Hemicypris megalops 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 : 18-22

Hemicypris megalops Sars, 1903

( Figs 4C , 8 , 9 )

1903 Hemicypris megalops, G. O. Sars , n. sp. —Sars: 27–28, pl. III figs 3a–b.

1906 megalops Sars—Vávra : 424.

1910 Cyprinotus (Hemicypris) megalops (Sars) —Daday: 182.

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

1932 Heterocypris megalops —Klie: 471, 499.

1937 megalops —Klie: 3.

?1938 Heterocypris megalops G. O. Sars [sic]—Klie: 23, 27 (fide herein).

1955 H. megalops Sars—Howe : 88.

? 1966 Hemicypris megalops Sars, 1903 —McKenzie: 265–266, fig. 2g–k (fide herein).

1970 Hemicypris megalops Sars—Bate : 294.

? 1972a Cyprinotus megalops (Sars) —Deb: 234, 238–240, text-fig. 1 (fide Victor & Fernando 1981).

1974 Heterocypris megalops Sars [sic]—Purper & Würdig-Maciel: 72, 73.

1976 Hemicypris megalops Sars—Victor & Fernando : 1809.

? 1977 Hemicypris megalops Sars—Jain : 356, 357, pl. 1, 3a–b (fide herein).

1978 Hemicypris megalops Sars, 1903 —De Deckker & Jones: 125.

1978 Hemicypris megalops Sars—Victor & Fernando : 417.

1979 Hemicypris megalops Sars—Victor & Fernando : 187.

? 1979 H. megalops —Williams: Table 1 (fide herein).

1980 Hemicypris megalops Sars, 1903 —Hanai et al.: 127–128.

1980 Hemicypris megalops Sars, 1903 —Victor & Fernando: 958, 959.

1981 Hemicypris megalops Sars, 1903 —Victor & Fernando: 11, 15–17, 21, 24, figs 30–40.

non 1981 Hemicypris megalops Sars, 1903 —Battish: 652, fig. 5 (fide herein).

1982 Hemicypris megalops Sars 1903 —Victor & Fernando: Table 1

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

1987 Hemicypris megalops ( Sars, 1903) [sic]—Forró et al.: 49.

1997 Hemicypris megalops (G. O. Sars, 1903) [sic]—Yin & Martens: Appendix.

2001 Hemicypris megalops Sars, 1903 —Bhatia et al.: 511, pl. 1: 1 & 2.

non 2004 Hemicypris megalops Sars, 1903 —Okubo: 26, figs 11i–l (fide herein).

2005 Hemicypris megalops —Prasad et al.: 185.

2008 Hemicypris megalops Sars—Bhandari & Kundal : 153.

2008 Hemicypris megalops Sars, 1903 —Savatenalinton & Martens: 17, 18, 20, 22, table 1.

2009 H. megalops Sars, 1903 b—Yu et al.: 37.

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

2012 H. megalops Sars 1903 a—Karanovic: 439, 441.

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

2013 Hemicypris megalops —Nath: 15.

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

2014 H. megalops Sars, 1903 —Mohammed et al.: 26.

? non 2014 Hemicypris megalops Sars, 1903 —Yu: 125–126, figs 68 & 69 (fide herein).

2015 Hemicypris megalops sars [sic]—Nath: 34, 35, table 1.

? non 2015 Hemicypris megalops Sars, 1903 —Tanaka et al.: 33, figs 2F, 3K & L, 5E, 8B & C, table 2 (fide herein).

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

2017 Hemicypris megalops Sars, 1903 —Khosla et al.: 77, 86, 88, plate 1, 8–10.

2017 Hemicypris megalops Sars, 1903 —Rasouli & Aygen: 428.

2018 Hemicypris megalops ( Sars 1903) [sic]—Khosla & Lucas: 12.

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

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

Diagnosis. Carapace, anterior and posterior margins about equally rounded, ventral margin slightly convex, maximum height at about mid-length. Left valve with marginal denticles along postero-ventral and antero-ventral to central anterior margins ( Sars 1903). Antennal aesthetasc Y 24% length of dorsal sclerotised margin of first endopodal segment, swimming setae long, reaching beyond ends of claws. Female antenna: claw G2 long, ca. 83% length of claw G1, claw Gm slender and long, ca. 70% length of GM. Mandibular gamma seta short and triangular, with wide base and long, stiff setules distally. Maxillula third endite with one smooth and one lightly serrated Zahnborsten. Sixth limb first segment with d1 seta, second segment with e seta reaching beyond distal end of third segment, third segment with f seta reaching to distal end of fourth segment. Seventh limb (cleaning limb) with seta dp on first segment longer than d1 and d2 of same segment, second segment with long e seta, not reaching to distal end of third segment. Terminal pincer organ rounded and compact. Caudal ramus with claw Ga noticeably larger than claw Gp, both claws slender, seta sp about as long as claw Gp.

Material examined. Paralectotypes. INDONESIA • 1♀, dissected in glycerine in a sealed slide; Sumatra; NHMO F12292 c2. • 1♀, dissected in glycerine in a sealed slide; Sumatra; NHMO F12292 c3.

Both paralectotypes were in very poor condition, with completely decalcified, soft valves. Paralectotype F12292c2 appeared to retain the original shape of the carapace in lateral view, while for paralectotype F12292c3 the valves were clearly deformed. Both specimens were dissected and the remains of the decalcified valves kept with the appendages in dissection slides .

Description. Carapace (description based on decalcified paralectotype F12292c2 before dissection). Length 864 µm, height 536 µm. Right valve larger than left, overlapping along all margins ( Fig. 4C ). Lateral view, carapace anterior and posterior margins about equally rounded. Dorsal margin slightly angular at maximum height (approximately mid-length) and at postero-dorsal margin. Ventral margin slightly convex. No other features can be documented due to poor preservation.

Antennule with seven articulated segments ( Fig. 8A ). First segment large, possibly with tiny Wouters organ on proximal part of dorsal margin, one seta on dorsal margin approximately mid-length, and two long setae near apical-ventral corner. Second segment wider than long, with one seta on apical-dorsal corner, and tiny bottle-shaped Rome organ on ventral margin. Third segment longer than wide, with one seta on apical-dorsal corner and one very 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 and one short (alpha) apical setae; alpha seta 1.8 times length of 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 one-third length of longest seta, and short seta ( Fig. 8B ). Aesthetasc Y 24% length of dorsal sclerotised margin of first endopodal segment (marked with dotted arrowed line on Fig. 8B ). Swimming setae long, reaching beyond ends of claws. Setae t2–3 relatively long, reaching beyond mid-length of claws, t1 and t4 shorter ( Fig. 9A ). Claw G2 long, ca. 83% length of claw G1. Claw Gm slender and long, ca. 70% length of GM. N.B. Claw G3 of the antennae of the specimens dissected for this study appear truncated (worn) distally. Therefore in other specimens this claw maybe slightly longer.

Mandible palp, first segment with small, slender alpha seta, tapering distally to setule-like distal end ( Fig. 8C & F ). Second segment 3+1+beta setae on inner edge, and three setae on outer edge. Beta seta setulous, longer than alpha. 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. 8D & F ). Gamma seta elongate and triangular and with long, stiff setules distally. Terminal segment with three stout claw-like setae and three thinner setae ( Fig. 8E ). Mandibular coxa with well developed teeth, typical of family ( Fig. 8G ).

Rake-shaped organ with 10 teeth distally ( Fig. 8H ).

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. 8I ). 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 lightly serrated Zahnborsten.

Fifth limb (maxilliped) female, basis with two short a setae (not shown on Fig. 9B ), and long d and b setae; c seta missing, typical of subfamily ( Fig. 9B ). Endite with ca. 14 apical setae. Exopodite (branchial plate) with six rays. Palp with three apical setae, one long, and two much shorter.

Sixth limb (walking leg) robust with five articulated segments ( Fig. 9C ). First segment with hirsute d1 seta. Second segment with e seta reaching to distal end of third segment. Third segment with f seta reaching to almost distal end of fourth segment. Fourth segment with two g setae, one relatively long and one tiny. Fifth segment with h1 longer than h3, and h2 claw long and robust.

Seventh limb (cleaning limb) with seta d1 on first segment slightly longer than d2, seta dp of same segment noticeably longer than both d1 and d2 ( Fig. 9D ). 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 and rounded ( Fig. 9E ). In three of four seventh limbs studied herein h2 reflexed (i.e. pointing down along limb), in other obscured.

Caudal ramus with claw Gp 66% length of claw Ga. Seta sp long, 87% length of claw Gp ( Fig. 9F ). Seta sa slender and relatively long, 33% length of claw Ga. Caudal ramus attachment sinuous, noticeably more curved distally ( Fig. 9G ).

Males were reported from India ( Deb 1972a), but Victor & Fernando (1981) suggested that this record needs to be re-examined.

Remarks. The paralectotypes studied herein were decalcified, and so the carapace morphology of the Sumatran material is not clearly known. This issue cannot be resolved until fresh material is collected from Sumatra. There are no marginal denticles visible in the paralectotypes, but this is most likely due to the decalcified condition of the valves, as both Sars (1903) and Victor & Fernando (1981) recorded them. Sars (1903) named the species megalops based on the large size of the eye. In the paralectotypes studied herein the eye is well developed but not overly large compared with other Hemicypris species ( Fig. 4C ). Victor & Fernando (1981) figured the cleaning limb of this species with a compact, rounded terminal end and with h2 reflexed (curved claw of Victor & Fernando 1981). In the material examined herein, the cleaning limb was of a similar morphology, distally compact and rounded and with a reflexed h2 seta. This is an unusual feature for the subfamily (usually the h2 seta projects out distally and the pincer is well defined) and could potentially be a useful character to recognise this species. However, this is based on maybe only three specimens (two examined for this study, and one (?) examined by Victor & Fernando (1981)), so more material should be checked to determine the nature of this character.

Hemicypris megalops has been reported from Japan ( Okubo 2004; Tanaka et al. 2015), but these records are considered to either represent Hemicypris kibiensis or possible occurrences of Hemicypris posterotruncata (see below). Other living and fossil records of this species cannot be readily assessed as details of the carapace are not sufficiently known. McKenzie’s (1966) record of Hemicypris megalops from Australia was based on A-1 instars; this record therefore has to be questioned as juveniles are not sufficient for reliable species determination. The carapace of Hemicypris megalops reported from China by Yu (2014) appears to be covered in pits all over (pits have not been reported for Hemicypris megalops ), and both Zahnborsten are smooth, suggesting that this may be a different species. Figures of Indian fossil specimens ( Bhatia et al. 2001; Khosla et al. 2017) differ from each other suggesting that they are not conspecific. Klie‘s (1938) record from Taiwan was not accompanied with figures, so cannot be confirmed.

Distribution and ecology. Sars (1903) first described this species from Sumatra, Indonesia (exact locality not recorded), and later it was reported from East and West Malaysia, and Sulawesi and Kalimantan, Indonesia ( Victor & Fernando 1981) ( Fig. 10 ). Other records from Japan, China, India and Australia need confirmation (see above). South East Asian records all lie in the tropical rainforest (Af) Köppen climatic zone ( Peel et al. 2007). Hemicypris megalops has been reported mostly from rice fields, but also ponds ( Victor & Fernando 1981).

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 8. Hemicypris megalops (Sars, 1903), paralectotypes (NHMO F12292c). A, antennule (paralectotype F12292c3). B, antenna (paralectotype F12292c2). C, mandibular palp, asterisk indicates seta missing on palp drawn, but present on other palp (paralectotype F12292c2). D, mandibular palp, third segment (paralectotype F12292c2). E, mandibular palp, fourth segment (paralectotype F12292c2). F, alpha, beta and gamma setae of mandibular palp (paralectotype F12292c3). G, mandibular coxa (paralectotype F12292c3). H, rake-shaped organ (paralectotype F12292c3). I, maxillula palp and endites (setae on endites not drawn) (paralectotype F12292c2). All specimens female.

FIGURE 9. Hemicypris megalops (Sars, 1903), paralectotype (NHMO F12292c2), female. A, antenna, detail of last two segments. B, fifth limb. C, sixth limb. D, seventh limb. E, seventh limb, detail of terminal segment. F, caudal ramus. G, caudal ramus attachment.

FIGURE 10. Distribution map of Hemicypris megalops and Hemicypris kliei.? indicates uncertain records. Abbreviations and colours of points refer to Köppen climatic zones, following Peel et al. (2007). Data from: 1 & 2, Deb (1972). 3, Bhatia et al. (2001). 4, Khosla et al. 2017. 5, Sars (1903) (approximate as no specific locality given). 6, Victor & Fernando, 1981. 7, Klie (1938) (no figures). 8, Yu (2014). 9, McKenzie (1966). 10, Schöning (1994), Pachur & Wünnemann (1996). 11, Carbonel & Peypouquet (1979). 12, Martens (1990). 13, Lindroth (1953). 14, this study. 15, Cohen et al. 2013.