Riotintobolus mangatsiaka, Wesener, 2020

Wesener, Thomas, 2020, Ecotone shifts in southern Madagascar: first barcoding data and six new species of the endemic millipede genus Riotintobolus (Spirobolida, Pachybolidae), ZooKeys 953, pp. 1-29 : 1

Riotintobolus mangatsiaka sp. nov. Figures 4 , 5 , 6

Material examined.

1 ♂ holotype, ZFMK MYR9801, Madagascar, PN Andohahela, Mangatsiaka, 24°58.051'S, 046°33.206'E, 90 m, spiny forest, leg. Wesener and Schütte, 23.v.2007.

Paratypes: 7 ♂, 14 ♀, ZFMK MYR938, same data as holotype.

Other material examined.

1 ♂, 1 ♀, FMMC 5413, Province Toliara; RNI d’Andohahela, parcel 2; 120 m; 24°49.0'S, 46°36.6'E; pitfalls, camp 6; leg. S. Goodman 7-15.xii.1995; 1 ♂, FMMC 5379, Province Toliara; RNI d’Andohahela, parcel 2; 120 m; 24°49.0'S, 46°36.6'E; pitfalls, camp 6; leg. S. Goodman 7-15.xii.1995;

Etymology.

Mangatsiaka, after the type locality (Fig. 2 ), spiny forests next to a site called Mangatsiaka, Andohahela National Parc. Noun in apposition.

Diagnosis.

Riotintobolus mangatsiaka sp. nov. shares the absence of a projecting epiproct on the telson only with R. anomalus , R. antafoky sp. nov., R. bovinus sp. nov., R. tsimelahy sp. nov. and R. lavanono sp. nov. The posterior telopod featuring two slender, sharp projections is only shared with R. bovinus sp. nov., R. tsimelahy sp. nov. and R. lavanono sp. nov. A posterior gonopod separated into three parts is only shared with R. tsimelahy sp. nov. and R. lavanono sp. nov., whose habitus and gonopods look very similar to those of R. mangatsiaka sp. nov. Both species differ in details of the tip of the posterior gonopod and in the colour of their antennae and legs, which are red in R. mangatsiaka sp. nov. and dark grey in R. lavanono sp. nov. R. mangatsiaka sp. nov. differs from R. tsimelahy sp. nov. in the presence of just one lateral processes on the posterior gonopod. All three species differ by>11% uncorrected p-distance in the COI barcoding gene.

Description.

Measurements: male holotype with 49+0 segments, ca. 42 mm long, 4.1 mm wide. Largest females of type series with 48 to 51+0 segments, up to 52 mm long, 5.4 mm wide.

Colour (in living specimens): Body rings grey, appendages red. Head, paraprocts and posterior margins of body segments darker grey to black (Fig. 4A ). Ozopore openings highlighted by black spot (Fig. 4A, B ).

Head: each eye with 30-35 ommatidia in six rows. Incisura lateralis open (Fig. 4C ). Labrum with standard three irregular teeth and a single row of 10-12 stout marginal setae. Clypeus with two setiferous foveolae on each side (Fig. 4D ). Antennae long, protruding back to segment 5. Length of antennomeres: 1<2>3=4=5=6. Second antennomere slenderer but twice as long as first. Terminal antennomere with four large sensory cones located together inside a membranous area (Fig. 5A ). Antennomere 5 with 3 rows, antennomere 6 latero-apically with a single row of sensilla basiconica (Fig. 5B-E ). Antennomere 6 with an unknown type of at least three sensilla or duct openings located close to disc (Fig. 5D, E ).

Gnathochilarium: lamellae linguales each with two standard setae located behind one another. Stipites each with three apical setae. Palpi of similar size (Fig. 5F ). Central pads with standard two sets of sensory cones, apical area with ten cones, higher area with ~ 30 (Fig. 5G ).

Mandible: Stipes without projection, well rounded (Fig. 4C ). Gnathal lobe, external tooth simple, rounded; mesal tooth with three cusps (Fig. 6A ). Eight pectinate lamellae. Mesal margin of pectinate area (intermediate area) with ca. four rows of small, slender spines. Molar plate with few, five, transverse furrows (Fig. 6A ).

Collum: smooth, laterally not protruding as far as ring 2 (Fig. 4C ).

Body rings: ozopores starting at segment 6, marked by a black spot. Located on suture between meso- and metazonite. Rings with smooth, but irregular coriaecous surface, ventrally on metazona with transverse ridges.

Telson: paraprocts elongated, with weak lips, abundant micropunctation especially towards edges (Fig. 4E ). Epiproct well-rounded, covering, but not reaching above paraproct (Fig. 4E ). Hypoproct inconspicuous (Fig. 4E ).

Legs: leg 1 with a large cylindrical coxa, twice as long as other podomeres. Tarsus with three pairs of ventral spines and an apical spine beyond claw. Leg 2 with an elongated coxa. Tarsus with three pairs of ventral spines and a short apical spine. Midbody legs with a rectangular coxa, as long as other podomeres. Each podomere ventrally with a single or a pair of apical setae, tarsus with a single apical spine and three pairs of ventral spines. Length of midbody legs ca. 1.2 times body diameter in males.

Female sexual characters. No tarsal pads, antennae shorter than male, only protruding back to ring 2. Female vulva simple, bivalve-like (Fig. 6B ). Anterior plate smaller than posterior plate, opening with one row of setae on each plate, close to operculum.

Male sexual characters: tarsal pads present from leg 3 to midbody, small, inconspicuous (Fig. 4D ). Coxae 3-7 without coxal processes, but coxae 3-5 swollen (Fig. 3D ).

Anterior gonopod sternite massive (Fig. 4F ), elongated into a wide, well-rounded triangular lobe (Fig. 4F ). Sternite in anterior view well-visible, without discernible apodemes, protruding almost as high as coxal processes. Coxite with a large, well-rounded mesal process (FIg. 4F, G). Telopodite with process arising mesally (Fig. 4G ), process apically curved with a large triangular projection (Fig. 4G ), tip well-rounded, slightly protruding above lateral margin of telopodite (Fig. 4F ). Whole telopodite process resembling an even-sided triangle.

Posterior gonopods consisting of three parts, separated by sutures or articulations (Fig. 4H ): a basal coxite with a slender coxite projection and a slightly shorter telopodite, efferent duct discharging laterally (FIg. 4H, I). Process of coxite and telopodite standing in same axis (Fig. 4H ). Pair of posterior gonopods located parallel to each other, connected by a small, sclerotised and visible sternite (Fig. 4H ). Basal part of coxite wide, mesally with a large triangular sclerite located on lower level than remaining part (Fig. 4H ). Coxite elongated. Efferent duct running at mesal margin of coxite (FIg. 4H, I) before curving to the lateral margin at beginning of telopodite (Fig. 4I ). Telopodite as wide as but much shorter than coxite, standing in same axis (FIg. 4H, I), apically membranous, with two slender apical processes both diverging (FIg. 4H, I). Mesal process membranous and wider, lateral process longer, slenderer and sclerotised, efferent duct seems to be ending at base of lateral process (FIg. 4H, I). Base of lateral process with a short, membranous-white projection (Fig. 4I ).

Intraspecific variation.

The number of segments varies between 47 and 51.

Live observations.

R. mangatsiaka sp. nov. could be found in great numbers in the early morning (7-9 a.m.) on the forest floor of the spiny bush. The otherwise dry spiny bush was still quite wet because of dew. No juveniles were observed. Contrary to other Riotintobolus species, such as R. mandenensis and R. minutus , R. mangatsiaka sp. nov. did not remain stiff like a stick when disturbed, but rolled-up into a spiral (Fig. 4B ), a common defence behaviour for juliform millipedes.

Figures

Figure 2. Distribution of the newly described Riotintobolus species, as well as of the still undescribed species. Vegetation marks modified from Moat and Smith 2007.

Figure 3. Riotintobolus tsimelahy sp. nov., holotype (ZFMK MYR 99940) (A-F) and male paratype (ZFMK MYR 9949) (G, H) A multi-layer photograph, male anterior body, lateral view B multi-layer photograph, male leg pairs 1 - 7, ventral view C multi-layer photograph, male posterior body end with telson D anterior gonopod, anterior view E left posterior gonopod, posterior view F right posterior gonopod, anterior view G damaged? left posterior gonopod, posterior view H damaged? right posterior gonopod, anterior view. Abbreviations: av = paraprocts; Co = collum (ring 1); Cx = coxite; Md = basal joints of mandible; Pre = epiproct; St = sternite; sub = hypoproct; T = telopodite; x = lateral swollen process; z = apical membranous ' flag'; numbers refer to leg pair number. Scale bars: 1 mm.

Figure 4. Riotintobolus mangatsiaka sp. nov., paratypes (ZFMK MYR 938) A living female B living male in defensive position C multi-layer photograph, male anterior body, lateral view D multi-layer photograph, male leg pairs 1 - 7, ventral view E multi-layer photograph, male posterior body end with telson F anterior gonopod, anterior view G anterior gonopod, posterior view H right posterior gonopod, posterior view I right posterior gonopod, anterior view. Abbreviations: av = paraprocts; Co = collum (ring 1); Cx = coxite; Md = basal joints of mandible; Pe = penis; Pre = epiproct; St = sternite; sub = hypoproct; T = telopodite; x = lateral swollen process; y = opening of efferenct duct; z = apical membranous ' flag'; numbers refer to leg pair number. Scale bars: 1 mm.

Figure 5. Riotintobolus mangatsiaka sp. nov., male (FMMC 5413), SEM A left antennae B antennomere 5 C details of sensilla basiconica D antennomere 6 E detail of unknown sensilla / pore opening F gnathochilarium underside G gnathochilarium, detail of right central pad. Abbreviations: cP = central pads; d = disc; iP = inner palpus; LP = lateral palpus; s = unknown sensillum; sb = sensilla basiconica; numbers refer to antennomere number. Scale bars as indicated.

Figure 6. Riotintobolus mangatsiaka sp. nov., male and female (FMMC 5413), SEM A left gnathal lobe of mandible, mesal view B left female vulva, lateral view. Abbreviations: av = anterior orientated plate; 3 iT = 3 - combed inner tooth; eT? external tooth; LT = lateral tooth; mp = molar plate; O = operculum; pL = pectinate lamellae; pv = posterior orientated plate. Scale bars as indicated.