Vestalenula sp.

Smith, Robin James & Chang, Cheon Young, 2022, Two new species of non-marine Ostracoda (Crustacea) of the genera Vestalenula Rossetti & Martens, 1998 (Darwinuloidea) and Microloxoconcha Hartmann, 1954 (Cytheroidea) from Tsushima, Japan, and a summary of the non-marine ostracod fauna of the island, Zootaxa 5150 (4), pp. 529-555 : 539-541

Vestalenula sp.

( Figs 3I–J & 5 )

JAPAN — Nagasaki Prefecture, Tsushima • 2 ♀♀, with soft parts dissected in glycerine and sealed in glass slides, valves stored dry in micropalaeontological slides; Mitsushima-machi Sumo ; 34.26246º N, 129.26264º E; alt. 58 m; 31 Aug. 2019; Robin J. Smith, Cheon Y. Chang, Jimin Lee leg.; stream in forest, cobbles, pebbles, gravel, interstitial sample; sample 190831-01. • 1 ♀; Izuhara-machi Tsutsu, Ayumodoshi Natural Park; 34.1552º N, 129.21647º E; alt. 95 m; 31 Aug. 2019; Robin J. Smith, Cheon Y. Chang, Jimin Lee leg.; seep, mud and organic detritus, including leaf litter, at side of path in forest; sample 190831-05 .

Brief description

Carapace length 385–414 µm, height 196–199 µm (n=2). Lateral view, dorsal and ventral margins straight and parallel, posterior margin evenly rounded, anterior margin with maximum curvature below mid-height ( Fig. 3I ). Adductor muscle scars with seven scars arranged in rosette. Right valve with large and well-developed keel near postero-ventral margin, length about one-third length of valve ( Fig. 3J & K ). Surface with slight pitting in central ventral and postero-dorsal areas. Colour translucent white.

Very small pigmented eye present.

Antennule with six segments ( Fig. 5A ). First segment with short, subapical-dorsal seta. Second segment with one long and one medium-length subapical-ventral setae. Third segment with apical-ventral seta and apical-dorsal seta. Fourth segment with short apical-ventral seta and tiny subapical seta. Fifth segment with two medium-length, stout apical-ventral setae, two longer apical-dorsal setae, and tiny subapical seta. Terminal segment with one long, one medium-length and one tiny setae and aesthetasc ya.

Antenna, first endopodal segment with one long, robust, and one short and slender sub-apical ventral setae ( Fig. 5B ). Fourth segment with short z1 claw, approximately 60% as long as G2 and G3 claw. Claw G1 very short, z2 tiny. Terminal segment with short GM claw, about 41% length of Gm.

Sixth limb five-segmented with very short d1 seta and two d2 setae on first segment ( Fig. 5C ). Second segment with two e setae and long pd seta, latter extending to just beyond end of third segment. Third and fourth segments with robust f and g setae respectively. Terminal segment with robust, claw-like h1 seta, about 55% length of claw h2, and short, robust h3 seta.

Caudal ramus consisting of sub-triangular base supporting one short claw ( Fig. 5D ). Posterior of body with small and rounded protrusion, interpreted as small post-abdomen, with dorsal seta.

Remarks. This is an undescribed species, but as only three specimens were recovered, one of which has a damaged carapace, it is left in open nomenclature. The posterior of the body ends with a small, rounded protrusion, which we interpret as a post-abdomen, albeit smaller than other examples in the genus. The protrusion has a dorsal seta, which has been reported on the post-abdomens of other species ( Table 3), supporting this view. The long keel on the right valve indicates that Vestalenula sp. belongs to the danielopoli -group of Vestalenula (species with a short keel belong to the boteai -group; see Rossetti & Martens 1998). Although the carapace shape is similar to V. cornelia , the presence of an apical-ventral seta on the third segment of the antennule, and two setae, one large, one much shorter, on the apical-ventral corner of the first endopodal segment of the antenna distinguishes it from all other Vestalenula found in Japan ( V. cornelia , V. cylindrica , Vestalenula gravata sp. nov., V. lundi and V. molopoensis ) ( Fig. 5A & B , additional setae marked with black triangles, Table 3). Three species from Brazil, Vestalenula botocuda Pinto et al., 2003 , Vestalenula irajai Pinto et al., 2003 and Vestalenula pagliolii ( Pinto & Kotzian, 1961) , also have two setae on the third segment of the antennule and first endopodal segment of the antenna, but these species have very short keels, thus belong to the boteai -group ( Table 3).

Distribution and ecology. This species was found twice. The first locality (Mitsushima-machi Sumo) is a small, shallow stream in a forest on the lower slopes of a mountain. The sediment was very poorly sorted and angular consisting of cobbles, pebbles and gravel, with specimens found interstitially. The second locality (Ayumodoshi Natural Park) is a seep at the side of a path in a forest, with a substrate of mud and organic detritus, including leaf litter.

Figures

FIGURE 3. A–H, Vestalenula gravata sp. nov. A, LV, ext. (LBM 1430009558). B, LV, int. (LBM 1430009558). C, RV, int. (LBM 1430009557).D, RV, oblique int.(LBM 1430009557).E, Cp, dor., anterior to right (LBM 1430009559). F, RV vent. (LBM 1430009557). G, Cp, vent., anterior to left (LBM 1430009559). H, adductor muscle scars, anterior to left (LBM 1430009557). I–K, Vestalenula sp. I, LV, ext. J, RV, int. K, RV, vent. Scale bar = 200 µm for A–G, I–K, 46 µm for H.

FIGURE 5. Vestalenula sp. A, antennule. B, antenna. C, sixth limb. D, caudal ramus and posterior of body. Black triangles indicate setae not present in some other Vestalenula.