Cypris pubera O.F. Müller, 1776

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 : 514-518

Cypris pubera O.F. Müller, 1776

( Figs 13–15 )

For an abbreviated synonym list see Meisch et al. (2019), but also see below.

Material examined. Two dissected females ( WOC 9, WOC10) ( Table 1 ).

Dimensions. Female (LV, n = 2) length 2.30–2.50 mm, H/L ratio 0.54–0.57.

Description of female. Shell ( Fig. 13 ) sub-triangular in lateral view. Dorsal margin strongly arched, with greatest height slightly in front of mid-length. Postero-dorsal margin bluntly angular. Anterior margin broadly rounded. Posterior margin narrowly rounded. Ventral margin weakly sinuous with small expansion at mouth area. Small spines (or denticles) present near anterior and posterior margins. Longer spine situated at postero-ventral part of RV. Shell surface strongly pitted and densely covered with small setae, with small number of tiny bumps on both anterior and posterior areas. Structure of marginal zone asymmetric in interior view. In RV, selvage significantly displaced inward along anterior, postero-ventral, and most part of ventral margins, with valve margin defined by flange. Inner list present but only easily recognised at postero-ventral part of shell. In LV, selvage only slightly displaced inward at anterior and postero-dorsal margins and being peripheral along rest of free margin. Inner list well developed and running close to inner margin. Carapace inflated in dorsal view, with greatest width slightly behind mid-length.

A1 ( Fig. 14A, B ) with eight segments, first two of which fused forming large base, carrying one short dorsal seta and two intermediately long ventral setae. Third segment short, with one short dorso-apical seta. RO stemmed from lobe-like structure on extero-ventral surface of third segment, very small compared with segment, distally with slightly enlarged opening. Fourth segment elongate, with one dorso-apical seta extending beyond next segment, and one short, plumose seta extending to about end of next segment. Fifth segment sub-quadrate, with two very long, plumose setae extending far beyond terminal segment with up to 80% of total length, and two unequally long ventral setae, one of which plumose, extending to end of sixth segment, other one smooth, extending to end of terminal segment. Sixth segment slightly elongate, with three very long, plumose setae and one intermediately long, smooth seta. Seventh segment elongate, with four very long, plumose setae and very short, sinuous seta α. Eighth segment slender, with three apical setae and aesthetasc y a, latter of which about twice as long as terminal segment. Ventral seta shorter than y a, not claw-like. Two medial setae very long.

A2 ( Fig. 14C, D ) basal segment with one postero-lateral seta and two unequally long ventral setae. Second segment robust, with one ventro-apical seta extending to or beyond middle of penultimate segment. Longest exopodal seta extending beyond mid-length of third segment (first endopodal segment), plumose along distal half. Other two exopodal setae progressively shorter. Aesthetasc Y short, situated behind mid-length of third segment. Third segment with one plumose ventro-apical seta extending to basal part of terminal segment. Swimming setae with long pseudochaetae, and extending slightly beyond tip of claws. Sixth seta only extending to 1/3 length of penultimate segment from proximal part. Third segment also with well-developed pseudochaetae on both dorsal and ventral areas. Aesthetasc y1 very short, situated behind t-setae. All t-setae plumose, among which t2 and t3 being longest, extending to 1/3 or 1/4 of length of claws from tips. Dorso-medial setae of penultimate segment (second endopodal segment) extending beyond terminal segment. z-setae not transformed, not extending to tip of claws. Aesthetasc y2 short. G1 longest claw, G2 and G3 sub-equal in size. GM reaching tips of G2 and G3. Gm reaching about distal third of GM. All claws serrated. Aesthetasc part of y3 about 1/3 length of Gm.

Md palp ( Fig. 14E ) with four segments. First segment (basis) with slender seta α accompanied by three unequal setae, two of which with setules. Second palp segment (first endopodal segment) with three dorso-apical setae of unequal length, and ventrally with four smooth, grouped setae, slightly shorter but plumose seta β, and shorter plumose accompanying seta. Third segment with ten apical setae, including strongly setulose seta γ. Third segment also with fine, long pseudochaetae on interior side. Fourth segment with seven distal setae/claws. Vibratory plate (exopod) with 6+1 plumose filaments.

Mx ( Fig. 14F ) with tooth bristles on third protopodal endite lobe strongly serrated distally. Third endite lobe also with plumose proximal seta.

L5 ( Fig. 15A ) protopod with two small setae a and plumose setae b and d. Palp (endopod) carrying three moderately long, plumose distal setae.

L6 ( Fig. 15B ) robust, consisting of four segments (penultimate segment undivided). First segment short, proximally with elongate, sclerotized anchoring structure, bearing long seta d1 and short, plumose seta d2. Second segment robust, bearing long pseudochaetae and antero-apical seta e, with setules distally. Third segment elongate, not sub-divided, bearing pseudochaetae, carrying medially plumose seta f and distally short seta g. Fourth segment short and sub-quadrate, bearing plumose seta h1, strongly serrated claw h2, and short seta h3.

L7 ( Fig. 15C, D ) with three segments. Basal segment bearing sub-equally long setae d1, d2 and dp. Second segment longest, bearing plumose seta e extending to about distal end of terminal segment, and with few pseudochaetae at sub-apical part. Third segment bearing plumose seta f and distally well developed pincer organ.

Ur ramus ( Fig. 15E ) thin and elongate, with short pseudochaetae along distal half of posterior margin. Claw Ga slightly longer than half length of ramus, slightly serrated. Gp claw about 1/3 length of ramus, slightly serrated. Sp seta situated close to distal claws, plumose, about twice as long as Sa. Main branch of Ur attachment curved, with small dorsal branch about two-thirds of length from ramus.

Remarks. This species can be identified by the shape, large size of the carapace, presence of small denticles along the anterior and posterior margins of both valves, as well as by the development of a longer spine at the postero-ventral margin of the RV. Cypris triaculeata ( Daday, 1892) is very similar to C. pubera , mostly differing in the position and numbers of spines on the postero-ventral part of the RV. These differences were considered as intraspecific variation by Meisch et al. (2019) leading to them listing C. triaculeata as a junior synonym of C. pubera . However, Mesquita-Joanes et al. (2020) considered the two species as separate based on morphology and a genetic analysis. They judged that some previous reports and figures of C. pubera actually refer to C. triaculeata , causing the confusion between the two species. With our specimens, the largest posterior spine on the RV is located near the ventral edge, corresponding to C. pubera (the largest spine is higher up on the posterior edge and near the point at maximum carapace length in C. triaculeata ).

Cypris pubera is a widespread species mostly occurring in the Holarctic (e.g. Meisch 2000), but with additional records from South America and New Zealand (e.g. Coviaga et al. 2018; Eager 1994). However, as noted by Mesquita-Joanes et al. (2020), some of these records could be misidentifications of C. triaculeata . Previous Chinese records include those from Nyalam District, Tibet ( Jiang & Chen 1974; Chen 1982). During this study, C. pubera was found once in a shallow pond with a sandy substrate and macrophytes at an altitude of 4167 m ( Table 1 ).

Figures

FIGURE 13. Cypris pubera O.F. Müller, 1776, female. (A) RV, exterior view (WOC9); (B) LV, interior view (WOC9); (C) LV, exterior view (WOC10); (D) LV, dorsal view with anterior end on the left (WOC10); (E) enlargement of antero-ventral margin of RV (WOC10); (F) enlargement of anterior margin of LV (WOC9). Scale bars: A–D = 500 μm; E, F = 100 μm.

FIGURE 14. Cypris pubera O.F. Müller, 1776, female (WOC10). (A) Right A1, exterior view; (B) close-up view of RO; (C) right A2, exterior view; (D) distal part of (C); (E) left Md palp, exterior view; (F) left Mx palp and 1st endite, exterior view (not all structures drawn).

FIGURE 15. Cypris pubera O.F. Müller, 1776, female (WOC10). (A) Left L5, exterior view (exopod not drawn); (B) left L6, exterior view; (C) right L7, exterior view; (D) distal part of right L7; (E) Ur and attachment.