Plusioglyphiulus hoffmani, 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 : 106-110

Plusioglyphiulus hoffmani n. sp.

( Figs 31-33)

TYPE MATERIAL. — Malaysia. Borneo, Sarawak, Gunung Mulu National Park, 4.05°N, 114.93°E, Deer Water Cave ( Luang Sungai Payau ), halfway, in guano, 25.IV.1978, leg. P. J. Chapman, holotype ♂ ( VMNH) ; 3 ♂♂, 5 ♀♀, 1 subadult ♂, 1 subadult ♀ paratypes ( VMNH); 1 ♂, 1 ♀ paratypes ( MNHN GA063); 1 ♂, 1 ♀ paratypes ( ZMUM); 1 ♀ paratype ( ZMUC); 1 ♀ paratype ( SEM).

ETYMOLOGY. —To honour Richard L.Hoffman ( VMNH), a prominent specialist in the systematics of Diplopoda, who provided several samples for this study.

DIAGNOSIS. — Differs from the most similar P.macfarlanei Mauriès, 1983 in minor details of gonopod structure (cxp1 of the anterior gonopod is not extended into a flat lobe, te of the same gonopod is recurved and unciform, the apex of the posterior gonopod is less elaborate), the short epiproct, the regularly convex paraprocts and the absence of complete crests on the collum.

DESCRIPTION

Length 19-30 mm, width 1.0- 1.6 mm, collum and segments of posterior third of body being equally broadest. Coloration uniformly light yellow-brown to light brown, sometimes with infuscated sides and tips of poriferous tubercles; head (except for brown-blackish ocelli and a paramedian pair of separated, light brown spots dorsad of ocellaria), collum and segment 2 mostly pale yellow; antennae and legs light brown.

Body with 45-53p+3-1a+T. Length of holotype about 24 mm, width 1.5 mm, with 52p+2a+T.

Antennae short and clavate ( Figs 31A; 33A), antennomeres 6 and 7 each with a considerable group of bacilliform sensilla distodorsally; similar but minute sensilla present also on antennomere 7 ( Fig. 32C). Ocellaria transversely subtriangular, with 5-9 ocelli in 4-6 longitudinal rows. Gnathochilarium oligotrichous.

Postcollar constriction very evident, collum and segment 2 particularly strongly enlarged ( Fig. 31A, B). Carinotaxy formula of collum: ta/t+2p/t+3p/ t+//ta/t+/(ta)/(t)/(t)+5p/t/t +5p/t/t+//ta/t+ pp/t/t/ t+//ma/t ( Fig. 31A, B). Carinotaxy of metatergum 2, 8/8+m/m+8/8; formula of metaterga 3 and 4, 3/3+4+M+4+3/3; formula of metaterga 5 and 6, and of several segments before apodous, 3/3+I/i+3/3+m/ m+3/3+I/i+3/3; formula of midbody metaterga, 3/3+I/i+3/4/3+m//m+3/4/3+I/i+3/3; that of apodous segments, 5+(m)+5 ( Figs 31; 32B); all crests and tubercles rather low, poriferous cones (I) considerably higher, but still broader than high, while median ones (m) as high as others ( Figs 31C, D; 32B).Dorsal crests on several posteriormost segments considerably higher than others ( Fig. 31E). Midbody segments circular in cross-section ( Fig. 32B). Pleural regions of segments 2-4 conspicuously expanded, flap-shaped, especially so on segment 3 ( Fig. 31A). An unusually high, transverse pleural ridge behind gonopod aperture on male segment 7, with very short rounded flaps bent caudad at apex. Tegument and limbus typical. Epiproct very short, subtrapeziform, broadly rounded apically, with a paramedian pair of well-separated, high but short crests/tubercles at about midway; paraprocts regularly convex, not flattened; hypoproct only slightly emarginate at caudal margin ( Figs 31F; 32A).

Legs relatively long, on midbody segments about as long as body diameter ( Figs 31C; 33B). Claw at base with a short accessory spine ( Figs 32D; 33B). Tarsi and their distal setae, as well as male legs 1-3 as in P. grandicollis , P. ampullifer n. sp. or P. pallidior n. sp.

Anterior gonopods ( Fig. 33C) very much like in P. macfarlanei in coxites being contiguous but not fused medially, each coxite bearing only a single, laterally serrate, digitiform process (cxp1); telopodites (te) simple, lateral in position, movable, long, likewise digitiform, devoid of setation, with tip unciform and directed laterad. Posterior gonopods ( Fig. 33D) small, relatively simple, without traces of telopodites; each coxite with a very short, rudimentary arm (d) distomedially near a shelf-like structure; a lobiform tip and a subterminal lateral setoid laterally.

Subadults about 16 mm long, 0.9 mm wide,pallid, with 41-42p+4a+T and three blackish ocelli in two longitudinal rows.Tubercles of middle, intercalary row on midbody segments very small, rudimentary. 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

Unlike P. pallidior n. sp., in which the subadults show no traces of a row of intercalary tubercles on the midbody segments, the subadults of P. hoffmani n. sp. do have such tubercles, albeit strongly reduced in size. In this case these tubercles can be presumed as appearing not at, but towards the onset of adulthood.

Any obvious troglomorphic traits in this species seem to be absent. This contradicts the observations of Chapman (1984), who referred to an eyeless, white, troglobitic species belonging to a new genus close to Plusioglyphiulus as one of the inhabitants of this cave (det. R. L. Hoffman). Because the above material comes from the original sample collected by Chapman and provisionally identified by Hoffman, Chapman (1984) was certainly referring to P. hoffmani n. sp. The diplopod fauna of the caves of Gunung Mulu National Park is known to be rather rich and diverse, containing seven genera of four orders. Most, if not all, of the species have been presumed to be troglobites ( Chapman 1984).

Based on geographical reasons alone, when the occurrence of two congeners in the same cave is exceptional, the recent records of P. cavernicolus in several caves of Sarawak other than Bidi Caves, including a few caves from Gunung Mulu National Park ( Decu et al. 2001), are most likely to represent misidentifications.