Redescription of the Subterranean Millipede Antrokoreana gujoensis (Diplopoda: Julida: Nemasomatidae) from Central Honshu, Japan Author Kato, Taiga Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606 - 8502, Japan E-mail: tkato @ zoo. zool. kyoto-u. ac. jp & Corresponding author tkato@zoo.zool.kyoto-u.ac.jp Author Nakano, Takafumi Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606 - 8502, Japan E-mail: tkato @ zoo. zool. kyoto-u. ac. jp tkato@zoo.zool.kyoto-u.ac.jp text Species Diversity 2023 2023-04-26 28 1 133 140 http://dx.doi.org/10.12782/specdiv.28.133 journal article 57134 10.12782/specdiv.28.133 caec401c-fdd8-4d38-b20a-529dab919b50 2189-7301 8110140 Antrokoreana gujoensis Masuda, 2010 [Japanese name: Gujo-tateune-horayasude] ( Figs 2–8 ) Antrokoreana gujoensis Masuda, 2010: 29–32 , figs 1, 2; Masuda 2021: 31 (list). Emended diagnosis. This species is clearly distinguishable from all congeners by each distal tip of the posterior gonopods elongate and rake-shaped with 3 or 4 branched-processes (bps; Fig. 7B, C ) and its basal part with 2 tulip-leaf shaped processes (tsps; Fig. 7B, C ) which do not reach the distal end of the posterior gonopod, differs further from its closest congener, A. takakuwai (Verhoeff, 1941) , by its possession of elongate distal tips of posterior gonopods, of which the basal processes do not reach the distal end of each posterior gonopod (compared with short distal tips of posterior gonopods in A. takakuwai ; Shinohara 1973 ). Type locality. Kumaishi-do Cave (cave entrance: ~ 35.74°N , ~ 136.99°E ), Gujo , Gifu Prefecture , Japan ( Masuda 2010 ) . Material examined. In total 32 specimens collected from Gujo , Gifu Prefecture , Japan , were examined: KUZ Z4034 , immature male, Kumaishi-kanko-do Cave (cave entrance: 35.74340°N , 136.99746°E ; near the type locality), 2 December 2021 , leg . Takafumi Nakano ; KUZ Z4340 – Z4346 , 7 males , KUZ Z4347 – Z4358 , 12 females , and KUZ Z4359 , immature female, Miyama Limestone Cave (cave entrance: 35.74971°N , 137.02514°E ), 12 March 2022 , leg . Taiga Kato (TK) and Kohei Kawamura ( KK ); KUZ Z4360 , Z4361 , 2 males , and KUZ Z4362 – Z4364 , 3 females , Otaki Limestone Cave (cave entrance: 35.73494°N , 136.98211°E ), 12 March 2022 , leg . TK and KK; KUZ Z4365 , male, and KUZ Z4366 – Z4370 , 5 females , Gujo Limestone Cave (cave entrance: 35.75343°N , 137.04408°E ), 8 May 2022 , leg . KK. Description. Size and number of body rings. Males: 21.5–29.2 mm long, vertical diameter of largest body ring 1.0– 1.8 mm ; body with 32–45 podous rings + 1 apodous rings + telson. Females: 22.7–33.9 mm long, vertical diameter of largest body ring 1.2–2.3 mm ; body with 32–40 podous rings + 1–2 apodous rings + telson. Head ( Fig. 3 ). Without ommatidia ( Figs 2 , 3A ); with 4 frontal setae. Labrum ( Fig. 3B ) with 2–4 labral teeth, 2–7 supralabral setae and 15–22 labral setae. Mandibular cardo with 1 seta; mandibular stipes without setae, unexpanded in males. Gnathal lobe ( Fig. 3C–E ): external tooth with 4 cusps; internal tooth with 6 cusps ( Fig. 3C ); 6 (4 complete + 2 incomplete) rows of pectinate lamellae ( Fig. 3D ), posterior teeth of each lamella with 2 finger-like branches (OEs) ( Fig. 3E ). Gnathochilarium ( Fig. 3F ) with triangular promentum. Lamellae linguales each with 6 setae in row, stipites each with 3 distolateral setae, without short medial setae. Antennae ( Fig. 3G–I ), in male (KUZ Z4341), 4.6 mm long, ~3.2× longer than vertical diameter of largest body ring, in female (KUZ Z4347), 3.0 mm long, ~2.1× longer than vertical diameter of largest body ring, with 4 apical sensilla. Lengths of antennomeres I–VIII (VIII = apical sensilla) (in mm), in male (KUZ Z4341): 0.17 (I), 0.57 (II), 0.69 (III), 0.64 (IV), 0.66 (V), 0.54 (VI), 0.44 (VII) and 0.09 (VIII). Length/width ratio of antennomeres I–VII, in male (KUZ Z4341): 1.0 (I), 3.4 (II), 3.7 (III), 4.4 (IV), 4.1 (V), 3.3 (VI) and 3.2 (VII). Antennomeres V–VI ( Fig. 3H ) each with terminal corolla of large sensilla basiconica bacilliformia (sbb); antennomere VII ( Fig. 3I ) whole surface covered with numerous short sensilla chaetica among longer sensilla trichodea. Fig. 2. Antrokoreana gujoensis , female (A: KUZ Z4363) and male (B: KUZ Z4340). A, Habitus of live animal in natural habitat; B, habitus of live animal (photograph taken by T. Jonishi), scale bar: 5 mm. Fig. 3. Antrokoreana gujoensis , males (A–E, H, I: KUZ Z4341; F, G: KUZ Z4343). A, Head, frontal view; B, labrum, frontal view; C, right mandible, ventral view; D, mandibular gnathal lobe of left mandible, anterior view; white arrowheads indicate complete pectinate lamellae, black arrowheads donate incomplete lamellae; E, mandibular gnathal lobe of right mandible, posterior view; F, gnathochilarium, ventral view; G, right antenna, sub-mesal view; H, antennomeres V–VI, showing a corolla of large sensilla basiconica bacilliformia at each distal margin; I, antennomere VII, showing short sensilla chaetica and longer sensilla trichodea. Abbreviations: OEs, finger-like branches; sbb, sensilla basiconica bacilliformia. Scale bars: A, B, 250 µm; C, I, 100µm; D, E, 50 µm; F, H, 200µm; G, 500µm. Fig. 4. Antrokoreana gujoensis , males (A, D: KUZ Z4343; B, C, E, F: KUZ Z4341). A, Body ring 5 and 6, lateral view; B, first leg pair, posterior view; C, third leg pair, posterior view, white arrowheads indicate adhesive pads; D, penes, posterior view; E, caudal end with 4 podous rings +1 apodous ring + telson, lateral view; F, telson, ventral view. Scale bars: A, E, F, 500µm; B, C, 200 µm; D, 50 µm. Collum . With whorl of 8 setae located about one-tenth of collum length from posterior margin. Body rings ( Fig. 4A ). Metazona dorsal surface smooth, ventral surface with 4–7 longitudinal striae; with posterior marginal whorl of very short setae, length of mid-body setae ~1.8% of vertical diameter of rings; 1 pair of ozopores present at center of lateral surface of each metazona of 6th ring to ultimate podous ring ( Fig. 2 ). Sternum of each ring, free from pleurotergum, with wing-like expansions anteriorly. Legs ( Fig. 4B–D ). In KUZ Z4341, mid-body legs ~2.2× longer than vertical diameter of ring; relative podomere lengths (prefemur to claw): 1.0: 1.75: 0.9: 1.0: 1.3: 0.4 (leg-pair 10). Claw slender, ~4.1× longer than height (KUZ Z4341); with accessory claw. In males, tibia of leg-pair 1 with 1 long spine directed proximad ( Fig. 4B ). Femur, postfemur, and tibia of following legs each with adhesive pad ( Fig. 4C ). Penes ( Fig. 4D ) shorter than coxae of leg-pair 2, each with 0 or 1 microsetae apically. Telson ( Fig. 4E, F ). Preanal ring without projection, with marginal whorl of setae and 5 additional dorsal setae in front of marginal whorl. Anal valves rounded, each with 7 setae; subanal scale semi-circular, without any modifications, with 2 setae. Gonopods ( Figs 5–7 ). Both anterior and posterior gonopods projecting ventrad. Anterior gonopods ( Figs 5 , 6 ): each coxal process (cp) not expanded distally, distal part rounded ( Fig. 6C ), with several microsetae on posterior surface ( Fig. 5A ), posterior part curved mesad ( Fig. 5B ); telopodite (tl) slender, finger-shaped, composed of single article, with several long setae on distal margin, field of spine-like setae absent; each flagellum (fl) with minute spinules (sps) distally ( Fig. 6D ). Posterior gonopods ( Fig. 7 ) slender, straight, with 1 longitudinal furrow, field of spine-like setae absent; anterior surface covered with minute scale-like processes (slps); posterior surface smooth, with 4 long bristles (lbs) on distal part, reaching apex of each posterior gonopod; distal tip elongate and rake-shaped with 3 or 4 branched-processes (bps), and its basal part with 2 tulip-leaf shaped processes (tsps), which do not reach the distal end. Vulvae ( Fig. 8 ). Pyriform, located inside body ring 3. Operculum (op) slightly longer than bursa, anterior surface of distal part with 4 setae located in 2 longitudinal rows ( Fig. 8A, B ). Bursa with 3–5 setae around central funnel. Receptaculum seminis (rs) single, long, claviform ( Fig. 8C ). Coloration. In life, yellowish brown with the defense glands visible by transparency as reddish spots ( Fig. 2 ). In ethanol, yellowish white. Genetic distances. The male and female specimens in each cave shared identical COI sequences, and therefore clearly belong to the same species. The COI sequence from the specimen collected from Kumaishi-kanko-do Cave and those from specimens collected from Otaki Limestone Cave were identical. The COI uncorrected p -distances are shown in Table 2 . The COI uncorrected p -distance was 1.2% between the specimens collected from Kumaishi-kanko-do Cave and from Gujo Limestone Cave, 1.7% between the specimens collected from Kumaishi-kanko-do Cave and from Miyama Limestone Cave, and 0.5% between the specimens collected from Gujo Limestone Cave and from Miyama Limestone Cave. Distribution. Known from seven caves located in the Mino Terrane in Gifu Prefecture , Japan : six caves, i.e., Kumaishi-do Cave ( type locality), Okugo-do Cave, Miyama Limestone Cave (= Sakabe-do Cave) ( Masuda 2010 , 2021 ), Gujo Limestone Cave, Kumaishi-kanko-do Cave, Otaki Limestone Cave at Gujo, and Inui-no-ana Cave at Yamagata ( Masuda 2010 , 2021 ). Fig. 5. Antrokoreana gujoensis , male (KUZ Z4341). A, Anterior gonopods, anterior view; B, anterior gonopods, posterior view. Abbreviations: cp, coxal process; fl, flagellum; tl, telopodite. Scale bars: A, B, 250 µm. Fig. 6. Antrokoreana gujoensis , males (A, B: KUZ Z4341; C: KUZ Z4343; D: KUZ Z4344). A, Anterior gonopods, anterior view; B, anterior gonopods, posterior view; C, anterior gonopods, right lateral view; D, tip of right flagellum of anterior gonopods. Abbreviations: cp, coxal process; fl, flagellum; sps, spinules; tl, telopodite. Scale bars: A–C, 250µm; D, 25µm. Remarks. The present specimens unquestionably belong to Antrokoreana given that they possess the diagnostic feature of the genus defined by Enghoff (1985) , i.e., the antennomere VII covered with short sensilla chaetica among longer sensilla trichodea. Additionally, the present male specimens clearly possess a pair of penes behind the coxae of leg-pair 2, but nonetheless, all the specimens collected from the caves at Gujo can be undoubtedly identified as A. gujoensis because the shape of their posterior gonopods is coincident with that of A. gujoensis as described by Masuda (2010 : fig. 2B). Indeed, the presence of a pair of penes in males is consistent with the placement of the species in the julidan family Nemasomatidae . Based on the morphological characters provided in the original description of A. gujoensis ( Masuda 2010 ) , the species was indistinguishable from A. takakuwai which is endemic to montane habitats around Mt. Fuji in Honshu ( Shinohara 1973 ). Fig. 7. Antrokoreana gujoensis , males (A, B: KUZ Z4365; C: KUZ Z4360). A, Right posterior gonopod, lateral view; B, apical part of right posterior gonopod, lateral view; C, apical part of left posterior gonopod, lateral view. Abbreviations: bps, branched-processes; lbs, long bristles; slps, scale-like processes; tsps, tulip-leaf shaped processes. Scale bars: A, 100 µm; B, C, 50µm. Fig. 8. Antrokoreana gujoensis , females (A, B: KUZ Z4349; C: KUZ Z4347). A, Right vulva, posterior view; B, left vulva, mesal view; C, left vulva, lateral view, broken line outlines the receptaculum seminis. Abbreviations: bu, bursa; op, operculum; rs, receptaculum seminis. Scale bars: A, B, 100µm; C, 200µm. Table 2. Uncorrected p -distances (%) for COI sequences among the specimens of Antrokoreana gujoensis collected from different caves (locality numbers, see Fig. 1) in central Honshu, Japan.

Locality	1	2	3
1. Kumaishi-kanko-do Cave
2. Otaki Limestone Cave	0.0
3. Gujo Limestone Cave	1.2	1.2
4. Miyama Limestone Cave	1.7	1.7	0.5

A recent study of Antrokoreana showed that A. asuwaensis possesses 4 complete + 2 incomplete pectinate lamellae of the mandibular gnathal lobes, a triangular promentum of gnathochilarium, minute spinules on the distal tips of flagella of anterior gonopods, and a long claviform receptaculum seminis of vulva, suggesting the possibility that these features would be shared with the other congeners ( Kato et al. 2022 ). The present results corroborate this hypothesis, since A. gujoensis also possesses these morphological features. The COI sequences from the specimens collected from the two western caves (Kumaishi-kanko-do Cave and Otaki Limestone Cave; Fig. 1 ) were identical. In contrast, the COI uncorrected p -distances between the specimens inhabiting the two western caves and those in the two eastern caves (Gujo Limestone Cave and Miyama Limestone Cave; Fig. 1 ) were 1.2%–1.7%. The results suggest gene flow between the Antrokoreana millipedes in the two western caves.