Elythesmus enghoffi Hoffman, 1978

Enghoff, Henrik, 2022, A mountain of millipedes X: Species of Pyrgodesmidae and Cryptodesmidae in the Udzungwa Mountains, Tanzania (Diplopoda, Polydesmida), European Journal of Taxonomy 845, pp. 66-100 : 85-92

Elythesmus enghoffi Hoffman, 1978

Figs 12–17

Material examined (124 ♂♂, 1 subad. ♂, 48 ♀♀, 10 subad. ♀, 1 juv. ♀)

Holotype TANZANIA • ♂; East Usambara Mountains , Amani, Monga; 1000 m a.s.l.; 4 Feb. 1972; H. Enghoff, O. Lomholdt and O. Martin leg.; under fallen leaves; ZMUC 0010126 .

Paratypes TANZANIA • 1 ♂, 1 ♀; same collection data as for holotype; NHMD 621777 .

New material

TANZANIA – Udzungwa Mountains • 11 ♂♂; Morogoro Region, Udzungwa Mountains Natl Park , Kidatu ; 07°41′13.5″ S, 36°56′28.6″ E; 650 m a.s.l.; 24 Oct. 2014; J. Malumbres-Olarte leg.; Plot 1, summed catch from five pitfall traps; NHMD 621778 • 6 ♂♂, 1 ♀; same collection data as for preceding; 07°41′14.9″ S, 36°56′24.7″ E; Plot 2, summed catch from five pitfall traps; NHMD 621779 • 23 ♂♂, 2 ♀♀, 3 subad. ♀♀; same collection data as for preceding; 07°41′02.4″ S, 36°55′49.3″ E; 1005 m a.s.l.; 14 Sep. 2014; Plot 3, summed catch from ten pitfall traps; NHMD 621780 • 10 ♂♂, 1 ♀; same collection data as for preceding; 07°41′05.2″ S, 36°55′48.4″ E; 993 m a.s.l.; 15 Oct .. 2014; Plot 4, summed catch from eight pitfall traps; NHMD 621781 • 7 ♂♂, 1 ♀; same collection data as for preceding; 07°40′45.5″ S, 36°55′06.9″ E; 1448 m a.s.l.; 21 Oct. 2014; Plot 5, summed catch from five pitfall traps; NHMD 621786 • 7 ♂♂, 2 ♀♀, 1 subad. ♀; same collection data as for preceding; 07°40′42.1″ S, 36°55′06.8″ E; 1482 m a.s.l.; 21 Oct. 2014; Plot 6, summed catch from four pitfall traps; NHMD 621787 • 13 ♂♂; same collection data as for preceding; 07°41′23.4″ S, 36°56′00.7″ E; 708 m a.s.l.; 24 Oct. 2014; Plot 7, summed catch from six pitfall traps; NHMD 521788 • 10 ♂♂, 1 ♀; same collection data as for preceding; 07°41′12.9″ S, 36°55′39.2″ E; 978 m a.s.l.; 14 Sep. 2014; Plot 8, summed catch from seven pitfall traps; NHMD 621789 • 4 ♂♂; same collection data as for preceding; 07°41′06.2″ S, 36°54′52.4″ E; 1527 m a.s.l.; 14 Sep. 2014; Plot 9, summed catch from four pitfall traps; NHMD 621690 • 1 ♂; Morogoro Region, Udzungwa Mountains Natl Park , above Kidatu; 7°40′34.5′′ S, 36°55′07.0′′ E; 1589 m a.s.l.; 3 Sep. 2016; R. Lowassary, T. Pape and N. Scharff leg.; pitfall trap, Acc. No. 2015-EN-001; NHMD 521691 • 1 ♂; Morogoro Region, Udzungwa Mountains Natl Park , Mito Mitatu ; 07°50′26.1″ S, 36°51′33.0″ E; 1006 m a.s.l.; 26 Oct .. 2014; J. Malumbres-Olarte leg.; Plot 14, pitfall trap; NHMD 621792 • 2 ♂♂; same collection data as for preceding; 07°49′39.8″ S, 36°50′26.0″ E; 1552 m a.s.l.; 27 Oct .. 2014; Plot 15, summed catch from two pitfall traps; NHMD 621793 • 1 ♀; Morogoro Region, Udzungwa Mountains Natl Park , Sanje Chini Camp ; 7°46′24.6″ S, 36°53′47.7″ E; 598 m a.s.l.; 17–19 Jan. 2014; T. Pape and N. Scharff leg.; hand collected; NHMD 621794 • 2 ♂♂; Morogoro Region, Udzungwa Mountains Natl Park , trail to Mizimu Camp ; 250 m a.s.l.; 3 Sep. 2012; T. Pape and N. Scharff leg.; hand collected; NHMD 621795 • 1 ♂, 1 subad. ♂; Udzungwa Mountains, Mwanihana Forest above Sanje; 1700 m a.s.l.; 15 Aug. 1982; M. Stoltze and N. Scharff leg.; NHMD 621796 • 1 ♂; same collection data as for preceding; 1250 m a.s.l.; 25 Jul. 1982; in litter; NHMD 621797 • 1 subad. ♀; same collection data as for preceding; 1000 m a.s.l.; 1 Aug. 1982; in litter; NHMD 621798 • 1 ♂; same collection data as for preceding; 1000 m a.s.l.; 1 Aug. 1982; pitfall trap; NHMD 621810 • 2 ♀♀; Udzungwa Mountains, Morogoro Region, Mwanihana Forest Res.; 1000– 1100 m a.s.l.; 10–24 Sep. 1984; N. Scharff leg.; intermediate rain forest; NHMD 621799 • 1 ♂; same collection data as for preceding; 700 m a.s.l.; 8–16 Sep, 1984; pitfall trap in lowland rain forest; NHMD 621800 • 3 ♂♂; Morogoro Region, Udzungwa Scarp Catchment Forest Reserve, Chita ; 08°30′13.4″ S, 35°55′08.9″ E; 659 m a.s.l.; 31 Oct. 2014; J. Malumbres-Olarte leg.; Plot 16, summed catch from three pitfall traps; NHMD 621801 • 1 ♂; same collection data as for preceding; 08°29′59.1″ S, 35°54′59.5″ E; 908 m a.s.l.; 30 Oct. 2014; J. Malumbres-Olarte leg.; Plot 17, pitfall trap; NHMD 621802 • 2 ♂♂, 1 ♀, 1 subad. ♀; Udzungwa Mountains, Iringa Region, Udzungwa Scarp Forest Res. , above Chita Village; 730– 1050 m a.s.l.; 23 Oct.–14 Nov. 1984; N. Scharff leg.; lowland rain forest; NHMD 621803 , NHMD 621804 , NHMD 621805 • 1 ♂, 1 ♀; same collection data as for preceding; 1400 m a.s.l.; 4–5 Nov. 1984; pitfall traps in intermediate rain forest; NHMD 621806 • 1 ♀; same collection data as for preceding; 1500 m a.s.l.; 13 Nov. 1984; litter, montane rain forest; NHMD 621807 • 1 ♀; same collection data as for preceding; 1600–1650 m.a.s.l.; 8–12 Nov. 1984; montane rain forest; NHMD 621808 • 1 ♂; same collection data as for preceding; 750 m a.s.l., 25–29 Oct. 1984; pitfall traps in lowland rain forest; NHMD 621809 . – Uluguru Mountains • 1 ♂, 2 ♀♀; Lupanga, West ; 1900 m a.s.l.; 1 Jul. 1981; M. Stoltze and N. Scharff leg.; litter; NHMD 621811 • 1 juv. ♀; Lupanga, East ; 1300 m a.s.l.; 10 Jul. 1981; M. Stoltze and N. Scharff leg.; litter; NHMD 621812 • 1 ♂; Morogoro Region, Morogoro District, Kimboza Forest Reserve ; 07°01′ S. 37°48′ E, Jan.– Mar. 1994; Frontier Tanzania leg.; NHMD 621813 • 11 ♂♂, 18 ♀♀; at Bunduki Village ; 07°01′06″ S. 37°39′45″ E; 1569 m a.s.l.; 26 Nov. 2010; V. Grebennikov leg.; ′sifting 27′; NHMD 621814 . – Nguru (Kanga) Mountains • 1 ♀; Morogoro Region, Kanga Mountains, Kanga Forest Reserve ; 400–500 m a.s.l.; 22–25 Nov. 1984, N. Scharff leg.; lowland rain forest; NHMD 621815 . – East Usambara Mountains • 1 ♂; Amani ; 1000 m a.s.l.; 15 Jul. 1980; M. Stoltze and N. Scharff leg.; pitfall trap; NHMD 621816 • 1 subad. ♀; Sangarawe Forest ; 5°6.5′ S, 38°35.7′ E; 990 m a.s.l.; 5–6 Nov. 1995; N. Scharff and C. Griswold leg.; sifting litter; NHMD 621817 . – West Usambara Mountains • 1 subad. ♀; Mazumbai forest Reserve ; 19–29 Sep. 1992; M. Andersen leg.; NHMD 621818 • 3 ♂♂, 1 subad. ♀; Mazumbai Forest ; 4°49′ S, 38°30′ E; 1400–1600 m a.s.l.; 11–19 Nov. 1995; N. Scharff and C. Griswold leg.; NHMD 621819 .

Descriptive notes

The original description ( Hoffman 1978) is exhaustive. The large material studied here, including by scanning electron microscopy (SEM), allows some supplementary notes as well as an account of interspecific variation. See Figs 12–16.

SIZE. Males: Length 6.6–13.2 mm; maximal body width (across metazona) 1.32–2.35 mm; 17 or 18 podous rings + 1 apodous ring + telson. One male possible with only 16 podous rings, see remarks. Females: Length 9.6–16 mm, maximal body width (across metazona) 1.57–2.69 mm; 18 podous rings + 1 apodous ring + telson. The considerable size variation is in part geographical, specimens from the

East and West Usambara Mountains being larger than those from elsewhere. The very extensive material from the Udzungwa Mountains suggests a correlation between altitude and body size, cf. Remarks.

BODY RINGS. Prozonites divided into two zones ( Figs 13C , 14C ). The anterior ca ⅔ is covered in a sculptural pattern consisting of tiny depressions delimited by fine walls, the caudal part of the walls being drawn out, each with ca five micro-ridges, each micro-ridge ending in a fine tooth ( Fig. 14C ). Posterior ca ⅓ unevenly covered by circular ‘buttons’ ( Akkari & Enghoff 2011: fig. 2) resembling the level 2 structural elements described for Cryptocorypha . Metazonites covered by a brown to blackish layer or secretion which can be removed partially using a needle, but which is resistant to ultrasonic cleaning as well as digestion with trypsin or commercial enzymatic detergent. Under the secretion, the metazonital tubercles are covered by rows of hairlike processes which presumably help to keep the secretion layer in place ( Fig. 14A ). The long setae of which each metazonital tubercle carries one are in high magnification seen to be segmented ( Fig. 14D ), their apical part is flattened ( Fig. 14E ). The limbus consists of tongue-shaped, apically sometimes finely serrate lobes, overlaid by a row of spines of ca the same length ( Fig. 14B , see also Akkari & Enghoff 2011: fig. 26).

GONOPODS ( Fig. 16 ). Exactly as described by Hoffman (1978) in all studied males, irrespective of geographical origin, body size or number of podous rings.

Remarks on variation

There is a considerable size variation in the large material of E. enghoffi studied. The width of adult males varies from 1.32 mm in the smallest male (from Udzungwa Mountains) to 2.35 mm in the largest males (from East Usambara Mountains). On the whole, specimens from the Udzungwa Mountains are smaller (male width 1.32–2.04 mm), compared to 2.20–2.35 mm in males from East and West Usambara Mountains and 1.55–2.11 mm in males from Uluguru Mountains ( Table 1 ).

Even more remarkable is the variation in ring number in adult males. Whereas adult females always have 18 podous rings (plus one apodous ring plus telson, adding up to the traditional “20 segments”), adult males may have 18 or 17, possibly even 16 podous rings. In the Udzungwa Mountains there is a geographical pattern: all examined males from the SW part of the Udzungwa (Udzungwa Scarp Catchment Forest Reserve, 659–1400 m a.s.l.) have 18 podous rings. In contrast, among males from the NE part of the mountains (Udzungwa Mountains National Park), males with 18 podous rings were found only at 1482+ m a.s.l.; all males from lower altitudes (down to 250 m a.s.l.) had 17 podous rings, but such males also occurred at altitudes as high as 1527 m a.s.l.

The sample from Kidatu, plot 9 (NHMD 621790) is particularly intriguing: out of four males, one has 18 podous rings, two seem to have 17, and one seems to have only 16 podous rings. However, this apparent case of very local variation in ring number needs verification because the males were unfortunately dissected for gonopod study before the rings were counted, so although deemed improbable, it cannot be completely excluded that one or two rings have become lost.

Figure 17 shows the relationship between podous ring number, body width and altitude in the Udzungwa Mountains.

The much smaller material from the Usambara Mountains only includes males with 18 podous rings, whereas males with 17 and 18 podous rings are present in the also quite small material from the Uluguru Mountains.

Figures

Fig. 12. Elythemus enghoffi Hoffman, 1978, specimens from Uluguru Mts, at Bunduki Village. A. 2 ♂♂ (NHMD 621814), dorsal view. B. ♂ (NHMD 621814), ventral view. C. ♀ (NHMD 621814), lateral view. Scale bars = 1 mm. Photo: S.G. Selvantharan.

Fig. 13. Elythesmus enghoffi Hoffman, 1978, ♂♂, from Kidatu. A, E–G. ♂ (NHMD 621778). B–D. ♂ (NHMD 621779). A. Head and collum, frontal view. B. Gnathochilarium and mandibles, ventral view. C. Ring 9, treated with ultrasound. D. Midbody leg. E. Spinnerets on telson. F. Gonopodal aperture, posterior-ventral view. G. Apodous ring and telson, posterior view. Scale bars: A–D, F–G = 0.1 mm; E = 0.02 mm.

Fig. 14. Elythesmus enghoffi Hoffman, 1978, ♂♂ from Kidatu. A–B. ♂ (NHMD 621779). C–E. ♂ (NHMD 621778). A. Metazonital tubercles after mechanical removal of blackish secretion, showing rows of hair-like processes. B. Limbus.C. Microsculpture of anterior part of prozona. D–E. Metazonital setae showing articulation and flattened tip. Scale bars: A = 0.05 mm; B–C, E = 0.01 mm; D = 0.001 mm.

Fig. 15. Elythesmus enghoffi Hoffman, 1978, ♀ (NHMD 621780) from Kidatu. A. Head and rings 1–5, ventral view. B. Right antenna, ventro-latgeral view. C. Leg pairs 1–2, plus left legs 3–4, and epigynal ridge (arrow), ventral view. D. Leg pairs 1–2 and epigynal ridge, ventro-lateral view. Scale bars: A = 0.2 mm; B–D = 0.1 mm.

Fig. 16. Elythesmus enghoffi Hoffman, 1978, gonopods. A. Topotype, ♂, with 18 podous rings from Amani, East Usambara Mts (NHMD 621816), right gonopod, ventral view. B–E. ♂ (NHMD 621778) with 17 podous rings from Kidatu, left gonopod. B. Ventral view. C. Oblique (slightly apical) mesoventral view. D. Mesal view. E. Lateral view. F. Specimen (NHMD 621787) with 18 podous rings from Kidatu, right gonopod, meso-ventral view. Scale bars: A–E = 0.1 mm; F = 0.05 mm.

Fig. 17. Elythemus enghoffi Hoffman, 1978, variation in body width and number of body rings of males from the Udzungwa Mts. Abbreviations: UDZ SCARP = Udzungwa Scarp Catchment Forest Reserve; UMNP = Udzungwa Mts National Park.