Sphaerobelum truncatum Wongthamwanich, n. sp.

Abstract

Sphaerobelum truncatum Wongthamwanich, n. sp. Figs. 5 –11 Material examined. Holotype male, CUMZ 2010.11, Thailand, Nan Province, Song Khwae District, Na Rai Luang Sub-district, Pang Hi Village; secondary forest; Latitude: 19.3962, Longitude: 100.6951; coll. N. Wongthamwanich; hand collecting; 22 August 2010. Paratypes: 4 males, CUMZ 2010.12 –15, 4 females, CUMZ 2010.16 – 19, 1 male, FMNH-INS 0 0 0 0 0 72 674, 1 female, FMNH-INS 0 0 0 0 0 72 673, 1 male, ZFMK Myr 0 0 1, 1 female, ZFMK Myr 0 0 2, same data as holotype. Etymology. The specific epithet is a Latin adjective, meaning terminating abruptly, and refers to the truncated state of the lateral end of the third podomere on the anterior telopods (Fig. 11 C). Diagnosis. Sphaerobelum truncatum differs from all other Sphaerobelum species in the unique combination of the following characters of the anterior telopods (Figs. 11 A–C): four podomeres above syncoxite, second podomere posteriorly with a process (Figs. 11 B, C) and one spine on the anterior side of the inner margin (Fig. 11 C), third and fourth podomeres located posteriorly juxtaposed to process of second podomere, third podomere distally truncate, fourth podomere with three sclerotized spines all located on small thin separated sclerotized plates: one spine at apex, the other two on posterior side (Figs. 11 B, C). Anterior telopods without sclerotized teeth. S. truncatum differs from the closely related species S. separatum Attems, 1953 in the presence of a well-rounded fourth podomere on the posterior telopod (Figs. 11 D, E), while the tip of the posterior telopod in the latter species is prolonged into a thin process and curved towards the process of the second podomere. S. truncatum is the only giant pill-millipede species known to have a regularly ‘square-wavy’ margin on the endotergum (Fig. 9 B). COI Sequence (paratype, FMNH-INS 0 0 0 0 0 72 674): Accession # JN 885184. See supplementary material. Description. Measurements: Males: length 18.6 –24.0 mm, width at the seventh tergite 10.2–12.6 mm, width of thoracic shield 9.9–12.2 mm, height of thoracic shield 5.7–6.8 mm. Sizes of volvated male (for epimorphic stadia, Figs. 4 A, B): length (tergite 5 –tergite 11 or 12) 12.1–13.9 mm, width (tergite 7) 10.2–12.6 mm, and height (thoracic shield–tergite 8) 10.7–12.6 mm. Females: length 21.2–30.4 mm, width at the seventh tergite 11.5–15.2 mm, width of thoracic shield 11.0– 14.3 mm, height of thoracic shield 6.2–8.1 mm. Sizes of volvated female: length 13.0– 17.6 mm, width 11.5–15.2 mm, and height 11.5–15.4 mm. Habitus (Fig. 5 C): Overall shape elliptical, tapering slightly from sixth tergite towards head. Coloration (Figs. 5 A–C): head dark brown, collum, thoracic shield, tergite, and anal shield black. Antennae and legs light yellow. Head: trapezoid, anterior part of the head with many long setae, posterior part densely dimpled; anterior margin of labrum with a single tooth. Eye field round, width approximately one mm, consisting of more than 60 densely-packed ocelli. No sclerotized crest/ridge between antenna socket and eye field. Tömösváry organ (Fig. 5 D) between eye field and antenna socket, next to, but separated from eye field. Antennae (Figs. 6 A–C): with six visible antennomeres; basal antennomere with a few thinly scattered sclerotized nodules (Fig. 6 C); distal antennomere enlarged, round and club-shaped, with 81–84 sensory cones in males, 36–42 in females. Antennomere lengths: 6> 1> 2 = 3> 4 = 5. Mandibles (Figs. 7 A, B): with a single external tooth, a three-lobed internal tooth, six rows of pectinate lamellae, number of teeth on pectinate lamellae declining from apical to proximal lamella, molar plate with one visible ridge. Gnathochilarium (Fig. 7 C): with numerous long setae on the lingual lamella. Inner palpi with numerous elongate and sharp sensory cones (Figs. 7 D, E), reduced lateral palpi with a field of 6 sensory cones (Figs. 7 D, F). Collum: anterior and posterior margin with a few setae, center part sparsely setae, densely covered by dimplelike impressions. Thoracic shield: ridge on lateral lobe absent, accompanied by a few long setae; center part of anterior margin covered sparsely with long setae. Tergites 3–12 (Fig. 8): Anterior margins dominated by small conical spines (Fig. 8 C). Two submarginal rows of round sclerotized nodules: nodules of anterior-most row large and isolated, those of second row small and close together (Fig. 8 B). Anterior fifth of tergite with smooth zone, followed by a zone of 3–5 irregular rows of long setae, and then by an area of short setae (Fig. 8 B). Central four fifths of tergite dominated by short setae, nodules and slightly curved long setae inserted in large dimples (Figs. 8 A, D). Posterior margins with a few thick setae (Fig. 8 A). Endotergum (Fig. 9): with a regularly ‘square-wavy’ margin (Fig. 9 B), outer zone with three rows of irregular marginal setae not reaching posterior margin. A single row of small elliptical cuticular impression present next to marginal ridge. Intersegmental membrane smooth, without cones or setae (Fig. 9 A). Anal shield: densely covered with long setae; round in both sexes. Inner side with three or four striae. Ventral side with one long black locking carina (Fig. 5 C, Lc). Legs: first pair of legs without coxal lobe (Fig. 5 F), first tarsi with two ventral spines and without apical spine; second pair of legs with small coxal lobes in male (Fig. 5 H), second tarsi with four ventral spines and without apical spine; third leg pair with acute coxal lobes, third tarsi with five or six ventral spines and one apical spine; ninth pair of legs with seven ventral spines and one apical spine on tarsus, femur with one long ridge (Fig. 11 G). Femur of ninth pair of leg 2.0 times longer than wide, tarsus 4.8 times longer than wide (Fig. 11 G). Stigmatic plate of first leg (Fig. 5 F): rounded, short and weakly curved, but forming a steep angle towards the coxa. Female vulva (Figs. 5 G, 11 H): consisting of two basal plates which are fused proximally and divided distally. Operculum pointed, basal part of operculum surrounding apical part of basal plates, distally protruding above coxa to basal half of prefemur. Vulva covers half (1 / 2) of coxa width, vulva is one-third (1 / 3) longer than coxa. Subanal plate (Fig. 10 A): brown, semicircular with a central shallow notch, laterally with four rib-like structures. Male gonopore (Fig. 10 B): covered by undivided sclerotized plate. Anterior telopods (Figs. 11 A–C): syncoxite with small spines, telopodite consisting of four podomeres, all podomeres covered by long setae. First podomere width equals height. Second podomere with posterior lobe-like, curved process with rounded edges; process protruding up to end of third podomere; anterior side of process with a single spine at inner margin. Third podomere distally truncate. Fourth podomere as long as third podomere, with three sclerotized spines located on small thin sclerotized fields, one spine at apex and the other two located on posterior side. Sclerotized teeth absent. Posterior telopods (Figs. 11 D, E): inner horns with sharp-edged tips, slightly curved backwards. Telopodite consisting of four podomeres. First podomere parallelogram-shaped. Second and third podomere dominated by short setae, margins with long setae. Process of second podomere weakly curved, distally glabrous, posteriorly apically enlarged and swollen (Fig. 11 D), anteriorly apically concave, spatulate, with a single sclerotized spine (Fig. 11 E). Moveable finger consisting of third podomere and small fourth podomere, slightly curved. Third podomere at inner margin with one small light colored spine, without any crenulated teeth. Fourth podomere at inner margin with two small sclerotized spines located in single brown sclerotized field. Intraspecific variation. Only seven males and six females of S. truncatum were available for analysis. However, some characters presented a clear difference between the sexes, such as the body length of females that tended to be longer than that of the males, while males have more sensory cones on the distal antennae than females. Life history. Adult specimens were collected in late August 2010 during the rainy season. Numerous eggs were found in an adult female, with most of them aggregated into many small clusters located between the intestine and the body wall, from the second leg pairs to posterior end of the body. The eggs as preserved in 70 % ethanol were orange in color. Mature eggs were round in shape with a diameter of about 2–2.5 mm. Distribution and ecology. The new species is only known from the type locality at 440–450 m altitude. There is a small stream running along the secondary dry evergreen forest and the forest floor is covered by laterite soil with saplings and seedlings, including a leaf litter of up to 3 cm depth. At the time of collection, the weather was a light precipitation, 92 % relative humidity, 25.5–26 °C and 27 °C soil and air temperature respectively. Most specimens were found on a 60 degree slope and only a few specimens were found on a flat plain area. Animals were found rolled up above the forest ground close to tree bases, in shallow soil pockets and under leaf litter. FIGURE 11. Sphaerobelum truncatum n. sp., A-G holotype, H female paratype, drawing, A: right anterior telopod, anterior view; B: last three podomeres of right anterior telopod, posterior view; C: last three podomeres of right anterior telopod, lateral view; D: last three podomeres of right posterior telopod, posterior view; E: last three podomeres of right posterior telopod, anterior view; F: stigmatic plate of 9 th left leg; G: 9 th left leg, posterior view; H: second right coxa with vulva, posterior view. Arrows point to the second podomere process. Abbreviations: Cx = coxa; ST = stigmatic plate; O = operculum; EP = external plate of vulva; IP = mesal plate of vulva. Roman numbers refer to number of podomere. Scale bars = 1 mm. Behavior. Sphaerobelum truncatum seems to be more active than Zephronia sp. They unroll their body in less than 5 minutes after capturing in the hand, which has never been observed for Zephronia sp. Sphaerobelum truncatum is well camouflaged, having similar color patterns to various objects in the environment, such as dried leaves and fruit seeds. The animals can also hide during the day by digging into the soil.Published as part of Wongthamwanich, Nattarin, Panha, Somsak, Sierwald, Petra, Wesener, Thomas & Thirakhupt, Kumthorn, 2012, A new species of the giant pill-millipede genus Sphaerobelum Verhoeff, 1924 from northern Thailand, with an extensive description and molecular characters (Diplopoda: Sphaerotheriida: Zephroniidae), pp. 29-43 in Zootaxa 3220 on pages 34-42, DOI: 10.5281/zenodo.21275