Section 3 of 4
Results
Natdanai Likhitrakarn, Sergei I. Golovatch, Ruttapon Srisonchai, Sothearen Thi, Sophea Chhin, Vanny Lou, Pablo Sinovas, Parin Jirapatrasilp, Chirasak Sutcharit, Somsak Panha, and Teerapong Seesamut · about 29 minutes
The cave-dwelling millipedes of the genus Plusioglyphiulus in Cambodia currently comprise six species, including two new species described herein. The phylogenetic placement and species-group assignment of the two new species follow the COI-based framework of Seesamut et al. (2026), rather than representing an independent de novo phylogenetic reconstruction in the present study. Under this framework, both new species are assigned to Group D, which includes 26 species-level lineages.
Within Group D, the two new Cambodian species are positioned among closely related congeners but are genetically differentiated from their nearest lineages. Uncorrected pairwise COI p-distances within Group D ranged from 0.9% to 20.5% (Table 1). The two new Cambodian species were separated from their closest congeners by minimum interspecific distances of 9.6% and 9.9%, respectively. Although these values represent the lower range of interspecific divergence observed within the group, they are accompanied by clear diagnostic differences in morphology. The COI data are therefore congruent with the morphological evidence and provide supplementary support for the delimitation of the two new species.
Taxa | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25
Plusioglyphiulus sp. D10 | | | | | | | | | | | | | | | | | | | | | | | | |
Plusioglyphiulus parviserratus sp. nov. | 0.139 | | | | | | | | | | | | | | | | | | | | | | | |
Plusioglyphiulus battambangensis sp. nov. | 0.145 | 0.103 | | | | | | | | | | | | | | | | | | | | | | |
Plusioglyphiulus sp. D3 | 0.160 | 0.146 | 0.143 | | | | | | | | | | | | | | | | | | | | | |
Plusioglyphiulus sp. D12 | 0.152 | 0.132 | 0.138 | 0.155 | | | | | | | | | | | | | | | | | | | | |
Plusioglyphiulus likhitrakarni | 0.138 | 0.099 | 0.096 | 0.155 | 0.151 | | | | | | | | | | | | | | | | | | | |
Plusioglyphiulus tham | 0.178 | 0.179 | 0.181 | 0.170 | 0.188 | 0.184 | | | | | | | | | | | | | | | | | | |
Plusioglyphiulus pimvichaiae | 0.155 | 0.121 | 0.152 | 0.146 | 0.149 | 0.146 | 0.194 | | | | | | | | | | | | | | | | | |
Plusioglyphiulus sp. D4 | 0.160 | 0.139 | 0.149 | 0.121 | 0.136 | 0.157 | 0.179 | 0.129 | | | | | | | | | | | | | | | | |
Plusioglyphiulus sp. D1 | 0.163 | 0.145 | 0.138 | 0.145 | 0.157 | 0.149 | 0.200 | 0.149 | 0.163 | | | | | | | | | | | | | | | |
Plusioglyphiulus sp. D18 | 0.178 | 0.155 | 0.158 | 0.164 | 0.160 | 0.176 | 0.133 | 0.178 | 0.173 | 0.169 | | | | | | | | | | | | | | |
Plusioglyphiulus sp. D14 | 0.190 | 0.166 | 0.170 | 0.188 | 0.170 | 0.182 | 0.190 | 0.172 | 0.167 | 0.193 | 0.179 | | | | | | | | | | | | | |
Plusioglyphiulus phra | 0.155 | 0.135 | 0.138 | 0.139 | 0.123 | 0.152 | 0.170 | 0.152 | 0.127 | 0.143 | 0.148 | 0.161 | | | | | | | | | | | | |
Plusioglyphiulus sp. D6 | 0.160 | 0.154 | 0.143 | 0.146 | 0.157 | 0.145 | 0.181 | 0.151 | 0.130 | 0.145 | 0.161 | 0.175 | 0.136 | | | | | | | | | | | |
Plusioglyphiulus sp. D16 | 0.172 | 0.170 | 0.161 | 0.173 | 0.163 | 0.164 | 0.181 | 0.160 | 0.173 | 0.164 | 0.175 | 0.155 | 0.164 | 0.149 | | | | | | | | | | |
Plusioglyphiulus sp. D7 | 0.164 | 0.151 | 0.164 | 0.161 | 0.170 | 0.167 | 0.205 | 0.164 | 0.158 | 0.155 | 0.188 | 0.155 | 0.155 | 0.115 | 0.164 | | | | | | | | | |
Plusioglyphiulus sp. D15 | 0.191 | 0.169 | 0.176 | 0.193 | 0.170 | 0.188 | 0.187 | 0.173 | 0.161 | 0.203 | 0.185 | 0.040 | 0.167 | 0.179 | 0.167 | 0.169 | | | | | | | | |
Plusioglyphiulus sp. D20 | 0.188 | 0.161 | 0.167 | 0.190 | 0.170 | 0.181 | 0.187 | 0.169 | 0.167 | 0.190 | 0.175 | 0.009 | 0.158 | 0.176 | 0.152 | 0.157 | 0.046 | | | | | | | |
Plusioglyphiulus sp. D13 | 0.193 | 0.169 | 0.170 | 0.197 | 0.176 | 0.187 | 0.194 | 0.170 | 0.170 | 0.191 | 0.184 | 0.019 | 0.167 | 0.182 | 0.160 | 0.161 | 0.054 | 0.016 | | | | | | |
Plusioglyphiulus sp. D5 | 0.149 | 0.154 | 0.142 | 0.130 | 0.145 | 0.143 | 0.176 | 0.138 | 0.103 | 0.154 | 0.164 | 0.161 | 0.149 | 0.130 | 0.148 | 0.155 | 0.166 | 0.163 | 0.161 | | | | | |
Plusioglyphiulus sp. D11 | 0.051 | 0.132 | 0.141 | 0.146 | 0.152 | 0.133 | 0.181 | 0.152 | 0.149 | 0.158 | 0.182 | 0.188 | 0.161 | 0.158 | 0.176 | 0.161 | 0.184 | 0.187 | 0.191 | 0.158 | | | | |
Plusioglyphiulus sp. D2 | 0.151 | 0.142 | 0.142 | 0.118 | 0.139 | 0.123 | 0.182 | 0.127 | 0.111 | 0.138 | 0.163 | 0.182 | 0.146 | 0.117 | 0.160 | 0.143 | 0.178 | 0.182 | 0.182 | 0.127 | 0.142 | | | |
Plusioglyphiulus sp. D19 | 0.172 | 0.157 | 0.160 | 0.157 | 0.175 | 0.176 | 0.130 | 0.170 | 0.170 | 0.179 | 0.054 | 0.188 | 0.151 | 0.169 | 0.181 | 0.187 | 0.196 | 0.184 | 0.187 | 0.172 | 0.172 | 0.172 | | |
Plusioglyphiulus wat | 0.160 | 0.138 | 0.148 | 0.155 | 0.158 | 0.154 | 0.185 | 0.146 | 0.151 | 0.146 | 0.178 | 0.161 | 0.148 | 0.160 | 0.182 | 0.178 | 0.164 | 0.160 | 0.164 | 0.143 | 0.158 | 0.155 | 0.175 | |
Plusioglyphiulus steineri | 0.166 | 0.148 | 0.154 | 0.172 | 0.157 | 0.167 | 0.164 | 0.169 | 0.175 | 0.166 | 0.143 | 0.167 | 0.157 | 0.158 | 0.166 | 0.160 | 0.167 | 0.164 | 0.170 | 0.175 | 0.166 | 0.161 | 0.157 | 0.152 |
Plusioglyphiulus sp. D17 | 0.178 | 0.166 | 0.178 | 0.176 | 0.172 | 0.172 | 0.093 | 0.191 | 0.166 | 0.187 | 0.129 | 0.188 | 0.164 | 0.181 | 0.182 | 0.202 | 0.193 | 0.185 | 0.190 | 0.175 | 0.182 | 0.175 | 0.136 | 0.191 | 0.167
Taxonomic account
Order Spirostreptida
Family Cambalopsidae Cook, 1895
Genus Plusioglyphiulus Silvestri, 1923
Plusioglyphiulus dubius
(Attems, 1938)
D2FA8FC6-8B69-5950-9B30-524862264F99
- Glyphiulus dubiusAttems, 1938: 272 (D).
- Plusioglyphiulus dubius—Mauriès 1970: 510 (M); 1983: 272 (D); Hoffman 1977: 715 (M); Jeekel 2004: 57 (R); Golovatch et al. 2009: 74 (R); 2011: 4 (L, M); Likhitrakarn et al. 2015: 179 (L); 2020a: 139 (L, M).
Remarks.
Attems (1938) originally described this species as Glyphiulus dubius based on a single female holotype obtained from Angkor, Cambodia. Mauriès (1983) subsequently noted a striking morphological resemblance between P. dubius and P. boutini Mauriès, 1970, distinguishing them primarily by the starting position of the divided dorsal crests (on body ring 6 in P. dubius vs ring 7 in P. boutini). However, because the diagnostic male material remains entirely unavailable, the definitive verification of this species is severely hindered. In the complete absence of male gonopod structures, which are critical for accurate generic and species placement, our current diagnosis must rely exclusively on overall somatic characters and body shape parameters. Until male topotypes are collected to clarify its true identity, P. dubius remains a species of doubtful status within the Cambodian fauna.
Plusioglyphiulus boutini
Mauriès, 1970
6B651AF8-1F0B-53DD-B684-07C78E89281A
- Plusioglyphiulus boutiniMauriès, 1970: 509.
- Plusioglyphiulus boutini—Hoffman 1977: 715; Mauriès 1983: 272; Boutin 2001: 1760; Jeekel 2004: 57; Golovatch et al. 2009: 72; 2011: 4; Likhitrakarn et al. 2015: 179; 2020a: 139 (R, D, M).
Remarks.
This species was originally described from a cave ecosystem near Kampong Trach, Kampot Province, Cambodia (Mauriès 1970). The newly accumulated material documented herein was collected from Phnom Kampong Trach Cave and Prasat Phnom Totong Temple, located only ~ 17 km away from the type locality. As illustrated in our updated distribution map (Fig. 12), these new sampling sites are remarkably close to each other, confirming that the new specimens collected by Likhitrakarn et al. (2020a) represent highly localized populations in immediate geographical proximity. The morphology of the newly examined specimens fully agrees with the original description and details provided by Mauriès (1970).
Plusioglyphiulus biserratus
Likhitrakarn, Golovatch, Thach, Chhuoy, Ngor, Srisonchai, Sutcharit & Panha, 2020
21DA0F5B-EE17-501A-ADB9-97CCE42254B5
- Plusioglyphiulus biserratusLikhitrakarn et al., 2020a: 141 (D).
Remarks.
This distinct cavernicolous species was originally described from Phnom Kbal Romeas Cave in Tuek Chhou District, Kampot Province, southern Cambodia (Likhitrakarn et al. 2020a). Based on topotypic material, P. biserratus is confirmed as a narrow endemic species strictly confined to its isolated type locality, underscoring a pronounced pattern of cave micro-endemism within the fragmented karst towers of Indochina. Despite its strict localization, the diagnostic features of this species remain exceptionally stable across all examined populations, standing out sharply from all other known Cambodian congeners by its unique male gonopods, particularly the simplified, single-structured anterior processes and the distinctly serrate apicolateral margins of the posterior gonopodal telopodites.
Plusioglyphiulus khmer
Likhitrakarn, Golovatch, Thach, Chhuoy, Ngor, Srisonchai, Sutcharit & Panha, 2020
FCC04BA6-6CA7-542F-A07D-1B422C0ACB36
- Plusioglyphiulus khmerLikhitrakarn et al., 2020a: 144 (D).
Remarks.
This remarkable species was originally described from Phnom Sorsia Temple Cave in Damnak Chang’aeur District, Kep Province, southern Cambodia (Likhitrakarn et al. 2020a). The morphology of P. khmer is distinctive within the genus, being readily distinguished from all other known Cambodian congeners by its complete and entirely undivided longitudinal crests on the collum. This conspicuous configuration provides a strong diagnostic contrast to the regional congeners, which always show divided and incomplete crests. Furthermore, the species is characterized by a complex arrangement of long, slender coxosternal processes (cxp1 and cxp2) of the anterior gonopods.
Plusioglyphiulus parviserratus
Likhitrakarn & Seesamut sp. nov.
52245CC1-46C4-5D82-BA7A-00A5C1751D16
https://zoobank.org/AE7C6DD1-F369-4748-A9F6-27C11ED7C5A1
Figs 2A, 3–7
- Plusioglyphiulussp. D9: Seesamut et al. 2026: 9 (MI).
Type material.
Holotype. • ♂ (CUMZ-CAM236), Cambodia, Battambang Province, Banan District, Phum Thmei, Wat La-ang Phnom Takream (locality code C104), 13°04'27"N, 103°03'32"E, 01.08.2024, leg. C. Sutcharit and R. Srisonchai. Paratypes. • 26 ♂, 43 ♀ (CUMZ-CAM236), same locality, together with holotype.
Figure 2.: Habitus, live coloration. A. Plusioglyphiulus parviserratus sp. nov., ♂ paratype; B. Plusioglyphiulus battambangensis sp. nov., ♀ paratype. All pictures by R. Srisonchai, not taken to scale.
Diagnosis.
This new species seems to be especially closely related to Plusioglyphiulus likhitrakarni Golovatch, Geoffroy, Mauriès & VandenSpiegel, 2011, a species described from eastern Thailand, sharing with the latter congener the highly similar general somatic characters and gonopod configuration. Both species, however, can be distinguished by a lower number of ommatidia rows, each eye patch with only 7–16 ommatidia arranged in 2–3 longitudinal rows (Figs 3A, 3C, 6C–E, 6G) (vs 15–22 ocelli arranged in 5–6 longitudinal rows in P. likhitrakarni), and by the distinct carinotaxic formula of the collum: (1a)/t+2p/t+3(3p/t)+4(4p/t)+ta/t+(5p)/t/t+ta/t+pp/(t)/t+m/m (Figs 3A, 3B, 4B, 6A–C, 6F, 6G) (compared to //(t)+1p/t//t+/(t)/t+2p//t+/(t)/t+3p//(t)/t+/(t)/t+4p/(t)/t+pp/t (or pp/(t)/t)+/ma/ma/m in P. likhitrakarni). They also differ in the carinotaxy of the midbody metaterga, with the formula of metatergum 5 and subsequent ones, except for the last few rings, usually following the pattern of 3/3+I/i+3/3/3+m/m (Figs 3A, 3B, 3D–H, 6A–C) (as opposed to 4/4+I/i+3/3/3+m/m in P. likhitrakarni). Furthermore, the telopodites of male legs 1 are distinctly 2-segmented (Figs 4D, 4E, 5A–D) (vs 1-segmented in P. likhitrakarni), and the anterior coxosternal processes (cxp1) of the anterior gonopods are regularly curved anteriorly, vividly resembling a bird’s head (Figs 4I, 4J, 5E–J), whereas they are characteristically contiguous and digitiform in P. likhitrakarni.
Figure 3.: Plusioglyphiulus parviserratus sp. nov., ♂ paratype. A–C. Anterior part of body, lateral, dorsal, and ventral views, respectively; D, E. Midbody segments, dorsal and lateral views, respectively; F. Cross-section of a midbody segment; G–I. Posterior part of body, lateral, dorsal, and ventral views, respectively.
Figure 4.: Plusioglyphiulus parviserratus sp. nov., ♂ holotype. A. Gnathochilarium, ventral view; B. Collum, dorsal view; C. Antenna, lateral view; D, E. ♂ legs 1, anterior and posterior views, respectively; F. ♂ legs 2, posterior view; G. ♂ legs 3, posterior view; H. Midbody rings, ventral view; I, J. Anterior gonopods, posterior and anterior views, respectively; K, L. Posterior gonopods, posterior and anterior views, respectively. Abbreviations: ap = anterior coxal process, cxp 1 = anterior coxosternal processes, cxp 2 = posterior coxosternal processes, f = flagellum process, pp = paramedian coxal process, te = telopodite. Scale bars: 0.1 mm.
Figure 5.: Plusioglyphiulus parviserratus sp. nov., ♂ holotype (A–C, H–M), ♂ paratype (E–G). A, B, D. Legs 1, subcaudal, frontal and sublateral views, respectively; C. Leg 1, frontal view; E–G. Anterior and posterior gonopods, anterior, subposterior and sublateral views, respectively; H–J. Anterior gonopods, frontal, caudal and lateral views, respectively; K–M. Posterior gonopods, subfrontal, caudal and lateral views, respectively.
Figure 6.: Plusioglyphiulus parviserratus sp. nov., ♂ male paratype, shaded surface display volume renderings based on 3DµCT models. A–D. Anterior part of body, lateral, sublateral, dorsal and ventral views, respectively; E. Head and anterior part of body, ventral view; F, G. Collum and anterior part of body, dorsal and lateral views, respectively. Scale bars: 0.1 mm.
Description.
Length of holotype, 28.2 mm; of adult paratypes, 19.4–35.3 mm (♂) or 20.5–40.4 mm (♀); midbody rings round in cross-section (Fig. 3F), their width (horizontal diameter) and height (vertical diameter) similar, width in holotype 1.6 mm; paratypes 1.3–1.8 mm (♂) or 1.6–1.9 mm (♀).
Coloration of live animals light brown (Fig. 2A), with darker lateral sides and a narrow median line; head and anterior body rings (rings 1–6) usually darker brownish; antennae, venter, and legs light yellowish (Fig. 2A). Coloration in alcohol, after two years of preservation (Fig. 3A–I), fading to uniformly reddish brown or dark castaneous brown to grey-brown, with the median line, porosteles, and surrounding areas usually dark brownish (Fig. 3A, B, D, E, G, H); antennae and venter yellow-brownish to brownish (Fig. 3A–C, E–G, I); eyes dark brown to blackish (Fig. 3A, C).
Adult body with 50p+4a+T (holotype); paratypes with 53–74p+1–5a+T (♂) or 54–79p+2–3a+T (♀). Eye patches transversely ovoid, with 7–16 flat ommatidia arranged in 2–3 longitudinal rows (Figs 3A, 3C, 6A, 6D, 6E, 6G). Clypeus with three teeth anteromedially (Figs 3C, 6D, 6E).
Antennae short and clavate (Figs 3A–C, 4C, 6A, 6D, 6E, 6G), extending to ring 2 laterally, antennomeres 5 and 6 each with a small apicodorsal field or corolla of bacilliform sensilla (Fig. 4C). Gnathochilarium oligotrichous, each lamella lingualis with 2–3 setae; promentum bare, separated from eumentum by a distinct transverse suture (n = 2) (Fig. 4A).
Postcollum constriction evident, but collum moderately enlarged (Figs 2A, 3B, 3C, 6A–F). Carinotaxic formula of collum: (1a)/t+2p/t+3(3p/t)+4(4p/t)+ta/t+(5p)/t/t+ta/t+pp/(t)/t+ma/m (Figs 3A, 3B, 4B, 6A–C, 6F, 6G). Carinotaxy of metatergum 2: 8/8+m/m+8/8; metatergum 3: 8/7+m/m+8/7; metatergum 4: 7/7+m/m+7/7 (Figs 3A, 3B, 6A–C, 6F, 6G). Metatergal formula 5 and subsequent ones, except for the last few rings, usually 3/3+I/i+3/3/3+m/m+3/3/3+I/i+3/3 (Figs 3A, 3B, 3D–H, 6A–C); that of legless rings usually 7+m+7 (Fig. 5G, H). All crests and tubercles rather low (Figs 3A, 3B, 3D–H, 6A–C, 6F, 6G). Porosteles large, low, conical, rounded, directed anterolaterad, and higher than wide (Figs 3A, 3B, 3D–H, 6A–C). Midbody rings subcircular in cross-section, virtually uncompressed laterally (Fig. 3F).
Tegument finely alveolate-areolate (Figs 3A, 3B, 3D, 3E, 3G, 3H, 6A–C, 6F, 6G), dull throughout. Metatergal setae absent. Pleural regions of rings 2–4 elongated, flap-shaped, especially prominent on ring 3 (Figs 3A, 3C, 6A, 6D).
Epiproct (Fig. 3G, H) broadly rounded apically, with 2+2 paramedian tubercles, the median tubercles larger than the lateral ones. Paraprocts smooth, regularly convex, and densely setose (Fig. 3G, I). Hypoproct transversely bean-shaped, concave posteriorly (Fig. 3I).
Ventral flaps behind gonopod aperture on male ring 7 evident (Figs 3A, 3C, 6A, 6D), distinguishable as low swellings with rounded lobes bent abruptly posteriorly.
Legs short, ~ 2/3 as long as body diameter (Figs 3F, 4H); claw with a strong, spiniform, accessory claw at base, the latter almost half as long as claw itself (Fig. 4H).
Male legs 1 with a usual, strong, and long central hook (actually a pair of tightly appressed hooks) regularly curved anteriorly; a pair of strong, sac-shaped, 2-segmented telopodites nearly half as long as central hook (Figs 4D, 4E, 5A–D, 7E–H), with a small second telopoditomere retained as a rudimentary knob (Figs 4D, 4E, 5A–C).
Figure 7.: Shaded surface display volume renderings from 3DµCT data showing the diagnostic character matrix of Plusioglyphiulus parviserratus sp. nov., male paratype. A–D. Anterior part of body in lateral, sublateral, dorsal, and ventral views, respectively (the internal structures exposed via virtual dissection). Distinct anatomical components are schematically color-coded to visualize structural boundaries: leg 1 (purple), leg 2 (green), leg 3 (yellow), and the anterior and posterior gonopods (red); E. Legs 1–3 in situ, anterior view; F–H. Legs 1, posterior, anterior, and lateral views, respectively; I. Leg 2, anterior view; J. Leg 3, anterior view; K–M. Anterior and posterior gonopods, anterior, posterior, and sublateral views, respectively. Scale bars: 0.1 mm.
Male legs 2 strongly enlarged, with high and large coxae; telopodites hirsute on anterior face; penes broad, oblong-subtrapeziform, fused at base (Figs 4F, 6D, 7E, 7I).
Male legs 3 modified as usual, with particularly elongate and slender coxae, and shortened telopodites (Figs 4G, 6D, 7E, 7J).
Anterior gonopods (Figs 4I, 4J, 5E–J) rather complex; coxosternal halves in contact, but not completely fused medially (Figs 4I, 4J, 5E, 5H, 5I). Anterior coxosternal processes (cxp1) forming a paramedian pair, long, slender, erect, setose only apically, and regularly curved anteriorly, resembling a bird’s head (Figs 4J, 5E, 5G, 5H, 5J). Posterior coxosternal processes (cxp2) higher, distally lamellate, with the apices rounded and turned laterally (Figs 4I, 4J, 5F, 5H, 5I). Telopodites (te) club-shaped, subcylindrical, movable, 1-segmented, apically setose, and shorter than cxp2 (Figs 4I, 4J, 5E–J).
Posterior gonopods (Figs 4K, 4L, 5E–G, 5K–M) compact, shorter; coxosternum well separated from sternum, fused only basally. Each coxite with an evident, stout, paramedian coxal process (pp) acute distally and directed laterally (Figs 4K, 5F, 5K–M). Anterior coxal process (ap) lamellate, subquadrate (Figs 4K, 4L, 5E–G, 5K–M), bearing a high, broad flagellum process (f) with the apex distinctly revolute laterally and a micro-serrate upper margin. (Figs 4K, 4L, 5E–G, 5K–M). Telopodite (te) elongate, membranous, apically rounded, with lateral margins slightly rugose, distinctly higher than both pp and ap (Figs 4K, 4L, 5E–G, 5K–M).
Habitat.
The specimens were collected in the dark zone of the cave, exclusively on bat guano deposits. The cave environment maintains high humidity and stable ambient temperatures throughout the year, characteristic of the limestone karst systems in Battambang Province, Cambodia.
Etymology.
The specific epithet is a Latinized adjective derived from a combination of the Latin prefix parvi- (meaning small) and the adjective serratus (meaning saw-like), highlighting the distinct micro-serrate upper margin of the broad flagellum process (f) of the posterior gonopods; adjective.
Remarks.
Morphologically, Plusioglyphiulus parviserratus sp. nov. seems to be especially similar to P. likhitrakarni, a congener originally described from eastern Thailand, with which it shares a remarkably similar general somatic characters and the basic structure of the gonopods. However, the new species is readily distinguishable from P. likhitrakarni by its unique carinotaxic pattern on the collum and midbody metaterga, as well as a significantly reduced number of ommatidia.
This sharp morphological differentiation is robustly supported by molecular data; the uncorrected pairwise p-distance between P. parviserratus sp. nov. and P. likhitrakarni at the COI barcode locus yields a significant divergence of 9.9% (Table 1). Although this value closely approaches the lower threshold of the typical interspecific distances separating valid congeners within Plusioglyphiulus (which generally range between 11.4% and 18.2%, with a mean interspecific divergence of 14.5%–15.1% depending on the species group (Seesamut et al. 2026)), such a substantial genetic gap coupled with the diagnostic boundaries fully corroborates the independent evolutionary status of the newly described taxon.
Plusioglyphiulus battambangensis
Likhitrakarn & Seesamut sp. nov.
D8533F7D-85E3-544A-B001-0E112D6221FB
https://zoobank.org/AC99FBFA-A37B-4580-BB94-FDECF2945F6D
Figs 2B, 8–11
- Plusioglyphiulussp. D8: Seesamut et al. 2026: 9 (MI).
Type material.
Holotype. • ♂ (CUMZ-CAM237), Cambodia, Battambang Province, Banan District, Phumi Thnong, Asram Kompir Temple (locality code C105), 13°05'44"N, 102°55'32"E, 01.08.2024, leg. C. Sutcharit and R. Srisonchai. Paratypes. • 17 ♂, 35 ♀ (CUMZ-CAM237), same locality, together with holotype.
Diagnosis.
This new species seems to be especially similar to Plusioglyphiulus parviserratus sp. nov. in both somatic characters and the structure of the posterior gonopods. Both species, however, can be distinguished by the carinotaxic formula of the collum: 1a/t+2p/t+3p/t/(t)+4p/(t)/t+(ta)/tc/t+5p/(t)/t+ta/t+pp/t/t+m/m (Figs 8A, 8B, 9B, 11A–C, 11F, 11G) (compared to (1a)/t+2p/t+3(3p/t)+4(4p/t)+ta/t+(5p)/t/t+ta/t+pp/(t)/t+m/m (Figs 3A, 3B, 4B, 6A–C, 6F, 6G)), and by having the small second telopoditomere on the male legs 1 significantly smaller (Figs 9D, 9E, 10A–C) (as opposed to larger (Figs 4D, 4E, 5A–C)). Additionally, the posterior gonopod of the new species displays an elongated and slender paramedian coxal process (pp) (Figs 9K, 10L, 10M), in contrast to the more stout one in P. parviserratus sp. nov. (Figs 4K, 5F, 5K–M), also showing a narrow flagellum process (f) provided with a smooth upper margin (Figs 9K, 9L, 10K–M) (vs broad and with a micro-serrate upper margin (Figs 4K, 4L, 5E–G, 5K–M) in P. parviserratus sp. nov.).
Figure 8.: Plusioglyphiulus battambangensis sp. nov., ♂ paratype. A–C. Anterior part of body, lateral, dorsal, and ventral views, respectively; D, E. Midbody segments, dorsal and lateral views, respectively; F. Cross-section of a midbody segment; G–I. Posterior part of body, lateral, dorsal, and ventral views, respectively.
Figure 9.: Plusioglyphiulus battambangensis sp. nov., ♂ paratype (A, B), ♂ holotype (C–L). A. Gnathochilarium, ventral view; B. Collum, dorsal view; C. Antenna, lateral view; D, E. ♂ legs 1, anterior and posterior views, respectively; F. ♂ legs 2, posterior view; G. ♂ legs 3, posterior view; H. Midbody rings, ventral view; I, J. Anterior gonopods, posterior and anterior views, respectively; K, L. Posterior gonopods, posterior and anterior views, respectively. Abbreviations: ap = anterior coxal process, cxp 1 = anterior coxosternal processes, cxp 2 = posterior coxosternal processes, f = flagellum process, pp = paramedian coxal process, te = telopodite. Scale bars: 0.1 mm.
Figure 10.: Plusioglyphiulus battambangensis sp. nov., ♂ holotype (A–G, K–M), ♂ paratype (H–J). A, B, D. Legs 1, caudal, subfrontal and sublateral views, respectively; C. Leg 1, subfrontal view; E–J. Anterior gonopods, subfrontal, caudal, sublateral, frontal, subcaudal and sublateral views, respectively; K–M. Posterior gonopods, frontal, caudal and sublateral views, respectively.
Figure 11.: Plusioglyphiulus battambangensis sp. nov., ♂ male paratype, shaded surface display volume renderings based on 3DµCT models. A–D. Anterior part of body, lateral, sublateral, dorsal and ventral views, respectively; E. Head and anterior part of body, ventral view; F, G. Collum and anterior part of body, dorsal and lateral views, respectively. Scale bars: 0.1 mm.
Description.
Length of holotype, 29.5 mm; adult paratypes 17.8–41.4 (♂) or 21.8–41.6 mm (♀) long; midbody rings round in cross-section (Fig. 8F), their width (horizontal diameter) shorter than height (vertical diameter), width in holotype 2.2 mm; in paratypes 1.3–1.7 (♂), 1.1–1.9 mm (♀).
Coloration of live animals light brown (Fig. 2B), with darker lateral sides and a narrow median line; head and anterior body rings (rings 1–5) usually darker brownish; antennae, venter, and legs light yellowish (Fig. 2B). Coloration in alcohol, after two years of preservation (Fig. 8A–I), faded to uniformly reddish brown or dark castaneous brown to grey-brown, with the median line, porosteles, and surrounding areas usually dark brownish (Fig. 8A, B, D, E, G, H). Antennae and venter yellow-brownish to brownish (Fig. 8A–C, E–G, I). Eyes dark brown to blackish (Fig. 8A, C).
Adult body with 65p+4a+T (holotype); paratypes with 53–79p+1–5a+T (♂) and 54–76p+2–6a+T (♀). Eye patches transversely ovoid, each provided with 8–12 flat ommatidia arranged in 2–3 longitudinal rows in adults (Figs 8A, 8C, 11D, 11E, 11G). Clypeus with three teeth anteromedially (Figs 8C, 11D).
Antennae short and clavate (Figs 2B, 8A–C, 9C, 11A, 11D–F), extending to ring 2 laterally; antennomeres 5 and 6 each with a small apicodorsal field or corolla of bacilliform sensilla (Fig. 9C). Gnathochilarium oligotrichous, each lamella lingualis with 2–3 setae; promentum bare, separated from eumentum by a distinct transverse suture (n = 2) (Fig. 9A).
Postcollum constriction evident, with the collum only moderately enlarged (Figs 2B, 8A–C, 11B–F). Carinotaxic formula of collum: 1a/t+2p/t+3p/t/(t)+4p/(t)/t+(ta)/tc/t+5p/(t)/t+ta/t+pp/t/t+ma/(ma)/m (Figs 8A, 8B, 9B, 11A–C, 11F, 11G). Carinotaxy of metatergum 2: 8/8+m/m+8/8; metatergum 3: 8/7+m/m+8/7; metatergum 4: 7/7+m/m+7/7 (Figs 8A, 8B, 11A–C, 11F, 11G). Metatergal formula 5 and subsequent ones, except for the last few rings, usually 3/3+I/i+3/3/3+m/m+3/3/3+I/i+3/3 (Figs 8A, 8B, 8D–H, 11A–C); that of legless rings usually 7+m+7 (Fig. 8G, H). All crests and tubercles rather low (Figs 8A, 8B, 8D–H, 11A–G). Porosteles large, low, conical, rounded, directed anterolaterad, and higher than wide (Figs 8D–H, 11A–C, 11G). Midbody rings subcircular in cross-section, virtually uncompressed laterally (Fig. 8F).
Tegument finely alveolate-areolate (Figs 8A, 8B, 8D, 8E, 8G, 8H, 11A–C, 11F, 11G), dull throughout. Metatergal setae absent. Pleural regions of rings 2–4 elongated, flap-shaped, especially clearly so on ring 3 (Figs 8A, 8C, 11A, 11D).
Epiproct (Fig. 8G–I) broadly rounded apically, with 2+2 paramedian tubercles, the inner pair being visibly larger than the outer ones. Paraprocts smooth, regularly convex, and densely setose (Fig. 8G, I). Hypoproct transversely bean-shaped, concave posteriorly (Fig. 8I).
Ventral flaps behind gonopod aperture on male ring 7 evident (Figs 8A, 8C, 11A, 11D), distinguishable as low swellings with rounded lobes bent abruptly posteriorly.
Legs short, ~ 2/3 as long as body diameter (Figs 8F, 9H); claw with a strong, spiniform accessory claw at base, the latter almost half as long as claw itself (Fig. 9H).
Male legs 1 with a usual, prominent, and elongate central hook (actually a pair of tightly appressed hooks) regularly curved anteriorly; a pair of strong, sac-shaped, 2-segmented telopodites nearly half as long as central hook (Figs 9D, 9E, 10A–D), with a small second telopoditomere retained as a rudimentary knob (Figs 9D, 9E, 10A–D).
Male legs 2 strongly incrassate, with high and large coxae; telopodites hirsute on anterior face; penes broad, oblong-subtrapeziform, fused at base (Figs 9F, 11D).
Male legs 3 modified as usual, with particularly elongate and slender coxae, and shortened telopodites (Figs 9G, 11D).
Anterior gonopods (Figs 9I, 9J, 10E–J) rather complex; coxosternal halves in contact, but not completely fused medially (Figs 9I, 9J, 10E, 10F, 10H, 10I). Anterior coxosternal processes (cxp1) forming a paramedian pair, long, slender, erect, setose only apically, and regularly curved anteriorly, resembling a bird’s head (Figs 9J, 10E, 10G, 10H, 10J). Posterior coxosternal processes (cxp2) higher, distally lamellate, with the apices rounded and turned laterally (Figs 9I, 9J, 10E–J). Telopodites (te) club-shaped, subcylindrical, movable, 1-segmented, apically setose, and shorter than cxp2 (Figs 9I, 9J, 10E–J).
Posterior gonopods (Figs 9K, 9L, 10K–M) compact, shorter; coxosternum well separated from sternum, fused only basally. Each coxite with a long, slender, paramedian coxal process (pp) acute distally and directed laterally (Figs 9K, 10L, 10M). Anterior coxal process (ap) lamellate, subquadrate (Figs 9K, 9L, 10K–M), with a high, narrow flagellum process (f) with a smooth upper margin at its apex, the apex itself being distinctly revolute laterally (Figs 9K, 9L, 10K–M). Telopodite (te) erect, elongate, membranous, apically rounded, with lateral margins slightly rugose, distinctly higher than both pp and ap (Figs 9K, 9L, 10K–M).
Habitat.
The specimens were collected in the aphotic zone of the cave, ~ 20 m from the entrance, occurring on moist limestone floor. The cave environment maintains high humidity and stable ambient temperatures throughout the year, characteristic of the limestone karst systems in Battambang Province.
Etymology.
The specific epithet is a Latinized adjective derived from the type locality, Battambang Province, Cambodia, where the type series was collected; adjective.
Remarks.
Morphologically, Plusioglyphiulus battambangensis sp. nov. is remarkably similar to its congener, P. parviserratus sp. nov. Both new species share an extremely uniform habitus, a strong reduction in the number of ommatidia, and highly similar gonopod structures. Such profound morphological conservatism frequently makes phenotypic discrimination between closely related cavernicolous congeners particularly difficult. However, despite these superficial similarities, P. battambangensis sp. nov. can be separated from P. parviserratus sp. nov. by the specific carinotaxic ornamentation of the collum, as well as by the significantly stouter processes of the gonopods, both anterior and posterior.
Among the Cambodian congeners, Plusioglyphiulus battambangensis sp. nov. and P. parviserratus sp. nov. represent clear geographic isolates, being remarkably disjunct from the more southernly distributed cave-dwelling species such as P. boutini Mauriès, 1970, P. biserratus Likhitrakarn et al., 2020, and P. khmer Likhitrakarn et al., 2020 (Fig. 12). Most importantly, the independent status of P. battambangensis sp. nov. is strongly supported by our molecular analysis; the uncorrected pairwise p-distance at the COI barcode locus yields a significant divergence of 10.3% from P. parviserratus sp. nov., a value fully corresponding to the stable species boundaries established for the family Cambalopsidae (Seesamut et al. 2026).
Key to Plusioglyphiulus species currently known to occur in Cambodia
1 | All crests on collum undivided and mostly complete | Plusioglyphiulus khmer Likhitrakarn et al., 2020
– | Crests on collum always divided and incomplete (Figs 3A, 3B, 4B, 6A–C, 6F, 6G, 8A, 8B, 9B, 11A–C, 11F, 11G) | 2
2 | General coloration very dark brown to blackish (fading to reddish after long conservation in alcohol). Paraprocts with a distinct, median, ridge-like elevation | Plusioglyphiulus dubius (Attems, 1938)
– | General coloration lighter, usually yellow-brown to brown (Fig. 2A, B). Paraprocts flat medially | 3
3 | Male leg 1 telopodites 1-segmented | 4
– | Male leg 1 telopodites 2-segmented (Figs 4D, 4E, 5A–D, 9D, 9E, 10A–D) | 5
4 | Male leg 1 with 1-segmented, very long telopodites, the latter almost as long as central hook. Anterior coxal process (ap) and paramedian coxal process (pp) of posterior gonopods suberect, long, slender, flagelliform, and clearly higher than Telopodite (te) | Plusioglyphiulus biserratus Likhitrakarn et al., 2020
– | Male leg 1 telopodites 1-segmented, extremely short, nearly vestigial. Posterior gonopod telopodites otherwise shaped | Plusioglyphiulus boutini Mauriès, 1970
5 | Carinotaxy pattern of collum, (1a)/t+2p/t+3(3p/t)+4(4p/t)+ta/t+(5p)/t/t+ta/t+pp/(t)/t+m/m (Figs 3A, 3B, 4B, 6A–C, 6F, 6G); posterior gonopods with a stouter paramedian coxal process (pp) (Figs 4K, 5F, 5K–M) and a broad flagellum process (f) bearing a micro-serrate upper margin (Figs 4K, 4L, 5E–G, 5K–M) | Plusioglyphiulus parviserratus sp. nov.
– | Carinotaxy pattern of collum, 1a/t+2p/t+3p/t/(t)+4p/(t)/t+(ta)/tc/t+5p/(t)/t+ta/t+pp/t/t+m/m (Figs 8A, 8B, 9B, 11A–C, 11F, 11G); posterior gonopods with a longer and more slender paramedian coxal process (pp) (Figs 9K, 10L, 10M) and a narrow flagellum process (f) bearing a smooth upper margin (Figs 9K, 9L, 10K–M) | Plusioglyphiulus battambangensis sp. nov.