Riotintobolus lavanono, 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 lavanono sp. nov. Figure 7

Material examined.

1 ♂ holotype, ZFMK MYR9941, Madagascar, South, Lavanono Beach, 25°25.404'S, 044°56.414'E, 27 m, spiny bush at the coast, after rain, leg. Wesener and Schütte, 18.vi.2007.

Paratypes: 16 ♂, 18 ♀, ZFMK MYR942, same data as holotype;

Etymology.

Lavanono, after the type locality, spiny forests directly next to the Lavanono Beach (Fig. 2 ). Noun in apposition.

Diagnosis.

Riotintobolus lavanono sp. nov. shares the absence of a projecting epiproct on the telson with R. anomalus , R. antafoky sp. nov., R. bovinus sp. nov., R. tsimelahy sp. nov. and R. mangatsiaka sp. nov., The posterior telopod featuring two slender, sharp projections is only shared with R. bovinus sp. nov., R. mangatsiaka sp. nov. and R. tsimelahy sp. nov. A posterior gonopod separated into three parts is only shared with R. mangatsiaka sp. nov. and R. tsimelahy sp. nov., whose habitus and gonopods look very similar to those of R. lavanono 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 dark grey in R. lavanono sp. nov. and red in both R. mangatsiaka sp. nov. and R. tsimelahy sp. nov. All three species differ by>11% uncorrected p-distance in the COI barcoding gene.

Description.

Measurements: male holotype with 47+0 segments, ca. 42 mm long, 4.2 mm wide. Largest females of type series with 46-48+0 segments, up to 58 mm long, 6.4 mm wide.

Colour (in living specimens): Body rings and head grey, appendages black (Fig. 7A ). Paraprocts and posterior margins of body segments darker grey to black (Fig. 7B ). Ozopore openings highlighted by black spot.

Head: each eye with 28-32 ommatidia in six rows. Incisura lateralis open (Fig. 7A ). Labrum with standard three irregular teeth and a single row of 10-12 stout marginal setae. Clypeus with two setiferous foveolae on each side. Antennae long, protruding back to segment 5. Length of antennomeres: 1<2>3>4=5=6. Terminal antennomere with four large sensory cones located together inside a membranous area. Antennomere 5 and 6 latero-apically with sensilla basiconica.

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

Mandible: Stipes without projection, well rounded (Fig. 7A ). Gnathal lobe not investigated.

Collum: smooth, laterally not protruding as far as ring 2 (Fig. 7A ).

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. 7B ). Epiproct well-rounded, covering, but not reaching above paraproct (Fig. 7B ). Hypoproct inconspicuous (Fig. 7B ).

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 four 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.

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

Anterior gonopod sternite massive, elongated into a wide, well-rounded triangular lobe (Fig. 7C ). Sternite in anterior view well-visible, without discernible apodemes, protruding almost as high as coxal processes. Coxite with a large, well-rounded mesal process. Telopodite with slender process arising mesally (Fig. 7C ), process apically curved with a large triangular projection, tip well-rounded, slightly protruding above lateral margin of telopodite.

Posterior gonopods consisting of three parts, separated by sutures or articulations (Fig. 7D ): a basal coxite with a slender coxite projection and a shorter telopodite, efferenct duct discharging laterally (Fig. 7E ). Process of coxite and telopodite standing in same axis. 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 before curving to the lateral margin at beginning of telopodite (Fig. 7E ). Telopodite half as wide and much shorter than coxite, standing in same axis, apically membranous, with two slender apical processes both diverging (Fig. 7D, E ). Mesal process membranous and wider, lateral process bent 90 degrees laterally, longer, slenderer and sclerotised, efferent duct seems to be ending at base of lateral process (Fig. 7E ). Base of lateral process with a short, membranous-white projection (Fig. 7E ).

Intraspecific variation.

Specimens of the same population differing between 45-47 in segment number. Females appear to be more brownish than the more greyish males.

Live observations.

R. lavanono sp. nov. could be found in great numbers after a rainy day in the late afternoon (3-5 p.m.) in a small remnant of spiny bush and under dead Opuntia remains. The specimens were only encountered in an area of a few square meters in view of the coast. Contrary to other Riotintobolus species, such as R. mandenensis and R. minutus , R. lavanono sp. nov. did not remain stiff like a stick when disturbed, but rolled-up into a spiral.

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 7. Riotintobolus lavanono sp. nov., paratype male (ZFMK MYR 942) C anterior gonopod, anterior view; posterior view D telopodite of left posterior gonopod, posterior view E left posterior gonopod, anterior view. Abbreviations: av = paraprocts; Co = collum (ring 1); Cx = coxite; Go = gonopods; Md = basal joints of mandible; Pre = epiproct; St = sternite; sub = hypoproct; T = telopodite; x = lateral swollen process; y = opening of efferent duct; z = apical membranous ' flag'; numbers refer to leg pair or segment number. Scale bars: 1 mm.