Hirudicryptus quintumelementum, Korsós & Geoffroy & Mauriès, 2009

Korsós, Zoltán, Geoffroy, Jean-Jacques & Mauriès, Jean-Paul, 2009, The fifth element: reconnection of the disjunct distribution of the members of Siphonocryptida (Diplopoda) with the description of a new species from Nepal, Journal of Natural History 43 (7 - 8), pp. 435-445 : 436-442

Hirudicryptus quintumelementum sp. nov.

( Figures 1–9 )

Material studied

3 ♀♀, Nepal, Siwapuri Dara (5Sheopuri Lekh), 15 km NE of Kathmandu, 2450 m, dry mature oak forest; little brook in a shallow gulley, sifting of vegetation, fallen leaves and other debris on moist to wet habitats along the brook (No. 250), 29. April 1985, leg. A. Smetana.

Holotype

Intact female specimen (34 segments), GMNH.

Paratypes

Female with 35 segments (dissected for temporary glycerine, and permanent SEM mounts); and another female with 27 segments, MNHN [ MNHN BB001 ] .

Etymology

The species is named as the fifth member of the millipede order Siphonocryptida ; but also in honour of the alien custodians (called ‘‘mondoshawans’’) in the movie by Luc Besson (‘‘Le cinquième élément’’ 1997) who eventually saved the Earth from a catastrophe, and whom the head and the collum of the new species (and actually all members of the order) resemble superficially.

Diagnosis

Member of the genus Hirudicryptus (family Siphonocryptidae , order Siphonocryptida ) as defined by Enghoff and Golovatch (1995), in having a narrow body (length/width ratio is.6) with midbody terga ca. four times wider than long, and a broad, crescent-shaped collum with no earlike lobes. Differs from other species of the genus in colouration and in the surface of the body terga being strongly granulate, with a transverse row of about 9–11 well-developed dark tubercles at the posterior margin on each side.

Description

♀ (holotype) 34 segments (incl. collum, without telson), body length 6.2 mm, max. width 0.9 mm; paratypes (♀♀): 35 and 27 segments, body length 7.7 and 4.8 mm, max. width 1.1 and 0.8 mm, respectively. Body length/width ratio: 6.9, 7, and 6, for the three specimens. See also Figure 1 .

Colour ( Figures 2 and 3). A light yellow mid-dorsal and two dark brown lateral stripes make the animal appear to have three equal stripes. This pattern is unique in the order except for S. latior where the light median stripe is less pronounced and also narrower ( Enghoff and Golovatch 1995). Tubercles at the posterior margin of the marbled paraterga are dark brown. Antennal segments distally, and sides of head are darker brown, eyespots black in dark patches. Underside, legs, telson uniformly light yellowish.

Head ( Figures 4 , 7–8 ). Elongated, proboscoid, sharply pointed triangular, about as long as wide. In dorsal view completely hidden under collum, only antennae visible. Antennae stout, slightly bent ventrad, with six antennomeres subequal in length, the last (seventh) much shorter, its length about one-third of the sixth. Ocelli 2+2, black, posterior bigger than anterior ones. A pair of long frontal setae present.

Collum ( Figures 4 , 7–8 ). Distinctly separate from second tergum, dorsally and in anterior view crescent-shaped, forming two smooth subrectangular lobes, without ventro-lateral ‘‘ears’’. In lateral view dorsal part highly elevated and protruded forwards, casque or helmet-shaped, widely separated from second tergum.

Body terga. Midbody terga ( Figures 3 and 5 ) about four to five times broader than long, slightly tapering towards both ends, with deep, distinct middorsal suture along entire length. Large, dark brown tubercles from the fourth tergum onwards, 9–11 on each half, uneven, partly paired and distributed at the posterior margin (1222221222121+1212221222221 is a usual arrangement). The 1+1 median ones usually the largest, and most conspicuous with their dark brown colour against the light median dorsal stripe. Postero-lateral projections on each tergum from third onwards strong, but not passing posterior tergal contour, also coloured dark brown. Arrangement of paraterga normal, 2–5 not overlying the preceding ones. Lateral margin of paraterga forming strong peritreme from fifth onwards, occupying almost entire length of paraterga, large ozopore on the fifth anteriorly, from the sixth onwards more or less in median position. Last tergum ( Figure 6 ) rounded or subtrapeziform, with a median longitudinal suture, but without posterior lobes, and no indication of (diplo)fusion.

Sterna . At midbody much wider than long, about two times wider than coxae.

Telson. Very small, completely hidden under last tergum, with two strong setae. Anal valves with two smaller setae directed ventrad.

Legs. Long, slender, in normal position not surpassing body margin (except under posteriormost terga). Coxa widely separated from each other. Telopodite comprising five podomeres. No accessory claw.

Male sexual characters. In the absence of males in the present sample, no description of gonopods can be presented.

Female sexual characters ( Figure 9 ). It should be emphasized that this is the first time that the vulvae of a female siphonocryptid have been properly studied (i.e. after removal, under a compound microscope). The following description is essentially based on polyzoniid terminology, and compared with members of that order.

Coxae of second legpair hypertrophied and very close to each other due to the fact they use the space usually occupied by the coxal sacs of other subsequent legpairs. Vulval cavity (termed ‘‘lucarne’’ by Brölemann 1935: 50), very large, using mesally more than half of posterior part of coxa, in a similar way as in Polyzoniida. In contrast, however, each vulva provided with a strongly developed operculum, entirely closing the vulval cavity. Operculum simple, rectangular plate, apically rounded and slightly concave. No setae or hairs could be observed at all, unlike most other diplopod vulvae. Bursa more or less globular as in Polyzoniida, with prominent vertical cleft dividing it into two subequal and poorly chitinized halves. In analogy with the structures generally encountered in other diplopod vulvae these two parts could be termed as internal and external ‘‘valves’’. Under a compound microscope, in continuation of medial cleft the outline of an apodematic tube can be distinguished (see dotted line in Figure 9 ), together with a spherical receptaculum seminis beneath.

Updated key to the five species of Siphonocryptida

1. Body very broad, length/width ratio of body 1.9–3.0, midbody terga ca. six times wider than long. First five paraterga overlying preceding paraterga, collum anteriorly with two extra, subrectangular lobes (‘‘ears’’). No frontal setae................... Siphonocryptus .................... 2

Body much narrower, length/width ratio.4 (except in very small juveniles), midbody terga ca. four times wider than long. Anterior paraterga not overlapping ‘‘reversely’’, collum simple crescent-shaped, with broad lobes in anterior view. Two long frontal setae.............. Hirudicryptus ............... 3

2. With a dorsal colour pattern of three dark and two light longitudinal stripes, body narrow, paratergal projections surpassing posterior contour of tergum, apical part of terminal podomere of posterior gonopods longer. (Sumatra).............................................. S. compactus

A mid-dorsal light stripe (or body uniformly pale), body broad, paratergal projections not surpassing posterior contour of tergum, apical part of terminal podomere of posterior gonopod shorter. (Malaya)............. S. latior

3. With a dorsal colour pattern of five longitudinal stripes: one median and two lateral dark ones, with two light ones between...................... 4

Dorsal colour pattern different: only three longitudinal stripes of equal width, one median light and two lateral dark ones. ( Nepal)

................................. H. quintumelementum sp. nov.

4. Body very narrow, adult specimens even with more than 50 paraterga are only 1.2 mm wide. Number of tubercles on posterior margin of each half of midbody paraterga 14–15. Terminal podomere of male posterior gonopod long, slender, simple. (Macaronesian islands)....................... H. canariensis Body less narrow, adult specimens with approximately 50 paraterga are 2.0– 2.5 mm wide (almost like S. latior ). Tubercles on posterior margin of midbody paraterga large, the number on each half only 6–8. Terminal podomere of male posterior gonopod with a clearly visible, distinct shoulder at its proximal third. (Taiwan) ....................................... H. taiwanensis

Figures

Figure 1. Body size relationships (max. body width plotted against number of terga) of four species of Siphonocryptida.

Figure 2. Hirudicryptus quintumelementum sp. nov. Paratype (27 terga), lateral view.

Figure 4. Head with collum and second tergum, fronto-lateral view. Scanning electron micrograph. Scale 0.1 mm.

Figure 5. Midbody terga, showing enlarged tubercles at posterior margin in dorsal view. Scanning electron micrograph. Scale 0.1 mm.

Figure 6. Last tergum, dorsal view. Scanning electron micrograph. Scale 0.1 mm.

Figure 7. Hirudicryptus quintumelementum sp. nov. Holotype, anterior part of body, frontolateral view. Antennal setae have been omitted. Scale 0.1 mm.

Figure 8. Hirudicryptus quintumelementum sp. nov. Holotype, anterior part of body, left lateral view. Scale 0.1 mm.

Figure 9. Right second leg and vulva, ventro-caudal view. Notes: Op, operculum; vi-ve, internal and external valves; C, coxa; st, sternum. Scale 0.1 mm.