Ostinobolus 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 : 86-89

Ostinobolus Wesener , gen. n.

urn:lsid:zoobank.org:act:1A0ECD32-48CB-4631-AE39-06263DF7EB87

Type species: Ostinobolus rufus sp. n.

Other species included: O. stellaris sp. n. O. montanus sp. n. O. subterraneus sp. n.

Diagnosis: the posterior gonopods of Ostinobolus with their apically swollen membranous area (v in Figs 48J , 50F , 51G , 52H) are unique among Spirobolida . Telopodites of anterior gonopod diverse, either inconspicuous ( Fig. 51F ), or on posterior side apically with a small, non-protruding process ( Fig. 48H ), or with a large retrorse process ( Fig. 52G ). Telopodites of posterior gonopod as wide as coxites, arranged face-to-face with one another. First leg pair longer than second ( Fig. 52A ). Living specimens roll themselves into a double-spiral when disturbed. Natural colour varies between species, red to brown ( Figs 48A, C , 52A, C ). Some Ostinobolus species share the habitus and the colour pattern with species of the sympatric living Alluviobolus . The latter, however, differs from the former in the presence of completely different anterior and posterior gonopods. Gnathochilarium with a subdivided mentum and a single sclerotized ledge on each stipites ( Figs 48E , 52D ), like in Flagellobolus , Riotintobolus , Pseudocentrobolus , Granitobolus , Caprobolus , Alluviobolus . Species of this genus share fewer characters on the anterior gonopods than other genera of Spirobolida . Especially the placement of the unusual O. subterraneus sp. n. inside Ostinobolus is tentative at best.

Distribution and ecology: species of Ostinobolus could be recorded with four species from the rain- and subhumid forests in Southeastern Madagascar ( Fig. 49 ). Most species are restricted to the rainforest and littoral rainforest with the exception of O. subterraneus sp. n. which also occurs in the semi-dry forest of Petriky. Specimens of O. rufus sp. n. were always collected on the soil surface, with juveniles feeding 1–2 cm deeper in the leaf litter. The same life style can be suggested for O. stellaris sp. n. and O. montanus sp. n., which share a similar colour pattern and leg length with O. rufus sp. n. O. subterraneus sp. n., however, differs from the other species of the genus in living deeply inside the root horizon of the soil.

Description. Males: length up to 53 mm, diameter up to 4.4 mm. 40–49 podous rings. Female length up to 65 mm, diameter up to 6.3 mm. 40–48 podous rings.

Colour highly species-specific, see species descriptions.

Head: each eye with circa 20–25 ocelli arranged in 4–6 vertical rows ( Figs 48A , 50A , 51A ). O. subterraneus sp. n. with only 6–8 decolorized and fused ocelli ( Fig. 52A ). Labrum with standard three irregular teeth and a row of 10–12 stout marginal setae. Clypeus with two setiferous foveolae on each side. Antennae of medium length, reaching back to ring 3–5 ( Fig. 51B ). Relative lengths of antennomeres: 1<<2=3=4=5<6

( Fig. 48A ). Terminal antennomere with four large sensory cones located together inside a membranous area. Antennomere 5 apically with four rows, antennomere 6 with two rows of sensilla basiconica.

Gnathochilarium unusual ( Fig. 48E ). Lamellae linguales each with two standard setae located behind one another. Stipites each with three apical setae. Mentum basally subdivided by a conspicuous suture ( Figs 48E , 52D ). Stipites towards mentum with a wide sclerotized ledge ( Fig. 48E ). Hypopharyngeal crest with a field of spine-like structures. Number of sensilla on central pads not counted.

Mandible: external tooth simple, rounded; mesal tooth with three cusps. Six pectinate lamellae. Molar plate with few (6 or 7) transverse furrows, anterior three furrows enlarged, posterior furrows minute.

Collum: smooth, laterally not protruding as far as body ring 2 ( Fig. 48A ).

Body rings: dorsally and laterally smooth, meso- and metazona ventrally with numerous transverse impressions. Ozopores starting at ring 6, touching suture between mesozona and metazona ( Fig. 48C ).

Telson: preanal process absent. Anal valves with neither lips, nor grooves, nor micropunctation, but posteriorly elongated. Subanal scale inconspicuous ( Figs 48D , 50C , 51C ).

Legs: coxae 1 and 2 elongated and fused with sternum, podomeres from prefemur to tarsus in both sexes each with 4–10 ventral/mesal setae. First leg pair longer than second ( Fig. 52A ). Tarsus 2 with only small claw, but 3–6 ventral spines. Length of midbody legs (with exception of O. subterraneus where leg length is reduced) circa 1.2 times body diameter in males ( Fig. 48F ) and 0.8 times body diameter in females. Each podomere with an apical, ventral seta. Coxae 3 and beyond of cylindrical shape ( Fig. 48F ). Tarsus with a stout dorso-apical seta and five pairs of ventral setae.

Male sexual characters: coxae 3 and 4 in some species elongated into short cylindrical cone ( Figs 48B , 51B ).

Anterior gonopods: median sternal projection triangular, with a wide, well-rounded tip ( Fig. 48G ). Sternite in most species longer than coxite. Coxite without a process, in anterior view well-visible, in posterior view only laterally present ( Figs 48H , 51F ). Telopodite diverse inside the genus, see species-specific descriptions.

Posterior gonopods in situ almost completely covered by anterior gonopod coxite and telopodite. Posterior gonopods coxite and telopodite completely fused, but suture partly visible ( Fig. 48J ). Sternite sclerotized and well-visible ( Fig. 48J ). Coxite protruding into a short stem towards telopodite, basally with a single spermatic groove. Telopodite as long and as wide as coxite ( Fig. 48J ), the former arranged face-to-face with one another. Shape of telopodite species-specific, but apically always with a large, swollen membranous area (v in Figs 48J , 50F , 51G , 52H). Sperm canal discharging mesally, basal to membranous area (w in Figs 48J , 50F , 51G , 52H).

Female sexual characters: vulva simple, bivalve-like, with a small, poorly sclerotized operculum at base. Posterior valve apically overlapping anterior one, both smooth, sensory cones absent. Towards opening, basally on each valve are two or three rows of setae.

Etymology: Ostinobolus , masculine, consists of Ostino - referring to the superficial resemblance of the posterior gonopods to a human femur bone, and -bolus.

Figures

Figure 48. Ostinobolus rufus sp. n., A, B, D, G–J male holotype; C, E, F male paratype. A head, lateral view B legs 1–7, ventral view C living specimen D telson E gnathochilarium F midbody ring with leg G anterior gonopod, anterior view H anterior gonopod, posterior view I left posterior gonopod, anterior view Į left posterior gonopod, posterior view. Apo = apodeme; av = anal valves; Co = collum; Cx = coxite; Gn = gnathochilarium; L = ledge; Md = mandible; Pre = preanal ring; St = sternite; sub = subanal scale; T = telopodite. Scale bars = 1 mm.

Figure 49. Distribution map of the genus Ostinobolus gen. n..

Figure 50. Ostinobolus stellaris sp. n., male holotype. A head, lateral view B legs 1–7, ventral view C telson D anterior gonopod, anterior view E right posterior gonopod, anterior view; F: right posterior gonopod, posterior view. av = anal valves; Co = collum; Cx = coxite; Gn = gnathochilarium; h = head; IL = incisura lateralis; L = ledge; Md = mandible; Pre = preanal ring; St = sternite; sub = subanal scale; T = telopodite. Scale bars = 1 mm.

Figure 51. Ostinobolus montanus sp. n., male holotype. A head, lateral view B legs 1–7, ventral view C telson D anterior gonopod, anterior view E right posterior gonopod, anterior view F anterior gonopod, posterior view G right posterior gonopod, posterior view. av = anal valves Co = collum; Cx = coxite; Gn = gnathochilarium; Md = mandible; Pre = preanal ring; St = sternite; T = telopodite. Scale bars = 1 mm.

Figure 52. Ostinobolus subterraneus sp. n., male holotype. A head, lateral view B legs 1–7, ventral view C telson D gnathochilarium, ventral view E anterior gonopod, anterior view F right posterior gonopod, anterior view G anterior gonopod, posterior view H right posterior gonopod, posterior view. av = anal valves; Co = collum; Cx = coxite; E = reduced eye; Gn = gnathochilarium; L = ledge; Md = mandible; Pre = preanal ring; St = sternite; T = telopodite. Scale bars = 1 mm.