Heterocypris savatenalintonae, Smith & Chang, 2020

Smith, Robin James & Chang, Cheon Young, 2020, Taxonomic assessments of some Cyprinotinae Bronstein, 1947 species (Crustacea: Ostracoda) from Japanese and Korean rice fields, including (re-) descriptions of six species and a review of the type species of the subfamily, Zootaxa 4795 (1), pp. 1-69 : 49-58

Heterocypris savatenalintonae sp. nov.

( Figs 4K & L , 26–30 )

2004 Heterocypris rotundata ( Bronstein, 1928) —Okubo: 24, figs 9 a–f (fide herein).

? 2014 Heterocypris salina ( Brady, 1868) —Yu: 134–139, figs 75, 77–79, in part (fide herein).

2016a Heterocypris rotundata ( Bronstein, 1928) —Smith et al.: 485–487, 489, 493–495, fig. 5, tables 1 & 2 (fide herein). 2016b Heterocypris sp.—Smith et al.: Appendix (fide herein).

2018 Heterocypris rotundata ( Bronstein, 1928) —Smith et al.: Appendix (Japanese records only) (fide herein).

Etymology. Named after Sukonthip Savatenalinton (Mahasarakham University, Thailand) in recognition of her significant contributions to the taxonomy of the Asian ostracod fauna.

Diagnosis. Left valve overlaps right valve along all margins. Lateral view with maximum height mid-length, posterior margin more inflated than anterior. Dorsal view ovoid, maximum width posterior of mid-length, anterior end not beak-shaped. Surface covered with ill-defined small pits (best observed with SEM). Weakly developed marginal denticles along postero-ventral margin of right valve. Male smaller than female. Antenna with long swimming setae, extending slightly beyond end of claws. Mandibular palp with relatively long alpha seta, very thin in distal half. Claw G2 of female short, about 69% length of claw G1. Maxillula Zahnborsten of third endite serrated. Fifth limb with d and b setae. Caudal ramus sexually dimorphic, ramus straight in female, distinctly curved in male. Hemipenis with rounded distal end to medial shield, and robust, thick lateral shield.

Type locality. The vicinity of Oroshimo, Kusatsu, Shiga Prefecture, Japan, 35.0746º N, 135.9340º E .

Material examined. Holotype. JAPAN • 1 ♂, with soft parts dissected in glycerine and sealed in a slide, valves stored dry in a micropalaeontological slide; Shiga Prefecture, Kusatsu, Oroshimo, Lake Biwa Museum ; 35.0746º N, 135.93402º E; alt. 90 m; 10 Sep. 2014; Robin J. Smith leg.; plastic container with mud and rice plants; LBM 1430009543 .

Allotype. JAPAN • 1 ♀, with soft parts dissected in glycerine and sealed in a slide, valves stored dry in a mi- cropalaeontological slide; same collecting data as for holotype; LBM 1430009544 .

Paratypes. JAPAN • 2 ♂♂, with soft parts dissected in glycerine and sealed in slides, valves stored dry in mi- cropalaeontological cavity slides; same collecting data as for holotype; LBM 1430009538 , LBM 1430009542 . • 1 ♀, with soft parts dissected in glycerine and sealed in a slide, valves stored dry in a micropalaeontological cavity slide; same collecting data as for holotype; LBM 1430009545 . • 1 ♂, with soft parts dissected in glycerine and sealed in a slide, valves stored dry in a micropalaeontological cavity slide; Shiga Prefecture, Kusatsu, Oroshimo, Lake Biwa Museum ; 35.0746º N, 135.93402º E; alt. 90 m; 22 Jun. 2009; Robin J. Smith leg.; rice field; LBM 1430009531 . • 1 ♀, with soft parts dissected in glycerine and sealed in a slide, valves stored dry in a micropalaeontological cavity slide; same data as preceding; LBM 1430009530 .

Other figured material. JAPAN • 2 ♂♂, whole, stored dry in micropalaeontological cavity slides; Shiga Pre- fecture, Koka, Kokacho Ueno ; 34.88653º N, 136.23216º E; alt. 208 m; 31 May 2014; Robin J. Smith leg.; rice field; LBM 1430009532 , LBM 1430009533 . • 2 ♀♀, whole, stored dry in micropalaeontological cavity slides; same data as preceding; LBM 1430009534 , LBM 1430009535 . • 5 ♂♂, with soft parts dissected in glycerine and sealed in slides, valves stored dry in micropalaeontological cavity slides; same collecting data as for holotype; LBM 1430009536 , LBM 1430009537 , LBM 1430009539 , LBM 1430009540 , LBM 1430009541 .

Other material. See Table 1.

Description. Carapace sexually dimorphic. Female carapace length 1246–1351 µm, height 737–775µm. Male carapace length 1047–1153 µm, height 623–662µm. Height / length 0-57–0.60. Female, lateral view anterior margin broadly curved with maximum curvature below mid-height ( Fig. 26A ). Posterior margin angular, with maximum curvature at approximately mid-height. Dorsal margin angular with maximum height at mid-length. Ventral margin straight to slightly convex. Left valve overlapping right along all margins, with clear overlap posteriorly and anteriorly, and along most of dorsal margin with exception of area near maximum height. Left valve with small flange at mid-height of posterior margin ( Fig. 26 A–C, marked with white triangles). Calcified inner lamella wide anteriorly, narrow posteriorly. Right valve posterior inner calcified lamella of even width, left valve with slightly widened calcified inner lamella at mid-height ( Fig. 26C ). Denticles weakly developed along posterior-ventral margin of right valve ( Figs 26D & F , 27F ). Anterior-ventral margin slightly uneven, with no clearly developed marginal denticles, outer list in central ventral area ( Figs 27B & C ). Selvage peripheral, inner list along anterior margin of right valve. Left valve with few marginal sockets in postero-ventral area ( Fig. 26E ). Surface of valves covered with weak, poorly defined pitting, slightly better developed towards anterior margin. Muscle scars typical of subfamily. Dorsal view ovoid, with posterior margin more inflated than anterior margin, anterior margin not beak-shaped, left valve overlapping right anteriorly and posteriorly; posterior overlap forming small ‘step’ at junction of valves (marked with white triangle on Fig. 26B ). Maximum width posterior of mid-length. Male smaller than female and with left valve lacking small flange on posterior margin as seen in female ( Figs 26G, H , 27D & E ), and therefore dorsal view without posterior small overlapping ‘step’ ( Fig. 26H ). Colour yellowish, with inconspicuous, pale brown patches ( Figs 4K & J , 30I ). In transmitted light microscopy, valves with poorly developed fine granular background (granules slightly smaller than normal pores), but without larger reticulation ( Fig. 32B ).

Antennules with seven articulated segments ( Fig. 28A ). First segment with tiny Wouters organ and short seta on dorsal edge, and two long setae on ventral apical corner. Second segment quadrate with tiny Rome organ and short apical-dorsal seta. Third segment with one apical-ventral seta and one apical-dorsal seta, both short. Fourth segment with two long apical-ventral setae and two shorter apical-dorsal setae. Fifth segment with two long apical-ventral setae and two medium-length apical-dorsal setae. Sixth segment with four long and one short (alpha) apical setae; alpha seta about 2.75 times length of dorsal margin of terminal segment. Seventh segment with two long and one medium-length apical setae and aesthetasc ya.

Female antenna, aesthetasc Y 24% length of dorsal sclerotised margin of first endopodal segment (marked with dotted arrowed line on Fig. 28B ). Natatory setae long, reaching slightly beyond end of claws. Claw G2 ca. 70% length of claw G1 ( Fig. 29A ). Claw Gm just over half length of claw GM. Male antenna ( Fig. 29B ) with G3 very small, about twice length of terminal segment. G1 claw-like, but very short, only slightly longer than G3. Z1 well developed, long claw, slightly longer than G2. Z2 stout, long seta. Claw Gm very slender, approximately half length of claw GM.

Mandible palp typical of subfamily, with 3+1+beta setae on inner side of second palp segment ( Fig. 28C ). Alpha seta long, tapering along length to flagellum-like end section ( Fig. 28D ). Beta seta hirsute and thick. Gamma seta stubby, capped with profusion of stiff setules. Mandibular coxa typical of subfamily, with well-developed teeth and small seta on outer side of endite ( Fig. 28E ).

Rake-shaped organ with 8 to 11 teeth.

Maxillula palp, first segment with group of five setae on outer apical edge, all of varying lengths, and two subapical setae, one of which long, located on outer edge, and other, shorter seta slightly displaced inwards ( Fig. 28F ). Second palp segment elongate, width/length 0.64. Apically with three claws and three setae. Third endite Zahnborsten serrated.

Fifth limbs of female with two a setae, b and d setae present and relatively long ( Fig. 29D ). Branchial plate with six rays. Palp with one long and two shorter terminal setae. Fifth limb palps of male asymmetrical ( Fig. 28G & H ). Left palp hook tightly curved and slender distally. Right palp hook inflated and larger than right, with noticeable lump on inner edge.

Sixth limb five segmented, slightly sexually dimorphic, with seta d1 noticeably shorter in male compared with female ( Fig. 29G & H ). In both sexes, setae e and f extending to end of next segment respectively. Fourth segment with two g setae, one relatively long and one much shorter. Claw h2 well developed and robust.

Seventh limb typical of family, consisting of three segments terminating with pincer arrangement ( Fig. 30A ). Seta d1 on first segment shorter than d2 and dp, d2 slightly shorter than dp.

Caudal rami sexually dimorphic; female caudal ramus with almost straight dorsal margin, male caudal ramus with distinctly concavely curved dorsal margin ( Fig. 30B & C ). Claws of male caudal ramus more curved distally compared with female’s. Male caudal ramus: sp seta varies in length from 29 to 37% length of caudal ramus, seta sa from 20 to 26%, claw Gp 38 to 48% and claw Ga 55 to 67%. Ratios of lengths of Gp to Ga range from 0.62 to 0.77. Caudal ramus attachment proximal section straight, distally curved, with two short dorsal branches, one located ca. 60%, and one ca. 83% of length from proximal end ( Fig. 30D & E ). Proximal section of caudal ramus curved in some specimens.

Hemipenes typical of subfamily, with roughly triangular medial shield, distally evenly rounded ( Fig. 30F ). Lateral shield boot-shaped, with distal end broadly rounded to slightly pointed, and width ranging from slender to thick ( Fig. 30G ). Some specimens with small knob on outer distal corner (‘heel’ of boot).

Zenker organ with 27–33 internal whorls of spines.

Spermatozoa range from 1072 to 1469 µm in length, with a mean of 1314 ± 3.6 µm (Smith et al. 2016, as Heterocypris rotundata ).

Morphological abnormalities. Two dissected females have aberrant setae on one fifth limb palp; one specimen has two setae protruding from approximately the mid-length of the left palp, while the other has one seta in a similar position on the left palp ( Fig. 29E & F ). A female also has an aberrant right antenna, with G2 claw missing, the GM claw of the terminal segment atypically small, and the Gm claw atypically large ( Fig. 29C ). The Gm claw is slightly wavy and smooth, missing the typical serration of antennal claws. One male specimen has a caudal ramus with five claws and one seta (other ramus of normal morphology), in contrast to the two claws and two setae normally seen in this species ( Fig. 30H ).

Remarks. This species was first reported from Japan as Heterocypris rotundata by Okubo (2004). Heterocypris rotundata , a species mostly reported from Europe and central Asia, is incompletely described, and most of the details of the chaetotaxy remain obscure. Meisch (2000) noted that its carapace is remarkably variable in size and shape, and specimens with transitional characters between it and Heterocypris incongruens exist. However, even taking this variability into account there are differences between the European and Japanese specimens. The Japanese specimens differ from Bronstein’s (1928) original description and other studies, such as Meisch (2000) and Fuhrmann (2012), in the following characters: the right valve lacks the depression near the anterior end (seen in dorsal view); the lateral view is slightly more inflated in the anterior-dorsal region; the posterior margin is more angular; the female left valve has a small flange on the posterior margin (absent in Heterocypris rotundata ); the right valve lacks marginal denticles along the anterior margin (present in Heterocypris rotundata ); the carapace is covered in weak pitting (absent in Heterocypris rotundata ); and the selvage of the right valve is marginal (selvage inwardly displaced in Heterocypris rotundata ; see Fuhrmann 2012). In the original description, Bronstein (1928) noted that the length of the terminal segment on the palp of the maxillula is more than twice the width, and this is one of the few characters of the appendages that he figured. In the Japanese specimens, the terminal segment of the maxillula palp is less elongate, with length less than twice the width, and the anterior claw (Ga) of the caudal ramus is proportionally shorter. Males are unknown in Heterocypris rotundata , so comparisons of male characters cannot be made.

Most described Heterocypris species have a noticeably different shape in lateral view compared to Heterocypris savatenalintonae sp. nov., but five species are similar in this respect. The differences of these species compared to Heterocypris savatenalintonae sp. nov. are listed below:

1. Heterocypris barbara ( Gauthier & Brehm, 1928) . The dorsal view of Heterocypris barbara is characterised by the left valve noticeably protruding beyond the right valve and the strong beak-shaped anterior end (both features missing in Heterocypris savatenalintonae sp. nov.). Additionally, the carapace surface of Heterocypris barbara is smooth, and the anterior denticles of the right valve well-developed, in contrast to the weak pitting and absent anterior denticles in Heterocypris savatenalintonae sp. nov. Bellavere et al. (2002) reported a similar species to Heterocypris barbara from Italy, but were unable to conclusively put a name to it. They concluded that it was either a sexual population of Heterocypris incongruens , or Heterocypris barbara , but lacking the anterior beak-shaped dorsal view that normally characterises the latter species. However, their specimens are different to Heterocypris savatenalintonae sp. nov., in particular the lateral view of the male carapace is much lower in their material and the lateral shield of the hemipenis differently shaped (as figured in Bellavere et al. 1999).

2. Heterocypris bogotensis Roessler, 1982 . This South American species differs in the posterior margin of the carapace, which is more rounded and missing the posterior flange, and the presence of marginal denticles on the anterior margin of the right valve (missing in Heterocypris savatenalintonae sp. nov.). Additionally, the selvage on the right valve is more displaced internally in Heterocypris bogotensis . Males of Heterocypris bogotensis are unknown, but the female appendages are very similar, with the exception of differing lengths of some setae (d1 on the sixth limb, sa and sp on the caudal ramus).

3. Heterocypris gregaria ( Skogsberg, 1917) . This species has a more rounded posterior, is missing the posterior flange, and the dorsal view is noticeably more compressed. The surface of the valves are reported to be irregularly reticulated. The G2 claw on the female antenna is also shorter (just over half the length of G1).

4. Heterocypris punctata Keyser, 1975 . This species has a more inflated anterior margin, a more rounded posterior margin, and lacks the small posterior flange on the left valve of the female. The surfaces of the valves are covered with well defined pits. The hemipenis has a more sharply rounded main body distally, and the outer lobe is wider proximally.

5. Heterocypris salina ( Brady, 1868) . This species has a similar lateral view to the carapace, but the left valve overlap is more prominent along the dorsal margin, the carapace is higher and the anterior margin more inflated in Heterocypris salina ( Fig. 31 ). The posterior overlap to the valves is also different, producing a distinct overlap in females of Heterocypris savatenalintonae sp. nov., whereas this is only slight in Heterocypris salina . The left valve of Heterocypris salina has a well-developed list on the anterior inner calcified lamella ( Fig. 31E , also see Meisch 2000 and Fuhrmann 2012), a feature missing in Heterocypris savatenalintonae sp. nov. At high magnification transmitted light microscopy, the valves of Heterocypris salina have a fine, poorly defined granular background (granules a few microns across, slightly smaller than normal pores) with a weak reticulated pattern overlying it (ca. 15–20 µm across) ( Meisch 2000) ( Fig. 32C ). The granular background is also present in Heterocypris savatenalintonae sp. nov., but the overlying, larger reticulation is missing ( Fig. 32B ).

The males of Heterocypris salina reported from China and figured by Yu (2014) are probably the same species as Heterocypris savatenalintonae sp. nov. based on the strong similarity of the appendages and carapaces. Additionally, the figured male specimens of Yu (2014) lack a list on the anterior inner calcified lamella of the left valve (which is present in Heterocypris salina ). However, it is unlikely that all Chinese records of Heterocypris salina listed in Yu (2014) are Heterocypris savatenalintonae sp. nov.

Distribution and ecology. No distribution data were given by Okubo (2004) for this species, so it is currently only known from Shiga Prefecture, Japan (herein). It is also probably present in China (see above), but its distribution there is unclear due to the confusion with Heterocypris salina . In Japan Heterocypris savatenalintonae sp. nov. inhabits rice fields from early May through to August. It has also been recovered in September from a water-filled plastic container with rice plants situated next to rice fields ( Table 1).

Figures

FIGURE 4. A & B, Cyprinotus cassidula sp. nov. (sample 10; see Table 1).A, left lateral view of whole carapace, female. B, left lateral view of whole carapace, male. C, Hemicypris megalops, whole carapace, right lateral view, female (paralectotype from Sumatra, Indonesia F12292c2, before dissection). D–F, Hemicypris posterotruncata. D & E, left lateral views of whole carapaces, females. F, dorsal view of whole carapace, anterior to left, female. G & H, Hemicypris ovata. G, paralectotype (NHMO F12264c), right view of whole carapace, female (prior to SEM). H, paralectotype (NHMO F12264b), internal view of right valve, female (before dissection). I & J, Hemicypris barbadensis (LBM 1430009514). I, left valve, internal view, female. J, right valve, internal view, female. K & L, Heterocypris savatenalintonae sp. nov. K, left lateral view of whole carapace, female. L, left lateral view of whole carapace, male. M–O, Hemicypris kibiensis (LBM 1430009515). M, left valve, internal view, female. N, right valve, internal view, female. O, high magnification transmitted light microscopy of valves. A–H, K & L, photographed while specimens submerged in water. I, J, M–O, mounted in unknown medium on glass slide.All photographs focussed stacked. Scale bar = 1506 µm for A & B, 1000 µm for C to N, 238 µm for O.

FIGURE 26. Heterocypris savatenalintonae sp. nov. A, whole carapace, right view, female (white arrow head indicates posterior flange) (LBM 1430009532, sample 34; see Table 1). B, whole carapace, dorsal view, female, anterior to right (white arrow head indicates posterior flange) (LBM 1430009535, sample 34). C, left valve, internal view, female (white arrow head indicates posterior flange)(LBM 1430009530, sample 3). D, right valve, internal view, female (LBM 1430009530, sample 3). E, left valve, internal view, female, detail of postero-ventral margin (LBM 1430009530, sample 3). F, right valve, internal view, female, detail of postero-ventral margin (LBM 1430009530, sample 3). G, whole carapace, right view, male (LBM 1430009532, sample 34). H, whole carapace, dorsal view, male, anterior to right (LBM 1430009535, sample 34). Scale bar = 500 µm for A–D, G & H, 92 µm for E & F.

FIGURE 27. Heterocypris savatenalintonae sp. nov. A, left valve, external ventral view, female (LBM 1430009530). B, right valve, external ventral view, female (LBM 1430009530). C, right valve, external ventral view, female, detail of central ventral area (LBM 1430009530). D, left valve, internal view, male (LBM 1430009531). E, right valve, internal view, male (LBM 1430009531). F, right valve, ventral view, female, detail of postero-ventral area (LBM 1430009530). G, right valve, oblique internal view, male, detail of antero-ventral area (LBM 1430009531). All specimens from sample 3 (see Table 1). Scale bar = 500 µm for A, B, D & E, 128 µm for C & F, 92 µm for G.

FIGURE 28. Heterocypris savatenalintonae sp. nov. A, antennule, female (LBM 1430009544). B, antenna, female (LBM 1430009544). C, mandibular palp, female (LBM 1430009544). D, alpha, beta and gamma setae of mandibular palp, female (LBM 1430009545). E, mandibular coxa, female (LBM 1430009544). F, maxillula palp and endites (setae on endites not drawn), female (LBM 1430009545). G, right fifth limb palp, male (LBM 1430009543). H, left fifth limb palp, male (LBM 1430009543). All specimens from sample 38 (see Table 1).

FIGURE 29. Heterocypris savatenalintonae sp. nov. A, detail of antenna, female (LBM 1430009544). B, detail of antenna, male (LBM 1430009542). C, detail of abnormal terminal segment of antenna, female (LBM 1430009545). D, fifth limb, female (LBM 1430009545). E, abnormal fifth limb palp, female (LBM 1430009545). F, abnormal fifth limb palp, female (LBM 1430009544). G, sixth limb, female (LBM 1430009545). H, sixth limb, male (LBM 1430009543). All specimens from sample 38 (see Table 1).

FIGURE 30. Heterocypris savatenalintonae sp. nov. A, seventh limb, female (LBM 1430009544). B, caudal ramus, female (LBM 1430009544). C, caudal ramus, male (LBM 1430009543). D, caudal ramus attachment, female (LBM 1430009544). E, caudal ramus attachment, male (LBM 1430009543). F, hemipenis (LBM 1430009543). G, outlines of hemipenes (from left to right, LBM 1430009541, LBM 1430009540, LBM 1430009542, LBM 1430009539, LBM 1430009536, LBM 1430009537). H, abnormal caudal ramus, male (1430009536). I, sketch of left valve, external view, showing position of pigmentation. All specimens from sample 38 (see Table 1).

FIGURE 31. Heterocypris salina (Brady, 1868). A, whole carapace, right view, female (LBM 1430009528). B, whole carapace, dorsal view, female, anterior to right (LBM 1430009528). C, right valve, internal view, female (LBM 1430009527). D, left valve, ventral view, female (LBM 1430009527). E, left valve, internal view, female, detail of antero-ventral margin (LBM 1430009527). Scale bar = 500 µm for A–D, 128 µm for E. All specimens from sample 1 in Smith et al. 2014.

FIGURE 32. High magnification transmitted light microscopy of valves.A, Hemicypris posterotruncata, showing a well developed fine granular background (LBM 1430009526). B, Heterocypris savatenalintonae sp. nov., showing a weakly developed fine granular background (LBM 1430009538). C, Heterocypris salina, showing a weakly developed fine granular background with a larger, overlying reticulation (LBM 1430009529). Photographed while valves submerged in water. All photographs focussed stacked.