Parvocythere gottwaldi, Higashi, Ryouichi & Tsukagoshi, Akira, 2012

Higashi, Ryouichi & Tsukagoshi, Akira, 2012, Two new species of the interstitial genus Parvocythere (Crustacea, Ostracoda, Cytheroidea) from Japan: an example of morphological variation, ZooKeys 193, pp. 27-48 : 28-34

Parvocythere gottwaldi sp. n. Figs 2-6

Type series.

Holotype: adult male (SUM-CO-2023), right valve length 173 µm, height 88 µm, left valve length 174 µm, height 84 µm, appendages mounted on slide and valves preserved in a cardboard cell slide, Paratypes: 14 adult males (SUM-CO-2024-2037) and 12 adult females (SUM-CO-2038-2049). All illustrated specimens were collected from interstitial pore-water at the type locality on October 10, 2008.

Type locality.

Daio-zaki, Shima City, Mie Prefecture, Pacific coast of central Japan, 34°16.59'N, 136°53.83'E (Fig. 1B), in sediments at approximately 20 cm depth. The sediment is mainly composed of clastic very coarse sand and granules.

Etymology.

This species is named in honour of Dr Jochen Gottwald, in recognition of his significant contribution to our knowledge of interstitial ostracods.

Diagnosis.

Carapace rounded trapezial in lateral view with very slight protrusion on antero-ventral area and sharp wrinkle-like groove running from middle to posterior in ventral area of both valves. Tapering anterior margin. Forty-two pore systems per valve. Seven and four marginal pores along anterior and posterior margins, respectively. Marginal infold broad in anterior but very narrow in posterior. Hingement modified pentodont type. No suture on middle of fourth podomere of antennula. Antenna with only one distal claw. Male copulatory organ asymmetric, with left organ (hemipenis) larger than right one. Left hemipenis bearing long copulatory duct single coiled in distal part, short and stout claw-like dorsal ramus, two-pronged ventral ramus, and well-developed crescent-shaped distal lobe with thick seta on centre of proximal part. Right organ reduced and bearing much reduced copulatory duct and crescent-shaped distal lobe with thick seta on proximal part.

Description.

Carapace (Figs 2 and 3). Carapace rounded trapezial in lateral view with very slight protrusion on antero-ventral area and sharp wrinkle-like groove running from middle to posterior in ventral area of both valves. Anterior margin tapers more than posterior margin. Dorsal margin slightly rounded. Ventral margin almost straight. Carapace surface generally smooth. All pore systems of simple type and 42 per valve. Seven and four marginal pores along anterior and posterior margins, respectively. Marginal infold broad in anterior area but very narrow in posterior area. Vestibula occupying large part of marginal infold. Inner surface covered with numerous pits. Hingement modified pentodont type. Right valve slightly overlapping left valve along hinge line. Four adductor muscle scars in oblique row. Mandibular scar visible beneath frontal scar.

Antennula (Fig. 4A). Five articulated podomeres. First podomere bare and short. Second podomere nine quarters as long as first podomere, with fine setae along antero-distal margin. Third podomere half as long as second podomere, with one medium seta on antero-distal end. Fourth podomere as long as third podomere, with two long setae on antero-distal end and one long seta on postero-distal end. Fifth podomere half as long as fourth podomere, with one long and one very long simple setae and one spatula-like long seta on distal end.

Antenna (Fig. 4B). Four articulated podomeres. First podomere with two segmented spinneret (exopodite) on distal end. Second podomere half as long as first podomere, with bunch of fine setae along middle of anterior margin and one medium seta on postero-distal end. Third podomere eight-thirds as long as second podomere, with numerous fine setae along antero-proximal margin, medium setae on middle of anterior margin and on middle of posterior margin, respectively, and one medium setulous seta on postero-distal end. Fifth podomere quarter length of fourth podomere, with numerous fine setae on distal margin and one stout claw on distal end.

Mandibula (Fig. 4C1, C2). Coxa (Fig. 4C1) elongated, with one medium seta on antero-ventral part. Six coxal endites. Palp (Fig. 4C2) consisting of four articulated podomeres. First podomere (basis) with bifurcated lamella (exopodite) on middle of dorsal margin. Second podomere two-thirds as long as first podomere, with three medium setae on ventro-distal end. Third podomere five-fourths as long as second podomere, with one stout medium seta on outside of distal end and one medium seta on ventro-distal end. Fourth podomere two-fifths as long as third podomere, with four setae on distal end.

Maxillula (Fig. 4D and E). Thin branchial plate (exopodite; Fig. 4E) with approximately nine plumose setae. Basal podomere with one palp and three endites (Fig. 4D). Palp consisting of two articulated podomeres: first podomere with one long and one medium seta on antero-distal end; second podomere eleven-tenth as long as first podomere, with one medium seta on middle of posterior margin and two medium setae on distal end. Endites with three setae, respectively.

Fifth limb (Fig. 4F). Four articulated podomeres. First podomere with two short setae on antero-distal end. Second podomere five-sixths as long as first podomere, with one medium seta on antero-distal end. Third podomere four-fifths as long as second podomere. Fourth podomere three-halves as long as third podomere, with stout distal claw.

Sixth limb (Fig. 4G). Four articulated podomeres. First podomere with one short seta on antero-distal end. Second podomere four-fifth as long as first podomere, with one long seta on antero-distal end. Third podomere as long as second podomere. Fourth podomere seven-fifth as long as third podomere with stout distal claw.

Seventh limb. Absent.

Male copulatory organ (Fig. 5). Asymmetric. Right organ (Fig. 5B) smaller than left (Fig. 5A), with reduced components: square capsule with weakened framework; copulatory duct (Cd) extremely reduced; distal lobe (Dl) thin and crescent-shaped with thick seta on proximal part. Left organ bearing well-developed long copulatory duct (Cd) single coiled in distal part; short and stout claw-like dorsal ramus (Dr); two- pronged ventral ramus (Vr); and crescent-shaped distal lobe (Dl) with thick seta on centre of proximal part.

Genitalia of female (Fig. 6). Almost symmetric and consisting of rounded frame-work and winding duct with vesicle-like joint nearby opening. Duct opening on ventral side.

Eye. Absent.

Dimensions.

See Table 1.

Occurrences.

Type locality and Kozu, Odawara City, Kanagawa Prefecture, Pacific coast of central Japan (35°16.73'N, 139°12.75'E).

Remarks.

Parvocythere gottwaldi sp. n. resembles Parvocythere mauiensis Hartmann, 1991 in the outline of carapace. The new species, however, can be distinguished from the other species by its antenna with only one distal claw and the asymmetric male copulatory organ. Although this new species is also similar to Parvocythere spec. A, as referred to in Gottwald (1983), in the characteristics of antenna and asymmetric male copulatory organ, the new species can be distinguished from Parvocythere spec. A by the tapering anterior margin of carapace and the copulatory duct (Cd) single coiled in the distal part.