Skleroprotopus securifer, Mikhaljova & Kazarin & Marusik, 2024

Mikhaljova, Elena V., Kazarin, Vitaly M. & Marusik, Yury M., 2024, The millipede genus Skleroprotopus Attems, 1901 (Diplopoda, Julida, Mongoliulidae) in China, with description of a new species, Zootaxa 5536 (3), pp. 483-491 : 486-488

Skleroprotopus securifer sp. nov. Mikhaljova

Figs 1–22

Material examined. Holotype: 1 male ( FSCB), China, Hebei Prov., Xiaowutai Mt. , 40.025˚N, 115.303˚E, 19.09.2005, leg. Y.M. Marusik ; Paratypes: 2 females, 8 juveniles ( FSCB), same data as for holotype .

Diagnosis. Differs from congeners mainly by the flattened, poleaxe-like outgrowth in the middle of the caudal surface of the anterior gonopod coxa in combination with very short and stout male coxites of the legpair 7.

Description. Male. Length in alcohol 44.0–45.0 mm, midbody vertical diameter 1.6–1.7 mm, with 60(–1) rings, excluding telson. Coloration (in alcohol) transversely striated from dark brown prozonites and beige metazonites. Anterior part of head light brown, vertex and occiput marbled dark brown. Eyes black, antennae brown. Collum with two transversely-oval, large, marbled light brown spots. Legs light brown. Telson light brown.

Head smooth, epicranial setae absent, 4 supralabral setae; 22 labral setae. Eye patches subtriangle, composed of at least 50 ommatidia. Antennae medium-sized, rather slender and clavate. A small group of sensilla basiconica at distodorsal surface of each of antennomeres 5, 6 and 7, sensilla basiconica gradually decrease to tiny ones on antennomere 7 ( Figs 1, 2 ). Mandibular stipites enlarged, ventrally incised, forming 2 nearly equal, subconical lobes. Gnathochilarium with lamellae linguales each of which with 6 setae arranged longitudinally. Promentum elongated longitudinally, expanded basally, swollen anteriorly. Collum laterally with distinct striae reaching to anterior margin.

Body slightly compressed laterally, this becoming increasingly pronounced towards telson. Prozona with dorsal shallow striae located diagonally to the body axis and lateral very shallow transverse striae. Metazona with regular, longitudinal striae reaching hind margin and disappearing above the ozopore level; setae on hind margins absent. Ozopores small, set far behind pro-metazonital suture. Epiproct broadly rounded and slightly protruding caudad, marginally with two setae. Preanal ring not pubescent, but with two marginal setae ventrally. Anal valves and subanal scale each with two marginal setae only.

Legs long and slender, without modifications; claws long, weakly curved, at base with a short (in pregonopodal legs) ( Fig. 5 ) and relatively short (in postgonopodal legs; about half the length of the claw) setiform accessory claw ventrally ( Figs 3, 7 ). Leg pair 1 enlarged, with 4-segmented telopodites, terminal segment with thin short setae distomesally ( Figs 4, 6 ), 3rd telopoditomere longest, dorsoventrally strongly flattened, with a front surface covered with short setae; telopoditomeres 1 and 2 with longer setae frontally, coxa with two long setae apically and three similar setae frontally. Penis elongated, with 4 subapical setae on the front surface ( Figs 5 , 9, 10 ). Coxae 2 each with one distal seta anteriorly and posteriorly ( Figs 5 , 13 ). Leg pair 7 with coxal processes as short knobs bearing setae both mesally and apically ( Fig. 8 ). Telopodites 7 variable even within same male holotype: telopodite on the left 3-segmented ( Figs 8, 11 ), but telopodite on the right 2-segmented ( Figs 8, 12 ).

Gonopods protruding. Anterior gonopod with 3-segmented telopodite (telopoditomere 3 (e, Fig. 18 ) tiny), bearing setae of different length apically and mesally on first telopoditomere, subapically on second telopoditomere and apically on third one ( Figs 16, 17, 18 ). Coxal process of the anterior gonopods long, with large, broad, flattened poleaxe-like outgrowth (b), rounded apex with protrusion, 2 basal setae (s) mesally and a longitudinal row of short setae (t) anterolaterally ( Figs 16, 17 , 21 ). Parabasal relatively long flagellum (f) with thin spines distally and nonbifurcated apex ( Figs 16, 17, 19 , 21 ). Posterior gonopod with long, slender anterior branch (a) pointed apically and posterior part (posterior branch) (p) bearing long setae in its inner surface and external edge, 1-segmented remnant of telopodite (r) at the base ( Figs 20, 21, 22 ).

Female. Length in alcohol 53.0–59.0 mm, midbody vertical diameter 2.4–2.5 mm, with 73(–1), 66(–1) rings, excluding telson. Ventral edge of the mandibular stipites with small knob medially. Leg pair 1 somewhat thicker and shorter, but leg pair 2 only somewhat shorter as compared the following legs. Vulva as in Figs 14, 15 .

Remarks. In some Skleroprotopus species (e.g. S. coreanus from the south of the Russian Far East), a large number of heterogeneous forms of males with various combinations of the main distinguishing characters were noted; these forms are young individuals belonging to different postembryonic stages of development ( Mikhaljova 2019). The male specimen of Skleroprotopus securifer sp. nov. described above is a fully-formed and mature adult male. The criteria for this interpretation are as follows: penis is conical bearing several setae apically; leg pair 1 is large, thick, with 4-segmented telopodites; leg pair 7 is modified, with 2–3-segmented telopodites and a short knobby setose coxal processes; anterior gonopods have 3-segmented setose telopodites (third lateral telopoditomere is tiny), flat coxal processes with large, broad, flattened poleaxe-like outgrowth, relatively long flagella, bearing small spinules apically; posterior gonopods with long, slender pointed anterior branches and posterior parts bearing long setae in them inner surfaces and external edges; posterior gonopods with remnants of telopodites at base.

As for the variation in the number of segments of the telopodite 7, similar variations were also noted in other species ( Murakami & Paik 1968; Mikhaljova & Korsόs 2003), thus, this feature is unreliable for distinguishing species.

Skleroprotopus securifer sp. nov. is similar to Skleroprotopus membranipedalis Zhang, 1985 in the general configuration of gonopods, but differs from it mainly by the short, knob-like coxal processes of the leg-pair 7 (vs. elongated in S. membranipedalis ), by the middle location of the poleaxe-like outgrowth (b) in the middle of the caudal surface of the anterior gonopod coxa (vs. subbasal in S. membranipedalis ), by the penis with 4 subapical setae on the front surface (vs. 2 apical setae laterally in S. membranipedalis ), by the darker coloration: dark brown prozonites and beige metazonites (vs. light brown-beige coloration, head whitish in S. membranipedalis ), as well as by the terrestrial habitat (vs. S. membranipedalis was collected in caves).

Etymology. The specific epithet refers to the axe-like posterior process of anterior gonopod.

Figures

FIGURES 1–7. Skleroprotopus securifer sp. nov., male holotype (FSCB). 1. Distal part of antenna. 2. Antenna apex. 3. Midbody leg. 4. Leg 1, anterior view. 5. Leg 2 and penis, posterior view. 6. Terminal segment of leg 1, anterior view. 7. Claw of mid-body leg. Scales: 10 μm (Fig. 7), 20 μm (Figs 2, 6), 100 μm (Figs 1, 3, 4, 5).

FIGURES 8–15. Skleroprotopus securifer sp. nov., male holotype and female paratype (FSCB). 8. Legpair 7, posterior view. 9. Penis apex, anterior view. 10. Penis, posterior view. 11. Telopodite of leg 7 on the left, posterior view. 12. Telopodite of leg 7 on the right, posterior view. 13. Distal part of coxa 2, anterior view. 14. Right vulva, lateral view. 15. Right vulva apex, lateral view. Scales: 10 μm (Figs 9, 11, 12), 20 μm (Fig. 10), 100 μm (Figs 8, 13); without scales: Figs 14 and 15.

FIGURES 16–19. Skleroprotopus securifer sp. nov., male holotype (FSCB). 16. Anterior gonopod, lateral view. 17. Anterior gonopod, mesal view. 18. Second and third telopoditemeres of anterior gonopod, lateral view. 19. Distal part of flagellum. Abbreviations: b, poleaxe-like outgrowth; e, third telopoditomere; f, flagellum; s, basal setae; t, short setae. Scales: 20 μm (Figs 18, 19), 100 μm (Figs 16, 17).

FIGURES 20–22. Skleroprotopus securifer sp. nov., male holotype (FSCB). 20. Posterior gonopod, mesal view, slightly turned back. 21. Posterior gonopod, plus tip of flagellum, lateral view. 22. Distal part of posterior gonopod, lateral view. Abbreviations: a, anterior branch; f, flagellum apex; p, posterior part; r, telopodite remnant. Scales: 20 μm (Fig. 22), 100 μm (Fig. 20), in mm (Fig. 21).