. In interior view, selvage displaced inwards. Anterior inner list running along medial part of calcified inner lamella. Posterior inner list situated very close to inner margin of calcified inner lamella.

A1 ( Fig. 17A ) with eight segments. First two segments fused into elongate base, supporting one short dorsal seta and two long ventral setae. Third segment sub-trapezoidal, with one short dorsal seta. Fourth segment slightly elongate, with one dorso-apical seta extending well beyond end of fifth segment, and one tiny ventro-apical seta not reaching to end of fifth segment. Fifth segment stout, with two unequal dorso-apical setae, and two very short, unequal ventro-apical setae. Sixth segment slightly elongate, with two very long, dorso-apical setae of sub-equal length, and two ventro-apical setae of different lengths, one of which claw-like. Seventh segment with four apical setae reaching tips of longest apical seta of sixth segment. Seta α not observed. Eighth segment slender, with slender aesthetasc y a, about twice as long as eighth segment, ventro-apical seta, slightly longer than y a, and two medial, much longer setae.

A2 ( Fig. 17B ) basal segment with one slender latero-posterior seta and two unequal ventro-apical setae. Second segment with one long ventro-apical seta. Longest exopodal seta with very fine distal part, reaching mid-length of penultimate segment or beyond. Aesthetasc Y situated proximal to mid-point of first endopodal segment, slender, 2- or 3-segmented, reaching beyond mid-length of segment. Natatory setae extending beyond terminal claws with ca. half of length. Sixth seta reaching to about end of terminal segment. Ventro-apical seta of this segment reaching to about tip of aesthetasc y3. Penultimate segment with two medio-dorsal setae of slightly unequal length. t-setae unequal in length, with t2 and t3 longest, extending beyond terminal segment with more than half length. Aesthetasc y1 situated proximally of t setae, extending slightly beyond penultimate segment. z-setae unequal, with z3 longest and z2 shortest. G claws serrated. G1 longest claw, G2 most robust and most serrated. GM slender and finely serrated at distal part, only slightly longer than G2. Gm 3/5 length of GM. Aesthetasc part of y3 extending slightly beyond mid-length of Gm .

Md palp ( Fig. 17C ) 4-segmented. S1 and S2 robust, covered with long pseudochaetae. Accompanying seta slender and smooth. Seta α not observed. Setal group of second segment with three sub-equally long, slightly plumose setae extending to about mid-length of terminal claws. Accompanying seta shorter, plumose. Seta β short, stout, plumose. Second segment with three slender antero-apical setae one of which plumose. Third segment with about nine apical setae: Four antero-apical, slender, smooth, unequally long setae, one latero-exterior, plumose seta extending beyond mid-length of terminal claws, two slender, smooth latero-interior setae, and about two slender, smooth postero-apical setae. Fine pseudochaetae present at antero-medial part of penultimate segment. Terminal segment with two long, robust claws, one shorter, robust claw, and one short, slender seta. Vibratory plate with two tiny setae and four long rays.

First segment of Mx palp ( Fig. 17D ) with one short latero-interior seta and five anterior setae. Second segment of Mx palp spatulate, with four claws. Two largest tooth bristles of third endite lobe slightly unequal in length and smooth.

Setae a of L5 ( Fig. 17E ) protopod tiny. Setae b, c, and d absent. Palp poorly sclerotized, with very long h2 and unequally long h1 and h3. Vibratory plate with two unequal setae.

L6 ( Fig. 17F ) with four endopodal segments. Seta d1 absent. Seta d2 well developed. Setae e, f, g, and h1 subequally long. Claw h2 robust, serrated. Seta h3 tiny.

L7 ( Fig. 17G ) with three segments. Seta d1 slightly shorter than d2. Seta dp comparatively short, only slightly longer than d2. Seta e short, not extending to mid-length of terminal segment. Seta f very short. Pincer organ small. Seta h3 slightly S-shaped.

Ur ( Fig. 17H ) with slightly swollen base, carrying long flagelliform structure and short sub-apical seta.

Remarks. The one specimen of this species recovered during this study is tentatively assigned to the species Potamocypris variegata based on the following characters: pitted carapace, long swimming setae, four setae on the terminal segment of the maxillula palp, and two rays on the maxillula branchial plate ( Fig. 17 ). The LV is noticeably more elongate (height / length = 0.56) compared to some other figured specimens of P. variegata (height / length = 0.64, Meisch 1985; 0.60, Fuhrmann 2012), and is similar to Potamocypris smaragdina ( Vávra, 1891) . However, P. smaragdina has only one ray on the maxillula branchial plate ( Meisch 1985). Potamocypris variegata has been previously reported from North America and western parts of Eurasia, including western Russia and Iran (see review in Meisch 1985; 2000). The records of this species from Tibet in this study and those from Beijing ( Zhai et al. 2017, specimens not illustrated) are therefore much further east than previous records. The solitary specimen herein was collected from a small, turbid pond at an altitude of 3075 m.

Figures

FIGURE 16. Potamocypris variegata (Brady & Norman, 1889), female (WOC57). (A) LV, exterior view; (B) LV, interior view (with a piece of RV fragment). Scale bar = 200 μm.

FIGURE 17. Potamocypris variegata (Brady & Norman, 1889), female (WOC57). (A) right A1, exterior view; (B) right A2, exterior view; (C) right Md palp, interior view; (D) left Mx, interior view (exopod not shown); (E) right L5, exterior view; (F) right L6, interior view; (G) right L7, interior view; (H) Ur. Note that the vibratory plate of L5 (panel E) has been deformed so that it is difficult to discern, and that the two setae changed their direction after dissection.