Plusioglyphiulus pallidior, Golovatch & Geoffroy & Mauriès & Den Spiegel, 2009

Golovatch, Sergei I., Geoffroy, Jean-Jacques, Mauriès, Jean-Paul & Den Spiegel, Didier Van, 2009, Review of the millipede genusPlusioglyphiulusSilvestri, 1923, with descriptions of new species from southeast Asia (Diplopoda, Spirostreptida, Cambalopsidae), Zoosystema 31 (1), pp. 71-116 : 98-101

Plusioglyphiulus pallidior n. sp.

( Figs 24-26)

TYPE MATERIAL. — Indonesia. Borneo, Kalimantan Timur, Kutai Timur, Sangkulirang , Baai , 01.332°N, 117.397°E, Cave Gua Ambulabung , by hand, 14.VIII.2004, leg. A. Bedos & L. Deharveng (KAL-068), holotype ♂ ( MZB) ; 2 subadult ♂♂ paratypes ( MZB); 1 ♂, 1 ♀ paratypes ( MNHN GA061). — Same cave, 15.VIII.2004, leg. A. Bedos & L. Deharveng (KAL-071), 1 ♂ paratype ( ZMUM). — Deep part of the same cave, by hand, 16.VIII.2004, leg. A. Bedos & L. Deharveng (KAL-110), 1 subadult ♀ paratype ( MNHN GA061); 1 juvenile ♀ paratype ( SEM).

ETYMOLOGY. — To emphasize the lighter general coloration compared to the sympatric and even syntopic P. bedosae n. sp.

DIAGNOSIS. — Differs from congeners by certain details of gonopod structure (unusually enlarged anterior gonopods versus rather slender posterior ones), coupled with the mixostichic carinotaxy of the collum and of other body segments, the presence of a marked depression on the collum and of only two rows of bituberculate crests below the poriferous cones on most of the body segments, the flattened paraprocts, the short and broadly rounded epiproct and the absence of spots dorsad of the ocellaria.

DESCRIPTION

Length of adults 43-50 mm, width 2.0- 2.1 mm, segments of posterior third of body being broadest. Coloration uniformly light yellow-brown; head (except for blackish ocelli), collum and segments 2-7 entirely yellow.

Body of adults with 64-70p+2-1a+T. Length of holotype about 50 mm, width 2.1 mm (width of collum, 2.0 mm) with 70p+2a+T.

Clypeus with 3 (n = 2) or 5 teeth (n = 1) anteromedially. Antennae short and clavate ( Fig. 26A), antennomeres 6 and 7 each with a very considerable group of bacilliform sensilla distodorsally. Ocellaria transversely subtriangular, with 8-11 ocelli in 5-7 longitudinal rows. Gnathochilarium oligotrichous ( Fig. 26B).

Postcollar constriction very evident, collum and segment 2 particularly strongly enlarged ( Fig. 24A). Carinotaxy formula of collum variable: ta/t+2p/ t+3p/t/t/t+///(t)+4p/t/t/t +5p/t/t/t+pp/t/t/t+//ma/t or //t+2p/t/t+3p/t/t+4p/t/t/t+//(ta)/(t)+5p/t/t/t+pp/t/t/ t+ma/t ( Fig. 24A). Collum strongly depressed near anterior third ( Fig. 24A). Carinotaxy of metatergum 2, 6/6+m/m+6/6; formula of metaterga 3 and 4, 3/3+3+M+3+3/3; formula of metaterga 5-7 and of several segments before apodous, 2/2+I/i+3/3+m/ m+3/3+I/i+2/2; formula of midbody metaterga, 2/2+I/i+3/4/3+m//m+3/4/3+I/i+2/ 2 in adults,2/2+I/ i+3/3+m/m+3/4/3+I/i+2/ 2 in subadults; formula of apodous segments, 4+0+4 ( Figs 24; 25A); all crests and tubercles rather high, poriferous cones (I) considerably higher, about as high as broad, while median ones (m) slightly lower than others ( Fig. 24B). All tergal tubercles microgranular ( Fig. 25C). Dorsal crests on several posteriormost segments considerably higher than others ( Fig. 25A). Midbody segments circular in cross-section ( Fig. 24B). Pleural regions of segments 2-4 conspicuously expanded, flap-shaped, especially so on segment 3 ( Fig. 24A). Pleural ridge behind gonopod aperture on male segment 7, tegument and limbus as in above congeners. Epiproct short, regularly and broadly rounded apically, with a paramedian pair of high but short crests/tubercles sometimes flanked on each side by 1 or 2 small knobs at about midway; paraprocts fl attened; hypoproct emarginate at caudal margin ( Fig. 25A, B).

Legs relatively long, on midbody segments about ¾ as long as body diameter ( Fig. 24B). Claw at base with a very short accessory spine ( Fig. 25D). Tarsi and their distal setae as in other congeners. Male legs 1-3 ( Fig. 26 C-E) more or less as in P. grandicollis , but male coxa 1 relatively short, while male telopodite 3 not so compact.

Anterior gonopods ( Fig. 26F) generally like in P. ampullifer n. sp., but coxites swollen and stout, non-contiguous medially; processes cxp1 very short, beak-shaped, finely ribbed apically; processes cxp2 high, hyaline, subspatuliform, setose at base on frontal face; telopodites (te) simple, lateral in position, movable, rather stout, subcylindrical with tip curved mesad, setose at about midway in distal half laterally. Posterior gonopods ( Fig.26G)small, relatively simple, without traces of telopodites; each coxite with a long, spiniform arm (d) laterally and a shelf-like structure at about midway on frontal face; distal half lamellose, fringed and with a deep fovea apically.

Subadults about 26 mm long, 1.3 mm wide, pallid, with 53-55p+4a+T and 3-5 blackish ocelli in 2-4 longitudinal rows. Male legs 1 similar to adult condition, but central sternal hook nearly straight, non-unciform. Male legs 2 and 3 slightly less strongly modified than in adults.

REMARKS

The most striking observation obtained from the above material is that an additional, middle row of intercalary tubercles on the metaterga (like in Fig. 27C, D) seems to appear only at the onset of adulthood.

Any obvious troglomorphic traits in this species seem to be absent. The size differences between P.bedosae n. sp. and P. pallidior n. sp. are so extreme that niche segregation is strongly suggested, such is the case in some other soil- or cave-dwelling millipedes ( Enghoff 1992; Enghoff et al. 1997). This is so far the only locality known that supports two species of Plusioglyphiulus . That we deal with two different species is beyond any doubt. Even the subadults of P. pallidior n. sp. are considerably larger than the adults of P. bedosae n. sp. In addition, they differ in gonopod structure so drastically that one ( P. pallidior n. sp.) could hardly be seen as an ontogenetic derivative of the other ( P. bedosae n. sp.).