Stenocypris viridis Okubo, 1990

Ma, Shunxin & Yu, Na, 2018, Freshwater ostracods (Crustacea) from Tiantong National Forest Park and Dongqian Lake, eastern China, with descriptions of two new species, Journal of Natural History 52 (27 - 28), pp. 1825-1868 : 1852-1855

Stenocypris viridis Okubo, 1990

( Figures 18d–g , 20 , 21 )

Stenocypris viridis sp. nov. Okubo, 1990: 42–44, fig. 2(f–i).

Material examined

Three females (ECNU20140909/TT26-28) dissected.

Dimensions

(Female, n = 3) Length, 1.50–1.60 mm; height, 0.57–0.62 mm; width, 0.44 mm.

Re-description

Carapace long and smooth, surface of carapace with setae along all margins except dorsal margin. Some long setae present on posterior end. Reni-form in lateral view. Ventral margin concave. Dorsal margin slightly arched. Anterior end wider than the posterior. Anterior margin with long, crooked septa, and septa narrower along ventral and posterior margins.

A1 seven-segmented. First segment with one short dorsal seta and two long ventral setae. Second segment with one short seta dorsal-distally and Rome organ. Third segment with one long dorsal and one short ventral seta. Fourth and fifth segments each with two dorsal setae and two ventral setae. Sixth segment with four long setae and one short setae distally. Seventh segment with two long setae, one aesthetasc ya and one short claw-like seta.

A2 four-segmented. Exopod consisting of one small plate and three setae (two short and one long), the long one exceeding end of first endopodal segment. First endopodal segment with three-segmented aesthetasc Y. Natatory setae exceeding tips of terminal claws. Seta t4 longer and stronger than other three t setae. All z setae equally long. Claw G1 approximately three-quarters length of claw G2. Claw Gm approximately one-half length of claw GM.

Md palp with slender α seta, stout β seta and hirsute γ seta. Coxa with well-developed teeth.

Mx1 palp two-segmented. Terminal segment rectangular. One of two large bristles on third masticatory lobe of Mx1 with fine serration, and other one slightly more slender and smooth.

L5 with two short setae a, one long b seta and one long d seta. Both b and d setae hirsute.

L6 five-segmented. Setae e and f almost reaching to end of next segment, respectively. Two g setae present, long one exceeding end of terminal segment.

L7 four-segmented. Basal segment with three d setae. Seta e reaching to end of next segment, and row of fine hairs present on end of second segment. Seta f protruding from middle of penultimate segment, exceeding end of terminal segment. Terminal segment with long h3 seta and pincer-organ.

UR asymmetrical. Right one more well-developed than the left. Both claws Ga and Gp with well-developed denticles. Claw Gp equalling one-half length of claw Ga. Seta Sa and claw Ga equally long. Seta Sp absent. Row of large spines presents on mid-posterior part of right UR. Only fine setae present on ramus of left UR.

UR attachment straight, with basal triangular reinforcement. Both ventral and dorsal branches long.

Distribution

Stenocypris viridis was previously only reported from Japan ( Okubo 1990, 2004). This species is a new record for China and may be endemic to eastern Asia.

Remarks

Many characters, including not only the carapace but also of the soft body, are shared by genera Stenocypris and Chrissia , but Stenocypris can be distinguished from Chrissia by the conspicuous septa along the free margin of the carapace (Karanovic 2012). Although only a few morphological features of S. viridis (including characters of the carapaces, UR and UR attachment) have been described and illustrated by Okubo (1990, 2004), we can identify our specimens as S. viridis because of the crooked outline formed by the arrangement of septa on the inner antero-dorsal margin of the valves, the smooth surface of the carapace, the length ratios between both claws (Gp / Ga = 0.5), and between the seta Sa and claw Ga (Sa / Ga = 1.0) on the UR, etc. It is considered to be very hard to distinguish S. viridis from Stenocypris bolieki (Karanovic 2012) . However, they can be distinguished from each other by the length of carapace, the shape and width of septa, the length of natatory setae on A2, etc. For example, S. viridis (1.20–1.60 mm) is smaller than S. bolieki (1.70–1.77 mm); the septa of S. viridis are wider than those of S. bolieki ; the shape of the septa is more crooked in S. viridis than in S. bolieki ; and the natatory setae on A2 of S. bolieki just reach or slightly exceed the tips of terminal claws, while those of S. viridis obviously exceed the tips of terminal claws ( Ferguson 1962).

Stenocypris viridis is re-described in this study. The UR of our specimens differ slightly from the Japanese ones by the following characters: (1) one or two spines are present on the end of the stem of the left UR in Japanese specimens, whereas the spine is missing in our specimens ( Figure 21c ); (2) the arrangement of spines on right UR is sectionalized in Japanese specimens ( Okubo 1990, 2004), and it is continuous in our specimens ( Figure 21b ).

Figures

Figure 18. (a) Stenocypris derupta Vávra, 1906. Female. (a) ECNU20140913/TT65.1, external view of LV. (b, c) Stenocypris hirutai Smith and Kamiya, 2006. Female. (b) ECNU20140914/TT14, external view of LV; (c) ECNU20140914/TT14, internal view of RV. (d–g) Stenocypris viridis Okubo, 1990. Female. (d) ECNU20140909/TT26, external view of RV; (e) ECNU20140909/TT26, internal view of RV; (f) ECNU20140909/TT2601, dorsal view; (g) external view of RV. Scale bars: 100 μm.

Figure 20. Stenocypris viridis Okubo, 1990. (a, c and d) (ECNU20140909/TT27); (b, f) (ECNU20140909/ TT26); (e, g) (ECNU20140909/TT28). Female. (a) A1; (b) A2; (c) Md palp; (d) Md coxa; (e) Mx1; (f) L5; (g) L6. Scale bars: 100 μm.

Figure 21. Stenocypris viridis Okubo, 1990. (a) (ECNU20140909/TT28); (b, c) (ECNU20140909/TT27); (d) (ECNU20140909/TT26). Female. (a) L7; (b) Right UR; (c) Left UR; (d) UR attachment. Scale bars: 100 μm.