Antrokoreana gujoensis Masuda, 2010

Kato, Taiga & Nakano, Takafumi, 2023, Redescription of the Subterranean Millipede Antrokoreana gujoensis (Diplopoda: Julida: Nemasomatidae) from Central Honshu, Japan, Species Diversity 28 (1), pp. 133-140 : 134-139

publication ID	https://doi.org/ 10.12782/specdiv.28.133
DOI	https://doi.org/10.5281/zenodo.8109605
persistent identifier	https://treatment.plazi.org/id/03C3B02A-FFF8-FF90-FEC4-E86CFD2AFBE6
treatment provided by	Felipe
scientific name	Antrokoreana gujoensis Masuda, 2010
status

Treatment

Antrokoreana gujoensis Masuda, 2010 [Japanese name: Gujo-tateune-horayasude] ( Figs 2–8 View Fig View Fig View Fig View Fig View Fig View Fig View Fig )

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 View Fig ) and its basal part with 2 tulip-leaf shaped processes (tsps; Fig. 7B, C View Fig ) 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) GoogleMaps .

Material examined. In total 32 specimens collected from Gujo, Gifu Prefecture, Japan, were examined: KUZ Z4034 View Materials , immature male, Kumaishi-kanko-do Cave (cave entrance: 35.74340°N, 136.99746°E; near the type locality), 2 December 2021, leg GoogleMaps . Takafumi Nakano; KUZ Z4340 View Materials – Z4346 View Materials , 7 males, KUZ Z4347 View Materials – Z4358 View Materials , 12 females, and KUZ Z4359 View Materials , immature female, Miyama Limestone Cave (cave entrance: 35.74971°N, 137.02514°E), 12 March 2022, leg GoogleMaps . Taiga Kato (TK) and Kohei Kawamura ( KK); KUZ Z4360 View Materials , Z4361 View Materials , 2 males, and KUZ Z4362 View Materials – Z4364 View Materials , 3 females, Otaki Limestone Cave (cave entrance: 35.73494°N, 136.98211°E), 12 March 2022, leg GoogleMaps . TK and KK; KUZ Z4365 View Materials , male, and KUZ Z4366 View Materials – Z4370 View Materials , 5 females, Gujo Limestone Cave (cave entrance: 35.75343°N, 137.04408°E), 8 May 2022, leg GoogleMaps . 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 View Fig ). Without ommatidia ( Figs 2 View Fig , 3A View Fig ); with 4 frontal setae. Labrum ( Fig. 3B View Fig ) 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 View Fig ): external tooth with 4 cusps; internal tooth with 6 cusps ( Fig. 3C View Fig ); 6 (4 complete + 2 incomplete) rows of pectinate lamellae ( Fig. 3D View Fig ), posterior teeth of each lamella with 2 finger-like branches (OEs) ( Fig. 3E View Fig ). Gnathochilarium ( Fig. 3F View Fig ) 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 View Fig ), 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 View Fig ) each with terminal corolla of large sensilla basiconica bacilliformia (sbb); antennomere VII ( Fig. 3I View Fig ) whole surface covered with numerous short sensilla chaetica among longer sensilla trichodea.

Collum. With whorl of 8 setae located about one-tenth of collum length from posterior margin.

Body rings ( Fig. 4A View Fig ). 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 View Fig ). Sternum of each ring, free from pleurotergum, with wing-like expansions anteriorly.

Legs ( Fig. 4B–D View Fig ). 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 View Fig ). Femur, postfemur, and tibia of following legs each with adhesive pad ( Fig. 4C View Fig ). Penes ( Fig. 4D View Fig ) shorter than coxae of leg-pair 2, each with 0 or 1 microsetae apically.

Telson ( Fig. 4E, F View Fig ). 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 View Fig View Fig View Fig ). Both anterior and posterior gonopods projecting ventrad. Anterior gonopods ( Figs 5 View Fig , 6 View Fig ): each coxal process (cp) not expanded distally, distal part rounded ( Fig. 6C View Fig ), with several microsetae on posterior surface ( Fig. 5A View Fig ), posterior part curved mesad ( Fig. 5B View Fig ); 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 View Fig ). Posterior gonopods ( Fig. 7 View Fig ) 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 View Fig ). 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 View Fig ). Bursa with 3–5 setae around central funnel. Receptaculum seminis (rs) single, long, claviform ( Fig. 8C View Fig ).

Coloration. In life, yellowish brown with the defense glands visible by transparency as reddish spots ( Fig. 2 View Fig ). 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).

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).

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 View Fig ) 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 View Fig ) were 1.2%–1.7%. The results suggest gene flow between the Antrokoreana millipedes in the two western caves.