Undulacandona spinula, Smith, Robin J., 2011

Smith, Robin J., 2011, Groundwater, spring and interstitial Ostracoda (Crustacea) from Shiga Prefecture, Japan, including descriptions of three new species and one new genus, Zootaxa 3140, pp. 15-37 : 28-33

publication ID	https://doi.org/ 10.5281/zenodo.207945
DOI	https://doi.org/10.5281/zenodo.6185481
persistent identifier	https://treatment.plazi.org/id/03EE4061-BE4A-700D-ACAD-E236FB83FA36
treatment provided by	Plazi
scientific name	Undulacandona spinula
status	sp. nov.

Treatment

Undulacandona spinula n. sp.

( Figs 9A–E View FIGURE 9. A – E , 10 View FIGURE 10 , 11 View FIGURE 11 )

Material examined. Five males and three females from a domestic well in Kyomachi 3-chome, Otsu, Shiga Prefecture, N35º 00’ 28”, E135º 51’ 49”, 6 October 2007, collected by Mark J. Grygier.

Etymology. From the Latin spinula , meaning a thorn, and referring to the thorn-like a lobe of the male sexual organ.

Type locality. Kyomachi 3-chome, Ostsu, Shiga Prefecture, Japan, N35º 00’ 28”, E135º 51’ 49”. Type material collected from a well lined with cemented stones inside an old house. Dimensions of well: 0.7 m diameter, 4 m to water surface, water 1.1 m deep.

Type material. Holotype: dissected male ( LBM 1430005085). Allotype: dissected female ( LBM 1430005086). Paratypes: dissected male ( LBM 1430005087), dissected female ( LBM 1430005088), whole male carapace ( LBM 1430005089), whole female carapace ( LBM 1430005090).

Diagnosis. Male carapace sub-rectangular in lateral view, dorsal view with posterior and anterior ends compressed and pointed. Female sub-triangular in lateral view. Surface of carapace with fine longitudinal striations in both sexes. An1 with six segments, the first two of which are partially fused. Male antenna with well developed sexual bristles, t2 terminating in a large, round disc. Hp with lobe a twice as long as lobe h. CR partially reduced, stout and curved. Claws Ga and Gp sub-equal in length. Setae Sa and Sp very small.

Description. Carapace length 707–756 µm, height 344–356 µm. Male carapace sub-rectangular in lateral view, ventral margin straight, dorsal margin straight in central part, sloping towards anterior and posterior margins ( Fig. 9A View FIGURE 9. A – E ). Anterior and posterior margins equally rounded. Left valve overlaps right along dorsal and ventral margins. Female carapace with less inflated posterior margin compared with male, and dorsal margin sloping down to anterior and posterior margins at a steeper angle ( Fig. 9B View FIGURE 9. A – E ). Dorsal view narrow, pointed at both ends, maximum width about mid-length ( Fig. 9C View FIGURE 9. A – E ). Surface of valves covered in horizontal striations, more strongly defined in female compared with male ( Figs 9D, E View FIGURE 9. A – E ). Fused zone relatively wide along anterior and posterior margins, with numerous radial pore canals anteriorly, fewer posteriorly. Calcified inner lamella approximately twice as wide anteriorly than posteriorly ( Fig. 10 View FIGURE 10 A). Adductor muscle scars indistinct. Hinge adont. Colour translucent white.

An1 ( Fig. 10 View FIGURE 10 B) six segmented, with the first two segments partially fused to produce one, elongate segment, possibly with some articulation between them. Dorsal margin of first segment with one robust seta at apical end. Second segment with two, long setae on apical ventral corner. Third segment with one apical-dorsal seta. Fourth segment elongate with one apical seta. Fifth segment elongate with three, long apical setae. Final segment small and elongate with long y a aesthetasc, two long and one short apical setae.

An2 ( Fig. 10 View FIGURE 10 C–E) exopodite consisting of rounded base with three short setae. Y aesthetasc long and slender. Male with divided second endopodal segment, with two male bristles, t2 and t3. Male bristle t2 very thick and stout, approximately reaching to end of final segment, terminating with large, thin, flattened disc structure. Male bristle t3 stout, but thinner than t2, curved, reaching to proximal half of final segment, and with bifurcated end (i.e. small projection on inner edge near tip). Male t4 seta very small. Female An2 with claw G2 equal in length to G1 and G3. Claw Gm slender and just over half length of claw GM. Seta z3 not observed in either of the two dissected females; it is unclear whether it is absent or obscured by z2.

Md palp ( Fig. 10 View FIGURE 10 F) four segmented, first segment with reduced setulous s2 seta and short, slender alpha seta, together with long setulous s1 seta and one long seta on inner edge. Second segment with group of three long setae, accompanied by small, slender beta seta and one slightly offset long seta (3+1+beta) on inner edge, and two setae on outer distal corner. Third segment with three subapical setae on outer edge, and three stout setae and one short seta on apical edge. Final segment with two long stout setae towards apical outer edge, and three apical, slender, shorter setae on inner edge. Coxa ( Fig. 10 View FIGURE 10 G) well-developed with approximately seven teeth on endite.

Mx ( Fig. 10 View FIGURE 10 H) consisting of three endites and two-segmented palp (endopodite). First palp segment with three apical setae on outer corner, and one apical seta slightly offset towards inner edge. Final segment slightly elongated, terminating with three long stout setae, and three shorter, more slender setae.

Female L5 ( Fig 11 View FIGURE 11 A) with one a seta on basis. Number of rays on branchial plate not observed. Endite with d seta and approximately 12 apical setae. Palp short and stubby, with three short terminal setae of sub-equal length. Male palps ( Figs 10 View FIGURE 10 I, J) with fused terminal hooks, slightly asymmetrical. Palps slightly taper distally to long, curved hooks.

L6 ( Fig. 11 View FIGURE 11 B) very long and slender, with five segments. First and second segments with no setae. Third and fourth segments with short f and g setae respectively. Final segment with tiny h3 seta, short h1 seta and long, slen- der h2 claw.

L7 ( Fig. 11 View FIGURE 11 C) with four segments, first of which bears d1, d2 and dp setae of approximately equal length. Second segment with no setae. Third segment with small g seta. Final segment terminated with short h1 seta, a slightly longer and claw-like h2 seta, and a very long, reflexed h3 seta, approximately as long as the second and third segments combined.

CR ( Fig. 11 View FIGURE 11 D) short and stout and strongly curved, with wide proximal base tapering distally. Claws Ga and Gp similar in length and slightly sinuous. Seta Sa tiny, seta Sp very short and located approximately at one-third the length of ramus from distal end.

Hp ( Fig. 11 View FIGURE 11 E) basal capsule elongated, roughly quadrilateral in shape, widening distally, with rounded distal inner corner. Distally with two lobes, one slender and long, tapering distally to hook, one much shorter with rounded end.

Zenker organ ( Fig. 11 View FIGURE 11 F) relatively small, with wide central tube. Internally with three rosettes. Anterior end plate rounded, large and bulbous. Posterior end plate sub-triangular funnel-shaped, leading to distal section of vas deferens.

Remarks. This species and genus is so far only known from the type locality. The morphology of Undulacandona spinula n. gen. & n. sp. is unusual for the Candoninae in several respects. If male bristles on the antennae are present in Candoninae species, they are usually thickened and stout, often with a sub-triangular end (e.g. Fabaeformiscandona okuboi Smith & Janz, 2008 ), or with a tiny disk-like projection (e.g. Fabaeformiscandona condylea Smith & Janz, 2008 and Fabaeformiscandona pedana Smith & Janz, 2008 ). However, the male t2 bristle of Undulacandona spinula n. gen. & n. sp. terminates with a very large, flattened disk, and the t3 bristle is bifurcated near its distal end.

The Zenker organ is also unusual in that it has only three internal rosettes (typically five in the family), has a wide central tube (typically narrow in the subfamily), and the anterior end is inflated and rounded while the posterior end is funnel shaped (typically both ends are morphologically similar and flattened in the subfamily). The Zenker organ of Undulacandona spinula n. gen. & n. sp. is similar to that of the Lake Baikal Candoninae Pseudocandona inaequivalvis baikalensis ( Bronshtein, 1947) (see Danielopol 1982), and some Paracypridinae (e.g. Paracypria inujimensis ( Okubo, 1980) , and Mangalocypria appendix Wouters, 1998) (see Wouters 1998; Smith and Kamiya 2003). This suggests that the Zenker organ of Undulacandona spinula n. gen. & n. sp. may have a mixture of plesiomorphic characters (i.e. the anterior and posterior end plates) and an apomorphic character (i.e. the reduced number of internal rosettes).

The seventh limbs of Undulacandona spinula n. gen. & n. sp. are large, and in whole specimens these limbs are often seen protruding from the posterior and postero-dorsal margins of the carapace ( Fig. 12 View FIGURE 12 ). Observations of living material reveal that these limbs have a locomotory function, pushing against sediment on the postero-dorsal side of the animal. The caudal rami, in contrast, are reduced, and appear not to be able to protrude to any significant degree from the carapace, and therefore probably have little or no locomotory function.