Xystodesmus keramae, Korsós & Nakamura, 2025

Xystodesmus keramae sp. nov.

Figs 2 A – D View Figure 2 , 16 B View Figure 16

Type material.

Holotype: • male, Japan, Central Ryukyus, Okinawa Pref., Okinawa Group, Aka-jima Isl., Mt. Ootake , shrine, 120 m a. s. l., mixed forest, 26°12'08.6"N, 127°16'32.5"E, 24 September 2010, leg. Z. Korsós ( NSMT -My 535 ) GoogleMaps . Paratypes: • 1 male, 2 females ( NSMT -My 536 ), 1 male, 2 females ( RUMF -ZD-00945 ), 1 male, 1 female ( HNHM diplo-04541 ) same locality and date GoogleMaps .

Diagnosis.

Xystodesmus keramae sp. nov. is a medium-sized Xystodesmus with typical colour pattern similar to X. parvus sp. nov. but differs from it by the well-developed coxal apophysis and the long, backwardly curved prefemoral process. It is also different from X. serrulatus where acropodite and prefemoral process are subequal in length, entirely straight, and very slender.

Description.

Length 26–32 mm, midbody width with paraterga 5.5–6.5 mm, midbody metatergal length 1.2–1.6 mm, collum width 4.4–4.8 mm, median collum length 1.9–2.4 mm. Body sides between segments 7–15 subparallel.

Head smooth, with 1 + 1 frontal setae, epicranial suture distinct. First antennal article sub-globose, 2 nd slightly clavate, otherwise subequal in length to straight articles 3–6, article 7 small, as long as wide, slightly tapering to its tip.

Pro- and metaterga completely smooth, transverse depression in metaterga clearly noticeable. Collum smooth, in dorsal view almost semicircular, posterior edge straight, slightly wavy, no marginal ridges, lateral corners triangular, directed posterior. Anterio-lateral edges of all paranota rounded, posterio-lateral corners of segment 2–4 in obtuse angle, posterior margins laterally bent forward. Small triangular projection starts from metaterga 5, only weakly increasing from segment 6 onwards, sublateral excavations lacking or only very shallow. Lateral sides of paranota slightly arched, outline of segments clearly delimited. Pore formula normal, pores in lateral central position on narrow paranota.

Segments 16–19 gradually tapering, caudal corners becoming strong and blunt. Epiproct in dorsal view triangular, in lateral view slightly curved downward, with four large setae on each lateral side on tubercles, projection with 2 + 2 setae apically; paraprocts slightly wrinkled, with two pairs of setae, upper ones on strong margin, lower ones on sides; hypoproct semicircular with two setae on tubercles.

Bases of midbody leg pairs clearly separated (by 1.2–1.6 mm in males, 1.5–1.7 mm in females), sterna smooth and wide, pro- and metasterna also clearly separated. Coxa short, as long as wide; prefemur ~ 1.8 × longer than coxa, on male postgonopodal legs and on all female legs with well-developed ventral spine; femur strongly incrassate, only ~ 1.5 × longer than prefemur; postfemur short, sub-globose, tibia and tarsus subequal in length, ~ 2 × as long as wide; claw normal on all legs.

Colour of living specimens (Fig. 16 B View Figure 16 ) pale brown, collum with dark margins, segments 2–4 with dark brown posterior margin, from 5 onwards medial part of metaterga with dark brown posterior margin; epiproct lighter. Head pale brown, antennae, legs, all paranota, and whole ventral side pale brown. Paranotal spots faded, hardly visible.

Male sexual characters. Second leg pair with strong, tubular coxal processes (as of X. kumamotoensis sp. nov., Fig. 3 D View Figure 3 ) provided with numerous apical setae, sterna, and coxae of segments 4–6 and further legs without any modifications. Gonopods (Fig. 2 A – C View Figure 2 ): Coxa stout, ~ 1.2 × longer than wide, with strong but slender coxal apophysis, and a single macroseta (ms) next to it. Prefemur short, thick, densely setose on ventral side; prefemoral process (pfp) strong, longer than and parallel to acropodite, but its pointed tip bent ventrad and almost touching tip of acropodite; acropodite (a) short, more slender than prefemoral process, gradually tapering towards the somewhat broader, leaf-like tip, and with a small triangular tooth (t) on half way of its mesal side (Fig. 2 B View Figure 2 ). Prostatic groove runs along the dorsomesal edge of acropodite.

Female characters (Fig. 2 D View Figure 2 ). 2 nd leg pair with pointed coxal projections (cp); cyphopods behind closely packed in small aperture, very close to each other. Receptacula (r) on posterio-mesal side small, triangular, hardly setose; operculum (op) elongated with 3 several small setae; bursal valves (v) large, setose, with high mesal apices.

Remarks.

The type locality, Aka-jima Island is a member of the Kerama Islands, ~ 25 km west from the southern part of Okinawa-jima Island. Another member of the Kerama Islands is Tokashiki-jima Island, where a number of female Xystodesmus specimens were also found (see unidentified female at the end of the paper), probably the same as X. keramae sp. nov.

Etymology.

Named after the type locality which belongs in the Kerama Islands (a subgroup of the Okinawa Group), west of Okinawa-jima Isl., Okinawa Pref., Japan. Genitive, from kerama.