Zoosphaerium minutus Sagorny & Wesener

Sagorny, Christina & Wesener, Thomas, 2017, Two new giant pill-millipede species of the genus Zoosphaerium endemic to the Bemanevika area in northern Madagascar (Diplopoda, Sphaerotheriida, Arthrosphaeridae), Zootaxa 4263 (2), pp. 273-294 : 284-289

Zoosphaerium minutus Sagorny & Wesener , n. sp.

Figs 8–11

Etymology. minutus , noun in apposition, referring to the small size of this species, which is the smallest known Zoosphaerium species, being of similar size to individuals of Microsphaerotherium .

Material examined. Holotype: 1 M, FMNH-INS 2858686-A ( FMNH), Madagascar: Mahajanga, Sofia, Amberivery Forest , Paysage Harmonieux Protégé de Bemanevika , site 2, 14°20'47.3''S, 48°34'47.3''E, 1570 m, Slightly disturbed montane forest, Pitfalls PF #5, coll. Steven M. Goodman and Toky Randriamora, Oct-2013 . Paratype: 1 M, ZFMK MYR 6143 , same data as holotype.

Other material examined: 1 M, FMNH-INS 2858676, Madagascar: Mahajanga, Sofia, Along trail to Matsaborimena , Paysage Harmonieux Protégé de Bemanevika , site 1, 14°20'26.7''S, 48°35'08.3''E, 1620 m, Slightly disturbed montane forest, pitfalls, PF#2, coll. Steven M. Goodman and Toky Randriamora, Oct-2013.

Diagnosis. Zoosphaerium minutus n. sp. differs from similar sized species of the genus Microsphaerotherium clearly in the presence of two locking carinae on each side of the anal shield ( Microsphaerotherium species only have one elongated carina on each side). The unusual posterior telopods of Z. minutus n. sp. make it challenging to assign it to existing species-groups ( Figs 10 G, H). Neither does the species share similarities in the posterior telopods with those species currently not assigned to any species-group ( Table 1 ). Zoosphaerium minutus n. sp. differs from those five species in most aspects, like the number of stridulation ribs (only one in Z. darthvaderi Wesener & Bespalova, 2010 , Z. analavelona Wesener, 2009 and Z. fisheri Wesener, 2009 ), or the number of apical cones (only four in Z. analavelona and Z. fisheri ).

Description. Body length: holotype male (largest): length 17.9, width of thoracic shield 8.8 (=widest), height of thoracic shield 5.1 (=highest).

Coloration: some discoloration may have occurred because of preservation in ethanol. Tergites brown to olive with a slightly darker rim at posterior edge of tergite. Anal shield uniform solid light-brown color, lighter than and conspicuously contrasting tergites. Collum and thoracic shield darker brown in color than other tergites. Head and antennae green, legs light-brown with green apical segments.

Head: wide and short ( Fig. 9 A). Eyes with 65–70 ocelli ( Fig. 9 B). Antennae protruding posteriorly to leg pair 4. Size of antennomeres 1>2=3<4=5<6 ( Fig. 9 D). Base of antennomeres 1–3 with small sclerotized teeth, protuberant on antennomere 1. First antennomere with shallow groove and one apical row of sensilla basiconica ( Fig. 9 F). Few larger setae present on antennomeres 1–5, antennomere 6 with numerous long setae and single row of sensilla basiconica surrounding apical disc. Male apical disc with 9/16 apical sensory cones ( Fig. 9 E). Organ of Tömösváry a small, elliptical pit located laterally in antennal groove ( Fig. 9 C).

Gnathochilarium: typical of the order ( Figs 10 A–E). Stipites located laterally to lamellae linguales, bearing numerous long setae ( Fig. 10 C). Setae also present on paramentum but absent at center of lamellae linguales ( Fig. 10 C). Central pads apically protruding from lamellae linguales, with a median triangular incision on each pad.

Posterior half of underside with single field of large sensory cones interspersed with longer, slimmer structures ( Fig. 10 B). Inner palpi protruding to medial side of gnathochilarium ( Fig. 10 A), bearing single field of sensory cones ( Fig.10 D). Rudimentary lateral palpi sharing a common well-developed base bearing four sensory cones ( Fig. 10 E). Hypopharynx with single row of marginal teeth.

Mandible: with the typical shape of the order Sphaerotheriida , condylus with sharp groove at apex, inner tooth 3-combed, with 5 or 6 pectinate lamellae ( Fig. 10 F).

Stigmatic plates: first plate triangular, apex well rounded. Few hairs limited to apical side of plate ( Fig. 8 A).

Pleurites: first pleurite laterally modified and extending backwards with a broad, apically rounded process.

Collum: mainly glabrous, a few setae at margins.

Thoracic shield: smooth and glabrous.

Tergites: surface glabrous and shiny, lacking small pits. Tips of paratergites of midbody tergites projecting posteriorly.

Endotergum: inner section with few long setae and several short triangular spines. Between inner area and row of setae with single row of sparse large elliptical, cuticular impressions. Apically a single, relatively dense row of short marginal bristles ( Fig. 11 A). Bristles reaching 1/2 to 2/3 the way towards tergite margin, each bristle with numerous small spines ( Fig. 11 B).

Anal Shield: large and well rounded. No setae on anal shield, but with numerous small pits. Underside carrying two black locking carinae on each side, posterior one 4–5 times longer than anterior one, both located close to margin of anal shield.

Legs: leg 1 with 4 ventral spines, leg 2 with 6, leg 3 with 7–9. First two leg pairs without an apical spine. Leg pairs 4–21 with 8 or 9 ventral spines and an apical spine. In leg 9 femur 2.0, tarsus 5.1 times longer than wide. All podomeres with only few setae ( Fig. 8 B).

Females unknown.

Male sexual characters: gonopore covered with a single undivided, elliptical sclerotized plate. Apical portion of plate membranous. Few setae on sclerotized plate ( Fig. 8 C).

Anterior telopods: harp carrying two stridulation ribs. Lateral rib shorter and more pronounced than mesal rib ( Fig. 8 D). Process of second podomere nearly as long as third podomere. Apical margin of process of second podomere facing third podomere mostly covered with a mound of few sclerotized spots. A sclerotized spine occurs at base of process below field of spots. Third podomere large, with a slight lateral projection. Large mound of sclerotized spots facing second podomere ( Fig. 8 E); two sclerotized spines in depression lateral to mound. Lateral apical margin with 6 sclerotized, crenulated teeth and 2 or 3 sclerotized spines ( Fig. 8 F). A triangular sclerotized structure is present on apex of third podomere.

Posterior telopods: movable finger rather elongated (3.9 times longer than wide), weakly curving towards and slightly longer than immovable finger. Shallow meso-apical cavity of movable finger with five sclerotized spines, three positioned apically (one positioned below pair of apical spines) and two in center of cavity. Posterior aspect with ca. 20 tiny crenulated teeth ( Fig. 8 H). Additional sclerotized spine at center of movable finger. Immovable finger slender (4.9 times longer than wide), weakly curving towards podomere 3. Base of immovable finger with one sclerotized spine ( Fig. 8 G). Podomere 1 with no setae, podomere 2 only with few setae on margin of anterior side, posterior side covered by hair except for apical part of finger. Podomere 3 with marginal setae not extending to tip of finger.

Distribution and ecology. Zoosphaerium minutus is currently only known from two collection sites in patches of mountainous rainforest in Bemanevika ( Fig. 13 ), Madagascar, where it occurs sympatrically with Z. bemanevika n. sp. ( Fig. 1 ).

Figures

FIGURE 1. Distribution map of Zoosphaerium species in Madagascar, including Zoosphaerium bemanevika n. sp., and Zoosphaerium minutus n. sp. Red points refer to other Zoosphaerium species (See Table 1). Circles refer to clades (see Figure 12). Vegetation mapped after literature (DuPuy & Moat 2007).

FIGURE 8. Zoosphaerium minutus n. sp., holotype (FMNH-INS 2858686 - A); A: coxa of first left leg with first stigmatic plate; B: 9 th left leg; C coxa of second left leg with gonopore; D: left anterior telopod, anterior view; E: left anterior telopod, posterior view; F: left anterior telopod, lateral view G: left posterior telopod, posterior view; H: left posterior telopod, anterior view. Abbreviations: as = apical spine; cl = claw; cr-t = crenulated teeth; cx = coxa; fe = femur; gp = gonopore; pof = postfemur; pref = prefemur; s-ps = field of sclerotized spots; sr = stridulation ribs; st = stigmatic plate; syn = syncoxite; ta = tarsus; ti = tibia; vs = ventral spines. Scale bars = 0.5 mm.

FIGURE 9. Zoosphaerium minutus n. sp., holotype (FMNH-INS 2858686 - A), SEM, A: head, frontal view; B: ocelli; C: organ of Tömösváry; D: left antenna, lateral view; E: left antenna, apical disc with sensory cones; F: left antenna, antennomere 1 with sensilla basiconica and sclerotized teeth. Abbreviations: aD = apical disc; aG = antennal groove; sb = sensilla basiconica; TO = Organ of Tömösváry.

FIGURE 10. Zoosphaerium minutus n. sp., holotype (FMNH-INS 2858686 - A), SEM, A: gnathochilarium, apical view of dorsal side; B: gnathochilarium, sensory cones on inner palpus; C: gnathochilarium, ventral view; D: gnathochilarium, inner palpus and central pad; E: gnathochilarium, rudimentary lateral palpus with sensory cones mesal view; F: left mandible, mesal view. Abbreviations: c = condyles; cp = central pad; eT = external tooth; Hyp = Hypopharynx; ip = inner palpus; iT = internal tooth; LL = lamellae linguales; LP = lateral palpus; mp = molar plate; pL = pectinate lamellae; St = stipites.

FIGURE 11. Zoosphaerium minutus n. sp., holotype (FMNH-INS 2858686 - A), endotergum of mid-body tergite, SEM, A: ventral view; B: bristles on apical margin.

FIGURE 13. Habitat of Zoosphaerium bemanevika n. sp. and Zoosphaerium minutus n. sp. in patches of mountainous rainforest in the Paysage Harmonieux Protégé de Bemanevika. Surroundings of remaining rainforest are prone to habitat destruction and deforestation. A: shows the grazing of Zebu cattle in the surrounding pseudosteppe; B: indicating the destruction of forest edges due to the yearly burning of the pseudosteppe. Each fire lets the forest fragments shrink a few meters in diameter. Photos are the courtesy of Achille P. Raselimanana.