Hyleoglomeris alba Nguyen, Kuroda & Eguchi, 2022

Kuroda, Mai, Eguchi, Katsuyuki, Oguri, Emiko & Nguyen, Anh D., 2022, Two new cave Hyleoglomeris species (Glomerida, Glomeridae) from northern Vietnam, ZooKeys 1108, pp. 161-174 : 161

Hyleoglomeris alba Nguyen, Kuroda & Eguchi sp. nov.

Figs 6 , 7 , 8 , 9 , 10 , 11

Material examined.

Holotype. Vietnam: male; Cao Bang Province, Tra Linh District, Quoc Toan commune, Thang Hen lake , Ky Rang cave , 22.7650N, 106.2911E, 2 Nov. 2021, leg. AD Nguyen (IEBR-Myr 919) . Paratypes. Vietnam: 2 females, Cao Bang Province, Tra Linh District, Quoc Toan commune, Thang Hen lake , Ky Rang cave , 22.7650N, 106.2911E, 12 Oct. 2020, leg. AD Nguyen, VT Mai & VD Dang (IEBR-Myr 917) ; 1 male, Cao Bang Province, Tra Linh District, Quoc Toan commune, Thang Hen lake , Ky Rang cave , 22.7650N, 106.2911E, 17 March 2022, leg. AD Nguyen & DD Nguyen (IEBR-Myr 928) .

Diagnosis.

The species can be recognized by a completely troglobiotic form with no eyes, an unpigmented body, and a roundly triangular syncoxital lobe.

According to Golovatch et al. (2006, 2013), the new species seems to belong to the troglobiont species group containing H. speophila , H. spelaea , H. cavernicola , H. differens Golovatch, Geoffroy & Mauriès, 2006, H. reducta Golovatch, Geoffroy & Mauriès, 2006, and H. albicorporis Zhang & Zhang, 1995. These species are characterized by a totally unpigmented body. However, the new species differs from these species in lacking ocelli and the telopods bearing a roundly triangular syncoxital lobe. In contrast, the other species have convex ocelli, telopods with a roundly subtraperziform syncoxital lobe ( H. speophila , H. cavernicola , H. reducta , H. albicorporis ), or a subquadrate syncoxital lobe ( H. spelaea ), or a roundly triangular syncoxital lobe ( H. differens ).

Etymology.

From the Latin Hyleoglomeris alba , meaning white. It was used to emphasize the unpigmented body of the new species.

Description.

Body length 4.38 mm, width of the second segment ~ 2.02 mm. Color entirely white, unpigmented (Figs 6 - 8 ). Ocelli totally absent. TÖmÖsvary’s organ transverse, strongly horseshoe-shaped, ~ 2 × as wide as long (Fig. 8B ). Antennae long and slender, antennomere, ~ 3 × longer than wide, antennal tip with four apical sensory cones (Fig. 8A ).

Collum semicircular, with a trace of a transverse oval spot in the center and two distinctly transverse striae (Fig. 7D ). Second tergum with a narrow hyposchism, not reaching the caudal margin, with seven or eight striae, five or six of which cross the dorsum. Anal shield rounded, very slightly concave medio-caudally (Fig. 8D ).

Leg-pair 17 (Figs 9A , 11A ) strongly reduced, with four podomeres, with a high, regularly rounded, outer coxal lobe; coxa with an apical setiferous spine; leg-pair 18 (Figs 9B , 11B ) also strongly reduced, but more developed in comparison with leg-pair 17, with four podomeres, and a simple V-shaped syncoxital notch.

Telopods (Figs 9C, D , 10 , 11C-E ) with a roundly triangular, sparsely setose, central syncoxital lobe (syl) accompanying two setiferous syncoxital horns (syh), each directed ventrad, slightly longer than the syncoxital lobe, tip crowned with an apical setoid. Prefemur (pre) and femur (fe) with long trichosteles (pret and fet), prefemoral one (pret) longer than femoral one (fet). Prefemur without additional processes. Distomesal process of femur (dpf) large, long, straight, rectangular; distal part tuberculiform and strongly curved downwards, directed laterodorsad. Tibia (ti) with a shorter triangular distolateral process (dpt). Tarsus (ta) slightly sigmoid anteriomesad, subacuminate apically, with a seta distoventrally.

DNA barcode.

We failed to amplify the COI fragments of this species.

Remarks.

The species was collected from the totally dark region in the cave. The completely unpigmented body without ocelli, and with long, slender antennae suggest that this species is a true troglobiont. These characters were also mentioned in Liu et al. (2017) who reviewed the morphological adaptations seen in troglobitic glomerids and other millipedes.

Figures

Figure 6. A, B Hyleoglomeris alba Nguyen, Kuroda & Eguchi, sp. nov., habitus C Ky Rang cave, dark zone. Images not to scale.

Figure 7. Hyleoglomeris alba Nguyen, Kuroda & Eguchi, sp. nov., holotype A whole body, dorsal view B lateral view C ventral view D collum, anterior view.

Figure 8. Hyleoglomeris alba Nguyen, Kuroda & Eguchi, sp. nov., holotype A left antenna B right antenna and Toemoesvary's organ C left hyposchism, dorsal view D pygidium, posterior view.

Figure 9. Hyleoglomeris alba Nguyen, Kuroda & Eguchi, sp. nov., holotype A leg-pair 17 B leg 18 C left telopod, anterior view D subposterior view.

Figure 10. Hyleoglomeris alba Nguyen, Kuroda & Eguchi, sp. nov., holotype A right telopod and syncoxital lobe, posterior view B anterior view.

Figure 11. Hyleoglomeris alba Nguyen, Kuroda & Eguchi, sp. nov., holotype A leg-pair 17 B leg-pair 18 C syncoxital lobe and syncoxital horns D left telopod, anterior view E subposterior view. Scale bar: 0.1 mm. Abbreviations: syl = syncoxital lobe, syh = syncoxital horn, pref = prefemur, fe = femur, pret = prefemoral trichostele, fet = femoral trichostele, dpf = distomesal process of femur, ti = tibia, dpt = distolateral process of tibia, ta = tarsus.