Alluviobolus omega, Wesener, 2024

Wesener, Thomas, 2024, Five new species and numerous locality records of Spirobolida millipedes from Madagascar (Diplopoda, Spirobolida, Pachybolidae), Zootaxa 5529 (3), pp. 461-486 : 470-475

publication ID	https://doi.org/ 10.11646/zootaxa.5529.3.3
publication LSID	lsid:zoobank.org:pub:716EDF67-C933-484D-911B-4585B11187A6
DOI	https://doi.org/10.5281/zenodo.14034006
persistent identifier	https://treatment.plazi.org/id/0394B500-FFDD-FFB3-FF32-2CD4D249FD80
treatment provided by	Plazi
scientific name	Alluviobolus omega
status	sp. nov.

Treatment

Alluviobolus omega sp. nov.

Figs 5–9 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9

Material examined. Holotype: 1 M, FMNH-INS 5458 , Madagascar, Province Toliara, Forêt de Vohibasia #3, 59 km NE Sakaraha, tropical dry forest, 780 m, 22°27.5’ S, 044°50.5’ E, coll. S. Goodman, 10–16.i.1996. GoogleMaps

Paratypes: 1 F, FMNH-INS 5458 , same data as holotype; 3 M, 1 F GoogleMaps , FMNH-INS 5462 , Province de Toliara, Forêt de Vohibasia , 59 km NE Sakaraha, 780 m, 22°27.5’ S, 44°50.5’ E, leg. S. Goodman, 10–16.i.1996 GoogleMaps ; 1 M, FMNH-INS 5403 , Province de Toliara, Forêt de Vohibasia , 59 km NE Sakaraha, 780 m, 22°27.5’ S, 44°50.5’ E, coll. S.M. Goodman, 10.i.1996 GoogleMaps .

Other material: 1 M, FMNH-INS 5396 , Province de Toliara, Forêt de Vohimena , 35 km SE Sakahara, 780 m, 22°41.0’ S, 44°49.8’ E, coll. S.M. Goodman, pitfalls, 17–24.i.1996 GoogleMaps ; 10 M, 2 F, CAS BLF 7381 , Madagascar, Province Fianarantsoa, Forêt d’Analalava , 29.6 km 280° W Ranohira, tropical dry forest, 700 m, 22°35’30” S, 045°07’42” E, coll. Fisher, Griswold et al., pitfall trap, 1–5.ii.2003 GoogleMaps ; 1 M, CAS BLF 7306 , Madagascar, Province Fianarantsoa, Parc National d’Isalo , 9.1 km 354°N Ranohira, gallery forest, 725 m, 22°28’54” S, 045°27’42” E, coll. Fisher, Griswold et al., pitfall trap, 27–31.i.2003 GoogleMaps .

Derivatio nominis. omega, noun in apposition, after the last letter of the Greek alphabet.The posterior gonopods resemble the letter “Z”, the last letter in our Lain alphabet.

Diagnosis. The gnathochilarium with the division of the mentum and the sclerotized ledges on the stipites and mentum identify this species a member of a group uniting several genera of small-bodied Malagasy Pachybolidae (see Wesener et al. 2009a). This species is placed in the genus Alluviobolus because of the posterior telopods, in which the coxite and telopodite are clearly separated, the telopodite with a torsion so that the opening of the spermatic groove (or sperm channel) discharges apico-laterally. A. omega sp. nov. differs strongly from the other three Alluviobolus species distributed in the SE of Madagascar: the anterior telopod has a weaker telopodite process, the posterior telopod is unique, almost resembling the letter ‘Z’ with a hole in anterior view and numerous large membranous folds apico-mesally.

Description

Measurements: holotype male with 45+0 body rings, ca. 36 mm long, midbody rings 3.1 mm wide. Other males with 45 or 46+0 body rings, length up to 39 mm, midbody ring width up to 3.4 mm. Females larger, large paratype female with eggs ca. 56 mm long, at midbody rings 5.1 mm wide, with 46+0 body rings.

Colour: Head and collum black, only on margins red ( Fig. 5A View FIGURE 5 ), legs, antennae ( Fig. 5B View FIGURE 5 ) and anal valves ( Fig. 5C View FIGURE 5 ) red. Telson and body black, dorsally with a thin red stripe.

Head:Eyes with 30 ommatidia arranged in 4–5 rows ( Fig.5A View FIGURE 5 ).Antennae, length of antennomeres1<<2>3>4>5=6 ( Fig 7A View FIGURE 7 ), with fields on sensilla basiconica on 5th and 6th ( Figs 7B, C View FIGURE 7 ), 4 apical cones ( Fig. 7B View FIGURE 7 ). Antennae in male long, reaching back to 5th body ring ( Fig. 5A View FIGURE 5 ), in female much shorter, protruding back to body ring 2. Head with 2/2 labral grooves and 2/2 setae on lamellae linguales of gnathochilarium ( Fig. 5A View FIGURE 5 ). Gnathochilarium with a mentum divided by a suture, stipites each with three apical setae ( Fig. 8A View FIGURE 8 ). Central pads of gnathochilarium with two sets of sensory cones, one rounded spot with 6 or 7 located more apically and an oval field with cones in 3–4 rows closer to the endochilarium ( Fig. 8B View FIGURE 8 ). Mandible with a 3-combed inner tooth, pectinate lamellae with teeth in 5–6 rows, molar plate relatively small, with 6 ridges ( Fig. 8C View FIGURE 8 ).

Ozopore starting at 6th ring ( Fig. 5A View FIGURE 5 ), located on suture between meso- and metazonite ( Figs 5C View FIGURE 5 , 9B View FIGURE 9 ).

Legs in both sexes long, longer than width of body rings ( Fig. 6F, G View FIGURE 6 ). Male legs without tarsal pads ( Figs 6F View FIGURE 6 , 8D, E View FIGURE 8 ). Male legs 3–5 with cylindrical coxa processes, tip broadly rounded. Process of coxae 3 and 4 bent posteriorly, 3rd tip protruding to 4th, 4th tip protruding to 5th coxa. 5th coxa process not bent, short. 6th and 7th coxae flat & broad ( Fig. 5B View FIGURE 5 ). Legs 8+ in male with a cylindrical, basally tapering coxa, femur longest podomere, length of podomeres: coxa <prefemur<femur>postfemur>tibia<tarsus, tarsus as long as prefemur. Each podomere in both sexes with an apical spine ( Fig. 6F, G View FIGURE 6 ). Male tarsus with short sharp claw with small paronychium ( Fig. 8D, E View FIGURE 8 ), single short apical spine above claw ( Figs 6F View FIGURE 6 , 8E View FIGURE 8 ) and 5 or 6 short ventral spines. Female leg similar to male leg, with four ventral spines ( Fig. 6G View FIGURE 6 ).

Anal valves not invaginated. No pre-anal processes ( Fig. 5C View FIGURE 5 ).

Female vulva simple, bivalve-like, with a small, poorly sclerotized operculum at base ( Fig. 8F View FIGURE 8 ). Posterior valve apically overlapping part of anterior one. Basally on each valve towards opening with two or three rows of setae

Anterior gonopods massive and wide ( Figs 5D, E View FIGURE 5 , 6A, B View FIGURE 6 ). Median sternal projection triangular and elongated with a well-rounded, rectangular tip ( Figs 5D, E View FIGURE 5 , 6A, B View FIGURE 6 ). Sternal process always far longer than coxite and telopodite, except for telopodite process. Coxite process weakly developed, broadly rounded mesally and barely visible behind massive sternite ( Fig. 6A, B View FIGURE 6 ). Telopodite mesally with a slender, apically tapering process ( Figs 5D, E View FIGURE 5 , 6A, B View FIGURE 6 ). Tip with a small, sharp-edged, retrorse process ( Fig. 6B View FIGURE 6 ).

Posterior gonopods in situ almost completely covered by coxite and telopodite of anterior gonopod. Coxite and telopodite of posterior gonopod clearly separated, with telopodite located at different level and angle than coxite ( Figs 5F, G View FIGURE 5 ). Sternite sclerotized and well-visible ( Figs 5G View FIGURE 5 , 6E View FIGURE 6 ). Coxite mesally with a single groove,protruding into a short stem towards telopodite. Telopodite longer than coxite, curved posteriorly ( Figs 5F, G View FIGURE 5 , 6 C–E View FIGURE 6 ). Telopodites arranged parallel to one another. A torsion present in telopodites, sperm canal discharging apico-laterally ( Fig. 5F, View FIGURE 5 G), telopodites resembling the letter ‘Z’. Telopodite in anterior view centrally with a ‘hole-like’ structure ( Fig. 6C View FIGURE 6 ), apex with four specific areas labelled a–d: (a) is a spinose membranous area, (b) the lateral opening of the sperm channel, (c) a membranous fringe below the apex and (d) a large membranous area located mesally ( Fig. 6C, D View FIGURE 6 ).

Distribution. Intermediate rain-dry forests ( Moat & Smith 2007) in Vohibasia, Isalo and Vohimena.

Intraspecific variation. The three populations at Vohibasia, Isalo and Vohimena differ from one another slightly in their size, ring number and gonopods. The population from Vohimena has 47 body rings, differs slightly in the colour pattern ( Fig. 9A, B View FIGURE 9 ), missing a coxal processes on male coxa 5 ( Fig. 9C View FIGURE 9 ), and in a completely red telson ( Fig. 9D View FIGURE 9 ). The anterior ( Fig. 9E, F View FIGURE 9 ) and posterior gonopods ( Fig. 9G, H View FIGURE 9 ) appear very similar to those of the type series from Vohibasia. Future studies should elucidate if these are three different species, like what was observed in the giant pill-millipede genus Zoosphaerium , where similar but distinct species can be found in Vohibasia, Isalo and Vohimena (Wesener 2009; Wesener & Anilkumar 2020).