Pseudocandona cheni, Yu & Ma & Wang & Zhai, 2022

Yu, Na, Ma, Shunxin, Wang, Qianwei & Zhai, Dayou, 2022, Three new species of non-marine ostracods (Crustacea, Ostracoda) from small water bodies of northern China, ZooKeys 1097, pp. 183-207 : 183

Pseudocandona cheni sp. nov.

Figs 1 , 2 , 3

Pseudocandona sp. 2 - Zhai et al. 2017: 486, fig. 9.

Type locality.

A small shallow pond (Y26, Table 1 ) in Inner Mongolia, China.

Type material.

Holotype: one male (dyzoc567). Allotype: one female (dyzoc569). Paratypes: one male (dyzoc568) and three females (dyzoc570, dyzoc706, dyzoc707). All from the type locality, with soft parts dissected, valves preserved on the micropalaeontological slides.

Other material.

One male (dyzoc625) and one female (dyzoc626), both from the site Y30 (Table 1 ), with soft parts dissected, valves preserved on the micropalaeontological slides. One female (dyzoc813), from the type locality. One female (dyzoc814), from the site Y30 (Table 1 ). Both undissected, with carapace enclosed, preserved on the micropalaeontological slides.

Etymology.

This species is named after Prof. Shouzhong Chen (= Shoutsung Chen; Institute of Hydrobiology, Chinese Academy of Sciences), who was the first among the Chinese ostracod workers to describe soft parts of non-marine ostracods from China ( Chen 1957).

Dimensions.

Male, n = 3, LV, length 860-872 μm, height 510-535 μm; RV, length 842-849 μm, height 485-513 μm. Female, LV, n = 5, length 874-941 μm, height 526-574 μm; RV, n = 3, length 874-903 μm, height 497-520 μm.

Diagnosis.

Carapace sub-trapezoidal in lateral view, relatively short and stout, with hinged part of dorsal margin nearly straight and sloping anteriorly (Fig. 1 ). Setal group on second segment of Md palp with five setae (Fig. 2D ). Right palp of L5 with wide trunk and ventrally curved finger-like end (Fig. 3C ). Left palp with elongated and ventrally curved trunk (Fig. 3D ). Hemipenis with M-process triangular distally. Lobe a tongue-like. Lobe b shortest, with sub-quadrate distal part on inner edge and triangular distal part on outer edge. Lobe h with rounded distal part (Fig. 3G ).

Description.

Carapace surface densely covered with small shallow pits in anterior, posterior, and dorsal areas (Fig. 1B ). In lateral view, greatest height posterior of mid-length. Postero-dorsal angle of male valve (Fig. 1A, B ) slightly blunter than female (Fig. 1E, F ). Ventral margin nearly straight. Anterior margin narrower than posterior. Anterior calcified inner lamella wide. Carapace compressed in anterior area and postero-ventral corner (Fig. 1I, J ). LV overlaps RV on dorsal, ventral, and posterior sides, and slightly exceeds RV anteriorly (Fig. 1I, J ).

A1 (Fig. 2A ) seven-segmented. First segment with two dorsal and two long ventral setae. Second segment with one short dorso-apical seta. Third segment without seta. Fourth and fifth segments with two long dorso-apical setae and one short ventro-apical seta, respectively. Sixth segment with one short and three long apical setae. Terminal segment with one short and two long setae and aesthetasc ya.

Male A2 (Fig. 2B ) five-segmented. Seta t2 and t3 transformed into male bristles, both similar in morphology, each terminating with slightly inflated, triangular process. Claws z1 and z2 long, slightly shorter than claw G2. Seta G3 slim, slightly exceeding end of terminal segment. Claw G1 short, slightly exceeding half-length of claw G2. Claw Gm slightly exceeding half-length of claw GM.

Female A2 (Fig. 2C ) four-segmented. Claw G2 short, not reaching half-length of claw G3. Claw G3 slightly shorter than claw G1. Claw Gm exceeding half-length of claw GM. Setae t1 - 4 unequally long, with t1 and t3 being longest while t4 being shortest. Seta z1 short, extending to ca. mid-way of terminal segment. Setae z2 and z3 extending to ca. mid-way of G -claws but z2 slightly longer than z3.

Md (Fig. 2D ) palp with short and slender α -seta. Seta β short and slender with 5 grouped setae and one sub-equally long accompanying seta on second segment. Seta γ long, smooth, and slender.

Mx (Fig. 3A ) palp two-segmented. Second segment spatulate. Two tooth-bristles on third masticatory lobe smooth.

Male L5 (Fig. 3C, D ) asymmetrical. Right palp basally wide, grading to finger-like end, with two sub-apical setae. Left palp distally narrower than right, with two sub-apical setae.

Female L5 (Fig. 3B ) with long b - and d - setae, and one long a -seta.

L6 (Fig. 3E ) five-segmented. First segment with d1 -seta extending slightly beyond this segment. Setae e and f extending to ca. tips of second and third endopodal segments, respectively. Seta g exceeding beyond terminal segment with ~ 50% of length. Terminal segment with h1 -seta conspicuously longer than h3 -seta.

L7 (Fig. 3F ) five-segmented. First segment with d1 -, d2 - and dp - setae. Setae e and f absent. Seta g long. Terminal segment with short h1 -seta and long h2 - and h3 - setae.

UR (Fig. 3H ) with tiny seta Sa. Claw Gp slightly shorter than claw Ga. Seta Sp slightly exceeding end of ramus.

Hemipenis (Fig. 3G ) sub-ovate in outline. Lobe a tongue-like, with sub-quadrate distal end. M-process with triangular distal part. Lobe b shorter than lobes a and h, with sub-quadrate distal part on inner edge and triangular distal part on outer edge. Lobe h slightly shorter than lobe a, with rounded distal part. Bursa copulatrix elongated with long finger distally.

Remarks.

The genus Pseudocandona Kaufmann, 1900, with 72 species described to date, is the third most diverse genus of the non-marine ostracods after Candona Baird, 1845 and Strandesia Stuhlmann, 1888 (see Meisch et al. 2019). [ Karanovic (2005, 2012) proposed an alternative taxonomic scheme where Typhlocypris Pseudocandona is treated as a subgenus under the genus Typhlocypris Vejdovský, 1882 and it only contains the six species of the Pseudocandona compressa group, but we follow Namiotko et al. (2014) who redefined the genus Typhlocypris .] The genus, as accepted at the moment, consists of five species groups (caribbeana, Pseudocandona compressa , prespica, rostrata, and zschokkei) and some species with uncertain positions ( Namiotko and Danielopol 2004; Meisch et al. 2019). This division is mostly based on the number of posterior setae on the second segment of Md palp. Species with 5+1+ β setae, as well as with the h1 -seta on the L7 being more than twice the length of terminal segment, are classified in the Pseudocandona compressa group ( Meisch 1996, 2000; Namiotko and Danielopol 2004), to which the present new species also belongs. Other species of this group are P. albicans (Brady, 1864), P. compressa (Koch, 1838), P. insculpta (G. W. Müller, 1900), P. pratensis (Hartwig, 1901), P. regisnikolai Karanovic & Petkovski, 1999, and P. sucki (Hartwig, 1901) ( Karanovic and Petkovski 1999; Meisch 2000; Karanovic 2012). Pseudocandona albicans can be distinguished from the present species by a shorter seta that accompanies the group of the five setae on the Md palp (sub-equally long to the grouped setae in the present species), a much slenderer first endopodal segment of the L6, as well as a slenderer carapace in dorsal view ( Meisch 2000). Male bristles on the A2 are absent in P. insculpta ( Meisch 2000), which easily distinguishes it from the present species. No other species of the Pseudocandona compressa group has the morphology of the male L5 and the Hp similar to P. cheni . In P. compressa , P. insculpta , and P. pratensis , the lob h is not distally inflated (albeit slightly curved in P. pratensis ), their right L5 have slenderer trunks. The lobe h in P. sucki is very wide, while the lobe b is small ( Meisch 2000). Pseudocandona regisnikolai is much larger (females range between 1.33 and 1.4 mm and males are up to 1.53 mm) ( Karanovic and Petkovski 1999). In addition, P. regisnikolai possesses only one dorsal seta on the basal segment of the A1, setae t2 and t3 on the male A2 are not transformed into bristles, the left prehensile palp of male is much slenderer than the right one, and the Hp bears a conspicuous lobe g ( Karanovic and Petkovski 1999).

Figures

Figure 1. Pseudocandona cheni sp. nov. A-D male, dyzoc 567 (holotype) A outer view of LV B outer view of RV C inner view of LV D inner view of RV E-H female, dyzoc 569 (allotype) E outer view of LV F outer view of RV G inner view of LV H inner view of RV I female, dyzoc 813, dorsal view of carapace, anterior to left J female, dyzoc 814, ventral view of carapace, anterior to left. Scale bars: 100 μm.

Figure 2. Pseudocandona cheni sp. nov. A male, dyzoc 567 (holotype), A 1 B male, dyzoc 567, A 2 C female, dyzoc 570, part of A 2 D male, dyzoc 567, Md. Scale bars: 100 μm.

Figure 3. Pseudocandona cheni sp. nov. A male, dyzoc 567 (holotype), Mx B female, dyzoc 570, L 5 C male, dyzoc 567, right L 5 palp D male, dyzoc 567, left L 5 palp E male, dyzoc 567, L 6 F male, dyzoc 567, L 7 G male, dyzoc 567, Hp H male, dyz 567, UR. Scale bars: 100 μm.