Hemicypris ovata Sars, 1903

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 : 35-40

Hemicypris ovata Sars, 1903

( Figs 4G & H , 14H & I , 18 & 19 )

1903 Hemicypris ovata, G. O. Sars , n. sp. —Sars: 5, 26–27, pl. III 2a & b.

1906 C. ovata Sars—Vávra : 424.

1910 Cyprinotus (Hemicypris) ovatus (Sars) —Daday: 181, 182.

1912 C. ovatus (O. Sars) 1903 —Müller: 163, 167.

1932 ovata— Klie: 471.

non 1950 Cyprinotus ovatus (Sars) —Tressler: 66, fig. 12n (fide Victor & Fernando 1981).

1955 H. ovata Sars—Howe : 88.

1970 Hemicypris ovata Sars 1903 – Bate: 290, 291, 292, 294, text-fig. 2c & d.

? 1972a Cyprinotus ovatus (Sars) —Deb: 234, 235, 238, 240–241, text-fig. 2 (fide herein).

? 1972b Cyprinotus ovatus (Sars) —Deb: 309, 311 (fide herein).

1974 Heterocypris ovata Sars—Purper & Würdig-Maciel : 72.

1978 Hemicypris ovata —Victor & Fernando: 417.

1979 Hemicypris ovata Sars—Victor & Fernando : 187.

1980 Hemicypris ovata Sars, 1903 —Hanai et al.: 128.

1980 Hemicypris ovata Sars, 1903 —Victor & Fernando: 959.

1981 Hemicypris ovata Sars, 1903 —Battish: 656.

1981 Hemicypris ovata Sars, 1903 —Victor & Fernando: 11, 17–21, 24, figs 47–62.

1983 Hemicypris ovata Sars, 1903 —Broodbakker: Table 1.

non 1994 ovata Sars, 1903 —Martens & Behen: 27 (fide Victor & Fernando 1981).

non 1998 Hemicypris ovata Sars, 1903 —Martens et al.: 52 (fide Victor & Fernando 1981).

non 2004 Hemicypris ovata Moniez, 1892 [sic]—Okubo: 27, figs 11e–h (fide herein).

2006 Hemicypris ovata Sars, 1903 —Krstić: 189.

2008 Hemicypris ovata Sars, 1903 —Savatenalinton & Martens: 17, 20, 22, table 1.

2011 Hemicypris ovata Sars, 1903 —Martens & Savatenalinton: Table 2.

? 2012 Hemicypris ovata Sars 1903 a—Karanovic: 439, 440, figs 150c, 151b (fide herein, in part).

2013 Hemicypris ovata— Akindele: Table 1.

? non 2013 Hemicypris ovata Moniez, 1892 ? [sic]—Kume: 4 (fide herein).

2013 Hemicypris ovata Sars, 1903 —Martens et al.: No page numbers.

2014 Hemicypris ovata Sars, 1903 —Karuthapandi et al.: 6578, table 3.

? non 2014 Hemicypris ovata Sars, 1903 —Savatenalinton: 197, 204, table 2, fig. 5c (fide herein).

? non 2016 Hemicypris ovata Sars, 1903 —Savatenalinton & Suttajit: 8, 9, 19 (fide herein).

2017 Hemicypris ovata— Akindele & Olutona: Table 2.

2017 Hemicypris ovata Sars, 1903 —Karuthapandi & Rao: 259.

2017 Hemicypris ovata Sars, 1903 —Matzke-Karasz et al.: 20.

2017 Hemicypris ovata Sars 1903 —Rasouli & Aygen: 423, 428, Fig. 5e .

? 2017a Hemicypris ovata ( Sars, 1903) [sic]—Savatenalinton: 28 (fide herein).

? 2017b Hemicypris ovata Sars, 1903 —Savatenalinton: Table 1 (fide herein).

2018 Hemicypris ovata Sars, 1903 —Smith et al.: Appendix.

2019 Hemicypris ovata Sars, 1903 —Meisch et al.: 64.

Diagnosis. Carapace, posterior margin slightly more rounded than anterior margin, ventral margin approximately straight, maximum height at about mid-length. Left valve with well developed marginal denticles along posteroventral and antero-ventral margins. Surface of valves smooth, with exception of area near anterior margin of left valve; here crescent-shaped area of small, shallow, but well-defined pits. Alpha seta of antennule long, over three times longer than length of terminal segment. Antennal aesthetasc Y 26% length of dorsal sclerotised margin of first endopodal segment, swimming setae long, reaching beyond ends of claws. Antenna, claw G2 long, ca. 77% length of claw G1, claw Gm slender and long, ca. 75% length of GM. Mandibular gamma seta short and triangular, with wide base and long, stiff setules distally on both inner and outer edges. Maxillula third endite with one smooth and one robustly serrated Zahnborsten. Sixth limb first segment with d1 seta, second segment with e seta reaching to distal end of third segment, third segment with f seta reaching to slightly beyond distal end of fourth segment. Seventh limb (cleaning limb) with seta dp on first segment similar in length to d2 of same segment, d1 shorter, second segment with long e seta, not reaching to distal end of third segment. Caudal ramus with claw Ga noticeably larger than claw Gp, both claws slender, seta sp about 90% as long as claw Gp, sa long, reaching to mid-length of Ga. Caudal ramus attachment with small dorsal branch.

Material examined. Paralectotypes. INDONESIA • 1 ♀, with soft parts dissected in glycerine and sealed in a slide, right valve stored dry in a micropalaeontological slide; Sumatra; NHMO F12264 b. • ♀, whole, stored dry in a micropalaeontological cavity slide; Sumatra; NHMO F12264 c.

Both paralectotypes examined were in poor condition, with the valves opaque white, indicating some degree of decalcification ( Fig. 4G & H ). Paralectotype F12264b consisted of a right valve containing the remains of the partially decayed body (the left valve was missing) ( Fig. 4H ). This specimen was dissected for this study (dissection slide F12264b1 and valve F12264b2). Musculature within the appendages is absent, but the chaetotaxy is almost complete. The valve was considered too delicate to photograph using SEM. Paralectotype F12264c is a whole, tightly closed carapace ( Figs 4G , 14H & I ). Despite the partial decalcification, this specimen seems to have mostly retained its original shape (but see Remarks below). It was used for SEM observation, but the integrity of the valves proved insufficient for extensive examination .

Description (based on paralectotypes). Paralectotype F12264b2, right valve: length 1225 µm, height 717 µm, length / height = 0.59. Paralectotype F12264c, whole carapace: length 1183 µm, height 695 µm, length / height = 0.59 (but see Remarks). Lateral view, right valve overlaps left along all margins, with most overlap anteriorly ( Fig. 14H ). Posterior margin slightly more rounded than anterior margin. Dorsal margin curved, slightly angular at maximum height (just posterior of mid-length) and at postero-dorsal margin. Ventral margin straight to slightly concave. Surface of valves smooth, with exception of area near anterior margin of left valve; here crescent-shaped area of small, shallow, elongated pits ( Fig. 14I ). Dorsal view ovoid, maximum width posterior of mid-length, anterior and posterior margins approximately equally rounded. Left valve with well developed marginal denticles along postero-ventral and antero-ventral margins. Colour of carapace not distinguishable in paralectotypes, but Sars (1903) reported yellow tinge and absence of pigmentation.

Antennule with seven articulated segments ( Fig. 18A ). First segment large, one seta on dorsal margin at approximately mid-length, and two long setae near apical-ventral corner; Wouters organ not observed (possibly dislodged). Second segment wider than long, with one seta on apical-dorsal corner, and tiny bottle-shaped Rome organ near ventral margin. Third segment longer than wide, with one seta on apical-dorsal corner and one short seta on apical-ventral corner. Fourth and fifth segments each with two long setae on apical-dorsal corner, and two shorter setae on apical-ventral corner. Sixth segment with four long setae and one shorter (alpha) apical seta 3.7 times longer than dorsal margin of terminal segment. Terminal segment with two long and one short, claw-like setae, and aesthetasc ya.

Antenna, exopodite with long seta reaching to end of first endopodal segment, medium-length seta ca. onethird length of longest seta, and short seta ( Fig. 18B ). Aesthetasc Y 26% length of dorsal sclerotised margin of first endopodal segment (marked with dotted arrowed line on Fig. 18B ). Swimming setae long, reaching beyond ends of claws. Seta t2 long, reaching beyond mid-length of claws, t1 and t4 shorter ( Fig. 18C ). Claw G2 long, ca. 77% length of claw G1. Claw Gm slender and long, ca. 75% length of GM.

Mandible, both palps with incomplete chaetotaxy (some setae dislodged) ( Fig. 19A ). First segment with small, slender alpha seta, tapering distally to setule-like distal end ( Fig. 19A & D ). Second segment 3+1+beta setae on inner edge, and three setae on outer edge. Beta seta setulous, longer than alpha ( Fig. 19A & D ). Third segment with group of four sub-apical setae on outer edge, gamma + 3 setae along distal edge, and two setae on inner sub-apical edge ( Fig. 19A & B ). Gamma seta elongate and triangular and with long, stiff setules distally ( Fig. 19B & D ). Terminal segment with three stout claw-like setae and three thinner setae ( Fig. 19A & C ). Coxa typical of family ( Fig. 18D ).

Maxillula palp, first segment with group of five setae on outer apical edge, all of varying lengths, and two sub-apical setae, one of which long, located on outer edge, and other, much shorter seta displaced inwards ( Fig. 18E ). Second segment sub-quadrate, slightly widening distally, apically with three claw-like robust setae, and three smaller setae. Third endite with one smooth and one robustly serrated Zahnborsten.

Rake-shaped organ with eight teeth ( Fig. 18F ) (nine reported by Victor & Fernando 1981).

Fifth limb (maxilliped) with long d and b setae; c seta missing, typical of subfamily ( Fig. 19E ). Setae a not observed (obscured). Endite with ca. 12 apical setae. Exopodite (branchial plate) present, but number of rays unclear (partially decayed). Palp with three apical setae, one long and two much shorter, similar in length.

Sixth limb (walking leg) robust with five articulated segments ( Fig. 19F ). First segment with hirsute d1 seta. Second segment with e seta reaching to distal end of third segment. Third segment with f seta reaching slightly beyond distal end of fourth segment. Fourth segment with two g setae, one relatively long and one tiny. Fifth segment with h1 and h3 similar lengths, and h2 claw long and robust.

Seventh limb (cleaning limb) with seta d1 on first segment shorter than d2, seta dp of same segment about as long as d2 ( Fig. 19G ). Second segment with long e seta almost reaching to distal end of third segment. Third segment with f seta at mid-length, reaching almost to distal end of segment. Pincer structure compact, seta h2 projecting distally.

Caudal ramus with claw Gp 70% length of claw Ga ( Fig. 19H ). Seta sp long, 91% length of claw Gp. Seta sa slender and relatively long, 46% length of claw Ga. Caudal ramus attachment main branch sinuous, curved more distally, with tiny secondary branch at 57% of length from proximal end ( Fig. 19I ).

Remarks. The paralectotypes examined for this study were both partially decalcified and generally poorly preserved. Paralectotype F12264c seemed to have retained the original shape of the carapace despite partial decalcification, but the valves could be slightly deformed; the SEM photograph of paralectotype F12264c is slightly less high than the transmitted light photograph of the same specimen taken while in water, which suggests that the valves may have curled slightly while being dried prior to SEM ( Figs 4G & 14H ). Ideally fresh material needs to be collected from Sumatra, but the locality and habitat of the original collection are unknown. The “posterior margin of the penultimate segment with three short spines” reported for the seventh limb of the lectotype by Victor & Fernando (1981) probably refers to groups of pseudochaetae seen edge on; one group was vaguely observable in paralectotype F12264b.

Males of Hemicypris ovata were reported from India by Deb (1972a), but these records need confirmation. In lateral view the specimens from India are generally similar to the paralectotypes, although smaller, but the Zahnborsten of the maxillula both seem to be serrated (only one serrated in Hemicypris ovata ). The figures of Deb (1972a) are not sufficiently detailed to make further comparisons. Hemicypris ovata reported from Japan by Okubo (1990b as Hemicypris nipponica ; 2004) is herein considered to be a variety of Hemicypris posterotruncata (see under Hemicypris posterotruncata for more details). The identification of Hemicypris ovata from Japan by Kume (2013) was based on Okubo (2004), so is likely to also be Hemicypris posterotruncata . The figured specimen of Hemicypris ovata from Thailand in Savatenalinton (2014) is higher (height / length 0.63) than the paralectotypes (height / length 0.59), and it has a more prominent angle on the dorsal margin at maximum height compared to the paralectotypes. It also appears to be lacking the crescent of pits near the anterior margin of the left valve. This may suggest that the Thai species is not conspecific. Karanovic (2012) figured a left valve of “ Hemicypris ovata ”, but this is not sufficient to determine the accuracy of the identification. The provenance was not given, but the same specimen was figured by Schöning (1994) as “ Hemicypris sp.”, a subfossil from Sudan. Reports of Hemicypris ovata from Nigeria ( Akindele 2013; Akindele & Olutona 2017) are not accompanied by figures so cannot be assessed.

As noted by previous authors, Hemicypris ovata and Hemicypris megalops are morphologically similar species ( Sars 1903; Victor & Fernando 1981). Sars (1903) noted that the differences include carapace size and shape ( Hemicypris megalops is smaller and more oval), colouration ( Hemicypris ovata un-pigmented, Hemicypris megalops with light brown patches), and the eye (larger and more anteriorly positioned in Hemicypris megalops ). Victor & Fernando (1981) noted the following differences: the antennal y3 aesthetasc (present in Hemicypris megalops , and implicitly missing in Hemicypris ovata , but herein this is considered to be an error as both species have this aesthetasc); the antennal Y aesthetasc (relatively longer in Hemicypris megalops ); the rake-shaped organ (with seven teeth in Hemicypris megalops , nine teeth in Hemicypris ovata ; this study found ten in H. megalops and eight in H. ovata ); the mandibular gamma seta (relatively longer in Hemicypris megalops ); the serration on one of the maxillular Zahnborsten (more strongly expressed in Hemicypris ovata ); the number of setae on the terminal segment of the maxillular palp (reported to be five in Hemicypris megalops , but this is an error as both species have six); the h2 seta on the seventh limb (reflexed in Hemicypris megalops ); and the caudal ramus attachment (without a dorsal branch in Hemicypris megalops ). In addition to these characters, this study found that Hemicypris ovata has some longer setae on the appendages, notably, but not restricted to, the alpha seta on the antennule, the h3 seta on the walking leg and the sa seta on the caudal ramus. Features of the appendages that differ between the two species (including setae of noticeably different lengths) are marked with black triangles on Figs 18 & 19 (also see Table 2).

Distribution and ecology. Hemicypris ovata was first reported by Sars (1903) from mud samples collected from Sumatra, Indonesia, although the exact locality is unknown ( Fig. 17 ). It was later reported from the Philippines by Victor & Fernando (1981) on the islands Luzon and Mindanao. Other records are considered to either be incorrect or need confirmation (see above). Sars’ (1903) and Victor & Fernando’s (1981) records correspond to the Tropical rainforest (Af), and Tropical savannah (Aw) Köppen climatic zones ( Peel et al. 2007). Sars (1903) did not specify the type of habitat that the mud samples he studied were from, but Victor & Fernando (1981) recorded this species from ponds and a rice field. Nothing else is known about its ecology.

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 5. Cyprinotus cassidula sp. nov. A, antennule, male (LBM 1430009504). B, antenna, male (LBM 090524-01-014). C, mandibular palp, male (LBM 1430009502). D, alpha, beta and gamma setae of mandibular palp, male (LBM 1430009502). E, mandibular coxa, male (LBM 1430009502). F, maxillula palp and endites (setae on endites not drawn) (LBM 1430009502). G, left fifth limb palp, male (LBM 1430009502). H, right fifth limb palp, male (LBM 1430009502). All specimens from type locality (Table 1, sample 4).

FIGURE 14. A–F, Hemicypris posterotruncata Bate, 1970. A, left valve, external ventral view (LBM 1430009522, sample 14; see Table 1). B, right valve, external ventral view (LBM 1430009522, sample 14). C, left valve, external ventral view, detail of ventral margin (LBM 1430009522, sample 14). D, right valve, external ventral view, detail of ventral margin (LBM 1430009522, sample 14). E, left valve, external ventral view, detail of antero-ventral margin (LBM 1430009522, sample 14). F, left valve, external ventral view, detail of denticles (LBM 1430009522, sample 14). H & I, Hemicypris ovata Sars, 1903. H, whole carapace, left view (paralectotype NHMO F12264c). I, detail of pits on anterior of left valve (paralectotype NHMO F12264c). All specimens female. Scale bar = 500 µm for A, B & H, 141 µm for C–E, 23 µm for F, 84 µm for I.

FIGURE 17. Distribution map of Hemicypris posterotruncata and Hemicypris ovata.? indicates uncertain records. Abbreviations and colours of points refer to Köppen climatic zones, following Peel et al. (2007). Data from: 1, Akindele 2013. 2, Schöning (1994) as Hemicypris sp., identified as H. ovata by Karanovic (2012). 3, Deb (1972a). 4, Deb (1972b). 5, Savatenalinton (2014), Savatenalinton & Suttajit (2014). 6, Sars (1903) (approximate as no specific locality given). 7, Victor & Fernando, 1981. 8, Bate (1970; 1972). 9, Rasouli & Aygen (2017). 10, this study. 11, Kume (2013). 12, Okubo (1990). 13, this study. 14, Tanaka et al. 2015.

FIGURE 18. Hemicypris ovata Sars, 1903. A, antennule. B, antenna. C, antenna, detail of last two segments. D, mandibular coxa. E, maxillula palp and endites (setae on endites not drawn). F, rake-shaped organ. Black triangles indicate features of the appendages that differ from Hemicypris megalops. (All figures female paralectotype specimen NHMO F12264b1.)

FIGURE 19. Hemicypris ovata Sars, 1903, paralectotype (NHMO F12264b1). A, mandibular palp, asterisks indicate setae missing on palp figured, but present on other palp. B, mandibular palp, third segment. C, mandibular palp, fourth segment. D, alpha, beta and gamma setae of mandibular palp. E, fifth limb. F, sixth limb. G, seventh limb. H, caudal ramus. I, caudal ramus attachment. Black triangles indicate features of the appendages that differ from Hemicypris megalops. (All figures female paralectotype specimen NHMO F12264b1.)