Trachyjulus bifidus, Likhitrakarn, Natdanai, Golovatch, Sergei I., Srisonchai, Ruttapon, Franck Brehier,, Lin, Aung, Sutcharit, Chirasak & Panha, Somsak, 2018

Likhitrakarn, Natdanai, Golovatch, Sergei I., Srisonchai, Ruttapon, Franck Brehier,, Lin, Aung, Sutcharit, Chirasak & Panha, Somsak, 2018, Two new species of the millipede family Cambalopsidae from Myanmar (Diplopoda, Spirostreptida), ZooKeys 760, pp. 55-71 : 55

Trachyjulus bifidus sp. n. Figs 5, 6, 7

Holotype

♂ (CUMZ), Myanmar, Tanintharyi Region, San Gu Cave (Elephant Cave), limestone, tower karst, 11°13'55"N, 99°10'32"E, 17.11.2015, leg. F. Bréhier.

Paratypes.

3 ♂, 1 ♀, 3 juv. (CUMZ), 1 ♂, 3 juv. (MNHN, MY15-01/01), same data as holotype. 6 ♂, 7 ♀, 4 juv. (MNHN, MY15-02/27), 2 ♂, 2 ♀ (ZMUM), same Region, Yae Gu Cave (River Cave), limestone, tower karst, 11°13'05"N, 99°10'32"E, 21.11.2015; 12 ♂, 10 ♀, 5 juv. (MNHN, MY15-07/13), same Region, Linno Gu n°1 Cave, guano, limestone, tower karst, 76 m a.s.l., 11°13'35"N, 99°10'32"E, 19.11.2015, all leg. F. Bréhier. 3 ♂, 2 ♀ (MNHN, MY15-09), same Region, Thin Bow Gu Cave (Linno Gu #2), limestone, tower karst, 11°11'23"N, 99°10'18"E, 03.06.2015, leg. C. Rahmadi.

Etymology.

To emphasize the strongly bifid telopodites of the anterior gonopods; adjective.

Diagnosis.

Differs from other Trachyjulus species based primarily on the following combination characters: the strongly elongated and bifid telopodites (te) of the anterior gonopods, coupled with the absence of flagella and the presence of deeply bipartite posterior gonopods, in which the telopodites (te) are much shorter than the massive, paramedian, coxal processes (cp).

Description.

Length of holotype ca. 19 mm; adult paratypes 13-30 (♂) or 12-25 mm (♀); midbody segments circular in cross-section (Fig. 5N), width of holotype 1.0 mm, of paratypes 0.8-1.0 (♂) or 0.8-1.1 mm (♀).

Coloration of adults in alcohol light grey-brown to dark castaneous brown, without a clear-cut pattern. Head, antennae and venter light yellowish to brownish. Ommatidia brown to blackish.

Adult body with 45p+4a+T (holotype); paratypes with 39 –70p+2– 4a +T (♂) or 40 –60p+2– 6a+T (♀). Eye patches transversely ovoid, with 3(4)+3(1) blackish, rather flat ommatidia in 1-2 longitudinal rows. Antennae short and clavate (Figs 5A, B, D, E, 7A), extending behind segment 5 laterally (Fig. 5A), antennomeres 5-7 each with a small apicodorsal group or corolla of bacilliform sensilla (Figs 5A, F, G, H, 7A), surface at base of antennomere 5 very finely scaly (Fig. 5F, I). Gnathochilarium (Figs 5E, 7B) oligotrichous, each lamella lingualis with 3-4 setae; mentum single.

In width, collum = midbody rings (close to 6th to 8th)> head = ring 2> 8-10> 7> 6> 5> 3 = 4; body abruptly tapering towards telson on a few posteriormost rings (Fig. 5R, S).

Collum (Fig. 5 A–C) smooth, only near lateral edge with 1-3 light, short, superficial striae (Fig. 5A). Postcollar metaterga clearly, but not particularly strongly carinate (Figs 5A, B, J, K, L, R, S), especially so from segment 5 on, whence porosteles commence, these becoming completely absent from legless segments where ozopores are missing (Fig. 5R). Porosteles large, but low, conical, round, directed caudolaterad, wider than high (Fig. 5Q). Carinotaxic formula of metaterga 2-4, 7/7+m/m+7/7 (Fig. 5 A–C). Carinotaxic formulae of following segments typically 10 –7/10– 7+I/i+2/2+m/m (Fig. 5A, B, C, J, K, L, R, S); all crests and tubercles, including porosteles, low.

Tegument smooth (Fig. 5A, B, J, K, L, R, S), dull throughout. Fine longitudinal striations in front of stricture between pro- and metazonae, remaining surface of prozonae very delicately shagreened (Fig. 5J, K, L, R). Metatergal setae absent. Segments 2 and 3 each with long pleural flaps.

Epiproct (Fig. 5 R–U) simple, bare, smooth, regularly rounded caudally. Paraprocts smooth, rather regularly convex and densely setose (Fig. 5U). Hypoproct transversely bean-shaped, slightly concave caudally (Fig. 5U).

Ventral flaps behind gonopod aperture on ♂ segment 7 evident swellings, forming a marked transverse ridge.

Legs nearly as long as body diameter (Fig. 5N), claw with an evident and long accessory claw near base (Fig. 5P), the latter up to ca. 2/3rds the length of claw itself (Fig. 5P).

♂ legs 1 highly characteristic (Figs 6A, B, 7C) in being very strongly reduced, with large 1-segmented telopodites and a pair of large, hook-shaped, medially contiguous, sternal processes with groups of long and strong setae at base on caudal face.

♂ legs 2 slightly reduced, but coxa and femur hypertrophied (Figs 6C, 7D); penes rather small, oblong-subtrapeziform, each with 1-2 strong setae distolaterally (Figs 6C, D, 7D).

♂ legs 3 slightly reduced, modified in having coxae especially slender and elongate (Figs 6E, 7E).

Anterior gonopods (Figs 6 F–H, 7G, H)) peculiar in stout telopodites (te) being two curved, widely separated fingers with a setose central field on anterior face (Figs 6F, H, 7H). Anterior coxosternal process (acp) lobe-shaped, caudally about as high as a stout posterior coxosternal process (pcp).

Posterior gonopods (Figs 6 I–K, 7F) elongate and finger-shaped, membranous, evidently bipartite, round, with both coxal processes (cp) and telopodites (te) sparsely microspiculate at margin (Fig. 6K); te membranous, slightly curved mesad, clearly shorter than cp, with a parabasal field of coniform microsetae caudally (Figs 6J, 7H).

Remarks.

The genus Trachyjulus Peters, 1864 is currently known to comprise 31 species ranging from Nepal, India, and Sri Lanka in the west, through Bangladesh and Myanmar to Vietnam, Thailand, Malay Peninsula, Singapore, and Indonesia (Sumatra and Java) in the east ( Golovatch et al. 2012). Only one species, the pantropical anthropochore T. calvus , has hitherto been documented from Myanmar ( Likhitrakarn et al. 2017). This species (cf. Golovatch et al. 2012) is similar to T. bifidus sp. n., but the latter is clearly distinguished by the bifid telopodites of the anterior and posterior gonopods.

Based on the pigmented body and eye patches, and like most if not all other cave-dwelling congeners known to date, T. bifidus sp. n. seems to be hardly more than a troglophile.

No special key to relevant genera involved seems to be needed, as the one given below to Myanmar species contains the necessary information.