Riotintobolus tsimelahy, 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 tsimelahy sp. nov. Figure 3

Material examined.

1 ♂ holotype, ZFMK MYR9940, Madagascar, PN Andohahela, Tsimelahy, 24°57.296'S, 046°37.214'E, 135 m, spiny forest, coll. Wesener and Schütte, 24.v.2007.

Paratypes: 9 ♂, 12 ♀, ZFMK MYR941, same data as holotype; 1 ♂, ZFMK MYR9950, same data as holotype; 1 ♂ with damaged gonopods; ZFMK MYR9949, same data as holotype.

Other material examined.

3 ♂ and ♀, BLF 5239 (CASENT9032808), Madagascar, Toliara, Forêt de Mahavelo, Isantoria River, 24°45'30"S, 46°9'26"E, 110 m, 28.i-1.ii.2002, spiny forest/thicket, EH18 pitfall trap, coll. B. L. Fisher et al.; 1 ♂, 1 imm., MZUF Fi-10, Madagascar; Andohahela, 6-12.xii.1991, leg B. Randriamampionona.

Etymology.

Tsimelahy, after the type locality (Fig. 2 ), spiny forests next to the Tsimelahy River, Andohahela National Parc. Noun in apposition.

Diagnosis.

Riotintobolus tsimelahy 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. mangatsiaka sp. nov. and R. lavanono sp. nov. The posterior telopod featuring two slender, sharp projections is only shared with R. bovinus sp. nov., R. mangatsiaka sp. nov. and R. lavanono sp. nov. A posterior gonopod separated into three parts is only shared with R. mangatsiaka sp. nov. and R. lavanono sp. nov., whose habitus and gonopods look very similar to those of R. tsimelahy 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. tsimelahy sp. nov. and dark grey in R. lavanono sp. nov. R. tsimelahy sp. nov. differs from R. mangatsiaka sp. nov. in the presence of two lateral processes on the posterior gonopod. All three species differ by>11% uncorrected p-distance in the COI barcoding gene.

Description.

Measurements: Telson not included in counts of segments. Male holotype with 50+0 segments, ca. 44 mm long, 4.3 mm wide. Largest females of type series with 49 or 50+0 segments, up to 50 mm long, 5.3 mm wide.

Colour (in living specimens): Body rings grey, appendages red. Head, paraprocts and posterior margins of body segments darker grey to black. Ozopore openings highlighted by black spot (Fig. 3A, C ).

Head: each eye with 30-35 ommatidia in six rows. Incisura lateralis open (Fig. 3A ). 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. 3B ). 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.

Gnathochilarium: lamellae linguales each with two standard setae located behind one another. Stipites each with three apical setae. Palpi of similar size. Endochilarium not dissected.

Mandible not dissected.

Collum: smooth, laterally not protruding as far as ring 2 (Fig. 3A ).

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

Telson: paraprocts elongated, with weak lips, abundant micropunctation especially towards edges (Fig. 3C ). Epiproct well-rounded, covering, but not reaching above paraproct (Fig. 3C ). Hypoproct inconspicuous (Fig. 3C ).

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 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. Vulvae not dissected.

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

Anterior gonopod sternite massive (Fig. 3D ), elongated into a wide, well-rounded triangular lobe (Fig. 3D ). Sternite in anterior view well-visible, without discernible apodemes, protruding almost higher than coxal processes. Coxite with a large, well-rounded mesal process (Fig. 3D ). Telopodite with process arising mesally (Fig. 3D ), process apically curved with a large triangular projection (Fig. 3D ), tip well-rounded, slightly protruding above lateral margin of telopodite (Fig. 3D ). Whole telopodite process resembling an even-sided triangle.

Posterior gonopods consisting of three parts, separated by sutures or articulations: a basal coxite with a slender coxite projection and a slightly shorter telopodite, efferent duct discharging laterally (Fig. 3E, F ). Process of coxite and telopodite standing in same axis (Fig. 3E, F ). Pair of posterior gonopods located parallel to each other, connected by a small, sclerotised and visible sternite. Basal part of coxite wide, mesally with a large triangular sclerite located on lower level than remaining part. Coxite elongated. Efferent duct running at mesal margin of coxite (Fig. 3E ) before curving to the lateral margin at beginning of telopodite (Fig. 3E ). Telopodite as wide as but much shorter than coxite, standing in same axis (Fig. 3F ), apically membranous, with one triangular apical process and two slender lateral processes (Fig. 3E, F ). Lateral processes straight, running almost parallel to one another, slender and sclerotised, efferent duct seems to be ending at base of lateral process (Fig. 3E ). Base of lateral process with a short, membranous-white projection (Fig. 3E ).

Intraspecific variation.

The number of segments varies, even within one population, between 47 and 51. The population from the Forêt de Mahavelo (Fig. 1) differs by 1.5% uncorrected p-distance of the COI gene to those from the type locality, Tsimelahy (Suppl. material 1). One small male from the type series (ZFMK MYR9949) has incompletely developed posterior gonopods, either a sign of healed damage (there are black spots on it), or maybe not fully developed (FiIg. 3G, H).

Live observations.

R. tsimelahy 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. tsimelahy sp. nov. did not remain stiff like a stick when disturbed, but rolled-up into a spiral, 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.