Simplomeris montivaga (Faës, 1902)

Wesener, Thomas, 2022, Integrative redescription of the enigmatic monotypic alpine pill millipede genus Simplomeris Verhoeff, 1936 (Glomerida, Glomeridae, Haploglomerinae), Zootaxa 5200 (6), pp. 550-564 : 555-559

Simplomeris montivaga (Faës, 1902)

Glomeris montivaga Faës, 1902a: 256 (original description)

Glomeris montivaga — Faës 1902b: 69 (also original description)

Onychoglomeris montivaga — Verhoeff 1906: 207 (key)

Haploglomeris (Simplomeris) montivaga — Verhoeff 1936: 223 (redescription)

Haploglomeris montivaga — Moritz & Fischer 1974: 362 (list)

Haploglomeris montivaga — Pedroli-Christen 1992: 402 (list, new locality)

Haploglomeris (Simplomeris) montivaga — Pedroli-Christen 1993: 59 (list)

Haploglomeris montivagus (sic!) — Beron 2008: 101 (list)

Simplomeris montivaga — Kime & Enghoff 2011: 107 (map, list)

Simplomeris montivaga — Oeyen & Wesener 2018: 8 (phylogeny, morphology)

Simplomeris montivaga var. montivaga Verhoeff, 1936: 225 new synonymy

Simplomeris montivaga var. simplonensis Verhoeff, 1936: 225 new synonymy

Simplomeris montivaga var. berisalensis Verhoeff, 1936: 225 new synonymy

Material examined (2 ♂♂, 4 ♀♀):

Topotypic material: 1 ♂, ZFMK MYR2626 , Switzerland, Wallis, Simplonpass , 750 m east of Hospiz, stream valley with Erico-Rhododendretum, with stones overgrown by Rhododendron ; 46°14'50.46''N, 8°2'19.88''E, 2130 m, leg. 23.vi.2014; 1 ♀, ZFMK MYR2625 , same data as previous; 1 ♀, ZFMK MYR2627 , same data as previous.

Other material examined: 1 ♂, ZFMK MYR2622 , Switzerland, Wallis, Riederalp , east of Riederfurka, overgrown rocks and under dead wood, 46°22'57.19''N, 8°1'20.45''E, 2170 m, leg. 22.vi.2014 ; 1 ♀, ZFMK MYR2623 , same data as previous ; 1 ♀, ZFMK MYR2624 , same data as previous .

Redescription:

Re-diagnosis: Medium-sized (8–12 mm), colourful ( Fig. 2A–D ) pill millipede species. S. montivaga shares the lack of a main stria crossing the thoracic shield dorsally with the species of the Glomeris klugii species group. S. montivaga lacks anterior stria (but has 3–5 posterior striae), of which at least 1 is usually present in species of the G. klugii species- group ( Hoess 2000). S. montivaga shares telopods lacking a trichostele as well as the telopoditomere 3 and 4 being elongated only with species of the subfamily Haploglomerinae , especially the only species of the genus Haploglomeris , H. multistriata . S. montivaga differs from H. multistriata in the number of striae of the thoracic shield (3–5 in S. montivaga vs.> 10 in H. multistriata ), as well as in the shape of the telopod: S. montivaga lacks any trichostele, while H. multistriata carries a short one on telopoditomere 1. S. montivaga carries on telopoditomere 2 a very wide process which reaches telopoditomere 4, while H. multistriata carries a slender triangular process which barely reaches the mid-length of telopoditomere 3. S. montivaga is in the mitochondrial COI gene close (4.9–6.1%) to G. primordialis , a similarity not at all reflected in their telopod morphology, body size or coloration.

Re-description (based on topotypic male and female)

Measurements: male length ca. 8 mm (broken), width of thoracic shield 3.1 mm, height of thoracic shield 1.7 mm. Female length ca. 11 mm, width of thoracic shield 5 mm, height of thoracic shield 2.7 mm.

General coloration (living specimens) head, legs and antennae blackish-brown. Collum brownish, posterior margin lighter, almost yellow. Thoracic shield and tergites basic colour blackish-brown, posterior margin light grey (duplicature). Thoracic shield anterior margin and inside schisma brightly yellowish, laterally with triangular orange spot above schisma, with narrow point of triangle located dorsally ( Fig. 2 ). Thoracic shield and tergites dorsally with two irregular orange spots, spots neither touching anterior nor posterior margin. Tergites laterally with a weaker, much smaller spot. In some species a third yellow spot is present, spots generally larger (see intraspecific variation below).Anal shield blackish brown, posterior half with a single large orange spot ( Fig. 2B ). Blackish-brown area with a triangular projection, projection not reaching anal shield margin. When specimen is rolled-up (defence behaviour), the two irregular red spots are located in the posterior half of the tergite, with two light depigmented spots becoming visible ( Fig. 2A ) at the anterior margin (covered by the preceding tergite when the specimen is walking).

Head sparsely covered with minute setae, especially anteriorly,>6 supralabral setae ( Fig. 3A ). Incisura lateralis (IL) directed slightly laterad, reaching neither height of organ of Tömösváry (TO) nor antennal basis ( Fig. 3A ). A furrow running laterally between ventral-most ocellus and TO, circumventing antennal fossa and terminating at height of IL ( Fig. 3A ). Labrum wide, with 7 marginal setae ( Fig. 3A ). Central labral tooth not projecting beyond lateral margin. Ocellaria black, 6 or 7+1 convex lenses ( Fig. 3A ). Antennae with disk four apical cones ( Fig. 3B ). Antennomere 3 approximately as long as 1 and 2 combined ( Fig. 3B ). Antennomere 6 by far the longest, approximately 2 times longer than wide. Antennomeres 1 and 2 only sparely setose, 3rd–7th more densely setose. Multiple sensilla basiconica on proximal apical edge of antennomeres 6 and 7 ( Fig. 3C ), 2 at 6th and 5 at 7th ( Fig. 3C ). Organ of Tömösváry like typical for the order, U-shaped ( Fig. 3A ), 1.6 times longer than wide. Bulging cone and slit margins smooth. No internal structures visible in SEM. Gnathochilarium typical for the order, cardines large. Lamellae linguales ventrally recessed. Stipites and lamellae linguales densely setose, apically stipites with 4 or 5 longer setae, lamellae linguales with a pair of longer setae ( Fig. 3D ). Inner palpi significantly larger than lateral palpi ( Fig. 3D ). Inner palpi with>30 sensory cones standing in single field ( Fig. 3E ). Lateral palpi with a field of 6–8 sensory cones ( Fig. 3E ). Endochilarium with large anterior membranous paramedian lobes, densely covered with cuticular scales ( Fig. 3E ). Central pads each with single cluster of 20–30 sensilla directed towards median furrow ( Fig. 3E ). Mandible information already published in Oeyen & Wesener (2018); with single large outer tooth and four-combed inner tooth. Six rows of pectinate lamellae. Lateral areas of intermediate area covered with small cuticular scales. Molar plate rectangular, with anterior depression and a weak membranous fringe. Condylus pronounced.

Collum with two continuous anterior striae ( Fig. 3F ). At low magnification glabrous, under SEM sparsely covered with minute setae, recessed into small pits.

Thoracic shield with wide schism located at posterior corner ( Fig. 3G ). No main or posterior striae, anterior striae 4, with the anterior-most one being longest ( Fig. 4A ). Marginal furrow widest laterally, narrowing medially ( Fig. 4B ). At low magnification glabrous, under SEM uniformly covered with minute recessed setae.

Tergites 3–11 covered with minute recessed setae, with single complete transverse anterior stria and short lateral striae anteriorly circumventing a depression. Lateral edges not projecting posteriorly.

Ozopore simple, without special sutures or other structures.

Anal shield dorsally evenly covered with minute setae and without any special notches or structures.

Legs. First leg pair coxae with large mesal elongation protruding up to anterior half of prefemur carrying two spines at well-rounded apex ( Fig. 4C ). First tarsus with single apical spine, 4 dorsal spines and 6 ventral spines. Leg pair 2 with much weaker mesal coxal process, coxal process carrying two large spines ( Fig. 4D, E ). Second tarsus with single apical spine, 6 dorsal spines and 13 ventral spines, shape of podomeres resembling those of following legs.

Midbody legs sparely covered with setae ( Fig. 4F ). Coxa almost triangular, much wider at base than apically. Coxa mesally elongated in short, well-rounded process. Tibia, pre- and postfemur apically with a single mesal spine, prefemur and tibia apically with 1 or 2 lateral spines ( Fig. 4F ). Femur almost 3 times longer than wide. Tarsus with single apical, 5 dorsal and 9–13 ventral spines. Tarsus 5 times longer than wide. Claw elongated.

Male sexual characters. Male anal shield lacking special structures. Male gonopore clam-shaped and mesally protruding from posterior side of coxa 2 ( Fig. 4E ). Single elongate membranous opening surrounded by 3 or 4 apical and two large basal setae. No division into separate plates ( Fig. 4E ).

Male leg 17 reduced with 4 podomeres ( Fig. 5A ). Coxae fused with stigmatic plates, mesally with small medial process bearing a sub-apical spine. Podomere 1 with mesal spine. Second podomere approximately slightly wider than podomere 3 and twice as long as podomere 1. Podomere 3 very short and inconspicuous. Podomere 4 with subapical spine and 6 or 7 ventral spines. Complete leg sparsely covered with minute setae.

Male leg 18 reduced, but to a lesser extent than leg-pair 17 ( Fig. 5B ). Coxae without widened coxal lobe and not fused to a syncoxite. Small mesal coxal process with single subapical spine. Single, well-developed medial spine on podomere 1. Podomere 2 slightly wider than podomere 3 and more than twice as long as podomere 1. Podomere 3 very short, no spines. Podomere 4 slightly longer and narrower than podomere 2, with apical spine.

Telopod (male leg 19) stout, syncoxite likewise ( Fig. 5D ). Inner lobe conspicuous, glabrous, wide and rounded, almost projecting as far as horns. Inner horns with numerous hairs of varying length at mesal margin, a subapical spine, which is curved almost 90° mesally but not well-developed ( Fig. 5D ). Telopoditomere 1 with mesal bulging process, rectangular ( Fig. 5C ). Telopoditomere 2 mesally elongated into large bulbous process (immovable finger) with knobbed proximal surface. Process projecting as far as telopoditomere 4 ( Fig. 5C ). Telopoditomere 3 as long as telopoditomere 2, but much slenderer, in posterior view towards process with knobbed surface ( Fig. 5E ). Telopoditomere 4 slender, slightly curved, almost as long as telopoditomere 3 ( Fig. 5C ) In posterior view with field of knobs juxtaposed to process of telopoditomere 2, apically with a posteriorly oriented spine. Telopoditomeres 3 and 4 forms chela (pincer) against medial process of second telopoditomere.

Female sexual characters. Anal shield slightly rounder than in males. Vulvae large, attached to posterior side of coxae 2 via membranes; ventrally with symmetrical mesal and lateral plates. Lateral plate overlaps mesal one apically on posterior side, but both are fused together at their base via a membranous connection. Operculum recessed between vulval plates.

Intraspecific variation. Not enough samples are present to describe morphological variation in great detail, but according to the specimens observed, as well as the literature, the number of striae on the thoracic shield seems to vary between three and five. Both populations differ slightly genetically, 0.2% (Supplemental Material). Verhoeff (1936) distinguished three colour varieties from the same population he studied: var. montivaga (the most common one, Fig. 1A–D ), var. simplonensis , in which the yellow spots on the tergites are larger as well as one more row is visible (similar to G. hexasticha ), and var. berisalensis which is identical to var. montivaga but with a continuous yellow-orange band on the thoracic shield. Glomeridae species are known to be colour variable ( Schubart 1934; Hoess & Scholl 1999; Wesener & Conrad 2016; Reip & Wesener 2018). Considering that Verhoeff (1936) found all three varieties in a single population they are here viewed as colour morphs without any taxonomic status.According to the Zoological Code of Nomenclature §45.6.4 variety names published before 1961 are viewed as subspecific names, making it necessary here to formally synonymize the three varieties. Such a synonymy is confirmed by our molecular results, as our two samples from Riedafurka contain both the var. simplonensis and the var. montivaga colour morph with no genetic differences.

Ecology. At both localities S. montivaga was found in syntopy to more numerous G. transalpina ( Fig. 1A ). G. transalpina , while restricted to the southwestern Alps, is nevertheless much more widespread than S. montivaga ( Kime & Enghoff 2011) .

Figures

FIGURE 1. Maximum likelihood tree. The evolutionary history was inferred by using the maximum likelihood method based on the selected Hasegawa-Kishino-Yano model (Hasegawa et al. 1985). The tree with the highest log likelihood (-5194.2969) is shown. Numbers above nodes refer to bootstrap values (1000 replicates). Grey boxes mark species of the genera Haploglomeris Verhoeff, 1906 and Onychoglomeris Verhoeff, 1906 Blue box marks Simplomeris, the yellow box marks the Glomeris klugii species-group.

FIGURE 2. Living specimens of Simplomeris montivaga (Faës, 1902) and the sympatric Glomeris transalpina Koch, 1836, topotype locality at Simplon. A. Glomeris transalpina Koch, 1836 (left) and S. montivaga (right), rolled up. B–D. Simplomeris montivaga, walking. Not to scale, but S. montivaga specimens are approximately 8 mm long. Photos courtesy of Jan-Philip Oeyen.

FIGURE 3. Simplomeris montivaga (Faës, 1902), topotype male (ZFMK MYR2626), scanning electron micrographs. A. Head, frontal view. B. Left antenna, lateral view. C. Antennomeres 6, 7 and disc, lateral view. D. Gnathochilarium, ventral view. E. Gnathochilarium, inner side with endochilarium. F. Collum (tergite 1), dorsal view. G. Thoracic shield (tergite 2), anterior view. Abbreviations: Ca = cardines; ch = schisma; d = antennal disc; cP = central pads; Gu = gula; IL = incisura lateralis; iP = inner palpus; la = labrum; LL = lamellae lunguales; LP = lateral palpus; ma = marginal brim; Me = mentum; O = ommatidia; pmL = paramedian lobe; sb = sensilla basiconica; sc = sensory cones; St = stipes; str = stria; to = organ of Tömösváry; numbers refer to antennomere or stria number.

FIGURE 4. Simplomeris montivaga (Faës, 1902), topotype male (ZFMK MYR2626), scanning electron micrographs (SEM). A. Thoracic shield, lateral view. B. Thoracic shield, lateral view, detail. C. Left leg 1 (damaged), posterior view. D. Leg pair 2 with gonopore, posterior view. E. Detail of gonopore. F. Right midbody leg, posterior view. Abbreviations: ch = schisma; Cx = coxa; Cx-p = coxal process; Fe = femur; Go = gonopore; ma = marginal brim; Po = postfemur; Pre = prefemur; sp = spine; str = stria; Ta = tarsus; Ti = tibia.

FIGURE 5. Simplomeris montivaga (Faës, 1902), topotype male (ZFMK MYR2626), scanning electron micrographs. A. Leg pair 17, anterior view. B. leg pair 18, anterior view. C. left telopod (leg pair 19), posterior view. D. Right telopod with syncoxite, anterior view. E. Right telopod, mesal view. Abbreviations: Cx = coxa; IH = inner horn; IL = inner lobe; Syn = syncoxite. Numbers refer to number of podomere or telopoditomere.