Hylomus songoku, Nguyen & Nguyen & Nguyen & Phung, 2019

Nguyen, Anh D., Nguyen, Manh-Ha, Nguyen, Thu-Anh T. & Phung, Hong-Luong T., 2019, Review of Dragon Millipedes (Diplopoda, Polydesmida, Paradoxosomatidae) in the Fauna of Vietnam, with Descriptions of Three New Species, Zoological Studies 58 (14), pp. 1-31 : 13-18

Hylomus songoku sp. nov.

( Figs. 1 , 16−20 ) urn:lsid:zoobank.org:act:030505EE-DF75-4832-ABF1-CC70AB989A03

Material examined: Holotype: 1 male (IEBR- Myr 164H) Phu Tho Province, Xuan Son National Park, Lap cave , 11 December 2010, coll. Phung T. H. Luong . Paratypes: 1 male, 3 females (IEBR-Myr 164P) same data as holotype.

Etymology: The name refers to “ songoku ”, a main character of the Japanese manga “Dragon balls” by Toriyama Akira ( Japan).

Diagnosis: The species differs from its congeners in suberect gonopod; solenophore with rounded lobuliform lamina medialis, and well developed lamina lateralis with densely setose area; tip of solenophore tuberculiform.

Description: Body length ca. 17.9−25.2 mm (male), 23.9−26.8 mm (female); width of midbody pro- and metazonae 1.1−1.2 mm (male), 2.1−2.3 mm (female) and 1.3−1.4 mm (male), 2.4−2.5 mm (female), respectively. Holotype length 25.2 mm, width of midbody pro- and metazonae 1.2 mm and 1.4 mm, respectively.

Colouration ( Figs. 16−18 ): body generally light yellow. Pleura yellowish brown; head yellowish and somewhat darker on the region between antenna sockets.

Head ( Fig. 16A ) slightly broader than collum. Clypeolabral region densely setose. Epicranial suture distinct, linear. Antennae ( Fig. 16A ) slender, thin and extremely long, reaching segment 7 or 8 if stretched posteriorly; antennomere 3> 4> 5> 2> 6> 7> 1 in length; antennomere 7 black.

Collum ( Figs. 16 A−B) somewhat narrower than segment 2 in width; surface shining, densely microgranulated and wrinkled, with two rows of setiferous spines: one of 10−12 smaller spines close to anterior margin and, one of 4 + 4 larger spines near posterior margin; the posterior spines gradually smaller medially. Paraterga well developed, highly elevated, antler-shaped with three branches.

Width of body segment 4 <3 <2 = 5−16, thereafter gradually tapering towards telson. Prozonae shining and shagreened. Metazonae with dense microgranulation. Transverse sulcus starting on metatergum 5, but vague, incomplete, thin and line-shaped. Metaterga densely granulated with two rows of setiferous spines; the anterior spines variable, tiny whereas posterior spines longer and larger, 3 + 3 on metaterga 2−3, 4 + 4 on metaterga 4−5, 5(6) + 5(6) on subsequent metaterga ( Figs. 16 C−D, 17A, C); metatergum 19 with numerous small setiferous spines, but not arranged in row. Pleurosternal carinae absent. Axial line present, thin and line-shaped. Waist between pro- and metazonae broad, neither striolate nor beaded.

Paraterga ( Figs. 16 , 17 A−C) well developed, antler-shaped, with 5−6 branches (one main branch, 2−3 anterior ones and 1−2 posterior ones), highly elevated from metatergal surface, sometimes with several very tiny setiferous spines around base. Ozopore on segments 5, 7, 9−10, 12−13, and 15−19, lying under the base of the second anterior branch.

Epiproct ( Figs. 17D , 18 A−B) strongly modified with two large lateral setiferous tubercles. Tip normal with four spinnerets. Hypoproct ( Fig. 18B ) trapeziform with two well separated, distolateral setiferous knobs.

Sterna ( Fig. 17 D ) modestly setose; cross impression vague, without modifications except two separated, setiferous tubeliform processes between coxae 4 ( Fig. 18C ).

Legs slender and extremely long, about 3−3.5 times as long as midbody height. Prefemora not swollen. Femora without modifications except femora 6 & 7 with a big ventral tubercle at 2/3 its length ( Fig. 18D ). Tarsal brushes absent.

Gonopod ( Figs. 19−20 ) simple. Coxite (co) about 1/3 as long as telopodite. Prefemorite (prf) about half as long as acropodite, densely setose, demarcated laterally from femorite by a transverse sulcus. Femorite (fe) longer than postfemoral region, slightly enlarged distally, and somewhat curved ventrad. Postfemoral region suberect, consisting of solenophore (sph) and solenomere (sl). The former simple with a rounded lobuform (rl) lamina medialis and well developed lamina lateralis with a densely setose region (ds). Solenomere flagelliform, partly sheathed by solenophore. Seminal groove running entirely mesally, directed distodorsad before entering the solenophore. Tip (tp) of solenophore tuberculiform.

Remarks: The species was found in the Lap cave, and it is the first troglobitic species of the genus Hylomus recorded in Vietnam.

Figures

Fig. 1. Distribution of Hylomus species in mainland Vietnam. 1: Hoang Lien National Park (Sa Pa, Lao Cai Province); 2: Nam Xay Commune (Van Ban District, Lao Cai Province); 3: Duc Xuan Commune (Bac Quang District, Ha Giang Province); 4: Xuan Son National Park (Phu Tho Province); 5: Tam Dao (Vinh Phuc Province); 6: Cuc Phuong National Park (Ninh Binh Province); 7: Phong Nha – Ke Bang National Park (Quang Binh Province); 8: Lien Chieu District (Da Nang Province); 9: Ba Na National Park (Da Nang Province); 10: Lo Xo Pass (Kon Tum Province); 11: Ngoc Linh Mt. (Kon Tum Province); 12: Kon Chu Rang Natural Reserve (Gia Lai Province); 13: Buon Ho District (Dak Lak Province); 14: Hon Ba Mt. (Khanh Hoa Province); 15: Phan Rang (Ninh Thuan Province); 16: Cat Tien National Park (Dong Nai Province).

Fig. 16. Hylomus songoku sp. nov. from Xuan Son National Park. Holotype. Anterior part, laterodorsal view (A), ventral view (B). Middle part, lateral view (C), subdorsal view (D). Scale bar = 1 mm.

Fig. 17. Hylomus songoku sp. nov. from Xuan Son National Park. Holotype. Segment 10, dorsal view (A). Posterior part, lateral view (B), dorsal view (C), ventral view (D). Scale bar = 1 mm.

Fig. 18. Hylomus songoku sp. nov. from Xuan Son National Park. Holotype. Epiproct, dorsal view (A). Hypoproct and epiproct, ventral view (A). Sternal process between coxae 4, subventral view (C). Leg 6-7 (D). Scale bar = 1 mm.

Fig. 19. Hylomus songoku sp. nov. from Xuan Son National Park. Holotype. Right gonopod, lateral view (A), mesal view (B, C). Scale bars: A-B = 1 mm; C = 0.1 mm. (Note: solenophore in figure 16C was broken while taking SEM image)

Fig. 20. Hylomus songoku sp. nov. from Xuan Son National Park. Holotype. Right gonopod, lateral view (A), mesal view (B), dorsal view (C). Scale bar = 1 mm.

Fig. 2. Hylomus asper (Attems, 1937) from Ngoc Linh Mt. Right gonopod, lateral view (A), mesal view (B).

Fig. 3. Hylomus cattienensis (Nguyen, Golovatch & Anichkin, 2005) from Cat Tien National Park. Anterior part, lateral view (A), dorsal view (B), ventral view (C); body rings 10−12, dorsal view (D), lateral view (E); posterior part, lateral view (F), ventral view (G); gonopods, ventral view (H); sternite 5, ventral view (I). Anterior part, lateral view (A), dorsal view (B), ventral view (C); body rings 10−12, dorsal view (D), lateral view (E); posterior part, lateral view (F), ventral view (G); gonopods, ventral view (H); sternite 5, ventral view (I). No scale bars were inserted while taking photographs for this figure. This figure emphasises colouration, shapes of paraterga (Pa), metaterga (Me), head (He), collum (Co), gonopods (Go), sternal tubercles (st), epiproct (Epi) and hypoproct (Hy).

Fig. 4. Hylomus cattienensis (Nguyen, Golovatch & Anichkin, 2005) from Cat Tien National Park. Right gonopod, lateral view (A), mesal view (B). Scale bar = 0.5 mm.

Fig. 5. Hylomus cervarius (Attems, 1953) from Sa Pa. Left gonopod, dorsal view (A), lateral view (B).

Fig. 6. Hylomus enghoffi (Nguyen, Golovatch & Anichkin, 2005) from Phong Nha – Ke Bang National Park. Habitus photo. No scale bars were inserted while taking photographs for this figure. This figure emphasises natural colouration.

Fig. 7. Hylomus enghoffi (Nguyen, Golovatch & Anichkin, 2005) from Phong Nha – Ke Bang National Park. Anterior part, dorsal view (A), lateral view (B). Middle part, dorsal view (C). Posterior part, lateral view (D), ventral view (E). Hypoproct (F). No scale bars were inserted while taking photographs for this figure. This figure emphasises colouration, shapes of paraterga (Pa), metaterga (Me), collum (Co), epiproct (Epi) and hypoproct (Hy).