Riotintobolus minutus Wesener, 2009

Wesener, Thomas, Enghoff, Henrik & Sierwald, Petra, 2009, Review of the Spirobolida on Madagascar, with descriptions of twelve new genera, including three genera of ' fire millipedes' (Diplopoda), ZooKeys 19 (19), pp. 1-128 : 52-53

Riotintobolus minutus Wesener , sp. n.

urn:lsid:zoobank.org:act:69657A54-E55E-4B78-BD6A-C14D398BC1F6

Material examined: 1 ♂, 2 ♀, 2 imm. Holotype: 1 ♂ (22 mm long), FMMC, Province Toliara, Sainte Luce, S 9, littoral forest on sand, in leaf litter (deep), 24°47’ S, 47°10’ E, leg. T. Wesener, 06.IV.2003 . Paratypes: 1 ♀, 2 imm., FMMC, same data as holotype ; 1 ♀, FMMC W031 B, Sainte Luce, S 9, in leaf litter with roots, 24°46.769’ S, 47°10.288’ E, 12 m, littoral forest on sand, leg. Wesener et al., 01.VI.2007 .

Differential diagnosis: R. minutus is the smallest known species of the genus and with a body length in mature males of only 22 mm, one of the smallest Spirobolida species known from Madagascar. The pitch-black colour with a thick dorsal red stripe ( Fig. 27A ) helps to clearly identify this species. The gonopods of this species are in some aspects similar to those of R. mandenensis and R. anomalus sp. n.

Description. Measurements: male holotype with 38 podous and 2 apodous rings, 22 mm long, 2.3 mm wide. Females with 39–41 podous and 0–2 apodous body rings, 23–26 mm long, 2.9 mm wide.

Coloration pitch-black, dorsally with an extraordinary wide, red stripe ( Fig. 27A ). Openings of ozopores highlighted by a red spot ( Fig. 27B ). Posterior half of collum dorsally black ( Fig. 27E ). Head, lateral part of anal valves and subanal scale red, legs whitish brown ( Fig.40B ). Eyes with 12–14 partly fused ocelli arranged in three rows ( Fig. 27E ). Antennae protruding back to body ring 2 ( Fig. 27B ). Legs lacking tarsal pads. Male legs reach 0.7 times, female legs 0.5 times, body diameter ( Fig. 27D ). Preanal process sharp-edged, but not protruding above anal valves ( Fig. 27G ). Anal valves small, at midanterior part with a deep groove. Margin of lip towards groove sharp-edged ( Fig. 27G ).

Anterior gonopod sternite apically elevated into a wide lobe with a triangular, wellrounded tip ( Fig. 27H ). Sternite tip almost as high as mesal coxite process, which is relatively slender but longer than sternite ( Fig. 27H ). Telopodite on posterior side apically with a large triangular, retrorse process ( Fig. 27J ), which is projecting above coxite and telopodite margins ( Fig. 27J ).

Posterior gonopods telopodite laterally with two large, finger-shaped processes ( Fig. 27I ). Sperm canal discharging at more apical process. Apically, a large membrane present, extending into two lobes, apically twice as wide as basally ( Fig. 27K ).

Intraspecific variation: females with 39+2 and 41+0 body rings are known, indicating post-mature moults.

Distribution and ecology: this species was only collected in the isolated littoral rainforest on sand in Sainte Luce ( Fig. 25 ). Only circa 200 ha of this forest will remain after a large scale mining project ( Vincelette et al. 2003, Bollen and Donati 2006). Although officially protected, large scale wood removal and even slash-and-burn agriculture ( Fig. 24C ) is still ongoing in this forest (own observations in March 2003 and June 2007). The surrounding pseudosteppe is regularly burned, further endangering this forest ( Fig. 24B ). However, further searches should be conducted in small remaining coastal forests north of Sainte Luce, where this species could also occur. All specimens were found deep in the soil under the wet leaf litter. Disturbed specimens often did not curl into a spiral, but remained motionless and stiff like a stick even when picked up. The giant pill-millipede species Sphaeromimus splendidus Wesener & Sierwald, 2005 and a still undescribed Zoosphaerium species are currently also only known from the littoral forest of Sainte Luce ( Wesener and Sierwald 2005, Wesener and Wägele 2008).

Etymology: minutus , adjective, refers to the small size of this species.

Figures

Figure 24. A Riotintobolus mandenensis sp. n., living specimens B pseudosteppe and burned shrubs dominating the area between the littoral forests of Mandena and Sainte Luce, SE Madagascar C Sainte Luce littoral forest, manioc plantation and destroyed trees inside conservation zone S8.

Figure 25. Distribution of the genus Riotintobolus gen. n.

Figure 27. Riotintobolus minutus sp. n., A–E female paratype(s), F–K male holotype. A two living specimens B habitus C gnathochilarium, overview; D midbody ring with leg pair E head, detail of incisura lateralis F legs 1–5, ventral view G telson H anterior gonopod, anterior view I left posterior gonopod, anterior view Į anterior gonopod, posterior view K left posterior gonopod, posterior view. av = anal valves; Co = collum; Cx = coxite; d-g = ozopores; Gr = groove; IL = incisura lateralis; L = ledge; Md = mandible; Pe = “penes”; Pre = preanal ring; St = sternite; T = telopodite; Te = telson. Scale bars = 1 mm.

Figure 40. Caprobolus andringitra sp. n. male paratype, SEM. A antenna, overview B antenna, apical view on disc C antennomere 5 with sensilla basiconica D gnathochilarium, ventral view E endochilarium detail F left mandible, mesal view G mandible, detail of pectinate lamella. 3iT = 3-combed internal tooth; cp = central pads of endochilarium; Endo = endochilarium; eT = external tooth; L = ledge; LT = lateral tooth; Me = mentum; mp = molar plate; pL = pectinate lamella; sb = sensilla basiconica; ST = stipites.