Sphaerobelum turcosa Srisonchai & Pimvichai, 2023

Srisonchai, Ruttapon, Likhitrakarn, Natdanai, Sutcharit, Chirasak, Backeljau, Thierry & Pimvichai, Piyatida, 2023, A new jewel-like species of the pill-millipede genus Sphaerobelum Verhoeff, 1924 (Diplopoda, Sphaerotheriida, Zephroniidae) from Thailand, ZooKeys 1181, pp. 41-57 : 41

Sphaerobelum turcosa Srisonchai & Pimvichai sp. nov.

Figs 2 , 3 , 4 , 5

Materials examined.

Holotype ♂ (CUMZ-Zeph0011), Thailand, Loei Province, Mueang Loei District, Phu Pha Lom Forest Park, 383 m a.s.l., 17°33'16"N, 101°52'06"E, 10/07/2014, leg. R. Srisonchai and C. Sutcharit.

Paratypes. 5 ♂, 2 ♀ (CUMZ-Zeph0012), same data as holotype . 1 ♂, 2 ♀ (CUMZ-Zeph0012), same data as holotype, 01/08/2020 and 25/09/2021, leg. P. Pimvichai, P. Prasankok and S. Saratan. 1 ♂, 2 ♀ (CUMZ-Zeph0012), same District, Wat Phu Pha Lom, 265 m a.s.l., 17°33'16"N, 101°52'04"E, 14/05/2008, leg. C. Sutcharit.

Etymology.

The specific name is a Latin adjective, meaning 'turquoise, greenish-blue mineral,' and refers to the general body color of living specimens.

Diagnosis.

Coxal process on leg 2 sharply projecting, tarsi of legs 4-21 with 4/5/6/7/8 ventral spines. Similar in these respects to S. lachneeis , S. schwendingeri and S. laoticum , but S. turcosa sp. nov. differs from them by the combination of several characters, viz. body yellow contrasting to dominant greenish-blue color (vs. dark green/black); mesal margin of femur with teeth (vs. without teeth); vulva board and large, covering mesal 2/3 of coxa (vs. narrower, covering mesal 1/3 or half of coxa); anterior telopod consisting of 4 conspicuous telopoditomeres (vs. 3 telopoditomeres); immovable fingers of posterior telopod slender (vs. strongly humped and swollen).

Description of the new species.

Measurements: Male Holotype. Body length ca 18.5 mm. Width, of thoracic shield = 9.5 mm, of tergite 8 = 10.3 mm (= broadest). Height, of thoracic shield = 5.1 mm, of tergite 7 = 5.3 mm (= highest). Male: body length = 15.2-18.4 mm. Width, of thoracic shield = 7.9-9.0 mm, of tergite 8 = 8.7-9.4 mm. Height, of thoracic shield = 4.8-5.6 mm, of tergite 7, 5.2-6.2 mm. Female: body length = 20.6-24.5 mm. Width, of thoracic shield = 6.3-10.6 mm, of tergite 8 = 7.2-11.6 mm. Height, of thoracic shield = 5.4-6.0 mm, of tergite 7, 5.7-6.7 mm.

Coloration: Live animals yellow with contrasting greenish-blue anterior margins of tergites and darker blue dorsal axial stripe (Fig. 2A-D ), thoracic shield with a large, paramedian, greenish-blue band at middle (Fig. 2A-C ), anal shield with a large, greenish-blue diamond at axial line (Fig. 2B, C ), head, collum and groove of thoracic blackish to dark blue (Fig. 2A ), legs, antennae, paratergite depressions and venter light brown to brown, venter brown to yellow brownish; coloration in alcohol, after more than 10 years of preservation, faded to light yellow with contrasting greenish-blue anterior margins of tergites, head, collum and groove of thoracic dark blue to blue, legs, antennae, paratergite depressions and venter brown to yellowish.

Head: trapezoid, anterior part of the head with many long setae, posterior part densely dimpled; anterior margin of labrum with a single tooth. Eyes with 37-63 ocelli (male) or 55-67 (female). Aberrant ocellus located inside antennal groove.

Antennae: short, with rounded joints, extending posteriorly to leg-pair 3. Lengths of antennomeres: 2<3=4<1<5<6. All antennomeres densely pubescent, sensilla basiconica surrounding apical disc. Last antennomere thickened, apically widened and well rounded (Fig. 2A ). Apical disc with 22-42 apical cones (male) or 21-29 (female). No sclerotized crest/ridge between antenna socket and eye field. Tömösváry organ located between eye field and antenna socket, next to, but separated from eye field.

Gnathochilarium: Structure typical of the Sphaerotheriida . Palpi with sensory cones arranged in clusters.

Mandibles: not dissected.

Collum: with glabrous surface, except for anterior and posterior margin with a few isolated and long setae.

Stigmatic plates: first stigmatic plate rounded, apex well-rounded, slightly curved towards coxa (Fig. 3A ).

Laterotergites: laterotergite 1 strongly projecting into a sharp tip. Laterotergite 2 with a broad, stout projection and a deep notch at lateral margin, like following laterotergites.

Following tergites: surface glabrous, shining, except the groove of paratergite with tiny setae. Tips of paratergites of midbody tergites projecting posteriorly.

Thoracic shield: surface glabrous as in tergites. Shallow grooves with few setae, surface glabrous, no keels.

Endotergum: Posterior margin (pm) flat, regular (Fig. 5A ). Outer area (oa) without setae. Middle area (ma) with a single row, conspicuous, elliptical cuticular impressions (cp); distance between impressions as long as individual diameter (Fig. 5B ). Bristles arranged in two rows, tip of the longest bristles not extended beyond posterior margin or not reaching to posterior margin (Fig. 5A ). Inner area (ia) without tubercles or setae, but with small pits (Fig. 5D ).

Anal shield: slightly sexually dimorphic, in female large and well-rounded (Fig. 2B ), in male slightly more rectangular, in both sexes glabrous. Surface similar to that of tergites. Underside with a single, very short, black locking carina, six times shorter than width of last laterotergite.

Legs: leg-pair 1 with 1 or 2 ventral spines, leg-pair 2 with 3 or 4, leg-pair 3 with 5 or 6. First two leg-pairs without an apical spine. Leg pairs 4-21 with 6 or 7 ventral spines and one apical spine. In leg 9, femur 1.6 times, tarsus 3.5 times longer than wide (Fig. 3C ). Femur extended mesally into a dentate margin featuring 10-14 teeth. All podomeres densely setose. Coxa with a large and marginally toothed process. Coxal process absent at first leg and sharply projecting at second (Fig. 3B ). Prefemur at apical margin with a projection laterally and mesally. Lateral projection triangular and sharply edged, juxtaposed to coxal process (Fig. 3C ).

Female sexual characters: vulva large, covering 2/3 of coxa, located at mesal margin, extending mesally to anterior third of prefemur (Fig. 3E ). Operculum rounded, mesal margin projecting into a well-rounded lobe 1/2 as high as remaining operculum. Subanal plate: large and wide, divided by a suture into two halves. Densely setose (Fig. 3D ).

Male sexual characters: gonopore large, covered with a single, undivided, triangular, sclerotized plate (Fig. 3B ).

Anterior telopods (Fig. 4A-C ): First podomere rectangular, slightly wider than long. Telopoditomere 2 large, as long as telopoditomere 3. Immovable finger (process of telopoditomere 2) wide, located posteriorly, but partly visible laterally in anterior view, projecting to half of movable finger (telopoditomeres 3 and 4), slightly curved, apically with a rounded tip. Telopoditomeres 3 and 4 divided by a short and weak suture, this suture being almost visible in lateral view (Fig. 4A-C ). Telopoditomere 3 large, cylindrical, slender, 1.2 times longer than wide, 2 times longer than telopoditomere 4 (Fig. 4A, C ). Telopoditomere 4 short, well-rounded, posterior face with two small, sclerotized spot and triangular spines (Fig. 4B ). All podomeres covered with long setae.

Posterior telopods (Fig. 4D-F ): inner horns with sharp-edged tips, slightly curved caudad. Telopodite consisting of four podomeres. First telopoditomere rectangular, slightly longer than wide. Immovable finger (process of telopoditomere 2) as long as movable finger, consisting of telopoditomeres 3 and 4. Immovable finger wide, 2.5 times longer than wide, with a characteristic, distally swollen, clearly rounded apically, apex only slightly wider than base; tip strongly curved when seen in dorsolateral view. Immovable finger in anterior view with a small spine, at middle with sclerotized spot. Telopoditomere 3 long and slender, 2.5 times longer than wide, with a membranous lobe at a excavate inner margin. Telopoditomere 4 very short and slender, only 4.5 times shorter than telopoditomere 3, 1.5 times longer than wide, slightly tapering apically. Telopoditomere 4 with one small, weak spine at margin towards immovable finger. Telopoditomere 1 and 2 at both sides covered by setae. Telopoditomere 3 only basally in anterior view with setae, remaining part, as well as telopoditomere 4 glabrous.

Distribution and habitat.

Currently known only from the type locality. All specimens were crawling openly on the bottom of several holes in humid rocks (Fig. 6 ). The stark bright color invited collectors to pick them up.

Figures

Figure 2. Habitus, live coloration. Sphaerobelum turcosa sp. nov., ♀ paratype A, E sublateral views B-D enrolled, sublateral, lateral, dorsal views, respectively. Scale bars: 5 mm.

Figure 3. Sphaerobelum turcosa sp. nov. A-C ♂ holotype D, E ♀ paratype A first left coxa with stigmatic plate B coxa of second leg with gonopore C ninth right leg D coxa and prefemur of second leg with vulva E subanal plate. Scale bars: 0.5 mm.

Figure 4. Sphaerobelum turcosa sp. nov. A-C ♂ holotype D-F ♂ paratype A-C left anterior telopods, anterior, posterior and lateral views, respectively D, E left posterior telopod, posterior, subventral views F posterior telopods, anterior view. Scale bars: 0.5 mm.

Figure 5. Sphaerobelum turcosa sp. nov. ♂ paratype, SEM micrographs of the endoterga on the midbody segment. A all areas of endotergum, posterior margin (pm), outer area (oa), middle area (ma), cuticular impressions (cp) and inner area (ia) B middle area and cuticular impressions C bristles D inner area.

Figure 6. Distribution and type locality of Sphaerobelum turcosa sp. nov. A distribution map of Sphaerobelum species in Thailand B, C limestone habitat at the type locality.