Moojenodesmus schubarti Golovatch & Gallo, 2022

Golovatch, Sergei I., Gallo, Jéssica S. & Bichuette, Maria E., 2022, Two new species of the millipede family Trichopolydesmidae from Bahia state northeastern Brazil, including a remarkable threatened troglobiont (Diplopoda, Polydesmida), Zootaxa 5115 (3), pp. 419-437 : 432-433

Moojenodesmus schubarti Golovatch & Gallo , sp. nov.

Figs 11 & 12

Material examined. Holotype male ( LES 0027864 ), Brazil, Bahia State, Iuiu Municipality, near Lapa do Baixão , epigean, S14°26’07.4”, W43°37’27.6”, 8.XII.2013, M. E. Bichuette & J. E. Gallão leg.

Paratypes: 1 male ( ZMUM) , 1 female (LES 0027865) , same locality, taken together with holotype .

Name. To honour Otto Schubart (1900–1962), one of the leading specialists in the systematics of Diplopoda of the time globally, Nestor of diplopodology in Brazil, and the author of the genus. Being resident of Brazil since 1933, he made particularly numerous and profound contributions to the millipede fauna of that country ( Lindner et al. 2012).

Diagnosis. Differs from congeners by 20 body rings in both sexes, the presence of a strong median hump (h) above the antennae on the male head, coupled with a particularly simple gonopodal telopodite divided into two parts only: a prominent, rounded and slightly higher lateral lobe (= exomere, ex) and a barely discernible mesal solenomere (sl) ( Fig. 12B, D ).

Description. Length ca 3.5 mm (male holo- and paratype) or 3.8 mm (female paratype), width of midbody pro- and metazonae 0.7 and 0.8 mm (male, female), respectively. Coloration entirely pallid ( Fig. 11 ).

Body with 20 rings (male, female). Tegument mainly dull, at most slightly shining, texture very delicately alveolate and scaly. Head densely pilose throughout; epicranial suture faint; isthmus between antennae ca 1.2 times broader than antennal socket ( Fig. 11C ). A strong, median, rounded, bare hump (h) above antennae on male head ( Fig. 11B ), but female head regularly convex, not modified. Antennae very short, strongly clavate due to a considerably enlarged antennomere 6, slightly produced past ring 2 (male) or collum (female) dorsally; in length, antennomere 6> 2 = 3 = 5> 4> 7> 1 ( Figs 11A–C ); antennomere 6 with a large, compact, roundish, distodorsal group of bacilliform sensilla; a smaller distodorsal group of similar, but shorter sensilla present also on antennomere 5; a few minute distodorsal sensilla discernible on antennomere 4 as well ( Fig. 11A–C ). Genae regularly rounded ( Fig. 11A, C ), gnathochilarium without peculiarities.

In width, collum = ring 3 <2 = 4 <5(6) = 14(15) <head; body gradually tapering towards telson on segments 16–20 ( Figs 11D–F ). Paraterga moderately developed, starting with collum, mostly clearly declivous, set high at about upper third of metazonae and always lying below a regularly convex dorsum, with squarish to narrowly rounded shoulders frontally, faintly and regularly rounded sides, and narrowly rounded caudal corners ( Fig. 11 ); the latter never pointed and always lying within rear tergal margin. Lateral margin of postcollum paraterga with two or three small setigerous indentations and a seta at caudal corner. Pore formula normal, ozopores inconspicuous, round, located laterally in front of caudalmost incision ( Fig. 11D, E ). Collum and following metaterga with regular, mostly subclavate, medium-sized to rather long setae borne on minute knobs, these knobs being arranged in three transverse rows typical of most polydesmoids; polygonal bosses missing ( Fig. 11D ). Stricture between pro- and metazonae wide, shallow and smooth. Limbus very thin, very faintly microdenticulate, nearly smooth. Pleurosternal carinae absent ( Fig. 11B, C ). Epiproct short, conical, directed caudoventrally, tip subtruncate; pre-apical papillae small ( Fig. 11D–F ). Hypoproct trapeziform, setiferous papillae at caudal corners evident, rather well separated; sides slightly concave.

Sterna broad, without modifications, poorly setose ( Fig. 11C, F ). Epigynal ridge very low. Legs moderately long and slender ( Fig. 11 ), ca 1.2–1.3 times as long as midbody height (male, female); tarsi especially long and slender, claw very short; sphaerotrichomes missing ( Fig. 12A ). Gonapophyses on male coxae 2 vestigial.

Gonopod aperture subcordiform, broader than male prozona 7. Gonopods ( Fig. 12B–D ) rather simple, coxites very large, subglobose, sparsely setose laterally, cannulae typical hollow tubes; telopodites sunken deep inside a prominent gonocoel, apical parts being barely exposed; each telopodite indistinctly biramous, strongly curved caudad; prefemoral (= densely setose) parts short and held subtransversely to main body axis, but acropodites lying parallel to each other; telopodite consisting of a very short solenomere (sl) lying mesal to a prominent, round, lobe-shaped exomere (ex).

Remarks. This species is a typical, very small, epigean Moojenodesmus , the first to be recorded from Bahia. Like some of its congeners, this new species is amongst the smallest Polydesmida on Earth. Thus, the relatively widespread, eurytopic, apparently mass and at least partly parthenogeneric M. pumilus Schubart, 1944 is only ca 2.0–2.2 (male) to 2.1–3.2 (female) mm long and has 19 (male) or 20 (female) body rings ( Golovatch 1992). Furthermore, based on the gonopodal conformation alone, M. pumilus fails to differ from M. pygmaeus Schubart, 1945 , the type species that seems to be bisexual and has only 18 body rings in both sexes ( Schubart 1944, 1945; Golovatch 1992). The situation thus strongly resembles that concerning another minute polydesmidan, Ammodesmus congoensis VandenSpiegel & Golovatch, 2015, a tiny member of the Afrotropical family Ammodesmidae , superfamily Pyrgodesmoidea , which is only 1.5–2.1 mm long and has either 18 or 19 body rings in both sexes ( VandenSpiegel & Golovatch 2015). This suggests that either Moojenodesmus pygmaeus and M. pumilus are indeed different species distinguished morphologically only through a lesser number of body rings in the former species or, this being not less likely now, both actually represent a single species, M. pumilus by priority, that shows intraspecific variations in body segment counts like those already confirmed in Ammodesmus congoensis. Further studies are necessary, especially molecular-based ones, to solve the riddle. Whether such variations are related to body miniaturization or parthenogenesis, or both, is likewise open to question yet.

Figures

FIGURE 11. Moojenodesmus schubarti sp. nov., male paratype. A–C. Anterior part of body, dorsal, lateral and ventral views, respectively. D–F. Posterior half of body, dorsal, lateral and ventral views, respectively. Abbreviation: h, hump. Photographs by K.V. Makarov, taken not to scale.

FIGURE 12. Moojenodesmus schubarti sp. nov., male paratype. A. Leg 9, lateral view. B. Right gonopod, posterior view. C & D. Left gonopod, mesal and lateral views, respectively. Scale bars: 0.2 mm (A) and 0.1 mm (B–D). Abbreviations: ex, exomere; sl, solenomere.