Zephronia siamensis Hirst, 1907

Srisonchai, Ruttapon, Sutcharit, Chirasak & Likhitrakarn, Natdanai, 2021, The giant pill-millipede genus Zephronia Gray, 1832 from Thailand, with a redescription of Z. siamensis Hirst, 1907 and descriptions of three new species (Diplopoda, Sphaerotheriida, Zephroniidae), ZooKeys 1067, pp. 19-56 : 19

Zephronia siamensis Hirst, 1907

Figures 1A-D ; 3 ; 4 ; 13A, B ; 14A

Zephronia siamensis Hirst, 1907: 218; Attems 1914: 147; Attems 1936: 182; Jeekel 2001: 21; Enghoff 2005: 89; Golovatch et al. 2012: 276; Wongthamwanich et al. 2012a: 30; Wesener 2016: 35.

Zephronia cf. siamensis - Decker 2010: 25.

Material examined.

Thailand - Chonburi Province • 2 ♂♂ 17 ♀♀; Sichang District, Koh Sichang ; 13°9'3.8"N, 100°48'56"E; 7 m a.s.l.; 14 November 2020; R. Srisonchai, N. Likhitrakarn, P. Jirapatrasilp leg. ; • 2 ♀♀; same collection data; NHMD • 2 ♀♀; same collection data; ZMUM • 3 ♀♀; same Province, Mueang District, Grand Cayon Chonburi; 12°31'23"N, 100°57'18"E; 7 m a.s.l.; 2 August 2019 ; ASRU members leg.; • 1 ♀; same Province, Sattahip District, Koh Chuang ; 12°31'23"N, 100°57'18"E; 7 m a.s.l.; 8 August 2013; R. Srisonchai, P. Jirapatrasilp leg. ; • 2 ♀♀; same Province , Bo Thong District, Wat Tham Khao Cha-ang-on; 13°12'31.7"N, 101°39'5.7"E; 128 m a.s.l.; 4 July 2016; R. Srisonchai, P. Tongkerd leg. ; • 1 ♀; Rayong Province, Mueang District, Koh Samet ; 12°34'22.6"N, 101°27'52.6"E; 128 m a.s.l.; 12 January 2010 ; ASRU members leg.

Type locality.

Kosichang and Chantaboon, Siam ( Hirst 1907), [Koh Sichang (Island) is in Chonburi Province, Chantaboon is in Chantaburi Province].

Diagnosis.

A member of Zephronia s. s. in which the position of Tömösváry’s organ located next to the aberrant ommatidia, not inside the antennal groove. Adult body length relatively small, usually ca. 20 mm, <26.5 mm, tip of subanal plate concave, process of telopoditomere 2 of anterior telopod rather short and strongly curved distally, and process of telopoditomere 2 of anterior telopod shorter than the combination of telopoditomeres 3 and 4. Similar in these respects to Z. laotica Wesener, 2019 and Z. dawydoffi Attems, 1953. Differs from these two species by showing a body length> 16.7 mm, live specimens with unique dark green, tergites with two yellow-brown patches located in anterior half of tergites, surface of tergites with conspicuous setae, femur of leg extended with conspicuous teeth, and telopoditomere 4 of anterior telopods posteriorly with a row of conspicuous crenulated teeth (cr-T).

Redescription.

Body size: Male: body length 15.0-26.5 mm. Width of thoracic shield 9.0-12.5 mm, of tergite 8 9.5-11.4 mm. Height of thoracic shield 5.2-6.4 mm, of tergite 7, 6.1-7.4 mm. Female: body length 15-23.0 mm. Width of thoracic shield ca. 12.1 mm, of tergite 8 ca. 12.8 mm. Height of thoracic shield ca. 7.3 mm, of tergite 7 ca. 8.2 mm.

Color (Fig. 1A-D ): Live specimens dark green; antennae dark brown; head, collum, thoracic shield, paratergites brown; legs bluish green. Tergites with two big patches, brown or yellowish brown, arranged in almost central part of anterior half; lateral part of tergites greenish dark, middle part of tergites brown. Anal shield with two colors contrasting each other, posterior half reddish brown, anterior half greenish dark brown. Color in alcohol after three months of preservation changed to greenish brown, head and collum dark greenish, tergites with a dark posterior margin, legs pale yellowish, distal podomeres rusty brown, antennae dark green.

Head: Trapezoid, anterior part of head clothed with numerous long setae, posterior part sparsely punctate; anterior margin of labrum with a single tooth. Each eye with 75-92 ommatidia. Aberrant ocellus located inside antennal groove.

Antennae (Fig. 3A ): Short, with rounded joints, extending posteriorly to leg-pair 2. Lengths of antennomeres: 6> 3> 5 = 4> 2 = 1. Antennomere 6 densely pubescent, sensilla basiconica surrounding apical disc. Last antennomere thickened, widened apically and axe-shaped. Shape of antennae sexually dimorphic, cylindrical in female; thickened, widened apically and slightly flattened in male. Apical disc with 51-61 (males) or 49-54 apical cones (females). No sclerotized crest/ridge between antennal socket and ommatidia.

Tömösváry’s organ: Located separately at a small, projected brim between ommatidia and antennal socket.

Gnathochilarium: Ventral surface with setae, other structures typical of the order. Palpi with sensory cones arranged in clusters. Mandibles not dissected.

Stigmatic plates (Fig. 3C ): First stigmatic plate subtriangular, apex broadly rounded, slightly curved towards coxa 1.

Laterotergites : 1 and 2 with a broad and well-rounded projection.

Collum: With glabrous surface, sparsely setose with very long setae, except for anterior and posterior margins which are densely setose.

Thoracic shield: Surface with tiny setae as on tergites. Shallow grooves filled with numerous long setae, no keels.

Tergites (Fig. 1A-C ): Surface shining, entirely clothed with dense and tiny setae, each seta located in a tiny pit. Tip of paratergites weakly projecting posteriorly.

Endotergum (Figs 13A, B , 14A ): Posterior margin with lobes, ‘rectangle-wavy’ margin. Inner section (inner area) smooth, with a few setae. Middle section (middle area) with a single row of conspicuous, elliptical cuticular impressions; distance between impressions as wide as individual diameter. Bristles arranged in one row, tip of the longest bristles not extended beyond posterior margin or not reaching to posterior margin.

Anal shield: Sexually dimorphic, in female large and well-rounded, in male slightly more rectangular, in both sexes glabrous. Surface similar to that of tergites. Inner surface (underside) with a single, long, black locking carina half as long as width of last laterotergite.

Legs (Fig. 3B ): Leg-pair 1 with one ventral spine, leg-pair 2 with two or three, leg-pair 3 with 4-6 ventral spines. Leg-pairs 4-18 with eight or nine ventral spines and two or three apical ones; thereafter slightly reduced into 5-8 ventral spines. In leg 9, femur ca. 1.7 ×, tarsus ca. 3.2 × longer than wide. Length of tarsus> femur> prefemur> coxa> tibia ≥ postfemur. All podomeres densely setose. Coxa large, with dentate ridge marginally (coxal process). Coxal process absent in leg-pairs 1 and 2. Prefemur without teeth. Femur large and stout, extended mesally, with 7-11 conspicuous teeth.

Subanal plate (Fig. 3F ): Large and wide, semicircular, divided by a conspicuous mesal constriction; central margin (tip) concave, wide; lateral margin slightly convex. Densely setose.

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

Anterior telopods (Fig. 4A-C ): First telopoditomere rectangular, slightly longer than wide. Telopoditomere 2 large, as long as telopoditomeres 3 and 4 combined. Process of telopoditomere 2 located posteriorly, but partly visible laterally in anterior view. Process of telopoditomere 2 wide, broader than telopoditomeres 3 and 4. Process of telopoditomere 2 conspicuously unciform, protruding as high as basal part of telopoditomere 4, apically with a well-rounded tip. Margin towards telopoditomere 3 with a membranous area carrying a rather small and sclerotized process (sp), apically with a rounded tip. Telopoditomere 3 slender, 1.4X longer than wide, 1.5X longer than telopoditomere 4. Telopoditomere 4 posteriorly with a row of 7 small and crenulated teeth (cr-T) with two prominent spines. All podomeres covered with long sparse setae, except for central part of telopoditomere 1 and posterior surfaces of 2-4.

Posterior telopods (Fig. 4D-F ): Inner horns with sharply edged tips, slightly curved caudad. Telopodite consisting of four podomeres. First podomere stout and narrow, nearly twice as wide as long. Immovable finger (process of telopoditomere 2) shorter than movable finger (consisting of telopoditomeres 3 and 4). Immovable finger stout and narrow, 1.6X longer than wide, not curved, glabrous distally. Margin towards movable finger with two massive, triangular, membranous lobes (ML). Telopoditomere 3 elongated, slightly curved, twice as long as telopoditomere 4; with a large, swollen, membranous ledge; postero-apically slightly enlarged, with a row of 11 or 12 crenulated teeth (cr-T). Telopoditomere 4 slender, twice as long as wide, slightly tapering apically; with a large, swollen, membranous ledge; with two long and sclerotized spines. Telopoditomeres 1 and 2 on both sides covered with few setae. Telopoditomere 3 at base of inner margin with a few setae, remaining parts of telopoditomeres 3 and 4 almost glabrous.

Female sexual characters (Fig. 3E ): Vulva large, covering ca. 2/3 coxa, located at mesal side, extending mesally to basal third of prefemur. Operculum regularly rounded, margin straight, mesal margin not protruding.

Distribution and habitats

(Figs 15A , 16 ). The newly collected specimens from the type locality were found under groups of Pandanus trees in a limestone area near a beach, while the other material from the Chonburi and Rayong provinces were likewise taken from limestone habitats. Currently, this species is known to occur only in eastern Thailand.

Remarks.

The live coloration of adults is generally dark green with two yellowish brown patches in the anterior half of tergites, this being quite unique for this species.

Almost 114 years since the original description, a redescription of Z. siamensis Hirst, 1907 has been made in this study based on the newly collected specimens from Koh Srichang (Srichang Island), here regarded as strict topotypes.

Considerable variation has been found in body size of the specimen described by Hirst (1907) compared to the topotypes: the type specimen was ca. 26.5 mm in length, whereas the new material we examined were within the size range of 16.7-23.5 mm.

Figures

Figure 1. Photographs of living Zephronia spp. A-D Zephronia siamensis E, F Zephronia phrain. Photographs not to scale.

Figure 3. Zephronia siamensis A-C male D, E female (CUMZ-Zeph 0013) A right antenna, ventral view B the ninth left leg, posterior view C first coxae with stigmatic plates, posterior view D coxae of second legs with gonopores, posterior view E coxae and prefemur of second legs with vulvae, posterior view F subanal plate, ventral view. Abbreviations: cx = coxa, o = operculum, pre = prefemur, syn-cx = syncoxite, St-Pl = stigmatic plate.

Figure 4. Zephronia siamensis A-C left anterior telopod, anterior, posterior and sublateral views, respectively D, E Left and right posterior telopods, posterior view F Posterior telopod, anterior view. Abbreviations: cr-T = crenulated teeth, cx = coxa, ML = membranous lobe, sp = sclerotized process, syn-cx = syncoxite.

Figure 13. SEM of endoterga of body ring 7, all from ventral views A, B Zephronia siamensis Hirst, 1907 C, D Zephronia enghoffi sp. nov. E, F Zephronia golovatchi sp. nov. G, H Zephronia panhai sp. nov. Abbreviations: cp = cuticular impression, ms = middle section, is = inner section, os = outer section, pm = posterior margin.

Figure 14. SEM of endoterga in body ring 7, all from ventral views A Zephronia siamensis Hirst, 1907 B Zephronia enghoffi sp. nov. C Zephronia golovatchi sp. nov. D Zephronia panhai sp. nov. E inner area of endotergum in Zephronia panhai sp. nov.

Figure 15. Limestone habitats of some Zephronia spp. A type locality of Zephronia siamensis (Koh Srichang, Chonburi Province) B, C type locality of Zephronia enghoffi sp. nov. (Tham Phaya Nakharat, Khon Kaen Province) D Habitat of Zephronia phrain at Phawor shrine, Tak Province.

Figure 16. Known distribution of Zephronia spp. in Thailand. Red triangle = Zephronia lannaensis; green circle = Zephronia phrain; blue triangle = Zephronia enghoffi sp. nov.; sky blue square = Zephronia golovatchi sp. nov.; purple circle = Zephronia panhai sp. nov.; yellow diamond = Zephronia siamensis Hirst, 1907; orange square = Zephronia viridisoma.