Spirobolus akamma, Kato & Takano & Nakano & Shimano, 2023

Kato, Taiga, Takano, Mitsuo, Nakano, Takafumi & Shimano, Satoshi, 2023, Taxonomic Assessment of a Threatened Large Millipede Endemic to the Southern Ryukyu Islands, Japan: a New Species of Spirobolus (Diplopoda: Spirobolida: Spirobolidae) from the Yaeyama Islands, Species Diversity 28 (1), pp. 23-30 : 24-29

publication ID	https://doi.org/ 10.12782/specdiv.28.23
persistent identifier	https://treatment.plazi.org/id/03F28795-FFAF-3D21-13F2-EB11FDE9B2A2
treatment provided by	Felipe
scientific name	Spirobolus akamma
status	sp. nov.

Treatment

Genus Spirobolus Brandt, 1833 View in CoL View at ENA Spirobolus akamma sp. nov. [Japanese name: Yaeyama-maruyasude] ( Figs 1–8 View Fig View Fig View Fig View Fig View Fig View Fig View Fig View Fig )

Polyconoceras sp. : Omine 1962: 1, 6 (list; as Polyconoxcerus [sic] sp.); Omine 1965a: 48, fig. 7 (as Polyconoceros [sic] sp.).

Polyconoceras callosus (Karsch, 1881) : Omine 1965b: table 1 (list; as Polyconcerus [sic] callosuesp [sic]).

Spirobolus joannisi Brölemann, 1896 : Ikehara et al. 1974: table 1 (list; as Spirobolus joannisu [sic]).

Prospirobolus joannise [sic]: Ikehara and Shimojana 1975: 125, one text-fig.; Kikunaga et al. 1993: 91 (list); Yokotsuka 2002: 242, one text-fig.; Yokotsuka 2004: 242, one text-fig.; Yokotsuka 2011: 242, one text-fig.

Acladocricus sp. : Omine et al. 1982: 119, 121, photo 5.

Spirobolus sp. : Takano 1989: 4, fig. 1; Murakami 1993: 98 (list); Tanabe 2001: frontispiece 5; Omine 2002: 157, 161, table 5; Chigira and Tanaka 2004: 16 (list), photo 18; Tanabe in NCD Okinawa 2005: 306; Takano in Ministry of the Environment 2010: 5; Nakamura and Korsós 2010: 79, 81 (list); Takano in Ministry of the Environment 2014: frontispiece 2, 56; Shinohara et al. 2015: 981, one photo; Nakamura in NCD Okinawa 2017: 36, one photo, 419; Horii 2020: 122, one text-fig.

Diagnosis. The new species is characterized by the following combination of characteristics: coxa of anterior gonopods long and subtriangular; mesal sternal process of anterior gonopods pentagonal; prefemoral endite of posteri- or gonopods coronoid, distal end rounded, with mesal margin lacking notch; telopodite of posterior gonopods more than 2× longer than prefemoral endite; lateral flange of cyphopods with 4 serrations.

Material examined. Holotype. KUZ Z4329 View Materials ( Fig. 1B–D View Fig ), male, Mt. Omotodake (24.41671°N, 124.19145°E), Ishigaki Island , Yaeyama Islands, Ryukyu Islands, Japan, 13 October 2020, col. Naoto Sawada ( NS). GoogleMaps

Paratypes. Four specimens from Ishigaki Island: KUZ Z4328 View Materials , male, near the type locality (24.41608°N, 124.19150°E), 3 June 2019, col GoogleMaps . Yuta Fujimori ; KUZ Z4331 View Materials – Z4333 View Materials , three females, same data as for holotype GoogleMaps . Six specimens from Iriomote Island, Yaeyama Islands, Japan: KUZ Z4330 View Materials , female, Mt . Tedo (24.37084°N, 123.82051°E), 21 October 2020, col . Minoru Anzai ; KUZ Z4334 View Materials , Z4335 View Materials , Z4338 View Materials , three males, and KUZ Z4336 View Materials , female, near Mariudo Waterfall (24.36030°N, 123.80045°E), 21 April 2022, col GoogleMaps . NS; KUZ Z4337 View Materials , female, near Yutsun Waterfall (24.36721°N, 123.88435°E), 20 April 2022, col GoogleMaps . NS.

Description. Adult males: 63.1–74.7 mm long, vertical diameter of largest body ring 5.9–6.3 mm; body with 55–57 podous rings + telson. Adult females: 75.5–92.2 mm long, vertical diameter of largest body ring 6.48–7.52 mm; body with 55–59 podous rings + telson.

Head. Head capsule ( Fig. 2A View Fig ) smooth, area below antennal sockets with wrinkles. Occipital furrow reaching level of lower edge of antennal sockets. Incisura lateralis open. Labrum with 2 or 3 teeth, 5–8 supralabral setae, and 16–28 labral setae. Eye diameter ~0.75× greater than interocular space; with 7 or 8 vertical rows of ommatidia, 5 or 6 horizontal rows, and with 31–39 ommatidia per eye forming suboval cluster. Antennae ( Fig. 2D, E View Fig ) short, reaching to posterior margin of collum, when stretched back accommodated in shallow furrow composed of horizontal segment in head capsule and vertical segment in mandibular cardo and stipes. Antennomere lengths II> I> III> V> VI> IV> VII; antennomere I and II glabrous, III with some ventral setae, IV sparsely setose, V, VI and VII densely setose, and V and VI with sensilla basiconica bacilliformia latero-apically ( Fig. 3A, B View Fig ); with 4 apical sensilla. Mandibular stipes broad at base, apically gradually narrowed; subanterior margin of stipes mucronate. Gnathal lobe ( Fig. 2B View Fig ) external tooth with 2 large and prominent cusps; inner tooth with 4 cusps; lateral tooth thin; 8 pectinate lamellae; molar plate with 15 transverse furrows. Gnathochilarium ( Fig. 2C View Fig ) typically spirobolidan; each stipes with 3 apical setae; each lamella lingualis with 2 setae, one behind the other; basal part of mentum transversely wrinkled; basal part of stipes longitudinally wrinkled.

Collum. Surface smooth, with marginal furrow along lateral part of anterior margin; lateral lobes narrowly rounded, not extending as far ventrad as ventral margin of body ring 2 ( Fig. 4A View Fig ).

Body rings. Surface very smooth, parallel-sided in dorsal view ( Fig. 1B, C View Fig ). Prozona smooth. ‘Tergo-pleural’ suture visible on pro- and mesozona; mesozona ventrally with fine oblique striae, dorsally punctate; metazoa ventrally with fine longitudinal striae. ‘Pleural’ parts of rings with fine oblique striae. Sterna transversely striate. Pleurotergal tips of body ring 2 ( Fig. 4B View Fig ) gaping ventrally, not connected to sternite; inner outline of pleurotergal tips of female body ring 2 viewed anteriorly nearly straight (upper part slightly convex, lower part concave slightly), with apex of pleural flange subpointed; pleurotergal tips of male body ring 7 fused ventrally. Ozopores present from body ring 6, situated in mesozona, ~1/4 pore diameter in front of metazoa ( Fig. 4A View Fig ).

Telson. Entirely smooth; preanal ring tapering, not exceeding anal valves ( Fig. 4C View Fig ). Anal valves impressed submarginally; margins slightly protruding, liplike. Subanal scale broadly triangular ( Fig. 4D View Fig ).

Legs. Midbody leg length 76% of body diameter in holotype male (leg-pair 15), 76% of body diameter in paratype female (KUZ Z4332: leg-pair 15). Prefemur basally constricted, femur longer than other podomeres ( Fig. 4H View Fig ). Postgenital legs unmodified, with few ventral setae (e.g., 0-1, 0, 0-1, 0, 0-1, 1-2; leg-pairs 10, 15 and 20). Adhesive pads absent. Claw slender, ~1/3× longer than tarsus. First and second legs ( Fig. 4E, F View Fig ) modified, coxae fused to sternites and greatly elongated. Coxae of male legs 3–7 with short rounded processes ( Fig. 4G View Fig ).

Anterior gonopods. Mesal sternal process (mp) pentagonal, not reaching as far as coxal tip ( Fig. 5A, B View Fig ). Coxa (co) long, subtriangular, apically gradually narrowed, rounded, with pronounced projection beyond sternal process ( Fig. 5A, B View Fig ). Telopodite (tea) apically far overreaching coxa ( Fig. 5C, D View Fig ); apex of telopodite hooklike, bending laterally ( Fig. View Fig

5A–D).

Posterior gonopods. Telopodite (tep) slender, more than 2× longer than prefemoral endite (pe) ( Fig. 6A–D View Fig ); inner side of apex slightly concave, with or without tiny serrations ( Figs 6B View Fig , 7 View Fig ); outer side of apex slightly swollen; outer margin of telopodite with longitudinal groove ( Fig. 6D View Fig ); prefemoral endite coronoid, with rounded distal end ( Fig. 6D View Fig ).

Cyphopods. Cyphopods broad distally ( Fig. 8A, C View Fig ); distallobe cephalic face without longitudinal groove ( Fig. 8A View Fig ). Lateral flange (lf) narrow, with 4 serrations; 1st serration as large as 2nd at midpoint of flange; 4th serration at proximal end of flange smallest ( Fig. 8C View Fig ). Valves (av and pv) prominent, of equal size ( Fig. 8B View Fig ).

Coloration. In life, both anterior and posterior margins of collum and dorsoposterior margin of body rings 2 to preanal ring reddish, with remainder of body rings blackish ( Fig. 1A View Fig ). Reddish color faded in ethanol.

Etymology. The specific name akamma is derived from the Yaeyama folk tale “ ẁDz ” (Akamma means “red horse” and is the name of the horse beloved by the protagonist), and thus is treated as indeclinable.

DNA sequences and genetic distances. In total, seven sequences were obtained: paratype male ( KUZ Z4328 View Materials ) from Ishigaki Island , three sequences, 28S (531 bp; INSD accession number LC727543), COI (658 bp; LC727547 ) and 16S (431 bp; LC727545 ); paratype female ( KUZ Z4332 View Materials ) from Ishigaki, one sequence, COI (658 bp; LC727549 ); and paratype female ( KUZ Z4330 View Materials ) from Iriomote Island, three sequences, 28S (531 bp; LC727544 ), COI (658 bp; LC727548 ) and 16S (431 bp; LC727546 ) .

The paratype male 28S sequence from Ishigaki and paratype female 28S sequence from Iriomote were identical; their 16S sequences revealed 4/431 (0.9%) base pairs to be polymorphic.

The COI uncorrected p -distance between S. akamma sp. nov. and S. bungii was 12.8–13.4%, with the distance between S. akamma sp. nov. and Spirobolus sp. 11.7–12.7%. The COI divergence between S. bungii and Spirobolus sp. was 4.1%. Additionally, the COI genetic distance of our S. akamma sp. nov. specimens was 0.2–0.9%. The low genetic divergence corroborates the taxonomic conclusion that Spirobolus populations on Ishigaki and Iriomote islands are conspecific.

Distribution and habitat. Spirobolus akamma sp. nov. occurs on Ishigaki and Iriomote islands in Yaeyama Islands; this species has been also recorded from Kohama Island, a small islet located between Ishigaki and Iriomote islands ( Chigira and Tanaka 2004). This species has been reported from terrestrial and arboreal habitats ( Ikehara and Shimojana 1975; Yokotsuka 2002; Shinohara et al. 2015), and most of our specimens were also collected from arboreal habitats.

Remarks. The new species clearly belongs to the genus Spirobolus because it possesses the following diagnostic generic characteristics ( Keeton 1960; Hsu 2008): boat-shaped posterior gonopods; a short prefemoral endite of the posterior gonopods, being neither subrectangular nor as long as the telopodite of the posterior gonopods; and with thick cyphopods, with teeth on the lateral flange. A BLAST search ( Altschul et al. 1990) of partial COI sequences of S. akamma sp. nov. (LC727547–LC727549) based on BLASTN 2.13.0+ ( Zhang et al. 2000) at the NCBI website (https://blast.ncbi.nlm.nih.gov/) revealed them to be mostly identical (87.1–87.7%; with 98% query coverage) to the sequence from the complete mitogenome of S. bungii (NC_056899 = MT767838). BLAST results preliminarily corroborated our conclusion that S. akamma sp. nov. is a member of Spirobolus .

Spirobolus akamma sp. nov. may be most morphologically similar to S. “lienhuachihus”, from Lienhuachih, central Taiwan, but it differs in possessing a pentagonal mesal sternal process of the anterior gonopods, and a lateral flange on the cyphopods with 4 serrations [S. “lienhuachihus” has a concave mesal sternal process of the anterior gonopods, and cyphopods with a lateral flange with 5–7 serrations ( Hsu 2008)].

Although the new species shares most characteristics of the posterior gonopods with S. grahami Keeton, 1960 , which is endemic to Sichuan and Guizhou in southwest China, the former is distinguishable from the latter by having the telopodite of the posterior gonopods more than 2× longer than the prefemoral endite of the posterior gonopods [in S. grahami , the telopodite is less than 2× the length of the prefemoral endite ( Keeton 1960)]. While S. akamma sp. nov. and S. walkeri Pocock, 1895 share general features of the cyphopods, the new species differs from it in the number of serrations of lateral flange of cyphopods (4 in S. akamma sp. nov. vs. 3 in S. walkeri ; Keeton 1960). The distribution of S. f. “semiflavus” includes the northeastern part of Taiwan, and is thus most geographically close to S. akamma sp. nov. ( Hsu 2008). However, S. f. “semiflavus” is unequivocally distinguishable from S. akamma sp. nov. by gonopodal and cyphopodal features.

The morphological features of S. akamma sp. nov. coincide with the Takano’s (1989) description of Spirobolus sp. from Yaeyama Islands. In anterior gonopod morphology, S. akamma sp. nov. is also similar to “ Polyconoceras sp. ” from the Yaeyama Islands as described by Omine (1965a). We posit that these previously reported “Yaeyama-maruyasude” are conspecific with S. akamma sp. nov.