Cavernocypris xiangi, Zhai & Smith & Zhang, 2025

Cavernocypris xiangi sp. nov.

Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7

Type locality.

Site Y 76 (Fig. 1 View Figure 1 , Table 1 View Table 1 ), spring-fed canal in Fengze Botany Garden of Kunming   GoogleMaps , Yunnan Province, China (25°16'20"N, 102°52'51"E, altitude 1973 m).

Type material.

All from type locality (Table 1 View Table 1 ). Holotype: dissected male ( WOC 172 ) GoogleMaps . Allotype: dissected female ( WOC 173 ) GoogleMaps . Paratypes: dissected males ( WOC 166 , WOC 167 , WOC 175 ) and females ( WOC 168 , WOC 169 , WOC 171 ). WOC 166 , WOC 169 , and WOC 175 with valve articulation intentionally retained during dissection GoogleMaps .

Other material examined.

Dissected male ( WOC 165 ) and female ( WOC 164 ) from site Y 56 (Table 1 View Table 1 ).

Derivation of name.

Named after Ji Xiang (232‒202 BC), a legendary military leader who rebelled against the cruel government of the Qin Dynasty in ancient China.

Dimensions.

Male (n = 5) LV L 0.55‒0.64 mm, H 0.28‒0.33 mm, H / L 0.50‒0.52 (Table 3 View Table 3 ). Female (n = 5) LV L 0.59‒0.64 mm, H 0.30‒0.34 mm, H / L 0.51‒0.54. RV slightly shorter and lower than LV of the same individual and usually with smaller H / L. Cp (n = 2) W / L 0.46‒0.48.

Diagnosis.

Cavernocypris with elongated pitted Cp. Dorsal appearance of Cp relatively stout. Dorsal area of LV without hump. Antero- and postero-ventral calcified inner lamellae of LV with inner list. Valve morphology without obvious sexual dimorphism. LV exceeds RV along all margins and overlaps RV ventrally. Seta γ of Md palp smooth. Ventral-most seta on the same segment minute. Hp with wide and long ls significantly exceeding ms. Apical part of ls bluntly angular. ZO with 12‒16 rosettes of spines.

Description.

(Sex noted only when describing dimorphic features.) Cp and valves sub-reniform in lateral view (Fig. 2 View Figure 2 ). LV larger than RV (Figs 2 E View Figure 2 , 3 A View Figure 3 ) overlapping RV ventrally (Fig. 2 G View Figure 2 ), resulting in less concave ventral margin than that of RV (Fig. 3 B View Figure 3 ). LV and RV also with subtle differences in outline along anterior and posterior margins (Fig. 3 B View Figure 3 ), with LV being less obtrusive at ventro-anterior and ventro-posterior areas but slightly less depleted at dorso-anterior and dorso-posterior areas. Sexual dimorphism in valve outlines subtle but persistent (Fig. 4 View Figure 4 ). Both valves of female more obtrusive potero-ventrally but more depleted dorso-posteriorly and antero-ventrally (Fig. 4 B, D View Figure 4 ). In other aspects, valve morphologies similar between sexes and between RV and LV (Fig. 2 View Figure 2 ). Highest point, i. e., antero-dorsal corner, at anterior 40‒45 %. Dorsal margin nearly straight, sloping posteriorly. Anterior margin broadly rounded. Posterior margin straight at upper section and narrowly rounded at postero-ventral corner. Ventral margin concave in RV, nearly straight in LV due to need to overlap RV (Fig. 3 View Figure 3 ). Valve surface densely covered with pits that become smaller toward hinge area (Fig. 2 F, I View Figure 2 ). Setal pores without rims. Selvage slightly displaced outwards at antero- and postero-ventral areas in both valves (Fig. 2 A, C, H View Figure 2 ). In interior view, LV with inner list on both antero- and postero-ventral areas (Fig. 2 D View Figure 2 ). RV with outer list easily observed from ventral view (Fig. 2 G, J View Figure 2 ).

A 1 (Fig. 5 A View Figure 5 ) with eight segments, first and second fused into elongated base, supporting one dorsal seta and two sub-equal ventral setae. Third segment sub-quadrate, jointed with preceding and following segments, carrying one dorso-apical seta. Wouter’s organ and Rome organ possibly present but cannot be confirmed in present specimens. Fourth segment sub-trapezoidal, carrying one dorso-apical seta and one ventro-apical seta. Following segment boundaries without joint structures. Fifth segment sub-quadrate, with two long dorso-apical setae and two short ventro-apical setae. Sixth segment slightly elongated, with two long dorso-apical setae and two short ventro-apical setae. One of ventro-apical setae of this segment very short in some specimens (arrowed in Fig. 5 A View Figure 5 ). Seventh segment elongated, with four long setae on interior surface and short seta α on dorso-apical position. Eighth segment slender, with three apical setae and aesthetasc ya. Aesthetasc ya more than three times length of this segment. Ventral seta slightly shorter than ya. Two medial setae much longer.

A 2 (Fig. 5 B ‒ D View Figure 5 ) with two protopodal segments (coxa and basis), one exopodal segment, and three endopodal segments (penultimate segment undivided in both sexes). Coxa with two sub-equal ventro-medial setae. Posterior seta absent. Basis with one long ventro-apical seta. Small sclerotized patterns present on coxa and basis as arrowed in Fig. 5 B View Figure 5 . Exopodal plate small, carrying three setae, longest one reaching mid-way of penultimate segment. Third one sometimes cannot be seen. First endopodal segment carrying slender aesthetasc Y. Swimming setae short, with sixth (dorsal-most) one longest, extending to about mid-way of next segment. Ventro-apical seta extending to mid-way of claws. Second endopodal segment (penultimate segment) carrying minute y 1 ventrally and two short, unequal setae dorso-medially. Female with 4 t-setae, t 4 being shortest. Male with only 1 t-seta. Female z 1 ‒ z 3 all setae. Male z 1 and z 2 transformed into serrated claws, with z 2 2 / 3 length of z 1. Female G 1 ‒ G 3 all strong claws. Female G 2 more strongly serrated than that of male. Male G 1 and G 3 both setae extending to about mid-way of longest claws, G 2 sub-equal to z 1 in size. Female GM long serrated claw, Gm smooth claw, or strong seta extending to mid-way of GM. Male GM and Gm morphologies resembling female Gm and GM, respectively. Aesthetasc part of y 3 extending to about mid-way of long claws in both sexes.

Md (Fig. 5 E, F View Figure 5 ) coxa elongated, endite distally with about 7 masticatory processes and with two unequal setae on inner edge and one short, stout, subapical seta near outer edge. Palp 4 - segmented. First segment (basis) elongated, dorsally bearing exopod (not shown) with 1 short and 4 long rays, and ventrally with slender seta α and three long, thick setae. Second segment dorsally with three unequal thin setae and ventrally with thick plumose seta β, three smooth grouped setae, and one longer smooth accompanying seta. Third segment dorso-subapically with four slender setae and apically with five setae, including thick smooth seta γ, three lateral setae, and one minute ventro-apical seta. Fourth segment with five claws / setae.

Mx palp (Fig. 6 A View Figure 6 ) 2 - segmented. First segment with one short sub-apical seta and four unequal dorso-apical setae. Second segment elongated, with four apical setae / claws. Tooth-bristles on distal gnathobasic endite smooth.

Male right (Fig. 6 B ‒ D View Figure 6 ) and left (Fig. 6 E ‒ G View Figure 6 ) L 5 palps unequal and with morphological variations between specimens. Trunk of right palp generally larger than that of left, both with small ventro-apical projection (projection in Fig. 6 G View Figure 6 lost, probably during preparation). Right clasper generally less curved than left, narrow (Fig. 6 C View Figure 6 ) or comparatively wide (Fig. 6 B, D View Figure 6 ). Distal end of claspers with small pointed sclerotized tip (blunt tip of Fig. 6 F View Figure 6 due to preservation or development). Protopod of L 5 with comparatively long setae a (Fig. 6 B, E View Figure 6 ). Setae b, c, and d absent. Exopod with two setae. Gnathobasic endite with about eight setae, some of which plumose.

L 6 (Fig. 6 H View Figure 6 ) with five segments. First segment (protopod) without seta d 1, with well-developed d 2. Second segment (first endopodal segment) with plumose seta e. Anterior margin of this segment usually with 1‒3 long pseudochaetae. Third segment stout, with plumose seta f. Fourth segment stout, with long, smooth seta g 1 extending significantly beyond terminal segment and minute accompanying seta g 2. Terminal segment short, carrying small seta h 1, strong and distally serrated claw h 2, and tiny seta h 3.

L 7 (Fig. 6 I, J View Figure 6 ) first segment (protopod) with comparatively short setae d 1 and sub-equally long setae d 2 and dp. Second segment (first endopodal segment) with short seta e. Third segment with seta f protruding from mid-length and row of pseudochaetae in apical area. Distally with pincer arrangement, h 2 relatively long.

Hp (Fig. 7 A, B View Figure 7 ) elongated, with greatest width at about proximal 2 / 5. ls protruding significantly beyond ms, with bluntly angular end. ms tapering distally. Internal structures typical of Cypridopsinae . Labyrinth stout, accompanied by elongated spinous element (arrowed in Fig. 7 B View Figure 7 ). Post-labyrinthal spermiduct with two full coils and descending tube.

Ur (Fig. 7 D View Figure 7 ) present only in female, situated to interior side of GL. Basal part not cylindrical as in Plesiocypridopsis (cf. Meisch 2000), tapering distally. Two apical setae unequal.

GL (Fig. 7 D View Figure 7 ) of each side consisting of two rounded lobes, broader anteriorly than posteriorly. Anterior part with semi-circular tube (arrowed in Fig. 7 D View Figure 7 ). Medially lacking sclerotized hook / spine-like structure (e. g., those in Plesiocypridopsis and Cypridopsis ).

ZO (Fig. 7 C View Figure 7 ) elongated, with 12‒16 rosettes of spines between two terminal plates. Central tube cylindrical, with fine transverse patterns.

Differential diagnosis.

When males are present, Cavernocypris xiangi sp. nov. can be easily distinguished from congeneric species by the peculiar Hp that bears a large ls (Fig. 7 A, B View Figure 7 ). Even if males are not available, the new species can be distinguished by the pitted valve surface and setal pores without rims (Fig. 2 View Figure 2 ). The setal pores of at least C. cavernosa , C. coreana , C. danielopoli , and C. subterranea possess rims. Cavernocypris hokkaiensis has smooth valves, and the posterior valve margin is not as narrow as in C. xiangi sp. nov. The dorsal part of the valve of C. reddelli has only one apex (lacking a postero-dorsal angle) in lateral view, and its LV carries a prominent inner list in the posterior area. The swimming setae 1‒5 on the A 2 of C. reddelli are longer than seta 6, and its Hp ( Külköylüoğlu 2020) resembles that of Cypridopsis vidua ( Martens et al. 2023; Zhai et al. 2023), which belongs to another genus of the same tribe. These features make C. reddelli somewhat peculiar in the genus, and it can thus be distinguished from the new species. Cavernocypris wardi has serrated Mx tooth-bristles, and the proximal part of the Ur is much wider than that of the new species ( Marmonier et al. 1989). The absence of setae b and d on the L 5 of the new species makes it different from C. coreana elongata (seta b present, Marmonier et al. 1989; Külköylüoğlu and Vinyard 1998), C. reddelli (seta d present, Külköylüoğlu 2020), C. subterranea (both setae b and d present, Marmonier et al. 1989), C. wardi (both setae b and d present, Marmonier et al. 1989).