Helicochetus mutaba Kraus, 1960

Enghoff, Henrik, 2018, A mountain of millipedes VI. New records, new species, a new genus and a general discussion of Odontopygidae from the Udzungwa Mts, Tanzania (Diplopoda, Spirostreptida, Odontopygidae), European Journal of Taxonomy 394, pp. 1-29 : 14-17

Helicochetus mutaba Kraus, 1960

Figs 4C–F , 6

Helicochetus mutaba Kraus, 1960: 40 .

Diagnosis

Resembles H. digititarsus Kraus, 1957 , H. gregorii ( Pocock, 1896) and H. monodon Kraus, 1960 in the combination of a broad, shovel-like process (“Tibialdorn”) at the level of the post-torsal narrowing; absence of ventral pads on male tibiae; presence of a basal lamella (“Grundblatt”) on the telomere; tip of telomere not drawn out into long process, with several short to moderately long spine-like outgrowths from the margin. Differs from these species in the shape of the basal lamella: slender, pointed and curved (with a few denticles on the concave margin in the new specimens).

Material studied (total: 2 ♂♂)

TANZANIA: 1 ♂, KMH 2097 , Nyumbenito Mt, forest near Udekwa , Uzungwa Mountains , 2000–3000 m a.s.l., date?, W.A. Rodgers leg. ( VMNH) ; 1 ♂, Iringa Region and District, Mazombo , 20 km NE of Iringa, 1700 m a.s.l., Jan. 1984, Jan Kielland leg. ( ZMUC) .

Description

Male

Based on studied specimens. Details from original description ( Kraus 1960) in parentheses. Both of the new specimens are strongly fragmented and completely faded.

SIZE. Diameter 4.1–4.7 mm (4.0 mm), specimen from Mazombo with ca 64 podous rings, no apodous rings in front of telson, specimen from Nyumbenito Mt probably incomplete (48 podous rings present, no apodous rings in front of telson).

HEAD. Without peculiarities. Five supralabral setae (6).

COLLUM. With two complete furrows on each side, none of them marginal (two distinct furrows, marginal furrow less distinct).

BODY RINGS. Almost perfect cylinders, not vaulted; suture straight; ozopores starting from ring 6, placed ca ⅓ of metazonite length between suture and limbus. Ca 14 metazonital striae, reaching almost up to ozopore (10–11 striae, not at all reaching ozopore level). Surface microsculpture ( Fig. 4D, F ), see Remarks for genus.

ANAL VALVES. Dorsally drawn out into pointed triangular process, ventrally with small protruding knob; mesal margin raised, setiferous tubercles not detectable.

LIMBUS ( Fig. 4C, E ). See Remarks for genus.

MALE LEGS. With postfemoral ventral pads from first post-gonopodal leg-pair 3–5 until ca midbody.

GONOPOD COXA ( Fig. 6A–B ). Lateral margin convex in basal half. Proplica (pp) simple, with straight mesal margin, ending in small proplical lobe (ppl). Metaplica (mp) higher than proplica, apically regularly rounded, subapically with low mesal flange (mmf), mesal margin of flange shallowly concave; distal, basad process (bp) slender.

GONOPOD TELOPODITE ( Fig. 6C–G ). Basomere including torsotope without spines, arculus 90°. A large, shovel-like flange (shl) (“Tibialdorn”) present at level of post-torsal narrowing ( Fig. 6F ). A long, slender, curved spine (ps) at base of solenomere ( Fig. 6E–F ). Solenomere (slm) slender, round in transverse section, as long as telomere (tm), apically wound up in tight, corkscrew-like spiral; spiraled part basally delimited by tight, knob-like turn (kn) (“knotige Drehung”) of solenomere shaft ( Fig. 6G ). Telomere basically a moderately narrow band curved in almost complete circle; with a curved, pointed basal lamella (btl) (“Grundblatt”) pointing into main telomere curvature and with 1–2 small denticles on concave side ( Fig. 6C, E ) (no denticles); tip of telomere on specimen from Mazombo with several long, thin, spinelike processes from margin ( Fig. 6D ), in specimen from Nyumbenito Mt more shallowly serrate.

Female

Unknown.

Distribution

Hitherto known only from the type locality, Mutaba in the vicinity of Kirungu (= Baudoinville ), in the Democratic Republic of the Congo. The two records from Tanzania, Nyumbenito Mt in the Udzungwa Range and Mazombo N of the Udzungwas, thus represent a considerable range extension. See, however, Remarks below.

Remarks

Helicochetus mutaba belongs to a group of very similar nominal species characterized by the following combination of key characters: a shovel-like lamella (“Tibialdorn”) at the level of the post-torsal narrowing; no ventral pads on male tibiae; telomere with a basal lamella (“Grundblatt”); tip of telomere not drawn out into a long process, with several short to moderately long, spine-like outgrowths from the margin. This group consists of H. digititarsus Kraus, 1957 ( Democratic Republic of the Congo), H. gregorii ( Pocock, 1896) ( Kenya) , H. monodon ( Kraus, 1960) ( Zambia) and H. mutaba ( Democratic Republic of the Congo, Tanzania). Table 2 shows the differences between these four species. The outline of the basal lamella of the telomere differs between the species, but it is not unlikely that future collections will bridge the small morphological gaps and that some or all of the four species will have to be synonymized.

Enghoff et al. (2016) recorded H. digititarsus from two Tanzanian localities: 1) Mara Region, Serengeti District, Seronera, Serengeti National Park; 2) Tabora Region, Nzega District, Nzega City. In light of the above discussion, it cannot be excluded that these specimens are conspecific with the one recorded here as H. mutaba .

The vial containing the male from Mazombo also contained a microvial with a mite which was presumably collected in association with the millipede. The mite was infested with numerous thalli of the fungus Rickia sp. (Ascomycota, Laboulbeniales ). Several species of mites are known to be closely associated with millipedes ( Farfan & Klompen 2012), and several species of Rickia Cavara are known to use mites as their host ( Tavares 1985; Seeman & Nahrung 2000), but this seems to be the first known instance of a Rickia –mite–millipede association.

Figures

Fig. 6. Helicochetus mutaba Kraus, 1960, ♂, from Mazombo. Left gonopod. A–B. Coxa. A. Anterior view. B. Mesal view. C–G. Telopodite. C. Anterior-lateral view. D. Detail of C (tip of telomere). E. Mesal-posterior view. F. Anterior-ventral view. G. Detail of F (tip of solenomere). Abbreviations: bp = apical basad process of coxa; btl = basal lamella of telomere; kn = knob-like turn of solenomere; mmf = mesal metaplical flange; mp = metaplica; pp = proplica; ppl = proplical lobe; ps = proximal solenomeral spine; shl = shovel-like flange; slm = solenomere; tm = telomere. Scale bars:A–C, E–F = 0.2 mm; D = 0.05 mm; G = 0.1 mm.

Fig.4.Helicochetusspp.,♂♂,fromUdzungwaMts.A–B.H.dimidiatus(Peters,1855).C–F.H.mutaba Kraus, 1960. A, C, E. Limbus; in E the limbus proper is damaged (remains are seen to the left), so the round-lobed “sublimbus” becomes visible.B, D, F. Surface microsculpture of limbus. Scalebars:A, C, E = 0.01 mm; B, D, F = 0.002 mm.