Lissodesmus nivalis, Mesibov, Robert, 2018

Mesibov, Robert, 2018, A new, alpine species of Lissodesmus Chamberlin, 1920 from Tasmania, Australia (Diplopoda, Polydesmida, Dalodesmidae), ZooKeys 754, pp. 103-111 : 103-107

Lissodesmus nivalis sp. n. Figs 2, 3

Holotype.

Male, Ben Lomond ski village, Tasmania, -41.5357, 147.6618, ± 25 m, 1490 m a.s.l., 2 April 2018, K. Bonham and R. Mesibov, QVM 2018:23:0038.

Paratypes.

1 male, 1 female, details as for holotype, QVM 2018:23:0039.

Other material

. Tasmania, QVM: 1 male, Giblin Fells, Ben Lomond, -41.5471, 147.6666, ± 100 m, 1540 m a.s.l., 15 April 2017, K. Bonham, 2017:23:0185, gonopod telopodite with femoral processes broken off; 1 stadium VI male, Surprise Vale, Ben Lomond, -41.5392, 147.6719, ± 50 m, 1450 m a.s.l., 20 November 2017, R. Mesibov, 2017:23:0244.

Diagnosis.

Distinguished from all other Lissodesmus species by a unique combination of character states of gonopod telopodite processes: solenomere without pre-apical process, tibiotarsus Y-shaped, femoral process L-shaped with forked tips, prefemoral process with long comb of teeth below irregularly dentate apical margin, roughened "shoulder process" near base of prefemoral process.

Description.

Male/female approximate measurements: length 25/25 mm, midbody vertical diameter 2.1/2.5 mm, midbody width across paranota 3.2/3.5 mm. Live specimens yellowish-brown to chestnut brown with pinkish red antennae (darker distally) and pinkish red legs (darker basally); rings darkest at posterior metatergal margin and along paranotal margins.

Male with vertex sparsely setose and frons moderately so. Antennal sockets separated by 2X socket diameter. Antenna short, just reaching ring 3 when manipulated backwards; relative length of antennomeres 2>(3,6)>(4,5), antennomere 6 widest. Col lum slightly narrower than head, slightly wider than tergite 2; anteriorly very slightly convex, laterally slightly convex; posterior edge medially a little emarginate; corners rounded. Tergite width increasing gradually from rings 2-6, then subequal, then decreasing 17-19. Waist (Fig. 2A, B) well-defined, with faint longitudinal striations. Prozonites and metazonites with faint cellular sculpturing; limbus composed of close-set flat tabs. Paranota (Fig. 2A, B) smooth, swollen, wide (ratio of overall width to prozonite width ca 1.4 on midbody ring); anterior shoulder tightly curved, projected anteriorly; lateral margin slightly convex, sometimes with small notches detectable, the first and last usually with 1 short seta on anterior corner of notch; posterior corner rounded, not extending past posterior metatergite margin on most rings, produced as rounded tooth on rings 17-19; posterior corner seta prominent, erect. Ozopore (Fig. 2B) small, opening dorsolaterally close to paranotal margin and anterior to posterior paranotal corner; pore formula 5, 7, 9, 10, 12, 13, 15-19. Spiracles with rims slightly raised above pleural surface; anterior spiracle on diplosegments larger, posterior spiracle about midway between leg bases. Sternites about as long as wide, with fine, short, sparse setae; transverse impression much deeper than longitudinal. Legs short; from legpair 3 prefemur greatly swollen dorsally, femur somewhat swollen dorsally, gradually less so posteriorly; most legs with postfemur and tibia expanded ventrodistally; relative podomere lengths tarsus>femur>prefemur>(postfemur, tibia) on midbody legs; tarsus straight. From legpair 3, sphaerotrichomes on prefemur, femur, postfemur, tibia and tarsus, densest on tibia and tarsus; each sphaerotrichome hemispherical with blunt-tipped, tapered setal shaft inclined distoventrally; dense brush setae on prefemur and femur, tapering with blunt tips; no sphaerotrichomes or brush setae on last 2 legpairs. Pre-anal ring with sparse, long setae; hypoproct paraboloid; epiproct extending a little past anal valves, sides slightly emarginate, tip truncate between 2 short, rounded, apical bumps; spinnerets in square array in shallow, low-walled cavity just ventral to epiproct tip.

Gonopore small, opening on rounded, mediodistal enlargement of leg 2 coxa. Gonopod telopodites extending to leg 5 bases when retracted; bases of legs 6 and 7 well-separated, coxae of legs 6 and 7 slightly swollen ventrally; sternite between legs 6 and 7 slightly excavate, with brushes of long, stiff setae on sternite just medial to coxae. Aperture ovoid but with anterior margin straight, wider than long, about 1/2 the width of ring 7 prozonite, rim slightly raised laterally.

Gonopods: gonocoxae truncate-conical, tapering distally, lightly joined medially, moderately setose on posterobasal surface. Telopodite (Figs 2C, 3) long, slender, gently curving anteriorly from base, with a band of long setae (Fig. 3C) on posterolateral surface from telopodite base almost to level of solenomere base. Telopodite base tapering from thickened basal rim. Cannula prominent, entering telopodite base in excavation lined with fine setae; prostatic groove running on anterior surface of telopodite before joining base of solenomere, opening at solenomere tip. Solenomere thin, rod-like, tapering to point, arising at ca 1/2 telopodite height on anteromedial surface, directed a little posterodistally before curving anterodistally. Tibiotarsus arising on posterior surface a little distal to level of solenomere base, thicker than solenomere, directed distomedially, apex bifurcated, the tips blunt. Femoral process arising on anterolateral surface distal to tibiotarsus origin, L-shaped; the longer portion of the “L” directed posterodistally with a forked tip; the shorter portion of the “L” directed posterobasally, also with forked tip but with distal portion of fork larger than basal portion. In distal 1/3 of telopodite, prefemoral process separated on posteromedial side from prominent, tab-like “shoulder” process with irregularly and bluntly toothed margin. Prefemoral process flattened anterolaterally, curving medially near obliquely truncate apex, with apical margin irregularly and bluntly toothed and with ca 15 discrete teeth forming comb on posterior margin.

Female closely resembling male but a little wider; legs not swollen. Genital aperture with posterior margin rounded-triangular medially; cyphopods not examined.

Name.

Latin nivalis , of snow; adjective. This species spends several months each winter with its habitat covered in snow.

Distribution.

So far known only from alpine moorland and shrubland at three localities on the Ben Lomond plateau in northeast Tasmania (Fig. 1A, B). Found in peaty material under prostrate and rock-hugging alpine shrubs (Fig. 1C).

Remarks.

The gonopod telopodite of L. nivalis sp. n. shares several features with other Tasmanian Lissodesmus species. As in L. anas and L. horridomontis , for example, the prefemoral process is offset laterally by the distal development of a roughened, tab-like “shoulder” process. The tibiotarsus has a bifurcated tip, as in L. cornutus and L. montanus , and the femoral process is L-shaped, as in L. clivulus and L. latus . However, the distinctive combination of telopodite characters in L. nivalis sp. n. makes it hard to judge from morphology what its nearest relation in the genus might be. It is quite unlike the five other Lissodesmus species found in the Ben Lomond area, namely L. adrianae , L. cognatus , L. devexus , L. hamatus and L. plomleyi .

The upright portion of the femoral process “L” is doubly forked on the left gonopod of the paratype male (Fig. 3D). There is no second bifurcation on the right gonopod of the paratype, or on the femoral processes of the holotype, so the double forking appears to be a developmental abnormality. (The third, non-type male is missing its femoral processes.)

The holotype and paratypes were collected by Tasmanian land snail specialist Kevin Bonham in company with the author. We searched the group of rocks shown in Fig. 1C and similar nearby habitats for more than an hour but found no more L. nivalis sp. n., although we saw scattered specimens of the common northeast Tasmanian dalodesmids L. adrianae and Tasmaniosoma clarksonorum Mesibov, 2010. My collecting in November 2017 was even less successful, yielding only one presumed juvenile of L. nivalis sp. n., despite my searching a larger area of apparently suitable shrub habitat for several hours. L. nivalis sp. n. may be naturally scarce in its alpine habitat.

The types were collected live and transported from the field in a collecting jar filled with peaty material. As often happens when dalodesmids are live-collected, the female and one of the males (the holotype) mated in the jar and were still in copula when killed by freezing several hours later. In Fig. 2C, white amorphous material (spermatic fluid?) can be seen adhering to the gonopod telopodites of the holotype.