Zoosphaerium silens, Wesener & Sagorny, 2021

Wesener, Thomas & Sagorny, Christina, 2021, Seven new giant pill-millipede species and numerous new records of the genus Zoosphaerium from Madagascar (Diplopoda, Sphaerotheriida, Arthrosphaeridae), European Journal of Taxonomy 758 (1), pp. 1-48 : 15-17

Zoosphaerium silens sp. nov.

urn:lsid:zoobank.org:act:2FA555CB-B805-401A-8730-6DFB6525C585

Figs 2B , 3 , 5B , 6

Diagnosis

The posterior telopods ( Fig. 6H–I ) identify Z. silens sp. nov. as a member of the Z. libidinosum speciesgroup. Zoosphaerium silens sp. nov. shares the absence of locking carinae with a number of spiny forest species. It differs from all other species except Z. libidinosum in the color of the tergites, the glabrous anal shield and the presence of at least two rows of very long endotergal bristles. Zoosphaerium silens sp. nov. differs from Z. libidinosum in the wider tarsus (3.5 versus 3.8 times as long as wide), the presence of only two rows of endotergal bristles (three rows in Z. libidinosum ) and the absence of a lateral triangular projection on the third podomere of the anterior telopods (present in Z. libidinosum ).

Z. silens sp. nov. differs by more than 14% uncorrected p-distance in the COI gene from Z. album and Z. libidinosum .

Etymology

‘Silens’ (= ‘quiet’), noun in apposition, after the reduced stridulation ribs in the male.

Material examined

Holotype MADAGASCAR – Toliara • ♂; Parc National de Kirindy Mite , 25.6 km SW of Belo sur Mer; 20°56.6′ S, 43°52.3′ E; alt. 10 m; dry deciduous forest; 9 Mar. 2007; V. Soarimalala leg.; coll. no. VS- 1348; FMNH-INS 3119887 .

Paratype MADAGASCAR – Toliara • ♀; same collection data as for holotype; FMNH-INS 3119887 .

Other material

MADAGASCAR – Toliara • 4 ♂♂; Rèserve Spéciale dʼAndranomena ; 20°10′31″ S, 44°28′25″ E; alt. 18 m; dry deciduous forest; 12 Mar. 2010; V. Soarimalala leg.; coll. no. VS-1815; FMNH-INS 3119875 • 1 ♂; same collection data as for preceding; ZFMK MYR11137 .

Description

BODY LENGTH. Largest female (paratype): length ca 27.2 mm, width of thoracic shield 14.3 mm, of tergite 8 14.8 mm (widest), height of thoracic shield 8.2 mm, of tergite 8 10.1 mm (highest).

COLORATION. Some discoloration may have occurred because of preservation in ethanol. Tergites dorsally orange to brown, especially at posterior margin, laterally green except for paratergite depressions which are yellow. Anal shield light brown to yellowish dorsally as well as posteriorly, laterally green. Thoracic shield green, but grooves and margins yellow-brownish ( Fig. 2B ). Head and antennae green, legs basally light brown, apically green.

HEAD. Wide and short. Eyes with>75 ommatidia. Aberrant ocellus located in antennal groove. Antennae short, with cylindrical joints, protruding posteriorly to leg pair 3. Length of antennomeres 1= 2=3= 4=5<6. A shallow groove present on antennomere 1. Male apical disc with 11 or 12 apical sensory cones. Organ of Tömösváry located in antennal groove.

GNATHOCHILARIUM AND MANDIBLE. Not dissected.

STIGMATIC PLATES. First plate triangular, apex well rounded, nearly as wide as at base. Mesal margin slightly curved towards coxa. Hairs most abundant on apical margin, very few hairs on basal and lateral margins ( Fig. 6B ).

PLEURITES. First pleurite weakly modified, slightly extending posteriorly. Other pleurites well-rounded.

COLLUM. Glabrous with very sparse setae around margins, mostly located at corners on either side of head.

THORACIC SHIELD. Smooth and glabrous, without protuberances.

TERGITES. Surface glabrous and matte, lacking small pits. Tips of paratergites of midbody tergites projecting posteriorly.

ENDOTERGUM. Inner section with numerous short triangular spines and very few longer setae. Middle area above spines with a single row of sparse elliptical cuticular impressions slightly varying in size. Apically two rows of dense marginal bristles, every second bristle strongly protruding above tergite margin ( Fig. 5B ). Bristles with numerous small spines.

ANAL SHIELD. Large and well-rounded. In both sexes glabrous. Underside lacking locking carinae.

LEGS. Leg 1 with 1 ventral spine, leg 2 with 1, leg 3 with 5 or 6. First two leg pairs without an apical spine, spine present on leg 3. Leg pairs 4–21 with 8–10 ventral spines and an apical spine. On leg 9, femur 1.7 and tarsus 3.5 times as long as wide. All podomeres with setae ( Fig. 6C ).

Male sexual characters

GONOPORE. Covered with a single undivided, rounded membranous plate, very wide, located on basal half of coxa ( Fig. 6A ).

ANTERIOR TELOPODS. Harp with two weak stridulation ribs ( Fig. 6E ). First podomere with numerous setae mainly at lateral margin, as wide as long. Process of second podomere as long as basal fifth of third podomere, not visible in anterior view, with apical mound of a few sclerotized spots juxtaposed to third podomere. Third podomere with an apical sclerotized spot and a lateral crenulated tooth, mesally with an elevated area carrying sclerotized spots ( Fig. 6D, F ); lower area carrying 4 spines ( Fig. 6D, F ). Second and third podomeres sparsely setose.

POSTERIOR TELOPODS.Movable finger weakly curved; hollowed-out inner margin with two non-sclerotized lobes and ca five smaller sclerotized spines, posterior aspect with ca 15 large crenulated teeth. Fixed finger wider than movable finger, with slightly curved tip; basally with single membranous lobe, on inner margin covered with a few sclerotized spots. Second and third podomeres lacking long hair, almost completely glabrous. First podomere glabrous except for a few setae at mesal margin.

Female sexual characters

Washboard with two short interrupted stridulation ribs on each half ( Fig. 6G ). Vulva covering more than ⅔ of coxa surface. Operculum large, ending before coxal margin. Apical margin of operculum wellrounded, reaching apicalmost point medially. Mesal plate reaching up to half of operculumʼs height ( Fig. 6J ).

Distribution and ecology

Zoosphaerium silens sp. nov. is currently known from the western dry forest of Kirindy-Mite as well as from the dry forest of Andranomena further north ( Fig. 3 ). These populations differ by an uncorrected p-distance of 2.8% ( Table 2 ).

Figures

Fig. 2. Habitus photographs of the seven new species of Zoosphaerium, lateral view. A. Zoosphaerium nigrum sp. nov., holotype (CASENT 9068289). B. Z. silens sp. nov., holotype (FMNH-INS 3119887). C. Z. ambatovaky sp. nov., holotype (CASENT 9068294/1).D. Z. beanka sp. nov., holotype (FMNH-INS 3119897). E. Z. voahangy sp. nov., holotype (FMNH-INS 3119921). F. Z. masoala sp. nov., holotype (FMNH-INS 3195651). G. Z. spinopiligerum sp. nov., holotype (FMNH-INS 3119885). Not to scale.

Fig. 3. Distribution map of the newly described species of Zoosphaerium. Vegetation color marks modified from Moat & Smith 2007. 1 = Z. nigrum sp. nov.; 2 = Z. silens sp. nov.; 3 = Z. ambatovaky sp. nov.; 4 = Z. beanka sp. nov.; 5 = Z. voahangy sp. nov.; 6 = Z. masoala sp. nov.; 7 = Z. spinopiligerum sp. nov. Numbers followed by ‘a’ mark additional, non-type localities.

Fig. 5. Scanning electron micrographs of the endoterga of midbody rings. A. Zoosphaerium nigrum sp. nov., holotype (CASENT 9068289). B. Z. silens sp. nov., holotype (FMNH-INS 3119887). C. Z. ambatovaky sp. nov., holotype (CASENT 9068294/1). D. Z. beanka sp. nov., holotype (FMNH- INS 3119897). E. Z. voahangy sp. nov., holotype (FMNH-INS 3119921). Scale bars = 100 µm.

Fig. 6. Zoosphaerium silens sp. nov., holotype (FMNH-INS 3119887). A. Left coxa 2 with gonopore, posterior view. B. Left coxa 1 with stigmatic plate, posterior view. C. Left leg 9, posterior view. D. Left anterior gonopod, posterior view. E. Left anterior gonopod, anterior view. F. Left anterior gonopod, lateral view. G. Female subanal plate with washboard. H. Right posterior telopod, posterior view. I. Right posterior telopod, anterior view. J. Left female coxa 2 with vulva, posterior view. Abbreviations: as = apical spine; cl = claw; cr-t = crenulated teeth; cx = coxa; ep = external plate; gp = gonopore; ip = inner plate; o = operculum; pref = prefemur; s-ps = sclerotized spots; sr =stridulation rib; st = stigmatic plate; syn = syncoxite; ta = tarsus; vs = ventral spines. Roman numerals indicate telopoditomeres. Scale bars = 1 mm.