Eudigraphis nigricans ( Miyosi, 1947 ), 2020

Karasawa, Shigenori, Kawano, Keisuke, Fukaya, Shin-ichi & Tsurusaki, Nobuo, 2020, Upgrading of Three Subspecies of Eudigraphis takakuwai to the Species Rank (Diplopoda: Penicillata: Polyxenida: Polyxenidae), Species Diversity 25, pp. 89-102 : 98-99

Eudigraphis nigricans ( Miyosi, 1947) , stat. rev.

[Japanese name: Iso-fusayasude]

( Figs 1 , 4D , 5C, D , 6D–F )

Monographis takakuwai nigricans Miyosi, 1947: 7 (type locality: Enoshima isalnd, Kanagawa Prefecture, Honshu, Japan; type specimens collected by S. Gamo seem to be lost); Takashima and Haga 1950: 23, fig. 2; Takashima and Haga 1952: 18; Miyosi 1959: 58; Miyosi 1965: 741; Miyosi 1979: 478; Ishii 1983: 45; Takano 1973: 4.

Eudigraphis nigricans: Haga 1952: 15 ; Ishii and Tamura 1995: 233; Ishii 1997: 257; Ishii 1999: 212; Ishii 2002: 289.

Eudigraphis takakuwai nigricans: Ishii 1988: 957 , figs 10, 11; Matsumoto and Gamo 1992: 51, fig. 1A–D; Murakami 1993: 97; Nguyen Duy-Jacquemin and Geoffroy 2003: 99; Mimizu Club and Minagoshi 2013: 44, 3 photos; Minagoshi 2017: 50, 3 photos; Kawano 2017: 14, figs 1–12.

Diagnosis. Body 3–4.2 mm long excluding caudal bundle with no difference between sexes. Ground color of body pale yellowish brown in dorsal view, but head black. Body dorsally with a pair of belt-like dark brown markings that run slightly off from both of the rims of each segments of body. Mandible with 8 molar processes and 5 molar combs (for the details in mandible structure; see Ishii 1988). This species can be easily distinguished from E. takakuwai by having a somewhat smaller body with black head. Brown markings are darker and more conspicuous in this species than in E. takakuwai .

Brief description (based on specimens from Mizushiri Coast, Tottori City, Tottori Prefecture). Body length excluding caudal bundle (males): 3.6–4.2 mm (n =4, mean 3.8 mm).

Coloration. Head black. tergites yellowish brown laterally tinted with dark brown.

Head with an anterior row of 20 trichomes per side ( Fig. 6D ) and a posterior row of 12 trichomes per side ( Fig. 6D ).

Anntenal article VI with 3 thick basiconic sensilla (T) of equal length; article VII with 2 thick basiconic sensilla ( Fig. 6F ). The presence of conical and setiform sensilla were unable to be determined.

Clypeo-labrum with ca. 10 scattered setae along posterior margin; anterior margin of labrum granulated ( Figs. 6E ). Gnathochilarium with slender lateral palp with 12 cylindrical sensilla, medial palp with a group of ca. 10 sensilla.

Material examined. TOKYO METROPOLIS. Chiyoda Ward, Hibiya Park , under bark of a tree trunk of Aphananthe aspera (7 spms., 99% EtOH, 17 October 2017, SF) . —— TOTTORI PREFECTURE. Tottori City, Mizushiri Beach (35.524599, 134.098788), 3 m (3 adults and 6 juv., 99% EtOH, 18 October 2017, NT), same beach (35.525003, 134.099100), 1 m (3 males, 3 females and 12 juv., 27 May 2019, NT) . —— YAMAGUCHI PREFECTURE. Shimonoseki City: Chofusotoura-cho (6 spms., 99% EtOH, 25 September 2017, Makiko Matsuda); Toyoura-cho, Inunaki Cape (2 spms., 99% EtOH, 25 September 2017, Makiko Matsuda); Toyoura-cho, Uka (1 male, 1 September 2017, KK); Tsunoshima island , in the sand of sandy beach (4 spms., 99% EtOH, 9 May 2018, Makiko Matsuda) . —— FUKUOKA PREFECTURE. Kitakyushu City: Moji Ward, Tsunemi (2 spms., 99% EtOH, 24 September 2017, Makiko Matsuda); Wakamatsu Ward, Hibiki Marine Park (18 spms., 99% EtOH, 23 June 2017, SK) .

Distribution. Honshu, Kyushu, Hachijo-jima island ( Takashima and Haga 1952), Nii-jima island ( Takano 1973), and Okinawa Islands ( Minagoshi 2017; detailed locality unknown, though it was tentatively plotted on Okinawa-jima island in Fig. 1 ). Most records in Honshu came from southwestern part of Honshu, though the northernmost records extend to Sendai Bay, Miyagi Prefecture for the Pacific coast ( Matsumoto and Gamo 1992) and Sado-ga-shima island for the coasts of Sea of Japan ( Mimizu Club and Minagoshi 2013).

Habitat. This species is usually found in cracks of rocks on rocky sea cliffs, from shoreline to 1 to 2 m above from shoreline. Association of this species to rocky seashores is rather strong, though the species can be found sometimes on trunks of trees in the seaside forest ( Takashima and Haga 1952). One of us (SF) found a population of E . nigricans under barks of a trunk of tree Aphananthe aspera in Hibiya Park , ca. 1.8 km away from the nearest shore of the Tokyo Bay .

Ecology. This species is univoltine and overwinters as adults and juveniles. Eggs laid can be seen from June to October according to the observation of a population in Amatsu-Kominato, Chiba Prefecture ( Ishii 1997). The number of eggs per egg batch varies from 26 on average ( Ishii 1997) to ca. 30 ( Matsumoto and Gamo 1992). Each egg batch is covered by trichomes of tail brush of the female who laid the batch ( Matsumoto and Gamo 1992). Gut content of the species consisted of lichens on the rocks of seashore ( Ishii 1997).

Remarks. One of us (KK), found some live individuals floating on the surface of seawater due to surface tension generated by having many long bristles on their bodies off the coast of Uka, Shimonoseki City in Yamaguchi Prefecture ( Kawano 2017). This nature seems to facilitate dispersal of the species by raft and current of the sea.

Figures

Fig. 1. Distribution of three species of Eudigraphis with source of samples used for molecular phylogenetic analysis. Localities of samples are shown in brackets. Sample numbers correspond to those in Table 1 and Figs 2, 3. Literature and new records were also incorporated.

Fig. 4. Typical habitats (A, C, E, arrowed) of Japanese Eudigraphis (B, D, F). A, B: E. takakuwai: A, Toyama Park, Shinjuku Ward, trunk of Zelkova serrata (17 October 2017); B, various stages were found under bark of trunks of Z. serrata at the same site. C, D: E. nigricans; C, Mizushiri Beach, Tottori City (18 October 2017); D, an adult found in the cavity under a rock. E, F: E. kinutensis; E, campus of Tottori University, Tottori City, Z. serrata (13 November 2017); F, E. kinutensis under the bark of trunks of Z. serrata (Ochidani Park, Tottori City, 10 November 2017).

Fig. 5. Dorsal (A, C, E) and ventral (B, D, F) views of Eudigraphis. A, B: E. takakuwai, female (Waita, Toyoura-cho, Shimonoseki City, 31 August 2017). C, D: E. nigricans, male (Uka, Toyoura-cho, Shimonoseki City, 1 September 2017). E, F: E. kinutensis (campus of Tottori University, Tottori City, 5 January 2018). All the scales = 1mm.

Fig. 6. Scanning electron microscope images of Eugdigraphis spp. A–C: E. takakuwai, male (Suzaki, Seiyo City); A, labrum and left antenna; B, ventral view of distal segments of left antenna; C, dorsal view of right part of head with 3 trichobothria a, b, c. D–F: E. nigricans, male (Mizushiri Beach, Tottori City); D, head; E, ventral view of labrum with lateral palps (LP) of gnathochilaria; F, Distal segments of left antenna (ventral view). G, H: E. kinutensis, male (Tottori University Campus); G, labrum; H, dorsal view of right antenna and trichomes on head.