Eutrichodesmus digitatus, Liu, Weixin & Tian, Mingyi, 2013

Liu, Weixin & Tian, Mingyi, 2013, Four new cavernicolous species of the millipede genus Eutrichodesmus Silvestri, 1910 from southern China (Diplopoda: Polydesmida: Haplodesmidae), Zootaxa 3734 (2), pp. 281-291 : 281-284

Eutrichodesmus digitatus sp. n.

Figs 1–2

Material: Holotype male (SCAU), China, Guangdong Prov., Qingyuan City, Jintan Town, Mi Dong, 0 5.2011, leg. Tian Mingyi (CHIgd11-LWX01). Paratypes: 1 male, 2 females (SCAU), same locality, together with holotype.

Name: To emphasize the gonopod telopodite having a conspicuous, bifid, digitiform, distofemoral process at about midway.

Diagnosis: Differs from other congeners by metaterga 2-13 supporting four transverse mixostictic rows of tubercles, and the gonopod telopodite with a conspicuous, bifid, digitiform, distofemoral process (dp) at about midway while the acropodite has several differentiated lobes.

Description: Length of adults of both sexes ca 8.0- 8.5 mm, width 1.5-1.8 mm. Holotype ca 8.5 mm long and 1.8 mm wide. Coloration uniformly pallid ( Fig. 1 ).

Adults with 20 segments, body subcylindrical, conglobation complete, pattern of volvation typical, starting from segment 5. Head ( Fig. 1 A) slightly transverse (wider than high), rather densely pilose, microgranular and microvillose just below antennae and on vertex, with a pair of rounded, paramedian knobs; isthmus between antennal sockets about as wide as antennal socket diameter. Axial suture conspicuous. Antennae ( Fig. 1 A) rather short and clavate; antennomere 6 longer than 5th, both with an evident dorso-apical pit containing a tight group of minute bacilliform sensilla; antennomere 8 with usual four sensory cones apically. Collum subtrapeziform, rather large, broader than head, not covering the head from above; with six transverse rows of round setigerous tubercles ( Fig. 1 B). Prozona very finely alveolate, collum and metaterga covered with a cerotegument crust held by abundant microvilli; stricture between pro- and metazona broad and shallow, more finely alveolate-microgranular than prozona. Limbus microcrenulate, partly hidden by nearby abundant microvilli. Metaterga 2-13 with four transverse mixostictic rows of tubercles, following metaterga with more than four transverse rows of tubercles; three frontal rows highest and best expressed in anterior body part ( Figs 1 B, D, E); each tubercle crowned with an abraded seta. Paraterga with evident shoulders anteriorly, strongly declivous, broad and usually trilobate laterally, evidently extending down below level of venter; paraterga 2 strongly enlarged, with three lobulations anterolaterally, schism and hyposchism both very small; paraterga 3 and 4 slightly shorter than others, usually bilobate laterally; paraterga 6-14 laterally with three, following paraterga with four, distinct lobulations, somewhat caudolaterally at base with 1 or 2 distinct lobulations. Pore formula normal, ozopores very indistinct, located near top of caudolateral lobulation. Pleurosternal ridges present only in ♂ segments 2 and 3. Epiproct short, also with differentiated tubercles, directed ventrocaudad, with usual four cones below tip. Hypoproct and paraprocts normal ( Figs 1 C, D).

Sterna usually with a deep, narrow, transverse depression between coxae, but sterna between ♂ coxae 5-7 and 9 much wider. Gonopod aperture transverse-oval, far from reaching lateral sides of segment 7 ( Fig. 1 G). Legs rather long and slender, nearly reaching tips of paraterga; femur somewhat longer than tarsus; claw normal, simple, very slightly curved ventrad ( Fig. 1 F).

Gonopods ( Figs 1 H, 2A, B) relatively complex. Coxae large, microtuberculate and abundantly setose ventrolaterally. Telopodite a little longer than coxite, slender throughout, setose in its basal half, with a conspicuous, bifid, digitiform, distofemoral process (dp) at about midway. Acropodite with several differentiated lobes; seminal groove terminating subapically with a hairpad.

Remarks: This pallid species is a typical “doratodesmid”, possibly a troglobite which is somewhat unusual in showing differentiated metatergal tubercles, coupled with rather long and slender legs.

Figures

FIGURE 1. Eutrichodesmus digitatus sp. n., male paratype. A-B, E. anterior body part, ventral, dorsal and lateral views, respectively. C-D. posterior body part, ventral and dorsal views, respectively. F. cross-section of a midbody segment, frontal view. G. gonopod in situ, ventral view. H. gonopod, mesal view. Photographed not to scale.

FIGURE 2. Eutrichodesmus digitatus sp. n., male paratype. A-B. left gonopod mesal and lateral view. Scale bar: 0.2 mm.