Paracobanocythere watanabei, Higashi, Ryouichi & Tsukagoshi, Akira, 2011

Higashi, Ryouichi & Tsukagoshi, Akira, 2011, Four new species of the interstitial family Cobanocytheridae (Crustacea: Ostracoda) from central Japan, Zootaxa 2924, pp. 33-56 : 45-49

Paracobanocythere watanabei sp. nov.

( Figs 11–14 , 15 A)

Type series. Holotype: adult male (SUM-CO-1980), right valve length 250 µm, height 80 µm, left valve length 249 µm, height 82 µm, appendages mounted on slide and valves preserved in a cardboard cell slide, Paratypes: 17 adult males (SUM-CO- 1981–1997) and 6 adult females (SUM-CO- 1998–2003). All illustrated specimens were collected at the type locality on February 10, 2009.

Type locality. Oura, Shimoda City, Shizuoka Prefecture, Pacific coast of central Japan ( Fig. 1 B), 34°40'06"N, 138°56'28"E. Marine littoral beach; sediment composed of clastic coarse sand and granule. Sampling depth approximately 10 cm.

Etymology. This species is named after Mr Satoshi Watanabe, in recognition of his finding of the first individuals of this species.

Diagnosis. Female slightly larger than male. Carapace rounded triangular in anterior view, and upside-down heart shaped in posterior view. Anterior and posterior margin rounded. Approximate number of 65 pore systems per valve. Seven and three marginal pores along anterior and posterior margins, respectively. Three vein-like structures running forward on inner surface of anterior marginal infold. Rib weakly developed behind adductor muscle scars. Male copulatory organ remarkably asymmetric in right and left hemipenes: right one consisting of roundtipped and stick-shaped distal lobe, and triangular tip of capsule; left one consisting of sharply tipped and curved distal lobe, and slenderly extended tip of capsule.

Description. Carapace ( Figs 11 and 12 ). Depressed dorso-ventrally and elongated. Rounded triangular-shaped outline in anterior view and upside-down heart shaped outline in posterior view. External surface smooth. Anterior and posterior margins rounded in lateral view. Ventral area flat. All pore systems of simple type and approximate number of 65 per valve with slight variation in each specimen. Marginal infold broad in anterior area and narrow in posterior area. Three vein-like structures running forward on inner surface of centre of anterior marginal infold. Vestibula occupying most of area in marginal infold. Left valve slightly overlapping right valve along anterior and posterior margins. Hingement of adont type. Four adductor muscle scars in oblique row.

Antennula (Fig. 13A). Five articulated podomeres. First podomere bare. Second podomere three times as long as first podomere, with one medium seta on outside distal end and long setulae along anterior margin. Third podomere half as long as second podomere and bare. Fourth podomere three and half times as long as third podomere, with two long and one medium setae on antero-distal end, one long seta on middle of posterior margin and one long seta on postero-distal end. Fifth podomere half as long as fourth podomere, with one medium seta on inside of distal end and one pair of basally fused setae composed of slender and round-tipped setae.

Antenna (Fig. 13B). Four articulated podomeres. First podomere with two segmented spinneret (exopodite) on outside distal end. Second podomere two-fifths as long as first podomere, with one short seta on postero-distal end. Third podomere twice as long as second podomere, with one short and one very short setae on antero-medial suture and one medium seta on postero-distal end. Fourth podomere one-third as long as third podomere, with claw on antero-distal end and one short and one thick setae on postero-distal end.

Mandibula (Fig. 13C). Coxa long, with one thick seta on antero-ventral part, two setae between first and second anterior coxal endites. Seven coxal endites. Palp consisting of four articulated podomeres. First podomere (basis) with very long seta (exopodite) on outside proximal end and one medium seta on ventro-distal end. Second podomere eleven-tenths as long as first podomere, with one medium seta on ventro-distal end. Third podomere seven-tenths as long as second podomere, with one very long, one long and one medium setae on middle of dorsal margin, one medium and one long seta on ventro-distal end. Fourth podomere two-fifths as long as third podomere, with two long and one medium setae on distal end.

Maxillula (Fig. 13D1, D2). Thin branchial plate (exopodite) with ten plumose setae. Basal podomere with one palp and three endites. Palp consisting of two indistinct podomeres: first podomere with four long setae on dorsodistal end and one long seta on ventro-distal end; second podomere half as long as first podomere, with two long and one medium setae on distal end. Endites: dorsally two with five setae; and ventrally one with four setae.

Fifth limb (Fig. 13E). Four articulated podomeres. First podomere with one short seta on antero-distal end and long seta on postero-proximal part. Second podomere five-thirds as long as first podomere, with one medium seta on antero-distal end. Bare third podomere half as long as second podomere. Fourth podomere nine-tenths as long as second podomere, with stout distal claw.

Sixth limb (Fig. 13F, G). Remarkably reduced leg in male (Fig. 13F): three articulated podomeres; first podomere with one very long seta on middle of anterior margin, one short seta on antero-distal end and one medium seta on middle of posterior margin; second podomere two-thirds as long as first podomere, with one medium seta on antero-distal end; third podomere half as long as second podomere, with one medium seta and undeveloped claw on distal end. Normal walking leg in female (Fig. 13G): four articulated podomeres; first podomere with one short seta on antero-distal end and one medium seta on postero-proximal part; second podomere five-fourths as long as first podomere, with short seta on antero-distal end; third podomere half as long as second podomere; fourth podomere as long as third podomere, with stout distal claw.

Seventh limb (Fig. 13H). Four articulated podomeres. First podomere with one short seta on antero-distal end and one medium seta on postero-proximal parts. Second podomere four-thirds as long as first podomere, with one very short seta on antero-distal end. Third podomere one-third as long as second podomere. Fourth podomere fivefourths as long as third podomere, with one stout distal claw and setulae distally along two-fifths of anterior margin.

Male brush-shaped organ (Fig. 13I). Consisting of two branches, each branch with about 16 setae on distal margin.

Male copulatory organ ( Fig. 14 A, B). Capsule of both hemipenes trapezoidal. Flexible copulatory duct (Cd) very long, more than twice of length of capsule, forming one roll in proximal part. Tip of capsule (Tc) and distal lobe (Dl) remarkably asymmetric in right and left hemipenes. Right organ ( Fig. 14 B): Tc acute-angle triangular; and distal lobe (Dl) round-tipped and stick-shaped. Left organ ( Fig. 14 A): Tc slenderly extended; Dl slender, ventrally curved at half, distally curved as tip and sharply pointed.

FIGURE 13. Appendages of Paracobanocythere watanabei sp. nov. A–D, F, H and I, Holotype (SUM-CO-1980); E, Paratype (SUM-CO-1981); G, Paratype (SUM-CO-1998). A, antennula; B, antenna; C, mandibula; D1, palp and endites of maxillula; D2, branchial plate of maxillula; E, fifth limb; F, sixth limb of male; G, sixth limb of female; H, seventh limb; I, brushshaped organ. Scale bar indicates 50 µm.

Caudal part of female ( Fig. 15 A). Genitalia consisting of rounded frame-work connected to pouch with long duct. Caudal rami near genitalia, with two setae on anterior and posterior parts, respectively. Caudal process covered with setulae.

Eye. Present.

Dimensions. See Table 3.

Length (µm) Height (µm)

Mean Observed range N Mean Observed range N Male Right valve 241 236–250 10 75 72–80 10

Left valve 246 240–254 11 78 67–82 11 Female Right valve 251 246–259 3 84 81–86 3

Left valve 256 252–266 4 85 81–89 4

Occurrence. So far known only from type locality.

Remarks. This new species resembles Paracobanocythere hawaiiensis in the morphologies of carapace and appendages. Paracobanocythere watanabei sp. nov., however, can be distinguished from P. ha w a i ie ns i s by the following features: seven and three marginal pores on anterior and posterior margins, respectively; no seta on the middle of anterior margin of antennular fourth podomere; a seta on the ventro-distal corner of first podomere of mandibular palp; clearly segmented male sixth limb. Moreover, the morphology of the left male copulatory organ is different between P. watanabei sp. nov., and P. hawaiiensis : the Tc is gently curved in the new species but it is strongly curved at the tip in P. h a w a i i e n s i s; the Cd is forming a roll in proximal part in the new species but it is not so in P. ha w a i ie ns is. The right male copulatory organ of P. hawaiiensis was not shown in its original description in Gottwald (1983).

Figures

FIGURE 1. Study area. A, map of Japan; B, sampling sites.

FIGURE 11. Carapaces of Paracobanocythere watanabei sp. nov. A – K, male specimens: A, Paratype (SUM-CO- 1983); B, Paratype (SUM-CO- 1984); C, D, I – K, Paratype (SUM-CO- 1985); E, Paratype (SUM-CO- 1986); F, Paratype (SUM-CO- 1987); G, Paratype (SUM-CO- 1988); H, Paratype (SUM-CO- 1989). A, left external lateral view; B, right external lateral view; C, internal view of left valve; D, internal view of right valve; E, dorsal view; F, ventral view; G, anterior view; H, posterior view; I, adductor muscle scars of left valve; J, hingement of left valve; K, hingement of right valve. L – O, female specimens: L and M, Paratype (SUM-CO- 1999); N and O, Paratype (SUM-CO- 2000). L, left external view; M, right external view; N, internal view of left valve; O, internal valve of right valve. Scale bar indicates 150 μm for A – H and L – O, 50 µm for I, and 100 µm for J and K, respectively.

FIGURE 12. Carapaces of Paracobanocythere watanabei sp. nov. A and B, Holotype (SUM-CO- 1980). A, left external view; B, right external view. Each of the carapace structures are transmitted images. Scale bar indicates 100 µm.

FIGURE 14. Male copulatory organs of Paracobanocythere watanabei sp. nov. A and B, Holotype (SUM-CO- 1980). A, external view of left organ; B, external view of right organ. Copulatory ducts are shaded. Abbreviation: Tc, tip of capsule; Dl, Distal lobe. Scale bar indicates 50 µm.

FIGURE 15. Caudal part of female. A, Paracobanocythere watanabei sp. nov., right lateral view (Paratype, SUM-CO- 2001); B, Paracobanocythere grandis sp. nov., left lateral view (Paratype, SUM-CO- 2017). Scale bars indicate 50 µm.