Pacidesmus martensi, Golovatch, Sergei I. & Geoffroy, Jean-Jacques, 2006

Golovatch, Sergei I. & Geoffroy, Jean-Jacques, 2006, Golovatch, with the description of a new troglobitic species from southern China (Diplopoda: Polydesmida: Polydesmidae), Zootaxa 1325, pp. 363-368 : 364-367

Pacidesmus martensi sp. n.

Figs 1–12

Material examined. ɗ holotype ( MNHN JC 306), China, Guizhou Prov., Qianxi County, Hong Lin Town, Ishui Luo Dong Cave (= Waterfall Cave), 16.XI.2003, leg. L. Latella. — Paratypes: 2 ɗ, 4 Ψ, 1 juv. ( MNHN JC 306), 1 ɗ, 1 Ψ ( ZMUM), 1 ɗ, 1 Ψ (BDBFUL), 1 ɗ, 1 Ψ ( ZMUC), Guizhou Prov., Dafang County, Yangzhamba Village, Hei Dong Cave (terrestrial), II.2004, leg. S. Prevorčnik & B. Sket.

Etymology. We take pleasure in dedicating this species to Prof. Dr Jochen Martens (Mainz University), a devoted student and collector of soil arthropods, birds and other animals in various parts of the world, including China.

Diagnosis. Differs from congeners by the strongly elevated paraterga with narrowly rounded caudal corners, the poorly developed accessory seminal chamber, and the shape of the gonopod acropodite (see Key below).

Description. Length of holotype about 21 mm, width of midbody pro­ and metazona 1.3 and 2.1 mm, respectively. Paratypes 17–22 mm, width of midbody pro­ and metazona 1.3–1.8 and 2.1–2.8 mm; ɗ usually slightly smaller than Ψ. Coloration entirely pallid, whitish, with pinkish tint in places.

Head usual, densely setose; genae roundly subquadrate; epicranial groove evident but shallow. Antennae ( Figs 1–2 , 9 ) long and slender, weakly clavate; antennomeres 5 and 6 each with a distodorsal field of minute bacilliform sensilla; antennomere 7 dorsally with a small, but evident, claviform, transparent tubercle at base and a flat tubercle in distal quarter.

Body polydesmoid, with 20 segments. Collum subequal in width to head and segments 2 and 3, with three indistinct transverse rows of very flat setigerous bosses; setae of front row slightly longer than others; paraterga broadly rounded, slightly elevated up to level of dorsum, devoid of evident indentations. Body parallel­sided on segments 7–17, thereafter abruptly tapering caudally. Paraterga of segment 2 elevated, not surpassing rear tergal contour. Subsequent paraterga slightly projecting caudad beyond rear tergal contour, evidently elevated above dorsum until about segment 10, onward about level to dorsum until segment 19, evidently below level of dorsum only on segment 19 ( Figs 1–7 ). Caudal corners of all paraterga more or less narrowly rounded, never pointed. Tergal surface smooth, with three transverse setigerous rows of very flat bosses, forming a typical pattern ( Fig. 5 ); setae minute, very short. Prozona very finely shagreened, metazona below paraterga microgranulate. Structure between pro­ and metazona nearly smooth, only sides with extremely faint transverse striolation. Limbus microdenticulate. Pore­bearing paraterga with four, poreless paraterga with three, minute lateral incisions. Pore formula normal, ozopores lying entirely dorsally, at bottom of a lanceolate groove near lateral margin between two caudolateral incisions ( Figs 3, 5 ). Epiproct coniform ( Figs 6–7 ), barely surpassing paraprocts caudally. Hypoproct distinctly trapeziform, with a pair of long setae at caudolateral corners.

A distinct pleurosternal flap­shaped crest present only on segment 2 ( Fig. 2 ), thereafter totally wanting. Sterna evidently setose, but without modifications. Gonopod aperture obcordate, with a small, rounded shelf caudomedially.

Legs very long and slender ( Figs 2, 4, 7 , 10 ), especially so towards caudal body end, nearly twice as long as body height; telopodite devoid of sphaerotrichomes; claw very long and slender, distinctly curved ( Fig. 10 ).

Gonopods ( Figs 8 , 11–12 ) with typical, enlarged, subtriangular, medially fully coalesced coxae, each coxa bearing 2–3 macrosetae ventrally and a cannula dorsomedially. Telopodite elongate, relatively simple; acropodite (= branch lying distally of recurvature point of seminal groove, cf. Golovatch 1991; Djursvoll et al. 2001) split into two unequal parts: a longer, slender, distally curved endomere (a) and a shorter, lobuliform exomere (l). Endomere with a small denticle (d) frontally at base. Region near pulvillus, and that lying distolaterally of recurvature point of seminal groove, conspicuously papillate­spinulate, often with another small but clear denticle distally on mesal face. Accessory seminal chamber very small, inconspicuous. Orifice on pulvillus surrounded by spinules.

Epigynal ridge low, slightly elevated and rounded only laterally. Vulvae usual, elongate, densely setose, with spiral canals at bottom of gutter.

Remarks. Because this remarkable species shows several evident traits of troglomorphism, such as the completely unpigmented tegument and the elongate appendages, it can be considered as troglobitic with a fair degree of certainty. The cave Ishui Luo Dong supports two further diplopods, both presumably troglobitic and highly local: Guizhousoma latellai Mauriès, 2005 ( Chordeumatida , Guizhousomatidae ) ( Mauriès 2005) and a Glyphiulus species from the granulatus ­group ( Spirostreptida , Cambalopsidae ) (Golovatch et al., in press). On the other hand, the cave Hei Dong harbours a tiny species of Doratodesmidae (Polydesmida) , most probably troglobitic as well. The distance between the two caves being only about 20 air­km, both lying within the same karst massif situated between Dafang and Qianxi, it is hardly surprising that they contain the same species of Pacidesmus . In addition, Guizhousoma latellai has hitherto been encountered in as many as four of the massif’s caves ( Mauriès 2005).

The discovery of P. martensi sp. n. in Guizhou — a species very closely related to and sympatric with P. sinensis , despite the latter’s poor original description ( Loksa 1960)— leaves no doubt whatever that they are congeneric. Therefore, the doubts expressed by Golovatch (1991) concerning the allocation of P. sinensis no longer apply.

Figures

FIGURES 1 – 8. Pacidesmus martensi sp. n., ɗ holotype. 1 – 2 Anterior body part, dorsal and lateral views, respectively; 3 – 4 Midbody segments (3 dorsal, 4 lateral view); 5 Segment 8, dorsal view; 6 – 7 Caudal body part (6 dorsal, 7 lateral view); 8 Right gonopod, lateral view. Scale bars 1.0 mm (Fig. 8 not to scale).

FIGURES 9 – 12. Pacidesmus martensi sp. n., ɗ holotype. 9 Antenna; 10 Leg 9; 11 – 12 Left gonopod (11 mesal, 12 lateral). Scale bar 0.3 mm.