Pseudopolydesmus, ATTEMS, 1898

Sierwald, Petra, Hennen, Derek A, Zahnle, Xavier J, Ware, Stephanie & Marek, Paul E, 2019, Taxonomic synthesis of the eastern North American millipede genus Pseudopolydesmus (Diplopoda: Polydesmida: Polydesmidae), utilizing high-detail ultraviolet fluorescence imaging, Zoological Journal of the Linnean Society 187 (1), pp. 117-142 : 124-125

GENUS PSEUDOPOLYDESMUS ATTEMS, 1898

( FIGS 1–8 )

Pseudopolydesmus Attems, 1898: 270 , 479. – Attems, 1914: 161. – Brölemann, 1916: 569. – Attems, 1926: 139. – Verhoeff, 1929: 619. – 1931: 305, figs 1–7. – Attems, 1940: 139, figs 201, 202. – Carl, 1941: 291, figs 1, 2. – Chamberlin, 1943c: 17. – Hoffman, 1950: 222, fig. 4. – 1974: 346 (= Dixidesmus ). – [ Withrow, 1988: 64.] – Hoffman, 1999: 442. – Djursvoll et al., 2000: 40.

Dixidesmus Chamberlin, 1943c: 18 . – Chamberlin & Hoffman, 1958: 65.

Type species: Polydesmus canadensis Newport, 1844 . By monotypy.

Diagnosis

Body form: Adult members of the genus Pseudopolydesmus always with 20 body rings including telson (never 19). Lateral corners of collum equal or exceed maximal width of mandibular stipites (narrower in Polydesmus and Brachydesmus , e.g. Djursvoll et al., 2000: 43, fig. 2a), except in Ps. paludicolus . Colour of adults in life ranging from dark brick red ( Fig. 1A ) to light chestnut brown ( Fig. 1B ).

Paranota and tergal sculpture: Paranota mostly level, extending horizontally ( Fig. 2 ). Leading margin flexed anterodorsad, forming a narrow rim. Tergal sculpture pattern (described above; Fig. 4 ) very similar to other members of Polydesmidae , such as Po. inconstans and Po. complanatus , the latter of which is the type species of Polydesmus . Tergal blister pattern in Pseudopolydesmus less distinct than the strongly impressed pattern of Polydesmus . Unlike Po.inconstans and Po. complanatus , tergal setae not usually visible under dissecting microscope except in Ps. paludicolus , but may be visible with UV enhancement.

Gonopod: Gonocoxae large, with two long setae at the ventromedial margin. Posterior margin of gonocoxa divided into ventral and dorsal plate-like lobes that partly surround the telopodite basally. Ventral lobe with one or two gonocoxal plates stacked dorsoventrally. Telopodite falcate. Seminal canal originating medially before looping laterad, debouching at ectal base of pulvillus. Pulvillus entirely covered in bristles ( Fig. 3 ). Seminal chamber large, with an associated duct (duct of the telopodite gland according to Verhoeff, 1931). Acropodite bearing between four and eight dentate to laminar processes along its ectal and medial surfaces; subterminally bearing from about ten to 60 terminal bristles ( Fig. 5A , not socketed like true setae) similar in appearance to a toothbrush; terminally bifurcating into small ectal and medial processes or laminae too small to distinguish under dissecting microscope ( Fig. 5B ).

Somatic male characters: Prefemora of all walking legs beginning with leg pair 3 (body ring 4) strongly swollen dorsad in Pseudopolydesmus males ( Fig. 6A ), much more than in Polydesmus males ( Fig. 6C ). Male sterna with prominent paired lobes or tubercles of various shapes between leg pairs of body rings 5, 6, 7 and 8 ( Fig. 7 ), which carry stiff, peg-like setae, differing from the unmodified setae of the walking legs. Leg pair 3 (body ring 4) with a pair of low lobes in some species; leg pairs 4 and 5 (body ring 5) with prominent lobes; leg pair 6 (anterior legs of body ring 6) with strongly elongated tubercles; leg pair 7 with small tuft of peg-like setae; leg pair 9 (directly posterior to gonopods) with tubercles flattened into longitudinal ridges ( Fig. 8 ); leg pair 10 (anterior leg pair of body ring 8) with prominent ventrad-directed tubercles. This is unlike male Polydesmus , in which tubercles of leg pairs 9 and 10 (the first two leg pairs directly posterior of the gonopods) are absent or very slight. In some species (e.g. in Ps. erasus ) there is an additional pair of lobes at the base of leg pair 11.

The species entries that form the remainder of the taxonomic section are presented in the order they appear in the above key to species. Each species name is given a comprehensive bibliography of published literature, including its junior synonyms and instances in which the name was misapplied. Notes are provided on the disposition of type material for each nominal species. Type abbreviations are as follows: HT, holotype; PT, paratype (s); ST, syntype (s). Names of states in the USA and provinces of Canada are shortened to their standard two-letter postal abbreviations. Specimen numbers of millipedes pictured in this paper that are not part of a type series are notated in bold with an asterisk, e.g. FMNH INS312685 *.

KEY TO SPECIES OF PSEUDOPOLYDESMUS MALES

1 a. Large recurved e2 process or fused recurved e2+e3 process ………………………………………………… 2 b. e2 notrecurved………………………………………………………………………………………………………4

2(1) a. Large recurved e2 not fused with e3 ( Figs 10–12 ) …………………………………………………… Ps. erasus b. Fused e2+e3 process ( Fig. 7 ) …………………………………………………………………………………… 3

3(2) a. m3 process distolaterad of m2; e1 elongate ( Fig. 14 ) ………………………………………… Ps. canadensis b. m3 absent; e1 absent or severely reduced ( Fig. 16 ) ……………………………………………… Ps. collinus

4(1) a. e3 large, spike-shaped; pulvillus large, rounded ( Figs 18–20 ) ………………………………… Ps.pinetorum b. Ectal processes subtriangular or flanged; pulvillus pointed …………………………………………… … 5

5(4) a. Ectal surface strongly flanged, m4 process present ……………………………………………………………6 b. Ectal surface not flanged, with or without strongly flanged medial surface ………………………………7

6(5) a. Ectal flange smooth; large triangular m2 between flange and pulvillus ( Figs 23–25 ) ………… Ps. minor b. Ectal flange bearing e3; no process between flange and pulvillus ( Figs 27–28 ) ………………… Ps. caddo

7(5) a. Strongly flanged medial surface bearing m2 and m3 ( Figs 30–31 ) ………………………… Ps. paludicolus b. Not flanged, with pronounced transverse ridge connecting e2 and m2 ( Figs 8 , 33 ) …………… Ps. serratus

Figures

Figure 1. Two live examples of Pseudopolydesmus. A, Pseudopolydesmus serratus, live adult male, dorsal view (VTEC MPE01173). B, Pseudopolydesmus paludicolus, live adult female, dorsal view (VTEC MPE01167).

Figure 2. Pseudopolydesmus erasus, adult male habitus, lateral view (FMNH INS3120685).

Figure 3. Schematic diagram of right gonopod telopodite of Pseudopolydesmus canadensis, medial view.Ectal processes labelled e1, e2, e3, and e4. Medial processes labelled m1, m2, m3, and m4. After R.L. Hoffman, 1974 (fig. 3).

Figure 4. Schematic diagram of metatergite and ozopore bearing paranota of Pseudopolydesmus, dorsal view. Blisters: Anterior Blister (AB); Median Blister Row (MB1, MB2); Posterior Blister Row (PB1, PB2, PB3); Central Blister (CB); and Lateral Blister (LB). Paranota Corners: Anterior Medial Corner (AMC), at the medial terminus of the Paranota Leading Edge; Anterior Lateral Corner (ALC), at the anteriormost denticle; Posterior Lateral Corner (PLC), usually forms a natural point; Posterior Medial Corner (PMC), at the caudal apex of PB3. Short vertical and oblique lines represent positions of tergal setae and the small circles in each LB represent the ozopores.

Figure 5. Features of the telopodite terminus in Pseudopolydesmus (scanning electron micrograph). A, terminal bristles in Pseudopolydesmus canadensis right gonopod, ectal view (FMNH INS6934). Unlike true setae, these bristles are not socketed at the base; instead, they project continuously from the cuticle of the telopodite. B, terminal bifurcation in Pseudopolydesmus serratus left gonopod, medial view (FMNH INS2819).

Figure 6. The characteristic prefemoral bulge in males of Pseudopolydesmus, and comparison of walking legs in Pseudopolydesmus and Polydesmus (scanning electron micrograph). A, adult male Pseudopolydesmus erasus, left leg 9, with characteristically large prefemoral bulge and thickened femur (FMNH INS3120685). B, adult female Ps. erasus, right leg 12, without prefemoral bulge (FMNH INS3120685). C, adult male Polydesmus inconstans, right leg 14, with slight prefemoral bulge and thickened femur (FMNH INS4265).

Figure 7. Sternal tubercles in male Pseudopolydesmus canadensis, ventral view, body rings 4–8 (FMNH INS6934, ultraviolet enhancement). Visible body rings (BR4–8) and their corresponding leg pairs (LP3–11) and gonopods (GPs) are labelled. Also note the characteristic silhouette of the gonopods of Ps. canadensis, with processes e2 and e3 sharing a narrow stalk.

Figure 8. Body ring 7 in adult male Pseudopolydesmus serratus, posterior view, showing gonopods and sternal tubercles of leg pair 9 (FMNH INS8238, ultraviolet enhancement). Note the prominent transverse ridge between processes e2 and m2 in the gonopods of Ps. serratus.

Figure 10. Gonopod of Pseudopolydesmus erasus (FMNH INS3120685). A, right gonopod, ectal view. B, left gonopod, medial view (image mirrored to match right gonopod).

Figure 11. Gonopod of Pseudopolydesmus erasus (FMNH INS3120685, ultraviolet enhancement). A, right gonopod, ectal view. B, left gonopod, medial view (image mirrored to match right gonopod).

Figure 12. Gonopod of Pseudopolydesmus erasus (FMNH INS3120685, scanning electron micrograph). A, right gonopod, ectal view. B, right gonopod, medial view.

Figure 14. Gonopod of Pseudopolydesmus canadensis (FMNH INS6934, scanning electron micrograph). A, left gonopod, ectal view. B, left gonopod, medial view. Both images mirrored to appear as right gonopod. Cannula removed.

Figure 16. Gonopod of Pseudopolydesmus collinus. Paratype (VMNH PSE00203, ulatraviolet enhancement). A, left gonopod, ectal view. B, left gonopod, medial view. C, left gonopod, posterior oblique view, showing fusion of e2 and e3 processes onto a short, thick stalk. All images mirrored to appear as right gonopod.

Figure 18. Gonopod of Pseudopolydesmus pinetorum. Holotype, Polydesmus natchitoches, from genitalia vial (USNM). A, left gonopod, ectal view. B, left gonopod, medial view. Both images mirrored to appear as right gonopod.

Figure 19. Gonopod of Pseudopolydesmus pinetorum. Holotype, Polydesmus natchitoches, from genitalia vial (USNM, ultraviolet enhancement). A, left gonopod, ectal view. B, left gonopod, medial view. Both images mirrored to appear as right gonopod.

Figure 20. Gonopod of Pseudopolydesmus pinetorum (FMNH INS1445, scanning electron micrograph). A, left gonopod, ectal view. B, left gonopod, medial view. Both images mirrored to appear as right gonopod.

Figure 23. Gonopodof Pseudopolydesmus minor. Holotype, Polydesmus euthetus (USNM). A, right gonopod, ectal view. B, right gonopod, medial view.

Figure 24. Gonopodof Pseudopolydesmus minor. Holotype, Polydesmus euthetus (USNM, ultraviolet enhancement). A, right gonopod, ectal view. B, right gonopod, medial view.

Figure 25. Gonopod of Pseudopolydesmus minor (FMNH INS7107, scanning electron micrograph). A, right gonopod, ectal view. B, left gonopod, medial view (image mirrored to match right gonopod).

Figure 27. Gonopod of Pseudopolydesmus caddo. Holotype (USNM). A, right gonopod, ectal view. B, right gonopod, medial view.

Figure 28. Gonopod of Pseudopolydesmus caddo. Holotype (USNM, ultraviolet enhancement). A, right gonopod, ectal view. B, right gonopod, medial view.

Figure 30. Gonopod of Pseudopolydesmus paludicolus (VTEC MPE01170, ultraviolet enhancement). A, left gonopod, ectal view. B, left gonopod, medial view. C, left gonopod, posterior oblique view, showing process e2 projecting laterally. All images mirrored to appear as right gonopod.

Figure 31. Left gonopod of Pseudopolydesmus paludicolus, ectal view (VTEC MPE01169, scanning electron micrograph). Image mirrored to appear as right gonopod.

Figure 33. Gonopod of Pseudopolydesmus serratus (FMNH INS2819, scanning electron micrograph). A, left gonopod, ectal view. B, left gonopod, medial view. Both images mirrored to appear as right gonopod.